Amplifier linearizer

Abstract

The present invention provides an advanced adaptive predistortion linearization technique to dramatically reduce nonlinear distortion in power amplifiers over a very wide instantaneous bandwidth (up to 2 GHz) and over a wide range of amplifier types, input frequencies, signal types, amplitudes, temperature, and other environmental and signal conditions. In an embodiment of the invention, the predistortion linearization circuitry comprises (1) a higher-order polynomial model of an amplifier's gain and phase characteristics—higher than a third-order polynomial model; (2) an adaptive calibration technique; and (3) a heuristic calibration technique. The higher-order polynomial model is generated by introducing, for example, a plurality of multi-tone test signals with varying center frequency and spacing into the power amplifier. From the power amplifier's corresponding output, the nonlinearities are modeled by employing a higher-order curve fit to capture the irregularities in the nonlinear transfer function. Different distortion transfer functions can be implemented for different operating conditions. The adaptive calibration technique is based on a feedback analysis technique, which updates the applicable distortion transfer function by analyzing the error signal between the introduced input signal and the output signal in real-time. The heuristic calibration technique implements different distortion transfer functions based on historical operating conditions and optimal configurations of the power amplifier.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61 / 187,546, entitled “Amplifier Linearizer,” and filed Jun. 16, 2010, the disclosure of which is incorporated by reference herein in its entirety. The present application is also a continuation-in-part of and claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 12 / 112,380, entitled “Adaptive Mismatch Compensators and Methods for Mismatch Compensation,” the disclosure of which is incorporated by reference herein in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of Invention[0003]The present invention relates to electronics and more specifically, to a technique for improving the linear performance of electrical components such as power amplifiers in radio frequency (RF) transceiver systems.[0004]2. Description of Related Art[0005]An electronic or power amplifier is a device for increasing the power of an inpu...

AI Technical Summary

Benefits of technology

"The present invention provides an advanced adaptive predistortion linearization technique to reduce nonlinear distortion in power amplifiers over a wide range of conditions. The technique improves amplifier efficiency by operating closer to saturation and can use lower power, lower mass, and lower cost amplifiers. The invention adapts to nonlinear distortion models, which can be updated in real-time and cancels out errors. The technique can be used in RF transceivers and can be calibrated based on operating conditions. Overall, the invention removes nonlinear distortion and improves the performance of power amplifiers."

Problems solved by technology

This causes interference on other frequency channels.

Power amplifier linearity and efficiency are crucial issues in the design of electronic systems.

However, the more efficient power amplifier configuration is used the more nonlinear it usually becomes.

Linearity errors in power amplifiers cause harmonic distortion and intermodulation distortion, which can limit the performance of state-of-the-art electronic systems such as, but not limited to radar systems, digital transceivers for wireless 3G and 4G communications, laboratory test equipment, medical imaging, and audio and video compression.

All conventional linearization methods are limited in their maximum correctable range, which is the region of power output level near the onset of saturation.

One method, known as a feedforward technique, is frequently employed and improves linearity, but results in poor power amplifier efficiency.

However, for advanced RF systems with very high instantaneous bandwidths, transfer functions based on second-order or third-order polynomials are not accurate enough to prevent all non-linear distortion.

In fact, many RF devices produce irregular nonlinearities that are difficult to model with standard, integer-power polynomial functions.

However, when operating conditions vary, e.g., temperature, time, or frequency, the transfer function may no longer be suitable to adequately remove non-linear distortion.

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