A Compact Ka-Band Bandpass Filter With High Selectivity Using Dual-Mode Step-Impedance Resonators In GaAs IPD Technology

This paper presents a compact Ka-band bandpass filter chip in GaAs IPD technology using dual-mode step-impedance resonators (DMSIR). The proposed DMSIR is developed from a folded half-wavelength SIR with a short-circuit load at its center tap. The coupling between two DMSIRs can generate two transmission zeros (TZs) located at the vicinity of the passband for improving the selectivity. Finally, a prototype of the proposed dual-mode fourth-order filter chip is fabricated and measured. The measurement results show that it has a center frequency (fC) of 35 GHz, with a minimum insertion loss of 2.4 dB. Two TZs are observed at 28.4 GHz and 38.4 GHz, respectively, and the upper stopband is extended to 80 GHz (>2.28 fC) with more than 20 dB suppression.