Patent ID: 7215289

Claim:
An antenna device applied to a portable radio terminal whose housing length is equal to or more than λ/4 with respect to the wavelength λ of transmission-reception signals comprising: an antenna element disposed on one end of the housing in the longitudinal direction in which at least one point of one end is connected to a signal wiring pattern on a substrate and the other end is an open end; and a parasitic element disposed on the same side of the housing as the antenna element in which one point of one end is connected to a ground wiring on the substrate and the other end is an open end; wherein the open end of the antenna element and the open end of the parasitic element are approximated each other and capacity coupled, and the antenna element, the parasitic element and the substrate are disposed forming a loop generating a loop current, wherein the loop current flows in a first direction between the substrate and the antenna element, and the loop current flows in a second direction between the substrate and the parasitic element, wherein the first direction and the second direction are opposite to each other.