Patent ID: 8598992
Filing Date: 2013-12-03
Classification: G06K,H03J,H04B,Y10T

Abstract:
1. A RFID transponder comprising: an LC resonant circuit for providing a clock signal at a predetermined clock frequency in a received mode and for transmitting the predetermined frequency in a transmit mode; a self-calibration stage for calibrating the current clock frequency of the resonant circuit towards the predetermined clock frequency; wherein the self-calibration stage is adapted to compare a first clock frequency of the resonant circuit determined during an interrogation period, during which the resonant circuit is excited by an external RF signal, with a second clock frequency determined by the LC resonant circuit during a oscillation maintenance period, during which the resonant circuit is excited internally through an oscillation maintenance circuit of the RFID transponder and the external RF signal is absent, and to calibrate the resonant circuit towards the predetermined clock frequency based on the comparison result; and further comprising an auxiliary oscillator for providing an auxiliary clock signal, wherein the self-calibration stage comprises a first counter for counting clock periods of the clock signal and a second counter for counting clock periods of the auxiliary clock signal, wherein the calibration stage is further adapted to count the clock cycles of the auxiliary clock signal during a fixed number of clock cycles of the clock signal during the interrogation period and during the oscillation maintenance period and to compare the counts.