Wireless electronic device with antenna cycling

1. A wireless electronic device, comprising:

at least first and second antennas;

at least one radio-frequency transmitter;

switching circuitry coupled between the transmitter and the first and second antennas, wherein the switching circuitry is configured to route radio-frequency signals from the radio-frequency transmitter to a selected one of the first and second antennas;

control circuitry configured to repeatedly toggle the switching circuitry between a first configuration in which the radio-frequency signals are transmitted through the first antenna for a first fraction of a toggling cycle time period and a second configuration in which the radio-frequency signals are transmitted through the second antenna for a second fraction of the toggling cycle time period; and

an accelerometer that generates orientation data, wherein the control circuitry is further configured to adjust the first and second fractions based at least partly on orientation data from the accelerometer.

2. The wireless electronic device defined in claim 1 further comprising at least one sensor, wherein the control circuitry is further configured to adjust the first and second fractions based at least partly on data from the sensor.

3. The wireless electronic device defined in claim 2 wherein the sensor comprises a proximity sensor.

4. The wireless electronic device defined in claim 2 further comprising a housing having first and second opposing ends, wherein the first antenna is located at the first end and the second antenna is located at the second end.

5. The wireless electronic device defined in claim 1 further comprising a housing having first and second opposing ends, wherein the first antenna is located at the first end and the second antenna is located at the second end.

6. A method of operating a wireless electronic device having first and second antennas, a radio-frequency transmitter, control circuitry, and switching circuitry that selectively routes radio-frequency signals from the transmitter to the first and second antennas in response to signals from the control circuitry, comprising:

repeatedly toggling the switching circuitry between a first configuration in which the radio-frequency signals are transmitted through the first antenna for a first fraction of a toggling cycle time period and a second configuration in which the radio-frequency signals are transmitted through the second antenna for a second fraction of the toggling cycle time period; and

with the control circuitry, adjusting the first and second fractions based at least partly on antenna efficiencies of the first and second antennas.

7. The method defined in claim 6 wherein repeatedly toggling the switching circuitry comprises applying control signals to the switching circuitry from the control circuitry.

8. The method defined in claim 7 wherein the wireless electronic device includes at least one sensor, the method further comprising:

with the control circuitry, adjusting the first and second fractions based at least partly on data from the at least one sensor.

9. The method defined in claim 8 wherein the at least one sensor comprises a proximity sensor and wherein adjusting the first and second fractions comprises adjusting the first and second fractions based at least partly on proximity sensor data from the proximity sensor.

10. The method defined in claim 8 wherein the at least one sensor comprises an accelerometer and wherein adjusting the first and second fractions comprises adjusting the first and second fractions based at least partly on data from the accelerometer.

11. The method defined in claim 10 wherein the wireless electronic device has a housing with first and second opposing ends, wherein the first antenna is located at the first end and the second antenna is located at the second end, and wherein repeatedly toggling the switching circuitry comprises repeatedly toggling the switching circuitry between the first configuration so that the radio-frequency signals are transmitted through the first antenna at the first end and the second configuration so that the radio-frequency signals are transmitted through the second antenna at the second end.

12. The method defined in claim 6 wherein the wireless electronic device has a housing with first and second opposing ends, wherein the first antenna is located at the first end and the second antenna is located at the second end, and wherein repeatedly toggling the switching circuitry comprises repeatedly toggling the switching circuitry between the first configuration so that the radio-frequency signals are transmitted through the first antenna at the first end and the second configuration so that the radio-frequency signals are transmitted through the second antenna at the second end.

13. A method of transmitting radio-frequency signals with a wireless electronic device having at least first and second antennas, comprising:

during each of a plurality of repeating cycles each of which has an associated cycle time period, transmitting radio-frequency signals for a first fraction of the cycle time period using the first antenna and transmitting radio-frequency signals for a second fraction of the cycle time period using the second antenna;

determining whether the first antenna is closer to an external object than a second antenna; and

in response to determining that the first antenna is closer to the external object than the second antenna, reducing the first fraction of the cycle time period and increasing the second fraction of the cycle time period.

14. The method defined in claim 13 further comprising:

while transmitting the radio-frequency signals using the first and second antennas, adjusting the first and second fractions of the cycle time period based on data from a sensor within the wireless electronic device.

15. The method defined in claim 14 wherein the sensor comprises a proximity sensor and wherein adjusting the first and second fractions comprises adjusting the first and second fractions based on data from the proximity sensor.

16. The method defined in claim 14 wherein the sensor comprises an accelerometer and wherein adjusting the first and second fractions comprises adjusting the first and second fractions based on data from the accelerometer.

17. The method defined in claim 13 wherein the wireless electronic device comprises transmitter circuitry and switching circuitry that routes radio-frequency signals from the transmitter circuitry to the first and second antennas and wherein transmitting the radio-frequency signals for the first fraction of the cycle time period using the first antenna and transmitting the radio-frequency signals for the second fraction of the cycle time period using the second antenna comprises controlling the switching circuitry.

18. The method defined in claim 13 wherein the wireless electronic device has a housing with first and second opposing ends, wherein the first antenna is located at the first end and the second antenna is located at the second end, wherein transmitting the radio-frequency signals with the first antenna comprises transmitting the radio-frequency signals with the first antenna at the first end, and wherein transmitting the radio-frequency signals with the second antenna comprises transmitting the radio-frequency signals with the second antenna at the second end.

19. The method defined in claim 13 wherein the radio-frequency signals are transmitted with an average power, the method further comprising:

adjusting the first and second fractions while maintaining the average power of the radio-frequency signals.

20. The method defined in claim 13 further comprising:

adjusting the first and second fractions based on signal strength of wireless signals received from a base station.