Design And Fabrication Of Compact Microstrip Lowpass Filter With Ultra-Wide Stopband

This letter presents a novel design of a compact microstrip lowpass filter (LPF) with specifications such as ultra-wide stopband, sharp roll-off, compact size and low insertion loss using high impedance transmission lines loaded by front coupled horizontal beelines and asymmetric steps and radial stubs is presented. A demonstration filter with 3 dB cut-off frequency at 1.77 GHz has been designed, fabricated and measured. There is a good agreement between the EM-simulation and measurement results. Results indicate that a relative stopband bandwidth of 154% (referred to a 30 dB suppression) is obtained while achieving a highest figure-of-merit of 14424.94. Overall size of filter is 21.1 × 13.3 mm2, which is 0.171λg × 0.108λg at 1.77GHZ.

Keywords:

microstrip , lowpass filter , ultra-wide stopband , front-coupled , radial stubs