Ka-band feed arrays for spacecraft reflector antennas with limited scan capability-an overview

The design and breadboard of an active transmitting array at Ka-band frequencies and its application to a reflector antenna system is described. The array is intended as a feed array in a near-field Cassegrain or Gregorian dual-reflector antenna system. It uses tapered slot (Vivaldi) elements in a break architecture. The array has been tested for RF performance. Its performance is acceptable, but there are some areas where improvements in the performance are possible. It was found that particular attention must be paid to the losses at the input to the array elements and in the element itself. Variation of the array phase center in different azimuth planes is another area of concern. The Vivaldi elements have a linear polarization and do not lend themselves easily to a circularly polarized arrangement. For lower losses and circular polarization, microstrip patch arrays in a tile configuration were found to be more advantageous.<>