JPH05183930A - Comb line filter - Google Patents

Abstract

PURPOSE:To reduce adjusting points and to resolve problems such as the increase of unstable elements or the like. CONSTITUTION:Reproduced signals are supplied to an adder 53 and a subtracter 54 and supplied to a CCD 63. A delay signal corresponding to one horizontal period of an NTSC system is extracted from the intermediate part of this CCD 63 through an amplifier 65 to a terminal 66, and a delay signal corresponding to the two horizontal periods of a PAL system is extracted from a terminal part through an amplifier 67 to a terminal 68. A signal from this terminal 66 is supplied to a low-pass filter 21. Further, signals from the terminals 66 and 68 are selected by a switch 22 corresponding to the system of the reproduced signals and supplied through a low-pass filter 23 to an equalizer circuit 24 to compensate the delay amount of the amplifier 67, for example. The signal from this equalizer circuit 24 and the signal from the low-pass filter 21 are selected by a switch 25 corresponding to the system of the reproduced signals and supplied to the adder 53. On the other hand, the signal from the equalizer circuit 24 is supplied to the subtracter 54.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comb filter suitable for use in a VTR for reproducing video signals of both PAL system and NTSC system.

[0002]

2. Description of the Related Art For example, there is a demand for viewing an NTSC video tape in an area where a television system adopts a PAL system. Therefore, conventionally, the color sub-carrier frequency of the video signal of the NTSC system is 4.43M of the PAL system.
Reproduction is performed at a frequency of Hz, and such a reproduction signal is supplied to a receiver for viewing.

By the way, a V for reproducing such a video signal
In TR, crosstalk removal of an NTSC chroma signal is performed using a delay signal of one horizontal period. On the other hand, crosstalk removal of the PAL system chroma signal is performed using a delayed signal of two horizontal periods. Therefore, for example, a comb filter as shown in FIG. 2 can be considered.

That is, in the figure, the reproduction signal supplied to the terminal 51 of the arithmetic IC 50 is supplied to the adder 53 and the subtracter 54 through the amplifier 52. Further, the signal from the amplifier 52 is taken out through the terminal 55. This terminal 5
The signal from 5 is supplied to the terminal 61 of the delay IC 60, and the signal supplied to this terminal 61 is CC through the amplifier 62.
It is supplied to D63.

From the clock terminals 71 and 72, NT
A clock signal of a predetermined frequency is supplied for each of the SC and PAL systems. These clock signals are selected (NTSC system → N, PAL system → P) according to the reproduction signal system by the switch 73, and the selected signals are supplied to the clock terminal of the CCD 63 through the terminal 64.

As a result, when the reproduction signal is of the NTSC system, a delay signal having a delay time corresponding to one horizontal period is taken out from the intermediate portion of the CCD 63 to the terminal 66 through the amplifier 65. When the reproduction signal is the PAL system, C
A delay signal having a delay time corresponding to two horizontal periods is extracted from the terminal end of the CD 63 to the terminal 68 through the amplifier 67.

Further, the signal from the terminal 66 is supplied to the equalizer circuit 82 for compensating the delay amount of the amplifier 65 through the low pass filter 81. The signal from the equalizer circuit 82 is supplied to the adder 53 through the terminal 56.
As a result, the adder 53 is supplied with a delay signal having a delay time corresponding to one horizontal period, the dropout compensation of the luminance signal is performed, and the signal is taken out to the terminal 58.

Further, the signal from the terminal 68 is supplied to an equalizer circuit 84 for compensating the delay amount of the amplifier 67 through the low pass filter 83. The signal from the equalizer circuit 84 and the signal from the equalizer circuit 82 are switched by the switch 85.
Select according to the playback signal system (NTSC system → N, P
AL system → P). Then, the selected signal is supplied to the subtractor 54 through the terminal 57.

Thus, when the reproduced signal is of the NTSC system, a delayed signal having a delay time corresponding to one horizontal period is supplied to the subtractor 54, and the chroma signal from which crosstalk is removed is taken out to the terminal 59. When the reproduction signal is the PAL system, a delay signal having a delay time corresponding to two horizontal periods is supplied to the subtractor 54, and the chroma signal from which crosstalk has been removed is taken out to the terminal 59.

However, in this circuit, the equalizer circuits 82 and 84 are adjusted according to the delay amounts of the amplifiers 65 and 67. Therefore, there are problems that the number of adjustment points at the time of manufacturing is increased, the manufacturing cost is increased, and the unstable elements are increased due to the adjustment. The present invention has been made in view of these points.

[0011]

The problem to be solved is that the conventional circuit has many adjustment points at the time of manufacturing, which causes problems such as an increase in manufacturing cost and an increase in unstable elements. is there.

[0012]

According to the present invention, a reproduction signal is supplied (terminal 61), a corresponding delay (CCD 63) is performed using a clock signal, and a first output means (amplifier 65) is used. A first delay signal having a delay time corresponding to one horizontal period of the first television system (NTSC system) is taken out, and two horizontal periods of the second television system (PAL system) are output through the second output means (amplifier 67). Has a delay circuit (IC60) adapted to take out a second delay signal having a delay time corresponding to (1), switches the first and second delay signals (switch 22), and switches the switched signal to the first signal. And a second output means, and an equalizer circuit 24 for compensating for the delay amount of either one of the second output means and the original reproduction signal to synthesize (subtractor 54) the clock signal of at least the chroma signal in the reproduction signal. Stoke removal is comb filters to be performed.

[0013]

According to this, the equalizer circuit to be adjusted is 1
However, it is possible to solve problems such as an increase in manufacturing cost due to an increase in the number of adjustment points and an increase in unstable elements.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a signal reproduced by a head 2 from a magnetic tape 1 is supplied to a reproducing amplifier 3. The luminance signal separated from the reproduction amplifier 3 is supplied to the demodulation circuit 4, and the demodulation signal is supplied to the de-emphasis circuit 5. Also, the chroma signal separated from the reproduction amplifier 3 is supplied to the color sub-carrier frequency conversion circuit 6, and, for example, PAL.
The high frequency is converted to 4.43 MHz of the system. The de-emphasized luminance signal and the high-frequency converted chroma signal are supplied to the adder 7, and the added reproduction signal is calculated by the calculation IC.
It is supplied to the terminal 51 of 50.

The reproduction signal supplied to the terminal 51 is supplied to the adder 53 and the subtractor 54 through the amplifier 52. Further, the signal from the amplifier 52 is taken out through the terminal 55. The signal from the terminal 55 is supplied to the terminal 61 of the delay IC 60, and the signal supplied to the terminal 61 is supplied to the CCD 63 through the amplifier 62.

From the clock terminals 71 and 72, NT
A clock signal of a predetermined frequency is supplied for each of the SC and PAL systems. These clock signals are selected (NTSC system → N, PAL system → P) according to the reproduction signal system by the switch 73, and the selected signals are supplied to the clock terminal of the CCD 63 through the terminal 64.

As a result, when the reproduction signal is of the NTSC system, a delay signal having a delay time corresponding to one horizontal period is taken out from the intermediate portion of the CCD 63 to the terminal 66 through the amplifier 65. When the reproduction signal is the PAL system, C
A delay signal having a delay time corresponding to two horizontal periods is extracted from the terminal end of the CD 63 to the terminal 68 through the amplifier 67.

Further, the signal from the terminal 66 is supplied to the low pass filter 21. Further, the signal from the terminal 66 and the signal from the terminal 68 are selected (NTSC method → N, PAL method → P) by the switch 22 according to the method of the reproduction signal, and the selected signal is passed through the low pass filter 23, for example, the amplifier 67. Is supplied to the equalizer circuit 24 for compensating for the delay amount.

The signal from the equalizer circuit 24 and the signal from the low-pass filter 21 are selected by the switch 25 according to the reproduction signal system (NTSC system → N, PAL system →
P). Then, the selected signal is supplied to the adder 53 through the terminal 56. In addition, the equalizer circuit 24
Is supplied to the subtractor 54 through the terminal 57.

As a result, the adder 53 is supplied with a delay signal having a delay time corresponding to one horizontal period, the dropout compensation of the luminance signal is performed, and the signal is taken out to the terminal 58. When the reproduction signal is the NTSC system, a delay signal having a delay time corresponding to one horizontal period is supplied to the subtractor 54, and the chroma signal from which crosstalk has been removed is taken out to the terminal 59. On the other hand, when the reproduction signal is of the PAL system, a delay signal having a delay time corresponding to two horizontal periods is supplied to the subtractor 54, and the crosstalk-removed chroma signal is taken out to the terminal 59.

Further, the luminance signal taken out at the terminal 58 is supplied to the noise canceller circuit 8. Further, the chroma signal taken out to the terminal 59 is supplied to the de-emphasis circuit 9. Then, the noise-cancelled luminance signal and the de-emphasized chroma signal are supplied to the adder 10, and the added composite video signal is taken out to the output terminal 11.

That is, in this device, the reproduction signal is P
In the case of the AL method, a delay signal having a delay time corresponding to two horizontal periods is taken out through the amplifier 67. Then, the equalizer circuit 24 compensates the delay amount of the amplifier 67 and supplies it to the subtractor 54.

On the other hand, when the reproduced signal is of the NTSC system, a delay signal having a delay time corresponding to one horizontal period is taken out through the amplifier 66. Here, the amplifier 66,
67 is a circuit formed on the same IC 60, and its delay amount is substantially the same. Therefore, the signal extracted through the amplifier 66 is compensated for the delay amount by the equalizer circuit 24, so that the subtractor 54 is supplied with the signal whose delay amount is compensated as in the case of the PAL system.

In this way, according to the above-mentioned device, the equalizer circuit to be adjusted is only one place (24), and it is possible to solve the problems such as the increase of the manufacturing cost due to the increase of the adjustment places and the increase of the unstable elements. It is possible.

In the above-mentioned device, the dropout compensation of the luminance signal has no problem even if there is some delay error, and the compensation of the delay amount is extremely important for removing the crosstalk of the chroma signal. Therefore, in the above-mentioned device, the output of the low-pass filter 21 may be always supplied to the terminal 56 except for the switch 25.

In the above-mentioned device, for example, NTSC
When the color sub-carrier frequency of the method is converted to 4.43 MHz in the high frequency range, the phase of the color sub-carrier signal is not inverted every horizontal period. That is, 4.43 MHz becomes 281.783 waves in one horizontal period (63.556 μs) of the NTSC system. Therefore, in order to eliminate the 0.783 wave and to make the phase invert every horizontal period, the operation clock frequency of the CCD 63 is set to 4.
It may be 470593 MHz.

As a result, for example, the CCD 63 has 4.4
When the operation clock of 33619MHz is supplied,
From the 1699th stage, a delay signal having a delay time corresponding to two horizontal periods of the PAL system is extracted. When an operating clock of 4.470593 MHz is supplied to the CCD 63, a delay signal having a delay time corresponding to one horizontal period of the NTSC system is extracted from the 848th stage.

Further, the means for performing the corresponding delay by using the clock signal is not limited to the above-mentioned CCD, but the signal may be digitized and the shift register may be used.

[0029]

According to the present invention, the number of equalizer circuits to be adjusted is only one, and it is possible to solve problems such as an increase in manufacturing cost due to an increase in adjustment points and an increase in unstable elements. became.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of a comb filter according to the present invention.

FIG. 2 is a configuration diagram of a conventional comb filter.

[Explanation of symbols]

 1 magnetic tape 2 head 3 reproduction amplifier 4 demodulation circuit 5, 9 de-emphasis circuit 6 frequency conversion circuit 7, 10 adder 8 noise canceller circuit 11 output terminal 21, 23 low-pass filter 22, 25 switch 24 equalizer circuit 50 arithmetic IC 51, 55 , 56, 57, 58, 59 terminal 52 amplifier 53 adder 54 subtractor 60 delay IC 61, 64, 66, 68 terminal 62, 65, 67 amplifier 63 CCD 71, 72 clock terminal 73 switch

Claims (1)

[Claims] 1. A reproduction signal is supplied, a corresponding delay is performed using a clock signal, and a first delay of a delay time corresponding to one horizontal period of the first television system is performed through the first output means. A delay circuit for taking out a signal and taking out a second delayed signal having a delay time corresponding to two horizontal periods of the second television system through the second output means, and the first and second delayed signals And the switched signal is combined with the original reproduced signal through an equalizer circuit that compensates for the delay amount of either one of the first and second output means, and at least the chroma signal in the reproduced signal is combined. A comb filter that allows crosstalk removal of signals.