JPS5831795B2 - Color television program - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a color television signal transmission system in which a carrier color signal formed by orthogonal two-phase modulation of a color subcarrier by two color signals is superimposed on a luminance signal and transmitted. It is something.

In conventional high-definition television systems, in order to transmit high-definition color image information, the band of the baseband signal that transmits brightness information and color information has been expanded, which is much wider than before. The need for transmission arises.

If we were to process the transmission, especially the reception, of television signals, which have become much wider as described above, by simply using the same signal format as an extension of the conventional method, the frequency band of the signal that should be handled by the receiver would be wasted. As the frequency band becomes wider, the utilization efficiency of the frequency band of the transmission path decreases, and the receiving equipment etc. also become complicated and expensive.Therefore, a new color television that can reduce the transmission frequency band while maintaining high quality color image quality is needed. A signal transmission method is required.

An object of the present invention is to solve the above-mentioned problems and to transmit high-quality, high-definition color image information by simplifying the configuration of a signal reproducing circuit in a receiving device, and by reducing distortion in the transmission system. An object of the present invention is to provide a color television signal transmission system that can reduce crosstalk and color distortion between color information and save signal transmission band.

That is, the color television signal transmission system of the present invention is as follows:
When a carrier color signal is formed by quadrature two-phase modulation of a subcarrier by a wideband color signal and a narrowband color signal, and the carrier color signal is superimposed on a luminance signal and transmitted, the wideband color signal and the narrowband color signal are When the frequency of the subcarriers is set to an integral multiple of the scanning line frequency, the polarity of the broadband color signal is alternately inverted for each scanning line, and the subcarriers have the same frequency and have a phase difference of 90 degrees from each other. When the frequency of is set to an odd multiple of + of the scanning line frequency, the polarity of the narrowband color signal is alternately inverted for each scanning line, and amplitude modulation is applied to each of the narrowband carrier color signal components to produce a wideband carrier color signal component and a narrowband carrier color signal component. are formed respectively,
Shared modulation that reduces the modulation level by half by combining these wideband and narrowband carrier color signal components with each other through two vestigial sideband modulation filters that share both sideband modulation bands. The present invention is characterized in that the carrier color signal is formed by the carrier color signal components of the wide band and narrow band whose frequencies are interpolated with each other only in the band.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of the configuration of a transmitting side device that forms and transmits a color television signal using the transmission method of the present invention, as well as signal band characteristics and signal spectrum representing the functions of each part thereof.

FIG. 1a shows an example of the configuration of a color television signal forming circuit on the transmitting side in the transmission system of the present invention. The luminance signal Y is converted into two chrominance signals, namely a wideband chrominance signal CW and a narrowband chrominance signal CN, and the luminance signal Y is passed through a low-pass filter 3 with a cutoff frequency fB.
to the mixer 4.

On the other hand, both wide and narrow band color signals CW. The CNs are each modulated via a low-pass filter amplifier 5.6 having a frequency band characteristic as shown in FIG. 1c and e, respectively, using a circuit configuration as shown in FIGS. 7 and 8.

In the configuration shown in Figures 1 and d, the wide and narrow band encoder output color signals CW and CN from the input terminals 15° and 22 are divided into two, respectively, and one is filtered by low-pass filters 16 and 23 with cutoff frequency fo and 6 dB attenuation. 17 and 24 respectively, and the other is a delay device 19 for adjusting the phase with the signal whose phase has been delayed by the filter 16.23.
．． 26 respectively to the subtracters 18 and 25, the band characteristics of the output signals are as shown in FIGS. 1c and 1e, respectively.
The gain in the band lower than the cutoff frequency fo is halved.

The subtracter outputs are outputted to output terminals 21 and 2 via low-pass filters 20 and 2γ with cutoff frequencies fw and fn, respectively.
If extracted from g, fo-fw and f are obtained from the 0-fo band components, respectively, as shown in Figure 1 c and e.
Wide and narrow band color signals CW and CN having band characteristics in which the gain of the o-fn band component is increased by 6 dB are obtained.

Next, as in the conventional carrier color signal formation, a color subcarrier having a carrier frequency fs (-nfh) that is an integral multiple of the horizontal scanning frequency fh is inputted to one of the modulators 7 and 8 from the input terminal 9. 7 is a phase shifter 10 with one additional delay.
and the above-mentioned wide-band and narrow-band color signals C
The carrier color signal components are amplitude-modulated by W and CN, respectively, and the polarity of one of these modulating color signals, for example, the wideband color signal CW, is changed from the input terminal 11 to the horizontal scanning period (1/fh). The switch SW, which is driven by supplying a switching signal, inverts each horizontal scanning period.

Such polarity reversal of one of the color signals results in a wide and narrow band color signal C.
This is to prevent the two carrier color signal components W and CN from sharing the same frequency in the vertical spatial frequency domain, thus facilitating separation between them and reducing interference. As seen in Figure i,
The spectrum of the narrowband carrier color signal is nfh, and the spectrum of the wideband carrier color signal whose polarity is inverted at +fh periods is 1+f
h(2n+1) frequency components, which are alternately interpolated as shown by solid lines and dotted lines.

For the above-mentioned wide and narrow band carrier color signal components, as shown in FIG. The carrier is guided to the mixer 4 through vestigial sideband modulation filters 12 and 13 having frequency band characteristics for band modulation, and is mutually combined to produce a carrier that has quadrature two-phase modulation of the color subcarrier of the carrier frequency fs. A composite television signal is obtained by combining the chrominance signal and superimposing it on the luminance signal Y.

In addition, in the residual sideband modulation filter 12.13, for example, the lower sideband is assigned to the wideband color signal CW, and the upper sideband is assigned to the narrowband color signal CN, and both of these carrier color signal components are The single sideband modulation band of the chrominance subcarrier is distributed above and below the color subcarrier, and the double sideband modulation components within the frequency fo where both bands are shared are mutually distributed by quadrature two-phase modulation as described above. maintain a phase relationship perpendicular to , so that the frequency spectra do not overlap with each other.

The frequency distribution of the composite color television signal according to the present invention, which has bottomed out as described above, is shown in Figure 1, and the details of the frequency spectrum distribution of the carrier color signal are shown in Figure 1i.
It becomes as shown in .

That is, as can be seen from the first diagram, the luminance signal Y and the carrier chrominance signal share a frequency band with the high frequency component of the luminance signal Y and a part of the lower sideband component of the wideband carrier chrominance signal CW. However, even in the shared band, as can be seen from Figure 1i, they maintain a line offset relationship, and do not share the same frequency components, and the carrier color signals do not interact with each other. As can be seen from FIG. 1, within the fs+fo frequency band centered on the color subcarrier with which both sideband modulation components share the band, the CW carrier color signal and the CN carrier color signal are Although they are multiplexed while maintaining the +line offset relationship and sharing the horizontal spatial frequency domain, as described above, they do not share the same frequency component.

Furthermore, in the frequency band exceeding fs+fo, only the upper sideband component, which is the single sideband modulated portion of the CN carrier color signal, occupies the band.

Note that in the above explanation, the color subcarrier frequency fs is an integer multiple of the horizontal scanning frequency fh, but this is set to an odd multiple of the horizontal scanning frequency fh, that is, -)fh(2n+1
) (In this case, the frequency relationship between the CW and CN carrier chrominance signal spectra described above is reversed, but the wideband chrominance signal CW from the F-wave amplifier 5 is directly guided to the modulator 7, and the p-wave If the narrowband chrominance signal CN from the amplifier 6 is guided to the modulator 8 with its polarity inverted alternately in lines, the frequency spectrum distribution of the resulting carrier chrominance signal will be as explained above.

Furthermore, it is also possible to arrange the single sideband modulation portions of both the CW and CN carrier color signals in a vertically reversed manner, taking into account the distribution of the luminance signal and the total frequency bandwidth.

FIG. 2 shows an example of the circuit configuration of a receiving device for receiving the above-described composite color television signal and restoring color image information in the transmission system of the present invention, and the band characteristics of each part thereof.

Figure 2a shows an example of the configuration of a color information signal restoration device on the receiving side in the transmission system of the present invention. The color television signal is guided from the input terminal 29 to the bandpass filter 30 (fS
-fW) to (fS+fn) are extracted.

The carrier color signal obtained as one wave output of the filter 30 is f
It is constructed of a one-horizontal scanning period (IH) delay device 31 having a narrowband characteristic with a passband of s±fo, an adder M1, and a subtracter M2, respectively, as shown in FIG. 2, for example. The signal is supplied alternately to two comb-shaped filters, and the CN carrier color signal and the CW carrier color signal, which are in a positive line offset relationship with each other as described above, are separated and taken out.

That is, the frequency characteristics of the two comb filters including the adder M1 and the subtracter M2 are shown by the dotted line and the solid line in FIG. 2, respectively, and are CW, CN,
In the fs±fo frequency band shared by both carrier color signals, the input signal exhibits a comb-shaped pass characteristic in which the gain is doubled at the peak value, and single sideband modulation components outside fs±fo are In the frequency band, the input signal is in its original form,
That is, it appears on the output side as a gain of 1.

Figure 2 also shows the passband characteristics of the above-mentioned comb filter adapted to the carrier color signal spectrum in the composite color television signal shown in Figure 1i, and the output of adder M1 is The subtractor M2 acts as a two-dimensional filter to extract the narrowband carrier color signal CN.
The output of acts as a two-dimensional filter that extracts the broadband carrier color signal CW.

That is, as shown in FIG. 2C, the carrier color signal components obtained in the detection output of the receiver using the transmission method of the present invention share the band fs±fo, and the narrow band components occupying the respective bands above and below it share the band fs±fo. Since it consists of wide-band carrier color signal components CN and CW, the outputs of adder M1 and subtractor M2 as carrier color signal components with such frequency distribution have frequency band characteristics as shown in FIG. 2d and e, respectively. The signals are led to color demodulators 34 and 35 via vestigial sideband demodulation filters 32 and 33, respectively.

Therefore, in the band fs±fo of the double sideband modulation components in the vestigial sideband demodulation filter described above, the response gain H (ωS) at the color subcarrier frequency is equal to that of the flat carrier part, and the color subcarrier frequency Any same frequency width p from the frequency
and H(ω8±p) at frequencies that are separated above and below, and fw-fo and fO~fn
In both bands, it is assumed that the characteristics are flat.

Therefore, the carrier color signals input to the color demodulators 34 and 350 obtained by applying carrier color signals having the frequency distribution characteristics shown in FIG. 2C to the filters 32 and 33 having such band characteristics both have flat frequency characteristics. .

The color demodulators 34 and 35 receive color subcarriers generated in phase synchronization with the color subcarrier components in the received signal in the color synchronization circuit 36, as in conventional color television receivers. The phase shifters 37 and 38 and the changeover switch SW are appropriately valved and supplied, and have a phase difference of 90 degrees,
In addition, the color demodulator 35 that reproduces the wideband color signal CW in accordance with the sending side performs synchronous detection of each input carrier signal component using a color subcarrier whose phase is inverted every horizontal scanning period, and performs demodulation of each input carrier signal component. Narrow and wide band color signal CN as output
, CW is reproduced and taken out from output terminals 39 and 40.

Next, FIG. 3 shows another embodiment of the color television signal transmission system of the present invention, with only the parts that are different from the previous example shown in FIGS. 1 and 2 selected.

First, in the embodiment shown in FIG. 3, the low-pass p-attenuators 5 and 6 in the transmitting side device shown in FIG. 1a are configured as shown in FIGS. The characteristics are shown in Figure 3.

Do as shown in d.

The configuration of the sawn wave amplifier 5 shown in FIG. 3a is almost the same as the configuration in the above example shown in FIG. It is wider than the band side fo.
Furthermore, the configuration of the stream wave amplifier 6 shown in FIG. 3C is significantly different from the configuration in the above-mentioned example shown in FIG.

Therefore, the band characteristics of the wide and narrow band color signals CW and CN passed through the r attenuation amplifiers 5 and 6 are as shown in FIG. 3d, respectively.

That is, in the wideband color signal CW, the gain of the fn-fw band component is 6 dB higher than that of the 0-fn band component, and in the narrowband color signal CN, the gain of the component in the fn-fn band is 6 dB higher than that of the 0-fn band component.
The entire band becomes the same as the gain of the components of the same band in the wideband color signal CW.

Next, in the embodiment shown in the third figure, the vestigial sideband modulation filters 12 and 13 in the transmitting side device shown in the first figure are
The zero band characteristics are shown in Figure 3 e and f, and Figure 1 f2
Unlike the above example shown in g, the band of the single sideband modulation part is set below the color subcarrier frequency fs, so that the wide and narrow band carrier color signal components CW and CN are (fs + fo
) ~ (fs - fn ) is shared in the horizontal spatial frequency domain, and within that band, both the wide and narrow band carrier color signal spectra maintain a one-line offset relationship, and in the vertical spatial frequency domain, both carrier color signal spectra maintain a one-line offset relationship. The carrier color signals are multiplexed in frequency separated format.

Therefore, the band characteristics of the detection output signal of the receiving device in the embodiment shown in Figure 3 are as shown in Figure 3, and the total band is (fs - fw) ~ (fs + fo),
Although narrower than in the previous example shown in FIG. 2C, both the wide and narrow band color signal components share the band, thus requiring the p-reducing effect of the comb-shaped pass characteristic as shown in FIG. 2C. The width of the frequency band is (fs-fn) to (fs+fo), as shown in FIG.

It is much wider than the bandwidth of (fs±fo) in the case of the above example shown in C, and the IH required for the comb filter configuration is
Since the pass band of the delay device 310 needs to be widened accordingly, it becomes necessary to use a complicated and expensive IH delay device with wide band characteristics.

In the embodiment shown in FIG. 3, the vestigial sideband demodulation filters 32 and 33 in the receiving device shown in FIG.
The band characteristics of FIG. 3 are shown in FIG. j
Unlike the previous example shown in FIGS. 2d and 2e, the band of the single sideband modulation part is selected below the color subcarrier frequency fs.

That is, in the embodiment shown in FIG. 3, the transmission band of the composite color television signal is narrower than in the previous example, but an IH delay device with wideband characteristics is required on the receiving side to reproduce the color signal.

As is clear from the above description, according to the present invention, the following remarkable effects can be obtained.

(1) Compared to conventional transmission systems, it is possible to transmit high-quality, high-definition color television signals without reducing the frequency band utilization efficiency of the transmission path.

(2) Two color information signals are transmitted with a line offset using a single color subcarrier with a frequency synchronized to an integral multiple of the horizontal scanning frequency, or an odd multiple of the horizontal scanning frequency, and the image vertical space is Since composite color television signals are transmitted by performing separable frequency division multiplexing in both the frequency domain and the horizontal spatial frequency domain, there is no crosstalk between color signals or deterioration of color image quality due to changes in transmission path characteristics. It is possible to transmit less color image information.

(3) In the color information reproducing device on the receiving side, even if the signal band of the color information to be reproduced as a high-quality, high-definition color television signal is wide, a signal delay element with narrow band characteristics, such as an IH delay line, is used. can be used to reproduce high-quality color information signals.

[Brief explanation of the drawing]

1A is a block diagram showing an example of the configuration of a transmitting circuit in the transmission system of the present invention; FIG. 1A is a block diagram illustrating a part of the circuit shown in FIG. e
2 is a characteristic curve diagram showing the band characteristics of the circuit shown in d, FIG. A block diagram showing an example of the configuration of a receiving circuit in the method, FIG.
3 to 3e are characteristic curve diagrams showing the band characteristics of each part of the circuit shown in FIG. In the figure, d is a characteristic curve diagram showing the band characteristics of the circuits shown in a and c of the figure, respectively, and e-j of the figure show the band characteristics of each part in the transmission system of the present invention with the circuit configuration shown in a to d of the figure, respectively. It is a characteristic curve diagram. 1...3 primary color signal input terminal, 2...signal converter, 3...low pass filter 4...
...Mixer, 5゜6...P reduction amplifier, 7,
8... Modulator, 9... Subcarrier input terminal, 10... Phase shifter, 11... Switching signal input terminal, 12, 13... ...Residual sideband filter 14...Color television signal output terminal, 15.22...Color signal input terminal, 16,
23...Low pass filter, 17,24...
...Attenuator, 18, 25...Subtractor, 1
9,26... Delay device, 20.27...
Sawa wave amplifier, 2L28... Color signal output terminal, 2
9...Color television signal input terminal, 30
... Bandpass filter, 31 ... Delay device, 32, 33 ... Residual sideband filter,
34, 35... Synchronous detector, 36...
・Color synchronization circuit, 37.38... Phase shifter, 39,
40...Reproduction color signal output terminal, 4L47...
...Reproduction color signal input terminal, 42.48...Low pass filter 43,49...Attenuator, 4
4...Subtractor, 45...Delay unit, 46
...Band pass filter, 50, 51...
... Reproduction color signal output terminal, Ml ... Adder, M
2...Subtractor, SW...Switch.

Claims (1)

[Claims] 1. When a carrier color signal is formed by quadrature two-phase modulation of a subcarrier by a wideband color signal and a narrowband color signal, and the carrier color signal is superimposed on a luminance signal and transmitted, the wideband color signal and the narrowband color signal are transmitted. When the frequency of the subcarrier is set to an integral multiple of the scanning line frequency, the polarity of the broadband color signal is alternately inverted for each scanning line, and the subcarrier of the same frequency has a phase difference of 90 degrees from each other. When the frequency of the carrier wave is set to an odd multiple of ten of the scanning line frequency, the polarity of the narrowband color signal is alternately inverted for each scanning line, and amplitude modulation is performed on each of the narrowband color signals to generate a wideband carrier color signal component and a narrowband carrier color signal. The modulation level is determined by combining the broadband and narrowband carrier color signal components with each other through two vestigial sideband modulation filters that share both sideband modulation bands. A color television signal transmission system characterized in that the carrier color signal is formed by the carrier color signal components of the wide band and narrow band whose frequencies are interpolated with each other only in a shared modulation band in which the frequency is halved.