COMMUNICATION DEVICES HAVING CONTROLLED IMPEDANCES

• US 20130023208A1
• Filed: 07/25/2012
• Published: 01/24/2013
• Est. Priority Date: 03/11/2005
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Innovision Research & Technology PLC (Broadcom, Inc.)
• Inventors: SYMONS, PETER
• Granted Patent: US 9,020,425 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/0723 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 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 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A NFC communications enabled device has a data store to store data, an inductive coupler to couple inductively with the magnetic field of a radio frequency signal and a signal supplier to supply a radio frequency signal to the inductive coupler. A modulator modulates a radio frequency signal in accordance with data and a demodulator extracts data from a modulated radio frequency signal inductively coupled to the coupler. A controller enables the NFC communications enabled device both to initiate near field radio frequency communication with another near field RF communicator and to respond to near field radio frequency communication initiated by another near field RF communicator. The inductive coupler has an antenna and a variable impedance element. The controller is configured to control the variable impedance element to control a magnetic field strength associated with a radio frequency signal supplied by the signal supplier.

Claims

1. A communications device, comprising:

a controlled impedance; and

a controller configured to vary the controlled impedance upon startup of the communications device to control a magnetic field strength of a magnetic field of a radio frequency signal.

2. The device of claim 1, further comprising:

an inductive coupler having an antenna coil configured and arranged in series with the controlled impedance; and

wherein the controlled impedance comprises;

an amplifier having an input coupled to a first connection of the controlled impedance and an output coupled to a second connection of the controlled impedance; and

a variable feedback element coupled between the input of the amplifier and the output of the amplifier.

3. The device of claim 2, wherein the controlled impedance further comprises:

a first capacitance coupled between the output of the amplifier and the second connection of the controlled impedance; and

a second capacitance coupled between the second connection of the controlled impedance and a ground.

4. The device of claim 2, wherein the variable feedback element comprises:

a plurality of impedances coupled to a corresponding switch from among a plurality of switches, each of the plurality of switches being controlled by the controller.

5. The device of claim 4, wherein the controller is configured to adjust a gain of the controlled impedance by controlling the plurality of switches to control the magnetic field strength of the magnetic field, the plurality of impedances being associated with active components or passive components.

6. The device of claim 1, further comprising:

a magnetic field strength controller configured to sense the magnetic field to provide a correction signal input,

wherein the controller is further configured to adjust the controlled impedance to control the magnetic field strength of the magnetic field according to the correction signal input.

7. The device of claim 6, wherein the magnetic field strength controller comprises:

a sense circuit configured to sense the magnetic field to provide a sensed magnetic field;

an error circuit configured to compare the sensed magnetic field and a reference signal to provide an error signal, the reference signal being associated with a desired magnetic field strength; and

a stabilizer circuit configured to operate upon the error signal to provide the correction input signal.

8. A communications device, comprising:

a controlled impedance; and

a controller configured to dynamically vary the controlled impedance when a protocol associated with the communications device changes to control a magnetic field strength of a magnetic field of a radio frequency signal.

9. The device of claim 8, further comprising:

an inductive coupler having an antenna coil configured and arranged in series with the controlled impedance; and

wherein the controlled impedance comprises;

an amplifier having an input coupled to a first connection of the controlled impedance and an output coupled to a second connection of the controlled impedance; and

a variable feedback element coupled between the input of the amplifier and the output of the amplifier.

10. The device of claim 9, wherein the controlled impedance further comprises:

a first capacitance coupled between the output of the amplifier and the second connection of the controlled impedance; and

a second capacitance coupled between the second connection of the controlled impedance and a ground.

11. The device of claim 9, wherein the variable feedback element comprises:

a plurality of impedances coupled to a corresponding switch from among a plurality of switches, each of the plurality of switches being controlled by the controller.

12. The device of claim 11, wherein the controller is configured to adjust a gain of the controlled impedance by controlling the plurality of switches to control the magnetic field strength of the magnetic field, the plurality of impedances being associated with active components or passive components.

13. The device of claim 8, further comprising:

a magnetic field strength controller configured to sense the magnetic field to provide a correction signal input,

wherein the controller is further configured to adjust the controlled impedance to control the magnetic field strength of the magnetic field according to the correction signal input.

14. The device of claim 13, wherein the magnetic field strength controller comprises:

a sense circuit configured to sense the magnetic field to provide a sensed magnetic field;

an error circuit configured to compare the sensed magnetic field and a reference signal to provide an error signal, the reference signal being associated with a desired magnetic field strength; and

a stabilizer circuit configured to operate upon the error signal to provide the correction input signal.

15. A method of operating a communication device, comprising:

receiving a magnetic field that is associated with a radio frequency signal; and

dynamically varying a controlled impedance to control a magnetic field strength of the magnetic field when a protocol associated with the magnetic field changes.

16. The method of claim 15, further comprising:

coupling an inductive coupler with the magnetic field to receive the magnetic field;

wherein the dynamically varying comprises;

switching a plurality of impedances to vary the controlled impedance to control the magnetic field strength.

17. The method of claim 15, further comprising:

sensing the magnetic field to provide a correction signal input, wherein the dynamically varying comprises;

dynamically varying the controlled impedance based on the correction signal input to control the magnetic field strength.

18. The method of claim 17, wherein the sensing further comprises:

comparing a signal associated with the sensed magnetic field to a reference signal associated with a desired magnetic field strength; and

providing the correction input signal based on a result of the comparing.

19. The method of claim 17, wherein the dynamically varying comprises:

varying the controlled impedance based on feedback information that is provided by sensing the magnetic field.

20. The method of claim 15, wherein the dynamically varying comprises:

dynamically varying the controlled impedance upon startup of the communication device.