| 摘要 |
To perform communication speedily and reliably at an increased frequency of communication occurrence when providing multiple antenna units which are set to the same frequency, each of antenna units having a gantry in a tollgate is set such that adjacent antenna units having the same frequency alternately perform communications. Each communication period is set to have a down link period in which an interrogation signal is transmitted and an up link period in which an unmodulated carrier wave is transmitted while a response signal is received. Upon receiving a signal, an on-vehicle device generates a response signal by using a control circuit and transmits the signal by reflection, and fixes a communication party for further communications. The communication cycles of adjacent antenna units are shifted from each other, thereby avoiding interference. The down link periods and the up link periods coincide between the antenna units whose communication areas are apart from each other, thereby avoiding interference. |
