Circuitry generating clean track crossover signals in disc memories - using PLL to produce estimated value from received pulses and avoid risk of false signal being produced

摘要

A digital disc system (1) moves the head (3) radially across the surface to identify a specific track location. As the disc moves the signal is sinusoidal and a track cross over is indicated by a pulse (TCS1) generated by a shaping circuit. The pulses are fed into a p.l.l. circuit (6) with a phase detector (7), a filter network (8) and a v.c.o. (9). The output (TCS2) is free of distortion and represents the accurate pulses for defining the track cross-over positions. USE - Optical, magnetic-optical or magnetic disc player.