Behavioral Digital Pre-Distortion for Phased-Array PA Nonlinearity
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Solution Overview
Problem
Wireless communication systems face challenges with signal distortion due to power amplifier nonlinearity, leading to inefficient power consumption and increased costs, especially with low-cost amplifiers exhibiting more nonlinearity and higher power consumption.
Innovation Solution
Implementing a digital pre-distortion system that includes a pre-distortion actuator using behavioral models or generalized memory functions, coupled with an adaptation engine to dynamically adapt and correct for nonlinearities in power amplifiers and antennas, thereby compensating for signal distortions before transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power amplifiers are driven into saturation to improve power efficiency, then power consumption is reduced, but signal distortion increases due to nonlinear characteristics
Solution Approach 1:
The system applies digital pre-distortion to the input signal before amplification, introducing an opposite nonlinearity that cancels out the amplifier's nonlinearity. This preliminary counteraction allows the amplifier to operate in saturation while maintaining linear output characteristics, resolving the contradiction between power efficiency and signal fidelity.
Solution Approach 2:
The system performs characterization of the power amplifier's nonlinear behavior in advance and stores correction parameters in lookup tables. These pre-computed correction values are applied during signal transmission, enabling the amplifier to operate efficiently in saturation without real-time complex calculations, thus maintaining both power efficiency and signal quality.
2Ease of manufacture
If low-cost power amplifiers are used to reduce manufacturing costs, then device cost is reduced, but nonlinearity increases leading to higher signal distortion
Solution Approach 1:
The system enables low-cost power amplifiers to self-correct their inherent nonlinearities through digital pre-distortion. Each amplifier is individually characterized to create device-specific lookup tables that compensate for its unique nonlinearity profile, allowing inexpensive amplifiers to achieve performance comparable to expensive linear amplifiers without requiring costly hardware upgrades.
3Object-affected harmful factors
If power amplifiers operate below saturation to maintain signal linearity, then signal quality is improved, but power efficiency decreases due to increased power consumption
Solution Approach 1:
By applying pre-distortion correction to the input signal, the system counteracts the amplifier's nonlinear behavior, allowing operation in the high-efficiency saturation region while maintaining output linearity. This eliminates the need to operate below saturation, thereby resolving the trade-off between signal quality and power consumption.
4Object-affected harmful factors
If digital pre-distortion with behavioral models is implemented to correct nonlinearity, then signal fidelity is improved, but device complexity increases
Solution Approach 1:
The system performs amplifier characterization and generates lookup tables in advance, storing pre-computed correction parameters. During operation, the system simply retrieves and applies these pre-stored values rather than performing complex real-time calculations, significantly reducing computational complexity while maintaining effective nonlinearity compensation.
Solution Approach 2:
The system replaces complex real-time mathematical modeling and computation with simplified lookup table retrieval and interpolation. This substitution of complex computational mechanics with simpler data access operations reduces processing requirements and device complexity while maintaining correction effectiveness.
Data Source
AI summary
A wireless communications system includes a pre-distortion actuator configured to receive a carrier-modulated signal and convert the carrier-modulated signal into an output signal, the pre-distortion actuator comprising a behavioral model that models a transmit chain of the system including at least one amplifier and at least one antenna and predict an input-output relationship of the transmit chain of the system between an input to the transmit chain to an output of the transmit chain. The system includes a phased antenna array configured to transmit the output signal. The phased antenna array includes a plurality of antenna elements, each antenna element electrically coupled to a respective power amplifier. The pre-distortion actuator is configured to generate the output signal by applying a correction to the carrier-modulated input signal that cancels out nonlinearities The behavioral model is updated based on feedback from a receiver from a previous output signal transmitted to the receiver.