JP2529948B2 - Image signal transmission system - Google Patents

Description

Detailed Description of the Invention [Object of the invention]

(Field of Industrial Application) The present invention relates to an image signal transmission system for transmitting and receiving television signals. (Prior Art) With the development of the highly information-oriented society, the motivation for higher image quality of TVs has increased, and the development of high-definition TVs / systems has been vigorously pursued in the last few years. However, when using this high-definition TV system, a very wideband signal must be transmitted. Therefore, various proposals have been made in the past such as this transmission method and communication with the current system. Among them, the use of the standard NTSC transmission line currently being broadcast and compatibility with this standard NSTC system (communication with the current standard) is not only possible with the current receiver, but also VTR and It has the great advantage of being able to record high-definition TV signals directly on video discs, etc., and seems to be particularly excellent. For example, as a technique of this kind, there is a document "Proposal of a high-definition TV system having complete communication" (Technical Research Report of the Institute of Electronics and Communication Engineers, CS-83, 61 July 1983). This is as shown in the side view of ν (vertical frequency) -f (temporal frequency) in FIG.
Paying attention to the fact that the color signal is in the second and fourth chapters and the first and third chapters are vacant, as shown in the figure (b), new information Y _H ( The high frequency component of the luminance signal Y) is frequency-shifted and inserted as Y _H ′. In other words, a high-frequency component Y _H of the luminance signal is frequency-converted to form a low-frequency signal Y _H ′, and frequency interleaving is performed between the original luminance signal Y and the chrominance signal and embedded. Is. However, the high-frequency component Y _H of the luminance signal is a minute signal, and the color signal and the original luminance signal are signals of a relatively large level, and the Y _H ′ is a signal between the original luminance signal Y and the color signal. When a signal embedded by frequency interleaving is separated on the receiving side, it cannot be completely separated. This causes mutual interference, which causes a problem that the image is deteriorated. In particular, with regard to the moving image mode, such deterioration appears remarkably, and it cannot be said to be a completely excellent method as a high-definition TV system compatible with the current standard NTSC system. (Problems to be Solved by the Invention) As described above, in the prior art, a signal obtained by frequency-converting a small high-frequency component Y _H into a low-frequency signal is embedded between high-level signals (luminance / color signals) as heterogeneous signals. Therefore, mutual interference occurs during separation and reproduction on the receiving side. For this reason, it was not possible to solve these problems and to completely realize a high-definition TV system compatible with the original standard NTSC system. The present invention has been made in view of such a current situation, and an object thereof is that the above mutual interference is extremely small,
Moreover, it is to provide a new image signal transmission system adopting a high-definition TV system compatible with the standard NTSC system.

Configuration of the Invention

(Means for Solving Problems) This invention focuses on the fact that a standard television signal transmitting device is transmitted by vestigial sideband amplitude modulation (VSB / AM), and is effective for a signal orthogonal to a carrier wave. The carrier suppression VSB · AM is performed after subtracting (adding negative) the low-frequency signal (Y _H ′) of the band signal and the signal induced in the quadrature component generated on the receiving side. That is, according to the present invention, the first means for generating a standard television signal based on the input image signal and the second means for converting the high frequency component signal of the luminance signal included in the image signal into the low frequency range. A third means for generating a signal of a quadrature component of the luminance signal included in the image signal, a first combining means for combining the signals from the second and third means, and a signal combined by this means. Amplitude-modulating means for amplitude-modulating the signal with a signal orthogonal to the carrier wave; second amplitude-modulating means for amplitude-modulating the signal generated by the first means with the signal of the carrier wave; The second combining means for combining the signal amplitude-modulated by the second amplitude modulating means and the carrier signal, the means for transmitting the signal combined by this means through the VSB filter, and the signal transmitted by this means. Receiving means to receive Includes, and is characterized in that the signal of the quadrature component of the luminance signal included in the image signal which cancels almost unnecessary signal components occurring in the receiving means is generated from the third means. (Function) A signal of a quadrature component of a luminance signal in an image signal which substantially cancels out an unnecessary signal component generated in the receiving means is generated by the third means without embedding a baseband signal between different kinds of signals, and By adopting a new method that cancels unnecessary signal components generated by the receiving means, there is no mutual interference when separating signals on the receiving side,
Moreover, the high frequency component of the luminance signal can be transmitted through the same transmission line as the current standard NTSC / TV signal. (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 2 is a system configuration diagram of a television signal transmitting side. The RGB signal of the image projected by the camera is V
The data is recorded in recording means such as TR and is converted into an NTSC signal by an NTSC encoder and transmitted by an antenna via a transmitter. At this time, it is properly monitored by the monitor. The present embodiment relates to a montage (MOD) added to the NTSC encoder. It is assumed that the transmitter converts the baseband signal into an RF band signal and transmits this signal. FIG. 1 is a basic configuration diagram of a television transmitting apparatus according to an embodiment. It should be noted that, in order to clearly show the characteristic, the characteristic portion is given a thick line and the current portion is surrounded by a dotted line. Video 3 primary color signals (R, G,
B) is applied to the input terminal 10, and these signals (R, G, B) are converted into digital signals by the analog-to-digital converter (A / D) 11, respectively, and the luminance signal Y, color difference signals I, Q It is input to a matrix 12 for generating Y, I and Q signals which generate signals. Here, each of the digital signals is a luminance signal (Y) obtained by weighting each of the three primary color signals of R, G and B and adding them, a signal obtained by subtracting the R signal and the Y signal, and a B signal.
Two color difference signals (I,
Q) and sent to the next stage. First, I and Q signals will be described. The part surrounded by the dotted line is conventionally known as an NTSC signal generator. The I and Q signals are input to low-pass filters LPF20 and 23 having bandwidths of 1.5 MHz and 0.5 MHz, respectively, subjected to band limitation, and then input to mixers 21 and 24, respectively. Also, the 3.58 MHz fsc output from the one-color subcarrier signal generator 25 is input to the mixer 21, and the mixer 24
Fsc that has passed through a phase shifter (for example, a phase shift angle π / 2) 26 is input to, and the I and Q signals are AM-modulated and become AM waves, which are input to the adder 22. The input signal to this adder 22 is
The phase of the fsc phase shifter (e.g. Q = 147 °) color burst signal obtained by phase shifting by 28, the horizontal synchronization signal f _H, signal from the synchronization signal generator SYNC27 for generating a vertical synchronizing signal f _V (f _V , f _H ) and a voice FM wave (for example, 4.5 MHz) from the FM signal generator AVDIO37 are added. Further, the Y signal whose band is limited by the LPF 29 of the block shown by the bold line is also added. The output of the adder 22 thus added is the low-pass filter LPF.
(For example, band 4.2 MHz) 36 is band-limited and converted to a normal NTSC signal (g (t) shown in the latter stage) by digital-analog converter 41. Next, the characteristic part of this embodiment will be described. Y mentioned above,
The Y signal output from the matrix 12 for generating the I and Q signals is equalized in amplitude by the amplitude flattening equalizer 13 to flatten the band characteristic. The amplitude reduction due to the backlash of the original signal of the correction term shown in the latter stage is as shown by the broken line in FIG.
The practice is the characteristic when the band of the correction term is up to 0.5 MHz. That is, this portion must be flattened. One output of the Y signal whose band characteristic is flattened is input to a bandpass filter BPF (for example, band 4.2 to 5.2 MHz) 14 and the other is input to a lowpass filter LPF (for example, band 4.2 MHz) 29. As shown in Fig. 4 (a), from BPF14, 4.2
Sub-sampler 15 for Y signal band-limited to ~ 5.2MHz
Output to the sub sampler 15 as shown in Fig. 4 (b). Is input from the outside and has an offset of 1/2 horizontal sync signal frequency in a form in which the band of this input signal is reversed,
Frequency interleaved with the original input signal. Next, as shown in FIG. 4 (c), this output is a signal having an integer multiplication of the horizontal synchronizing signal in the mixer 16 and an off-set of the horizontal synchronizing signal frequency of 1/4. The frequency is converted by the multiplier 16 by
The filter LPF (for example, band 0.5MHz) 17 is input to the fourth
As shown in FIG. 3D, a low frequency converted signal (Y _H ′) of the high frequency component of the Y signal is obtained. Here, the case where the band is extended by 1 MHz from the present is considered, and the above is summarized. FIG. 4 shows the processing of the ω _H component (video signal high frequency component) at that time.
The output of BPF14 is ((a) in the figure), and frequency interleaving is performed by sub-sampling ((b) in the figure).
Frequency conversion is performed using a carrier having an offset of 1 / 4f _H (horizontal synchronizing frequency) (FIG. 7 (c)), and a low-frequency conversion ω _H ′ component is created (FIG. 3 (d)). This puts the bandwidth in 0.5MHz. Then, the low-frequency converted signal (Y _H ′) is adjusted in amplitude in the signal level adjuster 18 to eliminate a noise component, and is input to the adder 19. On the other hand, the output of the amplitude flattening equalizer 13 is input to a low-pass filter LPF (eg 4.2 MHz) 29 (FIG. 5 (a)), and the output of the band-limited Y signal is added by the adder 22 described above.
Is input to the mixer 30 (the same figure (c)),
Here, the local carrier signal (f _cL ) generator 34 (FIG.
The frequency is converted by f _cL , and this output is input to the mixer 32 through the VSB filter (Nyquist type) 31 ((d) in the figure), where it is phase-shifted by the phase shifter (π / 2) 35. are synchronous detection at the output of the local carrier signal f _cL, this output is taken as the orthogonal component of the Y signal in a low pass filter LPF (e.g. bandwidth 0.5 MHz) 33 (FIG. (e)). this signal g shown later _β Corresponding to (t) The characteristic of the filter 31 is set so that the quadrature component generated on the receiver (R _x ) side is created in advance on the transmitter side and transmitted with the inverse characteristic, and the receiver unit cancels the unnecessary quadrature component. The characteristic is shown in Fig. 3. The Y _H ′ signal output from the signal level adjuster 18 and the signal having the inverse characteristic of g _β (t) are combined in the adder circuit 19. The analog / digital converter D / A38 Is returned to the signal. This signal is equivalent to showing later (t). This (t) contains the signal of the inverse characteristic of Y _H 'signals and g _beta (t). Then D described above / A38 of the output signal (t) in mixer 39 is a first amplitude modulation means, a carrier signal (f ₀₎ f ₀ is the phase shifter of the generator 43 (π / 2) 44 addition is frequency converted through Input to the device 40. Also, the output signal g of the D / A 41
_A signal obtained by phase-shifting the Y, I, Q signals that are _β (t), the audio signal, the synchronization signal, and the color subcarrier signal is generated by the carrier signal (f ₀ ) generator 43 in the mixer 42 that is the second amplitude modulation means. of
The frequency is converted by f ₀ and the result is input to the adder 40 which is the second coupling means. The f ₀ is also directly input to the adder 40 which is the second coupling means. The output signal from the adder 40 which is the second coupling means passes through the VSB filter 45 and is propagated as a broadcast wave by the power amplifier HPA46. When the propagated signal is received by the receiving side, _β (t) is generated as an unnecessary signal.
_Since a signal having the inverse characteristic of _β (t) is generated and transmitted,
It is possible to realize a system that is canceled by each other and is not affected by unnecessary signals. Here, the signal output by passing through the VSB filter 45 corresponds to S (t) shown in the subsequent stage. Next, the operation principle of the above-described embodiment will be described in detail using mathematical expressions. First, prior to the explanation, the signals used below are shown (including those sequentially shown above and also shown in FIG. 1): g (t): original video signal _gβ (t): generated in carrier quadrature component video signals to (t): the correction signal _{β (t): β} signal generated in the quadrature carrier component to (t) w _c: carrier angular frequency a _m: AM modulation index w _s: video signal angular frequency w _H ': Y signal Low-frequency conversion (Y _H ′) of high-frequency component (YH) of
The VSB filter (not shown) on the receiver side in the case of the NTSC radio wave of the angular frequency standard has the same characteristics as the Nyquist VSB filter 31, and its output signal S _β (t) is S _β (t) = {1-
_{a m · g (t)}} cosw c t-a m g β (t) sinw c t ... (1) shows the fit. Now, g as an input signal In the range of 0 <w _s <β, equation (1) becomes Is shown. However, as shown in FIG. 2, it is assumed that | w _s | <β is a straight line. Now, the correction signal (t) is modulated with an orthogonal carrier and the original
When added to the NTSC radio signal, the signal shown in equation (3) is obtained at the output of the VSB filter on the receiver side. So now And substitute it in the above equation (3) Get. Since we are thinking in the range 0 <w _s , w _H <β, Next, the above equation (4) is approximately S '(t) = {1 -a m A 1 cosw s t} cosw c t-B 1 cosw H'
_{t · sinw c t ... (5} ) may safely as. That is, the high frequency component of the Y signal can be generated in the orthogonal carrier of the second term of the above equation (5). That is, it becomes possible to independently extract the low-frequency converted high-frequency video signal component from the orthogonal component. At this time, the correction term returns to the in-phase component by A ₁ (W _s / β) ² cosw _s t, so that the original video signal g (t) is Since it is necessary to equalize the amplitude and flatten the band characteristic, as shown in, the amplitude flattening equalizer 13 is provided in this embodiment as described above. Furthermore, an interfering wave of B ₁ (W _H ′ / β) sinw _H ′ t will be mixed in, but if some attenuation (B ₁ ′) is applied to B ₁ , the saddle sample wave (1 / 4f Since it is also the offset of _H ), it has no effect. (Sub-sampler 15 in Figure 1
And mixer 10) By the above, synchronous detection (in-phase) on the receiver side Synchronous detection (quadrature component) Is obtained. That is, if the detection method on the receiving side is set to the synchronous detection type, if the level of the low frequency conversion high frequency component is adjusted as described above, it is possible to extend about 1.0 MHz from the current 4.2 MHz band. The above-mentioned configuration has been described as a digital signal processing format having the analog / digital converter 11 and the digital / analog converters 38 and 41 as input / output.However, when the entire configuration is processed by analog signals, the analog / digital conversion is performed. vessel
It goes without saying that the digital / analog converters 38 and 41 are not required. Although the embodiment of the present invention describes the case of the NTSC signal, it goes without saying that the same processing technique can be applied to the case of the PAL signal and the SFIAM signal.

【The invention's effect】

According to the present invention, mutual interference on the receiving side can be greatly reduced, and the same transmission line as the standard NTSC-TV signal currently implemented is used to transmit a high-definition TV signal by using the high frequency component of the luminance signal. Therefore, it is not necessary to transmit on a separate channel, and the transmission line that has been used conventionally can be shared for transmission of standard NTSC TV and high-definition TV. Since a high-definition television signal can be transmitted, the frequency band can be effectively used.

[Brief description of drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention, FIG.
Figure shows the system configuration of the video signal transmission side, and Figure 3 shows VSB.
Shows the characteristic of the filter, FIG. 4 is a diagram showing the processing of the video signal high-frequency component (w _H component), Fig. 5 LPF, f _{cL 'Shikisa,}
FIG. 6 is a diagram showing outputs of a VSB filter and an LPF, FIG. 6 is a diagram showing attenuation of original signal amplitude modulation by a correction term, and FIG. 7 is a diagram for explaining a conventional example.

Claims (3)

(57) [Claims] 1. A first means for generating a standard television signal based on an input image signal, and a second means for converting a high frequency component signal of a luminance signal included in the image signal into a low frequency range. A third means for generating a signal of a quadrature component of a luminance signal included in the image signal; a first combining means for combining the signals from the second and third means; A first amplitude modulation means for amplitude-modulating the generated signal with a signal orthogonal to a carrier wave; a second amplitude modulation means for amplitude-modulating the signal generated by the first means with the carrier wave signal; And second combining means for combining the signal amplitude-modulated by the second amplitude modulating means and the signal of the carrier wave, and means for transmitting the signal combined by the second combining means through a VSB filter, Transmitted by means Receiving means for receiving a signal, the signal of the orthogonal component of the luminance signal included in the image signal which substantially cancels the unnecessary signal component generated in the receiving means is generated from the third means. Image signal transmission system. 2. The image signal transmission system according to claim 1, wherein the signal of the high frequency component of the luminance signal included in the image signal is generated by frequency interleaving its own signal. 3. The image signal transmission system according to claim 1, wherein the signal induced in the signal orthogonal to the carrier wave is band-limited.