NFC device with PLL controlled active load modulation

• US 8,934,836 B2
• Filed: 06/28/2012
• Issued: 01/13/2015
• Est. Priority Date: 06/28/2012
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Lefley, Alastair
• Primary Examiner(s): Trinh, Sonny
• Application Number:
  US13/535,874
• Publication Number:
  US 20140003548A1
• Time in Patent Office: 929 Days
• Field of Search: 455/41.1, 455/41.2, 455/180.3, 375/256, 178/43, 340/10.1
• US Class Current: 455/41.1
• CPC Class Codes: G06K 19/0727 the arrangement being a circuit facilitating integration of the record carrier with a hand-held device such as a smart phone of PDA
• CPC Class Codes: G06K 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H04B 5/24 Inductive coupling

Abstract

A wireless communication device for communicating in the near-field via active load modulation. The device including an antenna configured to receive a magnetic field, a recovery device configured to recover a clock from the magnetic field, and a multiplexer configured to receive the recovered clock and a reference clock, and to output one of the recovered clock and the reference clock based on a current operational state of the wireless communication device, The wireless communication device further including a shunt regulator configured to produce the active load modulation by modulating an impedance of the wireless communication device, a phase-locked loop (PLL) configured to receive one of the recovered clock and the reference clock and to utilize the received clock to control the active load modulation, and a driver configured to contribute to the active load modulation by adjusting an amplitude of a voltage across the antenna.

Claims

1. A wireless communication device, comprising:

an antenna configured to receive a magnetic field;

a recovery device configured to recover a clock from the magnetic field;

a multiplexer configured to receive the recovered clock and a reference clock, and to output one of the recovered clock and the reference clock based on a current operational state of the wireless communication device;

a shunt regulator configured to produce an active load modulation by actively modulating an impedance of the wireless communication device;

a phase-locked loop (PLL) configured to receive one of the recovered clock and the reference clock and to utilize the received clock to control the active load modulation; and

a driver configured to contribute to the active load modulation by adjusting an amplitude of a voltage across the antenna.

2. The wireless communication device of claim 1, wherein the wireless communication device is a target near field communication (NFC) device.

3. The wireless communication device of claim 1, wherein the shunt regulator is further configured to vary a resistance based on a load associated with the antenna.

4. The wireless communication device of claim 3, wherein the shunt regulator is further configured to increase the load using a feedback mechanism to maintain a safe voltage level on the antenna.

5. The wireless communication device of claim 1, wherein the multiplexer is configured to output the recovered clock when the current operational state of the wireless communication device is that of a target.

6. The wireless communication device of claim 1, wherein the multiplexer is configured to output the reference clock when the current operational state of the wireless communication device is that of an initiator.

7. The wireless communication device of claim 1, wherein the PLL is further configured to transition between a locked state and a memory mode between a transmission and receipt of information packets.

8. The wireless communication device of claim 7, wherein the PLL is functioning in the memory mode during transmission of the active load modulation, and is functioning in the locked state at all other times.

9. The wireless communication device of claim 1, wherein the wireless communication device is a target radio frequency identification (RFID) device.

10. A wireless communication system, comprising:

a first wireless communication device, having initiator circuitry, configured to drive a first antenna to create a first magnetic field; and

a second wireless communication device, having target circuitry, configured to receive the first magnetic field at a second antenna, to recover a clock from the first magnetic field, to perform active load modulation based on the recovered clock, and to drive the second antenna to create a second magnetic field based on the active load modulation,

wherein the target circuitry comprises a multiplexer configured to output one of the recovered clock and a reference clock based on a current operational state of the second wireless communication device, and

wherein the first wireless communication device is further configured to receive the second magnetic field and to demodulate the second magnetic field using a demodulation technique.

11. The wireless communication system of claim 10, wherein the initiator circuitry comprises:

a demodulator configured to demodulate the second magnetic field;

a first phase-locked loop (PLL) configured to synthesize a sine wave; and

a first driver configured to drive the synthesized sine wave on the first antenna to create the first magnetic field,

and wherein the target circuitry comprises;

a recovery device configured to recover the clock from the second magnetic field;

a shunt regulator configured to produce the active load modulation by actively modulating an impedance of the second wireless communication device;

a second PLL configured to receive one of the recovered clock and the reference clock and to utilize the received clock to control the active load modulation; and

a second driver configured to contribute to the active load modulation by adjusting an amplitude of a voltage across the second antenna.

12. The wireless communication system of claim 11, wherein the first wireless communication device is configured to create the first magnetic field by adjusting a voltage of the sine wave.

13. The wireless communication system of claim 10, where the first wireless communication device and the second wireless communication device form a transformer.

14. The wireless communication system of claim 10, wherein the first wireless communication device is configured to demodulate the second magnetic field using current sensing functionality.

15. The wireless communication system of claim 10, wherein the first wireless communication device and the second wireless communication device are configured to communicate using active load modulation in the presence of both a high magnetic field and a low magnetic field.

16. The wireless communication system of claim 10, wherein the first wireless communication device and the second wireless communication device have poor magnetic coupling.

17. A method of performing active load modulation:

receiving a magnetic field at a wireless communication device;

recovering a clock from the magnetic field;

inputting one of the recovered clock and a reference clock to a phase-locked loop (PLL), located within the wireless communication device, based on an operational state of the wireless communication device;

placing the PLL into one of a locked state and a memory mode based on the operational state of the wireless communication device;

adjusting at least one characteristic of a voltage vector produced by the wireless communication device;

creating a modulated magnetic field based on the adjusted voltage vector; and

contributing to a drive of the modulated magnetic field.

18. The method of claim 17, wherein placing the PLL into one of a locked state and a memory mode comprises:

placing the PLL in the memory mode, by open circuiting the PLL, during a transmission of the modulated magnetic field; and

placing the PLL in the locked state at other times, such that the PLL locks to the recovered clock,

wherein the PLL is configured to remember a phase and frequency of the recovered clock while in the memory mode.

19. The method of claim 17, further comprising loading an antenna, located on the wireless communication device, through a feedback mechanism to maintain a safe voltage level across the antenna, wherein the loading is performed when the magnetic field is high.

20. The method of claim 17, further comprising:

transmitting the modulated magnetic field from the wireless communication device to a second wireless communication device; and

demodulating the modulated magnetic field using current sensing functionality within the second wireless communication device.