Publication:

ASTRA 3B horn antenna design

The ASTRA 3B satellite includes 60 Ku-band state-of-the- art transponders and 4 Ka-band transponders. The spacecraft have been designed for the distribution of both direct-to-home (DTH) broadcast services and two way broadband services across Europe. After Astra 2B and Astra 1M, Astra 3B is the third Astra satellite to be built by ASTRIUM. Two different horn antennas, for Ku- and Ka-bands, were designed with very stringent requirements as it is usually required for space applications. For the horns the cross-polar levels should be below -45 dB, and the return loss below -30dB for all frequency bands. Normally the horn aperture is fixed by the required illumination of the reflector edges, so it is difficult to reduce the aperture size of a horn antenna. Nevertheless, thanks to the design technique used, the relation between the output aperture and the total horn length for the Ka-band was approximately 0.56 and for the Kuband was something like 0.76. This means that the lengths of the horn antennas are 1.8 and 1.32 times the respective apertures. Furthermore, the taper and the phase center movement inside the respective bandwidths could be controlled and limited to certain limits during the optimization procedure, obtaining a very efficient configuration when they were combined with the reflectors. The horn antennas were based on the combination of horizontal and vertical corrugations and they were designed by the Antenna group of the Public University of Navarra.