Antenna evaluation of a non-contact vital signs sensor for continuous heart and respiration rate monitoring

A portable non-contact vital signs sensor system that is capable of continuously monitoring heart and respiration rates is presented. The system operates based on the continuous wave (CW) Doppler radar principle and has been evaluated using several antenna types: patch, Yagi, log-periodic and helical. The sensor operates at 2.4 GHz, realized on a custom designed low-cost PCB that integrates both the RF receiver (Rx) and transmitter (Tx) sections with analog electronics. It uses a quadrature receiver architecture with separate Tx and Rx antennas. The sensor using our custom designed helical antenna performs best among all antennas tested here. The sensor system can achieve a ±1 beat/min error versus the reference heartbeat signal for 75% of the continuous monitoring time, while the accuracy for the respiration rate is within ±1 breath/min for 95% of the time.