Carrier synchronization appropriate for ALM NFC data transmission

Patent metadata

Field	Value
Publication number	US-9712317-B2
Application number	US-201514918284-A
Country	US
Kind code	B2
Filing date	Oct 20, 2015
Priority date	Feb 17, 2015
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

In some aspects, the disclosure is directed to methods and systems for carrier synchronization in active load modulation for near field communications. A broadcast carrier is received from a remote device and mixed with a locally-generated carrier and modulated data. A carrier synchronization circuit synchronizes the locally-generated carrier with the broadcast carrier based on an identified phase error from a double Cartesian-to-polar mapping of the mixed locally-generated carrier and broadcast carrier. In some implementations, the system also includes a modulation suppression circuit for providing unmodulated carrier signals to the carrier synchronization circuit or suppressing modulation distortion to maintain frequency and phase tracking despite the presence of data.

First claim

We claim:

1. A system for carrier synchronization in near field communications, comprising:
a first circuit configured to convert a first pair of signals representing Cartesian coordinates of an aggregated near field communication signal comprising a broadcast carrier from a remote device and a locally-generated carrier into a second pair of signals representing polar coordinates of the aggregated near field communication signal;
a second circuit configured to identify and remove an offset from each of the second pair of signals to generate a third pair of signals; and
a third circuit configured to convert the third pair of signals from a Cartesian to polar representation and provide an output phase angle of the polar representation of the third pair of signals to a frequency adjustment circuit of a local carrier generator.

2. The system of claim 1 , further comprising the frequency adjustment circuit configured to adjust a frequency of the local carrier generator into synchronization with the broadcast carrier from the remote device.

3. The system of claim 2 , wherein the frequency adjustment circuit comprises a charge pump.

4. The system of claim 2 , wherein the frequency adjustment circuit comprises an array of dynamically switchable capacitors.

5. The system of claim 4 , wherein the dynamically switchable capacitors have binary coded values.

6. The system of claim 4 , wherein the dynamically switchable capacitors have unary coded values.

7. The system of claim 1 , wherein the second circuit is configured to identify and remove the offset responsive to detection of a pause in transmission of modulated data by the system.

8. The system of claim 1 , wherein the second circuit is configured to subtract an average amplitude rave of the second signals from the second signals to generate an envelope of the third pair of signals.

9. The system of claim 1 , further comprising a selector configured to provide one of either of the output of the second circuit or the output of the third circuit to the frequency adjustment circuit, responsive to detection of presence or absence of modulated data, respectively.

10. The system of claim 1 , wherein the first circuit further comprises a decimator.

11. The system of claim 1 , further comprising a direct digital frequency synthesizer (DDFS) configured to receive the output of the second circuit, the DDFS configured to generate a phase correction signal based on the output of the second circuit.

12. A method for carrier synchronization in near field communications, comprising:
receiving, by a first circuit of a first device, a near field communication signal comprising an aggregated broadcast carrier from a second device and a locally-generated carrier from the first device;
converting, by a second circuit of the first device, a Cartesian representation of the aggregated broadcast carrier to a polar representation;
removing, by a third circuit of the first device, an offset from the polar representation of the aggregated broadcast carrier to generate an intermediate signal;
converting, by a fourth circuit of the first device, a Cartesian representation of the intermediate signal into a polar representation; and
controlling a local carrier generator, by the first device, with an output phase signal of the polar representation of the intermediate signal from the fourth circuit.

13. The method of claim 12 , further comprising identifying an absence of modulation of the locally-generated carrier with data.

14. The method of claim 13 , wherein converting the Cartesian representation of the aggregated broadcast carrier to a polar representation is performed responsive to identifying the absence of modulation.

15. The method of claim 13 , wherein identifying the absence of modulation of the local-generated carrier comprises identifying a modulation pause between packets.

16. The method of claim 12 , wherein converting the Cartesian representation of the aggregated broadcast carrier to the polar representation comprises performing a coordinate rotation digital computer (CORDIC) calculation.

17. The method of claim 12 , wherein removing the offset from the polar representation of the aggregated broadcast carrier to generate the intermediate signal comprises subtracting an average amplitude of the aggregated broadcast carrier from the aggregated broadcast carrier.

18. The method of claim 12 , wherein removing the offset from the polar representation of the aggregated broadcast carrier to generate the intermediate signal comprises multiplying an average amplitude of the aggregated broadcast carrier by a sampled phase of the aggregated broadcast carrier.

19. A system for carrier synchronization in near field communications, comprising:
an antenna for receiving a broadcast carrier from a remote device and transmitting a locally-generated carrier and modulated data; and
a carrier synchronization circuit for synchronizing the locally-generated carrier and broadcast carrier based on an identified phase error from a double Cartesian-to-polar mapping of a combination of the locally-generated carrier and broadcast carrier.

20. The system of claim 19 , further comprising a modulation suppression circuit for providing unmodulated carrier signals to the carrier synchronization circuit.

Assignees

• Avago Technologies General Ip

Inventors

• Frantzeskakis Manolis
• Lee Dong-U
• Jain Divyanshu
• Gan Jianhua
• Xu Shengyang

Classifications

• H04L27/0014 Primary

  Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657) · CPC title

• H04B5/45

  Transponders · CPC title

• H04B5/20

  characterised by the transmission technique; characterised by the transmission medium · CPC title

• H04L2027/0055

  single phase · CPC title

• H04L7/02 Primary

  Speed or phase control by the received code signals, the signals containing no special synchronisation information {(H04L7/0075 takes precedence)} · CPC title