A Novel Narrow Passband Millimeter Filter Using Suspended Improved Compact Microstrip Resonant Cell

A novel millimeter wave narrowband bandpass filter using improved suspended compact microstrip resonant cell is proposed in this paper. Compared to the traditional high/low step-impedance filter, the improved CMRC structure possesses good lowpass filter characteristics. Besides, it can shorten the circuit size over 50%. And a suspended CMRC has better filter characteristics of low return loss and sharper stopband rejection than a traditional CMRC. Based on the improved suspended CMRC, a novel millimeter wave narrowband BPF operating at center frequency of 40 GHz is designed and tested. The investigation results show that the BPF has low insertion loss below 1 dB in the narrow passband with a bandwidth of 10% and sharp rejection in the stopband.