Antenna Feed Assembly Thermal Expansion Compensation
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Solution Overview
Problem
Antenna beam pointing errors caused by temperature fluctuations in satellite communications systems, particularly due to thermal expansion and contraction of feed assembly materials like aluminum alloys, result in significant beam movement and coverage issues, especially for geostationary satellites passing through the sun's radiation.
Innovation Solution
The antenna feed assembly employs axially spaced mountings with different coefficients of thermal expansion, where a titanium panel with a lower coefficient is used as the first mounting and an aluminum panel with a higher coefficient as the second mounting, to minimize lateral movement of feed chains and maintain beam stability, with the geometry optimized to ensure zero or near-zero lateral distortion of critical transmit/receive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If aluminum alloy is used for mounting feed chains to reduce weight, then weight is reduced, but thermal expansion causes lateral movement of feed horns leading to beam pointing errors
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) by using Invar alloy instead of aluminum alloy for the feed chain mounting structure. This material substitution reduces thermal expansion effects while maintaining the lightweight design, thereby resolving the contradiction between weight reduction and beam pointing accuracy under temperature variations.
Solution Approach 2:
The patent employs composite material construction where Invar alloy components are integrated with aluminum alloy structures. The Invar alloy provides dimensional stability with low thermal expansion, while aluminum alloy maintains lightweight properties. This composite approach allows the feed assembly to achieve both weight reduction and reliable beam pointing accuracy simultaneously.
2Reliability
If low-distortion materials like Invar are used for mounting feed chains, then beam pointing accuracy is improved, but weight increases due to high specific gravity
Solution Approach 1:
The patent applies local quality by using Invar alloy specifically for critical mounting components where dimensional stability is most important, rather than making the entire feed assembly from Invar. This localized application of low-expansion material provides necessary beam pointing accuracy while minimizing overall weight increase compared to using Invar throughout the entire structure.
3Adaptability or versatility
If feed horns are arranged in closely clustered array to provide uninterrupted coverage, then coverage continuity is improved, but sensitivity to thermal expansion increases causing unacceptable lateral movement
Solution Approach 1:
The patent changes the thermal expansion parameter by using Invar alloy mounting structures that exhibit minimal expansion under temperature variations. This allows closely clustered feed horn arrangements to maintain their precise relative positions even during thermal cycles, thereby preserving both coverage continuity and positional precision simultaneously.
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
This configuration reduces translational movement of feed chains and maintains beam stability, minimizing beam pointing errors and ensuring consistent coverage, even under large temperature changes, thereby addressing the sensitivity to thermal expansion and contraction issues.
Implementation Method 1
the first mounting having a lower coefficient of thermal expansion in the lateral direction than the second mounting whereby to reduce translational movement of each transmit/receive element in the lateral direction caused by temperature change of the assembly
Data Source
AI summary
An antenna feed assembly is provided which includes at least two elongate feed chains lying adjacent one another. Each feed chain is adapted to transmit or receive electromagnetic radiation between itself and the antenna along a longitudinal feed axis thereof via a transmit/receive element. The feed chains are held in fixed lateral relationship to one another by first and second mountings spaced apart axially of the feed chains. The transmit/receive elements extend axially from the first mounting towards the antenna and the second mounting is positioned on a side of the first mounting remote from the antenna. The first mounting has a lower coefficient of thermal expansion in the lateral direction than the second mounting whereby translational movement of each transmit/receive element in the lateral direction owing to temperature change of the assembly will be reduced.