Comprehensive Comparison of Continuous-Wave and Linear-Frequency-Modulated Continuous-Wave Radars for Short-Range Vital Sign Monitoring

The use of radar technology for contactless monitoring of cardiorespiratory activity has been a significant research topic for the last two decades. However, despite the abundant literature focusing on the use of different radar architectures for healthcare applications, an in-depth analysis is missing about the most appropriate configuration. This article presents a comparison between continuous-wave (CW) and linear-frequency-modulated continuous-wave (LFMCW) radars for application in vital sign monitoring scenarios. These waveforms are generated with the same architecture at two different frequencies: 24 and 134 GHz. Results evidence that both configurations are capable of measuring general metrics, such as the breathing and heart rates. However, LFMCW offers better results in the identification of cardiac events and the extraction of certain derived biomarkers, such as the heart rate variability sequences (HRV). Conclusions show that this performance does not depend on the selected working frequency.