SU1185355A1 - Device for simulating channel for reproducing digital magnetic record - Google Patents

Abstract

A DEVICE FOR SIMULATING THE DROP OF REPRODUCTION OF A DIGITAL MAGNETIC RECORDING, containing a code sequence generator, two response pulse generators, the outputs of which are connected to the corresponding inputs of the differential amplifier, the output of which is connected to the input of the filter, the output of which is the output of the device, which differs from the purpose of improving the accuracy of modeling due to the symmetry of the response of the playback channel to a single magnetic reversal carrier, it additionally contains three counts the trigger, the counting input of the first trigger is connected to the output of the code sequence generator, and the direct and inverse outputs of the first counting trigger are connected to the counting inputs of the second and third counting triggers, respectively, whose outputs are connected respectively to the inputs of the first and second response drivers, each of which consists of a delay line with 2K taps, the input of which is the input of the driver, TO elements EXCLUSIVE OR, To current generators and load resistor, one output to connected to the zero-potential bus, the other output is connected to the outputs of the current generators and is the output of the response pulse generator, the input of the 1st current generator (1, ... 1C) is connected to the output of the -th element EXCLUSIVE OR, whose inputs are connected to 1 --M and 2k - () - M bends of the delay line.

Description

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The invention relates to a technique of digital magnetic recording and can be used to simulate real reproduction signals.

The purpose of the invention is to improve the modeling accuracy by improving the symmetry of the response of the playback channel to a single magnetization reversal of the carrier.

FIG. 1 shows a diagram of the device in FIG. 2 — a diagram of each driver; 3 and 4 are timing diagrams.

The device contains the generator 1 code sequence, the first third counting triggers 2-4, the first and second drivers 5 and 6 response pulses, differential amplifier 7, filter 8. Each of the drivers 5 and 6 includes a delay line 9, generators 10-14 current, elements EXCLUSIVE US 15-19, a load resistor 20. Fig. 2 shows an example of the execution of a driver with K 5, i.e. The circuit contains 5 current generators, 5 elements COMPLETE OR, and the delay line has 10 taps made uniformly. Delay line is matched by

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Consider the work of formers 5 and 6.

A stepped bell-like impulse is formed by summing the currents of the generators 10-14 currents on a common resistor 20. The height of each voltage step being formed and; (FIG. 3) is determined by the product of the current of the i-th current generator by the resistance value of the resistor 20. The switching-on and off-times of the current generator are determined by the i-th EXCLUSIVE OR element, whose inputs are connected to the tap pairs of the delay line 9 located symmetrically relative to its central taps. Due to this, a high degree of symmetry of the generated pulse is ensured.

In the initial state at the input of the imager (FIG. 3), the level is O. The same level is present at all taps of the delay line 9, therefore, at the outputs of all elements EXCLUSIVE OR 15-19, level O is also present and all generators 10-14 of the current are turned off. Therefore, the voltage across the resistor 20 is zero.

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At the output of the item TAKING UP, .OR 1 appears only if the logical levels at its inputs do not match. Therefore, when entering the driver level 1

(FIG. 3), the elements EXCLUSIVE OR 15–19 are sequentially triggered, the generators 10–14 of the current are successively turned on, and an increasing portion of the bell voltage is formed on the output resistor 20 (FIG. 3). Further, starting from the moment when 1 reaches the sixth tap of the delay line 9, as the unit levels at the inputs of the EXCLUSIVE OR 19,18, 17, 16, and 15 elements coincide, the current generators 14, 13, 12, 11 and 10 are turned off. Thus, the shutdown of current generators occurs in the reverse order of their inclusion. In this case, a descending portion of the bell voltage (Fig. 3) is formed on the output-resistor 20 and the symmetry of the bell pulse is maintained with high ACCURACY, since the same currents that were turned on at the first stage of formation are turned off.

Upon reaching the unit level

the last withdrawal line 9 delay

pulse formation ends. When the voltage level at the input to the zero level changes, in a very similar way, the pulse formation is repeated. Further, the pulse at the output of the driver - resistor 20 appears whenever the change in the logic level of the voltage at the input occurs.

Consider the operation of the circuit device using the timing diagram (figure 4).

The output pulses of the generator 1 of the code sequence are fed to the input of the counting flip-flop 2, which, each time a pulse arrives, changes its state to the opposite. Since the inputs of the counting triggers 3 and 4 are connected

to the antiphase outputs of the counting trigger 2, the switching of the trigger 3 occurs along the positive pulse front at the direct output of the trigger, and the switching of the 4lio trigger to the negative front.

Shaper 5 generates a bell impulse on each pulse front of trigger 3, and

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The driver 6 is on each front of the trigger pulse 4. Thus, the driver 5 is triggered by each odd pulse of the generator 1 of the code sequence, and the driver 6 by each of its even pulse.

Using the differential amplifier 7, the bell pulses are subtracted. As a result, at the output of the differential amplifier 7 and the filter 8, which smooths the step voltage, a sequence of alternating polar bell pulses characteristic of the digital magnetic recording channel is formed (Fig. 4).

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The proposed device has flexibility in terms of ease of restructuring the response pulse shape, for which it is necessary to adjust the magnitudes of the currents of the generators 10-14 (Fig. 2) in order to obtain a given pulse shape. To change the pulse width in the device, it is enough to change the delay value of the delay line 9.

Thus, the proposed device is universal.

Since the shape of the pulse response of the playback channel is obtained with very high accuracy, then, with very high accuracy, the shifts of the peaks of adjacent pulses due to their overlap can be measured.

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Claims (1)

DEVICE FOR MODELING THE DROP PLAYBACK OF DIGITAL MAGNETIC RECORDING, containing a code sequence generator, two response pulse shapers, the outputs of which are connected to the corresponding inputs of a differential amplifier, the output of which is connected to the input of the filter, the output of which is the output of the device, characterized in that, in order to increase the accuracy modeling by increasing the symmetry of the response of the playback channel to a single magnetization reversal media, it additionally contains three Fae 1 counting trigger, and the counting input of the first trigger is connected to the output of the code sequence generator, and the direct and inverse outputs of the first counting trigger are connected to the counting inputs of the second and third counting triggers, respectively, whose outputs are connected respectively to the inputs of the first and second response pulse shapers, each of which consists of a delay line with 2K taps, the input of which is the input of the driver, K elements EXCLUSIVE OR, K current generators and load resistor § one, the water of which is connected to the bus of zero potential, the other output is connected to the outputs of the current generators and is the output of the response pulse shaper, the input of the ι-th current generator (ΐ = Ι,.,. Κ) is connected to the output of the ΐ-th element EXCLUSIVE OR, whose inputs connected to the ί —m and 2k- (i + 1) -M taps of the delay line.