Non-Constant Envelope Reference Signals for PA Nonlinearity Estimation

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Solution Overview

Problem

Wireless communication systems face inefficiencies due to nonlinear components like high-power amplifiers, which distort signals with high peak-to-average power ratio, leading to reduced power efficiency and the need for power back-off, and existing nonlinearity estimation methods are limited by data-driven approaches and constant envelope signals that prevent accurate estimation.

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 and perform digital pre- or post-distortion operations to adjust amplifier coefficients, thereby improving signal fidelity and power efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If power back-off is applied to reduce signal distortion from nonlinear components, then signal fidelity is improved, but power efficiency deteriorates

Engineering Contradiction:

Improvesignal fidelityVSAvoidpower efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies digital pre-distortion (DPD) to modify the signal before it enters the nonlinear power amplifier. By pre-compensating for the expected nonlinear distortion in the digital domain, the signal is conditioned to counteract the amplifier's nonlinear behavior, thereby maintaining signal fidelity without requiring power back-off and preserving power efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the receiver estimates nonlinearity characteristics of the transmitter's power amplifier and sends this information back to the transmitter. The transmitter uses this feedback to continuously adjust and refine the pre-distortion coefficients, enabling adaptive compensation that maintains signal fidelity while operating at optimal power levels.

Inventive Principle:

Principle #23Feedback

2Reliability

If constant envelope reference signals are used to avoid nonlinearity effects, then nonlinear distortion is reduced, but nonlinearity estimation capability is lost

Engineering Contradiction:

Improvenonlinearity avoidanceVSAvoidnonlinearity estimation accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

Instead of using constant envelope signals to avoid nonlinearity effects, the patent inverts the approach by deliberately using non-constant envelope reference signals that experience nonlinear distortion. This distortion is then measured and used to estimate the nonlinearity characteristics of the power amplifier, enabling the feedback mechanism to function effectively.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10707907B2System and method for nonlinearity estimation with reference signals

Publication Date: 2020.07.07 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.