| CPC H04B 7/145 (2013.01) | 16 Claims |

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1. A passive relay device which relays wireless communication between an inside of a radio wave shielding structure and an outside of the radio wave shielding structure, the inside of the radio wave shielding structure defining a first enclosure with an outer edge and a height measured perpendicular to the outer edge, and a second enclosure adjacent to the first enclosure, the passive relay device comprising:
an internal antenna which connects with the inside, the internal antenna including a directional antenna disposed in the first enclosure and directed toward the second enclosure located farther from the internal antenna than the first enclosure, the directional antenna having a directionality with respect to a radio wave reception angle that is adjustable based on a distance from the passive relay device to the outer edge of the first enclosure and the height of the first enclosure;
an external antenna which connects with the outside; and
a connection part which connects the internal antenna and the external antenna.
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