Compact Microstrip Lowpass Filter with High Harmonic Suppression

Abstract

A planar lowpass filter designed using two resonators of different shape and four high-low impedance transmission lines being used as suppressing cells is realized with wide stopband and compact size. The proposed filter is found to remove up to seventh harmonics. The influence of each resonator on the design is studied separately. The cutoff frequency of the proposed filter is 2.57 GHz and its physical size is 14.6 mm x 9.6 mm. The selectivity is 92.5 dB/GHz. The measured stopband at 18 dB attenuation level is observed from 2.78 GHz to 20 GHz. Simulated results are validated with the measurement results and a good matching is observed between them.