SU1615804A1 - Method of analog magnetic recording - Google Patents

Abstract

The invention relates to acoustoelectronics and can be used when recording signals on magnetic carriers. The purpose of the invention is to reduce signal distortion during reproduction. The invention makes it possible to reduce signal distortions caused by its attenuation in time when implementing a recording method based on converting the recorded modulated signal into an acoustic signal in a magnetic medium and affecting the recording magnetic field on it. Distortions are compensated by introducing the scaling of the recorded signal. The scaling is carried out in accordance with the function of the type exp (-KT), where K is selected from the interval 0 * 98K * 984Α, where α is the acoustic attenuation coefficient at the central frequency of the signal. The fulfillment of this selection condition K is aimed at decreasing the effective exponent of the exponent, in accordance with which the signal amplitude changes during reproduction due to the acoustic attenuation of the recorded and read signals. 2 Il.

Description

The invention relates to acoustoelectronics, in particular, devices based on magnetoelastic waves, and can be used in various electronic systems for storing analog signals.

The purpose of the invention is to reduce signal distortion during reproduction.

Figure 1 shows a diagram of the device for implementing the method of analog magnetic recording; 2 shows timing diagrams of recording and reproducing processes.

The method is implemented as follows.

The recorded information signal S (t) (Fig. 2), having the center frequency fo and the duration T, is subjected to amplitude weighting in accordance with the function type exp (-Kt), where the exponent K is chosen from the condition 0 K 4a,

where a is the value of the acoustic attenuation coefficient in a magnetic medium at a frequency of fo. The value of the acoustic attenuation coefficient a in a magnetic medium is previously determined using a well-known technique, for example, by the nature of the decay of the amplitude of a series of re-reflected acoustic pulses in a sample with parallel ends made of this magnetic material.

The scaling of the described signal is also performed by known methods. For example, the signal S (t) is fed to one of the inputs of the multiplier 1, the second input of which receives a signal corresponding to the function exp (-Kt) produced by the generator 2 of special-shaped signals (figure 1). The scaling method can be applied in the case of a chirp signal. those. signal with linear frequency modulation.

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widely used in radioelectronic systems, this method is frequency filtering using a filter having an exponential form of amplitude-frequency characteristic. Such a filter can be made on the basis of a well-developed surfactant technology.

Signal 3 is fed to an electroacoustic transducer 4 (Fig. 1) of a magnetoacoustic device and is converted into an acoustic wave, decaying as it propagates in magnetic medium 5 (Fig. 1). To record a signal on a magnetic medium, it is applied by recording magnetic ; "N (t), which can be formed by applying a pulse 7 to the winding 6 (Figures 1 and 2).

To reproduce the information signal S (t) 8 at an arbitrary point in time, a read pulse Ucr (t) 9 (Fig. 2) is applied to the transducer 4 (Fig. 1). This pulse in the magnetic medium excites the readout acoustic wave, which, interacting with the recorded magnetization distribution, reproduces the recording in the form of an Sounds signal (t) 10, which is removed from the winding 6 (Fig. 1) of the magnetoacoustic device.

The physical essence of the method is as follows.

Reducing signal distortions using the proposed recording method is achieved by introducing signal scaling in accordance with a given function before it is converted into an acoustic wave, which allows partially or completely compensating for distortions arising due to the presence of acoustic attenuation in the magnetic medium. By measuring the signal distortions caused by attenuation, the amplitude ratio at the initial and final portions of the reproduced signal can be taken in the case of a recorded signal with a constant amplitude, i.e. having a rectangular envelope.

When recording without using signal scaling (by a known method), this ratio during playback will be equal to exp (2aT}, because when a recorded acoustic signal propagates duration T in an environment with an acoustic attenuation coefficient (X, the beginning of the signal will have an amplitude of exp ( T) times less than its end, besides, this effect will be amplified by the same amount of time due to attenuation of the read pulse during the reproduction (exp). Thus, the read signal will have a distortion with the amplitude ratio at the initial and final segments equal to exp (2aT).

Signal Scaling Introduction

before it is written by the inverse exponent exp (-Kt), the signal amplitude ratio at the initial exponent becomes equal to exp (2o; T) x X exp (-Kt) exp (2a - K) T. Hence

It follows that the reduction of signal distortion during reproduction is achieved if this value is less than the distortion in the absence of scaling, i.e. when the condition 12a-K I 2a is fulfilled, which is equivalent to the choice of the value of the exponent from the condition 0 К Аа.

It is obvious that the minimum of signal distortions is achieved if exp (2-K) T 1, i.e. when choosing exponent

. In this case, the amplitude of the reproduced signal remains constant throughout its duration. If the value of K is outside the specified inequality, the signal distortion

during playback, increases with respect to distortion in the absence of scaling.

Example. In the experimental verification of the write method of writing, a magnetoacoustic device was used, the magnetic carrier of which is made of a polycrystalline iron-garnet garnet, a piezoelectric transducer based on a lithium niobate plate. The central frequency of the devices is 10 MHz. The winding device had 15 turns.

To test the efficiency of the recording method, an input signal of a frequency of 10 MHz with a duration T 50 µs was used.

as a simple radio pulse. The value of the acoustic attenuation coefficient was previously determined by the usual pulse method and was at a frequency of 10 MHz and 0.1 dB / MCS.

The signal was scaled using an analog multiplier, made on the basis of a balanced modulator of the type K 174 PS 1. A recording was fed to one multiplier stream.

signal, on the other - a signal generated by an exponential waveform generator. The generator was made on the basis of a standard radio technique - the use of the exposure-sensitive nature of the discharge capacity. The exponent of the exponent was regulated over a wide range by varying the time constant τ of the RC generator, where R is the value of the discharge resistance. The signal was read and recorded using a simple radio pulse of 0.5 μs duration with a center frequency of 10 MHz,

It was found that in the absence of scaling (K 0) of the signal, the reproduced signal is distorted and has an exponentially falling envelope with an amplitude ratio at the ends of the pulse equal to 10 dB. With the introduction of amplitude weighting (K 0), the distortion of the reproduced signal decreases and reaches a minimum (the signal has a rectangular envelope) when the exponent K of 0.2 dB / MCS 2a is shown. With a further increase of K, the distortion also increases

TO

0, Aa reach the same magnitude

us as p. no amplitude weighting. With a further increase in K, the distortion increases.

Thus, the reduction of signal distortion during reproduction is achieved when the value of K lies within

0 k o .4

dB

ISS

VIA 0 K 4a.

i.e. at performance of conditions

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The use of the method allows the expansion of the capabilities of an analog magnetic recording and is used to record and store relatively high-frequency and long-lasting signals used in various radio engineering systems and computing.

Claims (1)

Analog Magnetic Recording Method Including Converting a Writable Modulated Signal into an Acoustic Signal in a Magnetic Environment and Influencing a Magnetic Medium with a Recording Magnetic Field that is Different with the Purpose of Reducing Distortion of a Signal During Playback produce its scaling in accordance with the function of the form exp (-Kt), where the exponent K is chosen from the condition 0 К 4а, where a is the value of the coefficient of the acoustic attenuation in a magnetic medium at the center frequency of the recorded modulated signal Uc4 (t} S (t) 0 / exp (-Kt) (t} .Sg, ... (t} to “About