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Patent Searching and Data


Title:
SIGNAL DETECTION CIRCUIT
Document Type and Number:
Japanese Patent JPS62137905
Kind Code:
A
Abstract:

PURPOSE: To improve the signal detection accuracy and to decrease much the variation in the detection sensitivity to a threshold fluctuation of a detection section by using a filter section formed by inserting a comparator having a hysteresis characteristic between two BPFs.

CONSTITUTION: A BPF 3 receives plural AC signals V1 having different frequencies, the signals V1 are converted into plural signals V2 whose amplitude is attenuated as the absolute value being the difference between the frequency of each signal V1 and the center frequency is larger and whose logarithmic amplitude is proportional to a logarithmic amplitude of each signal V1. The comparator 4 receives the signal V2 and generates a signal V3 having a prescribed amplitude and the same frequency as that of the signal V2 only when the signal V2 is larger than the 1st threshold value. A BPF 5 converts the signal V3 into a signal V4 having the equal frequency as that of the signal V3 and whose amplitude is attenuated as the absolute value being the difference between the frequency of the signal V3 and the center frequency is larger. A detection section 7 inputs the signal V4 and outputs a detection signal only when the signal V4 is larger than the 2nd threshold value.


Inventors:
UESUGI NORIHIKO
Application Number:
JP1985000279720
Publication Date:
June 20, 1987
Filing Date:
December 11, 1985
Export Citation:
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Assignee:
NEC CORP
International Classes:
H03H7/01; (IPC1-7): H03H7/01