{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,31]],"date-time":"2026-01-31T00:31:13Z","timestamp":1769819473005,"version":"3.49.0"},"reference-count":27,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2021,5,27]],"date-time":"2021-05-27T00:00:00Z","timestamp":1622073600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Noncontact monitoring of human vital signs has been an emerging research topic in recent years. A key approach to this monitoring is the use of the Doppler radar concept which enables real-time vital signs detection, resulting in a new class of radar system known as bio-radar. The antennas are a key component of any bio-radar module and their designs should meet the common requirements of bio-radar applications such as high radiation directivity and mechanical flexibility. This paper presents the design of a four-element antenna array on a flexible liquid crystal polymer (LCP) substrate of 100 \u03bcm thickness and \u03b5r of 3.35. The designed antenna array can be used with a 24 GHz bio-radar for vital signs monitoring in a non-contact manner. It features a relatively compact size of 36.5 \u00d7 53 mm2 and measured gain of 5.81 dBi. The two vital signs: breathing rate (BR) and heart rate (HR) of two human subjects are detected with relatively good accuracy using the fabricated antenna array and radio frequency (RF) output power of \u22123 dBm from a distance of approximately 60 cm. The effect of bending on the antenna performance is also analyzed.<\/jats:p>","DOI":"10.3390\/s21113737","type":"journal-article","created":{"date-parts":[[2021,5,27]],"date-time":"2021-05-27T11:07:02Z","timestamp":1622113622000},"page":"3737","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["24 GHz Flexible Antenna for Doppler Radar-Based Human Vital Signs Monitoring"],"prefix":"10.3390","volume":"21","author":[{"given":"Nitin","family":"Kathuria","sequence":"first","affiliation":[{"name":"Department of Electrical and Electronic Engineering, Auckland University of Technology, Auckland 1010, New Zealand"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9511-7521","authenticated-orcid":false,"given":"Boon-Chong","family":"Seet","sequence":"additional","affiliation":[{"name":"Department of Electrical and Electronic Engineering, Auckland University of Technology, Auckland 1010, New Zealand"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"202","DOI":"10.1109\/JMW.2020.3034988","article-title":"Micrometer sensing with microwaves: Precise radar systems for innovative measurement applications","volume":"1","author":"Michler","year":"2021","journal-title":"IEEE J. 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