Advanced imaging antenna for satellite applications at L-band

The author discusses the application of the NFA (near-field antenna) concept to an antenna system capable of handling several missions at L-band. In particular it has to assure a so-called regional mission, which implies the coverage of at least 20% of the global field-of-view by means of 8 to 20 spots, depending on the area of coverage of each beam. Moreover a spot-beam global coverage must be set up with such an antenna, guaranteeing in both cases a minimum isolation of 20 dB for frequency reuse applications. The shape of the reflector, the feed cluster layout, and the excitation coefficients have been optimized, in order to satisfy both the electrical and the mechanical requirements. The results presented tend to confirm the validity of the near-field approach, even in the case of a large coverage sector (+or-8.7 degrees ), but using a minimum degree of reflector shaping.<>