Asymmetric Waveguide Junction for Compact Orthomode Coupling
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Solution Overview
Problem
There is a need for reducing the footprint of waveguide components in orthomode junctions (OMJs) and orthomode transducers (OMTs) without compromising RF performance, particularly in high throughput satellite systems that require compact designs while maintaining high RF performance.
Innovation Solution
A two-probe waveguide component design with a common waveguide featuring a first portion with conventional dual-polarization operation and a second portion with a partly asymmetric cross-section, providing two-fold rotational symmetry, which reduces the component's size while minimizing undesired cross-polarization and probe-to-probe coupling through appropriate shaping and dimensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a four-probe OMT design is used, then high-order modes rejection is provided, but the footprint diameter is large (about 5⁄6 wavelengths at the highest operating frequency)
Solution Approach 1:
The common waveguide is divided into a first portion with conventional dual-polarization operation and a second portion with asymmetric cross-section. This segmentation allows the symmetric first portion to provide high-order modes rejection while the compact asymmetric second portion reduces the overall footprint.
Solution Approach 2:
The second portion of the common waveguide features an asymmetric cross-section with at most two-fold rotational symmetry, which enables compact design while maintaining proper polarization separation. The asymmetric geometry reduces the footprint compared to fully symmetric four-probe designs.
2Reliability
If the OMT is placed closer to the horn operating in the lower frequency band, then filtering rejection from Tx ports to Rx ports is improved, but the footprint is increased due to included probe filters and combining network
Solution Approach 1:
The waveguide component integrates the common waveguide with asymmetric cross-section that combines polarization separation and frequency filtering functions in a single compact structure, eliminating the need for separate probe filters and combining networks that would increase footprint.
3Area of stationary object
If a two-probe design is used to reduce footprint, then the component size is reduced, but undesired cross-polarization and probe-to-probe coupling increase
Solution Approach 1:
The first portion of the common waveguide maintains conventional symmetric properties for proper polarization coupling, while the second portion introduces asymmetric cross-section properties to reduce cross-polarization and probe-to-probe coupling. This local differentiation of properties enables compact design without sacrificing RF performance.
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 design allows for a compact waveguide component that maintains high RF performance, including enhanced cross-polarization discrimination and reduced probe-to-probe coupling, making it suitable for dual-linear and dual-circular operation without the length penalties associated with other compact designs.
Implementation Method 1
The coupling probes may be arranged to couple to different polarization components of an electromagnetic field present in the common waveguide. The coupling probes may couple to the different polarization components of the electromagnetic field through longitudinal coupling slots.
Implementation Method 2
The second portion of the common waveguide may have a cross-section with at most two-fold rotational symmetry. By appropriate shaping and dimensioning of the asymmetric portion, undesired cross-polarization and/or probe-to-probe coupling can be reduced or even suppressed.
Data Source
AI summary
A waveguide component for an orthomode junction or an orthomode transducer includes a common waveguide with a longitudinal direction, the common waveguide includes at least a first portion and a second portion with different cross-sections, and two coupling probes, each arranged orthogonally to the longitudinal direction. The coupling probes are further arranged to couple to different polarization components of an electromagnetic field present in the common waveguide. The second portion of the common waveguide has a cross-section with at most two-fold rotational symmetry.