BPF-Integrated SPDT Switches With Improved Performance Using Frequency Selective Star-Junction Matching Circuit and Switched Magnetic Coupling Technique

摘要

This article presents a type of bandpass filter (BPF)-integrated single-pole double-throw (SPDT) switch using the frequency selective star-junction matching circuit and the switched magnetic coupling (SMC) technique, i.e., the lowpass phase shifter (LP-PS) and the quasi-elliptic lowpass filter (QE-LPF) with specified phase shift. Firstly, a high selectivity third-order BPF-integrated single-pole single-throw (SPST) switch with cross coupling and mixed electric and magnetic coupling (MEMC) is designed by the classical coupled-resonator filter design theory. A 34-dB OFF-state suppression (OSS) is achieved due to the detuned resonators, and the OSS can be further increased to 60 dB by the introduced SMC. Then, the BPF-integrated SPDT switches are designed by using proposed frequency selective star-junction matching circuit to cascade the above designed BPF-integrated SPST switch with or without SMC. The proposed frequency selective star-junction matching circuit is used to not only provide the required phase shift for meeting the impedance matching condition, but also have lowpass frequency response for expanding the upper stopband of ON-state channel, the rejection bandwidth of OFF-state channel, and the port-to-port isolation bandwidth. As examples, four BPF-integrated SPDT switches are designed and fabricated to validate the proposed design approaches, which show the improved electrical performance.