ANTENNA DEVICE

摘要

PROBLEM TO BE SOLVED: To provide the antenna device of a plural frequency operation system, capable of keeping a tilt angle fixed with simple constitution. SOLUTION: A circular ground plate 103 and a ring-like ground plate 104 are connected via plural lumped constant circuits 102. On the circular ground plate 103, a monopole antenna 101a as an antenna element and a wave guide 101b are provided so as to be almost vertical to a main surface. The lumped constant circuits 102 perform electrical coupling or interruption between the circular ground plate 103 and the ring-like ground plate 104 corresponding to an excitation frequency to the monopole antenna 101a.