ANTENNA DEVICE

摘要

A small-sized antenna having two or more feeding ports. A radiator consists of a planar conductor of an almost circle the diameter of which is about half the wavelength, or of an almost regular polygon the diagonal of which passing through the center is about half the wavelength long. A ground plate is disposed opposite to the radiator. The feeding ports are, respectively, connected on the radiator to the feeding points located on two orthogonal segments passing through the center of the radiator. This antenna is used as not only a single-unit antenna, but also two independent antennas where isolation between the feeding ports is secured. Thus, a small-sized two-unit antenna device is obtained. The radiator is formed into a rimmed hat in a stepped impedance resonator (SIR) structure where the diameter of the hat's crest is a 1/4 wavelength, resulting in a reduction in the size of the radiator.