Miniaturized 28 GHz packaged bandpass filter with high selectivity and wide stopband using multi-layer PCB technology

In this paper, a packaged bandpass filter (BPF) with a compact size operating at 28 GHz is proposed. This BPF is implemented based on a high-precision multi-layers printed circuit board (PCB) fabrication process with ultra-thin substrate. With the packaged configuration, the filter can not only reduce the circuit size and component insertion loss, but also eliminate the effect of electromagnetic radiation. To verify the mechanisms mentioned above, a packaged millimeter-wave (mm-wave) BPF with three transmission zeros is designed and fabricated. The measured results show that the proposed BPF has the merits of low insertion loss, high selectivity, and compact size. Meanwhile, this BPF can suppress harmonics with a rejection level of more than 24 dB up to 110 GHz. With these merits, the proposed BPF is attractive for 5G mm-wave application.