| 摘要 |
PURPOSE:To enable a mobile station to simultaneously detect the position of its own vehicle against a road station so as to save the labor and time required for installing beacons for detecting positions by making the mobile station to obtain communication data by receiving communication waves transmitted from the road station and, at the same time, to measure the intensity of the electric field so as to detect the maximum value. CONSTITUTION:A road station 10 transmits communication data after modulation on a carrier of, for example, sub-microwaves. The radio waves are radiated toward the area of 50-100 m in radius around a position P immediately below an antenna 14. The on-vehicle device 20 of a vehicle 12 receiving the radio waves amplifies signals received through a nondirectional antenna 22 to a desired level by means of a high- and intermediate-frequency sections 24 and 26. An RSSI level generation circuit 32 detects the intensity of the output signal receiving electric field of the section 26. The output waveform of the circuit 32 increases in level value as going closer to the position P immediately below the antenna 14 of the road station 10 and, after passing the position P, the level value again decreases and the waveform changes.
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