Wireless terminals including smart antenna systems having multiple antennas

1. A wireless communication device, comprising:

a transceiver configured for communication using multiple communication modes, the transceiver comprising a transmitter and a receiver;

a plurality of antennas coupled to the transceiver, the plurality of antennas including a first antenna and a second antenna, wherein the multiple communication modes include a multiple input multiple output (“MIMO”) mode and a single antenna receive mode; and

a control circuit configured to detect selection of the single antenna receive mode as an active one of the multiple communication modes, to detect selection of the MIMO mode as the active one of the multiple communication modes, to configure at least the first antenna to transmit a signal responsive to detection of the selection of the MIMO mode, and to automatically alter a configuration of the plurality of antennas and transceiver by configuring the first antenna as a transmit only antenna and the second antenna as a receive only antenna responsive to detection of the selection of the single antenna receive mode.

2. The device of claim 1 , wherein the control circuit further comprises:

a duplexer having a first terminal that couples the first antenna to the transmitter and a second terminal that couples the first antenna to the receiver, wherein the duplexer is not coupled to the second antenna; and

a filter that couples the second antenna to the receiver, and

wherein the receiver comprises:

a first amplifier coupled to the first antenna through the second terminal of the duplexer; and

a second amplifier coupled to the second antenna through the filter.

3. The device of claim 2 , wherein the control circuit is configured to alter the configuration of the plurality of antennas by turning off the first amplifier.

4. The device of claim 2 , wherein the control circuit is configured to alter the configuration of the plurality of antennas by grounding the second terminal of the duplexer.

5. The device of claim 2 , wherein the control circuit is configured to alter the configuration of the plurality of antennas by coupling the second terminal of the duplexer to a 50 ohm terminator.

6. The device of claim 2 , wherein the first and second amplifier comprise low noise amplifiers.

7. The device of claim 2 , further comprising a processor coupled to the control circuit and the transceiver that is configured increase a transmit power of the transmitter and to select the single antenna receive mode as the active one of the multiple communication modes when the transmit power of the transmitter exceeds a selection level to increase isolation between the first and second antennas.

8. The device of claim 7 , wherein the processor is further configured to reduce the transmit power of the transmitter when the control circuit configures the first antenna as a transmit only antenna and the second antenna as a receive only antenna.

9. The device of claim 8 , wherein the processor is further configured to receive a command to enter the MIMO mode from the receiver and to select the MIMO mode as the active one of the multiple communication modes responsive to the received command to enter the MIMO mode.

10. The device of claim 9 , wherein the transceiver communicatively couples the device to a base station scheduler and wherein the command to enter the MIMO mode is received by the receiver from the base station scheduler.

11. The device of claim 10 , wherein the processor is configured to detect a received signal power level and to report the received signal power level to the base station scheduler and wherein the command to enter the MIMO mode is only received from the base station scheduler when the reported received signal power level exceeds a minimum level and wherein the processor is further configured to exit the MIMO mode responsive to receipt of a command to exit the MIMO mode from the base station scheduler and wherein the command to exit the MIMO mode is only received from the base station scheduler when the reported received signal power level does not exceed the minimum level.

12. The device of claim 11 , wherein the processor is further configured to increase the transmit power of the transmitter and to decrease the transmit power and wherein the selection level for selecting the single antenna receive mode corresponds to a received signal power level that does not exceed the minimum level so that the processor does not select the single antenna receive mode when the base station scheduler selects the MIMO mode.

13. The device of claim 1 , wherein the first antenna and the second antenna are correlated antennas having less than a 5 decibel (dB) imbalance.

14. The device of claim 1 , wherein, when in the single antenna receive mode, the device is configured to receive voice communications but not data communications.

15. The device of claim 1 , wherein, in the MIMO mode, both the first and second antennas are used as receive antennas and wherein the first antenna is not used in any of the multiple communication modes as a receive antenna when the second antenna is not also used as a receive antenna.

16. The device of claim 1 , wherein the second antenna is not coupled to the transmitter.

17. A method of operating an antenna system of a wireless communication device including a first antenna and a second antenna, the method comprising:

configuring, using a processor and/or control circuit, the first antenna and the second antenna to receive a signal responsive to detection of selection of a multiple input multiple output (“MIMO”) mode of the antenna system;

configuring at least the first antenna to transmit a signal responsive to detection of selection of the MIMO mode;

automatically configuring only the first antenna to transmit responsive to detection of selection of a single antenna receive mode of the antenna system; and automatically configuring only the second antenna to receive a signal responsive to detection of selection of the single antenna receive mode.

18. The method of claim 17 , wherein the first antenna is coupled to a receiver through an amplifier and wherein automatically configuring only the second antenna to receive a signal comprises turning off the amplifier.

19. The method of claim 17 , wherein the first antenna is coupled to a transmitter through a first terminal of a duplexer and to a receiver through a second terminal of the duplexer and wherein automatically configuring only the second antenna to receive a signal comprises grounding the second terminal of the duplexer.

20. The method of claim 17 , wherein the first antenna is coupled to a transmitter through a first terminal of a duplexer and to a receiver through a second terminal of the duplexer and wherein automatically configuring only the second antenna to receive a signal comprises coupling the second terminal of the duplexer to a 50 ohm terminator.

21. The method of claim 17 , wherein the first antenna is coupled to a transmitter through a first terminal of a duplexer and to a receiver through a second terminal of the duplexer and wherein the method further comprises selecting the single antenna receive mode when a transmit power of the transmitter exceeds a selection level to increase isolation between the first and second antennas.

22. The method of claim 21 , further comprising decreasing the transmit power of the transmitter when only the second antenna is configured to receive a signal.

23. The method of claim 17 , wherein configuring the first antenna and the second antenna is preceded by:

determining that only voice communications are requested; and

selecting the single antenna receive mode when it is determined that only voice communications are requested.

24. The method of claim 17 , wherein the method further comprises selecting the single antenna receive mode when a transmit power of a transmitter coupled to the first antenna exceeds a selection level, to increase isolation between the first and second antennas.