SU1051570A1 - Device for forming signals reproduced from magnetic medium - Google Patents

Abstract

A DEVICE FORMING SIGNALS REPRODUCABLE FROM A MAGNETIC MEDIA containing a driver based on the extreme values of the reproduced signal, an amplifier, a trigger, Schmitt triggers, connected via an OR element to one trigger input, another input is provided by a temper builder using a temper builder. with the first input of the second Schmitt trigger, especially for those. that, in order to increase the fidelity of reproduction by automatically setting the formation thresholds depending on the recording density, a voltage source was added to it, a third Kmitt trigger connected in series, a first low pass filter and a first matching amplifier, output connected to the second input of the first Schmitt trigger, Four Schmitt flip-flops, a second low-pass filter and a second matching amplifier, connected in series with an output connected to the second input of the second Schmitt trigger, n The first inputs of the third and fourth Schmitt triggers are connected respectively to the output and input of the amplifier, the second inputs of the third and fourth Schmitt triggers to the output of the reference voltage source, and the input and output of the amplifier to the first inputs of the second and first Schmitt triggers, respectively.

Description

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The invention relates to instrument making, namely, to devices for reproducing information from magnetic media in magnetic recording equipment, and can be used in a pulse technique where it is necessary to form the extremal values of the input signal in a wide frequency range. Devices are known in which signal generation takes place at points close to the extreme values of the input signal, containing an extremum shaping unit, three Schmitt germs, a key element, a trigger, an amplifier, and an output emitter follower. In such devices, differentiation or delay of input signals occurs. These transformations are performed at points close to the extreme values of signal 1. However, in devices, the accuracy of the recovery (formation) of information depends on the recording density, which causes errors in the subsequent signal demodulation. The closest in technical essence to the present invention is a device for generating signals reproduced from a magnetic carrier, comprising a shaper according to extreme values of a reproduced signal, an inverter, two Schmitt triggers, the outputs of which are connected to the inputs of a logical element OR, and shaper outputs by extremal values The logic element OR is connected to the separate inputs of the trigger. In a known device, a signal is generated by extremal values with control on a given basis. The threshold for the formation of the former by extreme values is usually chosen small - about 0.010, 03 of the size of the reproduced signal, and the threshold for the formation of the threshold, the former, including the Schmitt trigger and the logical element OR, is chosen 0.3-0. , 6 from the value of the reproduced signal or is adjusted manually by changing the potential at the control inputs of Schmitt triggers. Thus, the formation threshold and the known device for generating signals are determined by the trigger formation thresholds. Erov Schmitt and is not changed, i.e., It is not chosen to be optimal when changing the recording density. It is known that the channel noise immunity is maximum if its bandwidth coincides with the spectrum of the signal being transmitted. If the bandwidth significantly exceeds the width of the signal spectrum, the noise level increases. Therefore, at low recording densities (during playback with pauses), when the noise level is large, the threshold value must be chosen at a level of 0.3-0.6 of the value of the reproduced signal, and at high levels at 0.1-0.15, those. the formation threshold of such devices must be adapted with respect to the recording density value 2. However, if the recording channel carries information with different densities (from low to high), then manual adjustment is generally impossible and the formation is performed at some average level, which can lead to loss of information. This device flaw may be eliminated if, depending on the recording density, the formation threshold of Schmitt triggers is automatically changed. The purpose of the invention is to increase the fidelity of reproduction by automatically setting the formation thresholds depending on the recording density,. The goal is set to 1a in that the device containing the shaper by the extreme values of the reproduced signal, the amplifier, the trigger, the first and second 11mitt triggers, the outputs connected via the OR element to one trigger input, the other input of which is connected through the shaper by the extreme values of the reproduced the signal to the first input of the second Schmitt trigger, a voltage source is connected in series, the third Schmitt trigger, the first low-pass filter and the first matching amplifier body, output connected to the second input of the first Schmitt trigger, serially connected fourth Schmitt trigger, second low pass filter and second matching amplifier, output connected to the second input of the second Schmitt trigger. The first inputs of the third and fourth Schmitt triggers are respectively connected to the output and the input of the amplifier, and the second inputs, of the third and fourth triggers of 1 mitt, with the output of the reference voltage source, and the input and output of the amplifier, with the first inputs of the second and first Schmitt triggers accordingly. The drawing shows a functional diagram of the proposed device. The DEVICE contains a shaper 1 by the extreme values of the reproduced signal, an amplifier 2, the first 3 and the second 4 Schmitt triggers, with outputs connected to the inputs of the logical element OR 5, while the outputs of the driver 1 by the extreme values of the logical element OR 5 are connected to separate trigger inputs .6. The device also contains in series the third trigger 1Chmitt 7, the first low-pass filter 8, the first matching amplifier 9, the output connected to the second input of the first Schmitt trigger, sequentially connected the fourth Schmitt trigger 10 second filter 11 of the low frequencies, the second matching amplifier 12, the output is connected to the second input of the second trigger of the Imitt, and the source 13 of the reference voltage, the output of which is connected to the second inputs of the third and fourth Schmitt triggers, while their first inputs are connected to the output and the input of the amplifier, respectively,

The device works as follows.

The reproducible signal from the magnetic carrier enters shaper 1 through extreme values of the reproduced signal, Schmitt triggers 3 and 10 and through amplifier 2 to Schmitt triggers 3 and 7. The reference voltage source 13 to the second inputs of trigger mits 7 and 10 is fed voltage. The generated signal from the output of shaper 1 is received at the first input of flip-flop 6, and at its second input a signal is applied, which is folded on a logical element OR 5 with Schmitt trigger 3 and 4, Pulse signals from Schmitt flip-flops 7 and 10 are fed to filters 8 and 11 low frequencies, where the pulse sequence is converted to a voltage. From the low frequency filter outputs 8 and 11, the matching amplifiers 9 and 12 supply voltage to the second inputs of Schmitt triggers 7 and 10. This voltage determines the formation level of the entire device. The front edge (threshold) of the input signal from Schmitt triggers 3 and 4, and the rear (informational) shaper 1 by extreme values.

In order to restore the reliability of the information pulse signals, it is necessary to reduce the value of the formation threshold of Schmitt triggers 3 and 4 with increasing recording density and, conversely, to increase it with decreasing recording density. In the proposed device, this task is carried out in series with the Schmitt trigger 7, the low-pass filter 8, the matching amplifier 9 for one half-wave the Schmitt trigger 10, the low pass filter 11

frequency 11 and a matching amplifier for the other half wave.

The magnitude of the voltage at the output of the filters, 8 and 11 low frequencies can be represented as

and --U Fnch about 7

where is the fnc voltage at the output of the low pass filter

0 (low pass filter);

UQ is the constant voltage at the output of the low pass filter; And - the amplitude of the pulses

five

111mit trigger; T - pulse duration

at the input of the low-pass filter; T is the period of pulse following.

Magnitude of voltage amplitude

The output of Schmitt triggers 7 and 10 is constant and is determined mainly by the supply voltage, and the magnitude of the pulse duration is the duration of the reproducible response, which,

5, in turn, is determined by the characteristics of the magnetic recording path and is also a constant value.

Consequently, the voltage at the output of the low-pass filters depends on

0 from the repetition period of the reproducible responses and varies directly in proportion to this value. At recording densities with a pulse repetition period equal to the length of the reproducible reproducible responses, at the output of 11mitt triggers 7 and 10, pulses are formed close to the meander, and the constant component at the output of the low-pass filter is small. If the period of the following pulses is longer than the duration of the reproducible response (at a low recording density), then the magnitude of the voltage at the output of the low-pass filter is much longer.

Gain coefficient matching

5 amplifiers 9 and 12 and their parameters are chosen such that the thresholds for the formation of triggers and mitts 3 and 4 are low if the pulse period is less than the duration

0 reproducible responses (at high density). The Schmitt trigger thresholds increase with an increase in the pulse duration, i.e. with decreasing recording density.

five

The device was tested in a static mode, when the recording densities at certain time intervals are constant. In practice, the recording density varies,

0, the threshold of Schmitt triggers 3 and 4 will automatically change. The trigger threshold at the Imitt 7 and 10 triggers is set by the voltage at the output of the 13 .V support voltage.

5, the proposed device, by comparison with the base object (prototype), makes it possible to increase the reproduced information by densities of 5,100 pulses / mm by half of the order.

Claims (1)

A DEVICE FOR FORMING SIGNALS PLAYABLE FROM A MAGNETIC CARRIER, containing a driver for the extreme values of the reproduced signal, an amplifier, a trigger, the first and second Schmitt triggers, outputs connected through an OR element to one trigger input, the other input of which is connected via the driver to the extreme the input of the second Schmitt trigger, characterized in that, in order to increase the fidelity of playback by automatically setting the formation thresholds in depending on the recording density, a reference voltage source is inserted into it, a third Schmitt trigger is connected in series, the first low-pass filter and the first matching amplifier are connected to the second input of the first Schmitt trigger, the fourth Schmitt trigger is connected in series, the second low-pass filter and the second matching amplifier, connected to the second input of the second Schmitt trigger by the output, while the first inputs of the third and fourth Schmitt triggers are connected respectively to the output and input of the force ator, the second inputs of the third and fourth Schmitt Trigger with reference voltage output, and the input and output of the amplifier - the first inputs of first and second Schmitt triggers, respectively.