Patent ID: 8242970

Claim:
An antenna apparatus comprising: a board that includes: a base part that has a pair of dielectric layers and a conductive layer disposed between the pair of dielectric layers; a plurality of metal plates having the same shape, and that are two dimensionally arranged on one surface of the base part while being spaced apart at even intervals so that the one surface of the base part is configured to be a band-gap surface that blocks propagation of electromagnetic wave within a predetermined frequency band; and a plurality of first connection parts electrically connecting the conductive layer with the plurality of metal plates, respectively; and a line antenna that is located on a band-gap surface side of the board, is arranged along the band gap surface, and is configured to receive and transmit the electromagnetic wave within an operating frequency band, wherein the operating frequency band is within the predetermined frequency band, wherein the plurality of first connection parts include a plurality of first adjustment circuits, respectively; the plurality of first adjustment circuits include a plurality of variable capacitance diodes, respectively, and are configured to individually adjust respective impedances between the conductive layer and the plurality of the metal plates; the plurality of first adjustment circuits further include a plurality of capacitors for preventing short-circuit between the plurality of metal plates and the conductive layer under a predetermined condition, respectively; and the plurality of capacitors are connected between the plurality of variable capacitance diodes and the plurality metal plates, respectively.