Doherty Amplifier Bias Control for Faster Peak Amplifier Response
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Solution Overview
Problem
Existing Doherty amplifiers face challenges in maintaining high-quality radio frequency output signals due to slow response times in detecting saturation levels, leading to potential carrier amplifier saturation and reduced communication quality, especially when dealing with instantaneous power increases in radio frequency input signals.
Innovation Solution
A Doherty amplifier configuration that includes a carrier amplifier, a peak amplifier, a drive level detection circuit, and a control circuit to rapidly adjust the bias of the peak amplifier based on detected drive levels, improving response time and maintaining signal quality by removing DC components to prevent bias point fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If saturation detection is performed using bias circuits with response time of several tens of nanoseconds, then the circuit can detect carrier amplifier saturation, but the response time is too slow to maintain high-quality radio frequency output signals during instantaneous power increases
Solution Approach 1:
The patent introduces an intermediary detection mechanism that monitors the drive level signal before it causes carrier amplifier saturation. By detecting changes in the drive level signal that precede saturation, the system can trigger the peak amplifier earlier, avoiding the slow response of traditional saturation detection while maintaining accurate monitoring of the amplification process
Solution Approach 2:
The system performs preliminary detection of drive level changes before the carrier amplifier actually saturates. By monitoring the input signal level and predicting when saturation will occur, the peak amplifier can be activated in advance, eliminating the delay associated with detecting saturation after it has already occurred
2Adaptability or versatility
If the peak amplifier bias is controlled based on radio frequency input signal level detection, then the system can respond to power level changes, but the response speed is low and radio frequency output signal quality deteriorates
Solution Approach 1:
The patent replaces the mechanical/electrical detection method (monitoring radio frequency signal levels through bias circuits) with a signal-processing-based approach. By analyzing the drive level signal characteristics and detecting changes that indicate impending saturation, the system achieves faster response without the inherent delays of traditional RF signal monitoring methods
Data Source
AI summary
A Doherty amplifier includes a carrier amplifier amplifying a radio frequency signal, a peak amplifier amplifying a radio frequency signal and including a driver stage peak amplifier and a power stage peak amplifier receiving an output of the driver stage peak amplifier, a drive level detection circuit detecting a drive level of the carrier amplifier, a control circuit outputting a signal to set a bias of the driver stage peak amplifier based on a drive level signal indicating the drive level detected by the drive level detection circuit, and a generation circuit generating a current or a voltage in accordance with an operating state of the driver stage peak amplifier. An operating state of the power stage peak amplifier is controlled based on the current or the voltage generated by the generation circuit in accordance with the operating state of the driver stage peak amplifier.