JPS6236395Y2 - - Google Patents

Description

[Detailed description of the invention] This invention transmits color television signals using a time-base compression multiplex transmission method, or the so-called TCI transmission method.
Alternatively, it relates to a color signal transmitting/receiving device used when transmitting a luminance signal and two color signals, i.e., wideband and narrowband color signals, separately by a component separation transmission method, in particular, multiplex transmission of both wideband and narrowband color signals. The deterioration of the characteristics can be reduced.

In general, in the above-mentioned various transmission methods that multiplex transmit two color difference signals constituting a color television signal or two color signals such as an I signal and a Q signal, the line correlation of color television images is used to A multiplex transmission system that alternately transmits these two color signals every cycle has been conventionally used, but in such line alternate multiplex transmission, both the two color signals, the wideband color signal and the narrowband color signal, are During a line period in which no color signal is transmitted, extremely simple signal interpolation is performed in which the same type of color signal transmitted in the previous line period is delayed by one line period and interpolated. This method has disadvantages in that interpolation noise occurs in which the color signal is discontinuous in the vertical direction, and the resolution in the vertical direction decreases, resulting in a significant deterioration in the quality of the reproduced color image.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks, to multiplex and transmit both wide and narrow band color signals constituting a color television signal without mixing them with each other, and without interfering with each other. It is an object of the present invention to provide a color signal transmitting/receiving device that can be easily separated and reproduced without causing deterioration of characteristics.

That is, the color signal transmitting and receiving device of the present invention is a color signal transmitting and receiving device that transmits and receives two color signals constituting a color television signal as a wideband color signal and a narrowband color signal. The highest frequency is F _W
and F _N and their highest frequency F _W
When F ₀ is a frequency that is an odd multiple of 1/2 of the horizontal scanning frequency _H of the color television signal, which is approximately equal to the difference between the horizontal scanning frequency H of the color television signal and F _N , the horizontal scanning frequency is approximately equal to the frequency F _N due to the narrow band color signal. A first modulated carrier signal that modulates a first carrier wave having a frequency F ₁ that is an integer multiple of _H and passes through a first lower vestigial sideband filter is used to generate the sum of frequencies F ₁ and F ₀ . transmitting a sum signal formed by adding a second modulated carrier signal obtained by re-modulating a second carrier wave having a frequency and passing through a second lower vestigial sideband filter and the broadband color signal; Then, the received sum signal is passed through a comb which exhibits almost flat characteristics up to frequency F ₀ and whose center frequencies of successive passbands from frequency F ₀ to frequency _FW are equal to successive integer multiples of the horizontal scanning frequency _H. At the same time, the received sum signal is passed through a wideband filter exhibiting type characteristics to reproduce the wideband color signal, and the received sum signal is converted to a horizontal scanning frequency _H in the frequency range from frequency _F0 to _FW .
a carrier signal having a frequency equal to the second carrier wave and the first The present invention is characterized in that the narrowband signal is reproduced by sequential demodulation using a carrier wave signal having the same frequency as the carrier wave.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In general, a wideband color signal and a narrowband color signal that constitute a color television signal have frequency component distribution characteristics having maximum frequencies F _W and F _N that are significantly different from each other, as shown in FIGS. 1a and b, respectively. Each exhibits Such wide-band and narrow-band color signals are based on the properties of television signals that form images through horizontal and vertical scanning, and the fine structure of the spectral distribution is based on the second
As shown in the figure, vertical frequency spectral components with frequency intervals equal to the field frequency _V are arranged with gradual attenuation in close proximity to both sides of the horizontal frequency spectral components equal to successive integer multiples of the horizontal scanning frequency _H. The harmonic spectrum groups of the field frequency _V that are associated with the harmonic spectrum components of the horizontal scanning frequency _H intersect with each other at a frequency interval equal to the frame frequency _P.

Therefore, as shown in FIG. 3a, wide-band and narrow-band color signals having both such spectral distributions have the frequency positions of their spectral components shifted from each other by an odd multiple of 1/2 of the horizontal scanning frequency _H , and As for the spatial frequency characteristics of images with gradual changes in the horizontal direction, such as horizontal stripes, the horizontal frequency spectrum has only low-frequency components, so the highest frequencies F _W and F _N of the color signals in both wide and narrow bands are almost the same. If the frequencies are interpolated with each other, the respective spectral components are arranged alternately, so that they can be easily frequency multiplexed and transmitted as shown in Figure 3b. By using two types of comb-shaped filters whose band center frequencies are shifted by 1/2 of the horizontal scanning frequency _H and whose center frequency intervals are both equal to the horizontal scanning frequency _H , both wide and narrow bands can be created with frequency interpolation in the manner described above. The vertical comb-type filter can be easily constructed using line-period delay elements. Note that even if the high-frequency components of the vertical frequency spectrum are deleted due to the comb-shaped furnace wave characteristics, the deterioration of the vertical characteristics due to the deletion is slight.

According to the present invention, by interpolating the frequencies of both wide and narrow band color signals having the frequency component distribution characteristics shown in FIGS. 1a and 1b, as shown in FIGS. 3a and 3b, as shown in FIGS. The signal processing for converting into a frequency multiplexed signal is carried out in the manner shown in sequence in FIGS. 4a to 4e. Although the present invention will be described below with reference to the case where the color signal is processed as an analog signal, it is possible to process the color signal more stably if it is processed as a digital signal as will be described later.

Therefore, in the operating principle of color signal conversion by the device of the present invention shown in FIGS. 4a to 4e, the narrowband color signal having the frequency component distribution characteristics shown in FIG. Let be a positive integer,
A carrier wave signal consisting of a sine wave having a frequency F ₁ having the relationship F ₁ =k _H ≈F _N with respect to the horizontal scanning frequency _H and the highest frequency F _N of the narrowband color signal is modulated by amplitude modulation, and the signal shown in FIG. As shown by the solid line, the frequency ranges from 0 to 2F ₁ with the frequency F ₁ as the center.
A modulated signal with a spectral distribution consisting of both sideband waves reaching up _to 2, a linear phase low-pass filter G _1N exhibits point-symmetric linear attenuation characteristics with respect to frequency F ₁ and takes the form of a vestigial sideband filter with frequency 0 as the lower limit.
(), extract the lower sideband component from frequency 0 to approximately _F1 , and then calculate the difference between the highest frequencies F _W and F _N of the wide and narrow color signals as shown in d of the same figure. Almost equal and horizontal scanning frequency _H
Frequency F 2 equals the sum of frequency F ₀ equal to an odd multiple of 1/2 and carrier frequency F ₁ mentioned above, F ₂ = F ₀ + _{F 1}
When a carrier wave signal consisting of a sine wave with , is modulated by amplitude modulation, as shown by the solid line in Figure e,
A modulated signal consisting of both sideband waves having a vertically symmetrical spectral distribution centered on frequency F ₂ is again formed. In this way, a modulated signal with a spectral distribution approximately ranging from frequency F ₀ to frequency F ₂ +F ₁ is converted into a modulated signal with a response of 1 at the carrier frequency F ₂ as shown by the dotted line in the figure e. /2, a linear phase low-pass filter G exhibiting point-symmetric linear attenuation characteristics with respect to frequency F ₂ and forming a vestigial sideband filter with frequency 0 as the lower limit.
_2N () and extract the lower sideband component from frequency F ₀ to approximately F ₂ , as shown in Figure 3a and b, the maximum frequency F _W of the wideband color signal has the maximum frequency F _N The frequency ranges are shifted so that they almost match, and a narrowband color signal with a spectral distribution having horizontal frequency spectral components at frequency positions that are odd multiples of 1/2 of the horizontal scanning frequency _H can be obtained. By adding the narrowband color signal with such a spectral distribution to the wideband color signal with the original spectral distribution, a wideband and narrowband color signal multiplexed with frequency interpolation is obtained as shown in Figure 3a. It will be done.

Next, in accordance with the operating principle described above, multiplex conversion is performed by frequency interpolation of both wide and narrow band color signals, and the multiplexed color signals are received and separated from each other through the reverse conversion process to convert both wide and narrow band color signals. FIG. 5 shows an example of the configuration of the color signal transmitting/receiving device of the present invention, which reproduces each color signal. In the illustrated circuit configuration, in order to stably and reliably implement the above-mentioned operating principle for both wide and narrow band color signals in the form of analog signals in the form of digital signals, first,
Wideband analog color signal _W (t) and narrowband analog color signal _N supplied to input terminals 1 and 2
(t) to analog-to-digital converters 3 and 4
After converting the signals into digital signals, the signals are respectively guided to a wide band filter 5 and a narrow band filter 6 to extract both wide and narrow band color signals having the spectral distributions shown in FIG.

The above-mentioned wideband filter 5 and narrowband filter 6 have frequency characteristics as shown in FIGS. 6a and 6b, respectively.
The wideband filter 5 shown in FIG. 1 exhibits a substantially flat characteristic from frequency 0 to a frequency F ₀ that is almost equal to the difference between the highest frequencies F _W and F _N of both wide and narrow band color signals, and from that frequency F ₀ to Up to the highest frequency F _W , there is no broadband reduced pass filter G _W ( ) exhibiting the characteristics of a comb filter with successive pass bands with center frequencies at frequency positions equal to successive integer multiples of the horizontal scanning frequency _H. , and the narrowband filter 6 shown in _FIG .
Narrowband low-pass filter G _N exhibiting the characteristics of a comb filter with successive passbands with center frequencies at frequency positions equal to successive integer multiples of _H
().

In order to minimize mutual mixing in the multiplex transmission of wide and narrow band color signals, it is preferable to send the wide and narrow band color signals through the wideband filter 5 and the narrowband filter 6, respectively, as described above. However, when emphasis is placed on the fidelity, definition, etc. of both wide and narrow band color signals, it is desirable to omit the above-mentioned filters 5 and 6 in order to avoid deletion of signal components due to such wave effects.

In addition, as mentioned above, in an image with gradual changes in the horizontal direction such as horizontal stripes, the horizontal frequency spectrum of both the wide and narrow band color signals consists of only low frequency components, so the narrow band filter 6 is also
As shown by the dotted line in , it is also possible to have a substantially flat characteristic from frequency 0 to frequency F ₀ as in the broadband filter 5 .

Next, the spectral components of the wideband color signal taken out from the wideband filter 5 are directly led to the adder 11, while the spectral components of the narrowband color signal taken out from the narrowband filter 6 are led to the multiplier 7, and are shown in FIG. 4b. The carrier signal ₁ (n) having the frequency F ₁ described above is subjected to amplitude modulation by multiplication, and the modulated output signal is converted into the modulated output signal shown in FIG. 5 d, which is equivalent to the low-pass filter G _1N ( A low-pass filter ₈ having the characteristics shown in _FIG . Amplitude modulation is applied, and the modulated output signal is guided to a low-pass filter 10 having characteristics as shown in FIG. 6e, which is equivalent to the low-pass filter G _2N () described above with respect to FIG. If only the wave components are extracted, a narrowband color signal consisting of the spectral components shown in FIG. The frequency multiplexed signal of the band chrominance signal is taken out and returned to the form of an analog signal via the digital-to-analog converter 12, and sent to the transmission line. Note that this frequency multiplexed signal can also be transmitted in the form of a digital signal.

On the other hand, on the receiving side, the received frequency-multiplexed color signal is guided to low-pass filters 14 and 15 via an analog-to-digital converter 13. Therefore, the low-pass filter 14, like the wide-band filter 5 on the transmitting side, has the same characteristics as the wide-band low-pass filter G _W () shown in FIG. 6a, and its wave output The broadband color signal _W (t) extracted as
6 from the output terminal 17. Furthermore, as shown in FIG. 6c, the low-pass filter 15 ranges from frequency _F0 to frequency _FW , and has center frequencies at frequency positions that are sequentially odd multiples of 1/2 of the horizontal scanning frequency _H. It has the same characteristics as a comb-shaped film G _3N () with sequential passbands, and therefore, its wave output is a narrowband color signal with the spectral distribution shown in Figure 3a and b. can be extracted. In order to perform double demodulation on the narrowband color signal having such a spectral distribution, which is opposite to the double amplitude modulation on the transmitting side described above with reference to FIGS.
8 and 19 in sequence, FIGS. 4d and b
After repeated demodulation of synchronous detection by multiplication using the carrier signals ₂ (n) and ₁ (n) having the aforementioned frequencies F ₂ and F ₁ , respectively, the output signal is output via the digital-to-analog converter 20. A narrowband color signal _N (t) having the original spectral distribution is taken out from the terminal 21 .

In addition, when applying the spectral distribution conversion by double modulation described above with reference to FIGS. 4 a to e to the digital color signal, the sampling performed when converting the color signal to a digital signal results in the conversion of the spectral distribution shown in FIGS.
As shown in FIGS. 7a to 7e, respectively, aliasing components of the frequency arrangement that have a mirror image relationship with respect to the sampling frequency F _S occur with respect to the frequency arrangement shown in FIG. 4 regarding the frequency 0. To avoid mixing with ingredients,
The sampling frequency _s should be selected to be at least approximately three times the frequency mentioned above with respect to FIG. 4d, and therefore approximately three times the highest frequency F _W of the broadband color signal.

Regarding the comb-shaped filter characteristic shown in FIG. 6c, it is necessary to make the successive passbands wide so that the vertical frequency spectral components attached on both sides of the horizontal frequency spectral component are not attenuated as much as possible.

As is clear from the above description, according to the present invention, two types of color signals in both wide and narrow bands can be multiplexed and transmitted without deteriorating the resolution of the reproduced color image in both the horizontal and vertical directions. By skillfully taking advantage of the fact that there are not many image components composed of fine diagonal lines in nature, and that the visual sense is not very sensitive to image components with such diagonal lines, multiplexing of color signals is possible. Deterioration in reproduced color image quality due to transmission can be kept to a minimum. In addition, as described above with reference to FIG. 3a, since the narrowband color signal whose frequency position is shifted is not superimposed on the low range of the wideband color signal, the characteristics of the low range component do not deteriorate at all. . On the other hand, for the low frequency components of the narrowband color signal, in the area where they overlap with the wideband color signal, preprocessing is performed in the low frequency section using a wideband comb filter characteristic in the vertical direction to prevent deterioration due to mixing. It is possible to suppress the deterioration of horizontal stripe components, but if the high frequency components of both wide and narrow band color signals are pre-processed using comb filter characteristics, conventional TCI
It can also be applied to transmission and component separation transmission, and since the energy of the multiplexed color signal is concentrated in the low range, it can also be applied to FM transmission such as satellite broadcasting. Further, since the multiplex conversion signal processing according to the present invention can be performed by a digital system, stable and reliable operation can be expected.

[Brief explanation of the drawing]

Figures 1a and b are characteristic curve diagrams showing the frequency distribution characteristics of both wide and narrow band color signals, Figure 2 is a diagram showing an example of the spectrum distribution, and Figures 3a and b are color signal transmission and reception according to the present invention. Diagrams showing examples of frequency multiplexing of both wide and narrow band color signal spectral components in the apparatus, FIGS.
FIG. 5 is a block diagram showing an example of the circuit configuration, FIGS. 6 a to 6 e are characteristic curve diagrams showing characteristic examples of various filters used in the circuit configuration, and FIGS. FIG. 3 is a diagram sequentially showing the operating principle of a digital system. 1, 2... Input terminal, 3, 4, 13... Analog-digital converter, 5, 14... Broadband filter, 6... Narrowband filter, 7, 9, 18, 1
9... Multiplier, 8, 10, 14, 15... Low pass filter, 11... Adder, 12, 16, 20
...Digital to analog converter, 17, 21...
...Output terminal.

Claims (1)

[Scope of utility model registration request] In a color signal transmitting and receiving apparatus for transmitting and receiving two color signals constituting a color television signal as a wideband color signal and a narrowband color signal, the maximum frequencies of the wideband color signal and the narrowband color signal are F _W and F _N , respectively, and F _O is an odd-numbered multiple of 1/2 the horizontal scanning frequency _H of the color television signal which is approximately equal to the difference between the maximum frequencies F _W and F _N , the apparatus transmits a sum signal formed by adding together a second modulated carrier signal which is obtained by modulating a first carrier wave having a frequency F ₁ which is an integer multiple of the horizontal scanning frequency _H which is approximately equal to frequency F _N with the narrowband color signal and passing the first modulated carrier signal through a first lower vestigial sideband filter, and then modulating a second carrier wave having a frequency which is the sum of frequencies F ₁ and F ₀ with the first modulated carrier signal and passing the second modulated carrier signal through a second lower vestigial sideband filter, the second modulated carrier signal being modulated again with the second modulated carrier signal and passing the second modulated carrier signal through a second lower vestigial sideband filter, the sum signal received being a signal which has an approximately flat characteristic up to frequency F ₀ and has successive passband center frequencies from frequency F ₀ to frequency F _W which are equal to the horizontal scanning frequency
The wideband chrominance signal is regenerated by passing the sum signal through a wideband filter having a comb characteristic equal to successive integer multiples of _H , and the wideband chrominance signal is regenerated by passing the sum signal through a wideband filter having a comb characteristic equal to successive integer multiples of H, and
a color signal transmitting and receiving device, characterized in that the narrowband color signal is reproduced by introducing the signal into a filter having a comb-shaped characteristic with successive passbands having center frequencies equal to successive odd _- numbered multiples of 1/2 _{the horizontal scanning frequency H in} the frequency range from F0 to Fw, and then demodulating the signal sequentially with a carrier signal having a frequency equal to the second carrier signal and a carrier signal having a frequency equal to the first carrier signal.