Beam Mode Expansion of Corrugated Conical Horns\ud with Phase Correcting Lens: Application to\ud Radioastronomy Receivers

摘要

A classical radioastronomy receiver is fed with a corrugated horn and an independent lens,\udboth placed in a cryostat to lower the noise temperature. The beam is focused and directed using a\udcombination of elliptical and plane mirrors. This paper proposes modifying the initial feeding system\udby placing the lens onto the horn aperture, thereby allowing a size reduction of the horn and lens, and a\udsimplification of their mechanical design. The profiled lens is shaped to correct the phase error on the\udhorn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam\udMode Expansion (BME). Results using both a hyperbolic-planar lens and a spherical-elliptical lens,\udas well as results obtained by using Geometrical Optics (GO) with a Kirchoff–Huygens integration\udto get the far-field pattern, have been compared with measurements. As a direct application, a full\udfocusing system for the new 40-m radiotelescope at the “Centro Astron´omico de Yebes” is presented\udfor the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn\udwith a phase-correcting lens.