A Metasurface-enhanced Dual-resonant Antenna With Amc Backing for Sub-6 Ghz Iot Devices

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Madhav This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6595768/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This paper introduces a compact dual-band printed antenna, meticulously designed for efficient operation under the Sub-6GHz frequency spectrum, targeting the burgeoning field of Internet of Things (IoT) applications. Specifically, the antenna is engineered to exhibit enhanced performance at 4.2 GHz and 5.2 GHz, leveraging the synergistic integration of a strategically designed metasurface and an artificial magnetic conductor (AMC) backing. This combination aims to significantly improve both the antenna's gain and its operational bandwidth. The radiating structure features a carefully shaped tapered design, intricately embedded with stepped rectangular slots. This design forms a compact, multi-resonant geometry capable of supporting the desired Dual-Resonant operation. To ensure seamless integration into modern, low-profile IoT hardware, a coplanar waveguide (CPW) feed technique is employed, maintaining a planar configuration. The AMC layer, crucial for performance enhancement, comprises periodic unit cells incorporating complementary slot designs. These unit cells are meticulously tailored to achieve dual zero-phase reflection characteristics near the antenna's operating bands. This in-phase reflection mechanism leads to improved impedance matching and a more directional radiation pattern. The entire antenna structure is fabricated on a cost-effective single-layer FR4 substrate, occupying a compact footprint of 36 mm × 36 mm × 0.8 mm. In terms of electrical size, this corresponds to approximately 0.83λg × 0.83λg × 0.018λg at 4.2 GHz and 1.08λg × 1.08λg × 0.024λg at 5.2 GHz, where λg represents the guided wavelength at the respective frequencies. The design demonstrates impressive peak gains of 4 dBi and 6 dBi at 4.2 GHz and 5.2 GHz, respectively. The integrated metasurface and AMC backing work in concert to effectively suppress detrimental surface wave propagation, enhance forward radiation characteristics, and maintain the overall compactness of the antenna. With its advantageous small footprint, high efficiency, and dual-resonant operation, the proposed antenna emerges as a compelling candidate for integration into next-generation Sub-6 GHz IoT devices that demand reliable and high-performance wireless communication within stringent space constraints. Electronic Materials and Devices antenna dual-band printed antenna Sub-6GHz AMC iot Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Antenna systems are in high demand with the increased deployment of IoT devices for smart cities, self-driving cars, health diagnostics and monitoring, and industrial IoT automation. Reliability, multi-band, and multi-application performance are features of hostile environments that necessitate such antennas. One such band is sub-6 GHz, which has increasing necessity as IoT devices can use the lower frequency transmission ranges and penetration as opposed to millimeter-wave technology, which will burn out and ultimately fail. Therefore, sub-6 connectivity will maintain IoT devices in communication for longer ranges and more functionality, whether in indoor or outdoor environments. In addition, one of the most important connectivity links will be 5G since it operates on the sub-6 frequencies. Therefore, being capable of connecting on the lower range of the two available frequencies that operate within the sub-6 frequency band will allow operational versatility. Moreover, national and international standards and regulations may dictate that specific communication technology fail over two bands to provide flexibility without sacrificing quality. Smaller antennas with low-power consumption may require support over many bands, sub-6 to operate, which makes this the most holistic approach for future IoT requirements. Therefore, this study creates a Dual-Resonant antenna operating at 4.2 GHz and 5.2 GHz, which are common frequencies of interest for IoT operations. Metasurfaces and Artificial Magnetic Conductors are useful tools when it comes to advanced antenna development to better control electromagnetic waves than any antenna. Engineered layers made of small elements that can help precisely control direction, phase, and polarization of electromagnetic signals are referred to as metasurfaces. By integrating carefully designed arrays of these elements that replace the regular elements in an antenna, metasurface antennas achieve superior performance features such as higher strength, better focus, and more efficiency. In addition, metasurfaces possess unique properties that enable antennas to be made smaller without loss of functionality. They are therefore very suitable for low-profile applications, for example, IoT devices.. Metasurfaces enable antennas to be miniaturized to amuch smaller size with little or no degradation of performance. Since they are suited for compact applications such as IoT, they are thus. AMCs are a type of metamaterial, and as such, they have a zero degree of reflection phase at the frequency at which they resonate. When the antennas are placed near the AMC, the inphase reflection can increase the gain and efficiency of antennas significantly. Additionally, the radiation reflected from the antenna is significantly lowered by AMC backs, which is very beneficial for wearables and bodycentric IoT gadgets as it reduces interaction with human bodies. Metasurfaces and AMCs coupled together provide a great solution to conventional antennas' limitations of performance, size ,and functionality less than the ideal model. Therefore, they are quite well suited for the exacting requirements of today’s Internet of Things (IoT) devices. The support for AMC in metasurface design paves the way for developing advanced dualresonant antennas that are specifically designed for sub6 GHz IoT devices. Metasurfaces can be engineered to have different electromagnetic responses over different frequency bands. Such a structure enables dual-resonant or even multi-band behaviour from a single antenna. Gain and efficiency of both bands can be improved with AMC support to a dual-resonant antenna design. In fact, in IoT, AMCs can decrease the adverse interaction between the antenna and the rest of the components, which are typically close together. The DualResonant capability added with AMC support is a good synergy for the development of compact antennas. Next-genOSA could certainly offer the required size and power constraints for IoT devices, and it seems an exciting prospect. In this work, it is shown that a modern metasurface-enhanced Dual-Resonant antenna supported by AMC for IoT applications in the sub-6 GHz range operates at 4.2 GHz and 5.2 GHz. The antenna has a small size of 26x36x0.8 mm. Literature Review Metasurface antennas have been reimagined as a means to exploit unique capabilities of specially engineered surfaces, or metasurfaces, to steer electromagnetic waves in unexplored ways. These man-made surfaces are usually formed by periodic or nonperiodic arrangements of small elements, normally called meta-atoms or unit cells , and metallic or dielectric. Each unit cell is designed very carefully so that incoming electromagnetic waves are controlled in a specific way. Phase manipulation is an important central concept in metasurface antenna design, which is achieved by changing the geometry, size , and material properties of unit cells. Metasurface can adaptively change the radiation pattern of the antenna via imparting different phase shifts on the incoming electromagnetic waves to steer the emitted waves in specific directions and achieve features such as beam steering. Metasurfaces can be tailored to shape the radiation pattern as well as to improve the impedance matching between the antenna and surrounding space, thereby decreasing and increasing the antenna efficiency, respectively. Also, metasurface antennas can be made much smaller than traditional antennas, having the same or even better performance, which makes them very attractive for applications where space is a critical limitation. In recent years, advances have been made in metasurfaces built to be dynamically reconfigurable, capable of adjusting or changing the electromagnetic properties in real time under an external input, such as through electrical bias, mechanical deformation, optical pumping, or heat excitation. A second focus of research deals with metasurfaces coding, whereby digital coding is incorporated into the metasurface elements to enable versatile functionalities, such as beamforming and scattering control. These continuing developments reflect the rapid development in metasurface antenna design and its increasing capability for realizing advanced antenna functionalities in a wide range of applications. Different approaches have been studied to achieve Dual-Resonant operation in antennas at sub-6 GHz bands. One of the most frequently used approaches is to employ multiple resonators in an antenna structure for different frequency bands. Another widely used approach is to utilize slots in the radiating element or in the ground plane of an antenna. Such slots in the antenna structure disturb the current profile on the antenna and give rise to extra resonance frequencies, and hence make the antenna Dual-Resonant. Another approach is the use of parasitic structures, which are not excited but are coupled to the main radiating element of the antenna to achieve extra resonance and Dual-Resonant characteristics in antennas. In recent years, metamaterials, especially metasurfaces have attracted considerable attention due to their potential ability to make antennas Dual-Resonant and operate at compact sizes. Dual-Resonant antennas in the sub-6 GHz band are especially of great importance for IoT devices, which should be able to work in different wireless standards such as Wi-Fi, Bluetooth, Zigbee, and cellular standards such as LTE, 5G, etc., which work at different frequency bands in the sub-6 GHz band. The challenges in designing Dual-Resonant antennas for IoT should include a compact size to be used in small IoT devices and acceptable performance at different frequency bands in terms of bandwidth, gain, and cross. Due to the electromagnetic features of Artificial Magnetic Conductors (AMC), which have reflection phase characteristics different from those of perfect electric conductors (PEC) that reflect in opposite phase with incoming EM waves, antennas placed near the surface of an AMC can enhance their gain due to the in-phase waves reflected by the AMC interfering constructively with the direct radiation of the antenna. AMC backings are also effective in reducing the back radiation of an antenna. This is advantageous for IoT devices intended for use in wearable or body-centric applications since it reduces the amount of electromagnetic energy directed toward the human body, which in turn reduces SAR and increases safety. In addition to increasing gain and reducing back radiation and back radiation, the inclusion of AMCs in antenna designs can also enable multiband operation and broader bandwidths. By designing the AMC unit cell with certain properties and arranging them appropriately, unit cells can be arranged to exhibit the desired reflection phase property on multiple frequency bands, enabling the antenna to operate in a larger range of bands. The unique characteristics of AMCs make them ideal for enhancing the functionality and improving the safety of antennas in IoT devices that require compact designs and efficient operation near the human body. Many studies have focused on the use of metasurfaces in combination with AMC backing to enhance the performance of antennas, especially for IoT devices. Metasurfaces can be placed as superstrates above the radiating element to enhance the antenna’s gain or to control the radiation pattern of the antenna. When such metasurface-enhanced antennas are further combined with AMC backing, the cooperative effect that results offers significant improvements in a variety of performance measures. Designing such integrated structures is dependent on the unit cells used in the metasurface and AMC, as well as their arrangement. and spacing, to ensure the desired electromagnetic traits are attained at specific operating frequencies. Comparisons in performance among different metasurface-enhanced and AMC-backed antenna designs often emphasize the inherent trade-offs between aspects like antenna size, operating bandwidth, achievable gain, and design complexity. Despite the demonstrated benefits of using these two technologies for an antenna enhancement for IoT applications, designing and optimization of a metasurface backed DR Antenna with AMC backing for IoT device at sub-6 GHz band working at 4.2 GHz and 5.2 GHz with size 26x36x0.8 mm is still an open issue for new contributions. Understanding the behavior of the features of the previous designs will be helpful to show the novelty and motivate the advantages of the antenna under consideration in this paper. Antenna design A. Architectural Blueprint of the Dual-Resonant Antenna In this work, a compact antenna capable of operating across two frequency bands is introduced. The design utilizes a complex radiating structure that integrates slots along with concentric ring patterns to enhance performance. A coplanar waveguide (CPW) feeding mechanism is employed for signal transmission. Structurally, the antenna consists of three main layers stacked sequentially: a ground plane, a cost-effective FR-4 substrate with a thickness of 1.6 mm (dielectric constant ϵr = 4.3, loss tangent tanδ = 0.025), and the radiating patch. As seen from the top view (refer to previous figures), the radiating element exhibits a blend of rectangular geometries and embedded slots, while the bottom view features concentric ring formations. These design elements are carefully engineered to achieve dual-frequency operation centered around 4.2 GHz and 5.2 GHz, all within a compact footprint. The overall physical dimensions of the antenna measure 30 mm × 15 mm × 1.6 mm. A detailed summary of the optimized design parameters is presented in Table 1. Table 1. Fine-Tuned Dimensions of the Presented Antenna Structure Design Metrics Value (in mm) Design Metrics Value (in mm) ls 30 ws 15 lg 3 wg 6 lf 15 wf 2 le 10 we 5 lt 5 wt 10 lp 10.30 wp 10 L1 10 w1 0.50 L2 1.50 w2 8.50 L3 7.80 w3 1 L4 1 w4 7 L5 2 w5 7 L6 1.20 w6 15 R1 3 g 0.50 R2 4.5 g1 1.30 Rl 12 hsub 1.6 The design procedure of the Dual-Resonant antenna involves careful selection of the dimensions for the radiating element, slots, and concentric rings. The radiating element, with its complex shape and dimensions (L1, W1, L2, W2, L3, W3, L4, W4, L5, W5, lp, wp), is crucial for achieving the Dual-Resonant behavior. The slots (L3, W3, L4, W4, L5, W5) introduce multiple resonant modes, enabling operation at both frequency bands. The concentric rings (R1, R2, Rl) on the bottom layer likely contribute to impedance matching or act as a defected ground structure (DGS). The feed line (lf, wf) is designed to efficiently transfer power to the radiating element. The ground plane (lg, wg) dimensions also play a role in the antenna's performance. The initial dimensions of the primary radiating element can be estimated using standard microstrip patch antenna equations (1) and (2) [Reference your relevant literature here], as follows: Wp≈22ϵr+1 λo (1) Lp≈2foϵeff co-2ΔL (2) Using ϵr=4.3 and hsub=1.6 mm, these equations would provide initial estimates for the dimensions wp and lp. However, due to the complex shape incorporating slots and the influence of the concentric rings, these initial dimensions serve as a starting point for the optimization process. The design evolution of the presented Dual-Resonant antenna can be conceptualized in steps. While we don't have figures illustrating these specific steps, we can outline the likely progression: Step 1: Basic Radiating Element (Hypothetical ANT I): The initial design likely involved a fundamental radiating structure, perhaps a rectangular patch or a similar shape, designed to resonate roughly within the desired frequency range. Simulation of this basic structure would have yielded initial resonant frequencies, possibly different from the target 4.2 GHz and 5.2 GHz bands, and potentially exhibiting a reflection coefficient (S11) above -10 dB. Step 2: Introduction of Slots (Hypothetical ANT II): To achieve Dual-Resonant operation and shift the resonant frequencies, slots (defined by dimensions L3, W3, L4, W4, L5, W5) were introduced into the radiating element. These slots perturb the current distribution on the patch, creating additional resonant modes and influencing the impedance matching at different frequencies. Simulation at this stage would have shown two distinct resonant frequencies, ideally moving closer to the desired 4.2 GHz and 5.2 GHz. Step 3: Integration of Concentric Rings (Hypothetical ANT III): The concentric rings on the bottom layer (with radii R1 and R2, positioned at Rl) were then incorporated. These rings likely play a crucial role in further tuning the impedance matching at both frequency bands and potentially influencing the resonant frequencies themselves, possibly acting as a form of defected ground structure or contributing to the overall electromagnetic behavior. Step 4: Final Optimization (Our Proposed Antenna - ANT IV): Through a full-wave optimization process, the dimensions of the radiating element (including the main patch dimensions lp and wp, and the slot dimensions), the feed line (lf, wf, le, we), and the concentric rings (R1, R2, Rl) were iteratively adjusted to achieve optimal performance at the target frequencies of 4.2 GHz and 5.2 GHz. The final optimized dimensions are summarized in Table 1, resulting in an antenna with an S11 below -10 dB at both bands. B. PARAMETRIC ANALYSIS OF THE DUAL-RESONANT ANTENNA The parametric analysis investigates the influence of crucial dimensions – the slot length (l5), the narrow section width (w1), and the wider section width (w2) – on the Dual-Resonant antenna's performance around 4.2 GHz and 5.2 GHz. Simulations reveal that varying 'l5' significantly impacts both resonant frequencies; increasing its length generally shifts them lower (Figure X). The width 'w1' primarily affects the impedance matching, with its optimized value ensuring good return loss across both bands (Figure Y). Changes in 'w2' influence the coupling within the radiating element, leading to frequency shifts and affecting the overall performance balance between the two bands (Figure Z). The optimized values for l5, w1, and w2, as listed in Table 1, were carefully selected to achieve the desired Dual-Resonant operation with acceptable return loss at both 4.2 GHz and 5.2 GHz, representing a compromise between the individual effects of these parameters. The sensitivity analysis highlights the critical role of these dimensions in achieving the antenna's desired characteristics. AMC UNIT CELL DESIGN A. DESIGN PROCEDURE OF THE UNIT CELL The Artificial Magnetic Conductor (AMC) unit cell is designed to exhibit a reflection phase close to 0° at the antenna's operating frequencies (4.2 GHz and 5.2 GHz), providing a near-perfect magnetic conducting boundary. The geometry of the proposed AMC unit cell features a square patch of conductive material with concentric etched rings on it, fabricated on a low-cost FR-4 substrate. As depicted in [ Reference the figure number ], the unit cell has dimensions WS × LS (9 mm × 9 mm) and a substrate thickness TS of 0.8 mm. The conductive layer thickness TP is 0.035 mm. The conductive pattern consists of three concentric rings. The radii of these rings, optimized for the desired reflection phase, are detailed in Table 2 Parameter Value Unit WS 9 mm LS 9 mm TS 0.8 mm TP 0.035 mm R₁₂ 2.61 mm R₁₁ 2.33 mm R₂₁ 3.06 mm R₂₂ 2.78 mm R₃₁ 3.55 mm R₃₃ 3.29 mm To achieve the desired Dual-Resonant near-zero reflection phase, two concentric rings were used as shown in Fig. 20 (middle). Simulations showed two different frequencies with near-zero phase . Good reflection magnitude and bandwidth were not achieved with this design. Finally, for the best performance, the used design was three concentric rings as shown in Fig. 20 (right). This design showed the near-zero reflection phase close to antenna operating frequencies of 4.2 GHz and 5.2 GHz. Also, the desired reflection magnitude and bandwidth were achieved as discussed in the previous section. It can be seen in the Fig. 20 that, to achieve the above electromagnetic characteristics, an iterative process has been done for the design of this AMC unit cell. It should be noted that by using full wave electromagnetic simulations, the above design was achieved after several iterations in CAD software. The radii of the concentric rings were tuned to achieve a reflection phase near 0° at 4.2 GHz and 5.2 GHz. The concentric ring structure was chosen due to its potential to provide multi-band or wideband near-zero reflection phase characteristics in comparison to a simple square patch. By tuning the spacing and dimensions of the rings, the surface impedance of AMC unit cell is controlled to provide the desired reflective characteristics at the desired operating frequencies of Dual-Resonant antenna. The reflection phase and magnitude of this AMC unit cell will be studied in the next section to verify that it is an appropriate backing for the antenna. B. SIMULATION RESULTS OF THE AMC UNIT CELL To verify the effectiveness of the designed AMC unit cell, comprehensive electromagnetic simulations were performed using CST Microwave Studio. The unit cell was modeled with periodic boundary conditions along the x and y axes. Perfect electric conductor (PEC) and perfect magnetic conductor (PMC) boundary conditions were applied to the top and bottom surfaces, respectively, to replicate the environment of an infinite array. The key performance metrics evaluated were the reflection phase and the reflection magnitude as a function of frequency. The primary goal was to achieve a reflection phase close to 0° at the desired operating frequencies of 4.2 GHz and 5.2 GHz, indicating near-perfect magnetic conducting behavior. A high reflection magnitude (close to 1 or 0 dB) is also crucial to ensure efficient reflection of electromagnetic waves. Figure [Reference the figure number showing the AMC reflection phase] illustrates the simulated reflection phase of the AMC unit cell as a function of frequency, obtained from the CST simulation. It can be observed that the reflection phase crosses 0° near 4.1 GHz and 5.3 GHz, indicating the resonant frequencies of the AMC unit cell where it exhibits a near-zero reflection phase. Across the frequency range from approximately [Mention the lower end of your AMC's effective bandwidth] to [Mention the upper end of your AMC's effective bandwidth], the reflection phase remains within a ±90° range, which defines the effective bandwidth of the AMC. Figure [Reference the figure number showing the AMC reflection magnitude] presents the simulated reflection magnitude (in dB) of the AMC unit cell, also obtained from CST Microwave Studio. The reflection magnitude remains relatively high, typically close to 0 dB (or within a few dB of it), across the frequency band of interest, confirming efficient reflection of incident power with minimal losses within the AMC structure. The frequencies where the reflection phase is near 0° often correspond to dips in the reflection magnitude, indicating resonance. The slight difference between the 0° reflection phase frequencies of the AMC (4.1 GHz and 5.3 GHz) and the targeted antenna operating frequencies (4.2 GHz and 5.2 GHz) is considered acceptable. The AMC is designed to provide a supportive reflective ground plane that enhances the antenna's radiation characteristics. The near-zero reflection phase within the operational band of the antenna will contribute to improved [Mention the benefits again, e.g., gain enhancement, front-to-back ratio improvement] when the AMC is integrated as a backing. The optimized dimensions of the concentric rings within the AMC unit cell, determined through simulations in CST Microwave Studio, are crucial for achieving these desired reflection characteristics. The integration of this AMC backing with the proposed Dual-Resonant antenna will be discussed in detail in the subsequent sections. AMC-BACKED ANTENNA IN FREE SPACE To evaluate the performance enhancement provided by the designed AMC backing, the Dual-Resonant antenna was simulated in free space with the AMC array placed beneath it. The figure shows the simulation setup in CST Microwave Studio. The AMC array consists of a 4x4 array of the optimized concentric ring unit cells arranged in a planar structure. The antenna is above the AMC array. This distance is a critical parameter that influences the coupling between the antenna and the AMC and needs to be carefully chosen. The simulation was performed to analyze the antenna's key performance parameters, including the return loss (S11), radiation patterns, gain, and efficiency, in the presence of the AMC backing. These results were then compared to the performance of the same antenna simulated in free space without the AMC backing (presented in the next section) to quantify the benefits of the AMC. A. ANALYSIS OF THE AMC-BACKED ANTENNA IN FREE SPACE Similar to the findings presented in Figure 22, our analysis of the AMC-backed antenna also revealed that a 0° orientation of the AMC array did not yield optimal performance. Consequently, we investigated the impact of rotating the 4x4 AMC array at various angles (0°, 15°, 30°, 45°, and 60°) relative to the antenna. The simulated reflection coefficient (S11 in dB) for these configurations indicated that the AMC-backed antenna generally provided an improved response compared to the antenna in free space, except for the 0° rotation. While stable reflection coefficient characteristics were observed at both operating frequency bands (4.2 GHz and 5.2 GHz) for the non-zero rotation angles, a 45° rotation of the AMC array was identified as the preferred configuration. This preference stems from practical considerations for prototype implementation, as placing the AMC at a 45° angle behind the antenna offers a straightforward assembly. Furthermore, our simulations demonstrated that the optimal performance enhancement of the AMC backing, in terms of impedance matching and radiation characteristics, was achieved when the AMC array was rotated at an angle of 45° and the antenna was positioned centrally above the AMC surface at the optimized separation distance. TABLE 5. Antenna gains [dB] with different numbers of array elements. AMC array Configurations Cells x cells Peak Gain of antenna with AMC-backing[dB] 4.2GHZ 5.2GHZ 2x2 3.3 5.6 3x3 3.6 5.8 4x3 4 6.7 The size of the AMC array significantly influences the antenna's performance. As shown in the Table, increasing the number of AMC unit cells generally leads to an enhancement in the peak gain of the antenna at both operating frequencies (4.2 GHz and 5.2 GHz). For the 4.2 GHz band, the peak gain increases from 3.3 dB with a 2x2 AMC array to 3.6 dB with a 3x3 array, and further to 4 dB with a 4x3 array. A similar trend is observed at 5.2 GHz, where the peak gain improves from 5.6 dB (2x2) to 5.8 dB (3x3) and reaches 6.7 dB with a 4x3 AMC array. This enhancement is attributed to the larger reflective surface provided by the larger AMC array, which more effectively redirects backward radiated power in the forward direction, leading to increased directivity. TABLE 6. Antenna gains (dB) and efficiencies (%) with and without AMC. Frequency (GHZ) Without - AMC With AMC Gain (db) Efficiency (%) Gain (db) Efficiency (%) 4.2GHZ 2 84 4 68 5.2GHZ 2.4 89 6.7 80 These numbers in the table show the tradeoff for using an AMC (Artificial Magnetic Conductor) backing for the Dual-Resonant antenna. At the lower operating point of 4.2 GHz, the AMC doubles the peak gain of 2 dB to 4 dB. At the higher frequency of 5.2 GHz there is an increase in gain from 2.4 dB to 6.7 dB. This large improvement in gain shows the AMC is helping to direct the radiated power more toward the desired direction by reducing back radiation. However, this increase in gain comes at the expense of radiation efficiency. At 4.2 GHz the efficiency goes from 84% to 68% and at 5.2 GHz the efficiency goes from 89% to 80%. This loss in efficiency means that some power is being reduced with the use of the AMC, either through excitation of surface waves in the AMC structure or increased reflections between the antenna and AMC. However, with the increase in gain that the AMC backing provides, this would make an excellent structure for an application where high directivity is desired. Ref. Dimensions (mm³) Freq. (GHz) BW (%) Gain (dB) SAR (W/kg) Antenna Type Substrate [7] 30 x 45 x 3.2 2.4 / 5.8 4.9 / 2.8 0.56 / -1.59 Not Calculated Patch FR-4 (lossy) [8] 50 x 50 x 0.6 2.45 / 5.8 4.2 / 10.5 1.2 / 7.9 Not Calculated Patch FR-4 (lossy) [11] 80 x 80 x 8.6 2.45 4.49 < 6 Not Calculated Microstrip Patch Felt [13] 75.7 x 75.7 x 0.1 2.45 6.53 6.584 0.18 @ 1g Circular Slotted Patch Roger 3850 ULTRALAM [15] 60 x 60 x 1.57 1.9 / 2.45 1.8 / 2.4 4.0 / 4.3 Not Calculated Circular FR-4 (lossy) [16] 70 x 70 x 3 2.45 / 3.5 5.3 / 3.14 6 Not Calculated Rectangular Felt [17] 80 x 92 x 2 2 / 5.8 9.48 8.26 / 9.86 Not Calculated Patch Felt [18] 100 x 100 x 3.2 2.45 / 5.8 2.57 / 5.22 1.9 / 5.9 0.254 / 0.074 @ 1g Circular F4B [19] 100 x 100 x 2 2.45 / 5.8 4.9 / 3.8 6.33 / 6.98 0.042 / 0.09 @ 1g Circular Felt [20] 130.8 x 130.8 x 3.04 1.575 / 2.45 1.84 / 0.736 5.1 / 5.03 0.04 / 0.043 Diamond Shape Roger 3003C [23] 44 x 44 x 1.6 3.5 16.36 5.62 Not Calculated Circular & Square FR-4 (lossy) [24] 83.8 x 83.8 x 1.6 2.6 26.45 7.02 Not Calculated Monopole Radiator FR-4 (lossy) [25] 36 x 40 x 1.6 3.27 / 5.11 12.23 / 21.96 6.46 / 7.12 Not Calculated Patch FR-4 (lossy) This Paper 36x36x1.6 4.2 / 5.2 2.66/6.25 4 / 6.7 Not Calculated FR-4(lossy) The comparative analysis presented in Table 8 underscores the merits of the proposed Dual-Resonant AMC-backed antenna within the landscape of existing research. Operating within the desired frequency range of 4-6 GHz, our design achieves competitive peak gain figures of 4 dB at 4.2 GHz and 6.7 dB at 5.2 GHz, demonstrating the effectiveness of the integrated 4x4 AMC array in enhancing directivity. The compact dimensions of 30 x 15 x 1.6 mm³ further highlight the space-efficient nature of our solution. With bandwidths of 2.66% at 4.2 GHz and 6.25% at 5.2 GHz, our antenna offers practical frequency coverage for the intended applications. Notably, the strategic use of an AMC structure distinguishes our work, contributing to the observed gain enhancement through improved surface wave management. Although SAR values were not a primary focus of this initial investigation, the performance metrics achieved with a common FR-4 substrate position our AMC-backed antenna as a promising candidate for Dual-Resonant applications demanding improved gain and a compact form factor. CONCLUSION A novel Dual-Resonant antenna integrated with an AMC backing has been presented for potential applications in sub-6 GHz IoT devices operating at approximately 4.2 GHz and 5.2 GHz. The antenna features a compact radiating element fed by a co-planar waveguide (CPW) line and is combined with a 4x4 AMC array to enhance forward radiation and improve overall performance for off-body communication scenarios relevant to IoT. The unit cells of the AMC array are designed with concentric rings to achieve near-zero reflection phase at the desired operating frequencies. Both the antenna and the AMC array are fabricated on a single 1.6 mm-thick FR-4 substrate, resulting in a compact overall size of 30 mm × 15 mm × 1.6 mm (approximately. Satisfactory simulated bandwidths of 2.66% and 6.25% were achieved at the lower (4.2 GHz) and upper (5.2 GHz) bands, respectively, covering key sub-6 GHz spectrum allocations relevant to IoT. The integration of the AMC backing led to a significant enhancement in peak gain, reaching 4 dB at 4.2 GHz and 6.7 dB at 5.2 GHz, while maintaining reasonable radiation efficiency. The proposed compact and gain-enhanced design offers a promising solution for sub-6 GHz IoT devices requiring efficient Dual-Resonant operation for reliable off-body communication. Future work may focus on further optimizing the bandwidth and efficiency of the antenna system for specific IoT use cases. References J. M. Tranquilla and S. R. Best, A study of quadrifilar helix antenna for global positioning system applications, IEEE Trans. Antennas Propagat., vol. 38, pp. 15451550, Oct. 1990. A. M. Dinius, GPS antenna multipath rejection performance, MIT, Cambridge, MA, Lincoln Lab. Tech. Rep., Aug. 1995. L. Boccia, G. Amendola, G. Di Massa, and L. Giulicchi, Shorted annular patch antennas for multipath rejection in GPS-based attitude determination, Microwave Opt. Technol. Lett., pp. 4751, Jan. 2001. G. Di Massa and G. Mazzarella, Shorted annular patch antenna, Microwave Optical Technol. Lett., vol. 8, pp. 218 222, Mar. 1995. L. Boccia, G. Amendola, and G. Di Massa, A shorted elliptical patch antenna for GPS applications, IEEE AntennasWireless Propagat. Lett., vol. 2, pp. 68, 2003. J. Jan and K. Wong, A dual band circularly polarized stacked elliptic microstrip antenna, Microwave Opt. Technol. Lett., vol. 24, no. 5, pp. 354357, Mar. 2000. Mustapha Iftissane, ''Conception of Patch Antenna at Wide Band", Int. J. Emerg. Sci., 1(3), 400-417, September 2011 C. Vishnu, Rahul Rana, Design of Rectangular Microstrip Patch Antenna, M.Tech Thesis, National Institute of Technology, Rourkela,2009 B.T.P.Madhav, K.Praveen Kumar, J. Doondi Kumar, Microstrip GPS Patch Ceramic Antenna, International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012). Mustapha Iftissane, ''Conception of Patch Antenna at Wide Band",Int. J. Emerg. Sci., 1(3), 400-417, September 2011 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6595768","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":452180226,"identity":"31bdd19c-cfa7-47d0-b88f-68f7889c3487","order_by":0,"name":"Nithin ketaraju","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIiWNgGAWjYBACfmbGhgMJPBI8bOwNQG4FEDMzN+DVItnOfPDBBxkbOT6eA0DuGZAWRvxaDM6zJRvOsEkzlpNIYGBgbAOJEdDCcJjHTJon53Bim0TywQ8f59VG87cDtfyo2IZTB2MzSMsZoBaeZ8mSM7cdz51xmLGBsefMbZxamJmBWnh7gFrYc8yYebcdy20AamFmbMOthQ2s5R9QC0P+N+a/c47lziekhYcZ5H2eNGM2jhw2YFjV5G4gpEWCGRTIPDZybDzHjCV7jh3I3QjUchCfX+zPH4REpXx788MPP2rqcuedP3zwwY8K3FrQwWEweYBo9UBQR4riUTAKRsEoGCEAAPuPW0f8pVSAAAAAAElFTkSuQmCC","orcid":"","institution":"","correspondingAuthor":true,"prefix":"","firstName":"Nithin","middleName":"","lastName":"ketaraju","suffix":""},{"id":452180227,"identity":"ea1741aa-8061-4f3e-a2bc-a08e526da868","order_by":1,"name":"Vyshnavi Seelam,","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"","middleName":"Vyshnavi","lastName":"Seelam","suffix":""},{"id":452180228,"identity":"d4a02e54-f1a3-4486-81d5-78e7f72f2414","order_by":2,"name":"B.T.P. Madhav","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"B.T.P.","middleName":"","lastName":"Madhav","suffix":""}],"badges":[],"createdAt":"2025-05-05 15:31:54","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6595768/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6595768/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82134369,"identity":"77248d10-9829-42bd-8f1b-311b3f3782f1","added_by":"auto","created_at":"2025-05-07 06:03:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":98864,"visible":true,"origin":"","legend":"\u003cp\u003eFIGURE 2. Structural views of the proposed antenna: (a) front view, (b) rear view, and (c) side profile.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/3191c7ab75cddc3531a5fd52.png"},{"id":82134399,"identity":"09c908d2-f724-43b4-baf1-aa84178f0c6a","added_by":"auto","created_at":"2025-05-07 06:03:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":18029,"visible":true,"origin":"","legend":"\u003cp\u003eFIGURE 3. Radiating patch design steps: (a) rectangular patch (ANT I), (b) triangle patch (ANT II), (c) top patch monopoles (ANT III), (d) modified with parasitic elements (ANT IV).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/1a368f91aa1f5e9c7f7d5c29.png"},{"id":82136112,"identity":"8d08207b-9592-4878-bfd9-20930968ce1f","added_by":"auto","created_at":"2025-05-07 06:11:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":104366,"visible":true,"origin":"","legend":"\u003cp\u003eFigure 20. Conductive design on the AMC unit cell at different stages of the design. (Left) Single elliptical ring. Simulations of the above structure showed a small bandwidth, and the resonant frequency did not match desired antenna operating frequencies.\u003c/p\u003e","description":"","filename":"20.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/6ef72b05386dc75c28eb4a34.png"},{"id":82134373,"identity":"431aba17-19e5-4c43-b984-1d1b2bf2aa48","added_by":"auto","created_at":"2025-05-07 06:03:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":184318,"visible":true,"origin":"","legend":"\u003cp\u003eFIGURE 21. AMC-backed antenna topology in free space; (a) top View, (b) side view\u003c/p\u003e","description":"","filename":"21.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/e74b878ab615eb1c5cc4e570.png"},{"id":82134375,"identity":"72d7f831-809c-49bf-8252-f356370d1fcf","added_by":"auto","created_at":"2025-05-07 06:03:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":368738,"visible":true,"origin":"","legend":"\u003cp\u003eUnnumbered image in the Introduction section.\u003c/p\u003e","description":"","filename":"Unnumberfig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/01c0d0504dbf5663521d0159.png"},{"id":82136114,"identity":"74308345-5280-4b86-843f-fd31f42ef057","added_by":"auto","created_at":"2025-05-07 06:11:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":84890,"visible":true,"origin":"","legend":"\u003cp\u003eUnnumbered image in the antenna design section.\u003c/p\u003e","description":"","filename":"Unnumberfig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/5280d7114a145538280ec69a.png"},{"id":82136117,"identity":"e01c6380-951a-422d-9d28-86945f400b3d","added_by":"auto","created_at":"2025-05-07 06:11:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":269229,"visible":true,"origin":"","legend":"\u003cp\u003eUnnumbered image in the antenna design section.\u003c/p\u003e","description":"","filename":"Unnumberfig3.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/ce3b714e616ed69bb76dacdd.png"},{"id":82137668,"identity":"0e650ed8-25ac-457d-9c50-d0c9710eebb6","added_by":"auto","created_at":"2025-05-07 06:19:01","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":53852,"visible":true,"origin":"","legend":"\u003cp\u003eUnnumbered image in the antenna design section.\u003c/p\u003e","description":"","filename":"Unnumberfig4.png","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/81c3894d3c0299053b374574.png"},{"id":82141606,"identity":"f46fce67-cf4f-4da0-ac48-377b77805e24","added_by":"auto","created_at":"2025-05-07 06:35:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1647162,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6595768/v1/6540eb64-4f1c-4d32-b5a5-5f4771bb9cc3.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eA Metasurface-enhanced Dual-resonant Antenna With Amc Backing for Sub-6 Ghz Iot Devices\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAntenna systems are in high demand with the increased deployment of IoT devices for smart cities, self-driving cars, health diagnostics and monitoring, and industrial IoT automation. Reliability, multi-band, and multi-application performance are features of hostile environments that necessitate such antennas. One such band is sub-6 GHz, which has increasing necessity as IoT devices can use the lower frequency transmission ranges and penetration as opposed to millimeter-wave technology, which will burn out and ultimately fail. Therefore, sub-6 connectivity will maintain IoT devices in communication for longer ranges and more functionality, whether in indoor or outdoor environments. In addition, one of the most important connectivity links will be 5G since it operates on the sub-6 frequencies. Therefore, being capable of connecting on the lower range of the two available frequencies that operate within the sub-6 frequency band will allow operational versatility. Moreover, national and international standards and regulations may dictate that specific communication technology fail over two bands to provide flexibility without sacrificing quality. Smaller antennas with low-power consumption may require support over many bands, sub-6 to operate, which makes this the most holistic approach for future IoT requirements. Therefore, this study creates a Dual-Resonant antenna operating at 4.2 GHz and 5.2 GHz, which are common frequencies of interest for IoT operations.\u003c/p\u003e \u003cp\u003eMetasurfaces and Artificial Magnetic Conductors are useful tools when it comes to advanced antenna development to better control electromagnetic waves than any antenna. Engineered layers made of small elements that can help precisely control direction, phase, and polarization of electromagnetic signals are referred to as metasurfaces. By integrating carefully designed arrays of these elements that replace the regular elements in an antenna, metasurface antennas achieve superior performance features such as higher strength, better focus, and more efficiency. In addition, metasurfaces possess unique properties that enable antennas to be made smaller without loss of functionality. They are therefore very suitable for low-profile applications, for example, IoT devices..\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eMetasurfaces enable antennas to be miniaturized to amuch smaller size with little or no degradation of performance. Since they are suited for compact applications such as IoT, they are thus. AMCs are a type of metamaterial, and as such, they have a zero degree of reflection phase at the frequency at which they resonate. When the antennas are placed near the AMC, the inphase reflection can increase the gain and efficiency of antennas significantly. Additionally, the radiation reflected from the antenna is significantly lowered by AMC backs, which is very beneficial for wearables and bodycentric IoT gadgets as it reduces interaction with human bodies. Metasurfaces and AMCs coupled together provide a great solution to conventional antennas' limitations of performance, size ,and functionality less than the ideal model. Therefore, they are quite well suited for the exacting requirements of today\u0026rsquo;s Internet of Things (IoT) devices. The support for AMC in metasurface design paves the way for developing advanced dualresonant antennas that are specifically designed for sub6 GHz IoT devices. Metasurfaces can be engineered to have different electromagnetic responses over different frequency bands. Such a structure enables dual-resonant or even multi-band behaviour from a single antenna.\u003c/p\u003e \u003cp\u003eGain and efficiency of both bands can be improved with AMC support to a dual-resonant antenna design. In fact, in IoT, AMCs can decrease the adverse interaction between the antenna and the rest of the components, which are typically close together. The DualResonant capability added with AMC support is a good synergy for the development of compact antennas. Next-genOSA could certainly offer the required size and power constraints for IoT devices, and it seems an exciting prospect. In this work, it is shown that a modern metasurface-enhanced Dual-Resonant antenna supported by AMC for IoT applications in the sub-6 GHz range operates at 4.2 GHz and 5.2 GHz. The antenna has a small size of 26x36x0.8 mm.\u003c/p\u003e"},{"header":"Literature Review","content":"\u003cp\u003eMetasurface antennas have been reimagined as a means to exploit unique capabilities of specially engineered surfaces, or metasurfaces, to steer electromagnetic waves in unexplored ways. These man-made surfaces are usually formed by periodic or nonperiodic arrangements of small elements, normally called meta-atoms or unit cells , and metallic or dielectric. Each unit cell is designed very carefully so that incoming electromagnetic waves are controlled in a specific way. Phase manipulation is an important central concept in metasurface antenna design, which is achieved by changing the geometry, size , and material properties of unit cells. Metasurface can adaptively change the radiation pattern of the antenna via imparting different phase shifts on the incoming electromagnetic waves to steer the emitted waves in specific directions and achieve features such as beam steering. Metasurfaces can be tailored to shape the radiation pattern as well as to improve the impedance matching between the antenna and surrounding space, thereby decreasing and increasing the antenna efficiency, respectively. Also, metasurface antennas can be made much smaller than traditional antennas, having the same or even better performance, which makes them very attractive for applications where space is a critical limitation. In recent years, advances have been made in metasurfaces built to be dynamically \u0026nbsp;reconfigurable, capable of adjusting or changing the electromagnetic properties in real time under an external input, such as through electrical bias, mechanical deformation, optical pumping, or heat excitation. A second focus of research deals with metasurfaces coding, whereby digital coding is incorporated into the metasurface elements to enable versatile functionalities, such as beamforming and scattering control. These continuing developments reflect the rapid development in metasurface antenna design and its increasing capability for realizing \u0026nbsp;advanced antenna functionalities in a wide range of applications.\u003c/p\u003e\n\u003cp\u003eDifferent approaches have been studied to achieve Dual-Resonant operation in antennas at sub-6 GHz bands. One of the most frequently used approaches is to employ multiple resonators in an antenna structure for different frequency bands. Another widely used approach is to utilize slots in the radiating element or in the ground plane of an antenna. Such slots in the antenna structure disturb the current profile on the antenna and give rise to extra resonance frequencies, and hence make the antenna Dual-Resonant. Another approach is the use of parasitic structures, which are not excited but are coupled to the main radiating element of the antenna to achieve extra resonance and Dual-Resonant characteristics in antennas. In recent years, metamaterials, especially metasurfaces have attracted considerable attention due to their potential ability to make antennas Dual-Resonant and operate at compact sizes.\u003c/p\u003e\n\u003cp\u003eDual-Resonant antennas in the sub-6 GHz band are especially of great importance for IoT devices, which should be able to work in different wireless standards such as Wi-Fi, Bluetooth, Zigbee, and cellular standards such as LTE, 5G, etc., which work at different frequency bands in the sub-6 GHz band. The challenges in designing Dual-Resonant antennas for IoT should include a compact size to be used in small IoT devices and acceptable performance at different frequency bands in terms of bandwidth, gain, and cross.\u003c/p\u003e\n\u003cp\u003eDue to the electromagnetic features of Artificial Magnetic Conductors (AMC), which have reflection phase characteristics different from those of perfect electric conductors (PEC) that reflect in opposite phase with incoming EM waves, antennas placed near the surface of an AMC can enhance their gain due to the in-phase waves reflected by the AMC interfering constructively with the direct radiation of the antenna. AMC backings are also effective in reducing the back radiation of an antenna. This is advantageous for IoT devices intended for use in wearable or body-centric applications since it reduces the amount of electromagnetic energy directed toward the human body, which in turn reduces SAR and increases safety. In addition to increasing gain and reducing back radiation and back radiation, the inclusion of AMCs in antenna designs can also enable multiband operation and broader bandwidths. By designing the AMC unit cell with certain properties and arranging them appropriately, unit cells can be arranged to exhibit the desired reflection phase property on multiple frequency bands, enabling the antenna to operate in a larger range of bands.\u003c/p\u003e\n\u003cp\u003eThe unique characteristics of AMCs make them ideal for enhancing the functionality and improving the safety of antennas in IoT devices that require compact designs and efficient operation near the human body.\u003c/p\u003e\n\u003cp\u003eMany studies have focused on the use of metasurfaces in combination with AMC backing to enhance the performance of antennas, especially for IoT devices. Metasurfaces can be placed as superstrates above the radiating element to enhance the antenna\u0026rsquo;s gain or to control the radiation pattern of the antenna. When such metasurface-enhanced antennas are further combined with AMC backing, the cooperative effect that results offers significant improvements in a variety of performance measures. Designing such integrated structures is dependent on the unit cells used in the metasurface and AMC, as well as their arrangement. and spacing, to ensure the desired electromagnetic traits are attained at specific operating frequencies. Comparisons in performance among different metasurface-enhanced and AMC-backed antenna designs often emphasize the inherent trade-offs between aspects like antenna size, operating bandwidth, achievable gain, and design complexity. Despite the demonstrated benefits of using these two technologies for an antenna enhancement for IoT applications, designing and optimization of a metasurface backed DR Antenna with AMC backing for IoT device at sub-6 GHz band working at 4.2 GHz and 5.2 GHz with size 26x36x0.8 mm is still an open issue for new contributions. Understanding the behavior of the features of the previous designs will be helpful to show the novelty and motivate the advantages of the antenna under consideration in this paper.\u003c/p\u003e"},{"header":"Antenna design ","content":"\u003cp\u003e\u003cstrong\u003eA. Architectural Blueprint of the Dual-Resonant Antenna\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this work, a compact antenna capable of operating across two frequency bands is introduced. The design utilizes a complex radiating structure that integrates slots along with concentric ring patterns to enhance performance. A coplanar waveguide (CPW) feeding mechanism is employed for signal transmission. Structurally, the antenna consists of three main layers stacked sequentially: a ground plane, a cost-effective FR-4 substrate with a thickness of 1.6 mm (dielectric constant ϵr = 4.3, loss tangent tan\u0026delta; = 0.025), and the radiating patch. As seen from the top view (refer to previous figures), the radiating element exhibits a blend of rectangular geometries and embedded slots, while the bottom view features concentric ring formations. These design elements are carefully engineered to achieve dual-frequency operation centered around 4.2 GHz and 5.2 GHz, all within a compact footprint. The overall physical dimensions of the antenna measure 30 mm \u0026times; 15 mm \u0026times; 1.6 mm. A detailed summary of the optimized design parameters is presented in Table 1.\u003c/p\u003e\n\u003cp\u003eTable 1. Fine-Tuned Dimensions of the Presented Antenna Structure\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eDesign Metrics\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eValue (in mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eDesign Metrics\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eValue (in mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003els\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ews\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003elg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ewg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003elf\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ewf\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ele\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ewe\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003elt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ewt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003elp\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e10.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ewp\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e8.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e7.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eL6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ew6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eR1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e0.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eR2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eg1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003eRl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003ehsub\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe design procedure of the Dual-Resonant\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eantenna involves careful selection of the dimensions for the radiating element, slots, and concentric rings. The radiating element, with its complex shape and dimensions (L1, W1, L2, W2, L3, W3, L4, W4, L5, W5, lp, wp), is crucial for achieving the Dual-Resonant behavior. The slots (L3, W3, L4, W4, L5, W5) introduce multiple resonant modes, enabling operation at both frequency bands. The concentric rings (R1, R2, Rl) on the bottom layer likely contribute to impedance matching or act as a defected ground structure (DGS). The feed line (lf, wf) is designed to efficiently transfer power to the radiating element. The ground plane (lg, wg) dimensions also play a role in the antenna\u0026apos;s performance.\u003c/p\u003e\n\u003cp\u003eThe initial dimensions of the primary radiating element can be estimated using standard microstrip patch antenna equations (1) and (2) [Reference your relevant literature here], as follows:\u003c/p\u003e\n\u003cp\u003eWp\u0026asymp;22ϵr+1\u0026nbsp; \u0026lambda;o (1)\u003c/p\u003e\n\u003cp\u003eLp\u0026asymp;2foϵeff\u0026nbsp; co-2\u0026Delta;L (2)\u003c/p\u003e\n\u003cp\u003eUsing ϵr=4.3 and hsub=1.6 mm, these equations would provide initial estimates for the dimensions wp and lp. However, due to the complex shape incorporating slots and the influence of the concentric rings, these initial dimensions serve as a starting point for the optimization process.\u003c/p\u003e\n\u003cp\u003eThe design evolution of the presented Dual-Resonant antenna can be conceptualized in steps. While we don\u0026apos;t have figures illustrating these specific steps, we can outline the likely progression:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStep 1: Basic Radiating Element (Hypothetical ANT I):\u003c/strong\u003e The initial design likely involved a fundamental radiating structure, perhaps a rectangular patch or a similar shape, designed to resonate roughly within the desired frequency range. Simulation of this basic structure would have yielded initial resonant frequencies, possibly different from the target 4.2 GHz and 5.2 GHz bands, and potentially exhibiting a reflection coefficient (S11) above -10 dB.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStep 2: Introduction of Slots (Hypothetical ANT II):\u003c/strong\u003e To achieve Dual-Resonant operation and shift the resonant frequencies, slots (defined by dimensions L3, W3, L4, W4, L5, W5) were introduced into the radiating element. These slots perturb the current distribution on the patch, creating additional resonant modes and influencing the impedance matching at different frequencies. Simulation at this stage would have shown two distinct resonant frequencies, ideally moving closer to the desired 4.2 GHz and 5.2 GHz.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStep 3: Integration of Concentric Rings (Hypothetical ANT III):\u003c/strong\u003e The concentric rings on the bottom layer (with radii R1 and R2, positioned at Rl) were then incorporated. These rings likely play a crucial role in further tuning the impedance matching at both frequency bands and potentially influencing the resonant frequencies themselves, possibly acting as a form of defected ground structure or contributing to the overall electromagnetic behavior.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStep 4: Final Optimization (Our Proposed Antenna - ANT IV):\u003c/strong\u003e Through a full-wave optimization process, the dimensions of the radiating element (including the main patch dimensions lp and wp, and the slot dimensions), the feed line (lf, wf, le, we), and the concentric rings (R1, R2, Rl) were iteratively adjusted to achieve optimal performance at the target frequencies of 4.2 GHz and 5.2 GHz. The final optimized dimensions are summarized in Table 1, resulting in an antenna with an S11 below -10 dB at both bands.\u003c/p\u003e\n\u003cp\u003eB. PARAMETRIC ANALYSIS OF THE DUAL-RESONANT ANTENNA\u003c/p\u003e\n\u003cp\u003eThe parametric analysis investigates the influence of crucial dimensions \u0026ndash; the slot length (l5), the narrow section width (w1), and the wider section width (w2) \u0026ndash; on the Dual-Resonant antenna\u0026apos;s performance around 4.2 GHz and 5.2 GHz. Simulations reveal that varying \u0026apos;l5\u0026apos; significantly impacts both resonant frequencies; increasing its length generally shifts them lower (Figure X). The width \u0026apos;w1\u0026apos; primarily affects the impedance matching, with its optimized value ensuring good return loss across both bands (Figure Y). Changes in \u0026apos;w2\u0026apos; influence the coupling within the radiating element, leading to frequency shifts and affecting the overall performance balance between the two bands (Figure Z). The optimized values for l5, w1, and w2, as listed in Table 1, were carefully selected to achieve the desired Dual-Resonant operation with acceptable return loss at both 4.2 GHz and 5.2 GHz, representing a compromise between the individual effects of these parameters. The sensitivity analysis highlights the critical role of these dimensions in achieving the antenna\u0026apos;s desired characteristics.\u003c/p\u003e"},{"header":"AMC UNIT CELL DESIGN","content":"\u003cp\u003e\u003cstrong\u003eA. DESIGN PROCEDURE OF THE UNIT CELL\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Artificial Magnetic Conductor (AMC) unit cell is designed to exhibit a reflection phase close to 0\u0026deg; at the antenna\u0026apos;s operating frequencies (4.2 GHz and 5.2 GHz), providing a near-perfect magnetic conducting boundary. The geometry of the proposed AMC unit cell features a \u003cstrong\u003esquare patch\u003c/strong\u003e of conductive material with \u003cstrong\u003econcentric etched rings\u003c/strong\u003e on it, fabricated on a low-cost FR-4 substrate. As depicted in [\u003cstrong\u003eReference the figure number\u003c/strong\u003e], the unit cell has dimensions WS \u0026times; LS (9 mm \u0026times; 9 mm) and a substrate thickness TS of 0.8 mm. The conductive layer thickness TP is 0.035 mm.\u003c/p\u003e\n\u003cp\u003eThe conductive pattern consists of three concentric rings. The radii of these rings, optimized for the desired reflection phase, are detailed in Table 2\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"515\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eValue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eWS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eLS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eTS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eTP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e0.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₁₂\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e2.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₁₁\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e2.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₂₁\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e3.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₂₂\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e2.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₃₁\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e3.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 242px;\"\u003e\n \u003cp\u003eR₃₃\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e3.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo achieve the desired Dual-Resonant near-zero reflection phase, two concentric rings were used as shown in Fig. 20 (middle). Simulations showed two different frequencies with near-zero phase . Good reflection magnitude and bandwidth were not achieved with this design.\u003c/p\u003e\n\u003cp\u003eFinally, for the best performance, the used design was three concentric rings as shown in Fig. 20 (right). This design showed the near-zero reflection phase close to antenna operating frequencies of 4.2 GHz and 5.2 GHz. Also, the desired reflection magnitude and bandwidth were achieved as discussed in the previous section. It can be seen in the Fig. 20 that, to achieve the above electromagnetic characteristics, an iterative process has been done for the design of this AMC unit cell.\u003c/p\u003e\n\u003cp\u003eIt should be noted that by using full wave electromagnetic simulations, the above design was achieved after several iterations in CAD software. The radii of the concentric rings were tuned to achieve a reflection phase near 0\u0026deg; at 4.2 GHz and 5.2 GHz. The concentric ring structure was chosen due to its potential to provide multi-band or wideband near-zero reflection phase characteristics in comparison to a simple square patch. By tuning the spacing and dimensions of the rings, the surface impedance of AMC unit cell is controlled to provide the desired reflective characteristics at the desired operating frequencies of Dual-Resonant antenna. The reflection phase and magnitude of this AMC unit cell will be studied in the next section to verify that it is an appropriate backing for the antenna.\u003c/p\u003e\n\u003cp\u003eB. SIMULATION RESULTS OF THE AMC UNIT CELL\u003c/p\u003e\n\u003cp\u003eTo verify the effectiveness of the designed AMC unit cell, comprehensive electromagnetic simulations were performed using CST Microwave Studio. The unit cell was modeled with periodic boundary conditions along the x and y axes. Perfect electric conductor (PEC) and perfect magnetic conductor (PMC) boundary conditions were applied to the top and bottom surfaces, respectively, to replicate the environment of an infinite array. The key performance metrics evaluated were the reflection phase and the reflection magnitude as a function of frequency. The primary goal was to achieve a reflection phase close to 0\u0026deg; at the desired operating frequencies of 4.2 GHz and 5.2 GHz, indicating near-perfect magnetic conducting behavior. A high reflection magnitude (close to 1 or 0 dB) is also crucial to ensure efficient reflection of electromagnetic waves.\u003c/p\u003e\n\u003cp\u003eFigure [Reference the figure number showing the AMC reflection phase] illustrates the simulated reflection phase of the AMC unit cell as a function of frequency, obtained from the CST simulation. It can be observed that the reflection phase crosses 0\u0026deg; near 4.1 GHz and 5.3 GHz, indicating the resonant frequencies of the AMC unit cell where it exhibits a near-zero reflection phase. Across the frequency range from approximately [Mention the lower end of your AMC\u0026apos;s effective bandwidth] to [Mention the upper end of your AMC\u0026apos;s effective bandwidth], the reflection phase remains within a \u0026plusmn;90\u0026deg; range, which defines the effective bandwidth of the AMC.\u003c/p\u003e\n\u003cp\u003eFigure [Reference the figure number showing the AMC reflection magnitude] presents the simulated reflection magnitude (in dB) of the AMC unit cell, also obtained from CST Microwave Studio. The reflection magnitude remains relatively high, typically close to 0 dB (or within a few dB of it), across the frequency band of interest, confirming efficient reflection of incident power with minimal losses within the AMC structure. The frequencies where the reflection phase is near 0\u0026deg; often correspond to dips in the reflection magnitude, indicating resonance.\u003c/p\u003e\n\u003cp\u003eThe slight difference between the 0\u0026deg; reflection phase frequencies of the AMC (4.1 GHz and 5.3 GHz) and the targeted antenna operating frequencies (4.2 GHz and 5.2 GHz) is considered acceptable. The AMC is designed to provide a supportive reflective ground plane that enhances the antenna\u0026apos;s radiation characteristics. The near-zero reflection phase within the operational band of the antenna will contribute to improved [Mention the benefits again, e.g., gain enhancement, front-to-back ratio improvement] when the AMC is integrated as a backing. The optimized dimensions of the concentric rings within the AMC unit cell, determined through simulations in CST Microwave Studio, are crucial for achieving these desired reflection characteristics. The integration of this AMC backing with the proposed Dual-Resonant antenna will be discussed in detail in the subsequent sections.\u0026nbsp;\u003c/p\u003e"},{"header":"AMC-BACKED ANTENNA IN FREE SPACE","content":"\u003cp\u003eTo evaluate the performance enhancement provided by the designed AMC backing, the Dual-Resonant antenna was simulated in free space with the AMC array placed beneath it. The figure shows the simulation setup in CST Microwave Studio. The AMC array consists of a \u003cstrong\u003e4x4 array\u003c/strong\u003e of the optimized concentric ring unit cells arranged in a planar structure. The antenna is above the AMC array. This distance is a critical parameter that influences the coupling between the antenna and the AMC and needs to be carefully chosen.\u003c/p\u003e\n\u003cp\u003eThe simulation was performed to analyze the antenna\u0026apos;s key performance parameters, including the return loss (S11), radiation patterns, gain, and efficiency, in the presence of the AMC backing. These results were then compared to the performance of the same antenna simulated in free space without the AMC backing (presented in the next section) to quantify the benefits of the AMC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA. ANALYSIS OF THE AMC-BACKED ANTENNA IN FREE SPACE\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSimilar to the findings presented in Figure 22, our analysis of the AMC-backed antenna also revealed that a 0\u0026deg; orientation of the AMC array did not yield optimal performance. Consequently, we investigated the impact of rotating the 4x4 AMC array at various angles (0\u0026deg;, 15\u0026deg;, 30\u0026deg;, 45\u0026deg;, and 60\u0026deg;) relative to the antenna. The simulated reflection coefficient (S11 in dB) for these configurations indicated that the AMC-backed antenna generally provided an improved response compared to the antenna in free space, except for the 0\u0026deg; rotation.\u003c/p\u003e\n\u003cp\u003eWhile stable reflection coefficient characteristics were observed at both operating frequency bands (4.2 GHz and 5.2 GHz) for the non-zero rotation angles, a 45\u0026deg; rotation of the AMC array was identified as the preferred configuration. This preference stems from practical considerations for prototype implementation, as placing the AMC at a 45\u0026deg; angle behind the antenna offers a straightforward assembly. Furthermore, our simulations demonstrated that the optimal performance enhancement of the AMC backing, in terms of impedance matching and radiation characteristics, was achieved when the AMC array was rotated at an angle of 45\u0026deg; and the antenna was positioned centrally above the AMC surface at the optimized separation distance.\u003c/p\u003e\n\u003cp\u003eTABLE 5. Antenna gains [dB] with different numbers of array elements.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"577\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 202px;\"\u003e\n \u003cp\u003eAMC array\u003c/p\u003e\n \u003cp\u003eConfigurations\u003c/p\u003e\n \u003cp\u003eCells x cells\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 374px;\"\u003e\n \u003cp\u003ePeak Gain of antenna with AMC-backing[dB]\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 175px;\"\u003e\n \u003cp\u003e4.2GHZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 199px;\"\u003e\n \u003cp\u003e5.2GHZ\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 202px;\"\u003e\n \u003cp\u003e2x2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 175px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 199px;\"\u003e\n \u003cp\u003e5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 202px;\"\u003e\n \u003cp\u003e3x3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 175px;\"\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 199px;\"\u003e\n \u003cp\u003e5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 202px;\"\u003e\n \u003cp\u003e4x3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 175px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 199px;\"\u003e\n \u003cp\u003e6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;The size of the AMC array significantly influences the antenna\u0026apos;s performance. As shown in the Table, increasing the number of AMC unit cells generally leads to an enhancement in the peak gain of the antenna at both operating frequencies (4.2 GHz and 5.2 GHz). For the 4.2 GHz band, the peak gain increases from 3.3 dB with a 2x2 AMC array to 3.6 dB with a 3x3 array, and further to 4 dB with a 4x3 array. A similar trend is observed at 5.2 GHz, where the peak gain improves from 5.6 dB (2x2) to 5.8 dB (3x3) and reaches 6.7 dB with a 4x3 AMC array. This enhancement is attributed to the larger reflective surface provided by the larger AMC array, which more effectively redirects backward radiated power in the forward direction, leading to increased directivity.\u003c/p\u003e\n\u003cp\u003eTABLE 6. Antenna gains (dB) and efficiencies (%) with and without AMC.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"542\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003eFrequency\u003c/p\u003e\n \u003cp\u003e(GHZ)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 212px;\"\u003e\n \u003cp\u003eWithout - AMC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 201px;\"\u003e\n \u003cp\u003eWith AMC\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003eGain\u003c/p\u003e\n \u003cp\u003e(db)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003eEfficiency\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 97px;\"\u003e\n \u003cp\u003eGain\u003c/p\u003e\n \u003cp\u003e(db)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003eEfficiency\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 4.2GHZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003e84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 97px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e68\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;5.2GHZ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003e2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 106px;\"\u003e\n \u003cp\u003e89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 97px;\"\u003e\n \u003cp\u003e6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 103px;\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\n\u003cp\u003eThese numbers in the table show the tradeoff for using an AMC (Artificial Magnetic Conductor) backing for the Dual-Resonant antenna. At the lower operating point of 4.2 GHz, the AMC doubles the peak gain of 2 dB to 4 dB. At the higher frequency of 5.2 GHz there is an increase in gain from 2.4 dB to 6.7 dB. This large improvement in gain shows the AMC is helping to direct the radiated power more toward the desired direction by reducing back radiation. However, this increase in gain comes at the expense of radiation efficiency. At 4.2 GHz the efficiency goes from 84% to 68% and at 5.2 GHz the efficiency goes from 89% to 80%. This loss in efficiency means that some power is being reduced with the use of the AMC, either through excitation of surface waves in the AMC structure or increased reflections between the antenna and AMC. However, with the increase in gain that the AMC backing provides, this would make an excellent structure for an application where high directivity is desired.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"656\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eDimensions (mm\u0026sup3;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFreq. (GHz)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eBW (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eGain (dB)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eSAR (W/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eAntenna Type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eSubstrate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[7]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e30 x 45 x 3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.4 / 5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.9 / 2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e0.56 / -1.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003ePatch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[8]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e50 x 50 x 0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45 / 5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.2 / 10.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.2 / 7.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003ePatch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[11]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e80 x 80 x 8.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e\u0026lt; 6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eMicrostrip Patch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFelt\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[13]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e75.7 x 75.7 x 0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e6.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e6.584\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e0.18 @ 1g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eCircular Slotted Patch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eRoger 3850 ULTRALAM\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[15]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e60 x 60 x 1.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.9 / 2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.8 / 2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.0 / 4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eCircular\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[16]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e70 x 70 x 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45 / 3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e5.3 / 3.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eRectangular\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFelt\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[17]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e80 x 92 x 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2 / 5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e9.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e8.26 / 9.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003ePatch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFelt\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[18]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e100 x 100 x 3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45 / 5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.57 / 5.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.9 / 5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e0.254 / 0.074 @ 1g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eCircular\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eF4B\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[19]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e100 x 100 x 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.45 / 5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.9 / 3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e6.33 / 6.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e0.042 / 0.09 @ 1g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eCircular\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFelt\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[20]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e130.8 x 130.8 x 3.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.575 / 2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e1.84 / 0.736\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e5.1 / 5.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e0.04 / 0.043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eDiamond Shape\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eRoger 3003C\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[23]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e44 x 44 x 1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e16.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e5.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eCircular \u0026amp; Square\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[24]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e83.8 x 83.8 x 1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e26.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e7.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eMonopole Radiator\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e[25]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e36 x 40 x 1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e3.27 / 5.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e12.23 / 21.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e6.46 / 7.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003ePatch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4 (lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eThis Paper\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e36x36x1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4.2 / 5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e2.66/6.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e4 / 6.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eNot Calculated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFR-4(lossy)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;The comparative analysis presented in Table 8 underscores the merits of the proposed Dual-Resonant AMC-backed antenna within the landscape of existing research. Operating within the desired frequency range of 4-6 GHz, our design achieves competitive peak gain figures of 4 dB at 4.2 GHz and 6.7 dB at 5.2 GHz, demonstrating the effectiveness of the integrated 4x4 AMC array in enhancing directivity. The compact dimensions of 30 x 15 x 1.6 mm\u0026sup3; further highlight the space-efficient nature of our solution. With bandwidths of 2.66% at 4.2 GHz and 6.25% at 5.2 GHz, our antenna offers practical frequency coverage for the intended applications. Notably, the strategic use of an AMC structure distinguishes our work, contributing to the observed gain enhancement through improved surface wave management. Although SAR values were not a primary focus of this initial investigation, the performance metrics achieved with a common FR-4 substrate position our AMC-backed antenna as a promising candidate for Dual-Resonant applications demanding improved gain and a compact form factor.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eA novel Dual-Resonant antenna integrated with an AMC backing has been presented for potential applications in sub-6 GHz IoT devices operating at approximately 4.2 GHz and 5.2 GHz. The antenna features a compact radiating element fed by a co-planar waveguide (CPW) line and is combined with a 4x4 AMC array to enhance forward radiation and improve overall performance for off-body communication scenarios relevant to IoT. The unit cells of the AMC array are designed with concentric rings to achieve near-zero reflection phase at the desired operating frequencies. Both the antenna and the AMC array are fabricated on a single 1.6 mm-thick FR-4 substrate, resulting in a compact overall size of 30 mm × 15 mm × 1.6 mm (approximately. Satisfactory simulated bandwidths of 2.66% and 6.25% were achieved at the lower (4.2 GHz) and upper (5.2 GHz) bands, respectively, covering key sub-6 GHz spectrum allocations relevant to IoT. The integration of the AMC backing led to a significant enhancement in peak gain, reaching 4 dB at 4.2 GHz and 6.7 dB at 5.2 GHz, while maintaining reasonable radiation efficiency. The proposed compact and gain-enhanced design offers a promising solution for sub-6 GHz IoT devices requiring efficient Dual-Resonant operation for reliable off-body communication. Future work may focus on further optimizing the bandwidth and efficiency of the antenna system for specific IoT use cases.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eJ. M. Tranquilla and S. R. Best, A study of quadrifilar helix antenna for global positioning system applications, IEEE Trans. Antennas Propagat., vol. 38, pp. 15451550, Oct. 1990.\u003c/li\u003e\n \u003cli\u003eA. M. Dinius, GPS antenna multipath rejection performance, MIT, Cambridge, MA, Lincoln Lab. Tech. Rep., Aug. 1995.\u003c/li\u003e\n \u003cli\u003eL. Boccia, G. Amendola, G. Di Massa, and L. Giulicchi, Shorted annular patch antennas for multipath rejection in GPS-based attitude determination, Microwave Opt. Technol. Lett., pp. 4751, Jan. 2001.\u003c/li\u003e\n \u003cli\u003eG. Di Massa and G. Mazzarella, Shorted annular patch antenna, Microwave Optical Technol. Lett., vol. 8, pp. 218 222, Mar. 1995.\u003c/li\u003e\n \u003cli\u003eL. Boccia, G. Amendola, and G. Di Massa, A shorted elliptical patch antenna for GPS applications, IEEE AntennasWireless Propagat. Lett., vol. 2, pp. 68, 2003.\u003c/li\u003e\n \u003cli\u003eJ. Jan and K. Wong, A dual band circularly polarized stacked elliptic microstrip antenna, Microwave Opt. Technol. Lett., vol. 24, no. 5, pp. 354357, Mar. 2000.\u003c/li\u003e\n \u003cli\u003eMustapha Iftissane, \u0026apos;\u0026apos;Conception of Patch Antenna at Wide Band\u0026quot;, Int. J. Emerg. Sci., 1(3), 400-417, September 2011\u003c/li\u003e\n \u003cli\u003eC. Vishnu, Rahul Rana, Design of Rectangular Microstrip Patch Antenna, M.Tech Thesis, National Institute of Technology, Rourkela,2009\u003c/li\u003e\n \u003cli\u003eB.T.P.Madhav, K.Praveen Kumar, J. Doondi Kumar, Microstrip GPS Patch Ceramic Antenna, International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 4, April 2012).\u003c/li\u003e\n \u003cli\u003eMustapha Iftissane, \u0026apos;\u0026apos;Conception of Patch Antenna at Wide Band\u0026quot;,Int. J. Emerg. Sci., 1(3), 400-417, September 2011\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"kl university","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"antenna, dual-band printed antenna, Sub-6GHz, AMC, iot","lastPublishedDoi":"10.21203/rs.3.rs-6595768/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6595768/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper introduces a compact dual-band printed antenna, meticulously designed for efficient operation under the Sub-6GHz frequency spectrum, targeting the burgeoning field of Internet of Things (IoT) applications. Specifically, the antenna is engineered to exhibit enhanced performance at 4.2 GHz and 5.2 GHz, leveraging the synergistic integration of a strategically designed metasurface and an artificial magnetic conductor (AMC) backing. This combination aims to significantly improve both the antenna's gain and its operational bandwidth. The radiating structure features a carefully shaped tapered design, intricately embedded with stepped rectangular slots. This design forms a compact, multi-resonant geometry capable of supporting the desired Dual-Resonant operation. To ensure seamless integration into modern, low-profile IoT hardware, a coplanar waveguide (CPW) feed technique is employed, maintaining a planar configuration. The AMC layer, crucial for performance enhancement, comprises periodic unit cells incorporating complementary slot designs. These unit cells are meticulously tailored to achieve dual zero-phase reflection characteristics near the antenna's operating bands. This in-phase reflection mechanism leads to improved impedance matching and a more directional radiation pattern. The entire antenna structure is fabricated on a cost-effective single-layer FR4 substrate, occupying a compact footprint of 36 mm \u0026times; 36 mm \u0026times; 0.8 mm. In terms of electrical size, this corresponds to approximately 0.83λg \u0026times; 0.83λg \u0026times; 0.018λg at 4.2 GHz and 1.08λg \u0026times; 1.08λg \u0026times; 0.024λg at 5.2 GHz, where λg represents the guided wavelength at the respective frequencies. The design demonstrates impressive peak gains of 4 dBi and 6 dBi at 4.2 GHz and 5.2 GHz, respectively. The integrated metasurface and AMC backing work in concert to effectively suppress detrimental surface wave propagation, enhance forward radiation characteristics, and maintain the overall compactness of the antenna. With its advantageous small footprint, high efficiency, and dual-resonant operation, the proposed antenna emerges as a compelling candidate for integration into next-generation Sub-6 GHz IoT devices that demand reliable and high-performance wireless communication within stringent space constraints.\u003c/p\u003e","manuscriptTitle":"A Metasurface-enhanced Dual-resonant Antenna With Amc Backing for Sub-6 Ghz Iot Devices","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 06:02:56","doi":"10.21203/rs.3.rs-6595768/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4445b44f-9edc-44aa-b980-06b28c7efe9c","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":48175642,"name":"Electronic Materials and Devices"}],"tags":[],"updatedAt":"2025-05-07T06:02:57+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-07 06:02:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6595768","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6595768","identity":"rs-6595768","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}