Compact dual-band quasi-elliptic bandpass filter with improved upper-stopband performance

Abstract

A compact dual-band bandpass filter with an improved upper stopband using defected ground structure is proposed. This filter offers quasi-elliptic responses at both the passbands, and the upper-stopband performance is improved by using end-coupled microstrip lines loaded with non-uniform shunt open stubs. An example dual-band bandpass filter is designed to demonstrate the effectiveness of the approach. The measurement shows a very good agreement with the simulation results. In addition, the implemented dual-band quasi-elliptic filter has a compact size of 0.24λ × 0.19λ and a wide stopband of better than 35-dB attenuation from 4.8 GHz to 9 GHz.