Digital Pre-Distortion Feedback for Nonlinear Power Amplifiers
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Solution Overview
Problem
Wireless communication systems face inefficiencies due to power amplifier nonlinearity, leading to signal distortion and high power consumption, especially in low-cost amplifiers, which also exhibit more nonlinearity and result in increased component costs.
Innovation Solution
Implementing digital pre-distortion (DPD) techniques using a pre-distortion actuator with behavioral models or generalized memory functions, coupled with adaptation engines that apply corrections to carrier-modulated signals to cancel out nonlinearities associated with power amplifiers and antennas, allowing for dynamic adaptation based on feedback to maintain accurate compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If power amplifier operates below saturation point to maintain linearity, then signal distortion is reduced, but power efficiency deteriorates
Solution Approach 1:
The system applies digital pre-distortion to the input signal before it reaches the power amplifier. The pre-distortion actuator modifies the signal in advance to compensate for the anticipated nonlinearity of the amplifier, allowing the amplifier to operate in its nonlinear saturation region while the overall system maintains linearity. This resolves the contradiction by preparing the signal beforehand rather than relying on the amplifier's linear region operation.
Solution Approach 2:
The pre-distortion actuator introduces an opposite distortion to the input signal that counteracts the expected nonlinearity of the power amplifier. By applying this preliminary anti-action, the signal is pre-compensated so that when it passes through the nonlinear amplifier, the combined effect produces a linear output, enabling efficient saturation operation without signal distortion.
2Use of energy by moving object
If power amplifier operates in saturation region to improve power efficiency, then power consumption is reduced, but signal distortion increases
Solution Approach 1:
The pre-distortion actuator modifies the input signal in advance to account for the amplifier's nonlinear saturation characteristics. By pre-compensating the signal with opposite distortion, the system enables the amplifier to operate efficiently in saturation while maintaining overall signal linearity through the combined pre-distortion and amplifier response.
Solution Approach 2:
The adaptation engine continuously monitors the amplifier's output and adjusts the pre-distortion parameters accordingly. This feedback mechanism ensures that the pre-distortion compensation remains accurate even as the amplifier's nonlinear characteristics change with operating conditions, maintaining signal linearity while operating in the efficient saturation region.
3Ease of manufacture
If low-cost power amplifiers are used to reduce component costs, then device cost is reduced, but nonlinearity increases
Solution Approach 1:
The low-cost power amplifier is equipped with a pre-distortion actuator and adaptation engine that automatically compensate for its inherent nonlinearities. The system measures its own output characteristics and adjusts the pre-distortion parameters accordingly, enabling the inexpensive amplifier to achieve performance comparable to expensive linear amplifiers without requiring manual calibration or replacement.
Solution Approach 2:
The pre-distortion actuator dynamically adjusts signal parameters based on the amplifier's measured nonlinear characteristics. By changing the pre-distortion parameters to match the specific amplifier's behavior, the system compensates for the increased nonlinearity of low-cost amplifiers, enabling their use without sacrificing signal quality.
Data Source
AI summary
A wireless communications system includes a stochastic pre-distortion actuator configured to receive a carrier-modulated signal and convert the carrier-modulated signal into an output signal. The system includes one or more antennas configured to receive the output signal and transmit the output signal, one or more power amplifiers electrically coupled between the pre-distortion actuator and the one or more antennas and a receiver configured to receive the output signal over-the-air and generate feedback based on the output signal. The pre-distortion actuator is configured to generate the output signal by applying a correction to the carrier-modulated signal that cancels out nonlinearities associated with the one or more antennas and/or the one or more power amplifiers. The pre-distortion actuator is configured based on the feedback.