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arXiv · 1012.3899

1.2 Meter Shielded Cassegrain Antenna for Close-Packed Radio Interferometer

Patrick M. Koch·Philippe Raffin·Yau-De Huang·Ming-Tang Chen·Chih-Chiang Han·Kai-Yang Lin·Pablo Altamirano·Christophe Granet·Paul T. P. Ho·Chih-Wei L. Huang·Michael Kesteven·Chao-Te Li·Yu-Wei Liao·Guo-Chin Liu·Hiroaki Nishioka·Ching-Long Ong·Peter Oshiro·Keiichi Umetsu·Fu-Cheng Wang·Jiun-Huei Proty Wu
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Abstract

Interferometric millimeter observations of the cosmic microwave background and clusters of galaxies with arcmin resolutions require antenna arrays with short spacings. Having all antennas co-mounted on a single steerable platform sets limits to the overall weight. A 25 kg lightweight novel carbon-fiber design for a 1.2 m diameter Cassegrain antenna is presented. The finite element analysis predicts excellent structural behavior under gravity, wind and thermal load. The primary and secondary mirror surfaces are aluminum coated with a thin TiO$_2$ top layer for protection. A low beam sidelobe level is achieved with a Gaussian feed illumination pattern with edge taper, designed based on feedhorn antenna simulations and verified in a far field beam pattern measurement. A shielding baffle reduces inter-antenna coupling to below $\sim$ -135 dB. The overall antenna efficiency, including a series of efficiency factors, is estimated to be around 60%, with major losses coming from the feed spillover and secondary blocking. With this new antenna, a detection rate of about 50 clusters per year is anticipated in a 13-element array operation.

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Patrick M. Koch, Philippe Raffin, Yau-De Huang, Ming-Tang Chen, Chih-Chiang Han, Kai-Yang Lin, Pablo Altamirano, Christophe Granet, Paul T. P. Ho, Chih-Wei L. Huang, Michael Kesteven, Chao-Te Li, Yu-Wei Liao, Guo-Chin Liu, Hiroaki Nishioka, Ching-Long Ong, Peter Oshiro, Keiichi Umetsu, Fu-Cheng Wang, Jiun-Huei Proty Wu. 2010-12-17. 1.2 Meter Shielded Cassegrain Antenna for Close-Packed Radio Interferometer. https://doi.org/10.1086/658675

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