Time and amplitude alignment in envelope tracking amplification stage

1. A method of calibrating an envelope path and an input path of an amplification stage including an envelope tracking power supply, the method comprising:

generating input signals having a known relationship for each of the input and envelope paths;

amplifying the signal in the input path with an amplifier powered by the envelope tracking power supply to generate a signal at an output of the amplification stage;

detecting the power in the signal at the output of the amplification stage; and

varying an amplitude and a delay of the signal in one of the envelope and input paths in order to reduce the variation in the power detected in the signal at the output of the amplification stage.

2. The method of claim 1 further comprising varying the delay in the one path to determine the delay minimising the variation in detected power and varying the amplitude in the one path to determine the amplitude minimising the variation in detected power.

3. The method of claim 2 further comprising varying the amplitude with the delay set at that determined to minimise variation in detected power or varying the delay with the amplitude set at that determined to minimise variation in detected power.

4. The method of claim 2 further comprising repeating each determination.

5. A method of calibrating an envelope path and an input path of an amplification stage including an envelope tracking power supply, the method comprising:

generating input signals having a known relationship for each of the input and envelope paths;

varying an amplitude and a delay of the signal in one of the envelope and input paths in order to reduce the variation in the power detected in a signal at the output of the amplification stage;

varying one of the relative delay or relative amplitude between the paths over a plurality of values;

detecting the power at the output of the amplification stage for each value;

determining the value of the relative delay or relative amplitude which generates the minimum detected output power variation;

applying the determined value;

varying the other of the relative delay or relative amplitude between the paths over a plurality of values;

detecting the power at the output of the amplification stage for each value; and

determining the value of the other of the relative delay or relative amplitude which generates the minimum detected output power variation.

6. The method of claim 5 wherein varying each of the relative delay and the relative amplitude comprises varying the delay and amplitude of the signal in one path whilst applying no variation to the signal in the other path.

7. The method of claim 1 in which the generated input signals for the input and envelope paths are correlated.

8. The method of claim 1 further comprising applying a sinusoidal signal to each of the envelope and input paths, wherein the applied signals in each path are 180° out of phase with each other.

9. The method of claim 1 in which the amplification stage is an RF amplification stage.

10. The method of claim 1 further comprising:

determining the delay and amplitude variations in the one path minimising the variation in the detected output power; and

setting the delay and amplitude variations in the one path corresponding to such.

11. An amplification stage having an input path and an envelope path, the amplification stage comprising:

a signal generator arranged to generate a signal on each of the input and envelope paths, the signals having a known relationship;

an envelope tracking power supply;

an amplifier powered by the envelope tracking power supply and configured to amplify the signal in the input path to generate a signal at the output of the amplifier; and

a detector for detecting the power in the signal at the output of the amplifier, the signal generator being adapted to vary the delay and amplitude of the signal in one of the envelope and input paths in order to reduce the variation in the power detected in the signal at the output.

12. The amplification stage of claim 11 wherein the signal generator is adapted to vary the delay and the amplitude in separate stages of operation.

13. The amplification stage of claim 11 further including a measurement block for measuring the power variation of the output signal.

14. An amplification stage including an amplifier and an envelope tracking power supply, and having an input path and an envelope path, the amplification stage comprising:

a signal generator arranged to generate a signal on each of the input and envelope paths having a known relationship;

a detector for detecting the power in a signal at the output of the amplifier, the signal generator being adapted to vary the delay and amplitude of the signal in one of the envelope and input paths in order to reduce the variation in the power detected in the signal at the output; and

a measurement block for measuring the power variation of the output signal, wherein the signal generator is adapted to generate the signal on one of the input or envelope paths for a plurality of delay values, and the measurement block is adapted to measure the output power variation for each delay value, the measurement block being further adapted to determine the delay value associated with the minimum detected power variation.

15. The amplification stage of claim 14 in which the measurement block is further adapted to apply the determined delay value.

16. An amplification stage including an amplifier and an envelope tracking power supply, and having an input path and an envelope path, the amplification stage comprising:

a signal generator arranged to generate a signal on each of the input and envelope paths having a known relationship;

a detector for detecting the power in a signal at the output of the amplifier, the signal generator being adapted to vary the delay and amplitude of the signal in one of the envelope and input paths in order to reduce the variation in the power detected in the signal at the output; and

a measurement block for measuring the power variation of the output signal, wherein the signal generator is adapted to generate the signal on one of the input or envelope paths for a plurality of amplitude values, and the measurement block is adapted to measure the output variation for each amplitude value, the measurement block being further adapted to determine the amplitude value associated with the minimum detected power variation.

17. The amplification stage of claim 16 in which the measurement block is further adapted to apply the determined amplitude value.

18. The amplification stage of claim 11 wherein the signal generator is arranged to generate the signal on each of the input and envelope paths with a correlation therebetween.

19. The amplification stage of claim 11 wherein the signal generator is arranged to generate a sinusoidal signal on each of the input and envelope paths which are 180° out of phase.

20. The amplification stage of claim 11 further adapted to set the delay and amplitude variations in the one path determined to minimise the variation in the power detected in the output.