Design of a dichroic surface for dual-frequency radioastronomical observations

The design of a law-loss, frequency-selective surface (FSS) for dual-frequency radioastronomical applications is discussed in this paper. The dichroic surface is inserted between the subreflector and the receiver-which is located at the secondary focus of the radiotelescope-to split the main beam of the antenna into two, and direct them toward receivers operating at X- and K-ba,lds, enabling simultaneous observation of arbitrarily polarized radio signals at these frequencies. Particular attention has been devoted to minimizing the overall attenuation introduced by the screen, which plays a critical role in determining the noise temperature of the radiotelescope. (C) 1999 John Wiley & Sons, Inc.