Design of high suppression filter for millimeter-wave using glass-based advanced package integrated technology

A high-selective millimeter-wave bandpass filter (BPF) utilizing folded-line coupling resonator (FLCR) is presented. This BPF consists of four unitized FLCRs, which are realized by redistribution layer (RDL) on a glass interposer. There are electric and magnetic couplings among the resonators. By parameterizing the size and couplings of the FLCRs, the passband and four TZs can be readily controlled. To illustrate the operational principle, an equivalent circuit of the FLCRs is proposed and discussed. To validate the design, the BPF prototype working at 20.7 GHz is designed and fabricated. The measured results show that the designed BPF can achieve a 3-dB fractional bandwidth of 17.3 %. Moreover, the designed BPF exhibits a roll-off of 18.68 dB/GHz in the low sideband and a roll-off of 10.76 dB/GHz in the high sideband, thereby producing sharp-rejection filtering. In addition, it can achieve more than 36 dB of suppression from 0 to 14.6 GHz and more than 30 dB from 24.5 to 38.5 GHz. The fabricated BPF has a compact size of 1.73 mm x 1.1 mm (0.242 2g x 0.154 2g).