An Autonomous Wireless Sensor Node With Asynchronous ECG Monitoring in 0.18 μ m CMOS

Abstract

The design of a 13.56 MHz/402 MHz autonomous wireless sensor node with asynchronous ECG monitoring for near field communication is presented. The sensor node consists of an RF energy harvester (RFEH), a power management unit, an ECG readout, a data encoder and an RF backscattering transmitter.The energy harvester supplies the system with 1.25 V and offers a power conversion efficiency of 19% from a dBm RF source at 13.56 MHz. The power management unit regulates the output voltage of the RFEH to supply the ECG readout with V and the data encoder with V.The ECG readout comprises an analog front-end (low noise amplifier and programmable voltage to current converter) and an asynchronous level crossing ADC with 8 bits resolution. The ADC output is encoded by a pulse generator that drives a backscattering transmitter at 402 MHz. The total power consumption of the sensor node circuitry is 9.7 W for a data rate of 90 kb/s anda heart rate of 70 bpm. The chip has been designed in a 0.18 m CMOS process and shows superior RF input power sensitivity and lower power consumption when compared to previous works.