A high-selective multiple-mode bandpass filter design, applicating in both millimeter-wave 5G and WiFi systems

This paper proposes a millimeter-wave bandpass filter (BPF) with high selectivity, which can be applied in both 5G and WiFi systems. Two dual-mode resonators (DMRs) are adopted and analyzed coupled microstrip lines (CMLs) and can form six transmission poles (TPs) and four transmission zeros (TZs). Furthermore, a multiple-mode resonator (MMR) is presented based on the DMRs to realize a high selective passband. Additionally, five extra TZs are introduced by two pairs of open-circuited stubs and transversal signal interference (TSI), which are introduced by cross-coupling of two signal paths. These TZs significantly enhance out-of-band suppression performance. The proposed BPF is fabricated in ceramic process, and measurement results demonstrate a minimum insertion loss of −1.52 dB, a 3-dB passband from 38.3 to 48.2 GHz, a 30-dB rectangular coefficient of 1.21, and a 30-dB stopband extending to the test limit of 67 GHz.