Doherty Power Amplifier Gain Control for Linear Output
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Solution Overview
Problem
Doherty amplifiers face challenges in achieving a linear input-output characteristic due to manufacturing variations that can cause the peaking amplifier to activate after the carrier amplifier has reached saturation, leading to oscillation and suboptimal performance.
Innovation Solution
A power amplifier circuit with a variable power splitter circuit, a carrier circuit, a peaking circuit, and a gain control circuit that adjusts the power of the signal split by the peaking amplifier based on the saturation level of the target carrier amplifier, preventing the increase in the bandpass characteristic of the peaking amplifier and thus avoiding oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the peaking amplifier is configured to activate at a relatively high power level, then the carrier amplifier can reach saturation for better efficiency, but the peaking amplifier starts amplification after saturation causing non-linear input-output characteristic
Solution Approach 1:
The patent applies preliminary action by detecting the saturation level of the carrier amplifier in advance and proactively adjusting the peaking amplifier's activation threshold before the actual saturation occurs. This allows the system to prepare the peaking amplifier for timely activation, ensuring smooth transition and maintaining linear input-output characteristic while preserving carrier amplifier efficiency.
2Reliability
If the bandpass characteristic of the peaking amplifier is increased to ensure timely activation, then the peaking amplifier activates before carrier saturation, but the output from the carrier amplifier passes through the closed circuit and enters the carrier amplifier causing oscillation
Solution Approach 1:
The patent implements feedback by continuously monitoring the saturation level of the carrier amplifier and using this information to dynamically adjust the peaking amplifier's activation threshold. This closed-loop control ensures the peaking amplifier activates at the precise moment needed without excessive bandpass characteristic increase, preventing oscillation while maintaining accurate activation timing.
Solution Approach 2:
The patent applies dynamics by making the peaking amplifier's activation threshold adjustable rather than fixed. The threshold is dynamically modified based on the detected saturation level of the carrier amplifier, allowing the system to adapt to varying operating conditions and prevent oscillation while ensuring timely activation.
3Productivity
If the peaking amplifier activates after carrier saturation due to manufacturing variations, then the carrier amplifier operates in saturation for better efficiency, but the Doherty amplifier fails to achieve linear input-output characteristic
Solution Approach 1:
The patent uses feedback to detect the actual saturation level of the carrier amplifier and adjusts the peaking amplifier's activation threshold accordingly. This compensates for manufacturing variations in the peaking amplifier's activation characteristics, ensuring consistent linear input-output performance across different devices while maintaining carrier amplifier efficiency.
Solution Approach 2:
The patent changes the activation threshold parameter of the peaking amplifier based on the detected saturation level of the carrier amplifier. This dynamic parameter adjustment compensates for manufacturing variations and ensures the peaking amplifier activates at the correct power level regardless of initial device characteristics.
Data Source
AI summary
A power amplifier circuit includes: a variable power splitter circuit that splits a first signal into a second and a third signal, the third signal being out of phase with the second signal, and increases or decreases first power of the third signal in response to a control signal; a carrier circuit including carrier amplifiers, the carrier circuit amplifies the second signal and output the amplified second signal; a peaking circuit including one or more peaking amplifiers, the peaking circuit amplifies the third signal and outputs the amplified third signal; and a control circuit that outputs to the variable power splitter circuit the control signal based on a saturation level of a target carrier amplifier, the target carrier amplifier being a carrier amplifier positioned closest to the output among the one or more carrier amplifiers in the carrier circuit.