Doherty Amplifier Bias Control for Fast Peak Amplifier Activation
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Solution Overview
Problem
Doherty amplifier circuits face challenges in maintaining high-frequency output signal quality due to slow response times in detecting saturation, leading to potential carrier amplifier saturation and decreased communication quality, especially with momentary power increases in high-frequency signals.
Innovation Solution
A Doherty amplifier circuit configuration that includes a carrier amplifier, a peak amplifier, first and second bias circuits, and a control circuit that rapidly adjusts bias based on the input high-frequency signal and drive level detection, preventing carrier amplifier saturation through a detection circuit that quickly responds to changes in signal power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias circuit detects saturation of a carrier amplifier to control the peak amplifier bias, then the peak amplifier can be activated to prevent saturation, but the response time is several tens of nanoseconds which is too slow for momentary power increases
Solution Approach 1:
The control circuit predicts the need for peak amplifier activation by detecting the input signal power level before the carrier amplifier actually saturates. By using the relationship between input signal level and carrier amplifier drive level, the system takes preliminary action to adjust the peak amplifier bias before saturation occurs, eliminating the delay inherent in saturation-detection methods.
Solution Approach 2:
The invention replaces the mechanical/electrical saturation detection mechanism with a signal-level-based control mechanism. Instead of waiting for the carrier amplifier to physically saturate and then detecting it, the system substitutes a control approach that uses input signal power detection and drive level relationships to predict and prevent saturation, achieving much faster response.
2Speed
If the peak amplifier bias is controlled based on the level of the high frequency input signal detected by the bias circuit, then the response can be faster, but the response speed is still limited by the bias circuit detection capability
Solution Approach 1:
The control circuit uses feedback from the carrier amplifier's drive level detection to adjust the peak amplifier bias. By monitoring the drive level of the carrier amplifier and using this information to control the peak amplifier bias in real-time, the system achieves both fast response and reliable output signal quality. The feedback loop ensures that the peak amplifier is activated at the optimal moment based on actual carrier amplifier performance.
3Use of energy by moving object
If the carrier amplifier operates at saturation to maintain high efficiency, then power efficiency is improved, but the output signal quality decreases when saturation occurs during momentary power increases
Solution Approach 1:
The invention dynamically adjusts the operating state of the amplifier system by controlling when the peak amplifier activates based on input signal power levels. Instead of the carrier amplifier statically operating at saturation, the system uses dynamic control to transition between carrier amplifier-only operation and combined carrier-peak amplifier operation, maintaining high efficiency while preventing quality degradation during momentary power increases.
Data Source
AI summary
A Doherty amplifier circuit includes a carrier amplifier that amplifies an input high frequency signal, a peak amplifier that amplifies an input high frequency signal, a first bias circuit that applies a bias to the carrier amplifier, a second bias circuit that applies a bias to the peak amplifier, and a control circuit that controls the second bias circuit on the basis of an input high frequency signal and a signal indicating a drive level of the carrier amplifier.