Enabling Pervasive Sensing with RFID: An Ultra Low-Power Digital Core for UHF Transponders

In the near future, RFID transponders are expected to become a key element in the ubiquitous computing scenario. Tags will likely be used to collect sensors data, enabling non invasive environment monitoring. Low-cost passive UHF transponders are expected to play a major role in this context, due to extended read range capabilities. Within a passive tag, power harvested from the field irradiated by the reader during the communication should operate both digital control circuitry and potential sensing devices. Exploiting ultra low-power tag circuitry would provide sensing sections with higher energy, thus improving measurement performance. In this paper, the design of a novel circuit is presented, which implements the digital controller of a UHF-RFID tag in compliance with the ISO 18000-6B protocol. Power-saving strategies are devised, both at the system and the circuit levels. A set of standard cells has been designed, suitable for the power-limited specific application. Functional checks have been successfully performed by means of an FPGA-based prototype and physical implementation on CMOS 0.18 mum technology has been carried out. First test chip measurements support the selected design approach