Design of BPF-Integrated SPDT Switch Based on Slotline Resonators Loaded With Diodes
Hao Wan, Jin Xu, Bin‐Yun Han, Guoqing Zhou, Yiqing Du, Lei Zhu
Abstract
Slotline Stepped-impedance resonators (SIR) loaded with p-i-n diodes are used to develop bandpass filter (BPF) integrated switches in this brief. The loaded diodes are used to switch the resonant conditions of the short-ended slotline resonators. The equations for their resonant conditions under different loads at different locations are derived and discussed. With these derived equations, the switchable filters are designed and synthesized using the classical coupled-resonator filter theory. The design concept is demonstrated by a Cascaded Quadruplet (CQ) BPF-integrated single-pole single-throw (SPST) switch at center frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0}\,\,=$ </tex-math></inline-formula> 1 GHz with 47.7 dB OFF-state suppression (OSS). Finally, two compact BPF-integrated single-pole double-throw (SPDT) switches are designed and fabricated. One of them combines source-load (S-L) coupling and introduces two additional zeros outside the desired passband to improve the frequency selectivity. The other on fractal common feeding line is developed to reduce the impact of accumulated residual admittances from OFF-state channels, which shows high roll-off rate of sidebands as well as high port-to-port isolation of 53.1 dB, and its overall circuit size is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.051 \lambda \text{g} ^{\mathrm{ 2}}$ </tex-math></inline-formula> .