SU1607010A1 - Device for compensation for time distortions in magnetic recording apparatus - Google Patents

Abstract

The invention relates to the accumulation of information. The aim of the invention is to expand the frequency range and improve the accuracy of compensating temporal distortion (VI). The device contains a magnetic recording-reproduction unit (MSW) with reference and information signal channels, the output of which is connected in series with an analog-digital converter (ADC) 4, memory register 7, a digital-analog converter (DAC) 13 and an integrator 14, whose output is a device output, as well as a time delay unit 11 and a clock signal generator 2. The device includes clock synchronization of gating pulses of gates of ADC gates and delayed read pulses of digital samples from the memory register from generator 2, the output of which is connected to the gate gates of the ADC through the frequency divider 3 connected in series, the channel of the reference signal of block 1, the first limiting amplifier 5 the shaper of 6 gates of the ADC gating, and with the read input of the register 7 of the memory, through the second limiting amplifier 8 connected in series and the shaper of 9 pulses. The device also comprises an AND 10 logic element, the second input of which is connected to the output of the first shaper 6 of pulses through a time delay unit 11 connected in series and the shaper of 12 enable pulses. 2 Il.

Description

ten

The invention relates to the accumulation of information, namely, magnetic recording-reproduction devices (MSVs) with compensation for the time and the content of the reproduced signal caused by fluctuations in the velocity (CS) of the recording medium.

The purpose of the invention is to expand the frequency range and increase the accuracy of the compensation of temporal distortions.

1 shows a block diagram of the device; in fig. 2- temporary data frames, which remove the formation of 5 read pulses from the memory register. Figure 2 marked: a - a sequence of pulses from the output of the second imager them: pulses and one input element And; 20

b - sequence of gating pulses of the ADC from the output of the first pulse former (dashed line: conditional parasitic time: | module Di for the case when the 25 mismatch between pulses of diagrams a and b c) p - 0; : c is a sequence of blocks delayed by & (-2/4 pulses of the temporal gate of the resolution and at the second input of the element AND (the dotted line shows the case of coincidence in time of the pulses of diagrams a, b, in only for the beginning of the first clock cycle T;);

g - sequence of read pulses of digital samples from the memory register and at the output of the AND element (the dotted line shows the case of coincidence of the pulses of the previous diagrams for the start of the first cycle)

Diagrams d, e, x show the case when the time with p is 3/4 T; .

The device contains a recording-reproducing unit 1 with buses of reference and information signals channels, a synchronizing signal generator 2, a frequency divider 3 and an analog-to-digital converter (ADC) 4, the signal input of which is connected to the channel of the information signal channel strobe the input is connected to the output of the generator 2 via the serially connected divider 3 frequency :, the channel of the reference signal of block 1 (additional bus), the first amplifier-limiter 5 and the driver 6 pulses, and the output of the ADC 4 is connected to the signal input ohm of the register 7. memory, the read input of which is connected to the output of the generator30

35

40

50

55

0

50

five

thirty

35

pa 2 through connected in series the second limiting amplifier 8 and shaper 9 pulses and element. And 10, another input of which is connected to the output of the first shaper 6 through a time delay block 11 and a shaper of resolution pulses connected in series, a digital-to-analog converter (DAC) 13 and an integrator 14 are output to the output of memory register 7 and devices.

The device works as follows.

The recording of the reproduction of the information and reference signals is carried out simultaneously on different tracks of the magnetic tape. A recorded harmonic reference signal is formed from a generator signal by a divider 3 with a division factor of, for example, two. The reproduced information signal is fed to the signal input of the A / D converter 4, to the gate input of which pulses are generated, which are generated from the reproduced harmonic reference signal by the first amplifier-limiter 5 and by the former 6. The frequency of these pulses is variable due to CS recording medium, and their average frequency is at least twice the upper frequency of the information signal O.

CtpO

 2nd in

soot

with the counting theorem. I

Moreover, a possible increase in the average frequency of the ADC gating pulses and pulses from the memory register in the known device does not lead to an increase in the accuracy of the compensation of the VI.

To confirm these findings, we consider the features of compensation for temporal, frequency, and phase distortions in the proposed and well-known devices, combining them under the more generic name of parasitic angular modulation (PIP) for recording the harmonic information signal and the harmonic law of the CS during recording (GLC) and playback (CWS). Using the replacement of the argument, the reproduced information "signal", the distorted PIP, can be represented as follows:

   S2.

U (t), (t) .Ii (/ 5n3b

(/ 3nB) cos () t, (1) where Qj, is the signal frequency;

pz pv

IR, RC - interference frequency and RACS and CWS coefficients; tn (t) /i.tn3(t)++ & t j, g (t) is the parasitic temporal displacement at ASR and CWS;

At (t) ft. ,, sinS2n t, iitng (t). t ngsin gt;

Rv

fr- - PB amplitude

yes.time offset;

N fz f. pvP

H - -Q; - gth; 7

iOne - PIP indices;

ISOP pv parasitic frequency deviation;

 ) Bessel functions of the first kind, on the order of r, p.

The reproduced reference pulse signal can be represented as a sequence of delta functions: NM

I / t) 2% - kT-it,. (KT) |, (2)

de, 1,2, ..., N-1 - numbers of clock pulses or amplitude samples of the information signal;

T is the period following the sync pulses; - duration

reproduced signal.

It can be seen from (1) and (2) that the parasitic belt displacement caused by the CS line on the MV process is converted into a PMP with indices f.

Taking amplitude samples in an anaogamic sampler and remembering ADC (before converting them to a digital code) will be provided as

M -1 U (t) U (t) l (t) U (t) (iiftkcO

- kT-ut, (t) i. (3) The spectrum or direct conversion of the urie of this product

07010Tf6

S (CO) Ju (t) I / t

Io

can be obtained by using filter

with property delta function 00

Jf (x) (x-x) (xp; M-1 p S / W) u kT-ut (kT) X

 O / jflcoCkT-UKoCkT) -,

By presenting the reproduced information signal (1) in the exponential form cosa) t 1/2 (), after 15 obvious transformations, we obtain the discrete Fourier transform (DFT) of the signal U (t) in the time domain:

20S, (03) i.

  i L

 gi () (tmn35i n3 TH Q; nQn kT

, p-i (cO.QcU

 .) (- nb r ,,, 9; nQ, kT)

;(five)

. From (5), the DFT is easy to crawl in the frequency domain, i.e. expressed through frequency samples, replacing ° 03 nGO ,, G}, 2aWN 2; r / NT 2 / Tc,

where CO 1 S2 (.. g- the sampling frequency is necessary according to the sample theorem; S2cB is the upper frequency

information signal spectrum; , ± 1, ± 2, .. ,, ± (N-0/2;

40S (nQ,) I re- /.)kT.

 ei (nO,) ACun, -i (nco.4S) xr

bx

, e () (kT)

5 DG to reduce recording, the time offset ut (kT) is written in general. From (5) and (6), it follows that in the spectrum of the broadband reproduced and sampled signal for 0 discrete frequencies PSO, C ,, nCO, the second factors in both terms under the sum sign are equal to one, which means full compensation of the PSM in the sampled signal for all The 5 components of its spectrum, nOj S. In this case, the maxima of the spectral density are formed at frequencies (13 n CO, T S2, and (6) takes the form of free / temporal distortions.

s.W,) - iXt-

  li O m {poe, + C2e

+ e -. (7)

From (5) and (6) it also follows that:: in the absence of one of the reproduced signals QC.O or nQ, 0, the other signal contains a PIP, as in (1) and (2), i.e. PIP compensation occurs only as a result of multiplying the reproduced signals for all the frequencies of the PSR, including the upper one, which in the proposed device is twice as large as in the known, From expressions (5), (6) and. (7) it also follows that in order to receive the reproduced signal and its spectrum, free from the PUM, it is necessary to go from a variable period of gating pulses in (4) to a constant reading period of digital samples from the memory register in (7).

One & To in a known device when

at. the prototype with the duration of the signal with:

0.01

2 2 0.05 0.005

0.1

ten

0.001

0.2

0.0005

0.01

ten

0.2

2 0.2

and the above example shows that with longer signals, typical for systems with complex signals (signals with a large base), unacceptable time-scale distortions occur, for example, in Doppler systems, leading to errors in measuring signal parameters.

Only with a small detuning of both generators, 001% is obtained .-, an acceptable result, when the distortions of the time scale can be neglected,

In the sampling-storage device,

the frequency deviation of the impulse-25 generator input 1tz to the ADC 4, occurs

a reading of f cs from the average frequency of the reference signal f causes a temporary error

,, - - -; ij; , (eight)

which accumulates over time and leads to a change in the time scale or signal duration by the LT value. This is because the clock synchronization of the reproduced reference signal pulses, strobe the ADC and the read pulse generator from the memory register, is performed once by the first played sync pulse delayed by the multivibrator, overturns the trigger and starts the read pulse generator, which then operates in self-oscillating mode. The accumulation of time-scale distortions also leads to a coincidence in time of the gates of the ADC gates and read pulses, which can occur after m pulses and 1 time during the signal duration

m

UT

(9)

NT N

tt t So ,. for example, for the upper frequency of the signal spectrum of 10 kHz at the frequency of the reference signal of kHz, the ISS, for different frequency deviations of both generators D (%). have

five

0

0

five

0

quantization of the information reproduced signal in time and, as shown above, compensation of the SMP according to expressions (3) - (7) for all components of the spectrum of the information signal. The compensation of PIP can additionally be due to the fact that the parasitic temporal displacement of the ADC's strobing pulses and the corresponding current values of the information signal is the same, therefore, the corresponding amplitude samples have the same magnitude as the samples without the parasitic time offset. Then, the obtained amplitude samples, free from temporal distortions, are alternately converted by DAC 4 to n-bit digital words, which are fed to the signal input of memory register 7, where they are stored for a short time and read from it by read pulses with a constant repetition rate equal to the average frequency of gates of the ADC Gating pulses, and detainees relative to them by

S tc,

five

- T - O T i

 - -stro - t These read pulses form coziness

from the harmonic signal of generator 2 using two different channels. With the help of the second amplifier-limiter 8 and the former 9, pulses are formed with a constant frequency of -2C cTDC- 5

04 which are served on

Research institutes of the frequency range and increasing the accuracy of compensation, a frequency divider connected between one output of the synchronizing signal generator and the additional bus of the reference signal channel and the first connected amplifying amplifier and pulse shaper connected between the reference signal bus and the additional gate input of the analog signal Digital TransformationManual N.Makarenko - Editor L.Veselovska Tehred M.Hodanich Proofreader A.Obruchar

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VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab.

Production

.-Publishing Combine Patent, Uzhgorod, st. Gagarin, 101

the bodies are connected in series the second limiting amplifier, the second pulse shaper and the AND element connected between another output of the clock signal generator and the matching memory register input, and the resolution pulse shaper of which input is connected through the time delay unit to the output of the first shaper driver and the output is to another input element I.

FIG. 2

one input element And 10 (timing diagram a in figure 2). At the other input of the element I, there are pulses of a temporary gate (resolution), which are formed from the gating pulses of the A / D converter 4 from the output of the former 6 (diagram b) delayed by time 5. time delay block 11 and ods 1i1607010

ten

ADC and read from register

memory from r, 0.5 T ,, to 5/8 T .. Such an initial mismatch will occur, for example, as a result - different paths of these pulses. However, in this device, as can be seen from the time diagrams, you can always

po.a: „: g .. :: (.,„

ME R) T VT4 Tr T -Lmr xjr 1 -yy .t / -

| ma c). The dotted line shows the conditionally parasitic temporal displacement of pulses caused by the recording medium COP. Earlier, it was noted that the strobe pulses of the ADC are also formed from; the clock signal of the generator 2 is connected by 1 sequential divider 3, the reference signal channel, the first amplifier-limiter 5 and the driver 6 - | LEM pulse frequency Q. by two, the pulses delayed relative to the pulses of the ADC gating are formed

. 4JJ1D1-D1 is distinguished by reproducibility; 1 gy

    - "- with" ™ ".

In the known device, as was noted when considering expressions (b) and (9), such a damping switch does not exclude temporal and amplitude distortions resulting from the drift of the frequency of individual gating pulse generators and reading. The digital samples of the reproduced signal, read from block 7, are fed to block 13 of the D / A converter, where they are transformed into a sequence of pulses modulated in amplitude. By means of the integrator, 14 of this sequence is reproduced by the frequency reproduced following

2 MW QcTpo

equal to the average frequency of the ADC gating pulses. The magnitude of the time delay L: block 11 and the duration of the pulses Cp of the temporary gate of block 12 are determined from the conditions:

 : 1 0l ACG / -: s;

temporal distortion. Moreover, the departure of the frequency of the generator 2 within acceptable limits does not violate the frequency range and the accuracy of compensation of the VI.

where t

,,

 T,

(10) (11)

 , 5 ISS duration

B -sn

sample pulses, read and convert for average speed ADC.

If the first condition (10) fails and the pulses of diagrams a, b and d coincide (dashed line in the first cycle of the diagrams), i.e. if the mismatch between them is tp.- O, the result of reading from the memory register will be undefined. However, in this device, this uncertainty is eliminated, for example, during the initial setup of the equipment by introducing a time delay of GLT; / 2. The following three time diagrams (d, e, g) represent the case when the magnitude of the time error T,. At the same time, the value of the time delay between strobe pulses30 Various choices are possible for the operating frequencies of generator 2 and the frequencies of the remaining blocks. So, for example, for an audio frequency range with an upper frequency of kHz, you can take a generator frequency of 2 40 kHz; the frequency of the reference signal f.2С kHz; gating and reading pulse frequency kHz; pulse frequency of the fa driver, 80 kHz, Q with the division factor of block 3

 and multiplication factors of formers 6 and 9 Ki.2. about

Claims (1)

Invention Formula 45 50 55 A device for compensating temporal distortions in a magnetic tape recorder, containing buses of the reference and information signals of the channels of the recording-reproducing unit, connected in series to an analog-to-digital converter, a memory register, a digital-to-analog converter and an integrator- output which is the output of the device, as well as the generator of the synchronizing signal and the block of the time delay, that is - with the aim of expanding the 1607010 ten ADC and read from register memory from r, 0.5 T ,, to 5/8 T .. Such an initial mismatch, mzzhrt- to occur, for example, as a result - various ways of these pulses. However, in this device, as can be seen from the time diagrams, you can always writing is distinguished by respiration; 1 gy - "- with" ™ ". In the known device, as was noted when considering expressions (b) and (9), such a damping switch does not exclude temporal and amplitude distortions resulting from the drift of the frequency of individual gating pulse generators and reading. The digital samples of the reproduced signal, read from block 7, are fed to block 13 of the D / A converter, where they are transformed into a sequence of pulses modulated in amplitude. By means of the integrator 14 from this sequence, the reproduced in - - - - - with „™" is extracted. temporal distortion. Moreover, the departure of the frequency of the generator 2 within acceptable limits does not violate the frequency range and the accuracy of compensation of the VI. 0 Various choices are possible for the operating frequencies of the generator 2 and the frequencies of the remaining blocks. For example, for the audio frequency range with an upper frequency of kHz, the frequency of the generator can be 2 40 kHz; the frequency of the reference signal f.2С kHz; gating and reading pulse frequency kHz; pulse frequency of the fa driver, 80 kHz, Q with the division factor of block 3  and multiplication factors of formers 6 and 9 Ki.2. about Invention Formula A device for compensating temporal distortions in a magnetic tape recorder, containing buses of the reference and information signals of the channels of the recording-reproducing unit, connected in series to an analog-to-digital converter, a memory register, a digital-to-analog converter and an integrator- output which is the output of the device, as well as the generator of the synchronizing signal and the block of the time delay, that is, with the aim of expanding