Read back compensation circuit for a magnetic recording device

Dynamic magnetic information storage or retrieval – General processing of a digital signal – Pulse crowding correction

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360 65, 360 67, G11B 509

Patent

active

042440084

ABSTRACT:
In magnetic recording devices, such as floppy disk drives, operational difficulties in the faithful reproduction of recorded data include peak shifting. The invention overcomes these difficulties by introducing a read back compensation circuit comprising a frequency equalizer which favorably amplifies a certain harmonic of the original read signal. In a recording device using a modified frequency modulation encoding scheme (MFM), for instance, this harmonic would be the second harmonic. In order to minimize the effect of circuit paramater variations the frequency equalizer may be split between two circuits, specifically between the read filter network and the read differentiating network. First switching means connected to the filter network and second switching means connected to the differentiating network are arranged as to change the damping factor and the frequency of the filter and differentiating network. The switching means are controlled in dependence either of the speed of the recording medium or of a track signal indicating the position of the read head.

REFERENCES:
patent: 2901737 (1959-08-01), Stouall, Jr.
patent: 3405403 (1968-10-01), Jacoby et al.
patent: 3436490 (1969-04-01), Roelots
patent: 3465321 (1969-09-01), Reisfeld
patent: 3516066 (1970-06-01), Jacoby
patent: 3568174 (1971-03-01), Jacoby et al.
patent: 3597751 (1971-08-01), Heidecker et al.
patent: 3996614 (1976-12-01), Budejicky
"OEM--Floppy Disk Drive FDD 100-8"--Siemens Corp, OEM Division, Anaheim, Calif.
"OEM--Floppy Disk Drive FDD 200-8"--Siemens Corp, OEM Division, Anaheim, Calif.
"A Method of High Density Recording on Flexible Magnetic Discs" Franchini et al., Computer Design--Oct. 1976.
"Magnetic Recording"--C. E. Lowman--McGraw, Hill Book Co.
Switchable Gain Read Amplifier--Sensenbaugh et al., Vol. 18 #9 2/76, IBM Tech. Dis. Bul.

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