Patent ID: 7505011

Claim:
An antenna apparatus comprising a dielectric substrate that has a predetermined dielectric constant; and a conductive layer that is formed on a surface of said dielectric substrate, wherein: on said conductive layer, a plurality of rhombic slot antenna sections are provided in which each rhombic slot antenna section comprises four slot elements having lengths of approximately ¼ of a wavelength to approximately ⅜ of a wavelength of a used frequency and arranged in a rhombic shape, and of the four slot elements, a first slot element and second slot element are connected, and a third slot element and fourth slot element are connected; said plurality of rhombic slot antenna sections are connected by a slot linking element having a predetermined length and forming a linked plurality of rhombic slot antenna sections; a folded-back slot detour element having a predetermined full length is connected to each end of the linked plurality of rhombic slot antenna sections; and a plate reflector is arranged at a predetermined distance from the surface of said dielectric substrate, and approximately parallel to the surface of said dielectric substrate, said antenna apparatus further comprising: a first feed point that feeds power to a junction of said first slot element and said second slot element of one of said plurality of rhombic slot antenna sections; a second feed point that feeds power to a junction of said third slot element and said fourth slot element; and a switching section that switches selectively between said first feed point and second feed point.