Digital Pre-Distortion Calibration for Nonlinear Power Amplifiers
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Solution Overview
Problem
Existing power amplifiers in wireless communication networks face challenges in maintaining linearity, leading to data errors due to amplitude and phase distortion, and current pre-distortion calibration methods interrupt data throughput by using non-data calibration signals.
Innovation Solution
A digital pre-distortion system that includes a DPD processor and calibration engine, which applies pre-distortion coefficients to digital baseband data signals without interrupting data transmission, by comparing digitized RF output signals with digital baseband signals to update distortion coefficients and compensate for nonlinearities in power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-distortion calibration is performed using non-data calibration signals, then power amplifier nonlinearity is compensated, but data throughput is interrupted
Solution Approach 1:
The patent performs calibration using actual data signals continuously flowing through the system rather than interrupting data flow with separate calibration signals. The calibration process operates continuously on the data stream itself, eliminating interruptions while maintaining both signal quality and throughput.
Solution Approach 2:
The patent makes the data signal serve dual purposes: it functions both as the useful data transmission carrier and as the calibration signal for characterizing power amplifier nonlinearity. This eliminates the need for separate non-data calibration signals and allows simultaneous data transmission and calibration.
2Reliability
If power amplifier is biased for best linearity, then signal quality is improved, but power consumption increases
Solution Approach 1:
The patent applies digital pre-distortion coefficients to modify the input signal parameters (amplitude and phase) before amplification. This allows the power amplifier to operate at higher efficiency bias points while the pre-distortion compensation maintains the desired linear output characteristics, thus reducing power consumption while preserving signal quality.
Solution Approach 2:
The patent applies pre-distortion to the input signal before amplification to pre-compensate for expected nonlinearities. This preliminary correction allows the amplifier to operate more efficiently without sacrificing output linearity, as the distortion is corrected in advance rather than requiring the amplifier to operate in a less efficient high-linearity mode.
3Use of energy by moving object
If power amplifier is biased for higher efficiency, then power consumption is reduced, but nonlinearity increases
Solution Approach 1:
The patent modifies the input signal parameters through digital pre-distortion to compensate for the increased nonlinearity that results from operating the power amplifier at higher efficiency bias points. The pre-distortion coefficients adjust the amplitude and phase of the input signal to counteract the amplifier's nonlinear behavior, maintaining output signal quality while enabling efficient operation.
Solution Approach 2:
The patent uses feedback from the actual output signal to continuously update and refine the pre-distortion coefficients. By comparing the distorted output with the expected output and adjusting the pre-distortion parameters accordingly, the system maintains accurate compensation for nonlinearities even as operating conditions change, enabling sustained high-efficiency operation with maintained linearity.
Data Source
AI summary
A system for data-based pre-distortion for a nonlinear power amplifier includes a digital pre-distortion (DPD) component, including a DPD processor and a DPD calibration engine, where the DPD processor applies a set of DPD coefficients to a digital baseband data signal, to generate a pre-distorted digital baseband data signal for conversion to a radio frequency (RF) signal and amplification by a nonlinear power amplifier (PA) to generate an RF output signal, where the DPD calibration engine compares a digitized, down-converted version of the RF output signal with the digital baseband data signal, to determine distortion coefficients of the nonlinear PA, and to update the set of pre-distortion coefficients in the DPD processor to compensate for the distortion coefficients of the non-linear PA, where data transmission is uninterrupted by the transmission of non-data calibration signals.