JPS6282713A - Waveform shaping circuit and magnetic picture recording and reproducing device using it - Google Patents

Abstract

PURPOSE:To eliminate a chattering component generated in an input signal regardless of the period or frequency change of the input signal by changing the sensitivity of a waveform shaping circuit in response to the frequency of the input signal. CONSTITUTION:An input signal Vin is fed to a terminal T1 and a sub carrier wave signal Sf in frequency 3.58MHz is fed to a terminal T2. The sub carrier wave signal Sf is subject to 1/1920 frequency division by a frequency divider 16 and the frequency division frequency signal fa is fed to a frequency divider 15 and an AND circuit 14. When a high level control signal v1 is fed to a terminal T4, the frequency signal fa is fed to each terminal T of flip-flop circuits 2-4 via an OR circuit 12. The frequency division ratio of the frequency divider 15 is 1/8, a frequency signal fb is fed to an AND circuit 13 and a high level control signal V2 is fed to a terminal T3, then the frequency signal fb is fed to each terminal T of the flip-flops 2-4 via the OR circuit 12. Thus, an output signal subject to waveform shaping without being affected by a chattering component is obtained.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a signal processing circuit that obtains an output signal from which chattering components generated in a pulse-like signal are removed, and a magnetic recording and reproducing device that applies this signal processing circuit, particularly an 8-dragon Regarding video.

[Background technology]

The magnetic recording and reproducing device known as 8-dish video has
A unique auto-tracking method is used. Regarding this method, see "Television Technology" (March issue, 1985).
Published by Denshi Gijutsu Publishing Co., Ltd., pp. 43-44). To give an overview, a pie signal f, = 102.5 ± 0.1 KHz, is recorded on four adjacent recording tracks of the magnetic tape along with a video signal and an FM audio signal.
, fl =1) 9fo, IKHz, f, = 165.2
KHz±0.1 KHz, f, =148.7±0.
1KHz k sequential recording. During playback, the pilot signals on both sides are detected and their levels are compared to achieve accurate tracking. This method is based on Automat-1c Trac Find
ing (hereinafter referred to as ATF).

By the way, the recording and playback method for 8B video is 5tnda.
rd Play Mode (hereinafter referred to as SP mode) and Long Play Mode (hereinafter referred to as LP mode).

As shown in FIGS. 4(a) and 4(b), the recording density in the LP mode is twice that of the SP mode. In LP mode, it is possible to record for a long time with one tape, but the image size is 1X.
is inferior to SP mode. Users can freely choose between SP mode and LP mode depending on their intended use.Furthermore, with an 8xx VTR, just by inserting a cassette during playback, the tape will be converted into an LP mode. It is necessary for the set to automatically determine whether it is in mode or SP mode, and to adjust the rotational speed of the capstan and drum to the rotational speed corresponding to each mode. For this control (servo) of the rotation speed, the four pilot signals f, -f are used similarly to the ATF. That is, by detecting all the cycles in which f, to f4 repeatedly appear, it is possible to determine whether the mode is LP mode or SP mode. The inventor of this application studied an ICi equipped with an automatic SP/LP discrimination circuit during playback, and the input signal was first input from the drum motor and the capstan motor.
, ~f4 signal is fully extracted, then frequency converted, noise components are removed through a waveform shaping circuit, and then the signal is input to the SP/LP discrimination circuit. SP
The /LP discrimination circuit discriminates SP/LP based on the input signal of the logic circuit used for IIL', for example. The waveform shaping circuit plays an important role in completely removing noise (chattering components) and applying accurate servo.

Removal of chattering components is, so to speak, waveform shaping.As a method for this, a pulse signal of a predetermined frequency is supplied to a shift register, a dead zone is provided for N pulse signals, and waveform shaping can be performed completely.

What must be noted here is that VTRs have various modes, including normal playback and high-speed playback such as search.

For example, the period of the detected pilot signal changes significantly between the normal LP mode and the SP mode such as search. By the way, it may change about 20 times compared to the normal LP mode.

The pilot signal is then converted into a pulse signal and A
Although it is supplied to the TF and capstan servo, chattering components occur before and after it. Comparing the search in the SP mode and the normal LP mode, the time width of the chattering component also changes as described above.

Studies by the authors of this invention have revealed that when the frequency of the input signal changes as described above, it is difficult to shape the waveform of the input signal.

In order to solve the above problems, we have repeatedly investigated the possibility of changing the frequency of the pulse signal that operates the entire waveform shaping circuit in response to changes in the cycle or frequency of the input signal. We realized that this can be done reliably and came to propose the present invention.

[Purpose of the invention]

An object of the present invention is to provide a signal processing circuit that can remove chattering components generated in the input signal, regardless of changes in the cycle or frequency of the input signal.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief summary of typical inventions disclosed in this application is as follows.

That is, the dead band width of the waveform shaping circuit is changed between standard playback and search, and, for example, the noise removal sensitivity of the waveform shaping circuit is increased during search, and the next noise removal is performed in accordance with the high-speed playback mode.

The outline of the waveform shaping circuit is as follows.

That is, the input signal is supplied to the first input terminal, and the input signal is supplied to the second input terminal.
a shift register whose input terminal is supplied with a pulse signal as a clock signal; and a frequency switching circuit which supplies pulse signals of different frequencies to the second input terminal according to a control signal. The pulse signal whose frequency changes in response to the change in frequency is
By supplying the input signal to the input terminal of and synchronizing the two, the dead band width is changed in accordance with the period and frequency of the input signal, which changes in response to the standard playback mode and the high-speed playback mode during search.

[Embodiment 1] Hereinafter, an embodiment of a signal processing circuit to which the present invention is applied will be fully described with reference to FIGS. 1(a) and 2(b) and FIG. 2.

Note that FIG. 1 shows a circuit diagram, and FIG. 2 shows a waveform diagram for explaining the circuit operation.

The feature of this embodiment is that the frequency of the pulse signal supplied to the shift register is switched in response to the chattering time width of all input signals or the mode selection of the electronic device in which this signal processing circuit is used, thereby eliminating the above chattering. The objective is to obtain a certain output signal.

Figure 1(b) illustrates this clearly.
It is. As the input signal Vin, as shown in the figure, the signal component and the noise (chattering) component can be applied to both signals by selecting a frequency divider by switching the switch SW and selecting the frequency divider. An output signal Vbe whose waveform has been shaped is obtained.

Next, a more specific circuit configuration of the waveform shaping circuit will be explained using FIG. 1(a)'r.

First, regarding the circuit configuration, 1 is a shift register, flip-flop circuits 2 to 4 degrees R-S flip circuit 5. It is composed of AND circuits 6 and 7. In addition,
The flip-flop circuits 2 to 4 are I I L (In
It is composed of integrated InjectionLogic).

1) is a frequency switching circuit, which includes an OR circuit 12, AND circuits 13, 14 . It is composed of frequency dividing circuits 15 and 16.

Although the signal processing circuit described above has a wide range of uses, the entire operation of the circuit will be explained when applied to the magnetic recording/reproducing apparatus shown in the second embodiment.

Terminal T receives an input signal Vln with a waveform as shown in FIG.
is supplied. The input signal Vin is a reproduced version of the pilot signal, and the rising period H is SP,! :
This is a signal for distinguishing between LP and LP, and the pulse-like signals shown before and after it are unnecessary chattering.

In this embodiment, the above-mentioned chattering is eliminated.

A subcarrier signal S with a frequency of 3.58 MHz is connected to the terminal T.
f is supplied. This frequency signal was selected because the signal processing circuit is used in a VTR, and its frequency is not limited to the above.

The subcarrier signal Sf is divided by the frequency divider 16 into 1
/1920, and the divided frequency signal fa is supplied to the frequency divider 15 and the AND circuit 14. The frequency of the frequency signal fa is approximately 1.86 KHz. When a high level control signal V is supplied to the terminal T4, the frequency signal fa is supplied to each T terminal of the clip-flop circuits 2 to 4 through the entire OR circuit 12. The frequency division ratio of the frequency divider 15 is set to 1/8, and the frequency signal fb is supplied to the AND circuit 13.

The frequency of the frequency signal fb is approximately 233 Hz. When the high level control signal 2 is supplied to the terminal T, the frequency signal fb is supplied to each T terminal of the flip-flop circuits 2 to 4 via the OR circuit 12.

The relationship between the set human power Vn, the reset human power Vc, and the output signal Vo for the input signals Vin, R-S F, and F in the waveform shaping circuit shown in FIGS. 1(a) and (b) is as shown in FIG. 2. .

As can be seen from the figure, in this embodiment, the outputs of the 3-stage D-type flip 70 tubes are ANDed, so the input Mi
The 701 outputs for n are Vin for 3 basic clocks.
When Vin continues to be in the rHJ state, it rises to the rHJ level, and when Vin for three basic clocks reaches rLJ in succession, it falls to the rLJ level.

By this operation, it is possible to obtain all output signals whose waveforms are not affected by chattering components.

S/ of this basic clock (sampling pulse) three times
The N discrimination operation is referred to as a dead zone of three clocks in the above-mentioned book.

It goes without saying that this dead zone can be varied by changing the number of stages of the D-type 7-lip 70-tub, but the present invention is characterized in that the operating clock frequency (sampling pulse) of the D-type flip-flop can be varied without changing the number of stages. . In other words, when the frequency of the input signal Vin is low, it is possible to distinguish between S/N (signal and noise) even if the clock frequency is low, but as the frequency of Vin increases, due to the dead zone when the clock frequency is low, K Kae・-te S/N
This results in a worsening of the ratio. Therefore, when the frequency of the input Vin becomes high, accurate waveform shaping operation can be performed by making the clock frequency follow the operational input signal Vin of the waveform shaping circuit.

The above switching using the control signals V, , V, may be performed in response to mode switching of the VTR. That is,
If the control signal ■ is supplied in the SP mode, the control signal v! is supplied in the LP mode. supply. In this way, the mode switching of the VTR will not malfunction due to chattering.

Next, a second embodiment of the present invention will be described below as an example of application of the above signal processing circuit to a VTR.

[Embodiment 2] Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

Note that FIG. 3 shows a block diagram of the main parts of the UVTR.

The feature of this embodiment is that SP, L
The present invention is configured to accurately perform the P discrimination operation and to automatically switch to the L mode, for example, the SP mode, when power is supplied.

21 is an 8-certified magnetic tape, which runs in the direction of the arrow. 22 is a recording track.

23 is a cue signal auxiliary track, and 24 is an audio auxiliary track.

The recording track 22 contains a video signal (including a color signal and a luminance signal), an FM audio signal, an ATF signal and an SP signal.
/LP discrimination pilot signals f, ~f4 are recorded.

31a and 31b are rotating heads, and the rotating heads 31a and 31b are rotated by the rotation of the drum 32 and the running of the tape 21.
begins to move on the tape along a trajectory indicated by 31.

Then, as the tape 21 runs, the pilot signal f,
~f4 are played alternately, switch S.

The signal is supplied to a mixer circuit 42 configuring a control circuit 41 via the control circuit 41 . At this time, the pilot signal of the adjacent recording track is also reproduced at the same time, and f! When driving! The tape 21 and the rotary heads 31a and 31b are controlled so that the reproduction level of , = f.

A local signal f of a predetermined frequency is supplied from a local oscillator 43 to the mixer circuit 42, and a beat component corresponding to the frequency difference between f and fl is supplied to the next stage bandpass filter circuit 44.

The output signal of the low-pass filter circuit 44 is detected,
The nine human force signal Vin shown in FIG. 2 above is obtained. Reference numeral 45 is the signal processing circuit shown in the first embodiment, which removes chattering as described above. Therefore, the ATF circuit 46 and the S P/L P discriminating circuit 52 are supplied with output signals Vd having different time widths corresponding to the tape speed and VTR mode as described above, and the output signals Vd are supplied to the ATF circuit 46 and the S P/L P discriminating circuit 52, and output signals Vd having different time widths correspond to the tape speed and VTR mode. Servo is done.

The circuit operation of the main servo will be described below as an example.

51 is a mode discrimination circuit, and 52 is S during playback.
This is a circuit for discriminating between P and LP.

In addition, VCC is a power supply, S is a power switch, and coil L
, and the capacitor cI constitute a power filter 53.

The switch Ss is momentarily turned off in the reproduction mode, and turned on in other modes.

That is, when the switch Ss'C is turned off in synchronization with the power on, the capacitor CtK is charged, and the voltage level at the inverting input terminal of the comparator 53 becomes higher than the reference voltage Vref.Then, the output of the comparator 53 When the level becomes low, the output level of the inverter 54 becomes high.

In response to this level change, the determination circuit 52 determines that the mode is reproduction mode and SP, but the latch circuit 55 determines that the inverter 5
The above mode is not latched when the output signal of No. 4 is low level. However, the discrimination signal output from the latch circuit 55 is in the SP mode and is displayed by the display circuit 56.

On the other hand, when switch S is turned on, capacitor C
7 discharge is performed, and the voltage level of the inverting input terminal of the comparator 53 becomes /T with respect to the reference voltage Vref. Comparator 53
The output signal of the inverter 54 becomes high level, and the output signal of the inverter 54 becomes high level.

As a result, the SP mode is locked by the latch 55, and the VTR becomes operable in the SP mode. In addition, S
Switching from P mode to LP mode, temporary stop, switching to recording mode, etc. are performed after the SP mode is canceled by another control circuit (not shown).

The main servo circuit 57 controls the rotation speed of the drum motor 61 and the capstan motor 70, and the rotation speed is controlled by the frequency signal DFG obtained from the frequency generator 62 and the capstan rotation signal CFG. Since the rotational speed of the capstan motor is different between the SP mode and the LP mode, the above input signal Vin
Although the frequency changes approximately 20 times, the chattering is removed in either case by the signal processing circuit 45, so that the SP/LP mode can be accurately determined and the rotational speed of the motor can be accurately controlled.

In addition, by temporarily switching the VTR'i to SP mode using the charging voltage of capacitor C2 when power is supplied,
The initial conditions of VTRs are unified.

〔effect〕

(1) A gate circuit that selectively transmits a pulse signal of a desired frequency in accordance with the frequency of an input signal supplied to the shift register, a frequency dividing circuit that divides the frequency of the pulse signal kl/NK, and a frequency dividing circuit that divides the frequency of the pulse signal kl/NK. and a gate circuit that selectively transmits all frequency signals, and selectively supplies the pulse signal to the shift register in response to the frequency change of the input signal, thereby responding to the frequency change of the input signal. making the shift register in an insensitive state for a period of time to remove undesirable chattering components appearing in the input signal;
This effect can be obtained.

(2) By providing the signal processing circuit shown in (1) above in the servo circuit of the kVTR, even if the time width of the chattering component changes accordingly, the frequency of the pulse signal can be selectively changed to the gate circuit. Since it can be varied by driving the
This provides the effect of reliably performing servo operation using an input signal from which chattering components have been removed.

(3) In the mode circuit of the VTR, a capacitor that maintains a desired voltage level and a switch circuit that makes the capacitor non-discharge in synchronization with the power supply are provided, and the voltage is compared with the charging pressure of the capacitor when the power is supplied. The mode discrimination circuit is driven to the SP mode by the control signal obtained by the control signal, and when a mode other than the SP mode is selected, the switch circuit is turned on to discharge the charge of the capacitor and the mode discrimination circuit is fully driven. This provides the effect of mode selection with a simple circuit configuration.

(4) Due to (3) above, the VTR mode is unified to tsP mode when power is supplied, and the next mode selection becomes easy.
Above, the invention made by the present inventor has been specifically explained based on examples, but the present invention is not limited to the above examples, and various modifications can be made without departing from the gist of the invention. Needless to say, it is deformable. For example, the frequency and frequency division ratio of the pulse signal supplied to the signal processing circuit are not limited to those mentioned above, and can be freely selected according to the conditions of the electronic device in which this signal processing circuit is used.

[Application field]

In the above explanation, the invention made by the present inventors will be mainly described in the field of application which is the background of the invention.
Although the case where it is applied to TR has been explained, it is not limited thereto, and for example, it can be applied to an IC having a waveform shaping circuit.
can be widely used.

[Brief explanation of drawings]

FIG. 1(a) shows a circuit diagram of a signal processing circuit for explaining the first embodiment of the present invention, and FIG. 1(b) shows a circuit diagram of a signal processing circuit for explaining the first embodiment of the present invention.
) is a block diagram showing a simplified circuit of the above-mentioned signal processing circuit. FIG. It is a diagram showing the circuit diagram of the main part of the servo circuit and fully explaining the P mode and LP mode. 1... Shift register, 2-4... Slip-flop circuit, 5... R-S flip-flop circuit, 6°7
．． 13.14...AND circuit, 1)...frequency switching circuit, 12...OR circuit, 15,16...frequency dividing circuit, f1-f,...pilot signal, 53...comparison device, S,, S,, S,...switch, C8... capacitor, 52... SP, LP discrimination circuit, 55...
Latch, 31...head. Representative Patent Attorney Katsutoshi Ogawa
1 Figure 1 (Ji Figure 2

Claims (1)

[Claims] 1. A waveform shaping circuit characterized in that the sensitivity of the waveform shaping circuit is changed according to the frequency of an input signal. 2. A shift register formed by connecting D-type flip-flops in multiple stages, a first AND circuit that receives each positive-phase output of the D-type flip-flops as input, and a first AND circuit that receives each negative-phase output of the D-type flip-flop as input. and an R-S flip-flop that uses the output of the first AND circuit as a set input and the second AND circuit as a reset input, and inputs an input signal to a shift register, The waveform according to claim 1, wherein the waveform is configured to obtain an output from an R-S flip-flop, and changes the clock frequency supplied to the D-type flip-flop according to the frequency of an input signal. Shaping circuit. 3. (1) Beat components of a plurality of pilot signals of a predetermined frequency recorded on a magnetic recording medium are supplied to the first input terminal with a time width change corresponding to a mode change of the magnetic recording/reproducing device, and a shift register whose second input terminal is supplied with a pulse signal whose frequency changes in response to the mode change, and a frequency which selectively supplies the pulse signal whose frequency changes in response to the mode change to the second input terminal; a signal processing circuit that obtains an output signal from which chattering components included in the beat component are removed by switching the frequency of the pulse signal; and (2) a capacitor that maintains a desired voltage level, which is in an open state when power is supplied. Then, the output signal obtained by supplying the above voltage level to the comparator drives the mode discrimination circuit to automatically set the regeneration mode, and when a mode other than the regeneration mode is selected, it becomes closed and discharges the above capacitor. A switch circuit for driving the mode discrimination circuit to switch modes other than the reproduction mode, and a switch circuit for automatically maintaining the reproduction mode when power is supplied, and using the output signal of the signal processing circuit for mode discrimination. A magnetic recording and reproducing apparatus characterized in that the magnetic recording and reproducing apparatus is also supplied to a servo circuit and controls the rotational speed of the motor in response to the mode switching.