Single-/Dual-Band Bandpass Filter-Integrated Single-Pole Double-Throw Switch Using Distributed Coupling Tri-Mode Resonators

This article presents a method to design a single-band (SB)/dual-band (DB) bandpass filter (BPF)-integrated single-pole double-throw (SPDT) switch by using one/two distributed coupling identical tri-mode resonator (TMR) pairs loaded with opposite polarity p-i-n diodes. Moreover, the proposed method is also directly suitable for designing the multiple-band (MB) BPF-integrated SPDT switch by simply increasing the used numbers of identical TMR pairs. As an example, a SB-BPF-integrated SPDT switch with the central frequency (CF) of 1 GHz and the ripple bandwidth (RBW) of 65 MHz is first designed by using one identical switchable TMR pair, so as to validate our design approach. Due to the inherent property of TMR and the introduced source-load coupling, high ON-state passband selectivity is achieved. Then, two switched 50-Ω matching circuits are connected to two noncommon feeding lines, and an SB-BPF-integrated SPDT switch with absorptive OFF-state property is also realized. Finally, a DB-BPF-integrated SPDT switch with CFs of 0.9 GHz/1.8 GHz and RBWs of 50 MHz/105 MHz is designed by simply employing two identical TMR pairs. When the operating states of two identical switchable TMR pairs are specifically chosen, the proposed DB-BPF-integrated SPDT switch exhibits multiple functions, i.e., the 900/1800 SB-BPF-integrated SPDT switches with absorptive OFF-state property, the 900/1800 DB-BPF-integrated SPDT switch with absorptive OFF-state property, and the 900/1800 diplexer-integrated SPDT switch. The measured results also show that these switches exhibit low ON-state passband losses, deep out-of-band rejections (OBRs) of ON-state passbands, high OFF-state suppressions (OSSs), high port-to-port isolations (PPIs), and compact circuit sizes.