Compact low-cost microstrip lowpass filter with sharp roll-off and wide attenuation band

摘要

A compact low-cost lowpass filter (LPF) with sharp roll-off and wide attenuation band using stepped impedance resonator loaded with interdigital fingers and U-shaped resonator is recommended in this article. The proposed LPF has a cut-off frequency of 1.2 GHz with a sharp roll-off 135 dB/GHz and passband insertion loss 0.35 dB. An array of two different shapes of defected ground structures are etched in the ground plane for introducing additional transmission zeroes to enhance the stopband performance. The relative stopband suppression is achieved up to 171% with a suppression factor of 2. The proposed structure is modelled, fabricated, and measured. The measurement results are found to be well-matched with the simulated ones. Eventually, a high figure of merit of 21 600 is achieved.