APSK Constellation Ratio Correction for LEO Signal Distortion
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Solution Overview
Problem
Low-earth orbit (LEO) satellite communication systems face challenges in compensating for signal distortion due to the rapid motion of satellites and limited signal processing resources, making it difficult for user terminals to correctly demodulate data from signals received from LEO satellites.
Innovation Solution
A method and apparatus for reducing amplitude and phase distortion of satellite signals using amplitude phase shift keying (APSK) modulation, where a user terminal determines the ratio between the inner and outer circle radii of the constellation and generates a correction signal based on this ratio and a reference ratio to compensate for distortion, allowing for effective signal demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-distortion techniques are used to compensate for nonlinear distortion, then signal quality is improved, but device complexity increases and is impractical for LEO satellites with limited processing resources
Solution Approach 1:
The patent inverts the conventional approach by implementing post-distortion compensation at the user terminal instead of pre-distortion at the satellite. The user terminal determines distortion characteristics from received signals and applies correction, reversing where the compensation function is performed to match the bent-pipe satellite architecture with limited processing resources.
Solution Approach 2:
The user terminal performs self-service by autonomously determining its own receiver distortion characteristics and generating appropriate correction signals without requiring complex satellite processing. The terminal uses its received signals to characterize and compensate for its own distortion, eliminating the need for satellite-based pre-distortion resources.
2Area of stationary object
If LEO satellites are used to provide coverage, then coverage area is improved, but signal distortion increases due to rapid satellite motion and limited processing resources
Solution Approach 1:
The patent implements feedback by having the user terminal continuously monitor received signal characteristics, determine distortion parameters from the signal itself, and adjust correction signals accordingly. This closed-loop approach allows the terminal to adapt to changing distortion conditions caused by rapid satellite motion while maintaining accurate demodulation.
Solution Approach 2:
The patent changes the approach from fixed pre-distortion parameters at the satellite to dynamic post-distortion parameters at the terminal. The user terminal determines distortion characteristics in real-time from received signals and adjusts correction parameters accordingly, enabling adaptation to rapid LEO satellite motion without requiring complex satellite processing.
3Device complexity
If conventional demodulation is used without distortion compensation, then device complexity is reduced, but data demodulation accuracy deteriorates due to nonlinear distortion from power amplifiers
Solution Approach 1:
The user terminal performs self-service by autonomously determining its own receiver distortion characteristics from received signals and generating appropriate correction signals without requiring complex satellite processing. The terminal uses its received signals to characterize and compensate for its own distortion, eliminating the need for satellite-based pre-distortion resources.
Solution Approach 2:
The patent introduces an intermediary correction signal that mediates between the distorted received signal and the demodulation process. The correction signal, generated based on determined distortion characteristics, acts as an intermediary element that linearizes the received signal before demodulation, improving accuracy without requiring complex processing architecture.
Data Source
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AI summary
A method and apparatus for reducing distortion of satellite signals modulated using amplitude phase shift keying (APSK) are disclosed. A receiver such as a user terminal receives, from a satellite, a signal including APSK-modulated symbols mapped to a constellation including a plurality of points arranged in an inner circle and in an outer circle; determines, based on the received APSK-modulated symbols, a ratio between a radius of the inner circle of the constellation and a radius of the outer circle of the constellation; generates a correction signal based, at least in part, on a comparison between the determined ratio and a reference ratio; compensates for distortion of the received signal based, at least in part, on the correction signal; mixes the correction signal with the received signal to generate a distortion-compensated signal; and de-modulates the distortion-compensated signal to recover data transmitted from the satellite.