PAGE CONTENTS
Objectives
The objectives of the activity are the following:
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To design and manufacture using metal additive manufacturing (SLM) a monolithic cluster of 13 dual-band, dual-circular polarization feed chains in Ka-band for GEO applications.
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To extensively test the resulting Engineering Model (S-parameter measurements, radiating measurements in anechoic chamber, thermal cycling, vibration testing).
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To perform PIM testing on a representative feed chain (using the same architecture as those included in the feed cluster) and to verify the PIM-free performance of the part and of the end-to-end manufacturing technology of SWISSto12 using silver-plating.
Challenges
The main challenges of the activity are the following:
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The pitch of the feed chain needed to meet the mission requirements is extremely small (22 mm). To meet this, a specific feed chain architecture is selected and several tricks are implemented, profiting from the degrees of freedom offered by additive manufacturing.
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The mechanical design of the final feed cluster EM is challenging for modern CAD software. The complexity of the part requires special handling to avoid software and model collapses.
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The machining of the feed cluster EM is also very challenging, the main risk being the protection of the waveguide channels from any shavings produced during the machining process.
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Finally, the way to implement test jigs (waveguide adaptors) suitable for performing S-parameter testing in such a compact array is not straightforward and requires a lot of effort.
System Architecture
The system architecture selected for the feed chain is the following:
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Two diplexers with custom waveguide inputs for TX (17.7-21.2 GHz) and RX (27.5-31 GHz). The two diplexers are flipped so that they can be put close to one another and profit from wall sharing (mass reduction and mechanical rigidity improvement).
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The two diplexers are connected to the two ports of a circular septum polarizer, used to generate right and left handed circular polarizations, respectively.
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After the septum polarizer, a very compact and low-profile choke horn (horn with axial corrugations) is connected.
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Not included in the scope of the activity: a waveguide harness network needs to be implemented to feed the input ports of the diplexers and to match the pitch of the feed cluster with that of the amplifiers (that is typically larger). For testing purposes, waveguide lofts to standard waveguide (adaptors) outputs are implemented as separate parts.
Plan
The project plan includes the following phases:
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Mission selection and requirements definition: the requirements are derived from a real GEO mission scenario, using also inputs from other relevant missions. Challenging requirements are adopted to push the limits of the technology.
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Preliminary design phase: two feed chain architectures are investigated and compared numerically. Several de-risking parts (sub-components of the feed chains) are breadboarded to assess the performances.
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Detailed RF and mechanical design of the feed cluster: The selected architecture is implemented in a cluster including 13 feed chains. Several iterations between RF and mechanical design are performed to guarantee compliance to the specifications.
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Manufacturing and testing: The feed cluster EM is manufactured and extensively tested (RF, mechanical, thermal, and PIM tests) to verify the compliance to the specifications.
Current Status
The project is completed with the successful manufacturing and extensive testing (thermal, mechanical, RF, PIM) of a feed cluster engineering model.
Companies
