Two-Stage Doherty Peaking Amplifier for High Gain and Bandwidth
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Solution Overview
Problem
Conventional Doherty amplifiers face challenges in achieving high efficiency and gain performance while maintaining bandwidth, particularly in high-speed, high-power applications, with asymmetrical and multi-way configurations leading to undesirable bandwidth reductions.
Innovation Solution
Incorporating a two-stage peaking amplifier configuration in the Doherty amplifier, where both stages are of the same design and biased to turn on later, combined with an RF coupler and optimized impedance-matching components to compensate for signal delay, allowing for higher gain and improved efficiency without significant bandwidth reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If asymmetrical or multi-way Doherty amplifier configurations are used to improve efficiency, then power back-off efficiency is improved, but bandwidth is reduced
Solution Approach 1:
The peaking amplifier is divided into two separate stages (first peaking amplifier and second peaking amplifier) that operate in sequence. This segmentation allows each stage to contribute to efficiency improvement while maintaining the overall bandwidth performance of the amplifier system, resolving the contradiction between efficiency and bandwidth.
Solution Approach 2:
The patent transitions from conventional single-stage or asymmetrical configurations to a two-stage peaking amplifier architecture. This dimensional change in the amplifier structure enables simultaneous achievement of high power back-off efficiency and preserved bandwidth by distributing the amplification function across two stages with different turn-on characteristics.
2Power
If higher gain is achieved through amplifier configuration, then signal amplification is improved, but efficiency deteriorates
Solution Approach 1:
The first peaking amplifier is configured to turn on before the second peaking amplifier, creating a preliminary amplification stage. This preliminary action allows the system to achieve higher overall gain while maintaining efficiency by having amplifiers activate at different power levels rather than simultaneously at high power.
Solution Approach 2:
The patent employs dynamic biasing where the two peaking amplifiers are configured to turn on at different times based on the input signal power level. This dynamic operation allows the system to optimize both gain and efficiency by having the first peaking amplifier handle lower power levels and the second peaking amplifier handle higher power levels.
3Power
If signal delay compensation is implemented to improve performance, then gain and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent introduces asymmetry in the biasing configuration of the two peaking amplifiers, with different turn-on thresholds and timing characteristics. This asymmetric design enables signal delay compensation and performance optimization without requiring complex additional components, as the complexity is managed through biasing design rather than additional circuitry.
Data Source
AI summary
Apparatus and methods for an improved-efficiency Doherty amplifier are described. The Doherty amplifier may include a two-stage peaking amplifier that transitions from an “off” state to an “on” state later and more rapidly than a single-stage peaking amplifier used in a conventional Doherty amplifier. The improved Doherty amplifier may operate at higher gain values than a conventional Doherty amplifier, with no appreciable reduction in signal bandwidth.