Reverse Orthomode Junction Assembly with Filters
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Solution Overview
Problem
Current antenna feed systems, particularly those using the turnstile junction topology, face challenges in achieving adequate signal isolation and power handling due to the size and mass of filters, especially at lower frequencies, and struggle to meet stringent return loss requirements for high Tx power signals, which limits their performance in dual circular polarization applications.
Innovation Solution
An advanced reverse orthomode junction feed assembly with associated filters, featuring a 6-port junction in a squared or circular waveguide, an asymmetric high-frequency band-reject filter, wide-band impedance matching resonant cavities, and choking irises, which improves impedance matching and return loss, enabling better signal isolation and power handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard turnstile junction topology is used with filters in Tx waveguides, then frequency band separation is achieved, but the system volume and mass increase significantly
Solution Approach 1:
The patent inverts the conventional turnstile junction topology by placing the low frequency feed section in the axial position and the high frequency feed section in the radial position, opposite to the standard configuration. This reversal enables more compact filter integration and reduces overall system volume while maintaining effective frequency band separation.
Solution Approach 2:
The patent combines multiple functions into integrated components, particularly merging the filter structures directly into the waveguide paths with optimized geometries that perform both frequency selection and impedance matching functions, thereby reducing the number of discrete components and overall system volume.
2Volume of stationary object
If small-sized filters are used in Tx waveguides, then system volume is reduced, but peak and average power handling capabilities are limited
Solution Approach 1:
The patent employs composite filter structures combining multiple materials with different electromagnetic properties, including dielectric materials and conductive coatings, to achieve high power handling capability in compact volumes. The composite construction allows for optimized field distribution and heat dissipation.
Solution Approach 2:
The patent utilizes parameter optimization in filter design, including adjusted cavity dimensions, optimized iris geometries, and tuned resonant frequencies, to maximize power handling capability within reduced physical dimensions. The design parameters are specifically optimized for high peak and average power operation.
3Shape
If conventional OMJ topology is used, then high frequency feed is in axial position, but return loss requirements for high Tx power signals are not met
Solution Approach 1:
The patent inverts the conventional orthomode junction topology by swapping the positions of high and low frequency feed sections. This reversal, combined with optimized transition structures, improves return loss performance by better matching impedance characteristics for high power transmit signals.
Solution Approach 2:
The patent implements localized impedance matching structures at critical junction points within the OMJ, including optimized iris geometries and transition sections with varying dimensions, to improve return loss performance in specific high-stress areas without affecting the overall topology.
4Weight of stationary object
If filters with small sections are used, then system mass is reduced, but both peak and average power handling capabilities are limited
Solution Approach 1:
The patent uses composite material construction in filters, combining lightweight dielectric materials with high-power conductive elements, to achieve reduced mass while maintaining or enhancing power handling capability. The composite structure optimizes both weight and thermal management.
Solution Approach 2:
The patent optimizes filter section parameters including thickness, density, and geometric dimensions to minimize mass while ensuring adequate power handling. The parameters are tuned to achieve the lowest possible mass for the required power handling specifications.
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 solution provides enhanced RF performance by achieving wider bandwidth operation and improved return loss, effectively isolating Tx and Rx frequency bands, and supporting higher power handling capabilities, thus meeting stringent performance requirements in spacecraft environments.
Implementation Method 1
an asymmetric high frequency band reject filter connecting to the first signal port, to reject a second high frequency signal
Implementation Method 2
wide-band impedance matching resonant cavities
Implementation Method 3
choking irises in the common path
Data Source
AI summary
An advanced reverse orthomode junction feed assembly with associated filters for use in an antenna feed system for transmitting a first low frequency (LF) electromagnetic signal and receiving a second high frequency (HF) electromagnetic signal. The assembly includes, in a preferred square waveguide topology, an orthomode junction with an antenna port for connecting to a choking iris matching section and an antenna feed, an opposed generally coaxial first signal port to transmit the LF signal, and a generally perpendicular second signal port, located there between, to receive the HF signal. A first signal channel having fully asymmetric on-axis second signal reject filters connects to the first port; and a second signal channel having cross-axis first signal reject filters with multi-cavity HF path matching assembly connects to the second port. The use of a magic-tee as a combiner for the receive signal provides tracking capability to the antenna feed system.