Nested Multistage Doherty PA for High-PAPR Efficiency and Linearity
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Solution Overview
Problem
Conventional multistage Doherty power amplifiers face challenges with low efficiency and poor linearity, particularly when using amplifiers with limited gain, due to excessive drive power dissipation and amplifier saturation, which affects their performance in high peak to average power ratio (PAPR) scenarios.
Innovation Solution
A nested multistage Doherty power amplifier design is implemented, utilizing a generalized carrier amplifier and peaking amplifier with different semiconductor features and bias voltages, optimized by a power distribution function (PDF) to enhance efficiency and linearity, and incorporating pre-distortion to compensate for gain compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional multistage Doherty PA implementations are used with amplifiers of limited gain, then the amplifier can handle high PAPR signals, but excessive drive power dissipation occurs and efficiency becomes low
Solution Approach 1:
The patent implements a nested multistage Doherty architecture where multiple Doherty stages are cascaded, with each stage handling a specific portion of the power backoff range. The first Doherty stage handles peak power conditions while the second stage handles lower power conditions, allowing each amplifier to operate in its optimal efficiency region and reducing overall drive power dissipation across the full PAPR range.
2Device complexity
If amplifiers are required to saturate at transition points in conventional multistage Doherty PA, then the structure is simpler, but linearity becomes poor
Solution Approach 1:
The patent employs dynamic gain control and adaptive biasing mechanisms that allow amplifiers to transition smoothly between operating states rather than abruptly saturating. The gain compression characteristics are dynamically adjusted based on the input signal level and stage operating point, maintaining linearity during transitions while preserving the multistage architecture's efficiency benefits.
3Power
If the power gain of sub-carrier amplifier is compressed to predetermined level, then gain extension effect is achieved, but the sub-carrier amplifier efficiency decreases
Solution Approach 1:
The patent utilizes controlled gain compression of the sub-carrier amplifier to generate a gain extension effect that linearizes the overall amplifier response. By carefully designing the compression characteristic and operating point, the sub-carrier amplifier's compressed gain compensates for the main amplifier's nonlinearity, achieving overall linearity improvement while managing the efficiency trade-off through optimal parameter selection.
Data Source
AI summary
A multistage Doherty power amplifier and a transmitter are provided, and the multistage Doherty power amplifier includes: a generalized carrier amplifier, which is a nested 2-way inverted Doherty sub amplifier, and a generalized peaking amplifier, connected to the generalized carrier amplifier, which is a nested single ended sub amplifier or a nested 2-way normal Doherty sub amplifier, the generalized carrier amplifier and the generalized peaking amplifier are arranged in a generalized 2-way inverted Doherty power amplifier form. With the multistage Doherty power amplifier, signal power probability distribution function (PDF) oriented for a cost-effective multi stage Doherty PA design is applied, and 2-way normal and inverted Doherty PA cells are used as basic units to construct multistage Doherty PA with gain extension effect.