Multiband feed using coaxial configuration

In a communication satellite, multiple frequency bands are used for transmitting and receiving communication, data and tracking signals. In this paper we present design, analysis and test results of a dual-aperture coaxial multiband feed horn. The coaxial configuration is particularly useful for the frequency bands that are widely separated. Our design goal was to operate at S-, Ku-, K- and Ka-bands. In our design the Ku through Ka bands are launched through a multiflared circular horn while the S band is launched through a stepped and flared coaxial horn sharing a common axis with the circular horn (Fig. 1). A method of moment (MoM) based software is developed to analyze the structure. It is found that for the S-band, the aperture impedance significantly affects the electrical performance. For the high frequency bands, the mutual coupling between the circular and coaxial apertures plays an important role on the performance. The simulated results including mutual coupling effects agree well with the measured data. This multiband feed design allows a compact, low weight, single offset reflector configuration as opposed to a Cassegrain antenna system that requires two separate feeds and a dichroic subreflector to accommodate multiple bands.