Semi-Passive Time-Domain UWB RFID System

This paper presents a semi-passive time-domain ultra-wideband (UWB) radio identification system. The reader consists of a commercial, low-cost, and integrated impulse-radio radar. The tag is composed of a UWB antenna loaded with a transmission line, which is in turn terminated with a PIN diode. The tag answers to the interrogator by backscattering, modulating the amplitude of the time-domain reflected pulses sent by the radar. A 2.4-GHz downlink channel is used to wake up the tag, in order to increase the lifetime of the battery. The wake-up circuit is based on a diode rectifier and the internal comparator within the tag chip (a microcontroller) without needing additional active devices. Experimental results obtained with a proof-of-concept tag show that read-ranges up to 8.5 m can be achieved.