Compact LPF to UWB BPF transition employing quasi-triangular DGS resonators and a discontinuity on the microstrip feed line

Compact lowpass filter (LPF) and bandpass filter (BPF) are introduced in this paper. The proposed LPF presents small size, low insertion loss and ultra-wide stopband with 20 dB attenuation from 6 GHz to more than 20 GHz. The length of the proposed multilayer LPF is reduced to 0.143 λg @ 3 GHz in comparison with 0.2 λg for the cascaded topology with λg = 0.157 m. The proposed BPF is utilizing a simple transformation from LPF based on J-inverter technique. It has low insertion loss and compact size. The simulated and experimental results of the proposed structure are in good agreement.