Envelope tracker driven transmit beamforming

1. A method comprising:

in a wireless communication device comprising a receiver, a transmitter, a plurality of power amplifiers coupled to a plurality of antennas and at least one envelope tracking power supply,

simultaneously transmitting respective signals from two or more respective power amplifiers of the plurality of power amplifiers, the two or more power amplifiers powered by a common envelope tracking power supply, the respective signals transmitted phase shifted relative to one another so as to be received coherently at an intended receiver; and

wherein a ratio of a first envelope of a first amplified transmit signal from a first respective power amplifier to a second envelope of a second amplified transmit signal from a second respective power amplifier is constant over a transmission from the wireless communication device.

2. The method of claim 1 wherein simultaneously transmitting comprises:

transmitting from a first power amplifier a first signal; and

transmitting from a second power amplifier a second signal,

wherein the second signal is shifted in phase relative to the first signal.

3. A method comprising:

at a telecommunication device,

operating the telecommunication device to receive signals from a remote radio and determine a phase difference of signals received from the remote radio;

operating the telecommunication device to transmit output signals in a time division duplexing mode of operation, including

generating a transmit signal;

modifying characteristics of the generated transmit signal in at least one signal path of the telecommunication device to produce two or more modified signals, including using information from received signals to phase shift the two or more modified signals relative to one another so they are received coherently at an intended receiver;

amplifying the generated transmit signal and the two or more modified signals in a plurality of respective power amplifiers for transmission from a plurality of respective antennas, wherein a ratio of a first envelope of a first generated transmit signal from a first respective power amplifier to a second envelope of a second generated transmit signal from a second respective power amplifier is constant over a transmission from the telecommunication device;

in response to an envelope of the generated transmit signal, in a single envelope tracking power supply, generating a switched power amplifier voltage supply signal; and

applying the switched power amplifier voltage supply signal to the respective power amplifiers of the plurality of respective power amplifiers.

4. The method of claim 3 wherein producing two or more signals which are phase shifted comprises applying a constant phase shift to the two or more signals over a transmit band of frequencies.

5. The method of claim 3 further comprising:

estimating a phase difference of signals received from the remote radio at a plurality of antennas of the telecommunication device; and

transmitting as the output signals two signals that are shifted in phase relative to one another in response to the estimated phase difference.

6. The method of claim 3 further comprising:

receiving a signal from a remote radio;

detecting a phase shift message in the received signal; and

transmitting as the output signals two signals that are shifted in phase relative to one another using a phase difference communicated by the phase shift message.

7. The method of claim 3 further comprising:

determining a receive path phase difference of a plurality of receive paths of the telecommunication device;

determining a transmit path phase difference of a plurality of transmit paths of the telecommunication device; and

calibrating at least one of the receive path phase difference and the transmit path phase difference.

8. The method of claim 7 further comprising:

transmitting as the output signals two signals that are shifted in phase relative to one another using a phase difference determined using the calibration.

9. The method of claim 7 wherein transmitting the two signals comprises:

transmitting a first signal and a second signal with the respective power amplifiers of the telecommunication device, the second signal shifted relative to the first signal by the transmit path phase difference or the receive path phase difference.

10. The method of claim 7 wherein transmitting the two signals comprises:

transmitting a first signal and a second signal with the respective power amplifiers of the telecommunication device, the second signal shifted relative to the first signal by a difference between the transmit path phase difference and the receive path phase difference.

11. The method of claim 3 further comprising:

determining a first phase difference between a receive path and a transmit path of the telecommunication device on a first antenna;

determining a second phase difference between a receive path and a transmit path of the telecommunication device on a second antenna;

determining a difference between the first phase difference and the second phase difference; and

using the difference, adjusting phase of at least one of the transmit path on the first antenna and the transmit path on the second antenna.

12. A method comprising:

at a telecommunication device,

generating a transmit signal;

modifying characteristics of the generated transmit signal in at least one signal path of the telecommunication device to produce one or more modified signals;

amplifying the generated transmit signal and the one or more modified signals in a plurality of respective power amplifiers for transmission from a plurality of respective antennas;

in response to an envelope of the generated transmit signal, in a single envelope tracking power supply, generating a switched power amplifier voltage supply signal; and

applying the switched power amplifier voltage supply signal to the respective power amplifiers of the plurality of respective power amplifiers,

wherein a ratio of a first envelope of a first amplified transmit signal from a first respective power amplifier to a second envelope of a second amplified transmit signal from a second respective power amplifier is constant over a transmission from the telecommunication device.

13. A method comprising:

at a telecommunication device,

transmitting two respective transmitted signals from two respective power amplifiers of the telecommunication device, wherein each respective power amplifier is driven by a respective envelope tracking switching power supply, each respective envelope tracking switching power supply being driven by a common envelope tracking reference signal, the two respective transmitted signals being phase shifted relative to one another so as to be received coherently at an intended receiver; and

wherein a ratio of a first envelope of a first signal of the two respective transmitted signals to a second envelope of a second signal the two respective transmitted signals is substantially constant over a transmission from the telecommunication device.

14. The method of claim 13 wherein the respective envelope tracking switching power supplies are driven by one or more envelope tracking reference signals.

15. The method of claim 13 further comprising:

converting a common digital envelope tracking signal to respective envelope tracking reference signals for driving the each respective envelope tracking switching power supply.

16. The method of claim 13 wherein the respective envelope tracking switching power supplies are driven a common envelope tracking reference signal.

17. A telecommunication device comprising:

a first transmit circuit including a first power amplifier driving a first antenna, wherein the first transmit circuit is operative to transmit a first signal to a remote radio;

a second transmit circuit including a second power amplifier driving a second antenna, wherein the second transmit circuit is operative to transmit a second signal to the remote radio; and

an envelope tracking circuit including one or more envelope tracking power supplies producing a switched power amplifier voltage supply signal, the switched power amplifier voltage supply signal being provided to the first power amplifier to power the first power amplifier and being provided to the second power amplifier to power the second power amplifier; and

wherein a ratio of a first envelope of the first signal to a second envelope of the second signal is substantially constant over a transmission from the telecommunication device.

18. The telecommunication device of claim 17 wherein the telecommunication device further comprises:

a calibration generator operative to determine a phase difference between the first transmit circuit and the second transmit circuit and determine a constant phase difference to be maintained between the first signal and the second signal to ensure coherent reception of the first signal and the second signal at the remote radio.