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© 2003 Wiley Periodicals, Inc.
STUDY OF AN OPTICAL SOLUTION
FOR THE NEW 40-m
RADIOTELESCOPE OF THE CENTRO
ASTRONO
´
MICO DE YEBES
E. Garcı ´a,
1
L. De Haro,
1
J. A. Lo´ pez Ferna´ ndez,
2
F. Tercero,
2
B. Galocha,
1
A. Barcia,
2
and J. L. Besada
1
1
Grupo de Radicio´ n, Escuela Te´ cnica Superior de Ingenieros de
Telecomunicacio´n
Universidad Polite´ cnica de Madrid
Ciudad Universitaria, 28040, Madrid, Spain
2
Centro Astrono´ mico de Yebes
Observatorio Astrono´ mico Nacional (OAN)
Yebes, Guadalajara, Spain
Received 17 October 2002
ABSTRACT: In this paper a solution for the focalization of the new
40-m radiotelescope at the observatory of the Centro Astrono´mico de
Yebes (CAY) in Guadalajara, Spain, is presented. Quasi-optics theory is
used in this paper for the propagation analysis of the beams through the
different optics elements. The goal of this paper is to design an optical
system that can focalize several bands in order to reduce to the mini-
mum number of possible optic elements, and share the maximum num-
ber of them. Parameters for hyperbolic lenses and ellipsoidal mirrors,
focal distances, and the feeder dimensions necessary for the focalization
in each band are calculated. © 2003 Wiley Periodicals, Inc. Microwave
Opt Technol Lett 37: 121–123, 2003; Published online in Wiley Inter-
Science (www.interscience.wiley.com). DOI 10.1002/mop.10842
Key words: radioastronomy; radiotelescope; focalization; quasi-optics;
Gaussian beam
1. INTRODUCTION
This paper presents a study of the focalization of the new 40-m
radiotelescope of Centro Astrono´mico de Yebes (CAY), in Spain
which may operate at S, X, K, and millimeter bands, using a
multiband feed system with minor mechanical changes on a clas-
sical Cassegrain-type radiotelescope. The geometry of this Casse-
grain antenna radiotelescope consists of a 40-m parabolic main
reflector with f / D 7.909. The distance between the subreflector
vertex and the Cassegrain focus is 25.396 m, with a subreflector
diameter of 3.28 m.
In radioastronomy there are several scientific observation bands
of interest, from 2 GHz up to higher than 300 GHz [1, 2].
Therefore, it is necessary to conduct an individualized study of the
problem, for each observation band, in order to design the feeds
and the focalization elements, such as lenses and conic or plane
mirrors [1, 3, 4]. This paper relates the necessity of the focalization
of the new 40-m Cassegrain radiotelescope of the Centro Astro-
no´mico de Yebes in Spain.
The receiver cabin poses a dimension constraint for all the
receivers, thus it is suitable to share the maximum number of
focalization elements for each observation band. Figure 1 shows
the receiver cabin and its physical dimensions [5].
2. QUASI-OPTICS REVIEW
Quasi-optics (QO) theory studies the propagation of Gaussian
beams in free space whose transversal extent is restricted in terms
Figure 2 Lateral view of the radiotelescope receiver cabin. [Color figure
can be viewed in the online issue, which is available at www.interscience.
wiley.com.]
Figure 1 Radiotelescope receiver cabin. [Color figure can be viewed in
the online issue, which is available at www.interscience.wiley.com.]
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 37, No. 2, April 20 2003 121