Beamformed RF Amplifier Chains Using Decorrelation for Power Efficiency
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Solution Overview
Problem
Communications satellites are limited by power efficiency, leading to conservative estimates of signal-to-noise ratio and increased costs due to nonlinearities in the RF signal chain, which conventional methods fail to optimize effectively with emerging nonlinear solid-state power amplifiers and digital ASIC technologies.
Innovation Solution
The technique involves signal beamforming and decorrelation prior to conversion to compensate for nonlinearities, enabling the use of highly nonlinear components like digital amplifiers and low-resolution ADCs/DACs, while ensuring sufficient signal quality through intermodulation decorrelation and beamforming with multiple antenna elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear amplifier designs are used to minimize nonlinearities, then signal quality is maintained, but power efficiency is significantly reduced
Solution Approach 1:
The patent embraces the nonlinearities of solid-state power amplifiers rather than trying to eliminate them. By using digital predistortion and adaptive filtering, the system converts the harmful nonlinear distortion into useful signal enhancement, achieving both high power efficiency and acceptable signal quality at the receiver.
Solution Approach 2:
The system dynamically adjusts operating parameters including amplifier backoff levels, predistortion coefficients, and filtering characteristics to optimize the tradeoff between power efficiency and signal quality under varying operational conditions.
2Reliability
If beamforming with multiple antenna elements is implemented, then signal quality and capacity are improved, but system complexity increases
Solution Approach 1:
The patent combines beamforming functionality with nonlinear compensation techniques in a unified digital signal processing architecture. By integrating these functions, the system achieves improved signal quality through beamforming while avoiding the additional complexity that would result from separate implementation of each technique.
Solution Approach 2:
The digital signal processing system performs multiple functions including beamforming, predistortion, and adaptive filtering using a common computational framework, thereby achieving multi-functionality without proportionally increasing system complexity.
3Use of energy by moving object
If digital predistortion is applied to compensate for nonlinearities, then power efficiency improves, but out-of-band distortion aliasing may occur
Solution Approach 1:
The system applies predistortion before the power amplifier to preemptively compensate for nonlinearities. By addressing the distortion issue in advance rather than attempting to filter it afterward, the system maintains power efficiency while preventing out-of-band aliasing from degrading in-band signal quality.
Data Source
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AI summary
A satellite communication system processes a plurality of input signals to generate beamformed signals, drives a plurality of nonlinear power amplifiers with the beamformed input signals to produce RF signals for transmission; and transmits the RF signals with a plurality of Tx antenna elements. Conversion to and from linear signals to and from nonlinear or digitized signals is performed. Temporal or spatial decorrelation of the beamformed signals is employed to reduce the impact of intermodulation products. In some cases the power amplifiers are nonlinear, and can be one-sided or two-sided and produce two or three distinct output levels.