| 摘要 |
PURPOSE:To prevent a detecting operation error by constituting so that FM is detected by outputting a receiving signal when there is a receiving signal, and outputting a signal of the same frequency as that of a transmission signal when there is no receiving signal. CONSTITUTION:A receiving signal (e) is input to the level detection circuit 10, and obtains a receiving conversion signal (f) of the same frequency as that of the receiving signal (e). At the same time, it is also sent to the pulse generating circuit 11, and obtains an output signal (g). These signals (f), (g) are sent to the signal switching circuit 12, and when the receiving signal (e) exceeds the threshold level, frequency of the receiving signal (e) is output, and when it is smaller than the threshold level, a signal of the same freqency as that of a transmission signal is output. A signal (h) which has been mixed in this way is input to the level detector 15 through the FM detection circuit 13, etc. At the same time, the integrating circuit of the pulse width detection circuits 16, 17 is reset through the level detection circuit 25, etc. Accordingly, the pulse width of a low frequency component generated by a moving object is detected, and the moving object is recognized. A detection error can be prevented by such a constitution. |
