JPS62250785A - Pal video signal separating device - Google Patents

Abstract

PURPOSE:To obtain a separated brightness signal whose signal components of frequencies between the frequencies integer-times of the half of the horizontal frequency within a prescribed band is emphasized by constituting the circuitry in a simple constitution requiring no special delay circuits other than a delay circuit for the signal- separation. CONSTITUTION:An input video signal Vi is supplied to a delay circuit 21 and delayed for two times of horizontal frequency. An output signal from the delay circuit 21 is subtracted from the input video signal Vi, an output signal from an subtraction circuit 22 is supplied to an attenuator circuit 23 where it is attenuated to the half, and an output signal from the attenuator circuit 23 is conducted to an output terminal 20c. Also, the output signal from the attenuator circuit 23 is subtracted from the input video signal Vi, and an output signal from a substraction circuit 24 is conducted to an output terminal 20y. Therefore, assuming the horizontal frequency of the input video signal Vi to be fH and the subc arrier wave frequency of the same to be fsc, the frequency characteristic between a video signal input terminal 10 and the output terminal 20c forms troughs of minimum gain at the frequencies integer-times of the half of the horizontal frequency through entire carrier color signal band and the lower side band.

Description

[Detailed description of the invention] Zero to light will be explained in the following order.

'A Industrial application field B Summary of the invention C Prior art D Problem to be solved by the invention E Means for solving the problem F Effect G Embodiment G-1 Configuration and operation (Fig. 1, Figure 2) G-2 Modification 11 Effect of the Invention A Industrial Field of Application The present invention is provided in a recording system of a video tape recorder for recording and reproducing PAL video signals, and is used to extract luminance signals and carrier color signals from PAL video signals. The present invention relates to a PAL video signal separation device.

B. Invention 1 Existing Summary The present invention provides a PAL video signal separation device for separating a luminance signal and a carrier color signal from a PAL video signal, which is installed in a recording system of a video tape recorder that records and plays back a PAL video signal. between the video signal input terminal and the first output terminal; a signal separation unit that includes the delay circuit to configure a subtractive comb filter, and includes the delay circuit between the video signal input terminal and a second output terminal to configure an additive comb filter; A predetermined band on the lower side of the carrier color signal band, or a part or all of this predetermined band and its high band side, of the video signal before and after the delay time portion corresponding to one horizontal period of the part of the delay circuit. a signal extraction unit that subtracts signal components in a band of at least the predetermined band and the signal obtained from the first output terminal and the signal obtained from the signal extraction unit, respectively, on the low frequency side of the carrier color signal band; By providing a signal addition section that adds the signal components of the entire low frequency band to the signal obtained at the second output terminal, a special delay circuit is not required in addition to the delay circuit for signal separation. With a simple circuit configuration that does not require
This is so that signal components of frequencies between frequencies that are integral multiples of are enhanced.

C. Prior Art In the recording system of a video tape recorder that records and plays PAL video signals, a luminance signal and a carrier color signal are separated from the video signal obtained by receiving television broadcasting, etc., and the luminance signal is frequency-modulated and The color signal is low frequency converted, and the frequency modulated luminance signal and the low frequency converted carrier color signal are combined and recorded on a magnetic tape by a rotating magnetic head. In this case, the luminance signal and the carrier color signal are combined. A comb filter is used for separation.

That is, in a band including a delay circuit that delays the input video signal by two horizontal periods, the gain is minimum in a band lower than the carrier color signal band of the input video signal, and in the carrier color signal band of the input video signal, The gain is minimum at a frequency that is an integral multiple of 172 of the horizontal frequency.

A filter circuit with a frequency characteristic having a comb-shaped characteristic is constructed, which forms a valley with a gain of OdB at a frequency that is an odd multiple of 174 of the horizontal frequency, and from this a carrier color signal is obtained. Including the above-described delay circuit, the gain has a flat characteristic of OdB in the lower band of the wL transmission signal band of the input video signal, and in the carrier color signal band of the input video signal, the gain is 172 dB of the horizontal frequency. The gain forms a peak of OdB at a frequency that is an integer multiple of the horizontal frequency.
A filter circuit with a frequency characteristic having a comb-like characteristic in which a valley with a minimum gain is formed at a frequency that is an odd number multiple of 74 is constructed, and a luminance signal is obtained from this filter circuit.

D Problems to be Solved by the Invention Incidentally, in the playback system of a video tape recorder that records and plays back PAL video signals, the frequency-modulated luminance signal and the frequency-modulated brightness signal played back from the magnetic tape by a rotating magnetic head are low-frequency converted. A high-pass filter and a low-pass filter separate a frequency-modulated luminance signal and a low-pass-converted carrier chrominance signal from the carrier color signal composite signal, and demodulate the luminance signal from the frequency-modulated luminance signal. , the carrier color signal subjected to low frequency conversion is converted to the original frequency, and the demodulated luminance signal and the carrier color signal changed to the original frequency are combined and output to the reproduced video signal output terminal. This reproduced video signal is then supplied to a television receiver to obtain a reproduced image, but even in the television receiver, a luminance signal and a carrier color signal are separated from the reproduced video signal by a comb filter.

In other words, a television receiver that reproduces a PAL video signal includes a delay circuit that delays the reproduced video signal by two horizontal periods, and forms a valley with minimum gain at a frequency that is an integral multiple of 172 of the horizontal frequency. A subtractive comb filter whose frequency characteristic forms a maximum peak at an odd multiple of 1/4 of the frequency is constructed, and a carrier color signal is obtained from this. No. 1
An additive comb filter is constructed with a frequency characteristic that forms peaks with maximum gain at frequencies that are an integer multiple of /2 and valleys that have minimum gain at frequencies that are odd multiples of 174 of the horizontal frequency. A luminance signal is obtained.

Therefore, as mentioned above, the filter circuit for luminance signal separation provided in the recording system of a video tape recorder that records and reproduces PAL video signals has a constant gain in the band below the carrier chrominance signal band of the input video signal. If the luminance signal obtained from this filter circuit has a constant gain in a band lower than the carrier chrominance signal band of the input video signal, the above additive comb type is used in the television receiver. The filter attenuates signal components of frequencies between frequencies that are integral multiples of 172 of the horizontal frequency in the luminance signal, especially signal components that have frequencies that are odd multiples of 1/4 of the horizontal frequency, thereby reducing the quality of the reproduced image. to degrade.

Therefore, in consideration of this attenuation in the television receiver, in the recording system of the video tape recorder, signal components of frequencies between frequencies that are integral multiples of 172 of the horizontal frequency within a predetermined band are enhanced as luminance signals. It is desirable to be able to obtain something.

However, for this reason, when a delay circuit is provided separately from the delay circuit for signal separation, there is an inconvenience that the cost of the device increases significantly.

In view of this point, the present invention uses a simple circuit configuration that does not require a special delay circuit other than a delay circuit for signal separation, and uses a simple circuit configuration that does not require a special delay circuit other than a delay circuit for signal separation. This is so that signal components with frequencies between the frequencies of 2 and 2 are enhanced.

E. Means for Solving the Problems The present invention includes a delay circuit that delays the input video signal supplied to the video signal input terminal by 2 horizontal periods over the entire carrier color signal band and its lower band. death,
The delay circuit is included between the video signal input terminal and the first output terminal to constitute a subtractive comb filter, and the delay circuit is included between the video signal input terminal and the second output terminal. a signal separation unit that constitutes an additive comb filter, and a predetermined band on the lower side of the carrier color signal band of the video signal before and after the delay time portion of one horizontal period of the part of the delay circuit; , or a signal extraction section that subtracts signal components of the predetermined band and a part or all of the high frequency band thereof, and a signal obtained at the first output terminal and a signal obtained from the signal extraction section, respectively. The signal components of at least the predetermined band on the low band side of the carrier color signal band and the entire band on the low band side are
A signal adding section is provided for adding signals obtained at the output terminal of the signal adding section.

F action In the PAL video signal separation device according to the present invention configured as described above, the frequency characteristic between the video signal input terminal and the first output terminal of the signal separation section is equal to the carrier color signal of the input video signal. In the band and all bands on the lower side thereof, a valley where the gain is minimum is formed at a frequency that is an integer multiple of 172 of the horizontal frequency, and a valley where the gain is O is formed at a frequency that is an odd multiple of 174 of the horizontal frequency.
The frequency characteristic between the video signal input terminal and the second output terminal of the signal separation section is a comb-shaped characteristic that forms a peak of dB, and the frequency characteristic between the video signal input terminal and the second output terminal of the signal separation section is the carrier color signal band of the input video signal and the entire band on the lower side thereof. In this case, the gain forms a peak of O dB at a frequency that is an integer multiple of 1/2 of the horizontal frequency, and a trough with the minimum gain forms at a frequency that is an odd multiple of 1/4 of the horizontal frequency, resulting in a comb-shaped characteristic. The frequency characteristics between the signal input 0:;; and the output terminal of the signal extraction section are such that in a predetermined band lower than the carrier color signal band of the input video signal, the gain is set at a frequency that is an integral multiple of the horizontal frequency. 1 of the horizontal frequency, forming the smallest valley
The frequency characteristic between the video signal input terminal and the output terminal of the signal adder is a comb-shaped characteristic that forms a peak of gain that is sufficiently larger than the minimum gain at a frequency that is an odd multiple of /2. In a predetermined band on the lower side of the color signal band, a waveform in which a valley with a gain of OdB is formed at a frequency that is an integer multiple of the horizontal frequency, and a peak where the gain is larger than OdB is formed at a frequency that is an odd multiple of 172 of the horizontal frequency. The characteristics are as follows, and a luminance signal in which signal components of frequencies between frequencies that are integral multiples of the horizontal frequency within a predetermined band are enhanced is obtained at the output terminal of the signal adder.

G Example G-1 Configuration and Operation (FIGS. 1 and 2) FIG. 1 shows an example of a PAL video signal separation device according to the present invention.

The input video signal Vi, which is a PAL video signal, is supplied to the video signal input terminal 10 and is supplied to a signal separation section 20 having a delay circuit 21 . The delay circuit 21 delays the input video signal Vi by 2 horizontal periods over the entire carrier color signal band and its lower band, and the delay circuit 21 delays the input video signal Vi by 2 horizontal periods over the entire carrier color signal band and its lower band, and has a delay time of 1 horizontal period at the front stage 21F and at the rear stage 21R, respectively.
Consists of. The signal separation unit 20 includes a delay circuit 21 and configures a subtractive comb filter between the video signal input terminal 10 and the output terminal 20c, and also includes the delay circuit 21 and configures a subtractive comb filter between the video signal input terminal 10 and the output terminal 20y. An additive comb filter is constructed in between.

That is, the input video signal Vi is supplied to the delay circuit 21 and delayed by two horizontal periods as described above, the output signal of the delay circuit 21 is subtracted from the input video signal Vi in the subtraction circuit 22, and the output signal of the subtraction circuit 22 is The output signal of the attenuation circuit 23 is supplied to the attenuation circuit 23 and attenuated to 1/2, and the output signal of the attenuation circuit 23 is led out to the output terminal 20c.The output signal of the attenuation circuit 23 is subtracted from the input video signal Vi in the subtraction circuit 24. An output signal of is derived to the output terminal 20y.

Therefore, if the horizontal frequency of the input video signal Vi is fo and the subcarrier frequency is f3C, the frequency characteristic between the video signal input terminal 10 and the output terminal 20c is as shown in the top row of FIG. In the carrier chrominance signal band of the signal Vi and all bands on the lower side thereof, a valley with minimum gain is formed at a frequency that is an integer multiple of 1/2 of the horizontal frequency, and a valley that is an odd multiple of 1/4 of the horizontal frequency is formed. As shown in the second row of FIG. 2, the frequency characteristic between the video signal input terminal 10 and the output terminal 20y is the carrier color of the input video signal Vi. In the signal band and all bands on the lower side thereof, the gain forms a peak of OdB at a frequency that is an integral multiple of 1/2 of the horizontal frequency, and the gain is 174 dB above the horizontal frequency.
This results in a comb-shaped characteristic in which a valley with minimum gain is formed at frequencies that are odd multiples of . Therefore, the signal c obtained at the output terminal 20c
y is a carrier color signal containing a luminance signal component, and the signal Yc obtained at the output terminal 20y is a luminance signal containing a carrier color signal component. However, the luminance signal obtained at the output terminal 20y has attenuated signal components with frequencies between frequencies that are integral multiples of 1/2 of the horizontal frequency, especially signal components with frequencies that are odd multiples of 1/4 of the horizontal frequency. It is.

In this example, the band below the carrier color signal band of the input video signal Vi is a low band of 0 to IMHz, a middle band of 1 to 2MHz, and a frequency fL from 2 MHz to the lower limit of the carrier color signal band. It is divided into high range up to 1~2 MH
In the case where a luminance signal is obtained in which signal components of frequencies between frequencies that are an integer multiple of the horizontal frequency in the midrange of z are enhanced, nfo is a certain integer multiple of the horizontal frequency in the center of the midrange. frequency.

For the video signal input terminal 10, there is provided a signal extraction section 30 that includes the front section 21F of the delay circuit 21 and constitutes a subtractive comb filter for the middle range of 1 to 2 M)-1z. That is, in the subtraction circuit 31, the signal obtained at the connection point between the front stage section 21F and the rear stage section 21R of the delay circuit 21 is subtracted from the input video No. 18 Vi, and the output signal of the subtraction circuit 31 is transmitted through the output terminal 32 at a frequency of 1 to 2 MHz. The output signal of the band pass filter 33 is supplied to the attenuation circuit 34 and attenuated to 1/A, and the output signal of the attenuation circuit 34 is led out to the output terminal 35. be done. A is made to be a number greater than 2, but not very large.

Therefore, the frequency characteristics between the video signal input terminal 10 and the output terminal 32 are as shown by the broken line in the third row of FIG. The output terminal 32 has a comb-shaped characteristic in which a valley where the gain is minimum is formed at a frequency that is an integer multiple of the horizontal frequency, and a peak where the gain is larger than OdB is formed at a frequency that is an odd multiple of 172 of the horizontal frequency. A non-vertical correlation component of the signal is obtained, and the frequency characteristic between the video signal input terminal 10 and the output terminal 35 is 0'' as shown by the solid line in the third stage of FIG.
The gain is minimum in the I MHz low band, 2 MHz x fL high band, and carrier color signal band, and 1 to 2 MHz
In the midrange, a valley with minimum gain is formed at a frequency that is an integer multiple of the horizontal frequency, and a peak of gain that is smaller than OdB but sufficiently larger than the minimum gain is formed at a frequency that is an odd multiple of 172 of the horizontal frequency. , it becomes a comb-shaped characteristic, and output terminal 3
5, brightness signal components of frequencies between frequencies that are integral multiples of the horizontal frequency in the midrange of 1 to 2 MHz are obtained.

Then, in the signal addition section 40, the signal cy obtained at the output terminal 20c of the signal separation section 20 and the signal Yn obtained at the output terminal 35 of the signal extraction section 30 are adjusted to 0 to IM, respectively.
The signal components in the low range of IIz and the middle range of 1 to 2 MHz are added to the signal Yc obtained at the output terminal 20y of the signal separation section 20, and the output signal of the signal addition section 40 is added to the luminance signal output terminal 50. is derived. That is, in the adder circuit 41, the signal cy obtained at the output terminal 20c and the signal Yn obtained at the output terminal 35 are added, and the adder circuit 41
The output signal of the carrier color signal band and the two
The output signal of the band attenuation filter 43 is supplied to the output terminal 44, and the signal Yc obtained at the output terminal 20y and the output terminal 44 are supplied to the adder circuit 45. The signal Ye obtained from the addition circuit 45 is added, and the output signal of the addition circuit 45 is derived to the luminance signal output terminal 50.

Therefore, the frequency characteristics between the video signal input terminal 10 and the output terminal 44 range from 0 to I M as shown in the fourth row of FIG.
In the low frequency range of Hz, a valley with minimum gain is formed at a frequency that is an integer multiple of 172 of the horizontal frequency;
The gain forms a peak of OdB at frequencies that are odd multiples of 4, (
It has a rectangular characteristic, and in the midrange of 1 to 2 MHz, the gain forms a valley where it is minimum at frequencies that are integral multiples of the horizontal frequency.
A gain valley is formed at odd multiples of 172 of the horizontal frequency, which is smaller than 0dll but sufficiently larger than the minimum gain, and the gain is OdB at frequencies that are odd multiples of 174 of the horizontal frequency.
It becomes a comb-shaped characteristic that forms larger mountains, and 2MII
In the high range of zxfL and the carrier color signal band, the gain is minimum, and the output terminal 44 has the low range of θ to IMH2 and 1
An enhanced luminance signal component is obtained in the midrange of 1 to 2 MHz, which is between frequencies that are integral multiples of 172 of the horizontal frequency in the midrange of ~2 MHz. As shown in the bottom row of FIG. 2, the frequency characteristic between the signal output terminals 50 is a flat characteristic with a gain of OdB in the low frequency range of 0 to IMHz,
In the mid-MHz range, the waveform has a trough with a gain of OdB at frequencies that are integral multiples of the horizontal frequency, and a peak where the gain is larger than OdB at frequencies that are odd multiples of 1/2 of the horizontal frequency. In the high frequency range of 2 MHz-f L and the carrier color signal band, the gain forms a peak of OdB at a frequency that is an integral multiple of 1/2 of the horizontal frequency, and
The luminance signal output terminal 50 has a comb-shaped characteristic in which a valley with minimum gain is formed at frequencies that are odd multiples of .
A brightness signal Yo is obtained in which signal components of frequencies between frequencies that are integral multiples of the horizontal frequency in the Hz midrange are enhanced.

Note that the signal cy obtained at the output terminal 20c of the signal separation section 20 is supplied to a bandpass filter 60 whose pass band is the carrier color signal band, and the output signal of the bandpass filter 60 is led out to the carrier color signal output terminal 70. Ru.

Therefore, the video signal input terminal 10 and the carrier color signal output terminal 7
Although the frequency characteristics between zero and forms the smallest valley, 1/4 of the horizontal frequency
A comb-shaped characteristic is obtained in which the gain forms a peak of O dB at frequencies that are odd multiples of , and a carrier color signal CO is obtained at the carrier color signal output terminal 70.

G-2 Modified Example In the above example, the band attenuation filter 4 of the signal adder 40
3 traps the carrier color signal band and the high frequency range of 2 MHZ% fL, so in the signal extracting section 30,
A bandpass filter 33 whose passband is a 2MHz middle range.
Instead, a band-pass filter or a high-pass filter may be provided whose pass band is a middle band of 1 to 2 MHz and part or all of the band on the high side thereof. Further, in the signal addition section 40, the carrier color signal band and the 2 MH
Instead of the band attenuation filter 43 that traps the high frequency range of z w f L, a low pass filter may be provided whose passband is a low frequency range of 0 to IM Hz and a middle frequency range of 1 to 2 MHz.

Furthermore, for example, the low-pass filter provided in the signal addition section 40 is configured to have a pass band of the above-mentioned low band of 0 to IMH2, middle band of 1 to 2 MHz, and high band of 2 MHz-fL. , video signal input terminal 10 and output terminal 44
The frequency response between 0 and 2 MHz is 1/1 of the horizontal frequency in the high range from 2 MHz to 1 MHz, as well as the low range from 0 to IMHz.
A comb-shaped characteristic is formed in which a valley with a minimum gain is formed at a frequency that is an integer multiple of 2, and a peak where the gain is O dB is formed at a frequency that is an odd multiple of 1/4 of the horizontal frequency, and the video signal input terminal 10 and the luminance signal The frequency characteristic between the output terminals 50 is 2 MHz
Similarly to the low range of θ to IMHz, the gain may have a flat characteristic of O dB in the high range of -f.

Effects of the Invention According to the present invention, in a PAL video signal distribution device that is installed in a recording system of a video tape recorder that records and plays back a PAL video signal and separates a luminance signal and a carrier color signal from a PAL video signal, the signal separation With a simple circuit configuration that does not require any special delay circuit other than the delay circuit for
This results in enhanced signal components at frequencies between frequencies that are integral multiples of .

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing an example of a PAL video signal separation device according to the present invention, and FIG. 2 is a diagram showing frequency characteristics of each part thereof. In the figure, 10 is a video signal input terminal, 20 is a signal separation section, 2
I is a delay circuit, 20C is the first output terminal, 20y is the second
, 30 is a signal extraction section, and 40 is a signal addition section.

Claims (1)

[Scope of Claims] A delay circuit that delays an input video signal supplied to the video signal input terminal by two horizontal periods over its carrier color signal band and its entire lower frequency band; The delay circuit is included between the first output terminal and the subtractive comb filter, and the delay circuit is included between the video signal input terminal and the second output terminal to form an additive comb filter. a signal separation unit constituting a filter, and a predetermined band on the lower side of the carrier color signal band of the video signal before and after the delay time portion of one horizontal period of the part of the delay circuit, or this predetermined band and a signal extractor that subtracts signal components in part or all of the band on the high frequency side; A PAL video signal separation device comprising: a signal adding section that adds signal components of at least the predetermined band on the low frequency side and the entire band on the low frequency side to the signal obtained at the second output terminal.