A compact wide bandpass filter for satellite communications with improved out-of-band rejection

Abstract

This paper presents a compact C-band bandpass filter with improved out-of-band rejection. It consists of a symmetric three-pole parallel coupled line microstrip loaded with complementary split ring resonators (CSRRs) and slot resonators. Enhancements regarding the filter responses are obtained by etching these two parasitic shapes successively. When, CSRRs are introduced in the ground plane, exactly in the back of the transmission line of 50 Ω, improvements on the filter selectivity level are achieved. Whereas, the slot resonator elements are implemented on the feed line to per-mit the suppression of the second harmonics. To reduce the second harmonics of 11.1−13 GHz, the parasitic elements are both combined, widen the filter rejection of 5.81%. The surface current distribution together with the equivalent circuit are also studied in order to demonstrate the slots and the CSRRs effect parameters on the behavior of the proposed filter. A prototype of the optimal filter is fabricated and measured.Theory and experiment results prove the validity of the new design procedure.