Digital phase-locked loop filter

Details Digital phase-locked loop filter Digital phase-locked loop filter

1991-12-20

1993-12-21

Kuntz, Curtis

Pulse or digital communications

Spread spectrum

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360 51, 375 81, H03D 324

Patent

active

052727300

ABSTRACT:
A digital filter for a phase-locked loop operates to compare the bit values of the data represented by the incoming pulse stream with patterns in that pulse stream known to produce bit shifting (either early or late). The bit shift caused by physical interaction of bits encoded on computer diskettes or the like always is predictable, in accordance with the pattern of previous bits, the current bit and the next bit. This information is processed by a logic circuit to predict which pulses in the incoming stream of data pulses are shifted. A signal is produced each time a predicted shifted pulse is determined; and this signal is utilized in conjunction with the output of the phase difference counter in the digital phase-locked loop to permit the phase of the controlled oscillator to be adjusted at each unshifted bit in a normal manner, and compensated for adjustment in a modified manner as a result of the prediction of the shifted pulses.

REFERENCES:
patent: 4030045 (1977-06-01), Clark
patent: 4231071 (1980-10-01), Anderson
patent: 5097489 (1992-03-01), Tucci
Western Digital Corp. Storage Management Products Handbook, 1984, pp. 121-123.
Standard Microsystems Corp. 1988 Components Catalog, pp. 514, 519, and 555.
Intel 820 77 A A, pp. 4-86 and 4-87.
National Semiconductor DP8473 Floppy Disk Controller Data Sheet, pp. 5-6 to 5-9.

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