A Packaged Tapered Balun with Improved Balance for Multi-Octave Power Combining

In this paper, a Packaged Tapered Balun (PTB) with enclosed metal shield is proposed to achieve multi-octave bandwidth operation for power combining applications such as push-pull power amplifiers and harmonics suppressed combiners. By establishing a parasitic transmission line equivalent circuit model of double-sided Shielded Tapered Lines, a suspended balance compensating branch and a common mode suppressed Balanced-to-Balanced transformer is introduced to improve the balance of PTB. Based on the proposed technique, a 0.6-6.5GHz PTB is demonstrated. According to the measured results, the designed balun exhibits better than -10dB return loss, -0.5dB insertion loss, ±0.15dB amplitude balance and ±0.4° phase balance.