Design of compact microstrip low pass filter using triangular and rectangular shaped resonator with ultra-wide stopband and sharp roll-off

Abstract

In this paper a new microstrip lowpass filter (LPF) is designed and fabricated with sharp roll-off and ultra-wide stop-band. To obtain these features, triangular and T-shaped resonators are utilized. The main resonator is created by two triangular and rectangular shaped structures. LC equivalent circuit and transfer function of the main resonator is extracted to compute transmission zeros of the main resonator. The proposed LPF has a 3 dB cut-off frequency of 1.663 GHz. The occupied size of the designed filter is 209.33 mm2 (17.3 mm × 12.1 mm). The ultra-wide stopband is achieved from 1.81 to 29.4 GHz with better than 20 dB attenuation. The achieved figure-of-merit of the proposed LPF is 33,813, which shows good specifications of the filter.