CREST FACTOR REDUCTION FOR A MULTICARRIER-SIGNAL WITH SPECTRALLY SHAPED SINGLE-CARRIER CANCELATION PULSES

• US 20120093210A1
• Filed: 10/14/2010
• Published: 04/19/2012
• Est. Priority Date: 10/14/2010
• Status: Active Grant

• Current Assignee: Kathrein SE
• Original Assignee: Kathrein-Werke KG. (Kathrein SE)
• Inventors: Schmidt, Georg, Schlee, Johannes
• Granted Patent: US 8,619,903 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04L 27/2624 by soft clipping

Abstract

A method for crest factor reduction of a multi-carrier signal is disclosed. The multi-carrier signal comprises a plurality of single-carrier signals, each single-carrier signal having signal-specific spectral properties. The method comprises identifying a peak in the multi-carrier signal and a time of occurrence of the peak and generating a plurality of cancellation pulses depending on the time of occurrence of the peak. A particular cancellation pulse of the plurality of cancellation pulses is associated with a particular single-carrier signal and cancellation pulse-specific spectral properties of the particular cancellation pulse substantially match the signal-specific spectral properties of the associated particular single-carrier signal. The method further comprises combining the plurality of cancellation pulses to form a combined cancellation pulse and applying the combined cancellation pulse to the multi-carrier signal to reduce the peak. A corresponding circuit and corresponding computer program products useable during manufacture and operation are also disclosed.

Claims

1. A method for crest factor reduction of a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the method comprising:

identifying a peak in the multi-carrier signal and a time of occurrence of the peak;

generating a plurality of cancellation pulses depending on the time of occurrence of the peak, wherein a particular cancellation pulse of the plurality of cancellation pulses is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of the particular cancellation pulse substantially match the signal-specific spectral properties of the associated particular single-carrier signal;

combining the plurality of cancellation pulses to form a combined cancellation pulse; and

applying the combined cancellation pulse to the multi-carrier signal to reduce the peak.

2. The method of claim 1, further comprising:

weighting the plurality of cancellation pulses with a plurality of weighting factors prior to combining the plurality of cancellation pulses.

3. The method of claim 2, further comprising:

adjusting the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals, each variable distortion threshold of the plurality of variable distortion thresholds defining an allowable range of operation for one of the plurality of single-carrier signals with respect to distortions.

4. The method of claim 3, wherein the adjusting comprises an optimization of the weighting factors based on evaluating and minimizing a crest factor reduction distortion of the multi-carrier signal caused by the crest factor reduction.

5. The method of claim 4, wherein the optimization is a convex optimisation.

6. The method of claim 1, wherein two or more successive ones of the combined cancellation pulses are generated by two or more different pulse generators of a crest factor reduction circuit performing the method for crest factor reduction.

7. The method of claim 1, wherein the identifying the peak also produces at least one of a value of a peak amplitude of the peak and a peak phase of the peak, and wherein the generating the plurality of cancellation pulses depends on at least one of the peak amplitude.

8. A crest factor reduction circuit for a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the crest factor reduction circuit comprising:

a peak detector for identifying a peak in the multi-carrier signal and a time of occurrence of the peak;

a multi-pulse generator for generating a plurality of cancellation pulses depending on the time of occurrence, the multi-pulse generator comprising a plurality of pulse generators and a cancellation pulse combiner connected to a pulse output of the plurality of pulse generators and adapted to form a combined cancellation pulse, wherein a particular pulse generator of the plurality of pulse generators is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of a cancellation pulse generated by the particular pulse generator substantially match the signal-specific spectral properties of the associated particular single-carrier signal;

a pulse injector for injecting the combined cancellation pulse to the multi-carrier signal.

9. The crest factor reduction circuit of claim 8, wherein the multi-pulse generator further comprises:

a weighting unit interposed between the plurality of pulse generators and the cancellation pulse combiner, the weighting unit being adapted to weight the plurality of cancellation pulses with a plurality of weighing factors prior to the combining the plurality of cancellation pulses.

10. The crest factor reduction circuit of claim 9, further comprising:

an adaptive adjuster adapted to adjust the weighting factors depending on a plurality of variable distortion thresholds for the plurality of single-carrier signals.

11. The crest factor reduction circuit of claim 10, wherein the adaptive adjuster is adapted to perform an optimization of the weighting factors based on evaluating and minimizing a crest factor reduction distortion of the multi-carrier signal caused by the crest factor reduction.

12. The crest factor reduction circuit of claim 8, comprising a plurality of the multi-pulse generators, the plurality of the multi-pulse generators being adapted to generate a plurality of combined cancellation pulses in a staggered succession.

13. The crest factor reduction circuit of claim 8, wherein the identifying the peak detector produces at least one of a value of a peak amplitude of the peak and a peak phase of the peak, and wherein the multi-pulse generator is adapted to generate the plurality of cancellation pulses depending on at least one of the peak amplitude and the peak phase.

14. A mobile communications transmitter comprising a crest factor reduction circuit according to claim 8.

15. A mobile communications base station comprising a crest factor reduction circuit according to claim 8.

16. A computer program product comprising a non-transitory computer-usable medium having control logic stored therein for causing processor to execute a method for crest factor reduction of a multi-carrier signal comprising a plurality of single-carrier signals, each single-carrier signal of the plurality of single-carrier signals having signal-specific spectral properties, the method comprising:

identifying a peak in the multi-carrier signal and a time of occurrence of the peak;

generating a plurality of cancellation pulses depending on the time of occurrence of the peak, wherein a particular cancellation pulse of the plurality of cancellation pulses is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of the particular cancellation pulse substantially match the signal-specific spectral properties of the associated particular single-carrier signal;

combining the plurality of cancellation pulses to form a combined cancellation pulse; and

applying the combined cancellation pulse to the multi-carrier signal to reduce the peak.

17. A computer program product comprising a non-transitory computer-usable medium having control logic stored therein for causing a computer to manufacture a crest factor reduction circuit comprising:

a peak detector for identifying a peak in the multi-carrier signal and a time of occurrence of the peak;

a multi-pulse generator for generating a plurality of cancellation pulses depending on the time of occurrence, the multi-pulse generator comprising a plurality of pulse generators and a cancellation pulse combiner connected to a pulse output of the plurality of pulse generators and adapted to form a combined cancellation pulse, wherein a particular pulse generator of the plurality of pulse generators is associated with a particular single-carrier signal of the plurality of single-carrier signals and wherein cancellation pulse-specific spectral properties of a cancellation pulse generated by the particular pulse generator substantially match the signal-specific spectral properties of the associated particular single-carrier signal;

a pulse injector for injecting the combined cancellation pulse to the multi-carrier signal.