RF Beam-Shaping Element for Reflector Antenna Blockage Reduction
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Solution Overview
Problem
Reflector-based antennas face performance reductions due to blockages caused by feed elements and sensors, leading to decreased antenna gain and increased side lobe levels, particularly in applications requiring highly directive beams for target tracking and satellite communication.
Innovation Solution
Incorporating a RF beam-shaping element between the primary reflector and the antenna feed to direct RF energy away from blockages towards unblocked regions, allowing for a simplified feed design with fewer elements and improved performance by reshaping the illumination pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If feed elements and sensors are placed at the focal point of the primary reflector, then the antenna can collect and re-radiate electromagnetic energy in a directive fashion, but blockages are created that reduce antenna gain and increase side lobe levels
Solution Approach 1:
The feed is segmented into multiple individual elements (e.g., four elements per quadrant) arranged in a specific geometric pattern. This segmentation allows the feed to illuminate only the unblocked portions of the primary reflector, avoiding the harmful effects of central blockage while maintaining directive radiation patterns.
Solution Approach 2:
The feed elements are positioned and excited with specific amplitude and phase characteristics to create a non-uniform illumination pattern that is zero in the blocked central region and optimized for the unblocked outer regions. This local quality adjustment ensures that energy is directed only towards effective reflecting surfaces.
2Productivity
If multiple feed elements are configured to illuminate only unblocked regions of the primary reflector, then efficiency is increased by directing RF energy away from blockages, but the feed design complexity increases
Solution Approach 1:
The array of feed elements serves multiple functions simultaneously: it provides directive radiation, achieves monopulse tracking capability through sum and difference patterns, and optimizes illumination of unblocked regions. This multi-functionality is achieved within a relatively simple geometric arrangement that can be implemented using standard antenna elements.
Solution Approach 2:
The feed elements are positioned asymmetrically with respect to the blocked region, with specific spacing and excitation amplitudes that create directional illumination patterns. The asymmetric arrangement allows the feed to naturally nullify illumination in blocked regions while maintaining optimal illumination of unblocked areas, achieving high efficiency without complex adaptive mechanisms.
3Device complexity
If a simplified feed design with fewer elements is used, then device complexity is reduced, but the ability to direct RF energy away from blockages is compromised
Solution Approach 1:
The feed elements are pre-positioned and pre-excited with specific amplitude and phase values that automatically create the desired illumination pattern before the antenna operates. This preliminary configuration ensures that blocked regions are never illuminated, eliminating the need for real-time adjustment mechanisms while maintaining simple feed design.
Solution Approach 2:
The illumination pattern created by the simplified feed array is designed to copy or replicate the ideal non-uniform distribution that would be achieved by a more complex feed system. By carefully selecting element positions and excitations, the simplified design reproduces the desired radiation characteristics without requiring additional elements or complex control mechanisms.
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 RF beam-shaping element enhances antenna gain, reduces cross-polarization, and maintains performance comparable to or better than specially configured multi-element feeds, while minimizing the impact on secondary sensors and avoiding additional physical components.
Implementation Method 1
A RF beam-shaping element is located between the primary reflector and the antenna feed. The RF beam-shaping element is configured to direct RF energy from the feed away from a blockage created by the feed itself towards unblocked regions of the primary reflector outside the blockage.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3D
AI summary
A beam-shaping element is provided to shape RF feed energy for reflector-based antennas. The RF beam-shaping element is located between the primary reflector and the antenna feed and configured to direct RF energy from the feed away from a blockage created by the feed itself towards unblocked regions of the primary reflector. The beam-shaping element allows for a simplified feed design. The feed may comprise one or more feed elements, each comprising a radiating element and a feed to the radiating element such as a cavity-backed slot radiator and stripline trace. In a monopulse tracking system, each quadrant may include only a single feed element. In common aperture systems, the RF beam-shaping element may be formed on only the rear surface of the secondary reflector that allows transmission at the predefined RF wavelength while reflecting energy of a second predetermined wavelength to another sensor.