Wave transmission lines and networks – Coupling networks – Frequency domain filters utilizing only lumped parameters
Patent
1992-09-25
1994-04-19
Ham, Seungsook
Wave transmission lines and networks
Coupling networks
Frequency domain filters utilizing only lumped parameters
333174, 333181, H03H 706, H03H 3013
Patent
active
053049632
ABSTRACT:
A filter circuit for an electromagnetic pickup can always generate a noise-filtered output signal of a high resolution without any substantial degradation of an S/N ratio even if the frequency of low-freqeucny noise components contained in an output of an electromagnetic pickup, increases in accordance with the increasing rotational speed of the rotating shaft. The filter circuit includes a low-pass filter 2 for filtering high-frequency noise components contained in the output signal from the electromagnetic pickup, and a high-pass filter 3 for filtering low-frequency noise components having frequencies lower than a predetermined cut-off frequency. The high-pass filter 3 comprises a capacitor 131 inserted in a signal line connected to the low-pass filter 2, a plurality of resistors 132, 133, 134 connected to the signal line 140 in parallel relation with respect to each other, and a plurality of switches SW1, SW2 connected to the corresponding resistors for switching on and off electrical connection of the corresponding resistors to the signal line in dependence upon the output voltage of the electromagnetic pickup. The switches are sequentially switched on in accordance with an increase in the output voltage of the electromagnetic pickup whereby the cut-off frequency of the high-pass filter is increased in accordance with the increasing output voltage of the electromagnetic pickup.
REFERENCES:
patent: 3813559 (1974-05-01), De Boer
patent: 4163385 (1979-08-01), Kato et al.
patent: 4487059 (1984-12-01), Fischer et al.
Ham Seungsook
Mitsubishi Denki & Kabushiki Kaisha
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