Michler, Fabian, Shi, Kilin, Schellenberger, Sven, Steigleder, Tobias, Malessa, Anke, Hameyer, Laura, Neumann, Nina, Lurz, Fabian, Ostgathe, Christoph, Weigel, Robert, and Koelpin, Alexander
Vital parameters are key indicators for the assessment of health. Conventional methods rely on direct contact with the patients&rsquo, skin and can hence cause discomfort and reduce autonomy. This article presents a bistatic 24 GHz radar system based on an interferometric six-port architecture and features a precision of 1 µ, m in distance measurements. Placed at a distance of 40 cm in front of the human chest, it detects vibrations containing respiratory movements, pulse waves and heart sounds. For the extraction of the respiration rate, time-domain approaches like autocorrelation, peaksearch and zero crossing rate are compared to the Fourier transform, while template matching and a hidden semi-Markov model are utilized for the detection of the heart rate from sphygmograms and heart sounds. A medical study with 30 healthy volunteers was conducted to collect 5.5 h of data, where impedance cardiogram and electrocardiogram were used as gold standard for synchronously recording respiration and heart rate, respectively. A low root mean square error for the breathing rate (0.828 BrPM) and a high overall F1 score for heartbeat detection (93.14%) could be achieved using the proposed radar system and signal processing.