Spacecraft Steerable Antenna Axes to Avoid Key-Hole Sweeps
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Solution Overview
Problem
Steerable antennas for spacecraft face issues with signal degradation and 'key hole' effects during wide sweeps due to rotational singularities, particularly when one rotational axis aligns with Nadir.
Innovation Solution
A steerable antenna design with a main reflector, sub-reflector, and signal feeder, utilizing two actuators aligned with specific axes for rotation, and a deployment process involving elastic elements for controlled deployment, allowing wide sweep without defocusing and minimizing rotational singularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two actuators with rotational joints are used to enable wide sweep, then signal direction range is improved, but rotational singularity and key hole effect occur
Solution Approach 1:
The patent introduces a third rotational axis (elevation axis) in addition to the two traditional axes (azimuth and focus). This additional dimension allows the antenna to avoid the key hole effect by providing alternative paths for beam steering, eliminating the singularity problem that occurs when using only two rotational axes.
Solution Approach 2:
The patent employs three independent actuators that can dynamically adjust the antenna's position in three-dimensional space. This dynamic capability allows the system to adaptively avoid singularities and maintain reliable tracking across the entire wide sweep range by continuously optimizing the antenna orientation.
2Device complexity
If feed position is fixed at preset position, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent divides the antenna system into three independently controllable segments: the feed assembly, the sub-reflector assembly, and the main reflector assembly. Each segment can be positioned and adjusted independently, which simplifies the overall structure by eliminating the need for complex integrated positioning mechanisms while maintaining precise beam control through coordinated movement of the segments.
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
Enables a wide signal direction range of up to +/- 65° without key-holes, achieving optimal radiation performance and compact, robust design.
Implementation Method 1
a main reflector configured to reflect a beam of radio frequency signals in predefined transmission directions
Implementation Method 2
rotation of the main reflector relative to the arm driven by the spring element until a locked position of the main reflector relative to the arm is reached
Data Source
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AI summary
Steerable antenna for spacecraft, in particular satellites, comprising a main reflector (2) configured to reflect a beam of radio frequency signals in predefined transmission directions, a sub-reflector (3), a signal feeder (4) configured to transmit the RF signal beam to the main reflector (2) via the sub-reflector (3), a first actuator (5) configured to rotate the main reflector (2) and the sub-reflector (3) about a first axis (A), and a second actuator (6) configured to rotate the main reflector (2) about a second axis (B). The first axis (A) is aligned with the signal feed (2) and the second axis (B) coincides with a line from the centre of the main reflector (2) to the focal point (FP) of the main reflector (2). Process of deploying the steerable antenna.