LINEARIZATION OF A TRANSMIT AMPLIFIER
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Abstract
An apparatus and method of linearization of a digitally-controlled pre-power amplifier (DPA) and RF power amplifier (PA) for performing predistortion calibration to compensate for nonlinearlities in the DPA and PA circuits. A predistortion look up table (LUT) stores measured distortion compensation data that is applied to the TX data before being input to the digital-to-frequency converter (DFC), DPA and PA. The on-chip receiver, which is normally inactive during the TX burst in a half-duplex operation, demodulates the RF PA output and uses the digital I/Q RX outputs to perform calibration of the TX pre-distortion tables. A sample of the RF output signal is provided to the receiver chain. While the PA (DPA) code is increasing (or decreasing), the amplitude and phase of the recovered I/Q samples are used to determine the instantaneous value of the AM/AM and AM/PM pre-distortion from which an update to the predistortion tables may be computed.
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Citations
41 Claims
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1. (canceled)
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4. A method of linearization of a transmit amplifier, said method comprising the steps of:
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scanning a plurality of power amplifier codes; generating a transmit amplifier output signal in accordance with each code scanned; and determining one or more predistortion values in accordance with said transmit amplifier output signal; and wherein said step of determining comprises the step of inputting said transmit amplifier output signal to receiver operative to demodulate said transmit amplifier output signal. - View Dependent Claims (2, 3, 5, 7)
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6. A method of linearization of a transmit amplifier, said method comprising the steps of:
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scanning a plurality of power amplifier codes; generating a transmit amplifier output signal in accordance with each code scanned; and determining one or more predistortion values in accordance with said transmit amplifier output signal;
wherein said transmit amplifier comprises a digitally controlled power amplifier.
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8. A method of compensating for predistortion of a power amplifier, said method comprising the steps of
scanning a plurality of power amplifier codes; -
generating a power amplifier output signal in accordance with each code scanned; providing controlled leakage of said power amplifier output signal to a receiver chain operative to demodulate said power amplifier output signal to yield a demodulated signal therefrom; calculating amplitude and phase distortion values in accordance with said demodulated signal; and calibrating a predistortion table with said amplitude and phase distortion values. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of predistortion calibration of a power amplifier, said method comprising the steps of
stepping through a dynamic range of codes of said power amplifier; -
inputting each code to a transmit chain comprising a predistortion look up table (LUT) of transmit amplifier predistortion values to generate a radio frequency (RF) output signal in response thereto; demodulating said RF output signal to yield a demodulated signal; calculating an instantaneous correction to the predistortion values stored in said predistortion LUT in accordance with said demodulated signal; and updating the contents of said predistortion LUT in accordance with said calculated instantaneous correction. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. An apparatus for calibrating predistortion of a digitally controlled power amplifier (DPA), comprising:
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circuitry for stepping through a range of codes of said DPA; a transmit chain comprising a predistortion look up table (LUT) adapted to store a plurality of amplifier predistortion values, said transmit chain operative to generate a radio frequency (RF) output signal in response to each code; circuitry for coupling said RF output signal to a receiver chain, said receive chain operative to demodulate said RF output signal to generate a demodulated signal therefrom; circuitry for calculating corrections to the predistortion values stored in said predistortion LUT in accordance with said recovered I and Q values; and update circuitry for updating the contents of said predistortion LUT in accordance with said calculated corrections. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41-43. -43. (canceled)
Specification