Near Field Communicator Implementing Switched Circuit States for Demodulation

• US 20130189926A1
• Filed: 03/12/2013
• Published: 07/25/2013
• Est. Priority Date: 07/23/2007
• Status: Active Grant

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Innovision Limited (Broadcom, Inc.)
• Inventors: Butler, Paul, BANGS, Joakim
• Granted Patent: US 9,253,590 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

A near field RF communicator has an inductive coupler to couple inductively to an H field of an RF signal from another near field RF communicator in near field range to provide a received signal, a demodulator coupled to extract any modulation from a source signal representing a received RF signal to provide an extracted modulation signal; and a controller coupled to receive an extracted modulation signal from the demodulator. The demodulator has a sampler to sample the source signal in sampling periods and to compare signal samples with at least one of other signal samples and a clock or reference signal to remove or reject the carrier of the received RF signal and to extract the modulation.

Claims

1. A near field communications (NFC) device, comprising:

a demodulator configured to sample a signal over successive periods and to provide an output voltage proportional to a change in a voltage of the signal between the successive periods; and

a controller configured to adjust a configuration of the demodulator and to determine a modulation protocol of the signal based on the output voltage,

wherein the output voltage is a result of a capacitive charge transfer within the demodulator as the demodulator configuration is adjusted between the successive periods.

2. The NFC device of claim 1, wherein the demodulator comprises:

a voltage detector module configured to provide an output signal representative of the output voltage when the output voltage exceeds a threshold voltage.

3. The NFC device of claim 1, wherein the successive periods are different time periods.

4. The NFC device of claim 2, wherein the controller is further configured to adjust the threshold voltage based on the modulation protocol or a modulation width of the signal.

5. The NFC device of claim 1, wherein the demodulator comprises:

a sampler including a capacitor, the capacitor being configured to accumulate or discharge a charge over the successive sampling periods to provide the output voltage.

6. The NFC device of claim 1, wherein the controller is further configured to switch the demodulator configuration between a first sampling configuration, a non-sampling configuration, and a second sampling configuration, wherein a first period from among the successive periods corresponds to the first sampling configuration, and wherein a second period from among the successive periods corresponds to the second sampling configuration.

7. The NFC device of claim 2, wherein the voltage detector module is an analog-to-digital converter (ADC), and wherein the output signal is a digital signal.

8. A near field communications (NFC) device, comprising:

a demodulator configured to sample a signal in a first configuration for a first sampling period and in a second configuration for a second sampling period and to provide an output voltage proportional to a change in a voltage of the signal between the first and the second sampling periods; and

a controller configured to adjust a configuration of the demodulator and to determine a modulation protocol of the signal based on the output voltage,

wherein the output voltage is a result of a capacitive charge transfer within the demodulator as the demodulator configuration is adjusted from the first configuration to the second configuration.

9. The NFC device of claim 8, wherein the demodulator comprises:

a voltage detector module configured to provide an output signal representative of the output voltage when the output voltage exceeds a threshold voltage.

10. The NFC device of claim 8, wherein the first sampling period and the second sampling period are different time periods.

11. The NFC device of claim 9, wherein the controller is further configured to adjust the threshold voltage based on the modulation protocol or a modulation width of the signal.

12. The NFC device of claim 8, wherein the demodulator comprises:

a sampler including a capacitor, the capacitor being configured to accumulate or discharge a charge from the first configuration to the second configuration to provide the output voltage.

13. The NFC device of claim 8, wherein the controller is further configured to switch the demodulator configuration between the first configuration, a non-sampling configuration, and the second configuration.

14. The NFC device of claim 9, wherein the voltage detector module is an analog-to-digital converter (ADC), and wherein the output signal is a digital signal.

15. A near field communications (NFC) device, comprising:

a demodulator configured to;

sample a signal over successive periods to provide an output voltage proportional to a change in a voltage of the signal between the successive periods; and

provide an output signal representative of the output voltage when the output voltage exceeds a threshold voltage; and

a controller configured to adjust the demodulator configuration and to determine a modulation protocol of the signal based on the output signal,

wherein the output voltage is a result of a capacitive charge transfer within the demodulator as the demodulator configuration is adjusted between the successive periods.

16. The NFC device of claim 15, wherein the demodulator comprises:

an analog-to-digital converter (ADC) configured to provide the output signal, and wherein the output signal is a digital signal.

17. The NFC device of claim 15, wherein the successive periods are different time periods.

18. The NFC device of claim 15, wherein the controller is further configured to adjust the threshold voltage based on a modulation protocol or a modulation width of the signal.

19. The NFC device of claim 15, wherein the demodulator comprises:

a sampler including a capacitor, the capacitor being configured to accumulate or discharge a charge over the successive sampling periods to provide the output voltage.

20. The NFC device of claim 15, wherein the controller is further configured to switch the demodulator configuration between a first sampling configuration, a non-sampling configuration, and a second sampling configuration, wherein a first period from among the successive periods corresponds to the first sampling configuration, and wherein a second period from among the successive periods corresponds to the second sampling configuration.