| 摘要 |
<p>PURPOSE:To immediately conclude a moving object as an illegal invader when a warning is issued against the object by modulating the phase of radio waves by of a specific code when the radio waves are issued to a moving object to which no warning is required from an invasion watching device. CONSTITUTION:When radio waves from an antenna 30 reach a moving object 71 fitted with a responder 80, the radio waves are reflected by the object 71 after receiving a Doppler frequency shift and, at the same time, radio waves which are modulated by means of a specific code from the responder 80 are reflected. While the Doppler-frequency shifting frequency to an ordinary moving object 70 is low, the frequency of the specific code can be made appropriately higher. Therefore, characteristics of a low-pass filter (LPE) 50 and band-pass filter (BPF) 51 are set so that the Doppler-frequency shifting frequency and frequency of the specific code can respectively pass through the LPF 50 and BPF 51 only. Then, when the radio waves of the antenna 30 reach the moving object 71, the LPF 50 and BPF 51 simultaneously output and a controller 90 controls a warning device 60 so that the device 60 cannot be actuated when reflected waves match the specific code.</p> |
