Antenna device

An antenna device, comprising:

• a ground plate made of a conductor with a flat plate shape;
• an opposing conductive plate made of another conductor with a flat plate shape, arranged to space apart from the ground plate by a predetermined distance, and electrically connected to a power supply line;
• and
• a plurality of short-circuit pins configured to electrically connect the opposing conductive plate and the ground plate,
• wherein
• one end of each of the plurality of short-circuit pins extends to a conductive plate plane, which is a plane including the opposing conductive plate, and the other end of each of the plurality of short-circuit pins extends to a ground plate plane, which is a plane including the ground plate,
• the opposing conductive plate and the ground plate are connected by selecting one or more of the plurality of short-circuit pins,
• the plurality of short-circuit pins have different distances from a center of the opposing conductive plate to an end of each of the plurality of short-circuit pins on the opposing conductive plate,
• a short-circuit pin of the plurality of short-circuit pins having a longer distance from the center of the opposing conductive plate to an end of the short-circuit pin on the opposing conductive plate having a larger short-circuit pin cross-sectional area,
• the antenna device resonates in LC parallel at a resonance frequency determined by an inductance provided by selecting one or more of the plurality of short-circuit pins and a capacitance between the opposing conductive plate and the ground plate so as to generate an electric field perpendicular to the ground plate and the opposing conductive plate, and
• by selecting one or more of the plurality of short-circuit pins, a radiation gain of linear polarization in a vertical direction of the ground plate is adjusted.