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US 4,910,799 AGranted
Noise reduction apparatus
AssigneeFujitsu Ten Limited
InventorKazuo Takayama
Life of this patent
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Abstract
A noise reduction apparatus in which an input signal is supplied to a first signal path (2) including a variable low-pass filter (2) and a second signal path (1), a control circuit (4) control is such that a cut-off frequency of the variable low-pass filter (2) is varied in accordance with a frequency of the input signal S(1), and an output signal is obtained from the first signal path when noise is generated and from the second signal path when noise is not generated.
Claims16
A noise reduction apparatus for removing noise superimposed on an input signal having a phase and a frequency including a major component, comprising:
- noise detecting circuit means for detecting the noise in the input signal;
- first signal path means including a variable low-pass filter having a variable cut-off frequency that varies in response to a control signal, for receiving the input signal and for providing an output responsive the input signal and said variable cut-off frequency so that the output includes all frequencies below the cut-off frequency;
- second signal path means for receiving and providing as an output the input signal;
- control circuit means for providing the control signal for controlling the cut-off frequency of said low-pass filter such that said cut-off frequency is varied in accordance with the frequency of the input signal;
- and
- selecting circuit means for selecting the output signal from said first signal path means when noise is detected by said noise detecting circuit means and for selecting the output signal from said second signal path when the noise is not detected.
3 more elements
Dependencies are inferred from the claim text.