| 摘要 |
PURPOSE:To attain excellent transmission/reception even if a face of a loop antenna of a card type transceiver is directed in any direction by adopting the constitution that at least two loop antennas are provided to a car body so as to transmit/receive signals having a phase difference of 90 deg. to each other. CONSTITUTION:The two loop antennas 10, 19 are provided as the loop antennas of an on-vehicle side controller 2 and a two-way phase shifter 20 is provided to the one loop antenna 19. The phase shifter 20 is of constant resistance/full transmission type and a phase difference of 90 deg. is produced between the input and output. The antenna 10 is provided to a door mirror of the door of the driver's seat and the antenna 19 is incorporated in a back part of the driver's seat. Thus, electromagnetic fields HA, HB generated from the antennas 10, 19 are crossed at the door side of the driver's seat and produced in a direction in parallel on ground. The combined electromagnetic field HT at a point P is a rotating magnetic field (circularly polarized magnetic field) whose direction is rotated by 360 deg. in the period of a carrier signal and when the card type transceiver 1 is placed at the point P, the rotating magnetic field HT orthogonal to the loop face of the loop antenna 3 exists without fail. |
