JPH08126027A - Signal processor for video tape recorder - Google Patents

Abstract

PURPOSE: To obtain a comb-line filter characteristics without needing level adjustment and delay time adjustment even when the level of paths for a delay element and its delay time are in dispersion in the signal processing circuit using the delay element. CONSTITUTION: This signal processing circuit comprising a delay element 2 delaying an input signal by one horizontal scanning period, a variable amplifier 3, a variable phase shifter 4, a level comparator 5, a phase comparator 6 and a subtractor 8, compares the level of an input signal with the level of the output signal of the variable phase shifter 4 delayed by one horizontal scanning period and controls the gain of the variable amplifier 3 so as to make the levels match with each other. The phase comparator 6 compares the phase of the input signal with the phase of the output signal of the variable phase shifter 4 to control the spase of the variable phase shifter 3 so that the phase difference is 180 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device for a video tape recorder which separates a video signal into a luminance signal and a chrominance signal for recording and reproduction.

[0002]

2. Description of the Related Art In a two-head helical scan type video tape recorder (hereinafter referred to as VTR), an input color television signal is separated into a luminance signal and a color signal, and an FM-modulated luminance signal (hereinafter referred to as a luminance signal). (Referred to as FM luminance signal) and the converted color signal converted into the low frequency band of the FM luminance signal are mixed and recorded on the magnetic tape. Since the luminance signal and the color signal of the color television signal are frequency-multiplexed, it is generally difficult to completely separate the luminance signal and the color signal. Conventionally used Y / C separation methods include a frequency separation method and a comb filter method using a delay element. As a method using a comb filter using a delay element, for example, Japanese Patent Publication No. 4-630
By configuring as disclosed in Japanese Patent Publication No. 89, the band of the luminance signal and the color signal is wide band.

In order to extend the recording time,
High-density recording is performed without a guard band between adjacent tracks. In order to avoid crosstalk interference from adjacent tracks at the time of reproduction, the rotation of the color signal is switched by recording every horizontal scanning period (hereinafter referred to as H), and then the adjacent crosstalk component is reproduced by a comb filter using a delay element at the time of reproduction. Has been devised to remove. For example, as disclosed in Japanese Examined Patent Publication No. 1-23718, a comb filter is configured by calculating a signal around 1H using a delay element to reduce adjacent crosstalk components and noise components. .

[0004]

In the above-mentioned prior art, since the comb filter is constructed by using the delay element, Y /
The C separation comb filter can broaden the bandwidth of the luminance signal and chrominance signal and reduce the noise component at the time of reproduction, but when the level of the delay element path and the delay time vary, the amount of attenuation that is important as a comb filter characteristic is insufficient. Also, the frequency shift of the zero point occurs, and the ability to remove the Y / C separation comb filter and the adjacent crosstalk component decreases. In order to ensure the performance of the comb filter characteristic, it is necessary to set the level of the delay element path and the delay time to specified levels. For this purpose, it is necessary to adjust the level and the delay time, and there is a problem in reducing the cost and the substrate area.

The object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate the need for level adjustment and delay time adjustment even when the level of the delay element path and the delay time vary, and a comb filter. An object of the present invention is to provide a signal processing circuit using a delay element capable of ensuring characteristic performance.

[0006]

In order to solve the above problems, the present invention provides a signal processing circuit using a delay element of 1H or 2H, which includes a variable amplifier and a variable phase shifter in a path passing through the delay element. And a means for controlling the variable amplifier by comparing the output and input levels of the delay element path including the variable amplifier and the variable phase shifter with a level comparator, and the output of the delay element path including the variable amplifier and the variable phase shifter. And means for controlling the variable phase shifter by comparing the input phase with a phase comparator,
A means for controlling the operation period of the means is provided.

[0007]

According to the present invention, the variable amplifier is controlled by the level comparator by the above structure so that the level of the path of the delay element matches the level of the input signal. Further, the variable phase shifter is controlled by comparing with the phase comparator so that the delay time of the path of the delay element becomes a specified delay time with respect to the input signal. Further, by operating the means only during the burst period, it is possible to achieve the specified level and delay time regardless of the signal content. By the above method,
Even when the level of the delay element path and the delay time vary, it is not necessary to adjust the level and the delay time,
In addition, the performance of the comb filter characteristic can be secured.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a signal processing circuit using a delay element according to the present invention.
The signal processing circuit of the present invention comprises an input terminal 1 and a delay element 2.
, Variable amplifier 3, variable phase shifter 4, and level comparator 5
, Phase comparator 6 and burst gate pulse input terminal 7
And a subtraction circuit 8 and an output terminal 9.

The signal input from the input terminal 1 is supplied to the level comparator 5, the phase comparator 6, and the subtraction circuit 8 via the delay element 2, the variable amplifier 3, and the variable phase shifter 4. The level comparator 5 compares the level of the signal input from the input terminal 1 with the level of the signal delayed by 1H, which is the output of the variable phase shifter 4, and controls the gain of the variable amplifier 3 so that the levels match. This makes it possible to adjust the level without adjustment. In addition, the phase comparator 6 compares the phase of the signal input from the input terminal 1 with the phase of the signal delayed by 1H which is the output of the variable phase shifter 4, and the phase of the variable phase shifter 3 is adjusted so that the phase difference becomes 180 degrees. To control. This makes it possible to adjust the phase without adjustment. A signal corresponding to the burst signal period is input from the input terminal 7, and the level comparator 5 and the phase comparator 6 are controlled to operate only during the burst signal period. As a result, stable level and phase adjustment can be performed regardless of the signal content. Input terminal 1
The output of the variable phase shifter 4 is subtracted from the signal input to the subtraction circuit 8
By subtracting with, a comb filter characteristic with a horizontal synchronizing frequency (fh) period is obtained, which is output from the output terminal 9.

Next, FIG. 2 shows a concrete example of the phase comparator 6 according to the present invention, and FIG. 3 showing the waveform of the phase comparator 6.
The operation will be described using. The phase comparator 6 includes an input terminal 10 for an undelayed signal, an input terminal 11 for a 1H-delayed signal, a 90-degree phase shifter 12, and a multiplier 13.
An LPF 14 for extracting a DC component, a comparator 15 for comparing with a reference voltage Vr, and an output terminal 16. As shown in FIG. 3A, a signal having a phase inverted every 1H (line) is input to the input terminal 10 and input to the multiplier 13. The signal shown in FIG. 3B obtained by delaying the signal shown in FIG. 3A by 1H is input to the input terminal 11, and the 90-degree phase shifter 12 produces the signal shown in FIG. Is entered. The output of the multiplier 13 becomes the signal shown in FIG. 3 (D), and the DC component is taken out by the LPF 14 and the comparator 1
At 5, it is compared with the reference voltage Vr. The result of comparison by the comparator 15 is output to the output terminal 17, and the phase amount of the variable phase shifter shown in FIG. 1 is controlled.

FIG. 4 shows the delay amount of the variable phase shifter 4 and the comparator 1.
5 shows the relationship of the voltages input to the variable phase shifter 5, when the delay amount of the variable phase shifter 4 is T, the delay amount of the delay path including the delay element is 1H, and the voltage input to the comparator 15 is shown. Becomes equal to the reference voltage Vr. The delay amount of the variable phase shifter is T-Δ
When T ₁ , the delay amount of the delay path including the delay element is 1H-
Since ΔT ₁ , the voltage input to the comparator 15 is Vr.
It becomes −ΔV, and a potential difference between the reference voltage Vr and ΔV occurs. This potential difference is detected by the comparator 15 and detected by the variable phase shifter 4
The delay amount of the variable phase shifter can be set to T, that is, the delay amount of the delay path including the delay element can be set to 1H by controlling.

Next, FIG. 5 is a characteristic diagram of the phase comparison 4 in which the phase amount that can be varied by the variable phase shifter 4 is set to 1/2 or less of the cycle (1 / fsc) of the subcarrier frequency (fsc). Will be explained. FIG. 5 shows the relationship between the delay amount of the variable phase shifter 4 and the voltage input to the comparator 15. The control system is stable when the voltage input to the comparator 15 and the reference voltage Vr of the comparator 15 are equal, but the delay of the variable phase shifter 4 is T ± n / 2fsc (n is an integer). There will be a stable point. That is, the delay amount of the delay path including the delay element becomes 1H ± n / 2fsc, and the frequency of the zero point of the comb filter deviates and the performance deteriorates. Therefore, by setting the delay amount that can be varied by the variable phase shifter 4 to 1/2 fsc or less, the delay amount of the variable phase shifter 4 is always T, in other words, the delay amount of the delay path including the delay element is 1H. You can get control to work.

As described above, according to this embodiment,
Even when the level of the path of the delay element 2 and the delay time vary, the variable amplifier 3 is provided on the path passing through the delay element 2.
And a variable phase shifter 4 are provided, the level comparator 5 compares the output level and the input level of the path of the delay element 2 including the variable amplifier 3 and the variable phase shifter 4 to control the variable amplifier 3, and the variable amplifier 3 By controlling the variable phase shifter 4 by comparing the output and input phases of the path of the delay element 2 including the variable phase shifter 4 with the phase comparator 6, it is possible to eliminate the level adjustment and the delay time adjustment. .

Next, another embodiment will be described with reference to FIG.
The present embodiment is an example of configuring a feedback comb filter in which the band characteristic of the comb filter is narrowed to increase the noise component reducing capability. The same parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be partially omitted.

The signal processing circuit of this embodiment is different from the signal processing circuit shown in FIG. 1 in that it has a limiter 24 and a level setting circuit 2.
5, an adder 23 for adding the output of the variable phase shifter 4 and the input signal, and a level setting circuit 25 from the input signal
The difference is that it has a subtracter 22 for subtracting the output of.

In FIG. 6, the signal input from the input terminal 21 passes through the subtractor 22 and the 1H delay path consisting of the delay element 2, the variable amplifier 3 and the variable phase shifter 4, and is added to the input signal by the adder 23. And a comb filter of the luminance signal is formed. By subtracting the output of the adder 23 from the signal input from the input terminal 21 via the limiter 24 and the level setting circuit 25, a comb-shaped filter characteristic of a narrow band color signal having a large noise component reduction capability is formed. Then, it is output from the output terminal 26. The 1H delay path is composed of the delay element 2, the variable amplifier 3, the variable phase shifter 4, the level comparator 5, and the phase comparator 6 as described in the embodiment of FIG. In this case, the level adjustment and the delay time adjustment can be eliminated.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, first, a Y / C separation comb filter is constructed by constructing a comb filter for color signals without adjustment, and using this signal to construct a comb filter for luminance signals. Is. The same parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof is partially omitted.

The signal processing circuit of this embodiment is based on the BPF 32.
The difference from the signal processing circuit shown in FIG. 1 is that it has a phase circuit 33, a subtractor 34, and a luminance signal output terminal 35.

In FIG. 7, a BPF 32 extracts a color signal including a high frequency component of a luminance signal from a signal input from an input terminal 31, and the delay element 2 described in the embodiment of FIG.
A comb-shaped filter for color signals, which includes a variable amplifier 3, a variable phase shifter 4, a level comparator 5, a phase comparator 6, and a subtracter 8, removes a high-frequency component of a luminance signal and extracts only a color signal. You can The output of the subtractor 8 is output to the color signal output terminal 36 and is also supplied to the subtractor 34. On the other hand, the signal input from the input terminal 31 is the BPF.
It is supplied to the subtractor 34 via the phase circuit 33 having the same group delay characteristic as 32, and the subtracter 34 subtracts the color signal to form a comb-shaped filter for the luminance signal, and the luminance signal is output to the output terminal 35. Is output.

As described above, according to this embodiment,
Even when the level of the delay element path and the delay time vary, the variable amplifier 3 and the variable phase shifter 4 are provided in the path passing through the delay element 2, and the path of the delay element 2 including the variable amplifier 3 and the variable phase shifter 4 is provided. Of the delay element 2 including the variable amplifier 3 and the variable phase shifter 4 is controlled by the level comparator 5 to compare the output level and the input level of the variable comparator 3 with each other. By controlling the variable phase shifter 4 by comparison, a comb filter for a color signal without level adjustment and delay time adjustment can be constructed, and this signal is subtracted from the input signal having the phase circuit by the subtracter 34. Since the luminance signal can be formed by subtraction, level adjustment and delay time adjustment can be eliminated when forming a Y / C separation comb filter.

Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, in a configuration for obtaining a luminance signal by subtracting a color signal obtained by a comb filter for a color signal from an input signal, a variable amplifier is provided so that the level and phase of the input signal and the color signal to be subtracted are equal. It is an example of a configuration in which a variable phase shifter is provided and controlled. The same parts as those of the embodiment shown in FIG. 7 are designated by the same reference numerals and the description thereof will be partially omitted.

The signal processing circuit of this embodiment is different from the embodiment shown in FIG. 7 in that it has a comb filter on the luminance signal processing side. The comb filter on the luminance signal processing side includes a subtractor 34, a variable amplifier 37, and a variable phase shifter 38.
And a phase comparator 39 and a level comparator 40.

The color signal separated by the comb filter is output to the output of the subtractor 8, and this signal is output to the variable amplifier 37,
A luminance signal is obtained by subtracting from the input signal by the subtractor 34 via the variable phase shifter 38. Since the variable gain device 37 is controlled by comparing the two signals input to the subtractor 34 with the level comparator 40, the level adjustment can be eliminated. Further, since the variable phase shifter 38 is controlled by comparing the phases of the both input to the subtractor 34 with the phase comparator 39, the phase adjustment can be eliminated. Variable amplifier 37,
The operations of the variable phase shifter 38, the level comparator 40, and the phase comparator 39 are the same as the configurations described in the embodiment of FIG.

As described above, according to this embodiment,
Even when the level and the phase of the BPF 32 and the phase circuit 33 vary, the level adjustment and the delay time adjustment can be eliminated while configuring the accurate Y / C separation.

FIG. 9 shows an arrangement in which the Y / C separation comb filter at the time of recording and the color signal noise reduction comb filter at the time of reproduction are configured so that one delay element is used in common and the adjustment is eliminated. This is an example. This can be realized by using the switch circuit 52 to switch between the signal input from the reproduction color signal input terminal 51 and the recording signal.

Although the NTSC system signal using the 1H delay element has been described above, the PA using the 2H delay element is used.
The same applies to L-type signals.

[0027]

As described above, according to the present invention, the variable amplifier and the variable phase shifter are provided in the path passing through the delay element even when the level of the path of the delay element and the delay time vary. The output and input of the delay element path including the variable amplifier and the variable phase shifter are controlled by comparing the output and input levels of the delay element path including the variable amplifier and the variable phase shifter with a level comparator. It is possible to eliminate the level adjustment and the delay time adjustment by controlling the variable phase shifter by comparing the phases of the above with the phase comparator.

Since the luminance signal can be constructed by subtracting from the input signal having the phase circuit using the signal of the comb filter for the color signal without the level adjustment and the delay time adjustment, Y / Even when the C-separating comb filter is constructed, the level adjustment and the delay time adjustment can be eliminated.

Furthermore, by using a comb filter for color signals without level adjustment and delay time adjustment, a Y / C separation comb filter at the time of recording and a color signal noise reduction comb filter at the time of reproduction are used. Therefore, the cost and the substrate area can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal processing circuit using a delay element according to an embodiment of the present invention.

FIG. 2 is a specific block diagram showing an embodiment of a phase comparator 6 according to the present invention.

FIG. 3 is a waveform diagram illustrating the operation of the phase comparator.

FIG. 4 is a characteristic diagram illustrating an operation of a phase comparator.

FIG. 5 is a characteristic diagram illustrating the operation of the phase comparator.

FIG. 6 is a block diagram of a signal processing circuit using a delay element according to an embodiment of the present invention.

FIG. 7 is a block diagram of a signal processing circuit using a delay element according to an embodiment of the present invention.

FIG. 8 is a block diagram of a signal processing circuit using a delay element according to an embodiment of the present invention.

FIG. 9 is a block diagram of a signal processing circuit using a delay element according to an embodiment of the present invention.

[Explanation of symbols]

 2 Delay element 3,37 Variable amplifier 4,38 Variable phaser 5,40 Level comparator 6,39 Phase comparator 8,34 Subtractor 12 90 degree phase shifter 13 Multiplier 14 LPF 15 Comparator 32 BPF 33 Phase circuit 52 switch circuit

Front page continued (72) Kazuaki Hori, Inventor Kazuaki Hori, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Hitachi Imaging Information Systems (72) Inventor Eiji Moro 1410 Inada, Katsuta-shi, Ibaraki Hitachi, Ltd. AV equipment Within the business unit

Claims (10)

[Claims] 1. A signal processing device of a video tape recorder for separating a video signal into a luminance signal and a chrominance signal and recording and reproducing the same on a recording medium, the path passing through a delay element for one horizontal scanning period or two horizontal scanning periods. A level comparator that includes a variable amplifier and a variable phase shifter and controls the variable amplifier by comparing the output level and the input level of the path of the delay element including the variable amplifier and the variable phase shifter, and includes the variable amplifier and the variable phase shifter. A comb filter for a color signal is configured with a phase comparator that controls a variable phase shifter by comparing the output phase and the input phase of the delay element path, and the comb filter for the color signal is reproduced. A means used as a color signal noise reduction circuit and a comb filter for a luminance signal by forming a comb filter for a luminance signal by subtracting a signal obtained by the color signal comb filter from an input signal during recording. A signal processing device for a video tape recorder, characterized by comprising at least one of the means constituting a separation filter. 2. The signal processing device for a video tape recorder according to claim 1, wherein the phase comparator comprises at least a 90-degree phase shifter and a multiplier. 3. The signal processing device for a video tape recorder according to claim 1, wherein the phase amount variable by the variable phase shifter is set to ½ or less of the cycle of the subcarrier frequency. 4. A variable amplifier and a variable phase shifter are provided in a path that constitutes a comb filter for a luminance signal by subtracting a signal obtained by a comb filter for a chrominance signal from an input signal, and both are subtracted. 2. A delay element provided with a level comparator for controlling a variable amplifier by comparing input levels and a phase comparator for controlling a variable phaser by comparing phases of both inputs to be subtracted. Signal processing circuit of the optimized video tape recorder. 5. A signal processing circuit using a delay element for one horizontal scanning period or two horizontal scanning periods, wherein a variable amplifier and a variable phase shifter are provided in a path passing through the delay element, and the variable amplifier and the variable phase shifter are included. A level comparator that controls the variable amplifier by comparing the output level and the input level of the delay element path and a variable phase shifter that compares the output and input phases of the delay element path including the variable amplifier and the variable phase shifter A signal processing circuit using a delay element, which has a phase comparator for controlling. 6. A signal processing circuit using a delay element for one horizontal scanning period or two horizontal scanning periods, comprising a variable amplifier and a variable phase shifter in a path passing through the delay element, and including the variable amplifier and the variable phase shifter. A level comparator that controls the variable amplifier by comparing the output level and the input level of the delay element path and a variable phase shifter that compares the output and input phases of the delay element path including the variable amplifier and the variable phase shifter A comb filter for a chrominance signal is formed by having a controlling phase comparator, and a comb filter for a luminance signal is formed by subtracting the signal obtained by the comb filter for a chrominance signal from an input signal. Thus, a signal processing circuit using a delay element, characterized in that a Y / C separation comb filter is configured. 7. A signal processing circuit using a delay element for one horizontal scanning period or two horizontal scanning periods, comprising a variable amplifier and a variable phase shifter in a path passing through the delay element, and including the variable amplifier and the variable phase shifter. A level comparator that controls the variable amplifier by comparing the output level and the input level of the delay element path and a variable phase shifter that compares the output and input phases of the delay element path including the variable amplifier and the variable phase shifter A comb filter for a color signal is configured to have a controlling phase comparator, and the comb filter for a color signal is used as a color signal noise reduction circuit at the time of reproduction, and at the time of recording, the color signal from the input signal is used. By subtracting the signal obtained by the comb filter for the luminance signal to form the comb filter for the luminance signal.
A signal processing circuit using a delay element, wherein a / C separation comb filter is configured. 8. A signal processing circuit using a delay element according to claim 5, wherein the phase comparator comprises at least a 90-degree phase shifter and a multiplier. 9. A signal processing circuit using a delay element according to claim 5, wherein the amount of phase that can be varied by the variable phase shifter is set to ½ or less of the period of the subcarrier frequency. . 10. A variable amplifier and a variable phase shifter are provided in a path forming a comb filter for a luminance signal by subtracting a signal obtained by a comb filter for a chrominance signal from an input signal, and both are subtracted. 8. A level comparator for comparing a level of an input to control a variable amplifier, and a phase comparator for comparing a phase of both inputs to be subtracted and controlling a variable phase shifter are provided. Signal processing circuit using a delay element.