Programmable filter/equalizer for duel speed and density magneti

Details Programmable filter/equalizer for duel speed and density magneti Programmable filter/equalizer for duel speed and density magneti

1990-11-13

1993-12-14

Hajec, Donald

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Head amplifier circuit

360 61, 360 65, G11B 509, G11B 1512, G11B 5035

Patent

active

052708756

ABSTRACT:
A programmable filter for the read channel of a magnetic recording device filters the sensed signals corresponding to data on magnetic media at at least two different transfer speeds of the magnetic media. The programmable filter, under microprocessor control, selectively switches its filter characteristics without affecting the quality of the filter but changing the cut-off frequency so as to correspond to the two different transfer speeds. The programmable filter of the present invention utilizes solid state switches to implement the switching of the filter characteristics to change the cut-off frequency without affecting the quality. The programmable filter is inductorless and is designed only with resistors and capacitors arranged in a filter network. The programmable filter does not use operational amplifiers, using instead low cost transistors in an emitter-follower configuration. The cut-off frequency of the filter is changed by adding resistance or capacitance in series or in parallel with existing resistances and capacitances in the resistor-capacitor network so as to change the cut-off frequency without affecting the quality. The programmable filter of the present invention provides pulse slimming thereby reducing intersymbol interference, provides sharp roll-off characteristics to minimize higher frequency noise, and produces a voltage output corresponding to the sensed data signals as well as a differentiated voltage output having the identical delay as the voltage output.

REFERENCES:
patent: 4244008 (1981-01-01), Holt
patent: 4314288 (1982-02-01), Gyl
patent: 4371901 (1983-02-01), Shah
patent: 4656533 (1987-04-01), Sakai et al.
patent: 4894734 (1960-01-01), Fischler

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