Tri-Band Feed Assembly With Common Phase Center and Equal Beamwidths
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Solution Overview
Problem
Conventional SATCOM terminals with small or low profile reflector antennas are limited by the size of their feed assemblies, which restrict their application and often support only single- or dual-band operations, while maintaining similar beamwidths and a common phase center across multiple frequency bands is a design challenge for multi-band feed assemblies.
Innovation Solution
A compact tri-band feed assembly is developed, incorporating a feed horn, coaxial polarizer, orthomode transducer, polyrod, and diplexer to support low, mid, and high frequency bands, with components optimized for smaller dimensions and equal beamwidths across bands, ensuring a common phase center for high antenna efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional feed assembly is used in small or low profile reflector antennas, then the antenna system can be compact, but the feed assembly size limits the types of SATCOM applications and often supports only single- or dual-band operation
Solution Approach 1:
The feed assembly is segmented into distinct functional components: a feed horn for common low/mid/high bands, a coaxial polarizer for low band signals, an orthomode transducer for signal separation, a polyrod for mid/high band support, and a diplexer for band separation. This segmentation allows each component to be optimized for specific frequency ranges while collectively achieving tri-band operation.
Solution Approach 2:
The feed horn is designed to be common to all three frequency bands (low, mid, and high), serving as a universal element that handles signals across the entire operating range. This multi-functional approach reduces overall complexity by having one component perform multiple functions rather than requiring separate horns for each band.
2Length of moving object
If the feed assembly is made compact for small or low profile reflector antennas, then space constraints are satisfied, but maintaining similar beamwidths and common phase center across multiple bands becomes challenging
Solution Approach 1:
Different portions of the feed assembly have specialized structures optimized for specific frequency ranges. The coaxial polarizer with notched rectangular shape is optimized for low band, the polyrod for mid and high bands, while the feed horn provides common coverage. This local optimization allows compact dimensions while maintaining proper beam characteristics for each band.
Solution Approach 2:
The design adjusts physical parameters such as the length of the coaxial polarizer (approximately one-half wavelength at low band frequency), the positioning of ports in the OMT, and the dimensions of the polyrod to achieve equal beamwidths across all three bands while maintaining a common phase center. These parameter adjustments enable compact size without sacrificing beam consistency.
3Volume of moving object
If components are reduced to smaller dimensions for compact operation, then space is saved, but achieving equal beamwidths and common phase center across bands becomes more difficult
Solution Approach 1:
The feed assembly employs a nested structure where the polyrod is disposed within the center conductor of the coaxial cable, the coaxial polarizer is nested within the feed horn structure, and the OMT is integrated into the compact assembly. This nesting allows multiple components to occupy reduced space while maintaining their functional integrity and precise dimensional relationships.
Solution Approach 2:
The design utilizes three-dimensional spatial arrangement to achieve compact volume while maintaining proper beam characteristics. The notched rectangular shape of the coaxial polarizer and the orthogonal arrangement of ports in the OMT exploit dimensional optimization to achieve equal beamwidths across bands in a compact footprint.
Data Source
Figure 1
Figure 1A~1B
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AI summary
A feed assembly for that operates at different frequency bands (e.g., low, mid and high frequency bands) is provided herein. The feed assembly includes a feed horn common to low, mid and high frequency bands, a coaxial polarizer to launch signals in the low band frequency band, a coaxial orthomode transducer (OMT) to launch signals in the low band frequency band and supports the mid and high frequency bands, and a polyrod disposed in a center conductor of the feed assembly, the polyrod common to the mid and high frequency bands. The feed assembly includes a tri-band feed assembly having different portions to support signals in the low frequency band and signals in the mid and high frequency bands.