Loss compensated high-Q tunable basspass filter using microstrip ring resonators

Abstract

A loss compensated tunable bandpass filter based on varactor-tuned microstrip square ring resonators is presented, which has a tuning range of 698–802MHz and steep skirt frequency response. The filter employs a PHEMT ATF34143 with appropriate feedback elements acting as a negative resistance circuit which not only reduces the insertion loss but also increases Q-factor significantly. According to the simulation results, the filter has a 3-dB fractional bandwidth of 1% and an insertion loss of about 6.8dB.