A remote-powered RFID tag with 10Mb/s UWB uplink and -18.5dBm sensitivity UHF downlink in 0.18µm CMOS

A remote-powered UWB RFID tag in 0.18μm CMOS is presented. The innovation is to employ asymmetric communication links, i.e. UWB uplink and UHF downlink in order to achieve extremely low power, high data rate and accurate positioning. Measurement shows the tag can operate up to 10Mb/s with minimum input power of 14.1μW, corresponding to 13.9 meters of operation range. Wireless sensing and positioning are new added functions highly demanded in future and emerging RFID technology [1]. Data rate of existing passive RFID is limited to few hundreds of kb/s causing large latency. On the other hand, the position accuracy is not better than 70cm [2]. In a advanced design, 3.4Mb/s data rate has been achieved in proximity operation [3]. Active tags with narrowband radio link overcome these weaknesses but, they are battery powered and more expensive. Impulse Ultra wideband (I-UWB) technique using short pulses for data transmission has been recognized as a powerful candidate for future RFID systems. It has the possibility of achieving MB/s throughput, operating range of several tens of meters, centimeters positioning, low power consumption, and low cost implementation. Previous works have revealed that UWB transmitter is extremely area and power efficient, whereas the receiver is still area and power hungry which requires internal power source [4]. In this work, we present a 10Mb/s impulse UWB RFID tag in 0.18μm CMOS. The tag is remotely powered by UHF wave with minimum input RF power as low as 14.1μW. Our innovative contribution is to employ two different communication links (UWB and UHF) respectively in uplink and downlink of the tag. This is because the amount of data or instruction from a reader to a tag is very few and a normal communication link as conventional UHF-RFID at 900 MHz could be used as downlink. UHF also provides remote power to the tag. The uplink requires higher data rate and precise positioning capability therefore an I-UWB transmitter is employed. Fig. 1 shows the block diagram of the tag. A power scavenging unit consisting of 9-stages CMOS voltage multiplier rectifies the incoming 900MHz RF signal to DC in a storage capacitor. The instantaneous power consumption of the circuits is too high to be operated constantly by remote-power. Therefore, a voltage-sensor, which consumes less than 1.5μA, activates the operation only when the voltage in storage capacitor reaches 2.75 V. The required energy for operation is provided by the stored energy in …