Compact TM01 Mode Extractor Using Nested Turnstile Junctions
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Solution Overview
Problem
Current mode extractors for satellite antennas are either bulky or require custom feed chain designs, and they often have limited frequency range compatibility, leading to increased development costs and performance degradation.
Innovation Solution
A compact mode extractor using two back-to-back turnstile junctions with a coaxial coupling device, designed to extract the TM01 mode with minimal impact on fundamental modes, allowing for compatibility with generic user-link feed chains and broadband operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mode extractor is designed to extract higher-order modes (TE21 or TM01) for RFS systems, then beam pointing accuracy is improved, but the feed cluster volume increases significantly
Solution Approach 1:
The mode extractor is integrated within the existing feed chain structure by nesting the turnstile junction and coupling device inside the feed horn assembly. The coaxial coupling device is positioned within the waveguide path, and the turnstile junction is incorporated into the feed horn's internal structure, allowing the mode extraction function to be embedded without increasing the external dimensions of the feed cluster.
Solution Approach 2:
The invention combines the mode extraction function with the existing feed chain components. The turnstile junction serves dual purposes: it acts as both a mode converter and a coupling element for the RFS port. The coaxial coupling device merges the TM01 mode extraction path with the existing waveguide structure, eliminating the need for separate extraction components that would increase volume.
2Volume of moving object
If a mode extractor is designed to be compact, then feed cluster volume is reduced, but compatibility with generic feed chain designs is lost
Solution Approach 1:
The turnstile junction is designed to operate across multiple frequency bands (Ka, Ku, and C-bands) by maintaining consistent performance characteristics for both fundamental and higher-order modes. The symmetric geometric structure of the turnstile junction allows it to function as a universal mode converter that works with standard feed horn configurations, enabling the same extractor design to be applied to different feed chain implementations without customization.
Solution Approach 2:
The invention utilizes asymmetric coupling arrangements within the turnstile junction to achieve broadband operation. By positioning the coaxial coupling device at specific asymmetric locations relative to the turnstile arms, the design achieves optimal coupling for TM01 mode extraction across multiple frequency bands while maintaining compatibility with symmetric feed horn structures.
3Adaptability or versatility
If a mode extractor is designed for broadband operation, then frequency range compatibility is improved, but device complexity increases
Solution Approach 1:
The turnstile junction geometry is optimized with specific dimensional ratios and arm configurations that enable broadband operation. By carefully selecting the arm length, width, and spacing parameters of the turnstile junction, the design achieves consistent performance across Ka, Ku, and C-bands without requiring adjustable or reconfigurable elements. The coaxial coupling device dimensions are similarly optimized to maintain coupling efficiency across the frequency range.
4Ease of operation
If TE21 mode is extracted with a coupling device, then RFS functionality is achieved, but the mode extractor size becomes comparable to a complete feed chain
Solution Approach 1:
The TE21 mode extraction components are nested within the feed horn structure. The coupling device is positioned inside the waveguide path, and the mode extraction function is integrated into the existing feed chain components, eliminating the need for separate extraction assemblies that would increase size to the extent of a complete feed chain.
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 a compact, cost-effective mode extractor that fits within a 32 mm diameter and 23 mm height, maintaining low insertion losses and compatibility with Ka-, Ku-, and C-bands, while ensuring accurate beam pointing and reducing development costs by not requiring custom feed chain designs.
Implementation Method 1
each of the second ports of the first turnstile junction is electromagnetically coupled to a corresponding one of the second ports of the second turnstile junction
Data Source
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AI summary
The present invention relates to a mode extractor for extracting a TM01 mode from an electromagnetic signal, comprising a first turnstile junction (510) and a second turnstile junction (520), each of the turnstile junctions having a first port (511, 521), four second ports of rectangular waveguide (512, 522) which are mutually orthogonal and orthogonal to the first port (511, 521), and a matching section (514, 524) provided at least partially in a center region (513, 523) of the respective turnstile junction, the center region (513, 523) being located at an intersection of the first port (511, 521) and the four second ports (512, 522), wherein the first turnstile junction (510) and the second turnstile junction (520) are arranged so that longitudinal axes of their first ports (511, 521) are aligned with each other and their first ports (511, 521) are facing in opposite directions, each of the second ports (512) of the first turnstile junction (510) is electromagnetically coupled to a corresponding one of the second ports (522) of the second turnstile junction (520), and a coaxial coupling device (540) is inserted into the matching section (514) of the first turnstile junction (510) so that a portion of the coaxial coupling device (540) extends into the first port (511) of the first turnstile junction (510). The mode extractor is compact and can be inserted between a conventional user-link feed chain and an antenna. The TM01 mode enables refined pointing performance.