| 摘要 |
PROBLEM TO BE SOLVED: To prevent interference with an adjacent lane and to attain cost down or the like by providing plural band pass filters, with which received signals from the adjacent lanes are removed on different pass bands, and selecting any one of filters as a received signal route at the moment when a carrier frequency received by on-vehicle equipment is recognized. SOLUTION: At transmission timing, the route of signals is switched to a modulator 5 by a switch 3 and transmission data are added to a carrier signal from an oscillator 13 by the modulator 5, amplified and radiated from a transmission antenna 7 later. On the other hand, signals from on-road equipment are received by a reception antenna 8 and low noises are amplified by a low noise amplifier 9. At the moment when the frequency of carrier wave received by the on-vehicle equipment is recognized, switches 4 and 14 change the pass band and select any one of band pass filters 15 and 16 for removing the received signals from the adjacent lanes as the route of received signals. While receiving the outputs of switches 14 and 3, an intermediate frequency(IF) signal is generated by a mixer 10, amplified by an IF amplifier 11 and detected by a detector 12 later. |
