Dynamic Doherty PA Biasing for High-PAPR Efficiency and Linearity
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Solution Overview
Problem
Conventional power amplifiers face inefficiencies when amplifying RF signals with high peak to average power ratio (PAPR) in modern wireless communications, leading to low average efficiency and reduced linearity.
Innovation Solution
A dynamic biasing scheme for Doherty power amplifiers is introduced, where the bias is generated based on the input signal power, allowing the peaking PA to be adaptively biased, enhancing efficiency and linearity over a large dynamic range of output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional RF PA is used to amplify RF signals with high PAPR, then the amplifier can handle the signal, but the average efficiency becomes low
Solution Approach 1:
The power amplifier is divided into two separate amplifiers: a carrier amplifier and a peaking amplifier. The carrier amplifier handles the average power continuously, while the peaking amplifier is activated only during signal peaks. This segmentation allows each amplifier to operate in its optimal efficiency region, resolving the contradiction between handling high PAPR signals and maintaining average efficiency.
Solution Approach 2:
The biasing of the peaking amplifier is made dynamic rather than fixed. The peaking amplifier's bias condition changes based on the instantaneous signal level, allowing it to remain off during low-power periods (improving efficiency) and activate during high-power peaks (handling PAPR). This dynamic adaptation resolves the contradiction between efficiency and signal handling capability.
2Reliability
If conventional RF PA is used with high PAPR signals, then the amplifier operates, but linearity is reduced
Solution Approach 1:
By segmenting the amplification function into carrier and peaking amplifiers, each can be optimized for linearity in its respective operating region. The carrier amplifier maintains linearity for average power, while the peaking amplifier provides linear amplification only when needed for peaks. This segmentation preserves overall linearity while improving efficiency.
Solution Approach 2:
The biasing of the peaking amplifier is controlled by a signal derived from the input signal through a detection and control circuit. This feedback mechanism ensures the peaking amplifier is activated at the precise moment when linearity is needed (during peaks), maintaining overall signal linearity while minimizing power consumption.
3Use of energy by moving object
If the peaking PA is kept off at low power levels, then efficiency improves, but the ability to handle varying power levels dynamically must be enhanced
Solution Approach 1:
The peaking amplifier's bias condition is dynamically adjusted based on the instantaneous signal level. During low-power periods, the peaking amplifier remains off for maximum efficiency. During high-power peaks, it is dynamically activated to provide the needed amplification. This dynamic biasing resolves the contradiction between efficiency and dynamic power handling capability.
Solution Approach 2:
A feedback control circuit monitors the input signal and dynamically adjusts the peaking amplifier's bias accordingly. This feedback mechanism ensures the peaking amplifier is activated at the optimal moment to handle varying power levels while maintaining efficiency during low-power operation.
Data Source
AI summary
A circuit includes a Doherty power amplifier circuit configured to amplify an input signal and generate an amplified signal of the input signal. The Doherty power amplifier circuit includes a first power amplifier circuit configured to operate in class C. The circuit further includes a bias circuit electrically coupled to the first power amplifier circuit. The bias circuit is configured to generate a bias based on the input signal, and to bias the first power amplifier circuit using the generated bias.