Reference Signal Nonlinearity Estimation for Amplifier Distortion

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Solution Overview

Problem

Wireless communication systems face inefficiencies due to nonlinear components like high-power amplifiers distorting signals with high peak-to-average power ratio, leading to reduced power efficiency, and existing methods for nonlinearity estimation are limited, especially for signals with high signal-to-noise ratios and higher modulation schemes.

Innovation Solution

A transmitter generates a reference signal with a non-constant envelope for nonlinearity estimation, allowing a receiver to estimate nonlinearity characteristics using a least-squares algorithm, which enables digital pre- and post-distortion operations to adjust amplifier coefficients, thereby improving signal fidelity and power efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If back off is applied to transmission power to reduce distortion from nonlinear components, then signal distortion is reduced, but power efficiency is reduced

Engineering Contradiction:

Improvesignal distortionVSAvoidpower efficiency

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent applies digital pre-distortion (DPD) operations before signal transmission to pre-compensate for nonlinear distortion. By estimating nonlinearity characteristics using reference signals with non-constant envelopes and applying correction in advance, the system eliminates the need for excessive back-off while maintaining signal fidelity and power efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the receiver estimates nonlinearity characteristics by comparing received reference signals with expected characteristics. These estimates are fed back to the transmitter to adjust pre-distortion parameters, creating a closed-loop system that optimizes both distortion reduction and power efficiency

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If signal preambles with constant envelope are used to avoid nonlinearity effects, then nonlinearity effects are avoided, but nonlinearity estimation is prevented

Engineering Contradiction:

Improvenonlinearity effectsVSAvoidnonlinearity estimation

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent inverts the conventional approach by deliberately using reference signals with non-constant envelopes instead of constant envelopes. This inversion allows the signals to experience nonlinearity effects that can then be measured and estimated, enabling the system to characterize and compensate for nonlinear distortion while maintaining efficient power operation

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11108419B2System and method for nonlinearity estimation with reference signals

Publication Date: 2021.08.31 QUALCOMM INC

AI summary

A transmitter may be configured to generate a reference signal having a non-constant envelope for nonlinearity estimation by a receiver. The transmitter may transmit the reference signal. A receiver may be configured to receive, from the transmitter, the reference signal having the non-constant envelope. The receiver may estimate at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. The receiver may transmit feedback based on the at least one nonlinearity characteristic and/or perform at least one digital post distortion (DPoD) operation based on the at least one nonlinearity characteristic.