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Read Pulse Compression by Linear Filtering

IP.com Disclosure Number: IPCOM000092834D
Original Publication Date: 1967-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Vermeulen, JC: AUTHOR

Abstract

Read pulses in a magnetic tape or disk unit are compressed by insertion of a pulse-slimming filter between read amplifier 1 and detector 2, as shown at A. Pulse compression is conducive to error reduction and allows higher density of recorded bits. The filter compresses an isolated pulse, as at B, which is characteristic of reading back a single transition in the write current of the unit. Due to the linear nature of the filter, any superposition of such characteristic pulses is then effectively improved as in C. Compression of a read pulse at B is effected by subtraction of two correction pulses. These are properly shifted and attenuated versions of the main pulse itself, such that the wide lower edges of the main pulse are just eliminated.

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Read Pulse Compression by Linear Filtering

Read pulses in a magnetic tape or disk unit are compressed by insertion of a pulse-slimming filter between read amplifier 1 and detector 2, as shown at A. Pulse compression is conducive to error reduction and allows higher density of recorded bits. The filter compresses an isolated pulse, as at B, which is characteristic of reading back a single transition in the write current of the unit. Due to the linear nature of the filter, any superposition of such characteristic pulses is then effectively improved as in C. Compression of a read pulse at B is effected by subtraction of two correction pulses. These are properly shifted and attenuated versions of the main pulse itself, such that the wide lower edges of the main pulse are just eliminated.

The filter circuit comprise s tapped delay line 3 and two operational amplifiers 4 and 5. Delay 3 has a matched termination not shown. The read signal is fed to the entrance of delay 3. A true version of each pulse is derived from the center tap and applied to one input resistor of amplifier 5. A pair of correction pulses of the opposite polarity, applied to the other input resistor of amplifier 5, is added algebraically to the read pulse. Such results in a compressed and inverted output pulse. The correction pulses are composed of an advanced and a delayed version of the identical read pulse, taken from the entrance and terminal taps of delay 3, respectively, and summed and inverted...