CREST FACTOR REDUCTION METHOD AND CIRCUIT FOR A MULTI-CARRIER SIGNAL

• US 20120093209A1
• Filed: 10/14/2010
• Published: 04/19/2012
• Est. Priority Date: 10/14/2010
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Kathrein-Werke KG. (Kathrein SE)
• Inventors: Schmidt, Georg, Schlee, Johannes
• Granted Patent: US 8,599,961 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04L 27/2624 by soft clipping

Abstract

A method for crest factor reduction of a multi-carrier signal is disclosed. The method comprises determining a plurality of signal values of a plurality of single-carrier signals prior to combining the plurality of single-carrier signals to form the multi-carrier signal. The method further comprises performing a joint potential peak detection on the plurality of signal values, producing a temporal position of a possible peak in the multi-carrier signal, generating a plurality of cancellation pulses, and injecting the plurality of cancellation pulses to the plurality of single-carrier signals at temporal injection positions which correspond to the temporal position of the possible peak in the multi-carrier signal. The single-carrier signals are then combined to form a crest factor reduced multi-carrier signal. A corresponding circuit and corresponding computer program product 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, the method comprising:

detecting time segments of the plurality of single-carrier signals prior to combining the plurality of single-carrier signals to form the multi-carrier signal, the sampling producing a plurality of sampled single-carrier signals;

performing a joint potential peak detection on the plurality of sampled single-carrier signals, the joint potential peak detection producing a temporal position of a possible peak in the multi-carrier signal;

generating a plurality of cancellation pulses;

injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal;

an

combining the single-carrier signals to form a crest factor reduced multi-carrier signal.

2. The method of claim 1, wherein the joint potential peak detection comprises:

determining a sum of absolute values of the plurality of single-carrier signals at a comparison temporal position, this sum being termed the “

absolute values sum”

;

comparing the absolute values sum to a peak indicator threshold; and

adopting the comparison temporal position as the temporal position of the possible peak in the multi-carrier signal if the absolute values sum is greater than the peak indicator threshold.

3. The method of claim 2, wherein the joint potential peak detection further comprises:

finding an interval in which the absolute values sum is greater than the peak indicator threshold;

determining values of the multi-carrier signal within the interval; and

determining a maximum of the values of the multi-carrier signal and a maximum position of the maximum, and adopting the maximum position as the temporal position of the possible peak in the multi-carrier signal.

4. The method of claim 1, wherein ones of the plurality of cancellation pulses have spectral properties that substantially match single-carrier spectral properties of corresponding ones the plurality of single-carrier signals.

5. The method of claim 1, wherein phases of ones of the plurality of cancellation pulses injected to corresponding ones of the plurality of single-carrier signals are substantially aligned to phases of the corresponding ones of the plurality of single-carrier signals so that ones of the plurality of cancellation pulses and corresponding ones of a plurality of single-carrier signal contributions to the possible peak in the multi-carrier signal are subject to an at least partial destructive interference.

6. The method of claim 1, further comprising:

weighting the plurality of cancellation pulses with a pulse amplitude distribution vector prior to injecting the plurality of cancellation pulses to the plurality of single-carrier signals.

7. A crest factor reduction circuit for multi-carrier signal formed by combining a plurality of single-carrier signals, the crest factor reduction circuit being placeable upstream of a combining point of the plurality of single-carrier signals and comprising:

a sampler for sampling the plurality of single-carrier signals and for producing a plurality of sampled single-carrier signals;

a joint peak detector for analyzing the plurality of single-carrier signals and for producing a temporal position of a possible peak in the multi-carrier signal;

a plurality of cancellation pulse generators; and

a plurality of cancellation pulse injectors for injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal.

8. The crest factor reduction circuit of claim 7, wherein the joint potential peak detector comprises:

an adder for adding the absolute values of the plurality of single-carrier signals at a comparison temporal position to form an absolute values sum; and

a comparator for comparing the absolute values sum with a peak indicator threshold; and

wherein the plurality of cancellation pulse injectors are adapted to inject the plurality of cancellation pulses at the comparison temporal threshold if the comparator has detected that the absolute values sum is greater than the peak indicator threshold.

9. The crest factor reduction circuit of claim 8, wherein the joint potential peak detector comprises:

an interval finder for finding an interval in which the absolute values sum is greater than the peak indicator threshold;

a multi-carrier signal evaluator for determining values of the multi-carrier signal within the signal; and

a maximum finder for determining a maximum of the values of the multi-carrier signal and a maximum position of the maximum, and for adopting the maximum position as the temporal position of the possible peak in the multi-carrier signal.

10. The crest factor reduction circuit of claim 7, wherein the plurality of cancellation pulse generators are adapted to generate cancellation pulses having spectral properties that substantially match single-carrier spectral properties of corresponding ones of the plurality of single-carrier signals.

11. The crest factor reduction circuit of claim 7, wherein the plurality of cancellation pulse injectors are adapted to substantially align phases of ones of the plurality if cancellation pulses to corresponding ones of the plurality of single-carrier signals so that ones of the plurality of cancellation pulses and corresponding ones of a plurality of single-carrier signal contributions to the possible peak in the multi-carrier signal are subject to an at least partial destructive interference.

12. The crest factor reduction circuit of claim 7, further comprising a cancellation pulse weighting unit for weighting the plurality of cancellation pulses with a pulse amplitude distribution vector upstream of the combining point.

13. A mobile communications transmitter comprising a crest factor reduction circuit for multi-carrier signal formed by combining a plurality of single-carrier signals, the crest factor reduction circuit being placeable upstream of a combining point of the plurality of single-carrier signals, the crest factor reduction circuit comprising:

a sampler for sampling the plurality of single-carrier signals and for producing a plurality of sampled single-carrier signals;

a joint peak detector for analyzing the plurality of single-carrier signals and for producing a temporal position of a possible peak in the multi-carrier signal;

a plurality of cancellation pulse generators; and

a plurality of cancellation pulse injectors for injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal.

14. A mobile communications base station comprising a crest factor reduction circuit for multi-carrier signal formed by combining a plurality of single-carrier signals, the crest factor reduction circuit being placeable upstream of a combining point of the plurality of single-carrier signals, the crest factor reduction circuit comprising:

a sampler for sampling the plurality of single-carrier signals and for producing a plurality of sampled single-carrier signals;

a joint peak detector for analyzing the plurality of single-carrier signals and for producing a temporal position of a possible peak in the multi-carrier signal;

a plurality of cancellation pulse generators; and

a plurality of cancellation pulse injectors for injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal.

15. 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, the method comprising:

detecting time segments of the plurality of single-carrier signals prior to combining the plurality of single-carrier signals to form the multi-carrier signal, the sampling producing a plurality of sampled single-carrier signals;

performing a joint potential peak detection on the plurality of sampled single-carrier signals, the joint potential peak detection producing a temporal position of a possible peak in the multi-carrier signal;

generating a plurality of cancellation pulses;

injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal;

combining the single-carrier signals to form a crest factor reduced multi-carrier signal.

16. 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 sampler for detecting time segments of the plurality of single-carrier signals and for producing a plurality of sampled single-carrier signals;

a joint peak detector for analyzing the plurality of single-carrier signals and for producing a temporal position of a possible peak in the multi-carrier signal;

a plurality of cancellation pulse generators; and

a plurality of cancellation pulse injectors for injecting the plurality of cancellation pulses to the plurality of single-carrier signals at a plurality of temporal injection positions, the plurality of temporal injection positions corresponding to the temporal position of the possible peak in the multi-carrier signal.