SU699548A1 - Method of reproducing digital magnetic information - Google Patents

Description

one

The invention relates to the field of instrumentation, in particular to methods of reproducing digital information from a magnetic recording medium at an unstable speed of movement of the latter.

A known method of reproducing digital information is based on the formation of pulses in excess of the result of differentiation of the reproduced signal of two levels opposite in sign and gating the result of differentiation at the time of transition of a pulse of 4 p 3 zero.

However, this method does not provide sufficient noise immunity in the presence of high-frequency impulse noise with zero transitions.

The closest in technical essence to the proposed is a method of reproducing a digital magnetic recording, which consists in amplifying reproducible two-pole pulses and gating them 2.

However, if the speed of movement of the magnetic media is uneven, caused, for example, by the difficult operating conditions of the magnetic recording and reproduction mechanisms (vibration, acceleration, temperature change in the recording and reproduction mode, manufacturing faults, etc.) during playback, the pulses are distorted as per the duration and so on the amplitude, which leads to the loss of information, and makes it difficult to separate the value of a binary symbol. In addition, it is often necessary to reproduce the recorded information at a speed many times different from the recording speed, which also leads to a significant change in the duration of the signals during playback and degrades the quality of the information received.

The purpose of the invention is to increase the noise immunity and stability of information reproduction at an unstable speed of movement of the magnetic carrier.

This is achieved by the fact that in the method of playing digital magnetic recording at the moment. First, the half-waves of double-pole pulses set the time interval after which gating pulses of varying duration are formed, and the value of the binary symbol is determined by the phase differences of the signals and gating the second half-wave of a two-pole pulse of opposite polarity.

The formation of a pulse after a predetermined interval of time delay from the start of the half-wave of the double-pole pulses excludes the start of the gating pulse by interference of a short duration. The duration of the strobe pulse is variable and is a function of the half-wave length of the two-pole signal pulse and is always less than the length of the two-pole pulse. This ensures a stable selection of ones and zeros during the reproduction of digital information with an unstable speed of movement of the magnetic carrier.

FIG. Figure 1 shows a block diagram of a device implementing the proposed method, and FIG. 2 - time diagrams of his work.

The reproducing magnetic head 1 is connected to the input of the amplifier-limiter 2, the output of which is connected to the inputs of the inverter 3 and the driver 4 of the gates

from the positive half-wave of the two-pole

a pulse signal, and the output of the inverter 3 is connected to the input of a formate 5 strobes from the negative half-wave of a two-pole pulse of the signal and with one input of the circuit AND 6, the other input of which is connected to the output of the generator of the strobes 4. One input of the circuit AND 7 is connected to the output of the amplifier 2 and the other input is with the output of the shaper 5 of a two-pole pulse. Reproduced by the magnetic head signals 1 (Fig. 2) after amplification and limitation are fed to the input of the gate generator 4, which after a predetermined interval of time delay, measured from the beginning of the positive half-wave of the two-pole pulse, forms a gating pulse 4 with a variable duration, arriving at one input circuits AND 6. At the second input of the circuit AND 6, the inverter 3 receives the negative half-waves of the bipolar signals. In the interval. ; x coincidence of the gating pulses 4 with the inverted negative half waves of the bipolar pulses 2; at the output of the circuit 6; pulses 6 appear, corresponding to a single

values of the recorded signals. And the pulses 7, corresponding to the zeros of the recorded signals, are formed when the AND gates of the gating pulses formed from negative inverted HALF-WAVES of two-pole pulses of the positive half-wave signals 2f received from the output of the limiting amplifier 2 at the inputs of the circuit. Time delay of the gating pulse start selected slightly longer than the duration of the interference pulses, these. exclude the possibility of the gate driver starting from the interference pulse. The irregularity of the speed of movement of the magnetic carrier and its associated variable length of two-pole pulses of signals does not affect the stability of the selection of ones and zeros of digital recording, since the duration of the gating pulses also varies in proportion to the duration of the two-polar pulses (Fig. 2).

The method provides high quality reproduction of a digital magnetic recording with a change in the speed of movement of the magnetic carrier.

Claims (2)

1. USSR Author's Certificate No. 458855, cl. G 11 B 5/02, 1975. 2. USSR author's certificate number 610160, cl. G 11 B 5/02, 1977. “- Phi2.1 / X .. v v / / L. t 2 3  one t i broadcast 2