In this letter, a packaged bandpass filter (BPF) with a compact size of $1.5 \times 1.5 \times 0.315$ mm³ operating at 28 GHz is proposed. This BPF is implemented based on a multilayers 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 (EM) 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.

中文翻译：

---

采用多层 PCB 技术的具有高选择性和宽阻带的小型化 28GHz 封装带通滤波器

在这封信中，一个封装的带通滤波器 (BPF) 具有紧凑的尺寸 $1.5 \times 1.5 \times 0.315$建议工作在 28 GHz 的mm ^{3 。}该 BPF 基于具有超薄基板的多层印刷电路板 (PCB) 制造工艺实现。通过封装配置，滤波器不仅可以减小电路尺寸和元件插入损耗，还可以消除电磁（EM）辐射的影响。为了验证上述机制，设计并制造了具有三个传输零点的封装毫米波 (mm-wave) BPF。实测结果表明，所提出的BPF具有插入损耗低、选择性高、尺寸紧凑等优点。同时，该 BPF 可以抑制高达 110 GHz 的谐波，抑制水平超过 24 dB。凭借这些优点，所提出的 BPF 对于 5G 毫米波应用具有吸引力。