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Modified Double Frequency Type Recording

IP.com Disclosure Number: IPCOM000093911D
Original Publication Date: 1966-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Schneider, RC: AUTHOR

Abstract

Compensation for signal distortion in double-frequency types of recording is provided in this method of recording information. The signal distortion takes the form of peak shift, baseline shift and extensive variations in dynamic range.

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Modified Double Frequency Type Recording

Compensation for signal distortion in double-frequency types of recording is provided in this method of recording information. The signal distortion takes the form of peak shift, baseline shift and extensive variations in dynamic range.

Drawing A indicates the write and read waveforms for conventional phase- modulated recording. Recording is accomplished by varying the write waveform to provide signal transitions 1, 2, and 3 in the center portion of defined bit periods 4, 5, and 6. A positive moving transition is defined as a binary 0 and a negative moving transition is defined as a binary 1.

For correct phasing of the information transitions, auxiliary transitions 7 and 8 are provided between adjacent information transitions of the same type. If the adjacent transitions are unlike it is not necessary to provide an auxiliary transition.

The dynamic range variation of the detected waveform is much greater between adjacent unlike bits of information than between like bits of information. Peak shift also occurs in the detected waveform by movement of the signal peaks for adjacent unlike bits of information into the region where no auxiliary transitions are recorded. Shifting of the high-frequency pulses from common baselines also occurs.

To overcome the problems of distortion in double-frequency types of recording an additional very high-frequency pulse is written between adjacent unlike transitions. Drawing B depicts the wri...