JPS58122604A - Magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To obtain a sound signal without distortion, by taking a pilot signal as a carrier wave, amplitude-modulating signals with a control signal, recording and reproducing the signals on/from a single track, and eliminating the frequency modulation of sound signals by means of the frequency fluctuation of the pilot signal. CONSTITUTION:A modulated wave of amplitude-modulation reproduced from a control track on a magnetic tape is demodulated at a demodulator 32 and the control signal is outputted from an output terminal 35. On the other hand, the modulated wave is formed into an impulsive pilot signal, about 480Hz in frequency via a switch SW, converted into a pulse, about 80Hz in frequency at a frequency-divider 38 and applied to a PLL40. The frequency fluctuation (wow and flutter) is detected at the PLL40, the result is applied to a VCO41 and a clock pulse is generated. The clock pulse varies a delay time of BBDs 52, 53 to eliminate the fluctuation from the sound signals from terminals 46 and 47.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention records a control track in a magnetic recording/reproducing device, records a pilot signal modulated with a control signal, a signal from which high frequency components have been removed, and uses the reproduced modulated wave signal. By separating the control signal and removing the wow and flutter components of the audio signal using the frequency fluctuation of this pilot signal, the control signal and the pilot signal can be recorded and played back on one track, and the reproduced audio It is an object of the present invention to provide a magnetic recording and reproducing device that can remove wow and flutter components from a signal.

In conventional video table recorders, during recording, the control signal of the frequency path 30H2 is recorded on a different track from the audio signal, and during playback, the phase of the reproduced control signal is compared with the reference signal of the frequency path 3QHz from the oscillator. The capstan motor's rotation is controlled by detecting the rotational speed using the frequency generated by the FG installed in the flywheel of the capstan, thereby preventing wow and flutter from being included in the reproduced audio signal. Ta. However, this rotational control of the capstan motor alone does not sufficiently remove wow and fluff components, and there is a drawback that the sound quality deteriorates due to wow and flutter contained in the reproduced audio signal.

The present invention eliminates the above-mentioned defects, and each embodiment thereof will be explained below with reference to the drawings.

Figure 1 shows a block system diagram of the first embodiment of the recording system of the lid according to the present invention. In the figure, reference numeral 1 denotes an input terminal into which a video signal is input, and this video signal is supplied to a synchronization signal separation circuit 2. The horizontal synchronization signal and vertical synchronization signal extracted from the video signal by the synchronization signal separation circuit 2 are supplied to the vertical synchronization signal separation circuit 3, where the frequency approximately 6 as shown in FIG.
The 0Hz vertical synchronization signal is separated and supplied to the branching unit 4. min) i! The D unit 4 divides this vertical synchronizing signal by 172 and converts it into a pulse with a frequency of approximately 30 Hz as shown in Fig.
) 5, 6 and the phase comparator T. The phase comparator 7 is a voltage controlled oscillator (hereinafter referred to as 1"VCOJ).

A phase-locked loop (hereinafter referred to as “P
vaoB whose oscillation frequency is divided by 1/16384 by the frequency divider 9.
6. By comparing the phase of the output signal with a pulse having a frequency of approximately 30 Hz. A pulse having a frequency of approximately 491 KHz, which is synchronized with the pulse having a frequency of approximately 30 H2 from the vcog, is increased and supplied to the counting input terminal of the counter 10. Furthermore, the monomulti 5 is triggered by the rising edge of the pulse shown in FIG. 2 (Bl) and generates the pulse shown in FIG. The rising edge of the pulse of Bl generates a pulse-like control signal shown in Figure 2 (Di) and supplies it to the low-pass filter 11.The low-pass filter 11 removes unnecessary high-frequency components from the control signal. After removal, it is supplied to the modulator 12.

The counter 10 starts counting the pulses supplied from vaoB when the pulse shown in FIG. 2 (C1) of the monomulti 5 falls, and divides this pulse by 1/1024 to (Generates a pulse (pilot signal) with a frequency of approximately 480Hz shown in El and passes it through the low-pass filter 13.
supply to. In this way, by adjusting the time constant of the monomulti 5 and reducing the pulse width of the pulse shown in Fig. 2 to), the phase of the pulse shown in Fig. 2 (g) can be advanced or delayed. can do. The pulse shown in FIG. 2 (El) has its high frequency components removed by a low-pass filter 12, becomes a sine wave with a frequency of approximately 480 Hz, and is supplied to a highly accurate f modulator 12 with very good linearity. Modulator 12 This sine wave with a frequency of about 480H2 is AM-modulated by the control signal from the low-pass filter 1t, and the amplitude becomes large during the low-level period of the monomulti 6-shi pulse, as shown in Figure 2 (fF). A modulated wave having a frequency of about 480 Hz whose amplitude gradually decreases during the level period is generated and supplied to the amplifier 14. By changing the time constant of the monomulti 5, the phase of the modulated wave shown in FIG. Figure 2 shows the time constant (by changing the pulse width of Di, the amplitude gradually changes from a small S width to a large amplitude and ends the change/the phase of #b can be changed, and the modulator 1
2, the amplitude C can be set to an appropriate level.

This modulated wave is amplified in the amplifier 14, then superimposed on the bias signal from the bias generator 16 in the mixer 15, and is supplied to the magnetic field IT and recorded on the control track in the longitudinal direction of the magnetic tape 18. . Along with this, an input terminal 19a.

191) The incoming audio signals of the first channel and the second channel are amplified by amplifiers 2Qa and 201), respectively, and then superimposed on the bias signal of the bias oscillator 16 and magnetically generated by mixers H& and 211). head 22
a and 22b, and are recorded on two audio signal tracks different from the control track in the longitudinal direction of the magnetic tape 18, respectively.

In the W modulator 12, which has extremely good linearity, the pilot signal which is a sine wave with a frequency of about 480H2 is used as a carrier wave, and the control signal from which high frequency components have been removed is used as a smart modulation signal to perform amplitude variation. Even when fhill is performed without removing high frequency components from the control signal, the frequency band from the lower sideband to the upper expansion band of the fhil wave becomes extremely narrow.

#E3 Figure is 1 of the reproducing system of the magnetic recording/reproducing device according to the present invention.
A block system diagram of an embodiment is shown. 30 magnetic tape 18
This is the input terminal into which a modulated wave as shown in Figure 2) is input, and this modulated wave is input to the automatic gain control (hereinafter referred to as "AGOJ") amplifier 3.
1, the signal is amplified while removing long-cycle level fluctuations, and is supplied to the receiver lJ[32 and limiter 33. The demodulator 32 performs full-wave rectification of this modulated wave as shown in FIG.
A waveform shown in A1 is obtained, and this is smoothed to obtain a waveform shown in FIG. 4 (B1), which is supplied to the zero-cross detector 34.

The zero cross detector 34 detects the waveform v shown in FIG. 4 (Bl).
Figure 4.10 compared to the ISA threshold level.
Detects the control signal shown in 1 and outputs it to output terminal 3.
Output from 5. Here, there is a phase shift f between the detection point e of the control signal and the amplitude change point a in Figure 4 (A), which is the point where the control signal was generated during recording, but this phase shift is Since it is determined by the smoothing time constant of the detector 32 and the threshold level of the zero-cross detector 34 and is a constant value, highly accurate tracking can be performed as in the conventional case.

Further, the modulated wave from the AGO amplifier 31 is made constant in amplitude by the IJ transmitter 3S, and then sent to the zero cross detector 36.
, where the noi level s o
It is a pulse-like control signal that becomes low level under V pt and is sent to terminal 8'Wa of switch SW and PLL.
37. The PLI, 37, is set to follow the frequency fluctuation of the supplied pulse-like pilot signal, and even if the pilot signal drops out, it continues to oscillate within the variable range of the built-in VaO, and the pulse that dropped out continues. It generates and outputs it to the terminal BWb of the switch sW. The switch SW is a switch that connects the terminals 8Wa and 8Wc when there is no dropout of the pilot signal, and connects the terminals swb and 8Wc when there is a dropout, and connects the terminals swb and 8Wc when there is a dropout of the pilot signal. The pilot HI was sent to the branch station 38 and the packet brigade device (
39 (hereinafter referred to as "BBDJ").

The divider 3s divides the above pulse by 176 to give a frequency of approximately 80.
It is supplied to the PLL 40 as a Hz pulse. This is a pilot signal with a frequency of approximately 480 Hz, and since it is difficult to detect frequency fluctuations at low frequencies, it is divided into stations and the frequency is approximately 80 Hz.
It is set to 0Hz. A pulse with a frequency of approximately 80Hz fiP
A frequency fluctuation (wow/flutter) of approximately IH2 or more is detected in LLJo, and is extracted as a change in stain pressure by the loop filter built in the PLL 40 and supplied to the VCO 41, which changes its oscillation frequency according to the wow/flutter. let This signal generated by voo4t is supplied to the clock drive circuit 42.48, where BB
The waveform is shaped into a clock pulse for D. The clock drive circuits 42 and 43 have the same characteristics and can only drive two BBDs with one clock drive circuit, so two clock drive circuits are used.

If one clock drive circuit can drive three BBDs, only one clock drive circuit is required. The clock pulse obtained by the clock drive circuit 42 is supplied to the BBD 39.
is supplied to the zero cross detector 44 after removing the wow and flutter of approximately 1 Hz or more from the low frequency signal of approximately 4BOHz including the wow and flutter by increasing the delay time m. After a cyclic component is removed by a pass filter (not shown), a zero cross is detected, shaped into a pulse, and supplied to the PLL 45.

Moreover, the audio signals of the first channel and the second channel that enter the input terminals 46 and 47, respectively, are connected to the variable resistors 48 and 47, respectively.
The input sensitivity is adjusted with 49, and the low pass filter is 50.51.
The high-frequency components that cannot be transferred with BBD are removed, and each BB
D52.5 S is supplied. These BBDs 52 and 53 have the same number of stages as the BBD 39, and are supplied from the lock drive circuit 43, and are synchronized with the audio signals of the first and second channels by varying the delay time of the lock pulse. Wow and flutter of approximately IH2 or higher are removed and supplied to low-pass filters 54 and 55. 1st. The audio signals of the second channel are converted to BBD by low-pass filters 54 and 55, respectively.
52.BBD with the clock component mixed in 53 removed.
Supplied to S6.57.

Here, in order to eliminate wow and flutter at approximately IHz or higher, the delay time of BBD3$l, 52.53 is set to a long value, and the delay time of BBD39, 52.53 is set to be long. ing. For this reason, for wah and black at high frequencies (for example, 10 Hz or higher), the phase lag due to delay becomes large and cannot be removed.
Pilot signal which is the output of BBD39,52.53,
1st. The second channel audio signal similarly contains this high frequency flutter component.

Frequency 480 with low frequency wow and flutter removed by BBD 39 and waveform shaped by zero cross detector 44
The pilot signal of H2 is supplied to PLL45. This pulse with a frequency of approximately 480Hz is PLI.

Frequency fluctuation (flutter) of approximately 10H2 or more at 45
is detected and taken out as a stain pressure change by the loop filter built in the PLL 45 and supplied to vcosa. v
The oscillation frequency of 7 is changed according to the oscillation frequency, and this is supplied to the clock drive circuit 60, where the clock pulse obtained by waveform shaping is 13BD.
Supplied to S6.57.

BED56,. No. 57 has a small number of stages, and the delay times t and c are optimal for removing flutter of 10 to 50 Hz. The BBDs 56 and 57 each have a clock drive [il circuit 0 and a clock pulse from the clock pulses to vary the delay time j to the first. 10-50H from the second channel's voice actor Akira
2 flutter is removed and the signal is supplied to low-pass filters 61 and 62. The audio signals of the first and second channels are EBD! After the mixed clock component is removed by the 1615T, the signal is amplified by the amplifier 61.64, the output level is adjusted by the variable resistor 65.66, and the signal is output from the output terminal 67.611.

Here, when the modulated wave is recorded and reproduced in the magnetic deso 18, the modulated wave is limited to the band #RfIili. In addition, when amplitude modulating a sinusoidal pilot signal with a pulsed control signal, the waveform of the modulated wave becomes as shown in Figure 5 (Al), and its frequency spectrum is as shown in Figure 5 (Bl).
As shown in the figure, it has a wide band sideband, and when this modulated wave is recorded and reproduced, the band is limited and the upper and lower sidebands are asymmetrical, and the higher-order sidebands are The reproduced modulated wave is subjected to amplitude and phase distortion and includes wow and flutter. Figure 5 (C1 is the modulated wave shown in Figure 15) After passing through a low-pass filter with a cutoff frequency of 2 KHz, wow and flutter were measured.
Contains flutter. However, if the high-frequency component of the control signal is removed and then the width adjustment is performed as in the above embodiment, the sideband of the modulated wave is an extremely narrow band and is not subject to band limitations during recording and playback. , the reproduced modulated wave does not contain wow and flutter components.

Next, the envelope of the modulated wave shown in FIG. 5(m) becomes a pulse as shown in FIG. The pulse shown in FIG. 6 is Fourier transformed as shown in the following equation.

Tatami A is a constant By substituting 00=-π into this equation (1), the following equation is obtained.

Equation (2) in Section 1 represents the fundamental wave when n = 1, and this frequency is approximately 3QH2, which is the same as the frequency of the control signal.
27A 1 , approximately J8GHz is expressed by −×− from equation (2), and 1
6 2 There is a carrier wave from approximately 4110H2 to 3QHg
The first side wave (fundamental wave of the pulse) represented by n = 1 on the top and bottom
There is a second side wave represented by n=2 above and below 60H2,
The distribution is similar below.

In this way, if the modulated wave shown in Figure 5 (A1) is calculated and synthesized to create a haiku wave band consisting of harmonics of orders within the range that is not subject to band limitation during recording and reproduction, the wah wave due to the above band limitation can be obtained.
No flutter occurs.

FIG. 7 shows a block system diagram of a second embodiment of the recording system of the apparatus of the present invention based on the above idea. In the same figure.

The same parts as in the IEI diagram are given the same reference numerals, and their explanations will be omitted. t47 In the figure, when the switch SW2 is closed, the flip-flop TO is set by the voltage (+B), and the Q output of the flip-flop 70 sets the terminals 71a and 71d of the switch T1, Lfb, 7181ytc, and 7.
Connect 1g, power supply (10B) switch sw2゜terminal 1
It is supplied to the reset terminal of the counter 72 via 1g e 71c, and the 204B counter 72 is reset. Further, the Q output of the flip-flop 10 is supplied to the microcomputer T3, and the microcomputer T3 starts the calculation described below.

FIG. 8 shows the calculation broachyard performed by the microcomputer 73. As shown in the figure, after the start of calculation, the number N of upper and lower waves (N is a positive integer, for example 10≦
In experiments, good results were obtained when N≦15), and values such as A and K(0) indicating the degree of modulation are initially set. Next, 5in (z7rN/32) in equation (2), , (
2,, Nizite, Woka, L tx 1is27πN/
32 Calculate. approximately 480Hz (480=30X16
), and set the calculated value of (2) a above every 30H2 above and below about 480H2 as the center. Since the memory T4, which will be described later, has 2048 words, the sixth
One period of the illustrated pulse 2π (rad:] is 22048
to determine the increments of θ. Thereafter, calculation using equation (2) is performed for each θ, and the calculated value and write pulse are output.

The calculated value from the microcomputer 73 is supplied to the memory 74, and immediately thereafter a write pulse is supplied to the memory 74 via the terminal 71.71a of the switch 71. The memory 14 is supplied with the count value of color/return 72 as address information.

The memory 74 writes the calculated value from the microcomputer to the designated address. The write pulse is also supplied to the count input terminal of the counter 72 via the terminal T1e (711) of the switch T1.

The counter 72 is the falling edge (end portion) of this write pulse.
Detect and improve your man's personality. In this way, in the memory 74, θ is changed from 0 to 0 in equation (2) for each word.

48 or the calculation results changed from τi to 2π [ra6] ago are written, and when all writing is completed, the counter 72 overflows and supplies a reset signal to the reset terminal of the flip-flop 10, and the program for the above calculation is finish. This K shift flip-flop 70 inverts its Q output and outputs it to the terminal 71a of the switch 71.
, 71d is opened, terminals rtb and 71f, 71 and 71h
Connect.

The 30Hss pulse from the frequency divider 4 is supplied to the phase comparator T and also to the monomulti 75.

The monomulti 75 is triggered by the rising edge of this pulse and generates a pulse with a predetermined pulse width, which is then passed through the switch T1.
is supplied to the reset terminal of the counter 72 via terminals 71h and 71e. Also, the frequency divider 8 divides the pulse with a frequency of approximately 491 KHz from the vaog into 1/16384.
The frequency is divided and a pulse with a frequency of approximately 30 Hz is supplied to the phase comparator 7, and a pulse with a frequency of approximately 491 kHz is divided by 1/
Divided by 8, the frequency is approximately 61.4KHz (204 of 30HH).
8 times the frequency) from the terminal 9a to the sample hold circuit 18 and the terminal 71f of the switch 71.
, 7 lb to the clock input terminal of counter T2. The counter γ2 starts counting when the pulse from the monomulti T5 falls, and counts from 0 to 2047″& in one cycle of the control signal.Here,
By changing the time constant of the mono-multi γ5 and the pulse width of the pulse output from the mono-multi T5, it is possible to obtain a consistent phase between the control signal and the composite modulated wave shown in FIG. 9+Al. The count value of the counter 72 is stored in the memory T.
4. Supplied as head address information.

Memory T4 stores at the specified address (2)
Reads the calculated value of the formula. This calculated value is converted into an analog value in the DAf converter 17 and then supplied to the sample and hold circuit 18, where it is sampled at the high level of the pulse supplied to the terminal 9a of the frequency divider 59 and is sampled at the low level. The access time of memory T4 and D
After the variations in conversion time of the Af converter 77 are corrected,
The signal is supplied to the amplifier 14 after the clock component (pulse at terminal 9a of frequency divider 9) used for sample and hold is removed by a low-pass filter 79.

The waveform of the synthesized modulated wave obtained in this way with N=12 is as shown in Figure 9 (Al), and its frequency spectrum is almost 0 to l KH as shown in Figure S (B).
It is a frequency component within 2. Here, when the circuit shown in the first diagram is used for the recording system, the wah/wah signal included in the pilot signal is
In order to reduce the flutter to less than 1% pp, the linearity of the modulator 12 must be very good, which is very difficult to achieve.

Figure 9 (The synthesized modulated wave shown in Al is cutoff frequency I
KH5! The wow and flutter after passing through the l low-pass filter is at most 0.05%pp, as shown in Figure 9 (0).
As described below, since this synthesized modulated wave is recorded and reproduced on the 8-key tape 18, wow and flutter hardly occur even if the band is limited.

FIG. 10 shows a block system diagram of a modification of the second embodiment of the recording system of the apparatus of the present invention. In this figure, the same parts as in FIG. 7 are given the same reference numerals, and the explanation thereof will be omitted. The memory 80 is (2
) is a read-only memory in which the calculated value of the formula is already stored, and its storage capacity.

The address is the same as memory T4. This memory 80
Even when using the circuit shown in FIG. 7, the operation of synthesizing the modulated waves is the same as that of the circuit shown in FIG. 7, and the explanation thereof will be omitted.

Note that in the circuits shown in Figures 7 and 10, Memo 1J74°80
The memory capacity is set to 2048 words, but by increasing this memory capacity, the increments of θ for creating the synthesized modulated wave are made smaller, and the wow and flutter included in the reproduced signal is greatly reduced. can, memory capacity,
The frequency of the pulses at the terminal 9a of the frequency divider 9, the DAi converter 77, etc. is not limited to the above embodiment. .

As described above, the magnetic recording/reproducing apparatus according to the present invention uses a control signal with a constant frequency from which high-frequency components have been removed to cause a rotating head to perform tracking scanning on a track inclined with respect to the longitudinal direction of a magnetic tape. A carrier wave with a frequency that is an integer multiple of the signal frequency has an amplitude f! I
l[ to obtain the modulated wave.

A modulated wave is recorded on a longitudinal control track, an audio signal is recorded on a longitudinal audio track, and the modulated wave reproduced from the control track is demodulated to obtain a control signal and synchronized with the control signal. A control signal is added to the control track in order to obtain a signal with the same frequency as the carrier wave, detect the frequency fluctuation of the signal with the same frequency as the carrier wave, and remove wow and flutter contained in the audio signal reproduced from the audio track. The carrier wave that becomes the pilot signal can be recorded and reproduced, and due to the band limitation during recording and reproduction, the reproduced pilot signal hardly contains any wow and flutter. A distortion-free audio signal can be obtained by removing the wow and black components of the audio signal from the frequency fluctuations of the reproduced pilot signal, and the modulated wave is formed by the envelope of the desired modulated wave. Using a Fourier-transformed formula for the pulse waveform, the sidebands that are not subject to band limitations during recording and reproduction are synthesized, making it possible to further reduce wow and flutter contained in the reproduced pilot signal. It has the following features.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the recording system of the apparatus of the present invention). Lock system diagram, FIG. 2 (Al-(Fl is a time chart showing signal waveforms of each part of the circuit shown in FIG. 1, FIG. 3 is a block system diagram of one embodiment of the reproduction system of the device of the present invention, FIG. A
l-(C1 is a time chart showing the signal waveforms of each part of the circuit in Fig. 3, Fig. 5 (AI, fBl, (C1 is the waveform 1 frequency spectrum of the modulated wave when using a loop-shaped control signal) , a diagram showing Wow Black,
FIG. 6 is a diagram showing a noculus subjected to Fourier transformation. FIG. 1 is a block diagram of a second embodiment of the recording system of the apparatus of the present invention, and FIG. 8 is a microcontroller shown in FIG. Calculation flowchart in user T3), 1lE9
Figure 10 is a block system diagram of a modification of the second embodiment shown in Figure 7. 1.19a, t!lb, 30, 46.47... Input terminal, 2... Synchronization signal separation circuit, 3... Vertical synchronization signal separation circuit, 4.9.38... Frequency divider ,s,s,ys・
... Monomulti, 1... Phase comparator s 8.41.
5 s・voo. 10.72...Counter, 11,13,50,51゜54,55,61.62.7...Low pass filter, 12
...Modulator, 14, 20a, 20b, 63.64...
・Amplifier, 15.21 &, 211)...Mixer, 16
...Bias, oscillator, 17.22a, 22b...
Magnetic head, 18...Magnetic tape, 31...AGO
Amplifier, 32... Demodulator, 33... Limiter s
34136144...Zero cross detector, 37.40
．． 45...PLLm 3s, 52.53.56°5
T...BBD, 42.43.60...Clock drive circuit, 67.68...Output terminal, TO...Flip-flop, 71...Switch, 7B...Microcomputer, T4...・Memory, 77...DAi
converter, 78...sample hold circuit. Figure 3 Figure 4 Figure 6 Figure 5 AI Figure 9 fAI M wave number [Hzl tC+ Procedure amendment form] May 1, 1980 Director General of the Patent Office Mr. Uyoko Shimada (Patent Office Examiner) 16 Incident Display Showa 5th Fii Patent Application No. 5249
No. 2 Name of Invention: Magnetic Recording and Reproducing Device & Correction Person Patent Applicant Address 8221 3-12 Moriya-cho, Kanayō-ku, Yokohama-shi, Kanagawa Name (432) Victor Japan Co., Ltd. Representative Director and President Michi Shiji - Part 4, Agent 6, Drawings subject to amendment. 2 Contents of amendments In the drawings, as shown in red ink on the attached drawing copy,
Figure (A), 03) J to r Figure 5 (A), 03),
(C) J To N Correct.

Claims (1)

[Claims] fi+ A signal from which high frequency components of a control signal of a constant frequency have been removed for causing a rotary head to perform tracking scanning on a track inclined with respect to the longitudinal direction of a magnetic tape, which is an integer multiple of the control signal frequency. A frequency carrier wave is amplitude-modulated to obtain a modulated wave, the modulated wave is recorded on a control track along the longitudinal direction, and an audio signal is recorded on the longitudinal audio track, and the audio signal is reproduced from the control track. Demodulate the modulated wave to obtain a control signal, obtain a signal with the same frequency as the carrier wave that is synchronized with the control signal, detect frequency fluctuations of the signal with the same frequency as the carrier wave, and reproduce from the audio track. A magnetic recording/reproducing device characterized in that it removes wow and flutter contained in a recorded audio signal. +21 Ill modulated wave is synthesized by using the Fourier transform formula of the pulse waveform formed by the envelope of the desired modulated wave to obtain sidebands that are not subject to band limitations during recording and reproduction. A magnetic recording and reproducing device according to claim 1, characterized in that: