A Compact and High Selective Combline Bandpass Filter Using GaAs IPD Technology

This paper presents a combination of lumped and distributed components to construct a compact and high selective bandpass filter (BPF) by using GaAs (Gallium Arsenide) integrated passive device (IPD) technology. Specifically, a fourth-order BPF, where resonators are less than a quarter wavelength with the added lumped capacitors, is structured. A new coupling branch is proposed to add transmission zero for higher selectivity. The measurement shows that combline BPF achieves a shape factor of 1.6, insertion loss of 5 dB at center frequency of 2.8GHz and the out-of-band rejection is 30 dB and 20 dB. The combline BPF only occupies 1.84 mm2 die area excluding pads.