Mobile wireless communications device with NFC coupling circuit and related methods

1. A wireless communications device comprising:

a wireless transceiver;

a processor coupled to said wireless transceiver;

a near field communication (NFC) circuit coupled to said processor;

an NFC antenna; and

a coupling circuit between said NFC circuit and said NFC antenna comprising

a capacitive network comprising a plurality of capacitors coupled in series with each other and in parallel with said NFC antenna,

a transmit branch coupled between said NFC circuit and a first node between a first pair of capacitors of said plurality thereof, and

a receive branch coupled between said NFC circuit and the first node between the first pair of capacitors of said plurality thereof.

2. The wireless communications device of claim 1 wherein said coupling circuit further comprises at least one tuning branch coupled between said NFC circuit and a second node between a second pair of capacitors of said plurality thereof.

3. The wireless communications device of claim 2 wherein said at least one tuning branch comprises a pair thereof.

4. The wireless communications device of claim 3 wherein said pair of tuning branches comprises a first tuning branch comprising a first capacitor, and a second tuning branch comprising a second capacitor, and a diode coupled thereto.

5. The wireless communications device of claim 1 wherein said transmit branch comprises an inductor and a capacitor coupled thereto.

6. The wireless communications device of claim 5 wherein said transmit branch further comprises another capacitor coupled at a node between said inductor and said capacitor and a voltage reference.

7. The wireless communications device of claim 1 wherein said receive branch comprises a resistor and a capacitor coupled thereto.

8. The wireless communications device of claim 1 wherein said NFC circuit is configured to cooperate with said processor to operate in an IC card emulation mode or a reader/writer mode.

9. The wireless communications device of claim 1 wherein said wireless transceiver comprises a cellular transceiver.

10. A wireless communications device comprising:

a wireless transceiver;

a processor coupled to said wireless transceiver;

a near field communication (NFC) circuit coupled to said processor, said NFC circuit configured to cooperate with said processor for operation in an IC card emulation mode or a reader/writer mode;

an NFC antenna; and

a coupling circuit between said NFC circuit and said NFC antenna comprising

a capacitive network comprising a plurality of capacitors coupled in series with each other and in parallel with said NFC antenna,

a transmit branch coupled between said NFC circuit and a first node between a first pair of capacitors of said plurality thereof,

a receive branch coupled between said NFC circuit and the first node between the first pair of capacitors of said plurality thereof, and

at least one tuning branch coupled between said NFC circuit and a second node between a second pair of capacitors of said plurality thereof.

11. The wireless communications device of claim 10 wherein said at least one tuning branch comprises a pair thereof.

12. The wireless communications device of claim 11 wherein said pair of tuning branches comprises a first tuning branch comprising a first capacitor, and a second tuning branch comprising a second capacitor, and a diode coupled thereto.

13. The wireless communications device of claim 10 wherein said transmit branch comprises an inductor and a capacitor coupled thereto.

14. The wireless communications device of claim 13 wherein said transmit branch further comprises another capacitor coupled at a node between said inductor and said capacitor and a voltage reference.

15. The wireless communications device of claim 10 wherein said receive branch comprises a resistor and a capacitor coupled thereto.

16. The wireless communications device of claim 10 wherein said wireless transceiver comprises a cellular transceiver.

17. A method for making a mobile wireless communications device comprising a wireless transceiver, a processor coupled to the wireless transceiver, a near field communication (NFC) circuit coupled to the processor, and an NFC antenna, the method comprising:

coupling the NFC circuit and the NFC antenna together with a coupling circuit comprising

a capacitive network comprising a plurality of capacitors coupled in series with each other and in parallel with the NFC antenna,

a transmit branch coupled between the NFC circuit and a first node between a first pair of capacitors of the plurality thereof, and

a receive branch coupled between the NFC circuit and the first node between the first pair of capacitors of the plurality thereof.

18. The method of claim 17 wherein the coupling circuit further comprises at least one tuning branch coupled between the NFC circuit and a second node between a second pair of capacitors of the plurality thereof.

19. The method of claim 18 wherein the at least one tuning branch comprises a pair thereof.

20. The method of claim 19 wherein the pair of tuning branches comprises a first tuning branch comprising a first capacitor, and a second tuning branch comprising a second capacitor, and a diode coupled thereto.

21. The method of claim 17 wherein the transmit branch comprises an inductor and a capacitor coupled thereto.

22. The method of claim 21 wherein the transmit branch further comprises another capacitor coupled at a node between the inductor and the capacitor and a voltage reference.