Circuit analysis of coupled lines and open stubs based UWB microstrip BPF

Abstract

This paper presents the circuit analysis of ultra-wideband (UWB) microstrip bandpass filter (BPF) which is designed based on coupled lines and open stubs. The filter is proposed to have UWB characteristic response required for surface penetrating radar (SPR) application. The circuit analysis is performed based on transmission line model both for coupled lines and open stubs, and then characterized using circuit & EM simulator. In comparison to the analysis result, the designed UWB microstrip BPF is simulated using 3D EM simulator software. Here, the proposed filter is deployed on a grounded FR4 Epoxy dielectric substrate with the thickness of 0.8 mm. From the circuit analysis result, it shows that the proposed UWB microstrip BPF has −3dB working bandwidth of 4.31GHz ranges from the frequency of 1.97GHz to 6.28GHz yielding UWB response which is comparable with the result of 3D EM simulator. The minimum insertion loss and maximum return loss in the passband area are 0.47 dB and 11.42 dB at the frequency of 5.45 GHz, respectively.