Digital Pre-Distortion for Phased Arrays With Nonlinear Power Amplifiers
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Solution Overview
Problem
Wireless communication systems face challenges in reducing signal distortion caused by power amplifier nonlinearity, particularly when power amplifiers operate below saturation, leading to inefficiency and increased component costs.
Innovation Solution
The implementation of digital pre-distortion (DPD) techniques, including stochastic optimization and combined direct and indirect learning methods, to correct for nonlinearities in power amplifiers and antenna systems before signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If power amplifiers operate below saturation point to avoid nonlinearity, then signal distortion is reduced, but power efficiency deteriorates
Solution Approach 1:
The patent applies digital pre-distortion (DPD) to the input signal before it reaches the power amplifier. The pre-distortion processor intentionally distorts the signal in advance, so that when the nonlinear power amplifier processes it, the combined effect produces a linear output. This preliminary action allows the amplifier to operate at high power levels without causing harmful signal distortion.
Solution Approach 2:
The pre-distortion processor applies an inverse nonlinearity to the input signal that counteracts the expected nonlinearity of the power amplifier. By pre-applying the opposite distortion, the system cancels out the harmful effects of amplifier nonlinearity, enabling efficient operation at saturation while maintaining signal fidelity.
2Ease of manufacture
If low-cost power amplifiers are used to reduce component cost, then manufacturing cost is reduced, but nonlinearity increases
Solution Approach 1:
The pre-distortion processor acts as an intermediary between the signal source and the low-cost power amplifier. It compensates for the amplifier's nonlinearity by pre-distorting the signal, thereby enabling the use of inexpensive amplifiers without sacrificing signal quality. This intermediary processing layer masks the deficiencies of low-cost components.
Solution Approach 2:
The system creates a digital model or lookup table representation of the power amplifier's nonlinear characteristics through calibration. This copied behavioral model is then used by the pre-distortion processor to apply the appropriate compensation, allowing the system to replicate ideal linear behavior even with nonideal hardware.
3Use of energy by moving object
If power amplifiers operate at saturation to improve power efficiency, then power consumption is reduced, but signal distortion increases
Solution Approach 1:
The pre-distortion processor prepares the signal in advance by applying the inverse of the expected nonlinear distortion. This preliminary processing ensures that when the amplifier operates at saturation, the combined effect of pre-distortion and amplifier nonlinearity produces a linear output signal, eliminating distortion while maintaining high efficiency.
Solution Approach 2:
The system dynamically adjusts the pre-distortion parameters based on the operating conditions and amplifier characteristics. By changing the distortion compensation parameters in real-time, the system optimizes the trade-off between power efficiency and signal fidelity, allowing saturation operation with minimal distortion.
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 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. 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.