Power amplifier time-delay invariant predistortion methods and apparatus
First Claim
1. A predistortion system for linearizing the output of a power amplifier comprising:
- a first receiver configured to receive a first signal representative of a radio frequency (RF) modulated signal;
a second receiver configured to receive a feedback signal representative of at least one nonlinear characteristic of a power amplifier;
a reference path communicatively coupled with the first receiver and a predistortion controller;
a feedback path communicatively coupled with the second receiver and the predistortion controller;
the predistortion controller comprising at least one lookup table of a predetermined size, wherein the lookup table comprises at least one correction value that falls within a range determined by the predetermined size of the table; and
wherein the at least one lookup table is configured to;
respond to inputs derived from the difference between squares of the in-phase and quadrature components, respectively, of the first signal and the feedback signal;
store at least one time-delay value that compensates for a time delay between the reference path and the feedback path;
adaptively update the at least one correction value in the table by combining both a non-linear correction value of the power amplifier and the at least one time-delay value; and
wherein the controller is configured to generate a correction factor for correcting the nonlinear characteristics of the power amplifier, wherein the correction factor is based on the at least one correction value in the lookup table; and
a processor, configured to;
combine the RF modulated signal with a second signal corresponding to the correction factor; and
supply the combined RF modulated signal with said second signal to the power amplifier to linearize the output of the power amplifier.
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Abstract
An embodiment of the invention is a time-delay invariant predistortion approach to linearize power amplifiers in wireless RF transmitters. The predistortion architecture is based on the stored-compensation or memory-compensation principle by using a combined time-delay addressing method, and therefore, the architecture has an intrinsic, self-calibrating time-delay compensation function. The predistortion architecture only uses a lookup table to conduct both the correction of non-linear responses of a power amplifier and the compensation of any time-delay effects presented in the same system. Due to the time-delay invariant characteristic, the predistortion design has a wider dynamic range processing advantage for wireless RF signals, and therefore can be implemented in multi-carrier and multi-channel wireless systems.
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Citations
18 Claims
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1. A predistortion system for linearizing the output of a power amplifier comprising:
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a first receiver configured to receive a first signal representative of a radio frequency (RF) modulated signal; a second receiver configured to receive a feedback signal representative of at least one nonlinear characteristic of a power amplifier; a reference path communicatively coupled with the first receiver and a predistortion controller; a feedback path communicatively coupled with the second receiver and the predistortion controller; the predistortion controller comprising at least one lookup table of a predetermined size, wherein the lookup table comprises at least one correction value that falls within a range determined by the predetermined size of the table; and wherein the at least one lookup table is configured to; respond to inputs derived from the difference between squares of the in-phase and quadrature components, respectively, of the first signal and the feedback signal; store at least one time-delay value that compensates for a time delay between the reference path and the feedback path; adaptively update the at least one correction value in the table by combining both a non-linear correction value of the power amplifier and the at least one time-delay value; and wherein the controller is configured to generate a correction factor for correcting the nonlinear characteristics of the power amplifier, wherein the correction factor is based on the at least one correction value in the lookup table; and a processor, configured to; combine the RF modulated signal with a second signal corresponding to the correction factor; and supply the combined RF modulated signal with said second signal to the power amplifier to linearize the output of the power amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A predistortion system for linearizing the output of a power amplifier comprising:
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a first receiver, configured to receive a first signal representative of a radio frequency (RF) modulated signal; a second receiver, configured to receive a feedback signal representative of at least one nonlinear characteristic of a power amplifier; a reference path communicatively coupled with the first receiver and a predistortion controller; a feedback path communicatively coupled with the second receiver and the predistortion controller; the predistortion controller comprising an address former and a lookup table, wherein; the predistortion controller is configured to; determine a time delay value that compensates for a delay between the reference path and the feedback path; and store the at least one time-delay value; the lookup table comprises correction values that are time invariant and are based on at least one operating characteristic of the power amplifier and the time delay value; the lookup table being responsive to inputs derived from the difference between the squares of the in-phase and quadrature components, respectively, of the first signal and the feedback signal; and a processor, configured to combine the RF modulated signal with a signal corresponding to at least one of the correction values supplied by the lookup table. - View Dependent Claims (9, 10, 11, 12)
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13. A predistortion system for linearizing the output of a power amplifier comprising:
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a first receiver configured to receive a first signal representative of a radio frequency (RF) modulated signal; a second receiver configured to receive a feedback signal representative of at least one nonlinear characteristic of a power amplifier; a reference path communicatively coupled with the first receiver and a predistortion controller; a feedback path communicatively coupled with the second receiver and the predistortion controller; the predistortion controller comprising at least one lookup table of a predetermined size; wherein the at least one lookup table is configured to respond to; a first input derived from a difference between the square of a quadrature component of the first signal and the square of a quadrature component of the feedback signal, and a second input derived from a difference between the square of an in-phase component of the first signal and the square of an in-phase component of the feedback signal; and wherein the predistortion controller is configured to generate a correction factor for correcting at least one nonlinear characteristic of the power amplifier based on at least the first input or the second input. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification