Method and apparatus for calculating the predistortion function from a power amplifier
First Claim
1. An apparatus for calculating a predistortion function from characteristics of a power amplifier, comprising:
- a predistortion module responsive to a predistortion function and an input signal by generating a predistorted signal;
the power amplifier responsive to said predistorted signal by generating an output signal; and
a predistortion function calculating module responsive to said amplifier characteristics by generating said predistortion function without using the generated predistorted signal, said predistortion function calculating module using a magnitude of said input signal at a given time to estimate said predistorted signal at said given time to calculate said predistortion function.
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Abstract
Disclosed is an apparatus and method for iteratively calculating the predistortion function from a power amplifier when the inverse to the power amplifier characterization does not exist analytically. A predistortion module generates a predistorted signal in response to an input signal and a predistortion function received from a predistortion function calculating module. The predistortion function calculating module generates the predistortion function in response to given amplifier characteristics. In particular, the predistortion function calculating module uses a magnitude of the input signal at a given time to estimate the predistorted signal at that given time in order to calculate the predistortion function. Optionally, subsequent iterations based on the magnitude of the estimate occur until a desired accuracy of the predistorted signal approximation and of the predistortion function is achieved.
22 Citations
22 Claims
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1. An apparatus for calculating a predistortion function from characteristics of a power amplifier, comprising:
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a predistortion module responsive to a predistortion function and an input signal by generating a predistorted signal;
the power amplifier responsive to said predistorted signal by generating an output signal; and
a predistortion function calculating module responsive to said amplifier characteristics by generating said predistortion function without using the generated predistorted signal, said predistortion function calculating module using a magnitude of said input signal at a given time to estimate said predistorted signal at said given time to calculate said predistortion function. - View Dependent Claims (2, 3, 4, 5, 6)
wherein “
n”
is a time index, wherein xn is a current value of said predistorted signal, wherein un is a current value of said input signal, wherein β
is a complex polynomial representation of said power amplifier, wherein coefficients are generated for said complex polynomial representation for each of a plurality of delay taps, wherein M is an order of power amplifier memory equal to the number of said plurality of delay taps and wherein |xn| is estimated by |un|.
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6. The apparatus of claim 1, wherein the predistortion function calculating module generates said predistortion function by using an estimated predistortion signal, the estimated predistortion signal calculated using at least the input signal.
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7. A wireless radio frequency communications system including an apparatus for calculating a predistortion function from characteristics of a power amplifier with memory, comprising:
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a predistortion module responsive to a predistortion function and an input signal by generating a predistorted signal;
the power amplifier responsive to said predistorted signal by generating an output signal; and
a predistortion function calculating module responsive to said power amplifier characteristics by generating said predistortion function without using the generated predistorted signal, said predistortion function calculating module using a magnitude of said input signal at a given time to estimate said predistorted signal at said given time to calculate said predistortion function. - View Dependent Claims (8, 9, 10, 11, 12)
wherein “
n”
is a time index, wherein xn is a current value of said predistorted signal, wherein un is a current value of said input signal, wherein β
is a complex polynomial representation of said power amplifier, wherein coefficients are generated for said complex polynomial representation for each of a plurality of delay taps, wherein M is an order of power amplifier memory equal to the number of said plurality of delay taps and wherein |xn| is estimated by |un|.
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12. The system of claim 7, wherein the predistortion function calculating module generates said predistortion function by using an estimated predistortion signal, the estimated predistortion signal calculated using at least the input signal.
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13. A method for calculating a predistortion function from characteristics of a power amplifier with memory, comprising the steps of:
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generating a predistorted signal in response to a predistortion function and an input signal;
generating an output signal in response to said predistorted signal; and
generating a predistortion function in response to said power amplifier characteristics without using the generated predistorted signal, said step of generating a predistortion function including the step of substituting a magnitude of said input signal at a given time to estimate said predistorted signal at said given time to generate said predistortion function. - View Dependent Claims (14, 15, 16, 17, 18)
wherein “
n”
is a time index, wherein xn is a current value of said predistorted signal, wherein un is a current value of said input signal, wherein β
is a complex polynomial representation of said power amplifier, wherein coefficients are generated for said complex polynomial representation for each of a plurality of delay taps, wherein M is an order of power amplifier memory equal to the number of said plurality of delay taps and wherein |xn| is estimated by |un|.
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18. The method of claim 13, wherein said step of generating a predistortion function includes using an estimated predistortion signal, the estimated predistortion signal calculated using at least the input signal.
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19. An apparatus for calculating a predistortion function from a characteristics curve of a power amplifier, comprising:
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a predistortion module responsive to a predistortion function representative of an inverse to said characteristics curve and an input signal by generating a predistorted signal;
the power amplifier responsive to said predistorted signal by generating an output signal; and
a predistortion function calculating module responsive to said power amplifier characteristics curve by generating said predistortion function without using the generated predistorted signal, said predistortion function calculating module using a magnitude of said input signal at a given time as an estimate of said predistorted signal at said given time to calculate said predistortion function. - View Dependent Claims (20, 21, 22)
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Specification