Parallel IIR Predistortion Circuit for GaN Power Amplifier Memory Effects
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Solution Overview
Problem
Power amplifiers in communication systems exhibit nonlinearity, causing spectral growth and distortions that increase bit error rates and interfere with adjacent channels, which existing digital predistortion techniques struggle to fully address, especially with the increasing demands of new wireless applications.
Innovation Solution
A digital predistortion system utilizing multiple infinite impulse response (IIR) filters in parallel to compensate for different memory effects of gallium nitride (GaN) transistors, such as gate lag, drain lag, and thermal effects, to generate a predistortion signal that effectively linearizes the power amplifier, improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital predistortion techniques are used to linearize the power amplifier, then spectral growth and distortions are reduced, but it is challenging to meet the increasing performance requirements of new wireless applications
Solution Approach 1:
The patent divides the predistortion function into multiple parallel signal paths, each handling different aspects of the power amplifier's nonlinear behavior. The first path processes signals through a first infinite impulse response (IIR) filter, the second path through a second IIR filter, and the third path through a memory polynomial-based circuit, with each path contributing to overall linearization performance
Solution Approach 2:
The patent extends the predistortion approach by adding multiple signal paths with different filter types and orders, transforming a single-dimension solution into a multi-dimensional approach that can handle complex memory effects and nonlinearities in GaN power amplifiers
2Measurement precision
If multiple parallel signal paths with different IIR filters are used to compensate for different memory effects, then compensation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the memory effect compensation into distinct parallel paths, with each path dedicated to compensating for specific memory effects using appropriately configured IIR filters of different orders, allowing targeted compensation without requiring a single overly complex filter
Solution Approach 2:
Each signal path in the parallel configuration serves multiple functions: filtering, memory effect compensation, and signal processing, with the combined output providing comprehensive predistortion coverage for various types of nonlinearities
Data Source
AI summary
A digital predistortion (DPD) system (302B) includes an input (222) configured to receive a DPD input signal. The DPD system includes a first predistortion circuit (404) configured to provide a first signal path coupled to the input to generate a first predistortion signal (428). The first predistortion circuit includes a first infinite impulse response (MR) filter (416). A second predistortion circuit (406) is configured to provide a second signal path coupled to the input in parallel with the first signal path to generate a second predistortion signal (430). The second predistortion circuit includes a second MR filter (418). A combiner circuit (442) is configured to combine the first predistortion signal and the second predistortion signal to generate a DPD output signal (306).