Multi-Stage Pseudo-Doherty Balanced Amplifier for Wideband Efficiency
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Solution Overview
Problem
Existing radio systems face challenges in achieving high efficiency and output power in power amplifiers due to sub-optimal drive signals, which can lead to inefficiencies and undesirable spectral emissions, especially in multi-stage pseudo-Doherty load modulated balanced amplifiers (PD-LMBAs).
Innovation Solution
A multi-stage pseudo-Doherty load modulated balanced amplifier (PD-LMBA) architecture with separate drive signals for each component amplifier, utilizing current sensors and a digital splitter to optimize drive signals for efficient wideband operation, and a method to estimate efficiency dynamically, allowing for adaptive tuning and optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If separate drive signals are provided to each component amplifier in a multi-stage PD-LMBA, then efficiency and output power are improved, but device complexity increases due to multiple drive signal paths and control circuitry
Solution Approach 1:
The drive signal control is segmented into multiple independent paths, with each component amplifier (main PA and auxiliary PAs) receiving separately optimized drive signals. This allows independent optimization of each amplifier's operating point and efficiency characteristics, directly resolving the contradiction by enabling efficiency improvement through separate control while managing complexity through modular signal distribution
Solution Approach 2:
The drive signals are dynamically adjusted based on operating conditions, with the controller modifying amplitude and phase of individual drive signals to maintain optimal efficiency across varying power levels. This dynamic control enables the system to adapt to different operating points, improving overall efficiency while the digital implementation manages complexity through programmable control logic
2Loss of energy
If multi-stage pseudo-Doherty architecture is used to extend high efficiency range, then efficiency is improved, but device complexity increases due to additional amplifier stages and coupling circuitry
Solution Approach 1:
The multi-stage PD-LMBA architecture implements a nested structure where auxiliary power amplifiers are integrated within the overall amplifier system, with each stage contributing to the efficiency profile at different power back-off levels. The auxiliary PAs are nested into the main PA system through coupling circuits, creating a compact multi-stage architecture that extends the high-efficiency operating range without proportionally increasing external complexity
Solution Approach 2:
The auxiliary power amplifiers serve multiple functions: they provide load modulation to the main PA, contribute to the output signal, and enable efficiency improvement across multiple operating points. This multi-functionality allows the additional stages to deliver enhanced efficiency range while justifying their inclusion through multiple beneficial effects rather than single-purpose additions
3Loss of energy
If Class C biasing is applied to balanced amplifiers, then efficiency is improved, but linearity deteriorates leading to undesirable spectral emissions
Solution Approach 1:
The patent converts the non-linear behavior of Class C biased amplifiers into a beneficial load modulation mechanism. The auxiliary PAs, also biased in Class C, generate complementary non-linear signals that, when combined through the coupling circuits, create an effective load modulation effect that improves efficiency while the digital predistortion compensates for spectral emissions, transforming the harmful non-linearity into a useful efficiency-enhancing mechanism
Solution Approach 2:
Digital predistortion is applied to the drive signals based on measured or modeled amplifier characteristics, creating a feedback mechanism that pre-compensates for the non-linear behavior of Class C biased amplifiers. This feedback approach maintains the efficiency benefits of Class C operation while correcting the spectral emissions, as the predistorted signals counteract the non-linear distortion before it occurs
4Loss of energy
If digital splitter with non-linear frequency selective functions is used to provide separate drive signals, then efficiency is improved through optimized drive distribution, but device complexity increases due to digital signal processing requirements
Solution Approach 1:
The patent replaces traditional analog RF signal distribution mechanisms with digital signal processing implementation. The digital splitter uses digital filters and signal processing algorithms to provide separate drive signals to each amplifier stage, substituting mechanical/analog components with programmable digital logic. This enables precise control of drive signal characteristics while managing complexity through software-defined functionality rather than complex hardware circuits
Data Source
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AI summary
Aspects of this disclosure relate to a multi-stage pseudo-Doherty load modulated balanced amplifier (10) that includes a control stage (12) and balanced stages (14, 16). The balanced stages (14, 16, 23, 25) can each include a balanced amplifier (14, 16) biased in class C. The balanced stages (14, 16, 23, 25) can each include an output coupler (23, 25) having a port driven by another stage of the multi-stage pseudo-Doherty load modulated balanced amplifier (10). In certain embodiments, two or more stages of the multi-stage pseudo-Doherty load modulated balanced amplifier (10) are driven by separate drive signals.