The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel.
A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength.
First, a mechanical prototype was built using an approximately 102- micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higherfrequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly.
This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.
This work was done by Larry W. Epp, Stephen L. Durden, Vahraz Jamnejad, Ezra M. Long, John B. Sosnowski, Raymond J. Higuera, and Jacqueline C. Chen of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48174
This Brief includes a Technical Support Package (TSP).
Dichroic Filter for Separating W-Band and Ka-Band
(reference NPO-48174) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing the development and testing of a Dichroic Filter designed to separate W-Band and Ka-Band frequencies. This research, conducted under NASA's Innovative Technology Program, aims to advance aerospace technologies with potential applications beyond space exploration.
The Dichroic Filter is a critical component for various scientific and engineering applications, particularly in telecommunications and radar systems. The document outlines the design and fabrication of the filter, emphasizing the use of materials such as Aluminum 6061-T6, which was chosen for its cost-effectiveness compared to copper, while acknowledging that the final flight model will be made from oxygen-free electronic (OFE) copper to minimize insertion loss.
Key findings from the testing phase are highlighted, particularly the quasi-optical test bed results, which demonstrated good accuracy in both theoretical predictions and measurements at the desired pass band around 94.5 GHz, with an error margin of less than 0.8%. This level of precision is crucial for ensuring the filter's effectiveness in real-world applications.
The document also describes the construction of test horns and the preparation of the test bed for the dichroic filter, showcasing the collaborative efforts of the research team, which includes notable contributors such as Larry Epp, Stephen L. Durden, and others. The completed prototype features a perforated area with a diameter of 50.8 mm (2 inches) and is designed to facilitate further testing and validation.
In addition to the technical specifications and results, the document emphasizes the importance of compliance with U.S. export regulations and the proprietary nature of the information contained within. It serves as a resource for those interested in the advancements in dichroic filter technology and its implications for future aerospace applications.
Overall, this Technical Support Package not only documents the specific research findings but also reflects NASA's commitment to fostering innovation and collaboration in the field of aerospace technology, paving the way for future developments that could benefit a wide range of industries.
