This paper describes the measurement of a driver's instantaneous heart rate corresponding to R-R interval in electrocardiogram and heart-rate variability (HRV) using 24 GHz radar reflectometers. Elimination of the spurious component due to random movement of a driver has been the most difficult problem for microwave measurement. Auto-gain control of the receiver, template matching and cross-correlation technique among multiple reflectometers enable motion artifact elimination, signal peak detection, and data processing for various parameters. The measurement of vital signals is considered useful for predicting the change in a driver's state, such as a heart attack as well as detecting drowsy driving, drunk driving, and fatigue.
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