JPS62102697A - Magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve S/N sufficiently and to reduce allowable color missing by devising the titled device that a delay time caused in a feedback component to avoid the effect even when the delay time is increased thereby utilizing the delay time caused in the feedback component. CONSTITUTION:A delay time taud of a delay circuit 3 is decreased by a delay time tau1 of a delay circuit 10 to form taud=1H-tau1. A phase advancing circuit 4 advances the phase of an input chrominance carrier signal (a) to advance the apparent time by the delay time tau1 of the delay circuit 10 to attain taua=tau1. The relation between the input chrominance carrier signal (a) through the phase advancing circuit 4 and a delay output signal by of the delay circuit 3 in an adder 5 is expressed as taud=1H-taua, and both equations taud=1H-tau1 and taud=1H-taua are established without discrepancy and since the tau1 is sufficiently smaller than the 1H, the relation of taud=1H is established practically. In selecting the delay time tau2 of the delay circuit 11 as tau2=tau1, the relation of taud+tau1=1H is established and a delay circuit between the input terminal 1 and the subtractor 8 is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording and reproducing apparatus (VTR) that sequentially records and reproduces color video signals on a magnetic recording medium, and in which a carrier color signal separated from a patented color video signal is recorded and reproduced. In a color signal processing circuit that performs low frequency conversion and guard panless recording so that a frequency interleave relationship is established between adjacent recording tracks, a 1H delay circuit is used to eliminate crosstalk from adjacent tracks during playback, and the A cyclic comb-shaped filter (also called a recursive filter) that has a configuration that returns the delayed output signal to the input side of the delay circuit.
The circuit has this characteristic.

BACKGROUND OF THE INVENTION In recent years, in order to reduce the amount of consumption of magnetic recording media and achieve high-density recording, magnetic recording and reproducing devices have begun to FM-modulate the luminance signal separated from the color video signal into a low-carrier FM luminance signal, and adjust the azimuth of the magnetic head. Guard panless recording is performed in a configuration that removes crosstalk from adjacent tracks by using the loss and by using the line correlation of the carrier color signal converted to the number of carrier color signals, but the image quality Improvements have not progressed at all. However, in recent years, in addition to high-density recording, there has been a movement towards higher image quality, and conventionally a comb-shaped circuit constructed using a 1H delay circuit is used to eliminate crosstalk from adjacent tracks of the carrier color signal. The configuration includes a recursive signal processing circuit that improves the characteristics of the filter circuit. Examples include replacing a conventional comb-shaped filter circuit with a recursive comb-shaped filter circuit, or leaving the conventional comb-shaped filter circuit intact. An example has been published in which a new recursive comb filter circuit is added.

An example of a conventional magnetic recording/reproducing device will be described below with reference to the drawings.

FIG. 6 shows an example of a recursive comb-shaped filter circuit of a color signal processing circuit of a conventional magnetic recording and reproducing apparatus.

In FIG. 6, 1 is an input terminal for the reproduced carrier color signal, 2 and 8 are subtracters, 5 is an adder, and 3 is a 1H delay circuit. 6 and 7 are coefficient circuits. Reference numeral 10 indicates a delay time caused by the coefficient circuit 6, and 11 indicates a delay time caused by the coefficient circuit 7, which are respectively divided into separate blocks as delay circuits. A delay circuit 12 corrects the delay time of the delay circuit 11.

9 is an output terminal.

The operation of the cyclic comb-shaped filter circuit of the color signal processing circuit of the magnetic recording/reproducing apparatus constructed as described above will be explained below.

First, the reproduced carrier color signal inputted to the input terminal 1 and the output delay signal of the 1H delay circuit 3 are added together in an adder 5, and the added signal is fed back through the coefficient circuit 6 and the delay circuit 10. A subtracter 2 performs subtraction, and the signal obtained by the subtraction is supplied to the 1H delay circuit 3. Further, the addition signal is passed through the coefficient circuit 7 and the delay circuit 11, the input carrier color signal is subtracted from the carrier color signal obtained through the delay circuit 12 by the subtracter 8, and the output carrier color signal is obtained at the output terminal 9.
Get more.

Through this series of operations, it exhibits characteristics that are better than those of conventional comb-shaped filter circuits, with sharp comb characteristics, noise such as crosstalk components from adjacent trunks is sufficiently removed, and carrier color with a good S/N ratio is achieved. I can get a signal.

In addition, when the line correlation is weak, such as when the hue changes in the vertical direction of the screen or when there is no color from a part of the screen, the color bleeds downward from the boundary between the colors (
In principle, the problem of cyclic comb filter circuits (hereinafter referred to as color fading phenomenon) exists, but in order to reduce this problem, an amplitude limiting circuit was added to the above configuration, and the line correlation was detected by some method. However, a method has been proposed in which the coefficients of the coefficient circuit e are switched depending on the strength.

Problems to be Solved by the Invention However, with the above configuration, if noise components such as crosstalk components from adjacent trunks are to be removed and the S/N of the reproduced carrier color signal is to be sufficiently improved, the coefficient circuit is It is necessary to make 1 large enough for a feedback factor of 6. Increasing the feedback coefficient by 1 means increasing the gain of the amplifier provided in the coefficient circuit etc.9 in an actual circuit, and the resulting delay time (phase delay), that is, the delay time of the delay circuit 1o. τμ increases. Furthermore, the addition of an amplitude limiting circuit or the like to reduce the color fading phenomenon described above further increases the gain of the amplifier and increases the delay time by 1. Tsu'! , B, If the effect of improving the S/N and the effect of reducing the color fading phenomenon are to be made sufficient, the delay time of the return portion will increase. Even if this delay time is minute, since it is fed back, it becomes a very large delay time, and in the end, the expected effect cannot be obtained.

The design conditions for the above-mentioned recursive comb filter circuit to operate normally are as follows: In the subtracter 2, the phase of the input carrier color signal and the feedback signal passed through the coefficient circuit 6 match, so that the 1H
When the delay time of the delay circuit 3 is τd, τd + τ1 = 1H...a In the adder 6, the phase of the input carrier color signal and the output signal of the 1H delay circuit 3 match, so that τd =1H...
...b In the subtracter 8, the phases of the output signal of the delay circuit 12 and the output signal of the coefficient circuit 7 match, so if the delay time of the delay circuits 11 and 12 is τ τ, then 1 b τd + τ2 = 1H + τb ...It's PaC. From b and formula 0, r2"" rb...
-d, and it can be seen that the delay time τb of the delay circuit 12 should be designed to be τ2. Also, from equations a and b, τ,=.

However, in reality, as mentioned above, 1〉o deshi,
In addition, since it is necessary to operate in the direction in which τ1 increases, a contradiction occurs.

Therefore, at present, the recursive comb filter circuit is not able to fully achieve its original performance, and it is difficult to arbitrarily set the feedback coefficient of the coefficient circuit and the amplitude limit level of the amplitude limit circuit, and There was a problem in that it was extremely difficult to obtain an effect of improving /N or an acceptable effect of reducing color fading.

In view of the above-mentioned problems, the present invention eliminates the influence of the delay time occurring in the feedback section, which prevents the original performance of the recursive comb filter circuit from being fully brought out, and eliminates the feedback coefficient and amplitude limit of the coefficient circuit. It is an object of the present invention to provide a magnetic recording and reproducing apparatus having a configuration and a system that can arbitrarily design the amplitude restriction level of the circuit and obtain a sufficient S/N improvement effect and an acceptable effect of reducing color fading.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing apparatus of the present invention has a method of apparently advancing the time by a time corresponding to the delay time occurring in the feedback section of the recursive comb filter circuit. By using a phase shift circuit such as a phase advance circuit that can be used, a delay circuit in which the delay time of a 1H delay circuit is shortened by a time corresponding to the delay time of the feedback section, or a delay circuit that has the same delay time as the delay time of the feedback section. , the subtracter 2 and the adder 6 operate in such a manner that the time relationship between the signals satisfies the original design conditions of the recursive comb filter circuit.

Operation The present invention uses the above-described configuration to correct the delay time occurring in the feedback section that restricts the performance of the recursive comb filter circuit, so that even if this delay time increases, its influence will not be affected. By doing so, the problem of not being able to obtain a sufficient S/N improvement effect or an acceptable effect of reducing discoloration due to the delay time generated in the feedback section can be solved.

Embodiment Hereinafter, a magnetic recording/reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a recursive comb filter circuit of a color signal processing circuit of a magnetic recording/reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is an input terminal for a reproduced carrier color signal, 2 and 8 are subtracters, 5 is an adder, 6 is a coefficient circuit that gives 1 to the feedback coefficient and has 1 in the delay time;
7 is a coefficient circuit that gives 2 to the coefficient and has a delay time τ2,
3 is a delay circuit that is shorter than 1H by the delay time τ1 of the coefficient circuit 6; 4 is a phase advancing circuit that apparently advances the time corresponding to the delay time τ1; and 9 is an output terminal.

FIG. 2 is an electric circuit diagram showing a specific example of the configuration of the coefficient circuits 6 and 7, and FIG. It was a hailstorm.

The operation of the magnetic recording and reproducing apparatus configured as described above will be described below with reference to FIGS. 3 and 2. Note that blocks having the same configuration as the conventional example shown in FIG. 6 are indicated using the same reference numerals.

First, the delay time τd of the delay circuit 3 is not the conventional 1H,
The delay time τ1 of the delay circuit 10 is shortened, and τd=1H−
When τ1...e, formula a of the above design of the subtractor 2 is satisfied.

The phase advancing circuit 4 advances the phase of the input carrier color signal to advance the apparent time by the delay time τ1 of the delay circuit 1o, and τ=τ1...
・Assuming f, in the adder 5, the relationship between the input carrier color signal passed through the phase advancing circuit 4 and the delayed output signal of the delay circuit 3 is as follows: τd=1H--old...q and e and Equation 9. holds true without contradiction, and at the same time τyu[IH
Since it is sufficiently short compared to , it satisfies formula b without any practical problems.

Furthermore, the delay time τ2 of the delay circuit 11 is expressed as τ2=τ1
...If h can be set, τd+τ2=1H...kawai), the delay circuit 1 as shown in FIG. 6 of the conventional example
2 becomes unnecessary.

As described above, according to this embodiment, the adder 5 adds the reproduction carrier color signal passed through the phase advance circuit 4 and the output delay signal of the delay circuit 3 whose delay time is slightly shortened by τ1.
Delay time τ1 of the feedback part of the recursive comb filter circuit
The feedback coefficient of the coefficient circuit 6 and the amplitude limiting level of the amplitude limiting circuit can be set arbitrarily, so that a sufficient S/N improvement effect and a sufficient effect of reducing color fading can be obtained. I can do it. Further, by making the delay time τ2 of the coefficient circuit 7 equal to τ1, the delay circuit 12, which was conventionally required, is no longer necessary, and the cost can be reduced.

Specifically, the phase advancing circuit 4 can be realized using only a capacitor and a resistor, as shown in an example shown in FIG. 2, and can be implemented at a very low cost.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of a recursive comb-shaped filter circuit of a color signal processing circuit of a magnetic recording/reproducing apparatus showing a second embodiment of the present invention. In the figure, in place of the phase advancing circuit 4 in FIG. 3, there is a delay circuit 13 having a delay time 1 equal to the delay time τ1 of the feedback section, and a delay circuit having a delay time τb equal to the delay time τ2 of the coefficient circuit 7. 12 is the third
Blocks having the same configuration as in FIG. 3 except for differences from the figures are indicated using the same reference numerals.

The operation of the magnetic recording and reproducing apparatus configured as described above will be explained below.

The reproduced carrier color signal is applied to the subtracter 2 through a delay circuit 13 having a delay time τat− equal to the delay time τ1 of the delay circuit 1Q, and the delay time τd of the delay circuit 3 is set to the delay time of the delay circuit 1o instead of the conventional 1H. Shorten by τ1 to 1, τ
If we assume that yu=r1゛°°°°j τd=1H−71°, then in the subtracter 2, the relationship between the output signal of the delay circuit 13 and the feedback signal passed through the coefficient circuit 6 is τd + τ1=1H・・・・・・・
・β Then, in the adder 5, the relationship between the reproduced carrier color signal and the output delay signal of the delay circuit 3 is as follows: τ+τd=1H...m, and the jxm equation holds true without contradiction.

In addition, in the subtracter 8, the relationship between the output signal of the delay circuit 12 and the output signal of the coefficient circuit 7 is τ 10τ+τ = 1H+τb or...0...nd2, and from the formulas m and n, the delay of the delay circuit 12 is time τ
It can be seen that b should be designed so that it becomes τ2.

As described above, according to this embodiment, the reproduced carrier color signal passed through the delay circuit 4 is supplied to the subtracter 2, and the signal obtained by the subtraction is supplied to the delay circuit 3 whose delay time is slightly shortened by τ1. Therefore, as in the first embodiment, the delay circuit 12
However, other than that, the same effect as the first embodiment can be obtained, and since a delay circuit is used instead of a phase advance circuit, the configuration is suitable for IC implementation. Obtainable.

A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a block diagram of a recursive comb-shaped filter circuit of a color signal processing circuit of a magnetic recording/reproducing apparatus showing a third embodiment of the present invention. In the figure, the phase advance circuit 4 is the coefficient circuit 6.
This block is different from the conventional example shown in FIG. 6 in that it is inserted after , and blocks having the same configuration as in FIG.

The operation of the magnetic recording and reproducing apparatus configured as described above will be explained below.

By inserting the phase advance circuit 4 which apparently advances the time corresponding to the delay time τ1 of the delay circuit 10 into the coefficient circuit 6, the relationship between the input carrier color signal and the feedback signal passed through the coefficient circuit 6 in the subtracter 2 is as follows. , τd+r1− ra= I H°°
In the ``°''0 adder 5, the relationship between the input carrier color signal and the 1H delayed output signal is as follows: Td=IH...p, and the equations 0 and 2 hold true without contradiction. The relationship between the output signal of the delay circuit 12 and the output signal of the coefficient circuit 7 in the subtracter 8 is as shown in equations c and d above.

As described above, according to this embodiment, the phase advance circuit 4 that apparently advances the time corresponding to the delay time τ1 of DLllo is inserted into the coefficient circuit 6, so that the delay circuit 12 as in the first embodiment is unnecessary. However, other than that, the same effect as the first embodiment can be obtained, and the delay circuit 3
Since the delay time is 1H, it is possible to obtain a configuration suitable for, for example, the case where the delay circuit 3 is used during recording in a magnetic recording/reproducing device.

Effects of the Invention As described above, the present invention improves the delay time of a phase advance circuit or a 1H delay circuit that can apparently advance by a time corresponding to the delay time occurring in the feedback portion of a recursive comb filter circuit. By using a delay circuit that is shortened by the time corresponding to the delay time of the feedback section, or a delay circuit that has the same delay time as the delay time of the feedback section, the time relationship of each signal in the subtracter and adder is changed to the original cyclic type. Conventionally, the performance of a recursive comb filter circuit has been restricted by providing a configuration that satisfies the design conditions of the comb filter circuit. It is possible to solve the problem of not being able to obtain a sufficient S/N improvement effect or an acceptable effect of reducing discoloration due to the delay time occurring in the feedback section.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a recursive comb-shaped filter circuit of a color signal processing circuit of a magnetic recording/reproducing apparatus according to the first embodiment of the present invention, and FIG. 2 shows an example of the phase advancing circuit of FIG. 1. 3 is a block diagram shown to clarify the delay time of the coefficient circuit in FIG. 1, FIG. 4 is a block diagram of the second embodiment of the present invention, and FIG. 5 is a block diagram of the second embodiment of the present invention. FIG. 6 is a block diagram showing the third embodiment. FIG. 6 is a block diagram showing a cyclic comb filter circuit of a color signal processing circuit of a conventional magnetic recording/reproducing apparatus. 1...Input terminal, 2,8...Subtractor,
3,12゜13...Delay circuit, 4...
Phase advancing circuit, 5... Adder, 6. Completed...
Coefficient circuit, 9...output terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person54
Figure 1

Claims (1)

[Claims] The reproduced carrier color signal and the delayed output of the delay circuit are added by an adder to create an added signal, and the added signal is subtracted from the reproduced carrier color signal by a first subtracter via a first coefficient circuit. creating a first subtraction signal and inputting it to the delay circuit;
The addition signal is subtracted from the reproduced carrier color signal by a second subtraction circuit via a second coefficient circuit and guided to an output terminal, and the addition signal is sent to the adder, the first subtracter, and the second subtracter, respectively. A phase advance circuit or a delay circuit is inserted into at least one of the input paths of the adder, the first subtracter, and the second subtracter so that the 1H time difference and phase of both input signals match, respectively. A magnetic recording and playback device featuring: