Adjustable Load Power Amplifier Linearity Control
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Solution Overview
Problem
Existing power amplifier systems face challenges in maintaining linearity and power control, especially in high peak-to-average ratio linear systems, leading to premature compression and excessive power drop under mismatch conditions, with current detection methods being ineffective and balanced power amplifiers adding complexity and efficiency losses.
Innovation Solution
A power amplifier system utilizing a first power detector and an adjustable load that provides an adjustable impedance at the output of the power amplifier, responsive to the power detector output, to improve linearity and power control, potentially using passive components or integrated within output impedance matching circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forward power detection using a power coupler and power detector is implemented, then constant output power can be maintained for different phases, but for high impedance phases the collector voltage must be significantly increased leading to premature power amplifier compression
Solution Approach 1:
The patent implements a feedback mechanism where the detected forward power signal is fed back to control the adjustable load impedance. The system continuously monitors the forward power output and adjusts the load impedance dynamically to maintain constant output power while preventing collector voltage excursions that cause compression
Solution Approach 2:
The patent employs a dynamically adjustable load impedance that changes based on the detected power level and phase conditions. Instead of using a fixed load, the system adaptively modifies the load impedance to optimize performance across different operating phases, preventing premature compression while maintaining constant output power
2Measurement precision
If a detector is implemented at the power amplifier output using collector voltage detection, then phase shift from matching circuitry is avoided, but excessive power drop under mismatch occurs
Solution Approach 1:
The patent introduces an intermediary adjustable load between the power amplifier output and the detection point. This adjustable load acts as a mediator that decouples the detection function from the power delivery function, allowing accurate power detection without the excessive power drops that occur with direct collector voltage detection under mismatch conditions
3Measurement precision
If current detection using a current mirror is implemented, then power detection is achieved, but for high impedance phases the current drops causing input power to increase leading to further power amplifier compression
Solution Approach 1:
The patent changes the detection parameter from current (which drops under high impedance) to forward power detection using a power coupler. By detecting power rather than current, and combining this with dynamic load impedance adjustment, the system avoids the current drop issue that leads to increased input power and further compression
4Stability of the object's composition
If a balanced power amplifier is used to compromise between power and linearity, then linearity improves, but complexity and physical size increase along with additional losses
Solution Approach 1:
The patent segments the power amplifier system into distinct functional blocks: a simple power amplifier stage, a power detection subsystem using a coupler and detector, and an adjustable load control subsystem. This segmentation allows each component to perform its function optimally without the complexity of a fully balanced architecture, achieving improved linearity through coordinated control rather than symmetric structure
Data Source
AI summary
A power amplifier system includes a first power detector configured to detect a forward power output of a power amplifier, the first power detector configured to provide a first power detector output and an adjustable load coupled to the output of the power amplifier and configured to receive the first power detector output, the adjustable load configured to provide an adjustable impedance at the output of the power amplifier in response to one of the output of the power amplifier and the first power detector output.