Primary radiator suitable for size reduction and preventing deterioration of cross polarization characteristic

摘要

A dielectric feeder has a holding portion inserted into the interior of a waveguide and a horn-shaped radiating portion having different radiation angles in major- and minor-axis directions. A plurality of annular grooves each having a depth corresponding to about a quarter wavelength of a radio wavelength lambd0 is formed in an end face of the radiating portion. An outer peripheral surface of the holding portion is cut out at circumferentially opposed positions axially in parallel with each other to form a pair of flat surfaces. Both flat surfaces are positioned in the major axis directions of the radiating portion and are thereby allowed to function as a phase compensating portion for compensating a propagative phase difference induced in the radiating portion. Further, there is formed a stepped hole comprising two recesses which are contiguous to each other from an end face of the holding portion toward the interior of the holding portion. The recesses are each set at a depth corresponding to about a quarter wavelength of a radio wavelength lambd∈ and are thereby allowed to function as an impedance converting portion.