A transponder IC for wireless identification systems

A novel batteryless, self-powered transponder design as well as its chip layout is presented. The transponder operates in two phases. First, the chip is energized by rectifying the electromagnetic energy from the interrogating RF field from the RFID base station; the extracted energy is temporarily stored and is thereafter used to power the whole circuitry. Second, the transponder starts to transmit coded data by FSK modulation back to the base station. The major part of the design uses a digital CMOS circuit, thus it is simple and easy to implement. The circuit is designed such that the output frequencies are independent of the load of the antenna; the simulation results show that the tolerance of the antenna variation is within /spl plusmn/10%. The design is compatible with the TIRIS system, a popular RFID product designed by Texas Instruments. It operates in the 134.2 and 123.2 kHz frequency bands. The layout occupies about 0.8 um/spl times/0.8 um area.