A Passive RFID Temperature Sensor With 0.16 °C Resolution, +0.42 °C/ -0.83 °C Inaccuracy and 0.234 nJ/Conversion

Abstract

This article presents an ultralow-power radio frequency identification (RFID) with an embedded CMOS temperature sensor (TS). The thermometry working flow of the Query01-Query00-Ack sequence is introduced, which is compatible with the electronic product code (EPC) GEN-2 standard. A 2k-bit multitime programmable (MTP) nonvolatile memory (NVM) array with a standard CMOS process is used to store tag information, tag identification (TID), EPC, initialization parameter, and TS data. The proposed rectifier can achieve a wide power dynamic range (PDR) of 21.5 dB with peak power conversion efficiency (PCE) of 65%@−15 dBm under a 100-k $\Omega $ load. A protection mechanism for reliable reading and writing is presented to ensure proper tag initialization and avoid the ghost tag phenomenon. Time-domain digital quantization is adopted to convert the signal that period varies with temperature into a digital signal for low power consumption. The TS achieves a resolution of $0.16~^{\circ }$ C and inaccuracy of $+ 0.42~^{\circ }$ C/ $- 0.83~^{\circ }$ C after one-point calibration at $0~^{\circ }$ C in the temperature range from $- 20~^{\circ }$ C to $30~^{\circ }$ C. When the TS is powered at 1 V, it can achieve 0.234 nJ of energy per conversion in a conversion time of 1.8 ms. The passive RFID TS occupies an area of 0.5579 mm2 in the 0.13- $\mu $ m CMOS process. At the frequency of ~910 MHz, measured tag sensitivity can reach −22 dBm, and the 3-dB bandwidth is 51.5 MHz.