Interdigital Capacitor Based Compact Microstrip Bandpass Filter with Wide Stopband

Abstract

ABSTRACT A compact, low-cost microstrip bandpass filter (BPF) with low insertion loss and wide attenuation band is presented in this article. The proposed structure consists of multiple interdigital capacitor sections and a T-shaped stub which is connected to the ground using via. The wide stopband response is achieved by the inclusion of defected ground structures (DGS). Addition of these defected ground structures also reduces the circuit size. The designed BPF of centre frequency 0.9 GHz is fabricated, measured, and its lumped equivalent circuit is also obtained. A good agreement is found among IE3D simulated results, circuit simulated results, and the measured results. The obtained results for the proposed bandpass filter (BPF) are −3 dB fractional bandwidth (FBW) of 63% and minimum insertion loss of 0.59 dB. The relative stop band (RSB) rejection is found up to 177% and the normalized circuit size (NCS) is found 0.012. This proposed filter can be used for GSM and other microwave circuitry in wireless communication system.