A Passive Reconfigurable Intermediate-Frequency Filter in GaAs Technology with High Rejection

This paper presents a passive reconfigurable intermediate-frequency (IF) bandpass filter (BPF) based on GaAs technology, consisting of a reconfigurable high- and a low-pass filter (LPF) connected in cascade. It features low insertion loss (IL) and a high rejection level. To reduce the IL caused by reconfigurable elements, these components are mainly applied in the shunt branches rather than in the main signal paths, for the purpose of adjusting transmission zeros. An enhanced rejection level is achieved by incorporating fixed TZ attributed to the LPF section. To validate the proposed design, a circuit prototype is designed, fabricated, and tested using a 0.15-μm GaAs p-HEMT process It demonstrated a bandwidth tuning range of 0.4-1 GHz at a center frequency of 1.8 GHz, with an an in-band IL between 2.65 dB and 5.17 dB, a return loss better than 16 dB, an out-of-band(OOB) rejection of up to 37 dB, and far-band rejection exceeding 60 dB.