RF Power Amplifier Impedance Transformation for PAE-Linearity Tradeoff
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Solution Overview
Problem
Existing RF power amplifiers face challenges in achieving high power added efficiency (PAE) and linearity, particularly in handling OFDM modulated signals, as they require high-linearity power amplifiers that also optimize PAE, which is not effectively addressed by conventional Class A or Class AB amplifiers.
Innovation Solution
The RF power amplifier incorporates an impedance transformation circuit, a current unit gain amplifier, and an output match circuit, where the impedance transformation circuit adjusts input impedance to output impedance based on an impedance matching parameter, and the current unit gain amplifier determines a predetermined power gain value to enhance PAE and linearity, ensuring a linear relationship between output power and input current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If common source (CS) power amplifiers of Class A or Class AB are used to increase linearity, then linearity is improved, but power added efficiency deteriorates
Solution Approach 1:
The power amplifier is divided into multiple functional modules: an impedance transformation circuit for input matching, a common gate (CG) amplifier stage for voltage amplification, and an output matching circuit. This segmentation allows each module to be optimized independently, with the CG configuration providing inherent impedance transformation properties that improve both linearity and efficiency simultaneously
Solution Approach 2:
The patent transforms the input impedance of the CG amplifier from a capacitive value to a resistive value through the input matching circuit. This parameter transformation enables the amplifier to operate at optimal impedance points, improving power added efficiency while maintaining the linearity benefits of the CG configuration
2Use of energy by moving object
If impedance matching is optimized for maximum power transfer, then power added efficiency is improved, but linearity deteriorates
Solution Approach 1:
The patent introduces an intermediary impedance transformation stage between the signal source and the CG amplifier. This intermediary circuit transforms the source impedance to match the optimal input impedance of the CG amplifier, enabling maximum power transfer while the CG amplifier itself maintains linearity through its inherent circuit topology
Solution Approach 2:
The matching circuits are designed with dynamic impedance transformation capabilities, allowing the system to adapt impedance values across different operating conditions. This dynamic approach ensures optimal power transfer efficiency is maintained across varying signal levels while preserving linearity performance
3Power
If power gain is increased to improve signal strength, then output power is improved, but power added efficiency deteriorates
Solution Approach 1:
The patent employs periodic switching action through the common gate amplifier configuration, where the transistor operates in a switching-like manner during portions of the signal cycle. This periodic operation reduces the average power consumption while maintaining high output power delivery, thereby improving power added efficiency
Solution Approach 2:
The patent replaces traditional resistive voltage division methods with an inductive impedance transformation approach using the CG amplifier's inherent inductance. This substitution eliminates resistive power losses and achieves both high output power and high efficiency through reactive impedance matching
Data Source
AI summary
A radio frequency (RF) power amplifier is disclosed. The RF power amplifier includes an impedance transformation circuit, a current unit gain amplifier, and an output match circuit. The impedance transformation circuit receives a first input power signal and outputs a second input power signal correspondingly, wherein the impedance transformation circuit transforms an input impedance to an output impedance according to an impedance matching parameter for increasing power added efficiency of a pre-stage circuit. The current unit gain amplifier provides a linear transimpedance so as to transmit an input current to an output impedance, and then generate a linear output power for increasing power added efficiency of the current unit gain amplifier, wherein the impedance matching parameter is determined by a first system voltage, a second system voltage, and a predetermined power gain value.