GaN MMIC Power Amplifier With Digital Gain Control for Linearity

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Solution Overview

Problem

FET-based distributed power amplifiers in microwave monolithic integrated circuits (MMICs) suffer from large gain variation and leakage, leading to degraded linearity and distorted output signals due to low early voltage, which affects the quality of amplified signals.

Innovation Solution

A broadband MMIC power amplifier is developed, incorporating a distributed pre-driver with a digital variable attenuator and an integrated coupler and detector unit, along with a feedback control loop, utilizing GaN-based technology to enhance linearity and gain control, featuring a GaN-based 1×N switch and a field programmable gate array for gain control, and employing a digital pre-distorter to suppress memory effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If FET-based distributed amplifiers are used in MMICs, then broadband amplification is achieved, but gain variation and leakage occur leading to degraded linearity

Engineering Contradiction:

Improvebroadband amplification capabilityVSAvoidlinearity and signal quality

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces traditional FET-based distributed amplification with a resonant tunneling diode (RTD) based amplification system. RTDs utilize quantum mechanical tunneling effects to achieve negative resistance characteristics, enabling broadband amplification while maintaining superior linearity and reducing gain variation compared to conventional FET implementations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the fundamental operating parameters by using RTD devices with negative differential resistance characteristics instead of positive resistance FETs. This parameter change enables the amplifier to operate with improved gain stability and reduced leakage across broadband frequencies, directly addressing the linearity issues of conventional designs.

Inventive Principle:

Principle #35Parameter changes

2Power

If conventional FET distributed amplifiers are employed, then power amplification is provided, but linearity degrades due to low early voltage

Engineering Contradiction:

Improvepower amplification capabilityVSAvoidlinearity

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent substitutes FET-based power amplification with RTD-based power amplification. The resonant tunneling diode's unique negative resistance region enables power amplification with inherently better linearity characteristics, eliminating the early voltage limitations that plague conventional FET amplifiers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If FET based distributed amplifiers are used, then amplification is achieved, but leakage occurs causing distorted output signals

Engineering Contradiction:

Improveamplification functionVSAvoidleakage and signal distortion

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention replaces FET-based amplification with RTD-based amplification to eliminate leakage issues. The RTD's operation in the negative differential resistance region provides a more controlled current-voltage characteristic that reduces unwanted leakage paths and prevents signal distortion while maintaining amplification functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7508267B1GaN based digital controlled broadband MMIC power amplifier

Publication Date: 2009.03.24 ROCKWELL COLLINS INC

AI summary

A power amplifier comprises a distributed pre-driver, digital signal adjuster, a distributed high power amplifier; and an integrated coupler-detector unit. The distributed pre-driver, the digital signal adjuster, the distributed high power amplifier and the integrated coupler-detector unit are formed at an interface of a Gallium Nitride layer and an Aluminum Gallium Nitride layer of a monolithic microwave integrated circuit device.