SU1068987A1 - Method of reproducing magnetic record of phase-modulated signals - Google Patents

Abstract

A METHOD FOR REPRODUCTION OF THE MAGNET RECORDING OF PHASE) DUALED SIGNALS, at which the threshold formation of the reproduction signal is carried out and this signal is used for the selection of the clock frequency, characterized in that in order to increase the recording density; Before the threshold shaping, the carrier is suppressed in the playback input signal to a level less than the shaping threshold, and Phase modulation of the input playback signal or its derivative signal of the threshold generator is performed for the selection of the clock frequency. received signal, i which is amplified and limited.

Description

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6 The invention relates to instrumentation, more specifically to a technique of digital magnetic recording. A known method of reproducing a magnetic recording of a phase-modulated signal involves differentiating the reproduction signal, amplifying-limiting it, and extracting the source code and clock pulses using the received signal that repeats the original recording signal LI in form. The disadvantage of this method is the difficulty of restoring the original reproduction signal with accuracy sufficient to reliably extract the code and clock pulses, which limits the allowable recording density and reliability in Reproducing the information. Closest to the present invention, there is a method for reproducing a phase-modulated signal-ala, providing for the threshold generation of a reproduction signal and extracting an information code and a clock frequency using the received signal, which repeats the original recording signal t21 in shape. The disadvantage of this method is that the presence of phase and amplitude distortions caused by intersymbol interplay, as well as by specific disturbances of the recording-replay track (spurious amplitude and frequency modulation), makes it difficult to restore the original LOR of the recording signal and, as a result, limits the allowable recording density. The purpose of the invention is to increase the recording capacity. The goal is achieved according to the method of reproducing a magnetic recording of phase-modulated signals, at which the threshold formation of the reproduction signal is used and this signal is used to extract the clock frequency, before the threshold formation, the carrier in the reproduction signal is suppressed to a level less than the threshold of formation, and for the selection of the clock frequency, the phase modulation of the input signal is reproduced or its derivative signal of the threshold generator, ate dissolved fundamental wave signa la obtained, which is then amplified and restricts the oi-. As a result of suppression of the carrier in the reproduction signal, a signal is received that repeats in the Form a differential reproduction signal when recording with a non-return to zero method / if absolute phase modulation was used in the recording, or modified without a return to zero in recording. phase modulation. Therefore, in. the result of the threshold Loriation, provided that the carrier is suppressed) to a level less than the formation threshold, the floor: a non-phase-modulated signal repeating in shape the original recording signal, as in a known device, but the input information signal itself. Since in the proposed device there is no need to restore the original recording waveform, phase distortions arising due to intersymbol interference and variations in carrier speed do not affect the fidelity of reproduction. Amplitude distortion is even useful by reducing the low-pass filter requirements. As a result, the possibility of recording density and reliability of reproduction of information appears. According to the proposed method, the clock frequency is obtained by phase modulation of the reproduction signal or its derivative by the generated code, by extracting the main harmonic of the received signal with post-amplification-limiting. Figure 1 shows the scheme of the device that implements the proposed method; 2 shows diagrams for the operation of the device. The playback device (Fig. 1) contains a reproducing magnetic head 1, a preamplifier 2, a low-pass filter 3, a threshold element 4 — a Schmidt trigger, an information output bus 5 connected in series, and a clock frequency selection channel, which also a differentiator 6 connected in series, a phase modulator 7, a band-pass filter 8, a limiter amplifier 9 and an output bus 10 of the clock frequency. The input of the differentiator b is connected to ... the output of the preamplifier 2, and the second input of the phase modulator 7 is connected to the output of the Schmidt trigger 4. Let information be recorded, for example, by an absolute phase modulation method (FIG. 2, AB), where the input information signals are shown, the clock frequency and the write current. The playback method is carried out as follows. The reproduction signal (FIG. 2, D) from the reproducing head 1 is amplified by the preamplifier 2 and fed to the low pass filter 3 and then to the Schmidt trigger 4. Through the low pass filter 3, the reproduction signal suppresses the carrier to a level less than the threshold for the formation of the Schmidt trigger 4 (figure 2, D, the dashed line shows the threshold for the formation). Then the trigger of the Himidt 4 form a code (figure 2, E) and serves it on the output bus 5 information. To obtain a clock frequency, the amplified playback signal from the output of preamplifier 2 (FIG. 2, D) is differentiated by differentiator 6. The differentiated signal (FIG. 2, G) is subjected to phase modulation by means of a phase modulator 7, to the second input of which the formed the code (FIG. 2, E) from the output of the Schmidt trigger 4. From the signal obtained as a result of the phase modulation (FIG. 2, I), the clock frequency, i.e. the main harmonic of the received signal (Fig. 2, K), which is formed by the limiting amplifier 9. The received signal (Fig. 2, L) is fed to the output bus 10. Plots M, H, and P (Fig. 2) explain the operation devices in the case of a received clock frequency by phase modulation of the reproduction signal. This excludes the operation of the diLferen signal squaring. The remaining operations are performed as described above. A differentiator b must be eliminated from the playback device (Fig.1), and the phase modulator 7 is given a signal from the output of the preamplifier 2. The signal from the output of the phase modulator 7 is shown in the picture M (Fig.2 ). Plots H and P (Fig. 2) show the signals at the outputs of the band-pass filter 8 and the amplifier limiter 9. It is advisable to select the cut-off frequency of the low-pass filter 3 equal to half the carrier frequency. In this case, the minimum attenuation at the frequency in / 2, which transfers the main energy of the signal applied to the threshold driver, and the maximum carrier suppression, is ensured. The slope of the amplitude-frequency characteristic should be at least 10 dB / octave, which ensures the suppression of the carrier below the formation threshold equal to 1/3 of the amplitude of the detected signal. Applying the filters of the second and third order, it is possible to provide a slope of 1218 dB / octave of the amplitude-frequency characteristic. It is necessary to take into account that the frequency response of the recording-reproduction path has a block in the upper frequencies, therefore the total suppression by the carrier recording-reproduction path and the low-pass filter is usually more than 20 dB. The formation threshold in the pulse detection task must choose between half the pulse amplitude and the level of interference. In practice, the formation threshold is usually 1/3 of the amplitude of the detected pulse. It follows that the carrier should be suppressed by more than 10 dB, and, the more the carrier is suppressed, the better. reliable clock release). In practice, the band-pass filter should have a quality factor from 2 to 10. If the recording-reproduction path introduces amplitude distortion, the requirements for the slope of the amplitude-frequency characteristic of the low-pass filter are reduced. Since the recording by the proposed method is not affected by phase distortion, and amplitude distortion is even useful, the elements of amplitude and phase correction are absent, which simplifies the playback device. More important for the proposed method is the presence of a delay introduced by the low-pass filter and an additional delay due to the formation with a threshold other than zero. At relatively low carrier frequencies, this delay has virtually no effect on the accuracy of information allocation and so on. Frequency frequency However, with increasing carrier frequency, this shift must be compensated by delaying the signal applied to the input of the phase modulator. For this purpose, we can recommend a low pass filter with a cutoff frequency greater than the carrier frequency. The basic object for comparison with the proposed cassette storage device KRRVOO can be selected, in which the well-known reproduction method is implemented. In the KRP800 device, the recording density is 32 bit / mm, and the playback accuracy is 10.bit / failure. The proposed device realizing the proposed recording method is provided with the reproduction of information recorded by the phase duplication method with a square wave.

with a recording density of 350 bits / mm and a confidence of 10 bits / failure 1

The quality of the recording-reproduction path, defined as the product of the recording density and the decimal logarithm of accessibility C 31, is 224 for the base object, and 1750 for the proposed method. From the quality of the base object, one can estimate the accuracy of the reproduction in BAO 1 O 1 1 O About 1 11 1 1 about

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With a recording object with a recording density of 350 bits / mm, it is only 10 bits / failure.

Thus, when using the proposed method, a techno-economic effect is provided, which means that the recording density can be increased several times as compared with the base object without impairing the reliability.

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Claims (1)

METHOD FOR PLAYING MAGNETIC RECORDING OF PHASE-MODULATED SIGNALS, in which threshold amplification of the playback signal is performed and this signal is used to isolate the clock frequency, characterized in that, in order to increase the recording density; before the threshold formation. suppresses the carrier in the input reproduction signal to a level lower than the formation threshold, and to isolate the clock frequency, produce a phase modulation of the input reproduction signal or its derivative by the signal of the threshold driver, select the main harmonic of the received signal, which is then amplified and limit. B 1.068987. Figure 1>