| 摘要 |
<p>PURPOSE:To raise an alarm, by setting a range cut distance depending on the speed of vehicle and by detecting a body having entered into the range cut distance. CONSTITUTION:The received signal fC1 of reflected waves received from a body DA by an antenna 106 has a propagation lag time tau1=2R1/C<=Tw in comparison with the transimtted signal fR and has a frequency fR1=fT+Cd1. The received signal fC2 of reflected waves received from another body DB by the antenna 106 has a propagation lag time tau2=2R2/C>Tw and has a frequency fR2=fT+Cd2. These received signals are applied to a mixer 107 through a circulator 105 and then synchronously detected by station-transmitted signal SL supplied from a directional coupler 102, thereby obtainng video signals fd1, fd2 of period Tp. A pulsating signal ff is passed through a filter 111 so that its high frequency component fp=1/Tp is removed.</p> |
