JPS58100584A - Eliminating circuit for energy spread signal - Google Patents

Abstract

PURPOSE:To obtain a stable picture, by clamping the entire period of video signals with a uniform pulse, through the pulse clamp by means of synchronizing pulses with a narrow pulse width formed from vertical synchronizing signals at a differentiating circuit. CONSTITUTION:A signal from an input terminal 7 is branched into two at a distribution circuit 8; one is given to a peak clamp circuit 9 and the other is provided for a pulse clamp circuit 12. A signal subject to less level fluctuation of peak value of a synchronizing signal at the peak clamp circuit 9 is given to a synchronizing separation circuit 10, and the synchronizing signal picked up from the circuit 10 is narrowed for the pulse width of the vertical synchronizing signal at a differentiation circuit 11 and the pulse width for the horizontal and vertical synchronizing pulse is almost made equal with each other, and given to a pulse clamp circuit 12 as a gate signal. A signal eliminating an energy spread signal can be led from the circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for removing energy spread signals superimposed on television signals.

As is well known, the frequency modulation method is used in the television satellite broadcasting. In a frequency-modulated television signal, when the video signal component remains unchanged and becomes a 1iii plane close to 1@c, the energy of the sideband waves due to the synchronization signal pulse is concentrated near a certain frequency.

There is a risk that other communication systems may be affected.

Therefore, in the satellite broadcast television signal 11c, a 5081 triangular wave synchronized with the vertical synchronization signal is superimposed as an energy spread signal.

Therefore, in order to receive this broadcast radio wave with a TV receiver, it is necessary to remove this energy spread signal from the demodulated video signal.

FIG. 1 shows a television signal with M of spread signals. This spread signal 1 is a 50 Hz triangular wave and is superimposed in synchronization with the vertical synchronization signal 2 of the television signal. A diode beak 2271 circuit has conventionally been used as this spread signal removal circuit.

FIG. 2 shows a diode beak amplifier circuit. As shown in Figure 1, the peak clamp circuit is composed of a capacitor 4 in series and a diode 5 in parallel, and operates in a first-order manner. The signal input from the terminal 5 has its tip potential fixed at the voltage Ve supplied from the diode 5 by charging and discharging the capacitor 4 and switching operation of the diode 5, and an output signal is taken out from the terminal 6.

In this peak clamp circuit, if the capacitance of the capacitor 4 is selected to be large, the television signal on which the spread signal is superimposed is directly applied to the diode 5, and the spread signal cannot be removed sufficiently.

On the other hand, if the capacitance of the capacitor 4 is selected to be small, the amplitude of the spread signal can be made small by the capacitor 4, and the voltage at the tip of the synchronizing signal of the television signal can be maintained at a substantially constant voltage by the diode 5.

Then, a signal from which the energy spread signal has been removed can be obtained from the output terminal 6. However, capacitor 4 &c↓
If the value is selected so that the low frequency components of the video signal, for example, the energy spread signal, can be removed, the low frequency components in the vertical synchronization signal, which has many low frequency components, will also be removed at the same time.

As shown in FIG. 5, distortion occurs in the vertical synchronizing signal waveform, resulting in sag 2', which sometimes makes the synchronization of television images unstable.

In other words, in the conventional diode clamp circuit, if the capacitance of the capacitor is increased, the energy spread signal cannot be removed, and if the capacitance is reduced, the energy spread signal is removed, but the vertical synchronization signal Kt is generated. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit capable of eliminating the above-mentioned drawbacks of the prior art, faithfully reproducing an output waveform, and sufficiently removing energy spread signals.

The present invention will be explained below by way of examples. FIG. 4 is a block diagram showing one practical sequence of the present invention. In the figure, 7
8 is an input terminal, and 8 is a distribution circuit that branches the signal into two. 9
The Bee 22271 circuit, which is composed of a diode and a relatively large coupling capacitance, removes most of the energy diffusion signal superimposed on the Eirin signal and reduces level fluctuations in the peak value of the synchronization signal. Reference numeral 10 denotes a synchronization separation circuit which functions to extract a synchronization signal from the video signal in which the energy spread signal has been attenuated. Reference numeral 11 denotes a differentiator circuit, which is composed of a capacitor in series with the line and a parallel resistor, and removes low frequency components of the synchronizing signal. Then, the pulse width of the fi vertical period signal is narrowed, and the pulse widths of the horizontal and vertical synchronization pulses are made almost equal,
By applying it as a gate signal to a pulse clamp circuit, the energy spread signal is removed.

FIG. 5 is a circuit diagram showing a specific example of this embodiment. In the figure, the video signal transmitted from the input terminal 7 is branched into two by a one-way distribution circuit 8.

The first branch output is amplified by an amplifying transistor 19 and transmitted to a pulse clamp circuit 12 & C, which is constituted by a coupling capacitor t20, a transistor 21, and a resistor and capacitor (not numbered). transistor 2
The base V of 1 is connected to the differential circuit 11 via the synchronous separation circuit 10.
A waveform-shaped pulse is applied.

Further, the second branch output passes through the transistor 14 to the beam 2.
2271 is applied to the circuit 9. The B22271 circuit consists of a coupling capacitor 15 and a DC voltage source 17 (1) / (A clamp diode 14 with an Iasumi voltage applied), which calculates the amplitude of the energy diffusion signal superimposed on the signal. Make it smaller.

As described above, when the value of the coupling capacitor 15 is reduced, the amplitude of the energy spread signal becomes smaller, but this causes waveform distortion of the synchronizing signal. On the other hand, when the value of the coupling capacitor 15 is increased, the residual amount of the energy diffusion signal becomes larger, but the waveform distortion of the synchronizing signal becomes smaller. In this specific example,
Coupling capacitor 15&C relatively large value 1 e.g. about 2μ
Use a capacitor of about F. Although some residual portion of the energy spread signal remains, the synchronization period is ensured and the waveform distortion (sag) of the synchronization signal is reduced.

In this way, when a capacitor with a relatively large capacity is used as the coupling capacitor 15, some energy diffusion signal remains, but according to this embodiment.

It is possible to prevent adverse effects caused by this residual content. The inside of the venue will be explained below using FIGS. 6 and 7.

As shown in Figure 6 (α)K, the television signal is as follows:
It is composed of a horizontal synchronizing signal 24 having an amplitude of about 20% and a video signal component 2S having an amplitude of 80%. Also, * direct synchronization signal 26
As shown in FIG. 9, the pulse width of the horizontal synchronizing signal 25 is wider than that of the horizontal synchronizing signal 25.

FIG. 6 (Shun is the waveform of the next synchronization signal separated from the Eirin signal (eL). Transistor 2 of the pulse clamp circuit 12
The polarity of the synchronizing pulse applied to pace 1 needs to be opposite to the waveform shown in video signal (1), as shown in (h)K. Therefore, the vertical synchronizing signal 26 has a wide and flat portion where the pulse level is high.

When the output wave <h> of the synchronization separation circuit 10 is passed through the differentiation circuit 11, a vertical synchronization signal 26 is obtained as shown in FIG.
The pulse width at the upper end of the differentiated vertical synchronizing signal 270 is about the same width as the horizontal synchronizing signal 25.

Now, the energy diffusion signal that is the video signal component is attenuated when it passes through the pulse clamp circuit 12.
As shown in Figure (1), the minute amplitude d becomes the residual portion of the energy spread signal. If the value of this residual d is not attenuated below the detection limit with respect to the amplitude of the entire video signal, brightness and darkness will flicker on the screen.
This causes so-called flicker. Note that point P is the position of the vertical synchronization signal.

Now, hypothetically, if we apply the synchronization pulse without differential shaping, that is, the synchronization pulse shown in FIG. Ninth, the level at the tip of the vertical synchronization signal is fixed to a constant value.

In the past, even if the amplitude of the residual part of the spread signal was d, P
4 is fixed like po in Fig. 7(b).

If a synchronization error occurs, the vertical synchronization signal pg.

At the central points Qt and Qs IIC far from P#'.

The amplitude of the level fluctuation is larger than the residual d.

Its maximum amplitude is Ga. When such a level fluctuation occurs, points Qt and Q2 are located at approximately the center of the screen, so that it is easy to see a flicker disturbance on the screen.

On the other hand, if the voltage applied to the pulse clamp circuit 12 is shaped into a waveform by a differentiating circuit as shown in FIG. It is possible to be 2-mped. Therefore, the level at the tip of the vertical synchronization signal is not fixed to a constant value, and the level of the vertical synchronization signal is pl, pm.
, ps, the amount of d varies in response to the phase variation of the superimposed voltage. However, since the level fluctuation of the entire screen becomes the value d, flicker does not occur.

Further, since the clamping is performed using a uniform synchronization signal, there is little sag occurring near the vertical synchronization period, and a video signal faithful to the original signal as shown in FIG. 6(g) can be reproduced.

As described above, according to the present invention, since the entire period of the video signal can be clamped with a uniform pulse, level fluctuations due to residual energy of the energy diffusion signal in the video signal are reduced, and flicker interference is reduced. Less stable images can be obtained.

There is no sag in the sync signal, so the TV receiver 1s'I
A synchronization signal with less waveform distortion can be obtained within fJA.

-fI: This improves the stability of image synchronization.

Further, even when a multiplexed signal is superimposed on the synchronization signal, the multiplexed signal can be faithfully reproduced.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram of a television gene video signal on which an energy spread signal is superimposed, Figure 2 is a circuit diagram of an energy spread signal removal circuit composed of a conventional diode peak clamp circuit, and Figure 3 is a circuit diagram of a conventional circuit. FIG. 4 is a schematic diagram of an embodiment of the present invention; FIG. 5 is a circuit diagram showing a specific example of an embodiment of the present invention; FIG. 7 and 7 are signal waveform diagrams for explaining the circuit operation of the present invention. 9...Peak clamp circuit, 10...Synchronous minute circuit, 11...Differential circuit, 1
2...Pulse clamp circuit. 1st mouth; 'rz 膓 3rd mouth Figure 5 2 O Alfl Off [! 1 Z

Claims (1)

[Claims] (1) A distribution circuit that branches a television signal on which an energy spread signal is superimposed into two. 1. A pulse amplifier circuit to which the output of the first branch is input. 2. A peak clamp circuit to which the output of the second branch is input. , #A synchronization signal separation circuit into which the Eirin signal generated at the output end of the peak clamp circuit is input. and a differentiating circuit into which the synchronizing signal separated by the synchronizing signal IIIA circuit is input, and the pulse width of the direct synchronizing signal is narrowly shaped into the differentiating circuit, and a gate signal containing nine synchronizing pulses is provided. I'm busy adding to the human power side. Eliminates discontinuous fluctuations in the level at the tip of the vertical synchronization pulse, and extracts the image signal component with less fluctuation in the level at the tip of the vertical and horizontal synchronization signals from the output of the #pulse loop circuit. An energy diffusion signal removal circuit characterized by being dangerous.