Dual-Mode Filtering Switches Based on Hybrid Microstrip-Cavity Structures

Dual-mode filtering switches using hybrid microstrip-cavity structures are proposed in this article. TE₁₀₁ and TE₀₁₁ modes of the cavity act as the resonant modes to obtain a dual-mode filtering response. The microstrip line integrating the control circuit is employed as the feeding network. In the ON-state, the diode of the control circuit is reverse biased. Based on the electromagnetic (EM) coupling theory, the two modes are excited to attain filtering performance, and the loss of the diode is significantly alleviated. When the diode is forward biased, the two modes are suppressed and isolation in the OFF-state is realized. Benefiting from the hybrid microstrip-cavity configuration, the coupling between source/load and resonator is flexible to control. Single-band and dual-band filtering switches are constructed. The dual-band filtering switch processes high selectivity passband response in the ON-state, the insertion losses are 0.4 dB, and three transmission zeros are distributed in the two bands. In the OFF-state, the isolations of the two bands are below 37 and 30.7 dB, respectively. Thus, the dual-mode filtering switches maintain high- Q features as the cavities. Moreover, they have multifunctionality and flexibility compared to the conventional cavity structures fed by probes and waveguides.