Carrier signal generation circuit and method for generating a carrier signal

A method for generating a carrier signal in an RFID transponder device, the method comprising:

• receiving an analog reader device carrier signal;
• generating the carrier signal by frequency division of a first frequency signal by an adjustable divisor that is determined depending on a division ratio signal;
• generating a phase difference signal by determining a phase difference between the reader device carrier signal and the carrier signal or by determining a phase difference between the reader device carrier signal and a second frequency signal which is derived from the first frequency signal;
• and
• generating the division ratio signal dependent on the phase difference signal such that the division ratio signal is a function of a slope of the phase difference signal;
• monitoring an amplitude of the reader device carrier signal;
• discarding the adjustable divisor provided with the division ratio signal;
• and
• restarting generation of the carrier signal, the phase difference signal and the division ratio signal upon detection of an abrupt and significant increase of the amplitude of the reader device carrier signal.

A carrier signal generation circuit for a Radio-frequency identification (RFID) transponder device, the carrier signal generation circuit comprising:

• a frequency divider with a first input to receive a first frequency signal, a second input, and an output to provide a carrier signal;
• a clock extractor configured to generate a reader device carrier signal;
• a digital phase comparator having a first input coupled to the output of the frequency divider and a second input coupled to an output of the clock extractor;
• a post-processing circuit with an input coupled to an output of the digital phase comparator;
• a low-pass filter with an input coupled to an output of the post-processing circuit;
• an AC component identification circuit with an input coupled to an output of the low-pass filter;
• a slope calculation circuit having a first input coupled to the output of the low-pass filter, a second input coupled to an output of the AC component identification circuit, and an output coupled to the second input of the frequency divider;
• and
• a controller coupled to the frequency divider, the clock extractor, the digital phase comparator, the post-processing circuit, the low-pass filter, the AC component identification circuit, and the slope calculation circuit, wherein the controller is configured to monitor an amplitude of the reader device carrier signal and to restart at least one of the low-pass filter, the AC component identification circuit, and the slope calculation circuit in response to a detection of an abrupt and significant increase of the amplitude of the reader device carrier signal.