In the present book, the high cross-polarization of the offset parabolic reflector has been suppressed by using a multi-mode matched feed. The concept of matched feed is thoroughly described at the beginning of the book. The multi-mode matched feed has been realized in three different waveguide structures, i.e., rectangular, cylindrical and corrugated structure. The detailed designs of all the three matched feed structures have been presented in the book. Through extensive numerical as well as experimental results, it has been verified that the proposed matched feeds effectively suppress the undesired high cross-polarization of the offset parabolic reflector antenna. The feeds also remove the beam squinting in the secondary radiation pattern of the reflector, when circular polarization is employed. Finally, a few practical applications of the proposed feeds are discussed and the corresponding results are summarized.