Parallel Predistortion Amplifier for Power-Dependent Phase Compensation
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Solution Overview
Problem
Existing power amplifier circuits face limitations in maintaining signal quality across a wide range of operating conditions due to the mismatch in characteristics between the active feedforward predistorter and the final-stage power amplifier, particularly in frequency, temperature, and output region.
Innovation Solution
A power amplifier circuit with a distortion compensation amplifier circuit that includes two amplifiers with different gains and phases, connected in parallel, and a control circuit to adjust these gains based on input signal power, ensuring phase compensation across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an active feedforward predistorter with diode is used to compensate for nonlinearity of the final-stage power amplifier, then output linearity of the linear amplifier is improved, but operating conditions (frequency, temperature, output region) under which compensation effect is obtained are limited
Solution Approach 1:
The patent changes the device type from diode to bipolar transistor and modifies the circuit configuration to enable dynamic adaptation to different operating conditions (frequency, temperature, output region) while maintaining compensation effectiveness, thus expanding the applicable operating condition range
Solution Approach 2:
The patent introduces a control circuit that dynamically adjusts the predistorter's operation based on real-time detection of operating conditions, enabling the system to adapt to varying frequency, temperature, and output region conditions rather than being fixed for specific conditions
2Manufacturing precision
If a diode-based active feedforward predistorter is configured to match the final-stage power amplifier characteristics, then compensation effect is achieved, but the characteristics mismatch between diode and transistor limits the compensation effectiveness
Solution Approach 1:
The patent uses bipolar transistors in both the predistorter and the final-stage power amplifier, ensuring homogeneous device characteristics and eliminating the mismatch problem that occurred when using diodes with different characteristics than the transistor-based power amplifier
Solution Approach 2:
The patent employs a control circuit with detection means that monitors operating conditions and adjusts the predistorter accordingly, creating a feedback mechanism that maintains compensation accuracy across varying conditions rather than relying solely on fixed characteristic matching
Data Source
AI summary
A power amplifier circuit includes a distortion compensation amplifier circuit that includes a first amplifier that amplifies a first signal distributed from an input signal, and a second amplifier connected in parallel to the first amplifier, that amplifies a second signal distributed from the input signal and having a different phase from the first signal, and outputs an amplified signal obtained by combining a signal output from the first amplifier and the second amplifier, and an output amplifier circuit that outputs an output signal obtained by amplifying the amplified signal. The distortion compensation amplifier circuit further includes a control circuit that controls, based on power of the input signal, the first gain and the second gain to compensate for a change in a phase of the output amplifier circuit with respect to a change in the power of the signal input to the output amplifier circuit.