RF Power Amplifier Predistortion for GaN Charge Trapping

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Solution Overview

Problem

GaN-based power semiconductor devices suffer from narrowband distortion due to charge trapping effects, leading to inefficiencies and increased complexity in digital predistortion (DPD) systems, which are costly and power-consuming, especially when addressing long-time constant charge trapping effects.

Innovation Solution

A radio frequency (RF) power semiconductor device employing a first non-linear filter network with infinite impulse response (IIR) filters, such as Laguerre filters, to correct narrowband distortion and a second non-linear filter network with finite impulse response (FIR) filters, like Generalized Memory Polynomial (GMP) filters, to address broadband distortion, reducing the need for extensive hardware and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If digital predistortion (DPD) systems are used to compensate for charge trapping effects in GaN-based power amplifiers, then narrowband distortion is corrected, but the system complexity and power consumption increase significantly

Engineering Contradiction:

Improvedistortion compensationVSAvoidDPD system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The DPD system is segmented into two distinct filter networks: a first non-linear filter network (using IIR/Laguerre filters) specifically targeting narrowband distortion from charge trapping effects, and a second non-linear filter network (using FIR/GMP filters) handling broadband distortion. This segmentation allows each network to be optimized for its specific function, reducing the overall complexity compared to a single comprehensive DPD system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention extracts and isolates the charge trapping effect compensation function into a dedicated first non-linear filter network with IIR filters. By separating this specific function from the general broadband distortion compensation, the system can address long-time constant effects without requiring the entire DPD system to handle all distortion types, thereby reducing overall system complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If extensive DPD hardware is deployed to address long-time constant charge trapping effects, then distortion compensation improves, but power consumption increases

Engineering Contradiction:

Improvecharge trapping compensationVSAvoidDPD power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The first non-linear filter network is designed with specific local quality characteristics using IIR filters that are particularly suited for modeling long-time constant effects. This localized optimization allows the system to efficiently handle charge trapping effects without deploying extensive hardware across the entire signal processing chain, thereby reducing power consumption while maintaining effective compensation.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a single filter network is used for both narrowband and broadband distortion, then device complexity is reduced, but distortion compensation precision deteriorates

Engineering Contradiction:

Improvefilter network structureVSAvoiddistortion compensation precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The distortion compensation function is segmented into two specialized filter networks: the first network using IIR/Laguerre filters optimized for narrowband charge trapping effects, and the second network using FIR/GMP filters optimized for broadband distortion. This segmentation ensures that each network can be precisely tuned for its specific distortion type, maintaining high compensation precision while keeping individual network complexities manageable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each filter network is designed with local quality optimized for its specific function: IIR filters provide precise modeling for long-time constant narrowband effects, while FIR filters provide accurate broadband characterization. This localized optimization ensures high precision for each distortion type without requiring either network to be excessively complex.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11533070B2Systems and methods of compensating for narrowband distortion in power semiconductor devices

Publication Date: 2022.12.20 ANALOG DEVICES INT UNLTD CO

AI summary

Some embodiments herein describe a radio frequency power semiconductor device that include a first non-linear filter network for compensating for lower frequency noise of a power amplifier. The first non-linear filter network can include a plurality of infinite impulse response filters and corresponding corrective elements to correct for a non-linear portion of the power amplifier. The radio frequency power semiconductor device can further include a second non-linear filter network for compensating for broadband distortion. The second non-linear filter network can be connected in parallel to the first non-linear filter network. The broadband distortion can include digital predistortion and the narrowband distortion can include charge trapping effects. The first non-linear filter network can comprise Laguerre filters. The second non-linear filter network can comprise general memory polynomial filters.