Miniaturised microstrip lowpass filter with broad stopband and sharp roll-off

Abstract

A novel miniaturised microstrip lowpass filter has been studied. With triangular and high–low impedance resonators symmetrically loaded, the proposed filter has successfully achieved size reduction and performance enhancement simultaneously. A demonstrator filter with 3 dB cutoff frequency at 1.5 GHz has been designed, fabricated and measured. Results show that a roll-off of 257 dB/GHz together with a relative stopband bandwidth of 157.4% can be obtained while achieving a high figure-of-merit of 38747.