CW radar system for no-contact and remote sensing of cardiac and respiratory movements

This paper deals with a continuous wave (CW) radar system as applied to medical environment with the scope of evaluating its capability of extracting vital signs of patients.By using a self-developed radar instrument, subjects were submitted to the device microwaves in different tests, changing their positions and physiological conditions, like normal respiration or apnea. Radar signals were processed for signal/noise enhancing and for extracting vital signs. Simultaneous recordings of the radar and true physiological signals, as coming from traditional diagnostic instrumentation,like piezoelectric band for respiration or ECG device for the electrocardiogram, allow to find an high correlation between hest movements or cardiac muscle activity and specific waves present in the radar signal. These results encouraged to develop a system for the automatic measurement of the breathing and heart rate from the radar signal alone; this system, based on a selective filtering of respiratory and cardiac frequencies and on adaptive template matching of cardiac cycles, was successfully tested on a limited number of cases in well controlled conditions. This completely non-invasive monitoring could be valuable for patients at risk and when it is not recommended the use of traditional instrumentation for health conditions (burnt patients) or for the context (at home),or simply for offering a good quality of life (like the elderly or infants)