Accurate Through-Wall Breathing Rate Measurements Using a C-Band FMCW Radar

• Published in: IEEE sensors journal Vol. 25; no. 7; pp. 12097 - 12108
• Main Authors: Rouco, Andre, Pereira, Ana, Filipe Albuquerque, Daniel, Bras, Susana, Pinho, Pedro
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Accuracy; Breathing rate (BR) detection; C band; Cement industry; Clutter; Continuous radiation; Emergency response; Frequency ranges; frequency-modulated continuous-wave (FMCW) radar; Ground truth; Heart rate; Monitoring; noninvasive monitoring; Radar; Radar cross-sections; Radar detection; Real time; Real-time systems; Rescue operations; Root-mean-square errors; Search and rescue missions; Signal processing; Telemedicine; through-wall radar; Ultra wideband radar
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2025.3542605

This article introduces a novel approach to through-wall breathing rate (BR) detection using a custom-built C-band frequency-modulated continuous-wave (FMCW) radar. Operating within the 4-6-GHz frequency range, the radar leverages the C-band's ability to penetrate dense barriers, such as 30-cm-thick brick and cement walls, with high-resolution capability. Motivated by applications in healthcare and emergency response, this study addresses the need for noninvasive monitoring in scenarios where direct contact is impractical or impossible, such as isolating infectious patients or detecting life in search-and-rescue operations. Unlike traditional methods, this approach incorporates optimized radar settings and an innovative signal processing methodology. This enables accurate measurements without subject movement and allows for real-time applications. Experimental validation involved a diverse dataset of ten subjects, with radar-based BR measurements compared with ground-truth data from the Biopac system. Results demonstrated high accuracy, achieving a mean absolute error (MAE) of 0.07 BPM and a root mean square error (RMSE) of 0.09 BPM. These findings confirm radar robustness in challenging, real-world scenarios, establishing its potential as a cost-effective, reliable solution for through-wall BR monitoring.