Satellite Path-Length Difference Estimation via Calibration Signal
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Solution Overview
Problem
Current spacecraft orbit recovery systems for geostationary satellites are complex and costly due to the need for highly directional and stable receiving antennas, which are sensitive to phase instabilities and require accurate signal-to-noise ratio measurements, leading to high manufacturing costs and civil engineering challenges.
Innovation Solution
A method and system that measure a 'useful phase difference' between signals received by two antennas using correlation or FFT/PLL analysis, with a calibration signal to compensate for phase instabilities, allowing for less stringent antenna stability requirements and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If highly directional and stable receiving antennas are used to improve signal-to-noise ratio and phase stability, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces a calibration signal as an intermediary element to measure and compensate for phase instabilities in the receiving chains. By transmitting a calibration signal from a known position and measuring its phase difference between antennas, the system can calculate correction terms that compensate for phase variations without requiring highly stable antennas. This intermediary calibration process resolves the contradiction by enabling accurate measurements with simpler, less expensive antenna hardware.
Solution Approach 2:
The system implements feedback by continuously measuring phase differences of the calibration signal and using these measurements to compute correction terms that are applied to subsequent target signal measurements. This feedback mechanism allows the system to compensate for phase instabilities in real-time, maintaining measurement precision while using less expensive, less stable antennas.
2Measurement precision
If highly stable receiving chains are used to reduce phase instability variations, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The calibration signal acts as an intermediary that quantifies the phase instabilities introduced by the receiving chains. By measuring the phase difference of the calibration signal (which passes through the same receiving chains), the system obtains correction terms that compensate for the chains' instabilities. This eliminates the need to manufacture extremely stable receiving chains while maintaining measurement accuracy.
Solution Approach 2:
The receiving chains essentially measure and compensate for their own instabilities using the calibration signal. The phase differences measured from the calibration signal directly reflect the instabilities in the receiving chains, allowing the system to self-correct without requiring external stabilization mechanisms or extremely stable hardware.
3Measurement precision
If distance between receiving antennas is increased to improve path-length difference estimation accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The calibration signal provides feedback about the actual phase differences introduced by the geometry of the receiving antenna arrangement. By measuring the calibration signal's phase difference and comparing it with the expected geometric phase difference, the system can determine correction terms. This feedback mechanism allows accurate path-length difference estimation even with smaller antenna separations, as the calibration compensates for geometric effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate path-length difference estimation with reduced complexity and cost, enabling efficient orbit recovery of geostationary satellites while minimizing interference and phase instability effects.
Implementation Method 1
measuring a phase difference, referred to as 'useful phase difference', between signals corresponding to the target signal received respectively on the first receiving antenna and the second receiving antenna
Implementation Method 2
The useful phase difference measurement step comprises either the correlation of the signals received respectively on the first receiving antenna and the second receiving antenna with a reference target signal
Implementation Method 3
or the analysis of said signals received respectively on the first receiving antenna and the second receiving antenna by means of an FFT or of a PLL
Implementation Method 4
or the analysis of said signals received respectively on the first receiving antenna and the second receiving antenna by means of an FFT or of a PLL
Data Source
AI summary
A method and system for estimating a path-length difference between two paths followed by a target signal transmitted by a spacecraft or aircraft to a first receiving antenna and a second receiving antenna of a receiving base, respectively. A useful-phase difference is measured between signals that correspond to the target signal received by the first receiving antenna and second receiving antenna. The path-length difference is estimated in accordance with the useful-phase difference measurements. The measurement of the useful-phase difference comprises either correlating the signals received by the first receiving antenna and second receiving antenna, respectively, with a reference target signal, or analyzing the signals received by the first receiving antenna and second receiving antenna, respectively, using an FFT or a PLL.