Baseband Predistortion Linearization for Wideband Memory Effects
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Solution Overview
Problem
Existing baseband predistortion methods struggle to effectively compensate for both RF frequency response memory effects and bias-induced or thermal memory effects in multi-channel wideband wireless transmitters, leading to inefficiencies and computational complexity.
Innovation Solution
A piecewise pre-equalized lookup table (LUT) based digital predistortion system that compensates for electrical and thermal memory effects, reducing computational complexity and numerical instability while maintaining linearity performance comparable to memory polynomial PD algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If memory polynomial PD algorithms are used to compensate for memory effects, then linearity performance is improved, but computational complexity increases
Solution Approach 1:
The predistorter is divided into two independent functional blocks: a memoryless nonlinearity compensator and a memory effects compensator. This segmentation allows each block to be optimized separately, reducing the overall computational complexity while maintaining the linearity performance benefits of memory polynomial algorithms.
Solution Approach 2:
The memory effects compensation functionality is extracted from the complex memory polynomial algorithm and implemented as a separate FIR filter block. This extraction simplifies the main predistortion path while isolating the memory compensation function to a dedicated component with manageable computational requirements.
2Manufacturing precision
If Volterra filter structure is applied to compensate memory effects, then memory effects are compensated, but the number of optimization coefficients becomes very large
Solution Approach 1:
The patent replaces the complex Volterra filter with simpler, more efficient structures (memoryless polynomial PD and FIR filter) that achieve the same memory effects compensation with far fewer coefficients. This substitution uses computationally cheaper alternatives that maintain effectiveness while dramatically reducing complexity.
3Device complexity
If Hammerstein predistorter is used to reduce complexity, then computational complexity is reduced, but performance is compromised
Solution Approach 1:
The patent merges the advantages of memoryless polynomial predistortion (nonlinearity compensation) with FIR filter-based memory effects compensation into a unified two-block architecture. This combination achieves performance comparable to memory polynomial algorithms while maintaining the reduced complexity of the Hammerstein approach.
Solution Approach 2:
The system dynamically adapts the characteristics of each block based on the specific requirements of the power amplifier being linearized. The memoryless block handles instantaneous nonlinearity while the FIR block handles temporal memory effects, with both blocks working together to optimize performance for varying operating conditions.
Data Source
AI summary
An efficient baseband predistortion linearization method for reducing the spectral regrowth and compensating memory effects in wideband communication systems using effective multiplexing modulation technique such as wideband code division multiple access and orthogonal frequency division multiplexing is disclosed. The present invention is based on the method of piecewise pre-equalized lookup table based predistortion, which is a cascade of a lookup table predistortion and piecewise pre-equalizers.