RF Predistortion with Memory Compensation for Power Amplifier Linearization
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Solution Overview
Problem
Power amplifiers in communication systems introduce non-linearity and memory effects, leading to distortion, particularly during amplitude modulation, which existing methods struggle to address efficiently without increasing amplifier size or power consumption.
Innovation Solution
A pre-distorter generates an error signal to compensate for non-linearity by distorting the input signal with a polynomial of envelope powers weighted by pre-distortion coefficients, using a polynomial generator and memory compensator module with feedforward and feedback mechanisms to address memory effects, and a spectral performance monitor to calculate error signals in the digital domain for rapid convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional baseband pre-distortion is used to reduce non-linearity, then distortion is reduced, but power consumption increases and system complexity increases due to digitization requirements
Solution Approach 1:
The patent replaces the conventional baseband digital domain pre-distortion approach with an RF domain implementation. Instead of digitizing signals at baseband and performing complex digital signal processing, the invention performs pre-distortion directly in the RF domain using analog circuitry, thereby eliminating the need for high-speed ADCs and reducing power consumption while maintaining distortion correction capability
Solution Approach 2:
The patent transitions the pre-distortion operation from the baseband dimension to the RF dimension. By performing pre-distortion at the RF carrier frequency rather than at baseband, the system avoids the power-consuming digitization step and achieves more efficient distortion correction with reduced system complexity
2Object-generated harmful factors
If conventional baseband pre-distortion is used to reduce non-linearity, then distortion is reduced, but device complexity increases due to digitization and analysis requirements
Solution Approach 1:
The patent replaces the complex baseband digital processing chain with a simpler RF domain analog implementation. By performing pre-distortion in the RF domain, the system eliminates high-speed ADCs, complex digital signal processors, and associated control logic, thereby reducing device complexity while maintaining effective distortion correction
3Object-generated harmful factors
If power amplifier operates in linear region below maximum power capacity to reduce distortion, then distortion is reduced, but amplifier efficiency decreases and system cost increases
Solution Approach 1:
The patent applies preliminary pre-distortion action to the input signal before it reaches the power amplifier. By pre-distorting the signal in advance to anticipate and counteract the amplifier's non-linear behavior, the system enables the power amplifier to operate at higher power levels (closer to saturation) while still producing linear output, thereby improving amplifier efficiency without sacrificing distortion performance
Solution Approach 2:
The patent applies preliminary anti-action by pre-distorting the input signal with an inverse of the expected non-linear distortion. This pre-applied opposite distortion counteracts the amplifier's non-linearity, allowing the amplifier to operate in its more efficient non-linear region while the pre-distortion compensates to deliver a linear output signal
Data Source
AI summary
A polynomial generator and memory compensator module is provided that includes: a first bank of delay filters for generating current and delayed versions of the envelope for an RF input signal and for the square of the envelope, a polynomial generator for generating polynomials using the current and delayed versions of the envelope, each polynomial being weighted according to pre-distortion weights; an adder for adding the polynomials to provide a pre-distortion signal for pre-distorting the RF input signal to provide a pre-distorted RF input signal such that a power amplifier amplifying the pre-distorted RF input signal provides an amplified RF output signal that reduces a non-linearity of the power amplifier; and a second bank of delay filters for generating delayed versions of the output signal, wherein the adder further adds the delayed versions of the output signal to the polynomials to provide the pre-distortion signal.