A Dual Transmission Zero Bandpass Filter Employing Novel Hairpin-coupled Resonators for Improved Stopband Characteristics Application the Vital Signs Detection Radar

• Published in: Progress in electromagnetics research M Pier M Vol. 129; pp. 11 - 22
• Main Authors: Gao, Mingming, Yang, Yunshu, Nan, Jingchang, Wu, Handong, Wang, Xiaolin, Cui, Xuanye
• Format: Journal Article
• Language: English
• Published: Electromagnetics Academy 01.01.2024
• Subjects: Design and construction; Electric filters; Electric filters, Bandpass; Patient monitoring equipment; Radar systems; Resonators; China
• ISSN: 1937-8726; 1937-8726
• DOI: 10.2528/PIERM24071705

Conventional hairpin band-pass filters (BPFs) typically have poor stopband performances. Therefore, this paper proposes a BPF with a center frequency of 24 GHz that employs a novel hairpin-coupled structure. An enhanced hairpin-coupled resonator topology is also introduced to improve the stopband suppression characteristics. Specifically, the proposed resonator and filter are configured through a hairpin structure and source-third resonator coupling, which afford a miniaturized size and coupling of the transmission zeros. Then, an equivalent circuit model is simulated to conduct loss analysis of the millimeter-wave (mm-wave) BPF, and the corresponding analytical parameters and result data are extracted. Furthermore, fast synthesis is achieved for the high stopband suppression mm-wave filter. The compact BPF developed is fabricated using quart glass process, with the corresponding measurements revealing that the insertion Loss (IL) is less than 4.5 dB, and the return loss (RL) exceeds 9 dB within the passband. Meanwhile, the stopband suppression at 20.6 GHz and 28.6 GHz can reach 43 dB and 35 dB, respectively. Those advanced performances demonstrate the promising prospect of the proposed filter for its application in biological radar life feature monitoring.