JPH01883A - Color video signal forming circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a color video signal forming circuit.

[Summary of the invention]

In a color video signal forming circuit, the present invention provides a luminance signal transmission path with means for separating signal components in the frequency band of a carrier color signal and an IH comb filter, so that the luminance signal can be transmitted without impairing the luminance signal band. and interference between color signals is prevented.

[Conventional technology]

In conventional video tape recorders (VTRs), when recording and reproducing color video signals, the recording system separates the luminance signal Y and the carrier color signal C and records them on magnetic tape, and the reproduction system separates the luminance signal Y and the carrier color signal C and records them on the magnetic tape. A color video signal is obtained by mixing (adding) the general feed color signal and the general feed color signal.

[Problem that the invention seeks to solve]

However, in the conventional VTR as mentioned above, the luminance signal Y
When the frequency band of the carrier color signal is wide, there is a problem that interference occurs between the signal component of the frequency band of the carrier color signal and the carrier color signal.

For example, when recording and reproducing color video signals, if the Y/C separation circuit in the recording system uses line correlation, the uncorrelated component CNS of the carrier color signal C may remain in the luminance signal system. This uncorrelated component is reproduced in both the luminance signal system and the color signal system, but only in the color reproduction system is automatic phase control (A
PC) processing, the phases of the uncorrelated component CSS of the carrier color signal reproduced in both signal systems do not match, and zero beat interference occurs when the luminance signal Y and carrier color signal C are added. .

In addition, the high-frequency component of the luminance signal Y mixes into the carrier color signal system, causing so-called cross-color interference in which incorrect colors appear in, for example, vertical stripes in the reproduced image.

In view of the above, an object of the present invention is to provide a color video signal forming circuit that can prevent interference between a wideband luminance signal and a carrier color signal and improve the quality of reproduced images.

[Means for solving problems]

The present invention provides a color video signal forming circuit that adds a luminance signal and a carrier color signal to form a color video signal, and includes a separation means for separating signal components in a frequency band of the carrier color signal, and a one-horizontal period delay line. This is a color video signal forming circuit in which a comb-shaped filter including a comb-shaped filter is provided in a luminance signal transmission path.

[Effect]

According to this configuration, interference between the carrier color signal and the broadband luminance signal is prevented.

〔Example〕

Hereinafter, an embodiment of a color video signal forming circuit according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows the configuration of an embodiment of the present invention.

In FIG. 1, (1) and (2) are input terminals to which a luminance signal Y and a carrier color signal C are respectively supplied, and an input terminal (2) is directly connected to an adder (3), and an adder W- Vessel (3
) is led out to the output terminal (4). input terminal fi
The luminance signal Y of l is passed through the delay line (11) and the bandpass filter (1
2), and in a subtracter (13), the output of the bandpass filter (12) is subtracted from the output of the delay line (11). The passband of the filter (12) is the carrier color signal C
The delay time τ of the delay line (12) is set equal to the delay time of the bandpass filter (2). The output of the subtracter (13) is sent to the second adder (5)
is supplied to the adder (3) via.

(20) is an additive comb filter, and the delay line (2
1) and an adder (22), and a delay line (21)
The delay time is set to one horizontal period (IH). The output of the bandpass filter (12) is directly supplied to the adder (22) and is also supplied to the adder (22) via the IH delay line (21).
). The output of the adder (22) has its amplitude halved by a coefficient multiplier (attenuator) (25) and is supplied to the adder (5).

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIG. 2 as well.

As shown in FIG. 2A, when a luminance signal Y having a wide frequency spectrum up to a frequency fw (e.g. 5 M)lz) which is significantly above the color subcarrier frequency fsc is supplied to the input terminal +1). , as shown in Figure B, f
With sC as the center, signal components having the same frequency spectrum as the frequency spectrum (2) of the carrier color signal C having a bandwidth of, for example, ±0.5 MHz are separated by a bandpass filter (12). In the subtracter (13), this separated signal component (spectrum) is converted into the input luminance signal (spectrum).
The output of the subtracter (13) becomes a partially deleted spectrum ◎ in which the portion of the carrier color signal band ■ is deleted, as shown in FIG.

By the way, as shown in the second diagram, the additive comb filter (20) has an attenuation range of f SC±n-fH, where n is an integer, and r sc±(2n-1)-f H/2.
becomes the pass area.

As is well known, in the NTSC system, the color subcarrier frequency f
SC is selected to be an odd multiple of 1/2 of the horizontal scanning frequency r, and frequency interleaving is performed between the luminance signal Y, whose energy is concentrated near frequencies that are integral multiples of f, and the carrier color signal C. . If fSC is selected in this way, when the carrier color signal C is delayed by IH, its phase is reversed and cancelled.

The comb-shaped filter (20) with the characteristics described above is
When a luminance signal with a frequency spectrum ■ as shown in the figure is supplied from the bandpass filter (12), the output of the coefficient multiplier (25) is microscopically a comb-shaped spectrum as shown by expanding the frequency axis in the same figure. ■It becomes. Moreover, the frequency band of the envelope is limited as shown in FIG.

The output of the band-limited comb-shaped spectrum ■ of the coefficient unit (25) and the output of the partially deleted spectrum ◎ of the subtractor (13) are combined in the second adder (5).
) is a partial comb-shaped spectrum ■, in which the deleted portion of the partially deleted spectrum ◎ is supplemented with a band-limited comb-shaped spectrum ■, as conceptually shown in FIG.

According to this embodiment, the carrier color signal component C without line correlation
Even if NS is mixed into the luminance signal Y of the input terminal fl),
Since it is separated by a bandpass filter (12) and a subtracter (step 3) and removed by a comb filter (20) having the characteristics described above, zero beat interference does not occur between the uncorrelated components of the color signal system.

In addition, this comb filter (20) limits the spread of the energy spectrum of the components in the frequency band of the carrier color signal in the luminance signal Y, so even if the high-frequency components of the luminance signal Y are at a high level, the cross Color interference is suppressed.

Note that since the comb filter (20) basically passes the entire spectrum of the luminance signal Y, the horizontal resolution is not impaired.

Next, another embodiment of the color video signal forming circuit according to the present invention will be described with reference to FIGS. 3 and 4.

The structure of another embodiment of the present invention is shown in FIG. In FIG. 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals and redundant explanation will be omitted.

In FIG. 3, the luminance signal Y at the input terminal (1) is passed through a band-stop filter (trap> (14) and a subtracter (15).
), and the output of the trap (14) is subtracted from the luminance signal Y in a subtracter (15). The center frequency of the trap (14) is set equal to "sc".

The output of the trap (14) is directly supplied to the second adder (5), and the output of the subtracter (15) is supplied to the second adder (5) via a comb filter (20) and a coefficient unit (25). It is supplied to an adder (5). The rest of the configuration is the same as that shown in FIG. 1 above.

The operation of the embodiment of FIG. 3 is as follows.

Of the broadband luminance signal Y supplied to the input terminal (1), the signal component centered at fSO is attenuated by the trap (14), and the output of the trap (14) is as shown in FIG.
As shown in , it becomes a partially deleted spectrum in which the neighborhood of r sc is deleted in a seven-figure shape. Trap like this (14)
The output of the subtracter (15) is subtracted from the broadband luminance signal Y from the input terminal (1) in the subtracter (15), and although not shown, the output of the subtracter (15) is an inverse V centered on fSO.
It becomes a letter-shaped spectrum.

The output of the subtracter (15) is supplied to a comb-shaped filter (20) with frequency characteristics as shown in the second diagram above, and a coefficient multiplier (
25) is a band-limited comb-shaped spectrum (not shown) having an inverted V-shaped envelope in the same way as described above.

The output of the band-limited comb-shaped spectrum of the coefficient unit (25) and the output of the partially deleted spectrum (■) of the trap (14) are combined in the second adder (5).
) is a partial comb-shaped spectrum (2) in which the missing portion of the partially deleted spectrum (2) is supplemented with a band-limited comb-shaped spectrum, as conceptually shown in FIG.

The embodiment shown in FIG. 3 has the same functions and effects as the embodiment shown in FIG.

Although the attenuation range due to the trap (14) is narrow, the energy spectrum of the carrier color signal is macroscopically r sc
There is no particular problem as the area is concentrated in the vicinity of .

In the embodiment shown in FIG. 3, a specific configuration of the transmission path for the luminance signal Y is shown in FIG. In FIG. 5, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and redundant explanation will be omitted.

In Fig. 5, an input resistor (14r), a capacitor (14c), and a coil (li) are connected in series to constitute a trap (14), and the luminance signal Y from the input terminal (11) is transmitted to the resistor (14r). ) to the base of the transistor (31) whose collector is connected to ground, and is further supplied to the capacitor (14c) & coil (1, [
is supplied to the emitter of a transistor (32) connected to the common base. The output of this transistor (32) is supplied to the base of a third transistor (33) whose collector is connected to ground.

The emitter output of the transistor (3I) is connected to the resistor (34
), the fourth transistor (3
5). Third transistor (3
3) is connected to the fourth emitter output via a resistor (36).
is supplied to the emitter of the transistor (35), and the lH delay line (2I
) and the transistor (35) via the resistor (37)
is supplied to the emitter of

The collector output of this transistor (35) is the terminal (6)
is derived. (7) is a power supply terminal.

The operation of the circuit shown in FIG. 5 is as follows.

Since the series resonance frequency of the capacitor (14c) and the coil (14j) is set to rsc, and the input resistance of the transistor (32) is small, the input of the transistor (31),
Therefore, the output is a partially deleted spectrum as shown in FIG. 4A above. On the other hand, the transistor (32
) is the emitter input of f! ? It has an inverted V-shaped spectrum centered at c, which is appropriately amplified and output from the emitter of the transistor (33) at the same level as the emitter output of the transistor (31).

Resistance values of resistors (34), (36), (37) R34°R3g and R3? When setting 2R34=R3ε8R37, the sum of currents supplied from the input and output sides of the IH delay line (21) to the emitter of the transistor (35) is the sum of the currents supplied from the transistor (31) to the emitter of the transistor (35). The emitter input of the transistor (35) is at the same level as the current supplied to the fourth transistor (35).
As shown in FIG. B, a partial comb-shaped spectrum (2) is obtained in which the missing portion is supplemented by the band-limited comb-shaped spectrum.

Next, still another embodiment of the color video signal forming circuit according to the present invention will be described with reference to FIGS. 6 and 7.

The structure of yet another embodiment of the present invention is shown in FIG.

In FIG. 6, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 6, the luminance signal Y of the input terminal (11) is commonly supplied to the delay line (11) and the bandpass filter (12),
The output of the delay line (11) is supplied to a subtracter (16).

The passband of the filter (12) is set equal to the frequency band of the carrier color signal C, and the delay time τ of the delay line (12) is set equal to the delay time of the bandpass filter (12). The output of the subtracter (16) is supplied to the adder (3).

(20S) is a subtractive comb filter, which is composed of a delay line (21) and a subtracter (23).
The delay time in 1) is set to one horizontal period (IH). The output of the bandpass filter (12) is directly supplied to the subtractor (23) and IHi! ! It is supplied to a subtractor (23) via a wire extension (21). The output of the subtracter (23) has its amplitude halved by the coefficient multiplier (R, device) (2°5) and is supplied to the subtracter (16).

Next, the operation of the embodiment shown in FIG. 6 will be explained with reference to FIG. 7 as well.

As shown in FIG. 7A, when a luminance signal Y having a wide frequency spectrum up to a frequency fu (for example 5 Mllz) significantly above the color subcarrier frequency fSO is applied to the input terminal (11), the same r s as shown in Figure B
A signal component having the same frequency spectrum as the frequency spectrum (2) of the carrier color signal C having a bandwidth of, for example, ±0.5 MIIz is separated by a bandpass filter (12) with c as the center. By the way, as shown in FIG. 7C, the subtractive comb filter (205) is opposite to the above-mentioned additive comb filter (20), where n is an integer and fs is thn-.
fH becomes the passband, and the intermediate f SC (2n
1) fs/2 becomes the MW region.

A comb-shaped filter (20S) with the characteristics described above is
When a luminance signal with a frequency spectrum ■ as shown in Figure C is supplied from the bandpass filter (12), the output of the coefficient multiplier (25) has a comb-like shape as shown in Figure C with the frequency axis expanded. The spectrum becomes ◎. Further, the frequency band of the envelope is limited as shown in the same figure.

The output of the band-limited comb-shaped spectrum ◎ of this coefficient unit (25) is subtracted from the output of the broadband spectrum ■ of the delay line (11) in the subtracter (16), resulting in a subtraction of ``5 (16).
As conceptually shown in the figure, the output becomes a partial comb-shaped spectrum ■ in which the carrier color signal frequency band of the broadband spectrum ■ is replaced by a band-limited comb-shaped spectrum ◎ whose polarity is inverted.

The embodiment shown in FIG. 6 also has the same effect as the embodiment shown in FIG. 1 described above.

As is clear from Figure 7, in the embodiment shown in Figure 6, the width of the micro spectrum of the carrier color signal band is narrower, but instead of the comb filter (20S), a feedback comb filter is used. By using , the width of the micro spectrum can be expanded.

Next, still another embodiment of the color video signal forming circuit according to the present invention will be described with reference to FIGS. 8 and 9.

The configuration of still another embodiment of the present invention is shown in FIG.

In FIG. 8, parts corresponding to those in FIGS. 1 and 3 are given the same reference numerals, and redundant explanation will be omitted.

In FIG. 8, the luminance signal Y of the input terminal (1) is lL
f-band portrait filter (1-lap゛) (+4) and subtraction: ; Commonly supplied to the wing (15), subtractor (15
), the output of the I-lap (14) is subtracted from the luminance signal Y. The center frequency of trap (14) is f S
Set equal to C. The output of the trap (14) is directly supplied to the subtractor (16) and the subtractor (15)
The output of the comb filter (20S) and coefficient unit (25)
via the subtractor (16). The rest of the configuration is the same as that shown in FIG. 3 above.

The operation of the embodiment of FIG. 8 is as follows.

Of the broadband luminance Nobuo Y supplied to the input terminal (1), the signal component centered at rsc is attenuated by the trap (14), and the output of the trap (14) is as shown in FIG.
As shown in , it becomes a partially deleted spectrum in which the vicinity of r sc is deleted in a v-shape. Trap like this (14)
The output of the subtracter (15) is subtracted from the broadband luminance signal Y from the input terminal (1), and although not shown, the output of the subtracter (15) is an inverse V centered at fSC.
It becomes a letter-shaped spectrum.

The output of the subtracter (15) is supplied to a comb filter (20S) with frequency characteristics as shown in FIG. This is a band-limited comb-shaped spectrum (not shown) of the envelope line of .

The output of the band-limited comb-shaped spectrum of the coefficient unit (25) is subtracted from the output of the partially deleted spectrum (■) of the trap (14) in the subtracter (16).
As conceptually shown in Figure B, the output becomes a partial comb-shaped spectrum (2) in which the deleted portion of the partially deleted spectrum (2) is supplemented with a band-limited comb-shaped spectrum whose polarity is inverted.

The embodiment shown in FIG. 8 has the same functions and effects as the embodiment shown in FIG.

Although the attenuation range due to the trap (14) is narrow, the mechanical spectrum of the carrier color signal is macroscopically f SO
There is no particular problem as the area is located near the area.

Further, as in the embodiment shown in FIG. 6, a feedback type comb filter can be used instead of the comb filter (2O3).

〔Effect of the invention〕

As described in detail above, according to the present invention, since the luminance signal transmission path is provided with a means for separating signal components in the frequency band of the carrier color signal and an IHJifl type filter color filter, a wide band can be obtained without impairing the luminance signal band. A color video signal forming circuit that can prevent interference between luminance signals and color signals and improve the quality of reproduced images is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a color video signal forming circuit according to the present invention, FIG. 2 is a spectrum diagram for explaining the operation of the embodiment of FIG. 1, and FIG. A block diagram showing the configuration of another embodiment, FIG. 4 is a spectrum diagram for explaining the operation of the embodiment of FIG. 3, and FIG. 5 shows a specific configuration of the main part of the embodiment of FIG. 3. Wiring diagram, No. 6
The figure is a block diagram showing the configuration of still another embodiment of the present invention,
FIG. 7 is a spectrum diagram for explaining the implementation of FIG. 6 + E'6 production, FIG. 8 is a block diagram showing the configuration of still another embodiment of the present invention, and FIG. 9 is an embodiment of FIG. 8. FIG. 2 is a spectrum diagram for explaining the operation of FIG. (12) is a bandpass filter, (13) and (15) are subtractors, (14) is a bandstop filter (trap), (
20), (2OS) is a comb filter, (21
) is an IH delay line.

Claims (1)

[Scope of Claims] A color video signal forming circuit for forming a color video signal by adding a luminance signal and a carrier color signal, comprising: a separation means for separating signal components in a frequency band of the carrier color signal; A color video signal forming circuit characterized in that a comb-shaped filter including a delay line is provided in a transmission path of the luminance signal.