Load-Modulated Digital Power Amplifier for OFDM Back-Off
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Solution Overview
Problem
Conventional RF power amplifiers face low average efficiency due to high peak-to-average power ratio (PAPR) in OFDM modulation, leading to reduced efficiency as output power decreases, necessitating significant 'back-off' to avoid distortion, which limits their operational efficiency in contemporary and future communication standards.
Innovation Solution
A digital power amplifier configuration using two or more individually activatable amplifiers connected to load modulate each other through a transmission line network, allowing them to operate in saturation and achieve multiple output power levels, with a digital pre-distorter to mitigate signal distortion and optimize efficiency across a wide range of input powers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional RF power amplifiers operate at peak output power to maintain high efficiency, then efficiency is improved, but output power must be reduced to accommodate signal peaks without distortion
Solution Approach 1:
The amplifier is divided into multiple individually activatable amplifiers that can be independently controlled. This segmentation allows the system to activate only the necessary number of amplifiers based on the instantaneous signal power level, avoiding the need to back off all amplifiers and maintaining high overall efficiency while accommodating signal peaks.
Solution Approach 2:
The system dynamically adjusts the operating state of individual amplifiers based on real-time signal conditions. By continuously monitoring the input signal power and activating/deactivating amplifiers accordingly, the system adapts to varying power demands, maintaining high efficiency across a wide range of operating conditions rather than operating statically at a fixed back-off level.
2Reliability
If signal peaks are accommodated by reducing input power to amplifiers, then distortion is avoided, but average efficiency deteriorates
Solution Approach 1:
By segmenting the amplifier into multiple independently controllable units, the system can activate only the necessary number of amplifiers based on instantaneous signal power. This prevents any single amplifier from being overdriven into distortion while ensuring that the total output power matches the signal demand, maintaining signal quality without unnecessary back-off.
Solution Approach 2:
The system changes the operating parameters (activation state) of individual amplifiers dynamically based on the instantaneous signal power level. When signal power is low, fewer amplifiers are activated; when signal power increases, more amplifiers are activated. This parameter adjustment ensures that each active amplifier operates in its optimal efficiency region without distortion.
3Power
If multiple amplifiers are used to accommodate signal peaks, then output power capability is improved, but device complexity increases
Solution Approach 1:
Multiple amplifiers are merged into a single functional unit with a common output combining network. The amplifiers share common control logic and output combining circuitry, which reduces the overall system complexity compared to having fully independent amplifier systems. The merging allows power scaling while maintaining manageable complexity through shared components.
4Loss of energy
If amplifiers operate in saturation region, then efficiency is improved, but output power must be reduced to avoid distortion
Solution Approach 1:
The amplifier system is segmented into multiple individually activatable amplifiers, each capable of operating in saturation for high efficiency. By activating only the necessary number of amplifiers based on instantaneous power demand, each active amplifier can operate in its high-efficiency saturation region without requiring back-off, while the total system output power scales with the number of active amplifiers.
Solution Approach 2:
The system maintains continuous useful action by ensuring that each activated amplifier operates continuously in its high-efficiency saturation region. Rather than having amplifiers operate inefficiently at reduced power levels, the system keeps active amplifiers in saturation and adjusts the number of active amplifiers to match the power demand, maintaining continuous high efficiency across varying power levels.
Data Source
AI summary
A digital power amplifier comprising two or more individually activatable amplifiers. The outputs of the amplifiers are connected causing an activated amplifier of the two or more amplifiers to load modulate another activated amplifier of the two or more amplifiers.