Multistage Doherty Power Amplifier With Gain Extension for High PAPR
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Solution Overview
Problem
Conventional Doherty power amplifiers face challenges with low efficiency and poor linearity due to the use of amplifiers with limited gain and the need for high drive power dissipation, especially when dealing with high peak-to-average power ratios (PAPR) beyond 6 dB.
Innovation Solution
A multistage Doherty power amplifier design utilizing nested 2-way inverted and normal Doherty sub-amplifiers, with different semiconductor processes for central and side cells, and a signal power probability distribution function (PDF) oriented approach to optimize efficiency and linearity, including analog pre-distortion and step-wise Doherty operation segmentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional multistage Doherty PA implementations are used with amplifiers of limited gain, then the device can be manufactured with available components, but the efficiency becomes low due to excessive drive power dissipation
Solution Approach 1:
The patent segments the amplification function into multiple stages with different gain characteristics. The first power amplifier stage provides high gain for low-power signals, while the second stage provides additional gain for higher-power signals. This segmentation allows each stage to operate in its optimal efficiency range, reducing overall drive power dissipation while using commercially available amplifiers with limited gain.
2Reliability
If conventional multistage Doherty PA implementations are used, then the structure can be implemented with standard amplifiers, but the linearity becomes poor due to saturation requirements at transition points
Solution Approach 1:
The patent implements dynamic gain adjustment across multiple amplifier stages. The first power amplifier stage operates with high gain at lower power levels, and the second stage activates with appropriate gain at higher power levels. This dynamic operation avoids the need for amplifiers to saturate at transition points, maintaining linearity throughout the power range while using standard amplifier components.
3Loss of energy
If a classic Doherty PA is used, then efficiency is enhanced at high PAPR signals, but the Doherty region is limited to maintaining high efficiency only when PAPR is greater than 6 dB
Solution Approach 1:
The patent segments the power amplification into multiple stages, each optimized for different power levels and PAPR conditions. The first stage handles low-power signals with high gain, while the second stage handles higher-power signals. This segmentation extends the effective Doherty region to accommodate a broader range of PAPR values beyond just greater than 6 dB, maintaining high efficiency across varying signal conditions.
Solution Approach 2:
The patent changes the gain parameter across different amplifier stages and operating conditions. The first power amplifier stage operates with high gain for low-power signals, while the second stage provides appropriate gain for higher-power signals. This parameter adjustment allows the system to maintain high efficiency across a broader range of PAPR values, enhancing adaptability to different signal distributions.
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.