Abstract: An antenna device includes an array antenna configured to radiate a radio wave. The array antenna includes at least four radiating elements arranged substantially parallel to a beam scanning plane of the radio wave. The at least four radiating elements are arranged substantially parallel to a first principal surface of window glass for a building, with the antenna device arranged such that the array antenna is arranged at the first principal surface of the window glass in a non-contact manner and such that the radio wave is radiated toward a second principal surface of the window glass opposite from the first principal surface.

Abstract: A reflector system, an active reflector, and a method of positioning an active reflector are provided, whereby dead zones can be cancelled efficiently. The reflector system includes: a first active reflector having a first reflecting surface configured to reflect, at a variable reflecting angle, radio waves transmitted from a transmitter, at least a part of the first reflecting surface being in a boundary area located at a boundary between a line-of-sight area and a non-line-of-sight area formed by one or more obstacles that block the radio waves from the transmitter; and a second active reflector having a second reflecting surface configured to reflect, at a variable reflecting angle, the radio waves from the transmitter or the radio waves reflected by the first active reflector, the second reflecting surface being provided in the non-line-of-sight area, or at least a part of the second reflecting surface being provided in the boundary area.

Abstract: A protective plate-equipped reflective member includes a reflective member that reflects or re-radiates a radio wave incident thereon; and a protective plate that is installed on a radio wave-incident side of the reflective member, wherein d=?×?0/(1.75×?r0.555) and ? is greater than or equal to 1 and less than or equal to 1.25, where a wavelength specified with respect to an operating center frequency f0 [Hz] is denoted by ?0 [mm], a plate thickness of the protective plate is denoted by d [mm], a relative permittivity of the protective plate at the operating center frequency f0 [Hz] is denoted by ?r, and a constant is denoted by ?.