Study of corrugated Winston horns

Smooth walled Winston horns have been extensively used as light collectors for bolometric instruments. Used in multimoded operation without a waveguide, the beam shape is top-hat like and a simple equation is sufficient to define its Full Width Half Max. On the other hand, it is well known that corrugated feed horns are more efficient than smooth walled horns and much better well behaved with respect to polarization characteristics and sidelobe rejection. We present in this paper a study of corrugated Winston feed horns which could be used for future Astronomical instruments devoted to Cosmic Microwave Background (CMB) polarization measurements. We show that in this case low cross-polarization can be expected in single moded operation and that they could produce lower sidelobes levels compared to conical or profile shapes.