Compact microstrip lowpass filter with sharp roll-off using radial resonator

A compact microstrip lowpass filter (LPF) with sharp roll-off is presented. The proposed filter consists of radial resonator, triangular patch and open stub. The proposed filter has good specifications such as low insertion loss <;0.1 dB, high return loss of -20 dB, wide stopband from 4.37 to 19 GHz with -20 dB attenuation level and compact size. The LPF filter has a cut-off frequency of 3 dB at 4.24 GHz and a high roll-off rate of 130.7 and finally a high figure-of-merit of 23526.