Multistage Amplifier Impedance Matching at the PAE Transition Region
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Solution Overview
Problem
Conventional power amplifiers, especially those used in space vehicles, face challenges with power efficiency, size, complexity, and poor amplitude modulation to amplitude modulation (AM-AM) and amplitude modulation to phase modulation (AM-PM) transfer characteristics, limiting their effectiveness in amplifying high-frequency signals like those in microwave and millimeter wave frequency bands.
Innovation Solution
A multistage power amplifier design where each stage operates at or near its power-added efficiency (PAE) peak, with carefully matched output impedance and biased drive circuits to achieve efficient power transfer and minimize distortion, utilizing gallium arsenide substrates and Field Effect Transistors (FETs) for efficient power amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conduction angle biasing is used to improve power efficiency, then power efficiency is improved, but AM-AM and AM-PM transfer characteristics deteriorate
Solution Approach 1:
The amplifier is divided into multiple stages, each operating at different conduction angles optimized for their specific function. The first stage operates at a higher conduction angle for linearity, while subsequent stages operate at lower conduction angles for efficiency, with each stage contributing to the overall power efficiency improvement without sacrificing AM-AM and AM-PM characteristics
Solution Approach 2:
The invention changes the operating parameters of each amplifier stage by biasing them to operate at or near their PAE peak in the linear-compression transition region. This parameter optimization allows each stage to achieve both good power efficiency and desirable AM-AM and AM-PM transfer characteristics simultaneously
2Loss of energy
If conventional power efficient amplifiers are used, then power efficiency is improved, but device complexity and size increase
Solution Approach 1:
The amplifier system is segmented into multiple manageable stages, each with simplified design requirements. By dividing the overall amplification function into discrete stages with specific operating points, the total complexity is distributed and reduced compared to a single complex conventional amplifier design
Solution Approach 2:
Each amplifier stage is biased to operate at or near its PAE peak, optimizing the operating parameters to achieve high power efficiency without requiring complex conventional architectures. This parameter optimization simplifies the overall design while maintaining efficiency
3Manufacturing precision
If amplifiers are operated in linear region, then AM-AM and AM-PM transfer characteristics are improved, but power efficiency deteriorates
Solution Approach 1:
The invention changes the operating parameters by biasing amplifiers to operate at or near their PAE peak, which is located in the linear-compression transition region. This parameter change allows the amplifiers to operate in a regime that provides both good AM-AM and AM-PM transfer characteristics and high power efficiency, resolving the traditional trade-off between linearity and efficiency
Data Source
AI summary
A multistage amplifier and design method are disclosed. The multistage amplifier has a plurality of amplifier stages, each stage having an amplifier designed and biased to operate at or near the amplifier's power added efficiency (PAE) peak. The PAE peak of each of the amplifier is at or near the amplifiers linear-compression transition region, providing a multistage power amplifier that is power efficient and has desirable amplitude to amplitude and amplitude to phase power transfer characteristics. The amplifier is designed by matching the output impedance of a final stage with a load. Amplifier stages are iteratively designed from the last stage to the first. At each stage, an amplifier and drive circuit are designed. The drive circuit and amplifier are designed to provide each stage with output impedance matched to the input impedance of the following stage and to operate at or near the PAE peak of the amplifier.