JPS6345991A - Transmission system for television signal - Google Patents

Abstract

PURPOSE:To improve the picture quality of a reproduced picture while keeping compatibility with existing system by applying frequency conversion to a chrominance carrier signal at the outside of a prescribed band and multiplexing the signal with a luminance signal and the chrominance carrier signal within a prescribed band. CONSTITUTION:NTSC system 3-primary color video signals R, G, B from a TV camera 1N are fed to a matrix circuit 11 to form a luminance signal Y of 0.4-4.2MHz and a couple of color signals IW4, QW4. The broad band color signals IW, QW are fed to a modulator 14 to apply orthogonal biphase 15 and the result is fed in common to a subtractor 51 and a band-pass filter 52. Since the phase of the carrier for shift-down is inverted between fields, the spectrum of conversion high-definition chrominance carrier signal Cus is incorporated in the spectrum gap of the luminance signal Y and chrominance signal C of the NTSC system. Thus, the television signal including high-definition color signal having copatibility with the existing system is obtained.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Example G1 Encoder of one example (Fig. 1) Figure 1, Figures 3 to 5)
G2 Embodiment Decoder (Figs. 2 and 6) H Effects of the Invention A Industrial Field of Application The present invention relates to an end-return television signal transmission system that is compatible with the current NTSC system. .

B. Summary of the Invention The present invention frequency-converts a carrier chrominance signal outside a predetermined band and multiplexes it with a luminance signal and a carrier chrominance signal within a predetermined band, thereby achieving high definition while maintaining compatibility with current systems. This makes it possible to obtain reproduced images of the same degree.

C. Conventional technology Based on the current NTSC system standard, in order to improve the definition of television images, the Institute of Electronics and Communication Engineers Technical Report C38 published a ``proposal for a remote-end mTV system with complete communication performance''.
3-61 (July 1982), etc.

First, while referring to FIGS. 7 to 10, EDTν(E
xter+rled Definition T V
) system, the signals of the 1ni elliptical TV system will be explained.

As is well known, a wide frequency band is required to transmit high-definition information in the horizontal direction. In the EDTV system, as shown in Figure 7, the NTSC system's 4.2Ml1
higher range than the luminance signal Y up to z, for example, 4.0 to 6
．． High-definition information in the frequency band of 0 MIIz (high-range brightness 16
No.) YH is low-frequency converted (shifted down) and multiplexed into a band of, for example, 2.2 to 4.2 MHz within the frequency band of the NTSC system. Hereinafter, the downshifted high-frequency luminance signal may be expressed as YH8 to distinguish it from the original high-frequency luminance signal υYH.

By the way, in the NTSC system, the color subcarrier frequency fSC is selected to satisfy a specific condition, and the spectrum of the luminance signal Y and the spectrum of the color signal C have a frequency interleaving relationship as shown in FIG. 8A. It is in.

However, if you look at the figure in detail, you will see that the spectrum of the color signal C is inserted into every other gap in the spectrum of the luminance signal Y, and there is still an empty gap in every other gap. Therefore, in the EDTV system, as shown in Figure 8B,
The downshifted high-frequency luminance signal Yos is inserted into this empty gap.

The micro frequency gap in FIG. 8 is two-dimensionally represented in the [time-vertical] frequency domain shown in FIG. That is, the color signal C of the NTSC system is placed in the second and fourth quadrants, and the high-frequency luminance signal VH8 of the EDTV system is placed in the first and third quadrants.

In addition, in order to arrange the spatio-temporal frequency spectrum of the high-band luminance signal YH as shown in FIG. 9, the phase of the subcarrier for downshifting the high-band luminance signal YH is as shown in FIG. 10. It is necessary to set the scanning lines having VH8 subcarriers of the same phase to descend every field.

Next, a circuit configuration for multiplexing and separating the high-band luminance signal YH of the EDTV system as described above will be explained with reference to FIGS. 11 to 13.

FIG. 11 shows an example of the configuration of a conventional EDTV encoder and decoder.

In FIG. 11, (10) shows the encoder as a whole, and a wide band three primary color image signal Rw is transmitted from the TV camera 1w.
. Both band chrominance signals ILi1G and Ql, I6 are filtered to 1.5MHz and 0 by low-pass filters (12N) and (13N), respectively.
．． The band is limited to 5 MHz and becomes the standard color signal WI and Q of the NTSC system. These color signals l and Q are sent to a modulator (14
), the chrominance subcarrier (fsc) supplied from the oscillator (15) to the modulator (14) is quadrature two-phase modulated, and the standard carrier chrominance signal C (2, 1 to 4) is output from the modulator (14). .2M
l1z) is supplied to the adder (16).

The wideband luminance signal Y- is commonly supplied to a high-pass filter (17) and a low-pass filter (18), and is separated into a high-pass luminance signal Y)l and a luminance signal Y, respectively. 20), the high frequency luminance signal YH is shifted down by I and multiplexed with the luminance signal Y. Taichi circuit (2
0) will be described in detail later. Multiple times! The output of /8 (20) is supplied to the adder (16) and combined with the carrier color (i-C), and the E[lTV signal is derived to the output terminal (19).

(30) shows the decoder as a whole, and the encoder (1
0) is commonly supplied to the low-pass filter (32) and the high-pass filter (33) from the input terminal (31) of the decoder (30), and the high-pass filter (33)
The output of is supplied to the separation circuit (40).

Details of the separation circuit (40) will be described later. Separation circuit (40)
Standard carrier color signal C (2,1~4,2Mllz
) is the color? j! A pair of standard color signals I and Q are supplied from the demodulation circuit (34) to a matrix circuit (35).

Frequency band lower than carrier color signal C (0 to 2.1M H
A low-pass luminance signal YL of z) is supplied from a low-pass filter (32) to an adder (36). From the separation circuit (40) to this adder (36), 2.1 to 4
．． A mid-range luminance signal YM in a frequency band of 2 MHz is directly supplied. Further, the high-frequency luminance signal yes shifted down from the separation circuit (40) is supplied to the high-frequency conversion circuit (37), and high-frequency conversion (shift-up) is performed, which is the reverse process of the low-frequency conversion in the multiplex circuit (20), which will be described later. ) is supplied to the adder (36). As a result, 0 to 6 M from each luminance signal YL, YM, YH
The Hz broadband luminance signal Y- is restored and sent to the adder (36
) is supplied to the matrix circuit (35). In the matrix circuit (35), the standard color signals I, Q and the wideband luminance signal Yw are used as [! DTV system three primary color signal R-1-
YH, G+Y14 and B+YH are formed and supplied to the picture tube (2).

FIG. 12 shows an example of the configuration of the multiplex circuit (20). This first
In Fig. 2, t (21) is an amplitude modulator, and the terminal (
20a) is supplied with the high-frequency luminance signal YH, and
The output of the 1/2 frequency divider (22) supplied with the color subcarrier as a carrier wave for downshifting the high-band luminance signal YH is transmitted from the terminal (20f) via the switch (23).
Supplied. As a result, the frequency band is 4.0~G,
The high-frequency luminance signal Y)l of OM Ilz is f SC/2
* Modulated at a frequency of 1.8MHz. Modulation n(2
+) is supplied to the bandpass filter (24) and
．． The lower sideband from 2 to 4.2 MHz is separated and downshifted. Downshifted high-range luminance signal V
H8 and the luminance signal Y from the input terminal (20b) are multiplexed in the adder (25) and sent to the output terminal (20c).
) is derived.

Also, in order to invert the phase of the carrier wave for each field,
The output of the frequency divider (22) is directly supplied to one fixed contact (23a) of the switch (23), and the other fixed contact (
23b) is supplied via the inverter (26), and the movable contact (23c) of the switch (23) is
a second 1/2 frequency divider (27) to which the vertical drive signal is supplied;
The re-fixing contacts (23
a) and (23b) alternately. Although not shown, the first frequency divider (22) is phase-locked by the horizontal drive signal.

Note that in a recent example, the frequency of the carrier wave for downshifting described above has been changed to 0.6fsc*2.15M Ilz.

FIG. 13 shows an example of the configuration of the separation circuit (40). This first
In Figure 3, (41) is 26 by field memory.
21+delay line, the first and second subtractors (42)
A signal of the current field is supplied from a terminal (40i) in common with (43) and (43). In the first subtracter (42), the previous field signal output from the delay line (41) is subtracted from the current field signal to obtain a downshifted high-band luminance signal VH8. Also, the delay line (4
The output of 1) is fed through an IH delay line (44) to a second subtractor (43), where it is subtracted from the current field signal to yield a standard carrier color signal C (lI).

In addition, 'YHs and C separated in this way are connected to a separation circuit (
40), the mid-range luminance signal YM is separated, such as by subtraction from the composite signal supplied to 40).

D Problems to be Solved by the Invention In the above-mentioned UDTV system, the frequency bandwidth of the luminance signal is
While the current NTSC system's 4.2M1lz will be expanded to 6MHz, the bandwidth of color signals I and Q will be
Same as the NTSC system, 1.5M1lz and (
It stays at 1,5Ml1z.

As is well known, in the NTSC system, the bandwidth of the color signal is
The direction is determined to make it as narrow as possible using visual characteristics.

However, from another perspective, considering the high definition of picture tubes from the time the method was decided to the present, the quality of the reproduced image is not necessarily sufficient with the current color signal bandwidth. The problem arises that it is not satisfactory.

In view of this, an object of the present invention is to provide a television signal transmission system that can improve the quality of reproduced images while maintaining compatibility with current systems.

E. Means for Solving Problems The present invention obtains a carrier color signal using a pair of color signals in a wider band than a predetermined frequency band, and converts the carrier color signal outside the predetermined frequency band to obtain a carrier color signal in the predetermined frequency band. This is a transmission system for television signals that is multiplexed with a luminance signal and a carrier color signal.

F Effect: According to this configuration, it is possible to obtain a wideband color signal on the receiving side while maintaining compatibility with the current system, and the quality of the reproduced image is improved.

G. Embodiment Hereinafter, an embodiment of the television signal transmission system according to the present invention will be described with reference to FIGS. 1 to 6.

G1 Embodiment Encoder The configuration of an encoder according to an embodiment of the present invention is shown in FIG. In FIG. 1, parts corresponding to those in FIG. 11 are designated by the same reference numerals, and some explanations will be omitted.

In Figure 1, from the TV camera IN to the NTSC system 3
The purulent image signals υR, G, B are supplied to a matrix circuit (11), which outputs a luminance signal Y of 0 to 4, 2 Mllz and a pair of color signals, 1, . 4 and Ql, +4 are formed.

The luminance signal Y is directly fed to the adder (16), and both color signals IW4 and Qu4 are each passed through a low-pass filter (12u).
and (13), as shown by the thick lines in FIG. 3, O~2.5M1lz and O~1
．． The chrominance signals +v and Q have a relatively wide band of OMHz. The broadband color signals I and Qu are supplied to the modulator (14), which converts the color subcarrier (fsc) supplied from the oscillator (15) to the modulator (14) into quadrature two-phase transformers.
14), a wideband carrier color signal CW is commonly supplied to the subtracter (51) and bandpass filter (52).

The output of the bandpass filter (52) is commonly supplied to the adder (16) and the subtracter (51), and the output of the subtracter (51) is passed through the high-pass filter (53) to the low-pass conversion circuit (54).
supplied to This low frequency conversion circuit (54) is the 12th one mentioned above.
From the multiplex circuit (20) in the figure to the frequency divider (22) and adder (
The color subcarrier output of the oscillator (15) is divided by 315 times in the frequency divider (22) and supplied, and the output of the low frequency conversion circuit (54) is supplied to the adder (25).
16).

The operation of the encoder of FIG. 1 is as follows.

Corresponding to the pair of broadband color signals I and Q shown in FIG. 3, the wideband carrier color signal CW output from the color modulator (14) is as shown by the solid line in FIG. 4A. 1,0
It is composed of an I signal component of 8 to 6.08 MHz and a Q signal component of 2.58 to 4.58 MHz as shown by the dashed line. From this wideband carrier signal Cw, a 2.0
8~4.2M Ilz NTSC standard conveyance color ℃
C is separated and this standard carrier color signal C is subtracted from the wideband carrier color signal Cu in a subtractor (51) to obtain 1.08=2,08M as shown in FIG. 4C.
The lower high-definition carrier color signal CL of llz, 4.2...
6.08M 117. An upper high-definition carrier color signal CU is obtained. The upper high-definition carrier color fraction υCu is separated by a high-pass filter (53) and supplied to a low-pass conversion circuit (54). In this low-frequency conversion circuit (54), low-frequency conversion (downshift) similar to that in Leno is performed on the multiplex circuit (20) described above, resulting in L 4.2 as shown in FIG. 5A.
~6.08MHz upper high-definition carrier color signal Cu4j,N
2.05-3.93M H within the frequency band of TSC method
z is shifted down to a high-definition carrier color signal CUS.

In the adder (16), this converted high-definition carrier color signal C
US and the standard carrier color signal C from the bandpass filter (52)
and the luminance signal Y are added. In this example,
Since the phase of the carrier wave for downshifting is inverted between fields, the spectrum of the converted high-definition carrier color signal CLjS is at the position of VH8 in FIG. is incorporated into each spectral gap.

As a result, a television signal containing a high-definition color signal that is compatible with current systems can be obtained.

Note that the lower high-definition conveyance color signal Cc shown in FIG. 4C.

When using, the high-pass filter (53) is changed to a low-pass filter, and the low-pass conversion circuit (54) is changed to a high-pass conversion circuit (see Figure 11), as shown in Figure 5B. Then, a shift amplifier to 3.23 to 4.23 MHz may be performed.

Decoder according to an embodiment of G2 The configuration of a decoder according to an embodiment of the present invention is shown in FIG. In this Fig. 2, the parts corresponding to Fig. 11 are the same.
A part of the explanation will be omitted.

In Fig. 2, the television signal formed by the encoder in Fig. 1 is supplied from the input terminal (31) to the YZC branch joint circuit), and the separated luminance signal Y is supplied to the 7-trix circuit (35). At the same time, the sign tl! ! I aperture feeding color signal C and downshifted upper high-definition feeding color signal CU
S is supplied to the color signal separation circuit (60). This color signal separation circuit (60) is the separation circuit (40) shown in FIG. 13 above.
The separated standard carrier color signal C is supplied to an adder (36), and the downshifted upper high-definition carrier color signal CUS is supplied to a high frequency conversion circuit (37). By shifting up in this high frequency conversion circuit (37),
is supplied to the adder (36). As a result, Figure 6A
As shown in the figure, a broadband general color signal 'i':'c tyu biased upward from 2.08 to 6.08 MHz is obtained. This wideband carrier color signal C1alU is supplied to a wideband color demodulator (34w), and the demodulated outputs of this demodulator (3h), ie, wideband color signals 1w and Qw, are supplied to a matrix circuit (35). In the matrix circuit (35), three high-definition primary color signals R'', G+ and B+ are formed from the two-band color signals 1w and Q and the luminance signal Y, and are supplied to the picture tube (2). As a result, a reproduced image with improved image quality can be obtained.

In addition, when using the converted high-definition carrier color signal Ct, s shown in FIG. 5B, the high-frequency conversion circuit (37) is changed to the low-frequency conversion circuit (54) in FIG. As shown in 1
．． What is necessary is to obtain a broadband carrier color signal CW biased toward the lower side of 08 to 4.2 MHz.

Further, wideband color difference signals (RY)w and (B-Y)w may be obtained from the color demodulator (34v) instead of IW and Qu.

Effects of the Invention H As detailed above, according to the present invention, the carrier color signal outside the predetermined band is frequency-converted and multiplexed with the luminance signal and the carrier color signal within the predetermined band, so that the receiving side This provides a television signal transmission system that can obtain a wideband color signal and improve the quality of reproduced images while maintaining compatibility with current systems.

[Brief explanation of the drawing]

FIG. 1 shows a television signal transmission system according to the present invention.
・A block diagram showing the configuration of an encoder according to an embodiment, FIG. 2 is a block diagram showing a configuration of a decoder according to an embodiment of the present invention, and FIGS. 3 to 6 explain an embodiment of the present invention. Figures 7 to 10 are spectrum diagrams and diagrams for explaining the conventional television signal transmission system, and Figures 11 to 13 are the conventional television signal transmission system and its diagrams. FIG. 2 is a block diagram showing an example of the configuration of main parts. (54) is a low frequency conversion circuit (interfield transposition modulation circuit)
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Claims (1)

[Claims] A carrier color signal is obtained by a pair of color signals in a wider band than a predetermined frequency band, and the carrier color signal outside the predetermined frequency band is frequency-converted to produce a luminance signal and a luminance signal in the predetermined frequency band. A television signal transmission system characterized in that it is multiplexed with a carrier color signal.