Direct synthesis method of wideband tunable filtering phase shifter based on complex matched transversal multiple resonances

In this article, a wideband filtering phase shifter (FPS) based on transversal multiple resonances is proposed. By utilizing transversal resonances with complex impedance, a wide operation band is achieved with compact circuit size. By doubly loading the tunable external coupling networks (ECNs) with complex impedance, the FPS obtains continuous phase tuning with stable filtering performance. In addition to the structural construction, a set of analytical formulas and guidelines for the direct synthesis of the FPS are provided, rather than tedious optimization. Finally, an FPS using transversal three resonances with complex impedance is designed, fabricated, and measured to validate the concept. The example showcases a wide 10-dB RL bandwidth of 32.5% with high selectivity, a compact size of 0.068 lambda(2)(g), a phase shift range (PSR) of 105 degrees, and a low phase error of +/- 5.4(degrees).