PURPOSE: To provide a satisfactory directional characteristic without damaging a gain/efficiency characteristic by installing a ground conductor on an antenna circuit substrate through a dielectric and installing a radio wave absorber at the externally peripheral surface of an antenna.
CONSTITUTION: The ground conductor 1 and the antenna circuit substrate 3 are installed on the surface of the ground conductor 1 through the dielectric 2a and the ground conductor 4 having an opening 7 for radiating a radio wave through the dielectric 2b is installed on the surface. The radio wave absorber 14 is installed at the externally peripheral end part of the antenna. It is desirable that a distance L from the center of the antenna elements arranged at the outermost periphery to the radio wave absorber 14 is a position equivalent to the arrangement interval of the antenna elements, and the rubber of a ferrite system is desirable for the absorber 14. Thus, a power component radiated from the externally peripheral part of the antenna can be removed and the plane antenna having the superior directional characteristic can be provided without the rise of a side robe level on account of unnecessary radiation even in the area of 40°-90° of the directional characteristic.
ISHIZAKA HIRONOBU
MIZUGAKI HISAYOSHI
