Antenna Pointing Control Using Almanac Scan and Triangulation
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Solution Overview
Problem
In space telecommunications, particularly in cis-lunar orbits, the large communication distances and onboard equipment constraints make it challenging to accurately orient directional antennas for efficient signal reception, as existing systems require additional RF sources and are costly and difficult to implement onboard.
Innovation Solution
A method for controlling antenna pointing using three modes: initial pointing with almanac data, a scan to maximize received power, and a triangulation maneuver to refine the pointing, which does not require additional antenna systems and can compensate for relative movements between the platform and communications device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop systems with several RF sources are used to optimize antenna pointing, then pointing precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The invention extracts and eliminates the unnecessary RF sources from the pointing system. Instead of using multiple RF sources as in conventional closed-loop systems, the patent uses a single RF source combined with a monopulse antenna configuration that provides differential signal paths. This extraction of redundant components directly reduces device complexity while maintaining pointing precision through the monopulse detection method.
Solution Approach 2:
The single RF source in the invention serves multiple functions: it provides both the nominal communication signal and the pointing detection signal simultaneously. The monopulse antenna system enables the same transmitted signal to be used for both communication and for detecting pointing errors through differential phase or amplitude comparison, eliminating the need for separate RF sources for each function.
2Speed
If phase-controlled array antennas are used for fast detection of nominal pointing path, then detection speed is improved, but antenna gain is reduced
Solution Approach 1:
The invention uses almanac data to pre-calculate and establish the nominal pointing direction before actual communication begins. This preliminary action provides an initial pointing reference that eliminates the need for fast scanning operations, allowing the system to start communication immediately with high gain while using only slow triangulation maneuvers for corrections.
Solution Approach 2:
The monopulse antenna system provides different functional zones within the same antenna structure. The main lobe provides high gain for communication, while the secondary lobes provide the differential signals needed for pointing detection. This local differentiation of function within the antenna structure allows simultaneous high gain and pointing capability without requiring a phase-controlled array.
3Device complexity
If almanac-based open-loop pointing is used, then system simplicity is maintained, but pointing precision is insufficient for very high data rates
Solution Approach 1:
The invention introduces a feedback mechanism using the monopulse detection method. The system continuously monitors the differential phase or amplitude signals from the antenna lobes to detect pointing errors relative to the nominal direction indicated by almanac data. This feedback enables automatic correction of pointing deviations, achieving high precision while maintaining relative system simplicity through software-based control.
Solution Approach 2:
The invention uses the differential signals from the monopulse antenna configuration as an intermediary to translate pointing errors into measurable electrical signals. These intermediate signals serve as a bridge between the physical antenna orientation and the control system, enabling precise measurement and correction without requiring complex additional hardware.
4Volume of moving object
If sensors and equipment are located at several metres from the communications system, then mass and volume constraints are relaxed, but coherence of data frames deteriorates due to vibrations and thermo-elastic deformations
Solution Approach 1:
The invention merges the antenna system and the pointing detection system into a single integrated structure. The monopulse antenna configuration uses the same physical antenna elements for both communication and pointing detection, eliminating the need for separate sensor systems located at distant positions. This integration ensures that all components experience the same vibrations and thermal deformations, maintaining coherence.
Solution Approach 2:
The antenna system performs its own pointing detection function through the monopulse method, using its transmitted signal and received differential responses to determine its own orientation. This self-service capability eliminates the need for external sensor systems that would be vulnerable to coherence problems from spatial separation, vibrations, and thermal gradients.
Data Source
AI summary
A method for controlling the pointing of an antenna situated on a platform in the direction of a communications device emitting a reference signal, includes the following steps: S1) apply a first mode of pointing of the antenna using almanac data for the platform and for the communications device so as to obtain an initial position of pointing in azimuth and in elevation of the boresight of the antenna; S2) apply a second mode of pointing of the antenna, comprising at least one scan of the antenna around the initial position so as to point the antenna in a direction that maximizes a received power of the reference signal; S3) apply a third mode of pointing of the antenna wherein at least one triangulation manoeuvre is implemented for pointing the antenna based on the maximum power.