Carrier signal generation circuit and method for generating a carrier signal

Patent metadata

Field	Value
Publication number	US-10242303-B2
Application number	US-201715473295-A
Country	US
Kind code	B2
Filing date	Mar 29, 2017
Priority date	Jul 25, 2016
Publication date	Mar 26, 2019
Grant date	Mar 26, 2019

Abstract

In an embodiment, a carrier signal generation circuit can be used for a Radio-frequency identification (RFID) transponder device. A frequency divider circuit has a first input to receive a first frequency signal, a second input to receive a division ratio signal, and an output to provide a carrier signal as a function of the first frequency signal and the division ratio signal. A phase difference circuit has a first input to receive an analog reader device carrier signal, a second input to receive a signal based on the first frequency signal and an output to provide a digital phase difference signal as a function of the reader device carrier signal and the signal based on the first frequency signal. A signal processor has an input coupled to the output of the phase difference circuit.

First claim

What is claimed is:

1. A carrier signal generation circuit for a Radio-frequency identification (RFID) transponder device, the carrier signal generation circuit comprising:
a frequency divider circuit with a first input to receive a first frequency signal, a second input to receive a division ratio signal, and an output to provide a carrier signal as a function of the first frequency signal and the division ratio signal;
a phase difference circuit with a first input to receive an analog reader device carrier signal, a second input to receive a signal based on the first frequency signal and an output to provide a digital phase difference signal as a function of the reader device carrier signal and the signal based on the first frequency signal;
a signal processor having an input coupled to the output of the phase difference circuit, the signal processor being adapted to provide the division ratio signal dependent on the digital phase difference signal such that the division ratio signal is a function of a slope of the digital phase difference signal: and
a controller coupled to the frequency divider circuit, the phase difference circuit and to the signal processor, wherein the controller is configured to monitor an amplitude of the reader device carrier signal and to restart the signal processor in case of detection of an abrupt and significant increase of the amplitude of the reader device carrier signal.

2. The carrier signal generation circuit according to claim 1 , wherein the signal based on the first frequency signal is the carrier signal.

3. The carrier signal generation circuit according to claim 1 , wherein the carrier signal is provided by the frequency divider circuit according to a division of the first frequency signal by an adjustable divisor, which is adjusted dependent on the division ratio signal.

4. The carrier signal generation circuit according to claim 1 , wherein the signal based on the first frequency signal is a second frequency signal derived from the first frequency signal.

5. The carrier signal generation circuit according to claim 4 , wherein the frequency divider circuit comprises
a first frequency divider that is configured to provide the second frequency signal dependent on the first frequency signal by a fixed ratio division; and
a second frequency divider which is configured to provide the carrier signal.

6. The carrier signal generation circuit according to claim 4 , wherein the controller is further configured to initially align a phase of the carrier signal or a phase of the second frequency signal to a phase of the reader device carrier signal once using a reset or preset of the frequency divider circuit, the reset or preset being synchronized to the reader device carrier signal.

7. The carrier signal generation circuit according to claim 1 , wherein the phase difference circuit comprises:
a clock extraction circuit configured to receive the analog reader device carrier signal and to provide a digital reader device carrier signal as a function of the analog reader device carrier signal;
a comparator coupled to an output of the clock extraction circuit and configured to provide a preliminary phase difference signal dependent on a difference of phases between the digital reader device carrier signal and the carrier signal or a second frequency signal derived from the first frequency signal; and
a post-processing circuit configured to provide the digital phase difference signal dependent on the preliminary phase difference signal.

8. The carrier signal generation circuit according to claim 1 , wherein the signal processor comprises:
a low-pass filter configured to provide a filtered signal as a function of the digital phase difference signal by low-pass filtering, and
a slope calculation circuit configured to provide the division ratio signal by determining a slope of the filtered signal.

9. The carrier signal generation circuit according to claim 8 , wherein the signal processor further comprises an identifier circuit configured to provide an alternating signal dependent on the digital phase difference signal, wherein the alternating signal corresponds to an alternating component of the digital phase difference signal and wherein the alternating signal is provided to the slope calculation circuit.

10. The carrier signal generation circuit according to claim 1 , wherein the first frequency signal is supplied by a stable high frequency source and wherein a frequency of the first frequency signal amounts to a multiple of a frequency of the analog reader device carrier signal.

11. 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.

12. The method according to claim 11 , wherein the phase difference signal is generated by determining a phase difference between the reader device carrier signal and the carrier signal.

13. The method according to claim 11 , wherein the phase difference signal is generated by determining a phase difference between the reader device carrier signal and a second frequency signal that is derived from the first frequency signal.

14. The method according to claim 11 , further comprising aligning a phase of the carrier signal or a phase of the second frequency signal to a phase of the reader device carrier signal once by restarting generating the carrier signal or by restarting generation of the second frequency signal, the restarting being synchronized to the reader device carrier signal.

15. The method according to claim 11 , wherein generating the phase difference signal comprises:
digitizing the analog reader device carrier signal to provide a digital reader device carrier signal;
phase comparing the digital reader device carrier signal to the carrier signal or to the second frequency signal to provide a preliminary phase difference signal; and
processing the preliminary phase difference signal by correcting invalid values and correspondingly providing the phase difference signal.

16. The method according to claim 11 , wherein generating the division ratio signal comprises:
generating a filtered signal by periodically lowpass filtering the phase difference signal; and
determining a slope of the filtered signal.

17. The method according to claim 16 , wherein generating the division ratio signal further comprises:
identifying an alternating component of the phase difference signal and correspondingly providing an alternating signal; and
calculating the slope of the phase difference signal by subtracting the alternating signal from the filtered si

Assignees

• St Microelectronics Int Nv

Inventors

• Kunc Vinko
• Bratuz Iztok
• Pevec Albin
• Kovacic Kosta
• Stiglic Maksimiljan

Classifications

• H04L7/033

  using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop · CPC title

• G06K19/0723 Primary

  the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs · CPC title

• G06K19/0772

  Physical layout of the record carrier · CPC title

• G06K19/0775 Primary

  arrangements for connecting the integrated circuit to the antenna · CPC title

• G06K19/0724 Primary

  the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types · CPC title