Beam mode expansion applied to horn system with meniscus lens: new application to radioastronomy receivers

Classical radioastronomy receivers are fed by a corrugated horn and independent lens, both of them placed in a cryostat to lower noise temperature. In addition, the beam is focused and driven using several elliptical and plane mirrors. The paper proposes to modify the initial feeding system, placing the lens onto the horn aperture, allowing a size reduction of the horn and lens and a simplification of their mechanical design. This profile lens is designed to correct phase error at the horn aperture. A quasi-optical model of horn plus lens system using beam mode expansion (BME) has been developed. Results using a spherical-elliptical lens and those from optical geometry theory (GO) have been compared.