Designing of High Gain U-Shaped Monopole Antenna using Uniplanar FSS layer for Ultra-Wideband Applications

Designing of High Gain U-Shaped Monopole Antenna using Uniplanar FSS layer for Ultra-Wideband Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Designing of High Gain U-Shaped Monopole Antenna using Uniplanar FSS layer for Ultra-Wideband Applications PARTHA Kumar DEB, Tamasi Moyra, Bidyut Kumar Bhattacharyya, Ananda Babu Devarapalli This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1397903/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 3 You are reading this latest preprint version Abstract In this manuscript, a novel high gain Microstrip Patch Antenna (MPA) is proposed using frequency selective surface (FSS) dedicated to operate at ultra-wideband (UWB) frequency domain between 3.1 to 10.6 GHz. The patch has been modified to a semi-circular shape and a partial ground technique is incorporated that also comprises a truncated semi-circular metallic plate to achieve desired high bandwidth. The FSS layer beneath the antenna has successfully augmented the gain of the antenna prototype by about 5–6 dBi. This FSS layer comprises of a 4×4 array of uniquely designed unit cells that satisfy the UWB specification and each cell size is 12×12 mm 2 . The integrated design provides an impedance bandwidth (IB) from 3.14 to 12.6 GHz. The proposed model finds application in the Worldwide Interoperability for Microwave Access (WiMAX) band, the C and X-band for satellite applications and in Wireless Local Area Network. The antenna is printed on a double-sided FR4 glass epoxy of 1.6mm thickness. A parametric investigation is conducted both for the FSS unit cell and the integrated design to optimize the antenna parameters to be suitable for the UWB frequency range. The optimized antenna size is 26×30 mm 2 and the integrated antenna size is 51×51 mm 2 . The antenna prototype has provided well similarity between simulated and measured results. Partial ground Ultra-wideband UWB frequency-selective surface (FSS) high gain impedance bandwidth (IB) Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 I. Introduction With the rapid increment in the number of users in the wireless communication systems, the major challenge arises as to providing communication infrastructure to each intended user. One of the ways to tackle this challenge is to use UWB and high gain antennas. The monopole antennas serve as a solution to achieve UWB with substantial advantages of low cost, smaller size, simple fabrication steps. But the surface wave on the antenna degrades the antenna gain, IB, directivity, etc. as well as raises the side lobe level and cross-polarization. A number of researchers have developed numerous techniques to tackle the problem of the surface wave. The most efficient technique is the use of metamaterial. These novel structures are engineered to produce rare physical properties like zero refractive index, double negative and left-handed material. It has gained a substantial research importance because of the exceptional electromagnetic properties. The uniplanar electromagnetic bandgap (EBG) structure or frequency selective surface (FSS) [ 1 ] which was first introduced by Ben A. Munk [ 2 ]. These are one or two-dimensional slots and metallic periodic resonant structures that introduce a stop-band and pass-band based on phase, frequency and polarization of the EM waves by the replication of a unit cell element. Its features are influenced by the periodicity, size and geometry of FSS elements [ 3 ]. To have practical realization based on a particular application, the points that a designer must need to consider are the FSS geometry, electrical properties, specifying the unit cells and the gap between them, the separation between the radiating patch and FSS layer. Its general applications are as pass-band filters [ 4 ], stop-band filters [ 5 ] and radar cross-section (RCS) reducers in radomes [ 6 ], absorbers [ 7 ] and beam splitters [ 8 ]. According to the federal communication commission (FCC) guidelines, the UWB antennas utilize 3.1–10.6 GHz frequency for EM wave propagation. The advantages of these antennas are high IB, low signal-to-noise ratio (SNR) with high data rate, less multi-path fading and narrowband signal [ 9 ]. Several researchers have proposed different kinds of printed monopole antennas [ 10 – 12 ] that had exhibited larger IB but with limited gain. Some of the techniques to improve the performance of the printed monopole antenna include modified ground plane, frequency selective surface (FSS), artificial magnetic conductor (AMC) and so on [ 13 – 15 ]. Among them highly efficient and useful technique is the use of FSS radiator that attracts a large research attention. The author in [ 16 ] designed a FSS based single layer planar trapezoidal monopole antenna with wider IB and high gain. The proposed antenna covered an IB of 2.4 GHz from 3.52–5.92 GHz frequency. It was also showed a maximum gain of 11.8 dBi at 5.1 GHz and the gain was maintained higher than 10.5 dBi for the entire IB. In [ 17 ], a compact high-gain UWB monopole antenna was proposed. The antenna was consisting of a U-shaped radiating patch and an edge-truncated partial rectangular ground plane with a rectangular slot at the centre. The gain of the UWB antenna had been enhanced with the help of FSS to a peak gain of 9.4 dBi. The proposed design also showed a significantly high front-to-back lobe ratio of ∼10 dB across the entire UWB range. In [ 18 ], a miniaturized single-layered FSS was proposed that consisted of a 4×4 array of unit cells of size 11×11 mm 2 . The gain was enhanced by 2 to 3.5 dBi when incorporated at the rear side of the antenna to work in a band from 2.82 to 19.94 GHz. In reference [ 19 ], the author had shown an UWB antenna using a double-layer FSS to boost the antenna performance for the applications in the Ku Band. The size of the antenna was 40.36×29.36 mm 2 with a 10 mm separation between the radiating patch and the FSS layer. The corners of the radiating patch were a rectangular truncated and the double-layer of FSSs consisted of rectangular loop unit cells in the bottom plane and the wire grid in the top plane. The optimized integrated UWB antenna was intended to work in 12.964 to 14.905 GHz frequencies. Reference [ 20 ] is about the design of the enhanced IB UWB antenna which was backed by a complementary split-ring resonator (CSRR) and an FSS layer to increase the gain. The FSS layer was a 10×10 array of FSS unit cell retained at a distance of 17 mm below the patch. The IB of 11.84 GHz was obtained. The peak gain was increased to 10.9 dBi from 4.9 dBi that was found at 3.79, 4.44, 7.89, 9.01 and 11.15 GHz frequencies. In another work [ 21 ], the authors had proposed a dumbbell-shaped FSS that was employed as a superstrate in two separate antennas to increase the gain and IB. The gain and IB of a circular patch antenna were found to be 6.02 dBic and 5.8–6.2 GHz operating region and for an inverted stacked microstrip patch antenna, it was enhanced by 5.1 dBic for the operating region of 5.8–6.2 GHz. In [ 22 ], the authors had incorporated a dual-band 7×7 spanner shape FSS to design a dual-band slot antenna to work at 3.53 and 6.2 GHz respectively. The gain of the two respective resonant frequencies was obtained as 13 dBi and 13.92 dBi. In this work, a novel antenna design is proposed to operate in the UWB region incorporating a 4×4 array of single layer FSS. This layer is separated by an optimized distance of 18 mm below the antenna ground plane. This integrated structure improves the gain of the antenna by 5 to 6 dBi throughout the UWB band and a peak gain of 11.36 dBi is achieved at 5.8 GHz frequency. The proposed design shows an IB of 9.46 GHz. The antenna is simulated in Ansoft HFSS 15.0. A rigorous parametric analysis has been carried out in antenna and FSS layer designing which helps to optimize the antenna size and to enhance the antenna performance. Ii. Uwb Antenna Design Inspired from [ 23 ], a U- shaped patch antenna is also proposed in this work based on inset- feeding technique whereas coplanar waveguide feeding was used in [ 23 ]. The proposed antenna is designed using FR4 glass epoxy of thickness 1.6 mm and relative permittivity of 4.4. The four-step design process is shown in Fig. 1 starting from a conventional rectangular microstrip patch antenna (RMPA) to the final proposed antenna. The feed width is 3.04 mm that helps to achieve impedance matching close to 50Ω characteristic impedance. To achieve wider IB, a partial ground technique is adopted which is evident from step-2 (in Fig. 1 (b)) onwards. The lower portion of the rectangular patch and upper portion of the ground are arched to obtain flare angle in the final proposed antenna in step-4 (shown in Fig. 1 (d)) which resembles the Vivaldi antenna radiating structure. This modification in the patch and ground plane enables the antenna to additionally resonate at higher frequencies and to produce wider IB. A semi-circular portion of radius 3.5 mm is removed from the top part of the ground plane. The effect of the ground plane modification is quite evident from reflection coefficient curves as shown in Fig. 2(a). It is clear that with the modification in the ground plane along with the radiating patch, the proposed design is capable to work in the UWB region between 3.1 to 10.6 GHz. But the gain of the proposed antenna is quite less as shown in Fig. 2(b). The integration of the antenna with the FSS layer as a measure of increasing gain is discussed in the later section. A parametric analysis of the U-shaped antenna will be given in the next section Iii. Parametric Analysis Of The U-shaped Antenna In this section, a parametric study is carried out to determine the effect of changing antenna feed width, semi-circular arc and semi-circular cut at the top of the ground plane on antenna performance. It will also help to optimize the antenna size. The variation of S(1,1) and peak gain for different values of feed width (fd) is shown in Fig. 3(a) & (b), for different values of radius (R) of the semi-circular portion in the ground plane and the various radius (r) of the semi-circular slot at the top edge of the ground plane are shown in Fig. 3(c) & (d) and (e) & (f) respectively. The center of the semi-circular ground is 7mm far from the lower edge of the ground plane. As shown in Fig. 3(a), there are four resonant peaks at 3.7, 6.6, 8.7 and 11.4 GHz. For all the variations of feed width (fd), these resonant peaks are located almost at the same frequency points with little variation. The best result is obtained for fd = 3.44 mm but the antenna produces less gain for this feed width. In the lower frequency edges highest gain is obtained for fd = 3.04 mm as shown in Fig. 3(b) which allows to select fd = 3.04 mm as an optimized feed width. In the next stage, the radius (R) of the semi-circular ground plane is varied while taking antenna feed width fixed at 3.04 mm as shown in Fig. 3 (c) & (d). Among all the variations, the four resonant peaks maintained their position in the S(1,1) plot and also well below − 10 dB throughout the UWB region for R = 18.5 mm. But the gain is somewhat less at the lower edges of the UWB region compare to the curve, R = 19 mm. In another stage of parametric analysis (shown in Fig. 3(e) & (f)), the radius (r) of the semi-circular slot at the top edge of the ground plane is varied while taking fixed fd and R at 3.04 mm and 18.5 mm respectively. It is found that all the return loss plots in Fig. 3(e) cover the whole UWB region except the plot for r = 4.5 mm. The plot for r = 3.5 mm produces the same four resonant peaks almost at the same frequency points with enhanced gain as evident from Fig. 3(f). Finally, the best result is obtained for fd = 3.04 mm, R = 18.5 mm and r = 3.5 mm which produces the IB of 9.12 GHz from 3.18 to 12.3 GHz. The peak gain of 7.6 dBi is observed at 3.2 GHz and 5.39 dBi is observed at 10.6 GHz. But the highest gain of 8.04 dBi is observed outside the UWB region at 12.1 GHz. The optimized antenna size is 26×30 mm 2 . Iv. Fss Unit Cell Design In the design of novel FSS unit cell, the FR4 substrate material of thickness 1.6mm and relative permittivity of 4.4 is used. The FSS array is observed with a 4×4 times periodic repetition of this unit cells in both x and y-direction which will act as an electromagnetic reflector for the proposed UWB antenna. The eight design steps are shown in Fig. 4 along with magnitude and phase response. The reflection phase response is shown in Fig. 5 and the Ansoft HFSS simulation setup is shown in Fig. 6 that includes master/slave boundary and Floquet ports at the top and bottom. The design parameters are Wu = Lu = 12.5mm, W 1 = L 1 = 6mm, R 1 = 2.8mm, R 2 = 2mm, L 2 = 3mm, W 2 = 2mm, a = 3mm, b = d = e = 1mm, c = 2mm, f = 0.8mm, g = 2mm. Since electromagnetic fields are similar in each of the unit cells it becomes simple to analyse the whole array by analyzing a single unit cell. As depicted in Fig. 4 (a), the 1st step of the FSS unit cell design comprises a square copper sheet of dimension W1×L1. This sheet is unable to produce a transmission zero anywhere in the desired UWB region. This results in a total transmission of EM waves which is not fulfilling the requirement of using the FSS layer as a reflector. In the 2nd step ( Fig. 4 (b)), a circular slot of radius R1 is incorporated which introduces a transmission zero around 11.7 GHz but it is failed to cover the whole UWB region. In the 3rd step ( Fig. 4 (c)), four rectangular sheets of dimension W2×L2 are joined at the edges of the square sheet of step 1 which shifts the location of transmission zero from 11.7 to 7.7 GHz but it covers the IB of 3.1 GHz between 6 to 9.1 GHz. The unit cell started producing better results as the structure is further modified and the best result is achieved in step 8 shown in Fig. 4 (h). In this step, the transmission zero is observed at 7.6 GHz and it covers the whole UWB region from 3.1 to 10.6 GHz and also beyond that up to 11.3 GHz. As evident in Fig. 5, the reflection phase decreases with the increment of frequency which is more prominent in step 3 and also gets fixed with no further decrement in the rest of the steps. This result provides a suitable environment for the FSS layer to enhance antenna-gain since it exhibits constructive interference with the antenna radiated waves. The reflection phase curve of the final step crosses the 00 lines at 7.9 GHz frequency. V. Antenna Integration With Fss The proposed U-shaped antenna is integrated with patch type 4×4 FSS layer as shown in Fig. 7 which reflects the back radiation in the direction of main radiation (major lobe) to enhance the gain along broadside direction. The FSS has shown a band-stop filter characteristic that consists of periodically placed metallic patches on a dielectric substrate. It is used to reflect a particular band of frequency. There is a constructive interference between these reflected waves when they are in phase with the antenna broadside radiation. As a result, antenna gain improves compare to the isolated antenna along the major lobe. The position of the FSS layer below the antenna is very crucial. The IB and gain are severely affected by the separation between the antenna and FSS layer and antenna location above the antenna. A parametric analysis is carried out to obtain an optimized separation (s) which is shown in Fig. 8. The parameters are varied within the range from 16 to 20 mm and the best result is obtained for s = 18 mm. The detailed parametric analysis result is shown in Table 1 which will be discussed in the next section. The antenna location is aligned considering the centre of the FSS layer. In the fabricated prototype, this separation is maintained with help of foam spacer as shown in Fig. 10 (d). In support of the FSS layer, a performance comparison is done by replacing the FSS layer with a PEC sheet. The result is plotted in Fig. 9 which gives a clear indication of better results with the FSS layer in terms of both reflection coefficient and gain within the UWB region. Table 1 Bandwidth and peak gain comparison for different separation between antenna and FSS layer Parameter/ Spacing (s) 16mm 17mm 18mm 19mm 20mm Operating frequency band (GHz) 3.2–3.95, 5.1-12.55 4.15–13.6 3.14–12.6 4.25–13.5 3.15–12.45 Peak gain (dBi) (max/min) 9.7/2.73 13.17/3.81 11.96/6.53 9.61/5.08 12.1/4.89 Vi. Result And Discussion In Fig. 10 , the fabricated model of the proposed design (Fig. 1 (d) and Fig. 7 (b)) is shown which is based on the FR4 substrate material. The measured result is plotted in Fig. 11 . The reflection coefficient (S11) measurement is carried out in Rohde & Schwarz ZNB20 vector network analyser. The E and H-plane co and cross-polarization radiation patterns are shown in Figs. 13 and 14 for all the four resonant frequencies (3.57 GHz, 5.7 GHz, 8.3 GHz and 11.8 GHz). The measured result shows the IB (below − 10 dB) from 3.14 GHz to 12.6 GHz and a maximum gain of 11.96 dBi at 5.8 GHz. A small difference between the simulated and measured results can be observed from the plots shown in Fig. 11 which is most obviously because of the losses in the imperfect soldering of the SMA connector. The FSS radiator is located below the antenna ground plane and the distance between them has varied and the above result obtained at a particular distance. This observation revealed that when the antenna is in close vicinity of the FSS layer, a difference can be found between the reflection coefficients of the integrated and isolated antenna. Therefore, it becomes very important to choose the position of FSS. The integrated antenna characteristic is recorded in Table 1 for different positions of the FSS radiator and corresponding graphs are plotted in Fig. 9. It is found that for the separation of 16 mm between the antenna and FSS the IB is divided into two regions (3.2–3.95 GHz and 5.1-12.55 GHz). The total IB achieved is 7.65 GHz and the peak gain is 9.7 dBi (max) and 2.73 dBi (min). For 17 mm of separation, it shows a total IB of 9.5 GHz (from 4.15–13.6 GHz). The maximum and minimum peak gain is 13.17 and 3.81 dBi respectively. The 18 mm separation produces the IB of 9.46 GHz (3.14–12.6 GHz) with a peak gain of 11.96 dBi (max) and 6.53 dBi (min). For 19 mm separation, the achieved IB is 9.25 GHz (4.25–13.5 GHz) and the peak gain is 9.61 dBi (max) and 5.08 dBi (min) and the total IB of 9.45 GHz (3.15–12.45 GHz) is achieved for 20 mm separation with the peak gain of 11.96 dBi (max) and 6.53 dBi (min). From this comparison table, it can be found that maximum IB and peak gain are achieved for 17 mm separation which is 9.5 GHz and 13.17 dBi respectively. But the achieved IB is not including the lower edge of the UWB region (unlicensed UWB region is 3.1–10.6 GHz). For the separation of 18 mm, the IB is somewhat less compared to 17 and 20mm separation but the minimum gain of 6.53 dBi is obtained at 10.6 GHz frequency which is the maximum among all other separations. The separation between the antenna and FSS reflector can also be verified by finding the far-field distance with the help of the equation F = 2D 2 /λ where F is the far-field distance, D is the largest dimension of the antenna which is 27 mm and λ = 81.08 mm is the wavelength related to first resonating frequency, 3.7 GHz of the antenna. The equated distance is 17.98 mm ≈ 18 mm. It is quite evident from Fig. 8(a) that the reflection characteristics get unaltered for the separation starting from 18 mm as all of them are in the far-field region. That’s why the minimum far-field distance; 18 mm is chosen as the separation between the antenna and FSS. As the monopole antenna radiation is primarily confined along the ± Z direction, the front-to-back ratio (FBR) of the U-shaped antenna without FSS is 8.6 dB at 10.64 GHz (simulated result) which is quite low as plotted in Fig. 12 . The FSS radiator works perfectly in reflecting the back radiation along the main lobe by increasing the FBR to 18.03 dB at 6.6 GHz frequency. It also maintains an average value of 9–10 dB across the UWB region whereas an average value of 4–5 dB is maintained by isolate antenna. The simulated radiation pattern for the proposed isolated antenna is plotted in Fig. 13 and for the proposed integrated antenna is plotted in Fig. 14. The comparison between their radiation pattern reveals that the integrated antenna becomes more directive along the broadside direction compared to the bidirectional radiation of the isolated antenna. It can be found that the E-plane co and cross-polarization isolation is more than 25 dB for both the isolated and integrated antenna. Though the isolation between H-plane co and cross-polarization is somewhat decreased in the integrated antenna compared to the isolated antenna but broadside radiation has enhanced in the case of integrated antenna. Vii. Performance Comparison The proposed work is compared with the similar kind of previous work that are designed in the UWB region with enhanced performance. This performance comparison is tabulated in Table 2 . In [ 15 ], a UWB antenna was designed for the frequency band of 2.7–13.9 GHz that employ a 6×6 array of FSS unit cells each of size 14×14mm 2 . This FSS layer increased the integrated antenna size which had produced a peak gain of 8.9 dBi and an overall gain improvement of 3.8 dBi. In [ 16 ], a trapezoidal-shaped antenna was designed to operate in the frequency region of 3.52–5.92 GHz with the help of a 5×5 array of FSS unit cells each of size 12.8×12.8 mm 2 that increased the antenna size. Even this design does not cover the whole unlicensed UWB region. The FSS based antenna, designed in [ 17 ], is considered a 6×5 array of unit cells to construct the FSS layer whose size is also compact and produces a peak gain of 9.4 dBi but it is still lesser than the proposed antenna design. The work shown in [ 19 ] consists of the most compact antenna among the works tabulated in Table 2 with the help of a 4×4 array of unit cells each of size 11.5×11.5 mm 2 . The antenna was designed to operate in the frequency band of 2.82–19.94 GHz but again the achieved peak gain is quite lesser than the proposed one. In [ 20 ], a 10×10-unit cell array-based co-planar waveguide feed antenna was designed. The antenna was quite compact and the achieved gain was also in appreciable level (10.9 dBi) but still lower than the proposed design. The work shown in [ 24 ] captured a wide area due to an 8×8 array of the unit cells. The size of each of the unit cells is 14×14 mm 2 and also obtained peak gain is quite lesser than the proposed work. Table 2 Performance comparison with existing works Ref. No. Antenna size (mm 2 ) Antenna size including FSS layer (mm 2 ) Operating frequency band (GHz) Peak gain (dBi) Gain improvement using FSS (dBi) [ 15 ] 26×34 81×84 2.7–13.9 8.9 3.8 [ 16 ] 30×24.5 64×64 3.52–5.92 11.8 8.6 [ 17 ] 16×22 52×62.5 3.1–18.6 9.4 6.9 [ 18 ] 34×41 41.75×41.75 2.82–19.94 7.6 3.5 [ 20 ] 35×30 53.15×53.15 3.16-15 10.9 6.5 [ 24 ] 20×27 84×84 4.7–14.9 8.7 4.5 This work 26×30 51×51 3.14–12.6 11.96 6 Viii. Conclusion A novel UWB antenna is proposed using a U-shaped microstrip patch antenna and a semi-circular ground plane to operate in the unlicensed UWB region. It shows an IB of 9.46 GHz (3.14–12.6 GHz). This design also incorporates a 4×4 array of unit cells to form an FSS radiator where the size of each cell is 12×12 mm 2 . The total size of the integrated antenna is 51×51 mm 2 . This FSS radiator acts as a reflector that reflects the back radiation along the main lobe that resulting in enhanced gain. The maximum peak gain of 11.96 dBi is achieved at a 5.75 GHz frequency. An average gain increment of 5–6 dBi is achieved throughout the band. The measured reflection coefficient is in good agreement with the simulated result. Declarations Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript Conflicts of interest/Competing interests The authors have no relevant financial or non-financial interests to disclose. Availability of data and material No datasets were generated or analysed during the current study. Code availability The work does not involve any software code. Authors' contributions Conceptualization, Methodology, Formal analysis and investigation, Writing - original draft preparation: [Partha Kumar Deb]; Writing - review and editing: [Partha Kumar Deb, Anand Babu Devarapalli]; Supervision: [Tamasi Moyra, Bidyut Kumar Bhattacharyya] References Praphat Arnmanee, C. P. (2018). 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High gain compact ultra-wideband antenna-frequency selective surface and its performance evaluation in proximity of soil surface. Microw Opt Technol Lett , 63, 869–875. doi: 10.1002/mop.32704 Das, P., & Mandal, K. (2019). Modelling of ultra-wide stop band frequency selective surface to enhance the gain of a UWB antenna. IET Microw. Antennas Propag , 13, 269–277. doi: 10.1049/iet-map.2018.5426 Supplementary Files Author.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 23 Feb, 2023 Editor assigned by journal 02 Mar, 2022 First submitted to journal 28 Feb, 2022 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. 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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-1397903","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":178268032,"identity":"5ab2da62-b18a-48f1-b770-ef09841d670f","order_by":0,"name":"PARTHA Kumar DEB","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYDCCAzxgKoGBvbHxAZDBw0ekFoMEBp7Dhw1AWtiI1yKRliYBYhLUwne899iDn3v+5PHPyDGr/JpjJ8PGwPzw0Q08WiTPnEs37HlmUCxx5o3ZbdltyUCHsRkb5+DRYnAjx0yC54BBYsPxHLPbktuYgVp42KTxarn/xkzyD1DL/AM5ZsWS2+qJ0HKDx0waZMuGE2lpjB+3HSasRfJMXrqxzAHjxI1nDh+WZtx2nIeNmYBf+I6fPfbwzQG5xHnHGxs//txWbc/P3vzwMT4tDMgRwQyOI2b8ylG1MP4grHoUjIJRMApGIAAAcM1O4mCSotMAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-6722-8737","institution":"National Institute of Technology Agartala","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"PARTHA","middleName":"Kumar","lastName":"DEB","suffix":""},{"id":178268033,"identity":"f5667496-f1d0-4617-a485-f8577a207242","order_by":1,"name":"Tamasi Moyra","email":"","orcid":"","institution":"National Institute of Technology Agartala","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Tamasi","middleName":"","lastName":"Moyra","suffix":""},{"id":178268034,"identity":"7211d2fd-2281-4e4d-9912-356a645f3c7f","order_by":2,"name":"Bidyut Kumar Bhattacharyya","email":"","orcid":"","institution":"Georgia Institute of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Bidyut","middleName":"Kumar","lastName":"Bhattacharyya","suffix":""},{"id":178268035,"identity":"0daa5548-62ca-498b-973c-bdf29d395d66","order_by":3,"name":"Ananda Babu Devarapalli","email":"","orcid":"","institution":"National Institute of Technology Agartala","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ananda","middleName":"Babu","lastName":"Devarapalli","suffix":""}],"badges":[],"createdAt":"2022-02-26 06:40:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1397903/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1397903/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":33412529,"identity":"bde8c754-2892-4600-ae17-3378edbc1ba6","added_by":"auto","created_at":"2023-02-24 15:26:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":241037,"visible":true,"origin":"","legend":"\u003cp\u003eUWB antenna design steps\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/58854101bb9b467b81680107.png"},{"id":33410217,"identity":"ead09b93-7b84-4418-8e72-41a0624f614d","added_by":"auto","created_at":"2023-02-24 15:02:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":87599,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Magnitude vs frequency plot, (b) peak gain vs frequency plot\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/9e4278a33f60b4898f182eeb.png"},{"id":33852080,"identity":"de55947c-e0f0-4bc1-8a51-c492dbb53b2a","added_by":"auto","created_at":"2023-03-06 16:45:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":258994,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated return loss and realized gain of U-shaped antenna for different values of (a), (b) feed width, (c), (d) radius of semi-circular shaped plane and (e), (f) radius of the semi-circular slot at the top edge of the ground plane.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/de080839b2be58afcd40e1c6.png"},{"id":33412937,"identity":"574f9787-7d5e-483a-bdb2-d228cda35efe","added_by":"auto","created_at":"2023-02-24 15:34:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":446102,"visible":true,"origin":"","legend":"\u003cp\u003eFSS unit cell design steps\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/46806852e99e2501e6d56434.png"},{"id":33412935,"identity":"d1a39a72-ffe4-4ba9-9500-8243b2238e69","added_by":"auto","created_at":"2023-02-24 15:34:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":109200,"visible":true,"origin":"","legend":"\u003cp\u003eReflection phase of different steps\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/70087564eb298c34bdeaf43e.png"},{"id":33852143,"identity":"3a487496-7e46-42c5-a1d6-5e1086189153","added_by":"auto","created_at":"2023-03-06 16:45:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":264038,"visible":true,"origin":"","legend":"\u003cp\u003eSimulation setup of the unit cell\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/f6393c68adc54e20dfb21545.png"},{"id":33412182,"identity":"15b14b7f-37c9-42b1-abbb-66d0c5d5c450","added_by":"auto","created_at":"2023-02-24 15:18:13","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":368702,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Proposed integrated antenna structure (b) 4×4 FSS layer\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/e50472eb3217057474be5973.png"},{"id":33410220,"identity":"ba74265b-9cb8-43a5-9931-0ff91e04118f","added_by":"auto","created_at":"2023-02-24 15:02:13","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":229343,"visible":true,"origin":"","legend":"\u003cp\u003eSimulation result obtained by varying the separation between antenna and FSS layer (a) return loss vs frequency plot and (b) peak gain vs frequency plot.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/f3055d235a4825c69d16b31a.png"},{"id":33412186,"identity":"d6bdc32d-141b-4559-9aa1-95f4407fa0c2","added_by":"auto","created_at":"2023-02-24 15:18:13","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":152652,"visible":true,"origin":"","legend":"\u003cp\u003eSimulation result obtained by replacing FSS reflector with PEC layer (a) return loss plot, (b) peak gain plot\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/e0396de9d464ed438d629ff4.png"},{"id":33411608,"identity":"607b943e-568f-40ba-baef-b2fa4d942ea6","added_by":"auto","created_at":"2023-02-24 15:10:13","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1049685,"visible":true,"origin":"","legend":"\u003cp\u003eThe fabricated prototype of the proposed antenna (a), (b) top and bottom view of the U-shaped patch antenna, (c) 4x4 FSS radiator, (d) final integrated antenna\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/db7ec6a1add7cfff9a93a20d.png"},{"id":33411597,"identity":"a1b46603-f4a0-4857-8434-a1646c946be4","added_by":"auto","created_at":"2023-02-24 15:10:13","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":158793,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated and measured result of the antenna with and without FSS (a) reflection coefficient vs frequency plot and (b) peak gain vs frequency plot\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/1dfe9c949c02f101fc94c35d.png"},{"id":33412188,"identity":"9f6a60b4-0e99-47ea-9ff3-d6f4e23d3a67","added_by":"auto","created_at":"2023-02-24 15:18:13","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":119421,"visible":true,"origin":"","legend":"\u003cp\u003eFront-to-back ratio comparison between the antenna with and without FSS radiator (Simulated result)\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/e275f66b4136866e11fee1c6.png"},{"id":33412533,"identity":"273ff67d-406b-4ea2-a282-4461b08360f1","added_by":"auto","created_at":"2023-02-24 15:26:13","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":149980,"visible":true,"origin":"","legend":"\u003cp\u003eE-plane co and cross polarization of isolated antenna for the resonant frequencies of (a) 3.57 GHz, (b) 5.7 GHz, (c) 8.3 GHz, (d) 11.8 GHz and H-plane co and cross polarization for the resonant frequencies of (e) 3.57 GHz, (f) 5.7 GHz, (g) 8.3 GHz, (h) 11.8 GHz (Simulated result).\u003c/p\u003e\n\u003cp\u003e*Co-Pol: Co-polarization, Cross-Pol: Cross-polarization\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/63bfb1f81195fb30000a62ef.png"},{"id":33412939,"identity":"6b671804-5ffa-4357-a2d1-025fe8f538db","added_by":"auto","created_at":"2023-02-24 15:34:13","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":154528,"visible":true,"origin":"","legend":"\u003cp\u003eE-plane co and cross polarization of the integrated antenna for the resonant frequencies of (a) 3.57 GHz, (b) 5.7 GHz, (c) 8.3 GHz, (d) 11.8 GHz and H-plane co and cross polarization for the resonant frequencies of (e) 3.57 GHz, (f) 5.7 GHz, (g) 8.3 GHz, (h) 11.8 GHz (Simulated result).\u003c/p\u003e\n\u003cp\u003e*Co-Pol: Co-polarization, Cross-Pol: Cross-polarization\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/7d0d0257a4a0c4f5732f10fa.png"},{"id":33852217,"identity":"dc9612bc-de14-45b6-a58f-e03c931a50fc","added_by":"auto","created_at":"2023-03-06 16:46:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2955643,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/2db2b655-849e-45e6-8944-4d6230b6786d.pdf"},{"id":33410218,"identity":"ec0630eb-4eda-40cd-b102-67fe89337f4f","added_by":"auto","created_at":"2023-02-24 15:02:13","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":46443,"visible":true,"origin":"","legend":"","description":"","filename":"Author.docx","url":"https://assets-eu.researchsquare.com/files/rs-1397903/v1/3583c8d907d0936bd47a84a4.docx"}],"financialInterests":"","formattedTitle":"Designing of High Gain U-Shaped Monopole Antenna using Uniplanar FSS layer for Ultra-Wideband Applications","fulltext":[{"header":"I. Introduction","content":"\u003cp\u003eWith the rapid increment in the number of users in the wireless communication systems, the major challenge arises as to providing communication infrastructure to each intended user. One of the ways to tackle this challenge is to use UWB and high gain antennas. The monopole antennas serve as a solution to achieve UWB with substantial advantages of low cost, smaller size, simple fabrication steps. But the surface wave on the antenna degrades the antenna gain, IB, directivity, etc. as well as raises the side lobe level and cross-polarization. A number of researchers have developed numerous techniques to tackle the problem of the surface wave. The most efficient technique is the use of metamaterial. These novel structures are engineered to produce rare physical properties like zero refractive index, double negative and left-handed material. It has gained a substantial research importance because of the exceptional electromagnetic properties. The uniplanar electromagnetic bandgap (EBG) structure or frequency selective surface (FSS) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] which was first introduced by Ben A. Munk [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These are one or two-dimensional slots and metallic periodic resonant structures that introduce a stop-band and pass-band based on phase, frequency and polarization of the EM waves by the replication of a unit cell element. Its features are influenced by the periodicity, size and geometry of FSS elements [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. To have practical realization based on a particular application, the points that a designer must need to consider are the FSS geometry, electrical properties, specifying the unit cells and the gap between them, the separation between the radiating patch and FSS layer. Its general applications are as pass-band filters [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], stop-band filters [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] and radar cross-section (RCS) reducers in radomes [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], absorbers [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and beam splitters [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the federal communication commission (FCC) guidelines, the UWB antennas utilize 3.1\u0026ndash;10.6 GHz frequency for EM wave propagation. The advantages of these antennas are high IB, low signal-to-noise ratio (SNR) with high data rate, less multi-path fading and narrowband signal [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Several researchers have proposed different kinds of printed monopole antennas [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] that had exhibited larger IB but with limited gain. Some of the techniques to improve the performance of the printed monopole antenna include modified ground plane, frequency selective surface (FSS), artificial magnetic conductor (AMC) and so on [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Among them highly efficient and useful technique is the use of FSS radiator that attracts a large research attention. The author in [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] designed a FSS based single layer planar trapezoidal monopole antenna with wider IB and high gain. The proposed antenna covered an IB of 2.4 GHz from 3.52\u0026ndash;5.92 GHz frequency. It was also showed a maximum gain of 11.8 dBi at 5.1 GHz and the gain was maintained higher than 10.5 dBi for the entire IB. In [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], a compact high-gain UWB monopole antenna was proposed. The antenna was consisting of a U-shaped radiating patch and an edge-truncated partial rectangular ground plane with a rectangular slot at the centre. The gain of the UWB antenna had been enhanced with the help of FSS to a peak gain of 9.4 dBi. The proposed design also showed a significantly high front-to-back lobe ratio of \u0026sim;10 dB across the entire UWB range. In [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], a miniaturized single-layered FSS was proposed that consisted of a 4\u0026times;4 array of unit cells of size 11\u0026times;11 mm\u003csup\u003e2\u003c/sup\u003e. The gain was enhanced by 2 to 3.5 dBi when incorporated at the rear side of the antenna to work in a band from 2.82 to 19.94 GHz. In reference [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], the author had shown an UWB antenna using a double-layer FSS to boost the antenna performance for the applications in the Ku Band. The size of the antenna was 40.36\u0026times;29.36 mm\u003csup\u003e2\u003c/sup\u003e with a 10 mm separation between the radiating patch and the FSS layer. The corners of the radiating patch were a rectangular truncated and the double-layer of FSSs consisted of rectangular loop unit cells in the bottom plane and the wire grid in the top plane. The optimized integrated UWB antenna was intended to work in 12.964 to 14.905 GHz frequencies. Reference [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] is about the design of the enhanced IB UWB antenna which was backed by a complementary split-ring resonator (CSRR) and an FSS layer to increase the gain. The FSS layer was a 10\u0026times;10 array of FSS unit cell retained at a distance of 17 mm below the patch. The IB of 11.84 GHz was obtained. The peak gain was increased to 10.9 dBi from 4.9 dBi that was found at 3.79, 4.44, 7.89, 9.01 and 11.15 GHz frequencies. In another work [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], the authors had proposed a dumbbell-shaped FSS that was employed as a superstrate in two separate antennas to increase the gain and IB. The gain and IB of a circular patch antenna were found to be 6.02 dBic and 5.8\u0026ndash;6.2 GHz operating region and for an inverted stacked microstrip patch antenna, it was enhanced by 5.1 dBic for the operating region of 5.8\u0026ndash;6.2 GHz. In [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], the authors had incorporated a dual-band 7\u0026times;7 spanner shape FSS to design a dual-band slot antenna to work at 3.53 and 6.2 GHz respectively. The gain of the two respective resonant frequencies was obtained as 13 dBi and 13.92 dBi.\u003c/p\u003e \u003cp\u003eIn this work, a novel antenna design is proposed to operate in the UWB region incorporating a 4\u0026times;4 array of single layer FSS. This layer is separated by an optimized distance of 18 mm below the antenna ground plane. This integrated structure improves the gain of the antenna by 5 to 6 dBi throughout the UWB band and a peak gain of 11.36 dBi is achieved at 5.8 GHz frequency. The proposed design shows an IB of 9.46 GHz. The antenna is simulated in Ansoft HFSS 15.0. A rigorous parametric analysis has been carried out in antenna and FSS layer designing which helps to optimize the antenna size and to enhance the antenna performance.\u003c/p\u003e"},{"header":"Ii. Uwb Antenna Design","content":"\u003cp\u003eInspired from [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e], a U- shaped patch antenna is also proposed in this work based on inset- feeding technique whereas coplanar waveguide feeding was used in [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. The proposed antenna is designed using FR4 glass epoxy of thickness 1.6 mm and relative permittivity of 4.4. The four-step design process is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e starting from a conventional rectangular microstrip patch antenna (RMPA) to the final proposed antenna. The feed width is 3.04 mm that helps to achieve impedance matching close to 50Ω characteristic impedance. To achieve wider IB, a partial ground technique is adopted which is evident from step-2 (in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e(b)) onwards. The lower portion of the rectangular patch and upper portion of the ground are arched to obtain flare angle in the final proposed antenna in step-4 (shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e(d)) which resembles the Vivaldi antenna radiating structure. This modification in the patch and ground plane enables the antenna to additionally resonate at higher frequencies and to produce wider IB. A semi-circular portion of radius 3.5 mm is removed from the top part of the ground plane. The effect of the ground plane modification is quite evident from reflection coefficient curves as shown in Fig.\u0026nbsp;2(a). It is clear that with the modification in the ground plane along with the radiating patch, the proposed design is capable to work in the UWB region between 3.1 to 10.6 GHz. But the gain of the proposed antenna is quite less as shown in Fig.\u0026nbsp;2(b). The integration of the antenna with the FSS layer as a measure of increasing gain is discussed in the later section. A parametric analysis of the U-shaped antenna will be given in the next section\u003c/p\u003e"},{"header":"Iii. Parametric Analysis Of The U-shaped Antenna","content":"\u003cp\u003eIn this section, a parametric study is carried out to determine the effect of changing antenna feed width, semi-circular arc and semi-circular cut at the top of the ground plane on antenna performance. It will also help to optimize the antenna size. The variation of S(1,1) and peak gain for different values of feed width (fd) is shown in Fig.\u0026nbsp;3(a) \u0026amp; (b), for different values of radius (R) of the semi-circular portion in the ground plane and the various radius (r) of the semi-circular slot at the top edge of the ground plane are shown in Fig.\u0026nbsp;3(c) \u0026amp; (d) and (e) \u0026amp; (f) respectively. The center of the semi-circular ground is 7mm far from the lower edge of the ground plane. As shown in Fig.\u0026nbsp;3(a), there are four resonant peaks at 3.7, 6.6, 8.7 and 11.4 GHz. For all the variations of feed width (fd), these resonant peaks are located almost at the same frequency points with little variation. The best result is obtained for fd\u0026thinsp;=\u0026thinsp;3.44 mm but the antenna produces less gain for this feed width. In the lower frequency edges highest gain is obtained for fd\u0026thinsp;=\u0026thinsp;3.04 mm as shown in Fig.\u0026nbsp;3(b) which allows to select fd\u0026thinsp;=\u0026thinsp;3.04 mm as an optimized feed width.\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003eIn the next stage, the radius (R) of the semi-circular ground plane is varied while taking antenna feed width fixed at 3.04 mm as shown in Fig.\u0026nbsp;3 (c) \u0026amp; (d). Among all the variations, the four resonant peaks maintained their position in the S(1,1) plot and also well below \u0026minus;\u0026thinsp;10 dB throughout the UWB region for R\u0026thinsp;=\u0026thinsp;18.5 mm. But the gain is somewhat less at the lower edges of the UWB region compare to the curve, R\u0026thinsp;=\u0026thinsp;19 mm. In another stage of parametric analysis (shown in Fig.\u0026nbsp;3(e) \u0026amp; (f)), the radius (r) of the semi-circular slot at the top edge of the ground plane is varied while taking fixed fd and R at 3.04 mm and 18.5 mm respectively. It is found that all the return loss plots in Fig.\u0026nbsp;3(e) cover the whole UWB region except the plot for r\u0026thinsp;=\u0026thinsp;4.5 mm. The plot for r\u0026thinsp;=\u0026thinsp;3.5 mm produces the same four resonant peaks almost at the same frequency points with enhanced gain as evident from Fig.\u0026nbsp;3(f).\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003eFinally, the best result is obtained for fd\u0026thinsp;=\u0026thinsp;3.04 mm, R\u0026thinsp;=\u0026thinsp;18.5 mm and r\u0026thinsp;=\u0026thinsp;3.5 mm which produces the IB of 9.12 GHz from 3.18 to 12.3 GHz. The peak gain of 7.6 dBi is observed at 3.2 GHz and 5.39 dBi is observed at 10.6 GHz. But the highest gain of 8.04 dBi is observed outside the UWB region at 12.1 GHz. The optimized antenna size is 26\u0026times;30 mm\u003c/span\u003e\u003csup\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e2\u003c/span\u003e\u0026nbsp;\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Iv. Fss Unit Cell Design","content":"\u003cp\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003eIn the design of novel FSS unit cell, the FR4 substrate material of thickness 1.6mm and relative permittivity of 4.4 is used. The FSS array is observed with a 4\u0026times;4 times periodic repetition of this unit cells in both x and y-direction which will act as an electromagnetic reflector for the proposed UWB antenna. The eight design steps are shown in\u003c/span\u003e Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e \u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003ealong with magnitude and phase response. The reflection phase response is shown in Fig.\u0026nbsp;5 and the Ansoft HFSS simulation setup is shown in\u003c/span\u003e Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e \u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003ethat includes master/slave boundary and Floquet ports at the top and bottom. The design parameters are Wu\u0026thinsp;=\u0026thinsp;Lu\u0026thinsp;=\u0026thinsp;12.5mm, W\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e1\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;L\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e1\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;6mm, R\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e1\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;2.8mm, R\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e2\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;2mm, L\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e2\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;3mm, W\u003c/span\u003e\u003csub\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e2\u003c/span\u003e\u003c/sub\u003e\u0026thinsp;\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e=\u0026thinsp;2mm, a\u0026thinsp;=\u0026thinsp;3mm, b\u0026thinsp;=\u0026thinsp;d\u0026thinsp;=\u0026thinsp;e\u0026thinsp;=\u0026thinsp;1mm, c\u0026thinsp;=\u0026thinsp;2mm, f\u0026thinsp;=\u0026thinsp;0.8mm, g\u0026thinsp;=\u0026thinsp;2mm. Since electromagnetic fields are similar in each of the unit cells it becomes simple to analyse the whole array by analyzing a single unit cell.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003eAs depicted in\u003c/span\u003e Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e(a), the 1st step of the FSS unit cell design comprises a square copper sheet of dimension W1\u0026times;L1. This sheet is unable to produce a transmission zero anywhere in the desired UWB region. This results in a total transmission of EM waves which is not fulfilling the requirement of using the FSS layer as a reflector. In the 2nd step (\u003c/span\u003eFig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e(b)), a circular slot of radius R1 is incorporated which introduces a transmission zero around 11.7 GHz but it is failed to cover the whole UWB region. In the 3rd step (\u003c/span\u003eFig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e(c)), four rectangular sheets of dimension W2\u0026times;L2 are joined at the edges of the square sheet of step 1 which shifts the location of transmission zero from 11.7 to 7.7 GHz but it covers the IB of 3.1 GHz between 6 to 9.1 GHz. The unit cell started producing better results as the structure is further modified and the best result is achieved in step 8 shown in\u003c/span\u003e Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cspan class=\"UnderlineSmallCaps\" name=\"Emphasis\" type=\"UnderlineSmallCaps\"\u003e(h). In this step, the transmission zero is observed at 7.6 GHz and it covers the whole UWB region from 3.1 to 10.6 GHz and also beyond that up to 11.3 GHz. As evident in Fig.\u0026nbsp;5, the reflection phase decreases with the increment of frequency which is more prominent in step 3 and also gets fixed with no further decrement in the rest of the steps. This result provides a suitable environment for the FSS layer to enhance antenna-gain since it exhibits constructive interference with the antenna radiated waves. The reflection phase curve of the final step crosses the 00 lines at 7.9 GHz frequency.\u003c/span\u003e\u003c/p\u003e"},{"header":"V. Antenna Integration With Fss","content":"\u003cp\u003eThe proposed U-shaped antenna is integrated with patch type 4\u0026times;4 FSS layer as shown in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e which reflects the back radiation in the direction of main radiation (major lobe) to enhance the gain along broadside direction. The FSS has shown a band-stop filter characteristic that consists of periodically placed metallic patches on a dielectric substrate. It is used to reflect a particular band of frequency. There is a constructive interference between these reflected waves when they are in phase with the antenna broadside radiation. As a result, antenna gain improves compare to the isolated antenna along the major lobe. The position of the FSS layer below the antenna is very crucial. The IB and gain are severely affected by the separation between the antenna and FSS layer and antenna location above the antenna. A parametric analysis is carried out to obtain an optimized separation (s) which is shown in Fig. 8. The parameters are varied within the range from 16 to 20 mm and the best result is obtained for s\u0026thinsp;=\u0026thinsp;18 mm. The detailed parametric analysis result is shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e which will be discussed in the next section. The antenna location is aligned considering the centre of the FSS layer. In the fabricated prototype, this separation is maintained with help of foam spacer as shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(d). In support of the FSS layer, a performance comparison is done by replacing the FSS layer with a PEC sheet. The result is plotted in Fig.\u0026nbsp;9 which gives a clear indication of better results with the FSS layer in terms of both reflection coefficient and gain within the UWB region.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\n \u003ctable border=\"1\" id=\"Tab1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBandwidth and peak gain comparison for different separation between antenna and FSS layer\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eParameter/ Spacing (s)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e16mm\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e17mm\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e18mm\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e19mm\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e20mm\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eOperating frequency band (GHz)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.2\u0026ndash;3.95, 5.1-12.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.15\u0026ndash;13.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.14\u0026ndash;12.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.25\u0026ndash;13.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.15\u0026ndash;12.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePeak gain (dBi) (max/min)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.7/2.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.17/3.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.96/6.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.61/5.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.1/4.89\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Vi. Result And Discussion","content":"\u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e10\u003c/span\u003e, the fabricated model of the proposed design (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d) and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b)) is shown which is based on the FR4 substrate material. The measured result is plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The reflection coefficient (S11) measurement is carried out in Rohde \u0026amp; Schwarz ZNB20 vector network analyser. The E and H-plane co and cross-polarization radiation patterns are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e13\u003c/span\u003e and 14 for all the four resonant frequencies (3.57 GHz, 5.7 GHz, 8.3 GHz and 11.8 GHz). The measured result shows the IB (below \u0026minus;\u0026thinsp;10 dB) from 3.14 GHz to 12.6 GHz and a maximum gain of 11.96 dBi at 5.8 GHz. A small difference between the simulated and measured results can be observed from the plots shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e11\u003c/span\u003e which is most obviously because of the losses in the imperfect soldering of the SMA connector.\u003c/p\u003e \u003cp\u003eThe FSS radiator is located below the antenna ground plane and the distance between them has varied and the above result obtained at a particular distance. This observation revealed that when the antenna is in close vicinity of the FSS layer, a difference can be found between the reflection coefficients of the integrated and isolated antenna. Therefore, it becomes very important to choose the position of FSS. The integrated antenna characteristic is recorded in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e for different positions of the FSS radiator and corresponding graphs are plotted in Fig.\u0026nbsp;9. It is found that for the separation of 16 mm between the antenna and FSS the IB is divided into two regions (3.2\u0026ndash;3.95 GHz and 5.1-12.55 GHz). The total IB achieved is 7.65 GHz and the peak gain is 9.7 dBi (max) and 2.73 dBi (min). For 17 mm of separation, it shows a total IB of 9.5 GHz (from 4.15\u0026ndash;13.6 GHz). The maximum and minimum peak gain is 13.17 and 3.81 dBi respectively. The 18 mm separation produces the IB of 9.46 GHz (3.14\u0026ndash;12.6 GHz) with a peak gain of 11.96 dBi (max) and 6.53 dBi (min). For 19 mm separation, the achieved IB is 9.25 GHz (4.25\u0026ndash;13.5 GHz) and the peak gain is 9.61 dBi (max) and 5.08 dBi (min) and the total IB of 9.45 GHz (3.15\u0026ndash;12.45 GHz) is achieved for 20 mm separation with the peak gain of 11.96 dBi (max) and 6.53 dBi (min). From this comparison table, it can be found that maximum IB and peak gain are achieved for 17 mm separation which is 9.5 GHz and 13.17 dBi respectively. But the achieved IB is not including the lower edge of the UWB region (unlicensed UWB region is 3.1\u0026ndash;10.6 GHz). For the separation of 18 mm, the IB is somewhat less compared to 17 and 20mm separation but the minimum gain of 6.53 dBi is obtained at 10.6 GHz frequency which is the maximum among all other separations. The separation between the antenna and FSS reflector can also be verified by finding the far-field distance with the help of the equation F\u0026thinsp;=\u0026thinsp;2D\u003csup\u003e2\u003c/sup\u003e/λ where F is the far-field distance, D is the largest dimension of the antenna which is 27 mm and λ\u0026thinsp;=\u0026thinsp;81.08 mm is the wavelength related to first resonating frequency, 3.7 GHz of the antenna. The equated distance is 17.98 mm\u0026thinsp;\u0026asymp;\u0026thinsp;18 mm. It is quite evident from Fig.\u0026nbsp;8(a) that the reflection characteristics get unaltered for the separation starting from 18 mm as all of them are in the far-field region. That\u0026rsquo;s why the minimum far-field distance; 18 mm is chosen as the separation between the antenna and FSS.\u003c/p\u003e \u003cp\u003eAs the monopole antenna radiation is primarily confined along the \u0026plusmn;\u0026thinsp;Z direction, the front-to-back ratio (FBR) of the U-shaped antenna without FSS is 8.6 dB at 10.64 GHz (simulated result) which is quite low as plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e12\u003c/span\u003e. The FSS radiator works perfectly in reflecting the back radiation along the main lobe by increasing the FBR to 18.03 dB at 6.6 GHz frequency. It also maintains an average value of 9\u0026ndash;10 dB across the UWB region whereas an average value of 4\u0026ndash;5 dB is maintained by isolate antenna.\u003c/p\u003e \u003cp\u003eThe simulated radiation pattern for the proposed isolated antenna is plotted in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e13\u003c/span\u003e and for the proposed integrated antenna is plotted in Fig.\u0026nbsp;14. The comparison between their radiation pattern reveals that the integrated antenna becomes more directive along the broadside direction compared to the bidirectional radiation of the isolated antenna. It can be found that the E-plane co and cross-polarization isolation is more than 25 dB for both the isolated and integrated antenna. Though the isolation between H-plane co and cross-polarization is somewhat decreased in the integrated antenna compared to the isolated antenna but broadside radiation has enhanced in the case of integrated antenna.\u003c/p\u003e "},{"header":"Vii. Performance Comparison","content":"\u003cp\u003eThe proposed work is compared with the similar kind of previous work that are designed in the UWB region with enhanced performance. This performance comparison is tabulated in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. In [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], a UWB antenna was designed for the frequency band of 2.7\u0026ndash;13.9 GHz that employ a 6\u0026times;6 array of FSS unit cells each of size 14\u0026times;14mm\u003csup\u003e2\u003c/sup\u003e. This FSS layer increased the integrated antenna size which had produced a peak gain of 8.9 dBi and an overall gain improvement of 3.8 dBi. In [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], a trapezoidal-shaped antenna was designed to operate in the frequency region of 3.52\u0026ndash;5.92 GHz with the help of a 5\u0026times;5 array of FSS unit cells each of size 12.8\u0026times;12.8 mm\u003csup\u003e2\u003c/sup\u003e that increased the antenna size. Even this design does not cover the whole unlicensed UWB region. The FSS based antenna, designed in [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], is considered a 6\u0026times;5 array of unit cells to construct the FSS layer whose size is also compact and produces a peak gain of 9.4 dBi but it is still lesser than the proposed antenna design. The work shown in [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] consists of the most compact antenna among the works tabulated in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e with the help of a 4\u0026times;4 array of unit cells each of size 11.5\u0026times;11.5 mm\u003csup\u003e2\u003c/sup\u003e. The antenna was designed to operate in the frequency band of 2.82\u0026ndash;19.94 GHz but again the achieved peak gain is quite lesser than the proposed one. In [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], a 10\u0026times;10-unit cell array-based co-planar waveguide feed antenna was designed. The antenna was quite compact and the achieved gain was also in appreciable level (10.9 dBi) but still lower than the proposed design. The work shown in [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] captured a wide area due to an 8\u0026times;8 array of the unit cells. The size of each of the unit cells is 14\u0026times;14 mm\u003csup\u003e2\u003c/sup\u003e and also obtained peak gain is quite lesser than the proposed work.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePerformance comparison with existing works\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRef. No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAntenna size (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAntenna size including FSS layer (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOperating frequency band (GHz)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePeak gain (dBi)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGain improvement using FSS (dBi)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e26\u0026times;34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e81\u0026times;84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.7\u0026ndash;13.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e30\u0026times;24.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e64\u0026times;64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.52\u0026ndash;5.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e16\u0026times;22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e52\u0026times;62.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.1\u0026ndash;18.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e34\u0026times;41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e41.75\u0026times;41.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.82\u0026ndash;19.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e35\u0026times;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e53.15\u0026times;53.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.16-15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e20\u0026times;27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e84\u0026times;84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.7\u0026ndash;14.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eThis work\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e26\u0026times;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e51\u0026times;51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.14\u0026ndash;12.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Viii. Conclusion","content":"\u003cp\u003eA novel UWB antenna is proposed using a U-shaped microstrip patch antenna and a semi-circular ground plane to operate in the unlicensed UWB region. It shows an IB of 9.46 GHz (3.14\u0026ndash;12.6 GHz). This design also incorporates a 4\u0026times;4 array of unit cells to form an FSS radiator where the size of each cell is 12\u0026times;12 mm\u003csup\u003e2\u003c/sup\u003e. The total size of the integrated antenna is 51\u0026times;51 mm\u003csup\u003e2\u003c/sup\u003e. This FSS radiator acts as a reflector that reflects the back radiation along the main lobe that resulting in enhanced gain. The maximum peak gain of 11.96 dBi is achieved at a 5.75 GHz frequency. An average gain increment of 5\u0026ndash;6 dBi is achieved throughout the band. The measured reflection coefficient is in good agreement with the simulated result.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest/Competing interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo datasets were generated or analysed during the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work does not involve any software code.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization, Methodology, Formal analysis and investigation, Writing - original draft preparation: [Partha Kumar Deb]; Writing - review and editing: [Partha Kumar Deb, Anand Babu Devarapalli]; Supervision: [Tamasi Moyra, Bidyut Kumar Bhattacharyya]\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003ePraphat Arnmanee, C. 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A compact uniplanar ultra-wideband frequency selective surface for antenna gain improvement and ground penetrating radar application. \u003cem\u003eInternational Journal of RF and Microwave Computer Aided Engg\u003c/em\u003e, 30, 22363. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/mmce.22363\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003ePramono, S., Adriyanto, F., \u0026amp; Sumantyo, J. T. S. (2021). Improvement of the Performance Characteristic of UWB Antenna Using a Novel Double-Layer FSSs Operating at the Ku-Band. \u003cem\u003eWireless Pers Commun\u003c/em\u003e, 121, 3297\u0026ndash;3308. Doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11277-021-08877-320\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eAvula Swetha and Kurukundu Rama Naidu. (2020). 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High gain dual band slot antenna loaded with frequency selective surface for WLAN/fixed wireless communication. \u003cem\u003eMicrow Opt Technol Lett\u003c/em\u003e, 61, 519\u0026ndash;525. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/mop.31559\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eKundu, S. (2021). High gain compact ultra-wideband antenna-frequency selective surface and its performance evaluation in proximity of soil surface. \u003cem\u003eMicrow Opt Technol Lett\u003c/em\u003e, 63, 869\u0026ndash;875. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/mop.32704\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eDas, P., \u0026amp; Mandal, K. (2019). Modelling of ultra-wide stop band frequency selective surface to enhance the gain of a UWB antenna. \u003cem\u003eIET Microw. Antennas Propag\u003c/em\u003e, 13, 269\u0026ndash;277. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1049/iet-map.2018.5426\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"wireless-personal-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wire","sideBox":"Learn more about [Wireless Personal Communications](https://www.springer.com/journal/11277)","snPcode":"11277","submissionUrl":"https://submission.nature.com/new-submission/11277/3","title":"Wireless Personal Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Partial ground, Ultra-wideband UWB, frequency-selective surface (FSS), high gain, impedance bandwidth (IB)","lastPublishedDoi":"10.21203/rs.3.rs-1397903/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1397903/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this manuscript, a novel high gain Microstrip Patch Antenna (MPA) is proposed using frequency selective surface (FSS) dedicated to operate at ultra-wideband (UWB) frequency domain between 3.1 to 10.6 GHz. The patch has been modified to a semi-circular shape and a partial ground technique is incorporated that also comprises a truncated semi-circular metallic plate to achieve desired high bandwidth. The FSS layer beneath the antenna has successfully augmented the gain of the antenna prototype by about 5\u0026ndash;6 dBi. This FSS layer comprises of a 4\u0026times;4 array of uniquely designed unit cells that satisfy the UWB specification and each cell size is 12\u0026times;12 mm\u003csup\u003e2\u003c/sup\u003e. The integrated design provides an impedance bandwidth (IB) from 3.14 to 12.6 GHz. The proposed model finds application in the Worldwide Interoperability for Microwave Access (WiMAX) band, the C and X-band for satellite applications and in Wireless Local Area Network. The antenna is printed on a double-sided FR4 glass epoxy of 1.6mm thickness. A parametric investigation is conducted both for the FSS unit cell and the integrated design to optimize the antenna parameters to be suitable for the UWB frequency range. The optimized antenna size is 26\u0026times;30 mm\u003csup\u003e2\u003c/sup\u003e and the integrated antenna size is 51\u0026times;51 mm\u003csup\u003e2\u003c/sup\u003e. The antenna prototype has provided well similarity between simulated and measured results.\u003c/p\u003e","manuscriptTitle":"Designing of High Gain U-Shaped Monopole Antenna using Uniplanar FSS layer for Ultra-Wideband Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-02-24 15:02:07","doi":"10.21203/rs.3.rs-1397903/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2023-02-23T05:53:31+00:00","index":0,"fulltext":""},{"type":"editorAssigned","content":"","date":"2022-03-02T05:10:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Wireless Personal Communications","date":"2022-03-01T01:45:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"wireless-personal-communications","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wire","sideBox":"Learn more about [Wireless Personal Communications](https://www.springer.com/journal/11277)","snPcode":"11277","submissionUrl":"https://submission.nature.com/new-submission/11277/3","title":"Wireless Personal Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f231af0e-a632-42fe-a71b-a3b05172e8f1","owner":[],"postedDate":"February 24th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2023-08-27T17:21:22+00:00","versionOfRecord":[],"versionCreatedAt":"2023-02-24 15:02:07","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1397903","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1397903","identity":"rs-1397903","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}