Claims
- 1. A method of canceling gain and phase imbalance of a signal, comprising:
determining a complex conjugate of the signal; estimating a cancellation parameter, said cancellation parameter based on the signal divided by its complex conjugate; calculating a correction value for the signal using said cancellation parameter and said complex conjugate; and correcting the signal by subtracting said correction value from the signal.
- 2. The method of claim 1, the signal provided in sequential samples, wherein said estimating a cancellation parameter comprises performing a stochastic gradient algorithm.
- 3. The method of claim 2, wherein said estimating a cancellation parameter comprises:
multiplying a cancellation parameter value by a complex conjugate sample to provide a comparison value; subtracting said comparison value from a signal sample to provide an error value; applying an adaptation function using said error value and said cancellation parameter and updating said cancellation parameter value; and repeating said multiplying, subtracting, applying and updating in an iterative manner to converge sequential cancellation parameter values.
- 4. The method of claim 3, wherein said calculating a correction value comprises dividing said comparison value by a constant value.
- 5. The method of claim 4, said comparison value comprising a digital value, wherein said dividing said comparison value by a constant value comprises shifting said digital value to divide by two.
- 6. The method of claim 3, wherein said applying an adaptation function further comprises:
generating a cancellation parameter adjust value by multiplying an error value by an adaptation value and a signal sample; and adding said cancellation parameter adjust value to said cancellation parameter value.
- 7. The method of claim 6, the signal comprising a plurality of packets, further comprising:
using a default cancellation parameter value to begin a stochastic gradient determination for a first packet; storing a final cancellation parameter value determined from said first packet; and using said final cancellation parameter value as an initial cancellation parameter value to begin said stochastic gradient determination for a second packet.
- 8. The method of claim 7, further comprising employing an adaptation algorithm to generate a plurality of decreasing adaptation values.
- 9. The method of claim 8, wherein said employing an adaptation function comprises:
using a first adaptation value for a first number of packets; reducing said first adaptation value to a second adaptation value for a second number of packets; and reducing said second adaptation value to a third adaptation value for subsequent packets.
- 10. The method of claim 1, wherein said estimating a cancellation parameter comprises performing a least squares estimation.
- 11. The method of claim 10, the signal provided in sequential complex samples, wherein said performing a least squares estimation comprises using sequential samples of the signal and corresponding complex conjugate samples.
- 12. The method of claim 10, wherein said calculating a correction value comprises multiplying said cancellation parameter by said complex conjugate and dividing by a predetermined constant.
- 13. A method of compensating a first signal for gain and phase imbalance, comprising:
receiving a first signal having gain and phase imbalance; creating a second signal that is a complex conjugate of said first signal; creating a third signal by multiplying said second signal by an estimated cancellation parameter, said cancellation parameter based on a ratio of said first and second signals; and creating a corrected signal by subtracting one half of said third signal from said first signal.
- 14. The method of claim 13, wherein said cancellation parameter is an adaptable tap in a digital signal processing circuit.
- 15. The method of claim 13, further comprising:
updating said cancellation parameter using a stochastic gradient algorithm.
- 16. The method of claim 13, further comprising:
creating an error signal by subtracting said third signal from said first signal; and updating said cancellation parameter by applying a stochastic gradient algorithm using said first signal and said error signal to create an adjust signal and adding said adjust signal to said cancellation parameter.
- 17. The method of claim 16, wherein said applying said stochastic gradient algorithm includes using an adaptation function for loop control.
- 18. A cancellation system for compensating for gain and phase of an imbalanced signal, comprising:
a conjugate conversion unit that receives the imbalanced signal and provides a complex conjugate signal being a complex conjugate of the imbalanced signal; an estimator that estimates a cancellation parameter based on the imbalanced signal divided by its complex conjugate; a combiner that combines said cancellation parameter and said complex conjugate signal to provide a cancellation signal; a converter that converts said cancellation signal to a correction signal; and a subtractor that subtracts said correction signal from the imbalanced signal to provide a corrected signal.
- 19. The cancellation system of claim 18, further comprising:
said combiner comprising an adaptable tap that multiplies said complex conjugate signal by said cancellation parameter to provide said cancellation signal; a subtractor that subtracts said cancellation signal from the imbalanced signal to provide an error signal; and wherein said estimator comprises an update unit, coupled to said adaptable tap, that applies a stochastic gradient algorithm using said cancellation parameter and said error signal to update said cancellation parameter of said adaptable tap.
- 20. The cancellation system of claim 19, wherein said update unit employs an adaptation function.
- 21. The cancellation system of claim 18, wherein said converter comprises a digital shift register that divides said cancellation signal by two to generate said correction signal.
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application is based on U.S. Provisional Patent Application entitled “Adaptive Gain And Phase Imbalance Cancellation”, Serial No. 60/407,135, filed Aug. 29, 2002, which is hereby incorporated by reference in its entirety.
Provisional Applications (1)
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Number |
Date |
Country |
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60407135 |
Aug 2002 |
US |