Performance of offset parabolic reflectors illuminated by matched feeds

The theoretical concept of applying matching primary feed devices to illuminate offset parabolic reflectors is studied. The physical interpretation of how this new class of feeds compensates for the geometric asymmetry of the offset system is explained. An economical technique to investigate the corresponding improvements in the near-axis radiation is given by suitably extending the modified stationary phase method, suggested in the literature, to the added modal behaviour of these feeds. The analytical developments and their respective novel results are accumulated relative to the main and basic parameters of offset antenna systems. The presentation is given in some detail so that it may be a useful paper for a wider group of readers.