Packaged Ka-Band IPD Bandpass Filter Using In-Phase and Out-of-Phase Mixed Couplings

By effectively merging in-phase and out-of-phase electric and magnetic mixed couplings in an in-line fourth-order topology, a high-selectivity millimeter-wave (mm-wave) bandpass filter (BPF) is proposed. The use of in-phase and out-of-phase mixed couplings introduces pairs of 180° phase shift, resulting in multiple transmission zeros (TZs) generated outside the passband, whose locations can be independently controlled by adjusting the coupling strength. Furthermore, the equivalent circuit models are analyzed and discussed to elucidate the operating mechanism. For experimental verification, a 25-GHz in-line fourth-order high-selectivity BPF is designed and fabricated using gallium arsenide (GaAs)-based integrated passive device (IPD) process. Compared with prior works, the proposed BPF shows the merits of high selectivity, wider rejection bandwidth, and low insertion losses, making it well-suited for enhancing receiver sensitivity and suppressing interference in satellite communication systems.