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15 July 2010 Component development for ALMA Band 1 (31-45 GHz)
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ALMA Band 1, covering 31-45 GHz, is the lowest signal frequency band of the ALMA telescope and development of the technology to be used for the front-end cartridge is currently in a research phase. We have made progress on various key components designed for use in the ALMA Band 1 cartridge, including the orthomode transducer (OMT), low-noise amplifier (LNA), lens, and down-converting mixer. Since the layout of the ALMA cartridges within the antenna is not optimized for the lowest band, a dielectric lens is required to avoid blocking other bands. Using a lens necessitates careful characterization of the dielectric properties controlling focal length and dielectric loss. It is also important to match the index of refraction of the lens to minimize reflection while still providing equal performance for both linear polarizations and not introducing any cross-polarization effects. Different anti-reflection techniques will be shown; for example, a hole array, as an anti-reflection layer, has been used for a vacuum window and measured results are compared with simulation. A test cryostat has been constructed by adding an extension to a commercial liquid helium cryostat. Initial sensitivity measurements of a simplified prototype receiver will be given, incorporating an HDPE window, commercial conical feedhorn, 3-stage LNA, and warm amplification stage. An overview of the system losses, receiver noise budget, and system alignment tolerances will also be shown. Furthermore, there is interest in either extending or shifting the existing frequency towards 50 GHz, and the impact on each component will be considered.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Doug Henke, Stéphane Claude, Frank Jiang, David Dousset, and Fillipo Rossi "Component development for ALMA Band 1 (31-45 GHz)", Proc. SPIE 7741, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V, 774123 (15 July 2010);


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