Patent ID: 7855689

Claim:
An antenna apparatus comprising: a ground plane having a band gap surface on a first side of the ground plane such that the band gap surface is conductive and substantially prevents propagation of electromagnetic waves set within a specific frequency band; and a traveling-wave linear antenna, disposed over the band gap surface on the first side of the ground plane and spaced away from the band gap surface, which linear antenna radiates electromagnetic waves of an operational frequency placed within the specific frequency band in response to an alternating current of the operational frequency inputted to the linear antenna to output a communication signal contained in the alternating current, wherein the linear antenna has a first center portion extending straight in a first direction, a first side portion extending straight from an end of the first central portion substantially at an angle of 90 degrees to the first direction and a second side portion extending straight from another end of the first central portion substantially at an angle of 90 degrees to the first direction so as to be substantially formed in a U shape and to radiate circularly polarized electromagnetic waves.