Parallel Power Amplifier Architecture Without Load Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Doherty amplifiers suffer from load modulation, which adversely affects power handling and bandwidth capability, and exhibit reduced efficiency at higher output power back-off regions due to increased peak-to-average power ratio in communication signals.
Innovation Solution
A no-load-modulation, high-efficiency, broadband, multiclass power amplifier is designed with multiple amplifiers operating in parallel, featuring impedance-matching components and hybrid couplers to eliminate load modulation and enhance efficiency across a wide range of output power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional Doherty amplifier architecture is used, then power handling capability is achieved, but load modulation occurs which adversely affects bandwidth capability and efficiency
Solution Approach 1:
The amplifier is divided into multiple parallel circuit paths (main amplifier path and peaking amplifier paths) with independent control. Each path contains separate amplifiers and impedance-matching components, allowing independent optimization of each path's performance characteristics while maintaining overall power handling capability.
Solution Approach 2:
Impedance-matching components are introduced as intermediary elements between the amplifiers and the combining network. These components transform impedances to eliminate load modulation effects, serving as mediators that decouple the load variations from the amplifier stages and preserve bandwidth capability.
2Power
If conventional Doherty amplifier architecture is used, then power handling capability is achieved, but efficiency is reduced at higher output power back-off regions
Solution Approach 1:
The amplifier employs dynamic operation where peaking amplifiers are activated or deactivated based on the input signal level. At high power back-off regions, the main amplifier operates efficiently while peaking amplifiers remain idle. As power level increases, peaking amplifiers are dynamically engaged to maintain overall efficiency, creating a adaptive efficiency profile across different operating points.
Solution Approach 2:
The system changes operational parameters (amplifier activation states, impedance transformations) based on the operating point. Impedance-matching components dynamically adjust the load seen by each amplifier stage, optimizing efficiency at different power back-off levels by transforming impedances to maintain optimal operating conditions for the active amplifiers.
3Power
If multiple amplifiers operate in parallel to increase power output, then power handling is improved, but load modulation adversely affects performance
Solution Approach 1:
The parallel amplifier paths are designed with asymmetric impedance transformations. Each path has specifically designed impedance-matching components that present different impedance characteristics to the combining network. This asymmetric design ensures that load modulation effects are minimized in each path, as the impedance transformations are optimized for their specific operating conditions rather than being uniform across all paths.
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5A
AI summary
Apparatus and methods for a no-load-modulation power amplifier are described. No-load-modulation power amplifiers can comprise multiple amplifiers connected in parallel to amplify a signal that has been divided into parallel circuit branches. One of the amplifiers can operate as a main amplifier in a first amplification class and the remaining amplifiers can operate as peaking amplifiers in a second amplification class. The main amplifier can see essentially no modulation of its load between the power amplifier's fully-on and fully backed-off states. The power amplifiers can operate in symmetric and asymmetric modes. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained. Further improvements can be obtained by combining signals from the amplifiers with hybrid couplers.