Ring Resonator Based Compact Bandpass Filters for UWB Applications

In this paper novel microstrip ring resonator based compact Ultra-Wideband (UWB) bandpass filters using different coupling structures are presented. The proposed filters are designed to provide a wide passband, low insertion loss and return loss, linear phase over the passband, flat group delay and high fractional bandwidth. The simulation of bandpass filter (BPF1) with interdigital coupling results a passband of 7.4 GHz over 2.2–10.5 GHz, minimum insertion loss of approximately -2 dB, return loss of around -40 dB and – 10 dB fractional bandwidth of 120 % while for the filter (BPF 2) with dual line coupling, they are 7 GHz over 3-14 GHz, -0.09 dB, -33 dB and 127.27 % respectively. The computed group delay variation in the passband for BPF1 is 0.2 ns while for BPF2 0.03 ns. The overall dimensions of the filters are 38 mm (length) × 3.2 mm (height) ×3.175 mm (breadth) and 16.5 mm (length) × 2.5 mm (height) × 1.6 mm (breadth) respectively. They are simulated using electromagnetic (EM) simulator, IE3D.