Technique for determining a time alignment error
A technique for determining a time alignment (TA) error in a circuitry is provided. One or few measurement cycles can be utilized for a closed-loop TA alignment, e.g., for envelope tracking in a transmitter. As to a method aspect of the technique, the amplitudes of a first signal and a second signal are determined. A first measure is computed that is indicative of a relative amplitude error, and a second measure is computed that is indicative of a variation of at least one of the amplitudes. The TA error is determined by correlating the first and second measures.
1. A method of determining a time alignment error in a transmitter, the method comprising:
determining a first amplitude of a first signal upstream of a signal processing unit in the transmitter and a second amplitude of a second signal downstream of the signal processing unit;
computing a first measure for a difference between the first amplitude and the second amplitude and a second measure for a variation of at least one of the first amplitude and the second amplitude; and
correlating the first measure and the second measure for determining the time alignment error.
2. The method of claim 1 , wherein determining the second amplitude includes at least one of tapping-off the second signal, down-conversion, and analog-to-digital conversion.
3. The method of claim 1 , wherein signal processing of the first signal in the signal processing unit includes at least one of digital-to-analog conversion, up-conversion, and power amplification.
4. The method of claim 3 , further comprising controlling a voltage of a power supply for the power amplification based on the first amplitude.
5. The method of claim 4 , further comprising controlling, based on the determined time alignment error, at least one of a first time delay in a first path including the power supply and a second time delay in a second signal path including the signal processing unit.
6. The method of claim 5 , wherein at least one of the first time delay and the second time delay are controlled according to a closed-loop control minimizing the determined time alignment error.
7. The method of claim 1 , wherein the correlating is based on a plurality of the first measures and the second measures.
8. The method of claim 1 , wherein the correlating includes computing a linear estimator for the correlation between the first measure and the second measure.
9. The method of claim 1 , wherein the correlating includes computing a least square regression, wherein a slope of the least square regression determines the time alignment error.
10. The method of claim 1 , wherein the correlating includes averaging a ratio of the first measure and the second measure.
11. The method of claim 1 , wherein the correlating includes averaging the first measure with a sign determined by the second measure.
12. The method of claim 1 , further comprising selecting a subset out of a plurality of determined first and second amplitudes for computing the first and second measures.
13. The method of claim 1 , wherein at least the determining the first and second amplitudes is performed during a data transmission via the transmitter.
14. A non-transitory computer readable recording medium storing a computer program product for determining a time alignment error in a transmitter, the computer program product comprising software instructions which, when run on processing circuitry of a computing device, causes the computing device to:
determine a first amplitude of a first signal upstream of a signal processing unit in the transmitter and a second amplitude of a second signal downstream of the signal processing unit;
compute a first measure for a difference between the first amplitude and the second amplitude and a second measure for a variation of at least one of the first amplitude and the second amplitude; and
correlate the first measure and the second measure for determining the time alignment error.
15. A device for determining a time alignment error in a transmitter, the device comprising:
processing circuitry;
memory containing instructions executable by the processing circuitry whereby the device is operative to:
determine a first amplitude of a first signal upstream of a signal processing unit in the transmitter and a second amplitude of a second signal downstream of the signal processing unit;
compute a first measure for a difference between the first amplitude and the second amplitude and a second measure for a variation of at least one of the first amplitude and the second amplitude; and
correlate the first measure and the second measure for determining the time alignment error.