| 摘要 |
PROBLEM TO BE SOLVED: To detect a transmission trigger signal from a received signal while a transmitted signal and the transmission trigger signal are not input from the outside by a method wherein the transmission trigger signal is output when a pilot signal contained in the received signal is at a prescribed level or higher and when it is detected that the pilot signal is continued for a prescribed time or more. SOLUTION: A pilot-signal detection circuit 801 extracts only a pilot signal from a received signal so as to be output to this transmission-trigger detection circuit 802 at the later stage. The transmission-trigger detection circuit 802 monitors the input pilot signal so as to detect a transmission trigger signal, and it outputs the detected transmission trigger signal to a signal processing circuit 803 at the later stage. In the signal processing circuit 803, a signal processing operation is performed by using the received signal on the basis of the transmission trigger signal which is detected by the transmission-trigger detection circuit 802, and a result is found so as to be output to a display 804 at the later stage. The display 804 displays a frequency analysis result and an active sonobuoy signal detection result which are found by the signal processing circuit 803.
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