| 摘要 |
PROBLEM TO BE SOLVED: To reduce the side robe of a radiation pattern with respect to a primary radiator having a horn part at one end of a waveguide. SOLUTION: A primary radiator has a waveguide 1, in which a conical horn part 1a is installed at one end and a blocking face 1b is installed at the other end and whose cross section is circular and first and second probes 2 and 3 inserted inside from the wall face of the waveguide 1. Plural notch parts 4 are formed at the opening end of the horn part 1a. The plural notch parts 4 are arranged at symmetrical positions, centering the shaft center of the waveguide 1. The depth of the notch parts 4 is set to be about 1/4 wavelength of thatλ0 of a radio wave transmitted through air. Thus, the phases of surface current flowing in the notch parts 4 and the adjacent projecting parts (parts without notch parts 4) become opposite and the side robe of a radiation pattern is reduced substantially.
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