Outphasing Power Amplifier Linearization with Phase-Corrected Class-D Bridge
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Solution Overview
Problem
Traditional power amplifiers experience efficiency degradation at reduced power levels, particularly with wideband waveforms like QAM, WCDMA, or OFDM, due to inefficient linearization methods and high-level modulators that struggle with varying signal envelopes, leading to reduced net efficiency and limited modulation bandwidth.
Innovation Solution
A system for linearization of outphased power amplifiers using a frequency counter, phase shifters, amplitude error amplifiers, and Class-D amplifiers to adjust RF inputs and phase corrections, ensuring efficient power back-off by splitting the input signal into constant and variable amplitude signals and shifting phases to optimize output power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional EER or LINC linearization methods are used at full power, then high efficiency is achieved, but efficiency degrades significantly at reduced power levels
Solution Approach 1:
The invention segments the power amplifier into multiple parallel amplifiers operating at different power levels. Each amplifier is optimized for a specific power range, allowing the system to maintain high efficiency across the entire power spectrum by selecting the appropriate amplifier segment for each operating condition.
Solution Approach 2:
The system dynamically switches between different amplifier segments based on the required output power level. This dynamic adaptation allows the amplifier to operate at peak efficiency for each power level rather than suffering efficiency degradation across all power levels.
2Adaptability or versatility
If high-level modulators are used for linearization, then full power efficiency is maintained, but modulation bandwidth is limited due to inability to follow varying signal envelopes
Solution Approach 1:
The invention divides the amplification task across multiple parallel amplifiers, each handling a portion of the signal spectrum. This segmentation allows each amplifier to operate within its optimal bandwidth and power range, collectively achieving both wide modulation bandwidth and high efficiency.
Solution Approach 2:
The system changes operating parameters (power level, bandwidth) by selecting different amplifier segments. Each amplifier is configured with specific parameters optimized for its designated operating range, allowing the overall system to adapt to varying signal conditions without efficiency loss.
3Power
If single amplifier operates at peak power, then maximum output power is achieved, but net efficiency drops at average power levels (6-10 dB below peak)
Solution Approach 1:
The invention segments the total output power requirement across multiple parallel amplifiers operating at different power levels. When full peak power is needed, all amplifiers contribute; when average power is sufficient, only the appropriate lower-power amplifiers are activated, maintaining high net efficiency across all operating conditions.
Data Source
AI summary
A high efficiency outphasing power amplifier is disclosed which provides a high-efficiency, high-linearity outphasing amplifier capable of amplifying complex, wideband, multi-tone signals. Systems herein may amplify at least 256 symbol QAM signals with negligible distortion, while achieving high direct current-to-radio frequency efficiency sustainable at virtually all power levels. Embodiments of the outphasing amplifier employ a bridge output network formed from two complementary Class-D amplifiers to switch a dc supply voltage across the load. In embodiments, the phase of both halves of the bridge is varied from zero to +/â90 or zero to 180 degrees to split the workload, to correct for phase error within the bridge network and to control output power. Because the current through the load and thus through the two halves of the amplifier vary directly with output level, the efficiency remains high even when power output is low.