Satellite Antenna Reflector Positioning for Flexible Pointing
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Solution Overview
Problem
Satellite antennas face challenges in flexibility regarding pointing, polarization, and frequency, leading to performance degradation and increased ohmic losses due to defocusing, especially when switching between coverage areas or changing polarization, which complicates implementation and increases production costs.
Innovation Solution
An antenna design featuring a reflector with multiple independent radiofrequency sources and a mechanism for moving and orienting the reflector to position the focal point at the phase center of each source, allowing for flexible pointing, polarization, and frequency adjustments without compromising directivity, achieved through translation and rotation of the reflector mounted on a deployment arm with stepper motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple sources are placed side by side at the focus of the reflector to cover different coverage areas, then the antenna can provide flexibility in pointing directions, but the directivity performance degrades by more than 1 dB due to defocusing
Solution Approach 1:
The reflector is made movable relative to the sources through a positioning mechanism, allowing the focal point to be dynamically adjusted to coincide with the phase center of the active source. This dynamic positioning eliminates defocusing losses while maintaining the ability to serve multiple coverage areas, thus preserving directivity performance (EIRP) while providing pointing flexibility.
Solution Approach 2:
A positioning mechanism acts as an intermediary between the multiple sources and the reflector, enabling precise control of the reflector's position to align the focal point with the phase center of the active source. This intermediary component resolves the contradiction by facilitating optimal alignment without requiring mechanical movement of the sources themselves.
2Adaptability or versatility
If small antennas with mechanical pointing are used to modify and direct the pointing of a spot on the Earth, then pointing flexibility is achieved, but the implementation becomes complex requiring flexible waveguides and mechanical driving of all antenna elements
Solution Approach 1:
The antenna system is segmented into fixed source elements and a movable reflector component. Instead of mechanically moving all antenna elements and waveguides, only the reflector is made movable through a simplified positioning mechanism. This segmentation drastically reduces mechanical complexity while maintaining pointing flexibility.
Solution Approach 2:
The complex mechanical pointing system that would require driving all antenna elements and flexible waveguides is replaced by a simpler system where the sources remain fixed and only the reflector is positioned mechanically. This substitution eliminates the need for flexible waveguides and complex mechanical drives for each element.
3Adaptability or versatility
If two sources with different polarizations are placed in front of an oversized reflector to achieve polarization flexibility, then polarization changing capability is provided, but ohmic losses increase due to defocusing of the sources
Solution Approach 1:
The reflector position is dynamically adjusted to align its focal point with the phase center of the active source, eliminating defocusing losses. This dynamic positioning allows the system to maintain optimal focus for each source regardless of polarization type, thereby reducing ohmic losses while preserving polarization flexibility.
4Adaptability or versatility
If a single source is connected to a complex electrical architecture combining two radiofrequency chains for circular and linear polarization, then polarization flexibility is achieved, but reliability decreases and production cost increases
Solution Approach 1:
The antenna system is segmented into multiple independent sources, each dedicated to a specific polarization type (one source for circular polarization, another for linear polarization). This segmentation eliminates the need for complex electrical architectures that combine multiple RF chains, thereby improving reliability by removing potential failure points while maintaining polarization flexibility.
Solution Approach 2:
Each source is designed to be universal in its capability to illuminate the same coverage area but with different polarization characteristics. This multi-functionality at the source level eliminates the need for complex polarization switching electronics, simplifying the overall architecture and improving reliability.
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 solution enables optimal flexibility in satellite antenna operations, reducing ohmic losses and simplifying implementation by allowing seamless transitions between different coverage areas and polarization modes without performance degradation, thereby enhancing the satellite's mission adaptability and reducing production costs.
Implementation Method 1
The antennas placed on board satellites typically include reflectors, geometrically shaped, illuminated by a single source to cover wide coverage areas pointed at the Earth
Implementation Method 2
the mechanism for moving and orienting the reflector to position the focal point at the phase center of each source
Data Source
AI summary
The antenna has sources (S1-Sn) i.e. horn type sources, arranged in a front part of a reflector (10) having a focal point. The sources have a phase center, and are independent, fixed and connected to separate radio frequency feed systems (RF1-RFn) defining different and predefined polarization and/or operating frequency characteristics. An orientation part displaces and orients the reflector from a position in which the focal point is placed at the phase center of one of the sources to another position in which the focal point is placed at the phase center of the other sources. An independent claim is also included for a method for controlling change of mission of a mission-flexibility antenna.