Low-power DSM-UWB RFID-based sensor system with low-process sensitivity

摘要

This Letter presents a RFID-based sensor system targeting internet of everything (IOE) application. The system consists of a sensor tag with time-domain sensor interface and a software defined radio receiver as the reader. In the proposed tag, a dual slope modulation (DSM) sensor interface combined with UWB transmitter (TX) is used to convert and transmit the sensing information in time domain. The sensor interface employs the DSM to reduce the output deviation caused by process variations. Moreover, the approach removes the need of time-to-digital converter (TDC) on tag and only three pulses are sent for each sample, resulting in significant power saving. On the reader side, the UWB pulses are detected and the intervals corresponding to the input signal are measured by a TDC. The UWB TX and DSM block of sensor tag is implemented in 0.18 μm CMOS process and FPGA, respectively. The system demonstrates 8-bit ENOB at 98 kS/s sampling rate. The mean percentage error of output results is less than ±0.5% under ±10% process variation. The power consumption of the tag is 127 μW with an figures of merit (FoM) of 5 pJ/conv.step, which is suitable for wirelessly powered IOE application.