Figure 2
From: Assessment of pulse rate variability by the method of pulse frequency demodulation
Block diagram of wireless trans-dermal photoelectric pulse wave monitoring system. This system detects pulse wave as the amount of light absorption by erythrocyte hemoglobin in pulsating epidermal capillary bed. Green light is emitted from a light-emitting diode (LED) to the skin and the reflected light is detected by a photodiode (PD) embedded in a sensor tip. The detected signal is amplified, digitized by an analog-to-digital (A/D) converter and processed with a serial signal conversion interface (SCI). The signal is then transmitted from a wireless micro-power module (303.825MHz). The signal is received with a receiving wireless module and processed by a microcomputer for data communications and error detection. The pulse wave signals are sent to board PC on which time series analyses including PFDM are performed and the results are presented on a liquid crystal display (LCD). AMP = amplifier, ANT = antenna, ASK = amplitude shift keying, OOK = on-off keying.