Power Amplifier DPD for Charge Trapping Compensation
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Solution Overview
Problem
Existing radio frequency communication systems face challenges in compensating for charge trapping effects in power amplifiers, particularly in GaN-based devices, which result in transconductance frequency dispersion, current collapse, and restricted microwave output power, leading to complex and costly computational solutions that are impractical for transceivers.
Innovation Solution
Implementing a digital pre-distortion (DPD) system with parallel non-linear filters, including Laguerre filters for narrowband distortion and Generalized Memory Polynomial (GMP) filters for broadband distortion, to accurately align observations and correct for charge trapping effects without decimation, reducing computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex computational solutions are used to compensate for charge trapping effects in power amplifiers, then compensation accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The compensation system is segmented into two parallel filter paths: a first non-linear filter for narrowband distortion compensation and a second non-linear filter for broadband distortion compensation. This segmentation allows each filter to specialize in specific frequency ranges, improving overall compensation accuracy while keeping individual filter complexities manageable.
Solution Approach 2:
The system dynamically adapts to different distortion characteristics by selectively engaging appropriate filter paths. The parallel architecture enables dynamic switching between narrowband and broadband compensation modes based on the specific charge trapping effects present, optimizing the balance between accuracy and computational load.
2Productivity
If decimation is used to reduce computational complexity, then processing speed is improved, but signal quality deteriorates
Solution Approach 1:
Instead of applying decimation to the entire signal processing chain, the system applies partial processing only where necessary - using non-linear filters selectively for narrowband and broadband distortion components. This partial action approach maintains signal quality by avoiding unnecessary downsampling while still achieving computational efficiency in the distortion compensation paths.
3Measurement precision
If parallel filter paths are used to compensate for different distortion types, then compensation accuracy is improved, but device complexity increases
Solution Approach 1:
The parallel filter architecture implements multi-functionality by having each filter path handle specific distortion types: the first non-linear filter addresses narrowband distortion while the second handles broadband distortion. This universal approach allows a single system to compensate for multiple distortion mechanisms simultaneously, improving accuracy without requiring separate dedicated systems for each distortion type.
Data Source
AI summary
Systems and methods for compensating a transmit signal for charge trapping effects of a power amplifier are provided. In certain embodiments, a non-linear filter is trained based on time aligning a first set of observations taken from digital transmit data prior to conversion to a radio frequency transmit signal, and a second set of observations taken from an output of a power amplifier that amplifies the radio frequency transmit signal. In certain implementations, the first set of observations and the second set of observations are obtained without decimation. Rather, decimation is provided after timing alignment. By implementing the DPD system in this manner, signal data is not lost by decimation and more accurate timing alignment between the sets of observations is achieved.