Uncorrelated adaptive predistorter
First Claim
1. An uncorrelated adaptive predistorter configured for use with an RF power amplifier, the uncorrelated adaptive predistorter comprising:
- an input loop configured to be coupled to the input of an RF power amplifier, the input loop including a look-up table containing predistortion values derived from a spline function with knots wherein knots of the spline function are placed along an index of the look-up table, the input loop configured to apply the predistortion values to an input signal, in response to a monotonically increasing function of the input signal power, for forming a predistorted input signal; and
an output loop coupled to the output of the RF power amplifier, the output loop including circuitry operable for selecting an intermodulation distortion product from the RF power amplifier output and including detector circuitry configured to measure the magnitude of the intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal;
processing circuitry operable, upon variation of the placement of the knots along the look-up table index, to generate predistortion values and to evaluate the measured magnitudes of the respective intermodulation distortion products that result from the variation in knot placement and resulting predistortion values, the processing circuitry further operable to update the predistortion values in the look-up table based on the magnitude evaluation, so that the updated predistortion values in the look-up table are uncorrelated with respect to the input signal.
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Accused Products
Abstract
An uncorrelated adaptive predistorer configured for use with an RF power amplifier having an input loop configured to be coupled to the input of the RF power amplifier an output loop coupled to the output of the RF power amplifier. Such an input loop includes a look-up table containing predistortion values to be apply to an input signal, in response to a monotonically increasing function of the input signal power, for forming a predistorted input signal. Such an output loop configured to measure an intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal, and operable to update the predistortion values in the look-up table.
107 Citations
30 Claims
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1. An uncorrelated adaptive predistorter configured for use with an RF power amplifier, the uncorrelated adaptive predistorter comprising:
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an input loop configured to be coupled to the input of an RF power amplifier, the input loop including a look-up table containing predistortion values derived from a spline function with knots wherein knots of the spline function are placed along an index of the look-up table, the input loop configured to apply the predistortion values to an input signal, in response to a monotonically increasing function of the input signal power, for forming a predistorted input signal; and an output loop coupled to the output of the RF power amplifier, the output loop including circuitry operable for selecting an intermodulation distortion product from the RF power amplifier output and including detector circuitry configured to measure the magnitude of the intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal; processing circuitry operable, upon variation of the placement of the knots along the look-up table index, to generate predistortion values and to evaluate the measured magnitudes of the respective intermodulation distortion products that result from the variation in knot placement and resulting predistortion values, the processing circuitry further operable to update the predistortion values in the look-up table based on the magnitude evaluation, so that the updated predistortion values in the look-up table are uncorrelated with respect to the input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An amplifier system comprising an RF power amplifier and an uncorrelated adaptive predistorter, the uncorrelated adaptive predistorter comprising:
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an input loop configured to be coupled to the input of the RF power amplifier, the input loop including a look-up table containing predistortion values derived from a spline function with knots wherein knots of the spline function are placed along an index of the look-up table, the input loop configured to apply the predistortion values to an input signal, in response to a monotonically increasing function of the input signal power, for forming a predistorted input signal; and an output loop coupled to the output of the RF power amplifier, the output loop including circuitry operable for selecting an intermodulation distortion product from the RF power amplifier output and including detector circuitry configured to measure the magnitude of the intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal; processing circuitry operable, upon variation of the placement of the knots along the look-up table index, to generate predistortion values and to evaluate the measured magnitudes of the respective intermodulation distortion products that result from the variation in knot placement and resulting predistortion values, the processing circuitry further operable to update the predistortion values in the look-up table based on the magnitude evaluation, so that the updated predistortion values in the look-up table are uncorrelated with respect to the input signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An amplifier system comprising an RF power amplifier and an uncorrelated adaptive predistorter, the uncorrelated adaptive predistorter comprising:
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an input loop configured to be coupled to the input of the RF power amplifier, the input loop including a look-up table containing magnitude and phase predistortion values derived from a spline function with variables wherein knots of the spline function are placed along an index of the look-up table, the input loop configured to apply the predistortion values to a modulated RF input signal, in response to a monotonically increasing function of the input signal power, for forming a predistorted input signal; the input loop including a detector circuit coupled to the look-up table and configured to produce a scalar value representative of the power of the input signal; an analog-to-digital converter circuit coupled to the detector circuit and the look-up table, the analog-to-digital converter circuit configured to convert the scalar value to a digital signal that functions as an index to the look-up table; a complex attenuator coupled to the look-up table and configured to combine predistortion values in the look-up table with the input signal; and a delay circuit coupled to the complex attenuator and configured to delay the application of the input signal to the complex attenuator; an output loop coupled to the output of the RF power amplifier, the output loop including circuitry operable for selecting an intermodulation distortion product from the RF power amplifier output and including detector circuitry configured to measure the magnitude of the intermodulation distortion product of the RF power amplifier output resulting from the predistorted input signal; the output loop further including processing circuitry operable, upon variation of the placement of the knots along the look-up table index, to generate predistortion values and to evaluate the measured magnitudes of the respective intermodulation distortion products that result from the variation in knot placement and resulting predistortion values, the processing circuitry further operable to update the predistortion values in the look-up table based on the magnitude evaluation, so that the updated predistortion values in the look-up table are uncorrelated with respect to the input signal. - View Dependent Claims (25, 26)
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27. An uncorrelated adaptive method of predistorting an input signal applied to an RF power amplifier, the method comprising:
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producing a scalar value representative of the power of the input signal; applying the scalar value to index a look-up table containing predistortion values derived from a spline function with knots wherein knots of the spline function are placed along an index of the look-up table and applying the predistortion values to the input signal for forming a predistorted input signal that yields an output from the RF power amplifier; measuring the magnitude of an intermodulation distortion product of the RF power amplifier output to select optimal predistortion values; varying the placement of the knots along the look-up table index, and generating predistortion values and evaluating the measured magnitudes of the respective intermodulation distortion products that result from the variation in knot placement and resulting predistortion values; updating the predistortion values in the look-up table based on the magnitude evaluation, so that the updated predistortion values in the look-up table are uncorrelated with respect to the input signal; and combining the predistortion values with the input signal to improve the linearity of the RF power amplifier. - View Dependent Claims (28, 29, 30)
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Specification