A 900 MHz / 2.45 GHz RF frontend for passive RFID transponders

The RF frontend is one of the key elements in passive transponders, accounting for such diverse operations as RF-DC conversion, voltage regulation, modulation and demodulation of the incident RF wave. In this paper, the design of a high-performance frontend for passive RFID transponders under the international standard ISO/IEC 18000-4/6 is presented. Its physical implementation has been carried out on a commercial RF-CMOS 0.35?m technology. Special structures such as Schottky diodes and MIM capacitors are not necessary. The frontend provides a regulated supply voltage of 1V at a nominal current consumption of 2?A for the transponder back-end (the digital core and additional analog circuits such as an on-chip temperature sensor). The chip is matched to a specially designed resonant antenna. Measurement results coincide largely with those obtained though simulation, thus confirming the effectiveness of the design procedure. A maximum read-out distance of up to 5.1 m is achieved at UHF frequency band under European regulations. The front end can also operate in the microwave frequency band (2.45GHz) with a reduced read out distance.