Design of microstrip wide stopband lowpass filter with lumped equivalent circuit
A microstrip lowpass filter using stepped impedance resonator hexangular unit is presented. The proposed lowpass filter (LPF) has some appropriate features such as compact size, low insertion loss and wide stopband. The LPF has cut-off frequency at 2.8 GHz and stopband bandwidth from 3.15 up to 25.5 GHz with attenuation level better than −20 dB. Also, it has in-band insertion loss <0.1 dB and return loss better than 16.5 dB. Simulated and measured results are presented and relatively good agreement between them has been obtained.