Envelope-Tracking Power Amplifier Matching Circuit for Linearity
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Solution Overview
Problem
Power amplifier modules in mobile communication devices face challenges in maintaining linearity while reducing power consumption, especially with high-speed data communication standards like HSUPA, LTE, and LTE-advanced, as the gain of the power amplifier circuit varies with source voltage, leading to increased costs due to the need for complex control circuits.
Innovation Solution
A power amplifier module configuration that includes a first power amplifier circuit, a second power amplifier circuit with a variable source voltage, and a matching circuit with capacitors and an inductor to decrease the gain of the first power amplifier circuit as the source voltage increases, thereby maintaining linearity without additional complex control circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the source voltage of the second power amplifier circuit is increased to enhance linearity, then the linearity is improved, but the gain of the first power amplifier circuit increases causing overall gain variation and increased device complexity
Solution Approach 1:
The matching circuit acts as an intermediary between the first and second power amplifier circuits. It includes capacitors connected in series between the power amplifier circuits and an inductor connected between a node between the capacitors and ground, forming a passive gain control mechanism that eliminates the need for additional active control circuits
Solution Approach 2:
The matching circuit changes the electrical parameters (impedance, gain) of the first power amplifier circuit in response to changes in the source voltage of the second power amplifier circuit. As the source voltage increases, the matching circuit automatically decreases the gain of the first power amplifier circuit, maintaining constant overall gain without requiring active control
2Use of energy by moving object
If envelope tracking control is implemented to reduce power consumption, then power efficiency is improved, but additional control circuits are required increasing cost and complexity
Solution Approach 1:
The matching circuit serves as a passive intermediary that automatically adjusts the gain of the first power amplifier circuit based on the source voltage level, eliminating the need for additional active control circuits while maintaining power efficiency through envelope tracking
Solution Approach 2:
The matching circuit provides self-service gain control by automatically responding to source voltage changes. The circuit configuration itself (capacitors and inductor arrangement) enables the gain adjustment function without requiring external control signals or additional control circuitry
Data Source
AI summary
Improvement in linearity is achieved at low costs in a power amplifier module employing an envelope tracking system. The power amplifier module includes a first power amplifier circuit that amplifies a radio frequency signal and that outputs a first amplified signal, a second power amplifier circuit that amplifies the first amplified signal on the basis of a source voltage varying depending on amplitude of the radio frequency signal and that outputs a second amplified signal, and a matching circuit that includes first and second capacitors connected in series between the first and second power amplifier circuit and an inductor connected between a node between the first and second capacitors and a ground and that decreases a gain of the first power amplifier circuit as the source voltage of the second power amplifier circuit increases.