Two radiating systems for generating a scanning high power microwave beam are presented. The first one uses beamwaveguide to feed an offset paraboloid antenna, which is suited for overmode input waveguide. The second consists of an offset paraboloid antenna fed by a multimode horn that is linked to a vacuum flexiable elliptical waveguide as a method of limited elevation scan, which is simple and suited for the transmitter with single mode output waveguide. The physical optics analysis technique is used to investigate above antennas. The numerical results shows that the gains and spillover efficiencies are reasonable.