Doherty Power Amplifier Bias Control for Variable Back-Off Efficiency
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Solution Overview
Problem
Existing power amplifiers struggle to maintain efficiency when faced with large amplitude variations and wide frequency band signals, particularly in multilevel modulation, leading to inefficiencies due to unadjusted back-off amounts.
Innovation Solution
A power amplifying circuit with a Doherty configuration, including a carrier and peaking amplifier group, where the number of amplifiers in each group is adjusted based on input signal characteristics, using a bias control circuit to manage bias signals and a power supply circuit for multilevel voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the supply voltage is changed according to the power level of the input signal, then the efficiency of the power amplifier is improved, but the adjustment cannot follow the variation of the input signal when the amplitude variation is large or the frequency band width is wide
Solution Approach 1:
The power amplifier is divided into multiple amplifier units that can be independently controlled. The control unit selectively activates or deactivates specific amplifier units based on the input signal characteristics, enabling fine-grained adaptation to large amplitude variations and wide frequency bands while maintaining high efficiency through optimized supply voltage allocation.
2Productivity
If multilevel modulation control is used to increase communication speed, then the channel band width is expanded, but the back-off amount increases and the efficiency of the power amplifier cannot be maintained
Solution Approach 1:
The system dynamically adjusts the operating state of amplifier units based on real-time detection of input signal characteristics including modulation scheme and back-off amount. The control unit modifies the supply voltage and activates/deactivates amplifier units adaptively, allowing the power amplifier to maintain high efficiency across varying communication speeds and modulation levels.
3Productivity
If the quantity of symbols in multilevel modulation increases to improve data rate, then the back-off amount increases, but the existing configuration cannot adjust the back-off amount and efficiency decreases
Solution Approach 1:
The control unit detects the input signal characteristics including the quantity of symbols used in multilevel modulation and the resulting back-off amount. Based on this feedback, the system adjusts the supply voltage and selectively activates amplifier units to optimize efficiency for the current data rate requirement, preventing efficiency degradation as data rate increases.
Data Source
AI summary
A power amplifying circuit includes a splitter connected to an input terminal, a combiner connected to an output terminal, a carrier amplifier group, a peaking amplifier group, a phase shifter, and a bias control circuit. The splitter splits an input signal from the input terminal for two paths. The carrier amplifier group is connected to one of the two paths of the splitter. The phase shifter is connected between the carrier amplifier group and the combiner. The peaking amplifier group is connected between another of the two paths of the splitter and the combiner. The bias control circuit supplies bias signals to each amplifier group. At least one of the amplifier groups includes a plurality of amplifiers. The control circuit changes a quantity of amplifiers to use in each amplifier group by adjusting a level of the bias signal being supplied to each amplifier.