Doherty Power Amplifier With Cascaded Auxiliary Stages and Delay Compensation
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Solution Overview
Problem
Conventional Doherty power amplifiers face inefficiencies due to premature active-load pulling by auxiliary power amplifiers before the main power amplifier reaches saturation, affecting overall efficiency and broadband performance.
Innovation Solution
The implementation of multiple stages of cascaded auxiliary power amplifiers and a delay device in the main power amplification branch to enable the auxiliary power amplifier to shut down ideally at a specified threshold, allowing the main power amplifier to approach saturation, thereby improving efficiency and reducing group delay impacts on broadband performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional Doherty power amplifier uses a single auxiliary power amplifier biased to class B or class C, then the auxiliary power amplifier can provide peak power amplification, but it starts to perform active-load pulling before the main power amplifier reaches saturation, causing the main power amplifier to not reach saturated state and reducing overall efficiency
Solution Approach 1:
The auxiliary power amplification function is divided into multiple stages (first auxiliary power amplifier and second auxiliary power amplifier), where each stage activates at different power levels. The first auxiliary power amplifier handles moderate peak power while the second handles higher peak power, creating a阶梯式 (step-wise) amplification approach that prevents premature active-load pulling and allows the main power amplifier to reach saturation properly.
Solution Approach 2:
The patent changes the operating parameters of auxiliary power amplifiers by introducing multiple stages with different activation thresholds and gain characteristics. The first auxiliary power amplifier is configured to activate at a lower power threshold with a specific gain, while the second auxiliary power amplifier activates at a higher threshold, creating a progressive parameter change that optimizes efficiency across different power back-off conditions.
2Loss of energy
If multiple stages of cascaded auxiliary power amplifiers are used, then the main power amplifier can reach saturation state and efficiency is improved, but the system complexity increases
Solution Approach 1:
The patent combines multiple auxiliary power amplifiers in a cascaded configuration where the first auxiliary power amplifier and second auxiliary power amplifier work together in sequence. This merging of multiple amplification stages achieves the desired efficiency improvement while managing complexity through a systematic cascaded architecture that integrates the auxiliary amplifiers with the main power amplifier and combiner network.
Data Source
Figure 1A~1C
Figure 1D~3
Figure 4~6
AI summary
A Doherty power amplifier (100) includes: a first amplification circuit (110), including a main power amplification branch and at least one auxiliary power amplification branch, where the main power amplification branch includes a first main power amplifier (111), and each auxiliary power amplification branch of the at least one auxiliary power amplification branch includes multiple levels of auxiliary power amplifiers (112, 113); a delay device (383), connected in the main power amplification branch, and configured to compensate for a delay difference between the main power amplification branch and the at least one auxiliary power amplification branch; a combiner network (140), configured to: perform impedance inversion on the first amplification circuit (110), and couple an output end of the main power amplification branch and an output end of the at least one auxiliary power amplification branch to a load (160); and a first power divider (130), connected to an input end of the main power amplification branch and an input end of the at least one auxiliary power amplification branch, and configured to allocate an input signal of the first power divider (130) to the main power amplification branch and the at least one auxiliary power amplification branch. The technical solutions can improve efficiency of the Doherty power amplifier (100).