JPS60250793A - Energy diffusing system - Google Patents

Abstract

PURPOSE:To eliminate beat interference on the picture and enable application to various kind of scramble systems in satellite broadcast of TV, by using triangular wave relating to short horizontal scanning period as a diffusion signal. CONSTITUTION:Signals that control timing of duty, flat part, rise part and fall part of triangular wave and clock signals are supplied from an encoder 1 to a counter 2. The counter 2 counts clock signals basing on the control signal, and makes counting until specified timing at counting gradient corresponding to the duty, and outputs triangular wave of the shape of formed digital signal. The output is D/A converted 3, and the amplitide is adjusted by a variable attenuator 4 and sent out adding to a transmission signal by an adder 5. The receiving side removes diffusion signals from received signals and takes out transmission signals.

Description

[Detailed Description of the Invention] [Technical Field] The present invention provides a method for performing satellite television broadcasting.
It concerns the energy dispersion method implemented.

In satellite broadcasting, the frequency band used for downlink (e.g. 12 GHz band) is shared by terrestrial fixed services, broadcasting services, etc., but it is easier to protect terrestrial fixed services from satellite broadcasting services. To do so, F
We decided to apply energy diffusion to make the spectral distribution of M television radio waves uniform, and according to current technical standards, the spectral power flux density measured in any 4KHz bandwidth is reduced by 22 dB compared to the power measured in the entire frequency band. It is assumed that there is.

The present invention aims to improve the diffusion effect compared to conventional methods in energy diffusion during such satellite television broadcasting.

[Prior art]

Traditionally, energy dispersion is based on the vertical scanning frequency of the preview image signal (80 Hz for the NTSC standard system, 50 Hz for the PAL system, 1125 lines for high definition television (HD
A triangular wave with a period related to 80Hz (TV) system, specifically 30Hz or 15H in the NT'SC system.
The z triangular wave was used as a spread signal and was superimposed on the television image signal. The frequency deviation at that time is eoOKH
z, this value satisfies the above-mentioned reduction in power flux richness by 22 dB. Furthermore, the effect of energy diffusion becomes greater as the amplitude of the superimposed triangular wave is increased, but if the amplitude is increased too much, interference will be caused to adjacent channels.

- J. Interference in television FM transmissions, such as in satellite broadcasting, appears as beat disturbances on the screen. When energy is diffused using a triangular wave of 30 Hz or 15 Hz as in the past, the beat frequency is also 30 Hz.
It changes at a frequency of Hz or 15) 1z, and this change is recognized as flicker on the television screen. this is,
Since the change is slow, if you visually evaluate the beat frequency where the interference is large, this will be a guide to screen interference.

The above can be expressed as a disturbance state as shown in FIG. In this case, as can be seen from the figure, the disturbance changes slowly, and when conventional energy diffusion was used, the beat stripes caused by the disturbance could clearly be seen moving.

〔the purpose〕

An object of the present invention is to eliminate the above-mentioned conventional drawbacks, to make the beat disturbance appearing on a television screen as inconspicuous as possible, and to provide an energy diffusion method that can be applied to various scrambling methods as described below. There is a particular thing.

Another object of the present invention is to provide an energy spreading method particularly suitable for FM transmission such as 1125-line HDTV using a time-base compression multiplex subsampling method.

[Key points of the invention]

In order to make beat disturbances that appear on a television screen less noticeable, the present invention uses a triangular wave associated with an extremely short horizontal scanning period as a spreading signal compared to conventional methods, and also time-division multiplexes a luminance signal and a chrominance signal. In order to be suitable for various types of television signals, the duty of the triangular wave (the time division ratio between the rising part and the falling part) is not necessarily 50% as in the past.

That is, the present invention forms a spread signal using a triangular wave having a period equal to the horizontal scanning period of a television image signal or an integral multiple thereof, and applies the spread signal to the television image signal so that the inflection point of the triangular wave is It is characterized in that it is synchronously superimposed so that it does not occur during the duration of the unit luminance signal or color signal constituting the television image signal.

Here, the triangular wave is defined to include one having flat parts corresponding to the horizontal synchronization period and clamp period of the television image signal.

〔Example〕

Time axis compression multiplexing (TCI) to be transmitted as shown in Fig. 2(a)
) signal as well as the waveform of the spread signal used in the present invention.
Shown in Figure (b).

That is, in this embodiment, the horizontal synchronization period and clamp period of the transmission signal are set at a constant flat level, and the color signal portion (C
It is a triangular wave that rises at 1, 02) and falls once at the signal portion (Y).

It will be explained below that the diffusion effect is improved by setting the period of the diffusion signal to be the horizontal scanning period or an integral multiple thereof. In other words, if the frequency of the spread signal is increased, for example, the repetition frequency is increased to a frequency corresponding to the horizontal scanning period, as shown in Figure 3, the fluctuation period of the beat disturbance that appears on the screen becomes shorter, which is less than the frequency that appears in the conventional method. The flicker-like interference will no longer be noticeable, and the interference will no longer be visually noticeable. To be more precise, at this time, a crepe-like beat interference pattern will appear on the screen,
Because the period of fluctuation is short, instead of looking at the peak of the interference as in the conventional method, we look at the average level. Therefore, the appearance of the beat stripes is much better than in the case of the conventional method shown in Figure 1. It will be improved.

Figure 4 shows that the TCI signal shown in Figure 2 (a) is
An example of the configuration of the transmission/borrow arrangement when FM transmission by satellite is performed by superimposing the spread signal (triangular wave) with the horizontal scanning period shown in b) is shown.

The TCI signal encoder 1 supplies the counter 2 with a control signal and a clock signal for controlling the duty cycle of the triangular wave and the timings of the flat part, rising part, and falling part. This counter 2 counts clock signals based on the control signal, performs counting up to a predetermined timing with a counting slope according to the duty, and converts the triangular wave in the form of a digital signal into an analog signal using a D/A converter 3. After converting the signal into a triangular wave, its amplitude is adjusted by a variable attenuator 4, added to the TCI signal by an adder 5, and taken out from an output terminal 6.

FIG. 5 shows an example of a configuration for removing the above-mentioned spread signal from a signal received on the receiving side to obtain a transmission signal (TCI signal). The received signal is applied to the synchronization signal and clock signal regeneration circuit 12 from the input terminal 11 to generate a clock signal and a control signal, and these two signals are supplied to the counter 13 to generate a digital signal with the same waveform as the triangular wave generated on the transmitting side. Create a triangular wave in the form of a signal. After converting this into a triangular wave of an analog signal by the D/A converter 14, adjusting the amplitude of the triangular wave by the variable attenuator 15, and subtracting it from the received signal in the subtracter 16, the spread signal can be removed. I can do it. The signal obtained above is Te
1 signal decoder 17 to restore a high-definition television signal.

In the above description, the spread signal is formed through digital circuits such as the counters 2 and 13, but it goes without saying that it may also be formed directly in an analog manner.

Next, a case will be described in which the energy diffusion method according to the present invention is applied to a scrambled TCI signal.

The scrambling method is a method in which the positions of the color signal (CI, C2) and spider signal (Y) are swapped within one horizontal scanning period, and the horizontal scanning period in which swapping occurs and the horizontal scanning period in which swapping is not performed are The determination shall be made using a pseudo-random signal. FIG. 6(a) shows the transmitted signal when the positions are simply swapped, and FIG. 6(b) shows the spread signal at that time.

In this embodiment, due to a simple position change, discontinuity occurs in the superimposed spread signal (see FIG. 6(b)), and the horizontal synchronization period or clamp period may be damaged.

Note that when the spread signal in FIG. 2(b) is used for the transmission signal in FIG. 6(a), the triangular wave changes from the rising part to the falling part in the middle of the luminance signal during the horizontal scanning period in which the positions are swapped. Therefore, if the removal of the spread signal on the receiving side is insufficient, it is likely to cause interference in viewing the television program.

In order to avoid this, as shown in FIGS. 7(a) and (b), during the horizontal scanning period in which the positions are exchanged, both the luminance signal (Y) and the color signal (CI, 02) are arranged in the time order of each signal. Make sure to place it with the front and back reversed. In this case, as can be seen from FIG. 7(b), no discontinuity occurs in the spread signal, and therefore the above-mentioned drawbacks such as damage to the horizontal synchronization period or clamp period do not occur.

In addition, in the above explanation, TCI is used as the transmission number.
Although we assumed a signal of the NTSC system, which is the current standard system, the horizontal synchronization period is flat, the horizontal retrace period corresponds to the rising part, and the signal period corresponds to the falling part. Of course, a triangular wave may be used as the spread signal.

Furthermore, the spread signal of the horizontal scanning period is flattened in the horizontal synchronization period and the clamp period in the case of the TC1 signal, and the N
In the case of TSC signals, the horizontal synchronization period is flat, but this means that if the spread signal is not removed sufficiently on the receiving side, the horizontal synchronization part and clamp level become unstable, resulting in a high-quality television image. This is because there is a possibility that the reproduction of the flat part becomes difficult, but if there is no such fear, this flat part may not necessarily be provided.

Furthermore, it goes without saying that the various triangular waves described above may have their polarities reversed.

In addition, in the method of the present invention, when beat interference originally occurs in FM transmission of television signals, the purpose is to make changes in the beat interference caused by energy diffusion less noticeable, so the triangular wave that is the spread signal is used. Of course, the period does not have to be one period of the horizontal scanning period, but may be a time length of a plurality of horizontal scanning periods (even in this case, a spread signal that changes sufficiently quickly can be obtained).

〔effect〕

By carrying out the present invention, the period of fluctuation of the beat disturbance appearing on the television screen is shortened, and energy diffusion can be performed with a much greater diffusion effect than in conventional systems. In addition, when the period of the spread signal explained in the example is set to the time length of one horizontal scanning period, the duty of the triangular wave that is the spread signal is not set to 50%, and the boundary (inflection point) between the rising part and the falling part is Moderation signal (Y
) and the color signal (C,,C2),
Even if the removal of the spread signal is insufficient on the receiving side, it is unlikely to cause visual interference.

In addition, when the transmission signal is scrambled,
Even if the scrambling is performed by simply exchanging positions, a sufficient spreading effect can be obtained without causing much interference to the transmitted signal. (See Figure 6) Furthermore, as in the embodiment shown in Figure 7, if the time sequence of the signals in the horizontal scanning period in which the positions are swapped is reversed, no discontinuity will occur in the spread signal. Completely good characteristics are obtained including the horizontal synchronization period and clamp period.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the state of beat disturbance by the conventional spreading method, and Fig. 2 (a) and (b) are TC transmitted by the present invention.
A signal waveform diagram showing the waveform of the I signal and the waveform of the spread signal. Fig. 3 is an explanatory diagram of the state of beat disturbance by the spreading method of the present invention. Fig. 4 is a circuit that superimposes the spread signal on the TCI signal according to the present invention. FIG. 5 is a block diagram showing an example of a circuit on the receiving side that removes a spread signal from a superimposed and transmitted signal according to the present invention; FIGS. 6(a) and (b) ) is a diagram showing an example of scrambling by simple position swapping, and Figures 7(a) and (b) are diagrams showing an example of scrambling in which the time arrangement of the signals is reversed in the horizontal scanning period with position swapping. It is. 1...TCI signal encoder. 2...Counter, 3...D/A converter, 4...
Variable attenuator, 5...adder. 6...Output terminal, 11...Input terminal, 12...
Synchronous signal and clock signal regeneration circuit, 13... Counter, 14... D/A converter, 15... Variable attenuator, 16... Subtractor, 17... TCI signal decoder. Patent Applicant Japan Broadcasting Association Agent Patent Attorney Aku Tani - Figure 3 Time Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A spread signal is formed by a triangular wave having a period equal to the horizontal scanning period of the television image signal or an integral multiple thereof, and the spread signal is applied to the television image signal by inflection of the triangular wave. An energy diffusion method characterized in that the dots are synchronously superimposed so that they do not occur during the duration of a unit luminance signal or chrominance signal constituting the television image signal. 2) The energy diffusion method according to claim 1, wherein the triangular wave has a flat portion corresponding to a horizontal synchronization period and a clamp period of the television image signal.