Real-Time Heart Rate Monitoring via Batteryless RFID Tags

This paper introduces a system wherein a battery-less RFID tag is capable of sensing the heartbeats of a mobile individual, while an RFID reader wirelessly detects them. The key advantage of the designed tag is its transmission of sensed data through the phase of the reflected signal to the reader, rather than its amplitude, rendering it more immune to noise and disturbance. The tag comprises three blocks: heartbeat detection, energy harvester, and three-port RFID structure. The main power consumption of the proposed tag is by the microcontroller, which consumes a maximum of 1.69 mu A at a 3.6 V power supply, making it a suitable option for energy harvesting applications. The minimum detectable pulse width of heartbeats by this system is measured at 60 ms, indicating that heart rates up to 250 bpm can be detected by this system, considering a duty cycle equal to 25% for the pulse.