Apparatus and methods for synchronization of transmitters

1. A first-transceiver for use in an antenna diversity scheme, the first-transceiver comprising:

a first-time/clock-generation-unit;

a first-receiver, configured to receive a wireless second-alignment-signal from a second-transceiver with a second-time/clock-generation-unit, wherein the wireless second-alignment-signal is representative of a state of the second-time/clock-generation-unit; and

a first-transmitter;

wherein:

the first-transceiver is configured to set the first-time/clock-generation-unit, based on the wireless second-alignment-signal, to reduce an alignment-error between the first-time/clock-generation-unit and the second-time/clock-generation-unit;

a frequency synthesizer in the first-time/clock-generation-unit is configured to provide, based on a clock-source signal from an oscillator, a carrier frequency to tuners of the transmitter and the receiver, a sampling frequency to a DAC of the transmitter and an ADC of the receiver, and a system timer frequency to a system timer; the first-transmitter is configured to transmit a wireless first-transmission-signal, in accordance with the first-time/clock-generation-unit, as part of the antenna diversity scheme, wherein:

the first-transmission-signal corresponds to a second-transmission-signal that is transmitted by the second-transceiver; and

the antenna diversity scheme comprises aligned transmission of both the first-transmission-signal and the second-transmission-signal.

2. The first-transceiver of claim 1 , wherein the first-transmitter is configured to transmit a wireless first-alignment-signal, representative of a state of the first-time/clock-generation-unit, for reducing an alignment-error between the second-time/clock-generation-unit and the first-time/clock-generation-unit.

3. The first-transceiver of claim 1 , wherein the first-transceiver is configured to set the first-time/clock-generation-unit by adjusting a time of the first-time/clock-generation-unit and/or a frequency of the first-time/clock-generation-unit.

4. The first-transceiver of claim 3 , wherein the first-time/clock-generation-unit comprises the frequency synthesizer and the system timer, and wherein the first-transceiver is configured to set the first-time/clock-generation-unit by one or more of:

applying an offset to a count of the system timer;

applying a frequency offset to one or more of:

the carrier frequency that is provided to the tuners of the transmitter and the receiver,

the sampling frequency that is provided to the DAC of the transmitter and the ADC of the receiver,

the system timer frequency that is provided to the system timer;

tuning a crystal oscillator that is associated with the frequency synthesizer;

changing divider settings of a phase locked loop that is associated with the frequency synthesizer;

digitally rotating digital samples for compensating an RF carrier frequency offset; and

resampling of a digital signal for compensating a difference in DA converter frequency.

5. The first-transceiver of claim 1 , wherein the aligned transmission comprises transmission of both the first-transmission-signal and the second-transmission-signal aligned with respect to time and/or frequency such that they constructively combine when received at a remote receiver.

6. The first-transceiver of claim 1 , wherein the wireless second-alignment-signal comprises a prefix and/or a postfix portion of an earlier-second-transmission-signal, and wherein the earlier-second-transmission-signal is transmitted before the second-transmission-signal.

7. The first-transceiver of claim 6 , further comprising a controller configured to determine an alignment-error associated with the first-transceiver; and

if the alignment error is greater than a predetermined threshold, then the first-transceiver is configured to set the first-time/clock-generation-unit based on the wireless second-alignment-signal.

8. The first-transceiver of claim 1 , further configured to:

receive a plurality of wireless alignment-signals, including the wireless second-alignment-signal, from a plurality of other transceivers, including the second-transceiver; and

set the first-time/clock-generation-unit, based on the plurality of wireless alignment-signals, to reduce alignment-errors between the first-time/clock-generation-unit and a plurality of time/clock-generation-units of the other transceivers.

9. The first-transceiver of claim 1 , wherein the first-transmission-signal corresponds to the second-transmission-signal as both the first-transmission-signal and the second-transmission-signal comprise corresponding representations of an information-signal.

10. The first-transceiver of claim 1 , wherein the wireless second-alignment-signal is a wireless Radio Frequency signal.

11. A multi-transceiver system comprising:

a first-transceiver comprising:

a first-time/clock-generation-unit;

a first-receiver, configured to receive a wireless second-alignment-signal from a second-transceiver with a second-time/clock-generation-unit, wherein the wireless second-alignment-signal is representative of a state of the second-time/clock-generation-unit; and

a first-transmitter;

wherein:

the first-transceiver is configured to set the first-time/clock-generation-unit, based on the wireless second-alignment-signal, to reduce an alignment-error between the first-time/clock-generation-unit and the second-time/clock-generation-unit;

a frequency synthesizer in the first-time/clock-generation-unit is configured to provide, based on a clock-source signal from an oscillator, a carrier frequency to tuners of the transmitter and the receiver, a sampling frequency to a DAC of the transmitter and an ADC of the receiver, and a system timer frequency to a system timer; the first-transmitter is configured to transmit a wireless first-transmission-signal, in accordance with the first-time/clock-generation-unit, as part of the antenna diversity scheme, wherein:

the first-transmission-signal corresponds to a second-transmission-signal that is transmitted by the second-transceiver; and

the antenna diversity scheme comprises aligned transmission of both the first-transmission-signal and the second-transmission-signal,

the second-transceiver, and

a digital communication channel configured to exchange coordination-signalling between the first-transceiver and the second-transceiver to co-ordinate setting the first-time/clock-generation-unit and/or the second time/clock-generation-unit.

12. The multi-transceiver system of claim 11 , wherein the coordination-signalling comprises one or more of:

a time-of-transmission of the second-alignment-signal;

a value of the second-time/clock-generation-unit at a predefined moment in time relative to the time-of-transmission of the second-alignment-signal;

a value of the second-time/clock-generation-unit at a time-of-transmission of the second-alignment-signal;

a delay between the time-of-transmission and the time-of-reception of the second-alignment-signal;

an expected time of arrival of the wireless second-alignment-signal at the first-transceiver; and/or

an expected time of arrival of the wireless first-alignment-signal at the second-transceiver.

13. The multi-transceiver system of claim 11 , wherein the digital communication channel is connected between:

(i) a timing-controller; and

(ii) the first-transceiver and the second-transceiver,

wherein the timing-controller is configured to provide the coordination-signalling to the first-transceiver and/or the second-transceiver to coordinate setting the first-time/clock-generation-unit and/or the second-time/clock-generation-unit.

14. The multi-transceiver system of claim 11 , wherein the first-transceiver is spaced apart from the second-transceiver.

15. A method of operating a first-transceiver for use in an antenna diversity scheme, the method comprising:

receiving a wireless second-alignment-signal from a second-transceiver with a second-time/clock-generation-unit, wherein the wireless second-alignment-signal is representative of a state of the second-time/clock-generation-unit; and

setting the first-time/clock-generation-unit, based on the wireless second-alignment-signal, to reduce an alignment-error between the first-time/clock-generation-unit and the second-time/clock-generation-unit;

using a frequency synthesizer in the first-time/clock-generation-unit to provide, based on a clock-source signal from an oscillator, a carrier frequency to tuners of a transmitter and a receiver, a sampling frequency to a DAC of the transmitter and an ADC of the receiver, and a system timer frequency to a system timer;

transmitting a wireless first-transmission-signal, in accordance with the first-time/clock-generation-unit, as part of the antenna diversity scheme, wherein:

the first-transmission-signal corresponds to a second-transmission-signal that is transmitted by the second-transceiver; and

the antenna diversity scheme comprises aligned transmission of both the first-transmission-signal and the second-transmission-signal.

16. The method of claim 15 , further comprising transmitting a wireless first-alignment-signal representative of a state of the first-time/clock-generation-unit for reducing an alignment-error between the second-time/clock-generation-unit and the first-time/clock-generation-unit.

17. The method of claim 15 , further comprising setting the first-time/clock-generation-unit by adjusting a time of the first-time/clock-generation-unit and/or a frequency of the first-time/clock-generation-unit.

18. The method of claim 15 , further comprising transmitting both the first-transmission-signal and the second-transmission-signal aligned with respect to time and/or frequency such that they constructively combine when received at a remote receiver.

19. The method of claim 15 , further comprising:

determining an alignment-error associated with the first-transceiver, and

setting the first-time/clock-generation-unit based on the wireless second-alignment-signal if the alignment error is greater than a predetermined threshold.

20. The method of claim 15 , wherein the wireless second-alignment-signal is a wireless Radio Frequency signal.