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US 5,471,507 AGranted
Circuit for detecting object signal from input signal
AssigneeFujitsu Limited
InventorsYutaka Awata, Mitsuo Kakuishi
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Abstract
An input analog signal having a periodicity is converted into one-bit digital signals by an A/D converter (42), and the one-bit digital signals are converted into parallel signals by a serial-to-parallel converter (43). A correlation between the parallel signals and a reference signal string is detected by a correlation device (45). When the correlation is detected, a hold circuit (48) holds detection of the correlation and hence outputs a tone signal detection result. With the above simple, low power consumption circuit structure, the tone signal can be detected.
Claims7
A signal detection circuit comprising:
- A/D conversion means for converting an analog signal having a periodicity into one-bit digital signals;
- serial-to-parallel converting means for converting the one-bit digital signals into parallel signals of a predetermined number of bits by using a clock signal having a frequency equal to at least twice that of a detection object signal, the predetermined number of bits corresponding to a number of bits of the detection object signal;
- correlation means for detecting a correlation between the parallel signals and a reference signal string indicating a signal component of the detection object signal;
- and
- hold means for holding a state of detection of the correlation when an output signal of the correlation means becomes indicative of the state of detection of the correlation at least one time in a period of the detection object signal.
2 more elements
Dependencies are inferred from the claim text.