A differential wideband bandpass filter

Abstract

A wideband differential bandpass filter with enhanced common mode suppression and better out of band performance is presented in this paper. This filter consists of two back to back connected stepped impedance resonators (SIRs) coupled to each other through two dumbbell shaped slotline resonators. The size of the filter is 22 mm × 43 mm. The proposed filter has the differential passband bandwidth of 65 % centered around 4.85 GHz, with the common mode (CM) suppression better than 22 dB over the entire differential passband of the proposed filter. The insertion loss varies from 1.27 dB to 2.5 dB in the passband of the filter.