Miniaturized frequency-agile bandpass filter integrated single-pole double-throw switch

摘要

This article presents a miniaturized frequency-agile bandpass filter (BPF) integrated single pole double throw (SPDT) switch using common LC resonator. The BPF-integrated on-sate channel is constituted by the capacitively coupled LC resonators with loaded varactor diodes and reverse-biased p-i-n diodes. The off-state channel with high suppression is built when the p-i-n diodes loaded LC resonators is forward-biased. As an example, a frequency-agile BPF-integrated SPDT switch with constant 3-dB fractional bandwidth of 18.4% is designed. Its fabricated circuit area including bias circuit but excluding feeding lines is 0.105 λ_g X 0.079 λ_g. Measured results show that its 3 dB operating frequency bandwidth covers from 0.499 to 1.077 GHz with in-band insertion loss varying from 4.15 to 3.15 dB. Off-state suppression better than 37.8 dB, port-to-port isolation better than 51.1 dB, and good return loss can be also observed.