Millimeter-wave on-chip dual-band bandpass filter using multi-stub resonator in GaAs technology

An on-chip dual-band bandpass filter (BPF) with wide bandwidth and low insertion loss is designed using 0.25-μm gallium arsenide (GaAs) technology. The proposed BPF is based on a multi-stub resonator (MSR) consisting of an open-circuited resonator loaded with a T-shaped open stub and a pair of L-shaped open stubs, which together generate four resonant modes to enhance the filtering performance. The resonant frequencies can be conveniently tuned by adjusting the geometric parameters. For demonstration, an on-chip dual-band BPF operating at 61.7 GHz and 94.5 GHz was fabricated and measured, achieving 3-dB fractional bandwidths (FBWs) of 35.1 % and 24.4 %, respectively. The measured in-band insertion losses are below 1.1 dB and 1.2 dB, with return losses greater than 20 dB. The overall circuit occupies only 0.356 × 0.252 mm², excluding input and output pads.