Yong, QiZhao, Yifan2025-07-042025-07-042025-12-01Yong Q, Zhao Y. (2025) A contactless human vital sign monitoring system using a Doppler radar. Biomedical Signal Processing and Control, Volume 110, December 2025, Article number 1082231746-8094https://doi.org/10.1016/j.bspc.2025.108223https://dspace.lib.cranfield.ac.uk/handle/1826/24161Traditional vital signs monitoring methods are associated with certain limitations, such as requiring direct skin contact, causing potential distractions from sensors, and being susceptibility to electromagnetic interferences. Non-contact measurement methods have attracted growing interest but existing solutions face challenges in terms of working distance, accuracy, lack of temporal resolution, and applications in real-time heartbeat detection. This study introduces a novel non-contact vital sign monitoring system based on a K-band radar with dedicated algorithms for demodulation, parametric filter design, and self-adapting real-time heartbeat detection and extraction. This system provides precise and reliable per-beat heartrate detection and measurement, under a wide range of distances and working conditions, achieving superior performances and functionalities compared to existing contact-based implementations. By comparing with photoplethysmography and phonocardiogram sensors, the proposed system achieved real-time accurate per-beat heart rate measurement, with a relative root mean squared error of < 5 % for working distance of up to 3.2 m. Additionally, it can detect apneas and abnormal breathing activities, while also generating phonocardiogram and vibrography signals as a contactless virtual stethoscope. We anticipate that the solution will enable a wide range of applications including critical personnel monitoring, home and healthcare surveillance, self-assisted public health devices, and rescue operations.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Biomedical Engineering3006 Food sciencesContactlessVital signsDoppler radarParametric filter designingDigital signal processingArticle673943108223110