Beam Mode Expansion of Corrugated Conical Horns with Phase Correcting Lens: Application to Radioastronomy Receivers |
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| Authors: | E García L De Haro C O'Sullivan G Cahill J A López Fernández F Tercero B Galocha J L Besada |
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| Institution: | (1) Grupo de Radiación, Dept. S.S.R., Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid, Spain. legarcía@tsc.uc3m.es;(2) Department of Physics, National University of Ireland, Maynooth, Maynooth, Co. Kildare, Ireland;(3) Centro Astronómico de Yebes, Instituto Geográfico Nacional, Yebes, Guadalajara, Spain |
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| Abstract: | A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower
the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes
modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the
horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on
the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME).
Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical
Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct
application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for
the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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| Keywords: | beam mode expansion quasi-optical systems radioastronomy radiotelescope |
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