ISSTT Proceedings

ISSTT Proceedings

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Flight Attenuators for the HIFI Local Oscillator Bands

Authors:
Willem Jellema, Marcel Bruijn, Jan-Joost Lankwarden, Marcel Ridder, Herman Jacobs, Wolfgang Wild, Stafford Withington
Abstract:
During the flight instrument level tests of HIFI it became clear that the instrument performance suffered from LO related instabilities. Because the actual LO power requirements of the flight mixers appeared to be an order of magnitude smaller than specified, the LO subsystem was forced to be operated outside its rated and stable operating regime. In order to push the LO power amplifiers back into normal and saturated operation, broadband optical attenuation in all LO bands of around 3 dB up to 18 dB appeared necessary. In this paper we present the design and development of broadband optical attenuators from first ideas and principles, demonstration, development to spacequalification, flight production, performance characterization and post-delivery to Herschel-HIFI. The asbuilt attenuators are based on thin Ta films on robust alumina substrates and in a few cases combined with an ARcoating based on a polyimide spinning process. We conclude by presenting the attenuator flight performance, which can be tuned within a few tenths of a dB from target, and essentially provide a flat frequency response from 500 GHz up to more than 2 THz at cryogenic conditions.
Categories:
Herschel-HIFI
Year:
2008
Session:
4
Full-text:
Download a PDF of this paper.
Page Number(s):
122-131