Dual-band reflector feed system for classical Cassegrain radio telescopes

The authors describe a dual-band feed system, operating at S - and X-band, that can be temporarily mounted and used in a classical Cassegrainian-type radio telescope without removing the existing feed systems. The feed system, designed to give as high efficiency as possible in both bands, consists of two offset primary-fed parabolic reflectors, one for each frequency band. The X-band reflector, located behind the S-band reflector, radiates through a plane dichroic surface that replaces the central part of the S-band reflector. The feed system is to be used for space geodesy utilizing the very-long-baseline interferometry (VLBI) technique and has been tested and used at a radio telescope in Chile. Results of both a theoretical design study and measurements are given