Wirelessly-Powered Printed Temperature Sensor with an Ultra-Low-Power and High-Sensitivity CMOS Readout IC

Abstract

This paper presents a wirelessly-powered high-sensitivity printed temperature sensor (TS). The proposed system consists of a -17dBm sensitivity RF-DC conversion circuit, a 2.2 mu W readout interface, and a printed NiO thermistor sensor. The 1 mm(2) printed NiO film has a good sensitivity index (B value) of 4000 K, but has high resistance (M Omega). The conventional readout system has difficulty detecting small resistance changes in the large thermal resistance range while only consuming a few microwatts, which is a need for enabling RF-power sensors remotely. A low-noise readout IC was designed to convert the resistance changes to digital codes. The proposed TS achieves a resolution of 0.04 degrees C/code in a temperature range of -20 degrees C to 90 degrees C, and measurement deviation within +/- 1.1%, while consuming only 2.2 nJ per conversion.