| 摘要 |
PURPOSE:To enable the detection of an object by using a higher harmonic receiver even when a jamming wave having frequency same to usual transmission frequency gets in, by parallelly arranging a receiver for receiving higher harmonics with transmission frequency other than a receiver for receiving a signal having frequency same to usual transmission frequency. CONSTITUTION:When a jamming wave having frequency same to transmission frequency gets in, a jamming signal and a real receiving signal returned from an object by reflection are mixed in the output of a transmission wave receiver 3 and the detection of the object becomes difficult. In this case, a selection circuit 7 selects the signal of a higher harmonic receiver 6 with respect to only a place where the detection of the object becomes difficult by the information from a jamming wave detecting circuit 8 to send the same to an indicator 4. A transmission signal is a signal obtained by using certain determined frequency but generally contains a considerable higher harmonic component having frequency twice as compared with the transmission frequency. Therefore, the receiving signal returned from the object by reflection also has the twice higher harmonic component other than the transmission frequency component and, if conversion, the amplification and the detection of frequency are subjected to signal treatment by using the higher harmonic receiver 6 for receiving said frequency signal, the object can be detected similarily as the transmission frequency receiver 3. |
