Smartphone proximity card emulation

1. A portable computing device, comprising:

an antenna;

storage that stores an identification number; and

a processor configured to control modulation of the identification number onto an unmodulated carrier signal received by the antenna from a proximity card reader device to enable the portable computing device to emulate a proximity card;

wherein the portable computing device is configured to emulate a proximity card by responding to the proximity card reader device in a first mode using the antenna, and to receive a wireless charging signal from a wireless charger using the antenna to charge a rechargeable battery in a second mode, the processor enabling the identification number to be modulated onto the unmodulated carrier signal for a predetermined time duration, and causing the portable computing device to enter the second mode after expiration of the predetermined time duration to wirelessly charge the rechargeable battery.

2. The portable computing device of claim 1 , wherein the portable computing device is a smartphone.

3. The portable computing device of claim 1 , wherein the antenna is configured for a kilohertz frequency range.

4. The portable computing device of claim 1 , further comprising:

a carrier detection module configured to determine whether a received signal is a wireless signal transmitted by the wireless charger or is the carrier signal received from the proximity card reader device; and

the carrier detection module provides an indication of the carrier signal to the processor when the wireless signal is determined to be transmitted by the proximity card reader device.

5. The portable computing device of claim 4 , wherein the carrier detection module is configured to measure an amplitude of the wireless signal, to determine the wireless signal to be transmitted by the wireless charger if the measured amplitude is greater than a predetermined threshold value, and to determine the wireless signal to be the carrier signal received from the proximity card reader device if the measured amplitude is less than the predetermined threshold value.

6. The portable computing device of claim 4 , wherein the carrier detection module is configured to determine the wireless signal to be transmitted by the wireless charger if the wireless signal includes a wireless power transfer communication.

7. The portable computing device of claim 4 , wherein the processor receives the carrier signal indication on a general purpose input-output port.

8. The portable computing device of claim 1 , further comprising:

a modulation circuit coupled between the processor and the antenna;

the processor configured to retrieve the identification number from the storage and to provide the identification number to the modulation circuit according to a predetermined timing; and

the modulation circuit configured to modulate the identification number onto the carrier signal at the antenna according to the predetermined timing.

9. The portable computing device of claim 8 , wherein the predetermined timing is configured to synchronize bits of the identification number with a frequency of the carrier signal.

10. The portable computing device of claim 8 , wherein the processor transmits the identification number to the modulation circuit from a serial port.

11. The portable computing device of claim 1 , further comprising:

a wireless charging controller coupled to the antenna to enable a rechargeable battery of the portable computing device to be wirelessly charged by a wireless charging signal received by the antenna;

the processor configured to disable wireless charging of the rechargeable battery when the identification number is being modulated onto the carrier signal; and

the processor configured to enable wireless charging of the rechargeable battery when the identification number is not being modulated onto the carrier signal.

12. A method in a portable computing device, comprising:

operating in a first mode to emulate a proximity card, including

receiving an unmodulated carrier signal transmitted by a proximity card reader device at an antenna of the portable computing device,

accessing an identification number stored in storage of the portable computing device, and

modulating the identification number onto the unmodulated carrier signal for a predetermined time duration to enable the portable computing device to emulate a proximity card; and

operating in a second mode for wireless charging after expiration of the predetermined time duration, including

receiving a wireless charging signal from a wireless charger using the antenna, and

charging a rechargeable battery of the portable computing device with the charge from the wireless charging signal.

13. The method of claim 12 , further comprising:

disabling wireless charging capability associated with the antenna to operate in the first mode;

performing said modulating of the identification number onto the carrier signal; and

enabling wireless charging capability associated with the antenna to operate in the second mode.

14. The method of claim 13 , further comprising:

determining whether a received wireless signal is transmitted by a wireless charger or is the carrier signal received from the proximity card reader device; and

when the wireless signal is determined to be the carrier signal received from the proximity card reader device,

performing said disabling of wireless charging capability associated with the antenna to operate in the first mode, and

performing said modulating of the identification number onto the carrier signal.

15. The method of claim 14 , wherein said determining whether a received wireless signal is transmitted by a wireless charger or is the carrier signal received from the proximity card reader device comprises:

measuring an amplitude of the wireless signal;

determining the wireless signal to be transmitted by the wireless charger if the measured amplitude is greater than a predetermined threshold value; and

determining the wireless signal to be the carrier signal received from the proximity card reader device if the measured amplitude is less than the predetermined threshold value.

16. The method of claim 13 , wherein said determining whether a received wireless signal is transmitted by a wireless charger or is the carrier signal received from the proximity card reader device comprises:

determining whether the wireless signal includes a wireless power transfer communication.

17. The method of claim 12 , wherein the portable computing device is a smartphone.

18. The method of claim 12 , wherein the antenna is configured for a kilohertz frequency range.

19. A computer readable storage medium having computer program instructions stored in the computer readable storage medium that enable a processor to perform a method in a portable computing device, the method comprising:

accessing an identification number stored in storage of the portable computing device;

receiving an indication of an unmodulated carrier signal received at an antenna of the portable computing device from a proximity card reader device;

disabling wireless charging capability associated with the antenna to operate in a first mode;

providing the identification number to a modulation circuit of the portable computing device according to predetermined timing for a predetermined time duration to modulate the identification number onto the unmodulated carrier signal by the antenna to enable the portable computing device to emulate a proximity card; and

enabling wireless charging capability associated with the antenna to operate in a second mode after expiration of the predetermined time duration.

20. The computer readable storage medium of claim 19 , wherein the portable computing device is a smartphone.