DIGITAL SIGNAL DETECTION SYSTEM

• Main Author: NAKAMURA SEIZO
• Format: Patent
• Language: English
• Published: 14.05.1990
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

PURPOSE:To surely detect the presence of a digital signal by setting a reference voltage of an analog comparator in advance properly. CONSTITUTION:A radio wave subject to frequency modulation (FSK) by a digital signal is caught by a reception antenna 1, frequency-detected and a digital signal is outputted from a data output terminal 11. A pulse outputted from a change point detection circuit 16 passes through a band pass filter 17 whose band width is sufficiently narrow, its envelope is detected by an envelope detector 122, and after the AC component is eliminated by a low pass filter 13, the result is compared with a reference level by an analog comparator 14 and when the level is discriminated to be larger than the reference level, a signal detection output representing the presence of the digital signal is outputted at a signal detection output terminal 15. On the other hand, when no radio wave comes to the reception antenna 1, no digital signal is outputted from an analog comparator 10 and only random noise is outputted. Thus, a signal detection output representing the presence of a digital signal is not outputted from the analog comparator 14.