JPS58205380A - Eliminating circuit of energy spread signal - Google Patents

Abstract

PURPOSE:To prevent the deterioration in picture quality, by feeding back an output of a low pass filter passing a signal component of a frequency band of an energy spread signal negatively so as to suppress the energy spread signal. CONSTITUTION:A received demodulating output video signal including noise component and on which the energy spread signal is superimposed is led to a video amplifier 7 via a subtractor 6, it amplified output signal is applied to a clamp circuit 8 and a phase inverter 9 in parallel, and outputs of the circuits 8, 9 are applied to a synthesizer 10, where the signals are synthesized. This synthesized output is led to the subtractor 6 via the low pass filter 11 and an attenuator 12 sequentially and subtracted from an input picture signal, and an amplified output signal of the video amplifier 7 is extracted as the output video signal eliminating the energy spread signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the spectral energy Y of television's gN star broadcasts: an energy dispersion signal for dispersing within the firefly region, and an energy dispersion signal for removing it from received broadcast radio waves. With regard to the first (b) path, there is one thing that can be done to prevent quality deterioration due to noise generated during reception of a 1-weak electric field.

-N, in television satellite broadcasting, broadcasting
In order to disperse the wave spectrum energy as uniformly as possible within the energy broadcasting area, the television signal is placed in another energy shield No. 15 such as a triangular box, and then F
It is broadcast on M Hi-Shirami.

The triangular wave for energy dispersion is typically 15-30Hz.
It is necessary to remove this triangular wave for energy diffusion from the receiving layer 1. Since this energy spread signal has a much lower frequency component than the video signal spectrum, the signal level at the top of the synchronization signal is 1. Alternatively, by holding it at a constant level using a pedestal level clamp circuit, the energy diffusion signal 7 which is added to the video signal is lost.

The configuration of such a conventional energy spread signal removal circuit χ#I
Shown in Figure 1. In this conventional (b) route, the received F
Image signal obtained by demodulating with M-wave large input FMuI modulator l - @t
% video amplifier moss to the clamp circuit J, and the above-mentioned constant level is clamped by the circuit to change the signal level by 1 tatami of the triangular wave for energy diffusion11. After suppressing the
Take it out as a video signal output through the translation amplifier q.
Such a conventional energy dispersion No. 4cx-large circuit.

Energy dispersion (No. 1 can be removed sufficiently, but the received electric field is weak and noise is mixed into the FM Atsushi input, resulting in a demodulated image (
No. 4 8/N is a core 4! The table has a Note 1 in which the noise of the high-frequency mantissa component of the noise component > r is converted into the noise of the low-frequency ridge component using the clamp hJJ.
In addition, as mentioned above, if the eccentric output force is simply clamped to a constant level, 1 this will produce low-frequency horizontal noise ρ, which is so-called line noise, and the drawback is that the low-frequency noise that is particularly noticeable increases. There's one. The reasons for this noise are explained below.

Two examples of conventional clamp circuits (Figure 2 CA) and LB)
Nibosu. The beak clamp circuit shown in Figure 2 (A) is as follows:
Combined condensate? Cc, diode 1) consists of an input/output resistor R1r kL*. 10 N as shown in Figure λ CB)
The shaped lamp circuit consists of input resistance R,% coupling capacitor Cc
, diode D, and Da, resistor ax 1R3, R
4k; J: positive and negative pulses σ) input combination capacitors Cpp and Cpn J-.

To these clamp circuits, as shown in FIG. 3(A), an unnecessary signal of amplitude V consisting of an energy diffusion signal, noise, etc. is supplied with a video signal VWY. When the frequency fu of the unnecessary signal DW is sufficiently lower than the horizontal synchronization frequency that is the clamp period, the amplitude V of the unnecessary signal UW increases on the output side of the amplifier circuit 5, as shown in FIG. yvty</). That is,
At 1t-t, the clamp circuit 5 is charged with a reverse voltage of v'=v(/-y) in the L coupling capacitor Cc, which acts to cancel the unnecessary signal UWY. Here, the theoretical value of the value y is as follows.

TN Here, TN: Clamp pulse duck Tr: Horizontal synchronization period 'l'c: Cc-)L R: Series resistance during 4 clamp pulses For example, Cc = /l00pF, K = /, /k
Unnecessary signal pressure in case of Q &i! When the frequency 1, that is, the noise attenuation -AU is made longer, the noise frequency FU becomes significantly poorer as shown in FIG. Once, the lower intermantissa was jj
In this case, the noise damping lid Au becomes a large spear, but as the island area circumference mantissa becomes smaller, the value becomes smaller.

However, in the case of the noise reduction test Au, the noise frequency fu becomes even higher, and when the noise frequency becomes fu2,
As the I value y becomes smaller, it becomes a larger value. This means that according to equation (1), the logic tM region y is horizontally open M synchronization Ill
This is because it is a rD circumference lJJ function, and fu =
= n/Tr L n = 0. /, λ, −・・
It seems that the noise is sufficiently reduced in the vicinity of the frequency of = ), but this attenuation is due to the fact that only the change in the level of the clamping position when the pulse of the clamp circuit 5 is conducted is compressed. −1, the noise generation is ′
7 (not compressed at all), noise L
In addition, since the trace force applied to the coupling capacitor R9 is held only during the horizontal synchronization period Tr,
Based on the noise component 5f with a frequency of fu ``''±Δf, a noise component with a frequency of NJi of fu−Δf is generated at a new location and becomes 1 here due to the clamping action.

The manner in which such new noise components are generated will be explained in detail with respect to FIGS. S and FIG. 7 In this case, when the clamp circuit advances the pulp, a noise with an amplitude corresponding to the same potential V is detected, so that the output side of the circuit 5 is yv. A direct current voltage is generated. When the noise frequency fu matches the clamp period), the value of the noise ablation width V appearing in the pulse conductor aH8 of the clamp circuit is a constant value added by the phase angle θ of the noise waveform, as shown in Fig. 5. Become. Next, when a noise component NW with a frequency of % fu = T and Δf is supplied to the clamp circuit j, the noise m wave number fu deviates from the clamp period Tr by Δf, so the noise detection potential S at the time of pulse conduction of the clamp circuit gradually changes in accordance with the deviation in the number of cycles Δf, and a reverse voltage having a magnitude corresponding to the change in the noise detection potential is held in the coupling capacitor Cc. As a result, as shown on the output side of FIG. 6, a low frequency noise component having a fundamental frequency Δf is newly generated. Assuming the amplitude of this new noise component to be V', v'=ma(/-y), so how long will it take for the clamping effect to be completed?
, and v' approaches Ma. Therefore, in order to completely eliminate the energy spread signal by the clamping effect, if the canceling circuit is configured to increase the effect of the clamping effect, the amplitude V' of the newly generated low-frequency noise fraction will increase. It will end up being put away.

The manner in which the new low-frequency noise components are generated as described above is represented by L circuits shown in FIG. 7 using an equivalent circuit. That is, the frequency Δ
The noise component from a new noise source MS, f is,
The noise component from the noise source NS1 with the frequency fu included in the input signal is eli-sampled into two pump pulses and detected noise is generated in series to the coupling capacitor Cc as a voltage with the opposite sign to the pressure value. become.

As described above, in the conventional energy diffusion signal removal circuit consisting of a simple clamp circuit, the more a sufficient removal effect can be obtained, the more fu = -! -(n=8-1
One drawback is that the signal-to-noise ratio of the reproduced image deteriorates rather sharply because a new low-frequency noise component is generated from the noise component near the frequency r.

The object of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology.

Not only can it sufficiently remove the energy diffusion noise superimposed on the optical image signal, but it can also completely prevent the generation of the low-frequency noise component that has conventionally occurred. The goal is to provide information.

That is, the present invention includes an energy diffusion signal,
a first synthesis circuit that synthesizes the image input signal and the reduced signal;
a clamp circuit that Y-clamps the synthesized signal from the first synthesis circuit; a phase inversion circuit that inverts the phase of the synthesized signal; and a second synthesis circuit that Y-synthesizes the phase inverted signal with the output signal of the clamp circuit; a low-pass filter for passing at least signal components in the frequency band of the energy spread signal to be filtered by the second synthesis circuit; - It is characterized in that it is supplied to the synthesis circuit in the form of negative feedback to suppress the energy spread signal.

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

First, an example of the circuit configuration of the removal circuit of the present invention is shown in FIG. In the illustrated configuration example, the received demodulated output video signal containing noise components and further superimposed with an energy diffusion signal is guided to the video intensifier 7 via the subtracter 6, where it is appropriately amplified, and the amplified output signal is subtracted. The circuits ry and ? are supplied in parallel to the phase inverter 9, and these circuits f, ? The output signals are supplied to the output signal combiner 10 and QIJA'd with each other.
The synthesizer is guided through a low-pass filter L/2 and an attenuator/2 to a subtracter B, where it is subtracted from the image signal and the amplified output signal of the video amplifier 7 is removed from the energy spread signal. Extract as an output isthmus image signal. It is assumed that the input video signals of the video amplifier have the same polarity (+), and hereinafter, each circuit is assumed to have the same polarity as shown in the figure.

The effects of energy diffusion signal removal using the above-mentioned circuit configuration will be explained. When the energy diffusion signal is supplied to the superimposed amplified output video signal clamp 1, the energy amplification signal is removed from the clamp output video signal in the same manner as described above for the conventional circuit. On the other hand, at the phase inverted output of the phase inverter 9, which also supplies the amplified output signal g1 with the energy spread signal (4) being 1 volt, the energy diffusion signal is 1 volt as it is.

(b) Since the outputs of paths f and 9 are opposite to each other, their video signals are differentially 8
As the combined output of the anti-gamma synthesizer/θ, the optical signal is canceled out, and the energy diffusion signal is mainly extracted. Such a combined output signal is filtered by a low-pass filter. When the energy spread signal is supplied to the subtracter B through an attenuator/2-in sequence with an appropriate reduction amount, the energy spread signal is negatively fed back to the input side of the video amplifier 7, and the energy spread signal superimposed on the input video signal is canceled out and removed. be done. Therefore, the L video signal is extracted from the video amplifier 7 with the energy diffusion signal removed.

In the signal processing process of such energy spread signal removal? Let's talk about the low-frequency noise component of the wave number Δf that originates from the unnecessary signal component.First, as shown in FIG. If an unnecessary signal of r Δf is mixed in, as shown in Figure 6 and Figure 7, the noise generation source N82 with frequency Δf is inserted in series with the clamp circuit/θ as shown in Figure 7. , and a low-frequency noise component with the opposite sign to the sample value of the unnecessary signal at frequency fu is newly mixed into the video signal.Therefore, as shown in Fig. 9, the unnecessary noise component at the original frequency fu Only the new low-frequency noise component -If with the opposite polarity is added to the image through the low-pass filter @// and the attenuator/2.
The signal is negatively fed back to the input side of the circuit 70, combined with the original noise component u in the input video signal, and applied to the clamp circuit 9 again. Therefore, when sampled again by the clamp pulse in the clamp circuit 9,
The sample value of the noise component of the frequency fu and the sample value of the low frequency noise component of the frequency Δf have opposite signs, and act on the canceling method 11. That is, negative feedback is applied to the low frequency noise component of frequency Δf.

Therefore, if the feedback loop gain YA in the circuit configuration shown in FIG. 1 or FIG. 9 is assumed.

The energy spread signal has a frequency f (E).

The Z component is +E6. f).

In other words, the noise component of the frequency Δf is reduced by 5, / + A tljf) by the conventional removal circuit of the present invention with the configuration shown in the j-th diagram. In addition, the low-pass filter in the paulownia filter example shown in Figure 1 has a custom-made pass band that allows only the energy spread signal to pass, so that the low-frequency noise component Δf is not added to the video amplifier 7 at all. You can also choose not to have one.

However, in that case, the low-pass filter should have a steep cutoff characteristic, for example close to 10 dB/octave, as long as it satisfies the negative feedback stability condition described in the circuit configuration shown in Figure R. Is it desirable?

Next, another example of the configuration of the energy spread signal removal circuit according to the present invention is shown in FIG. Here, the R
The structure is the same as the example shown in the figure, except that a differential amplifier/3 is used in which the subtracter 6, video amplifier 7, and phase inverter 9 are integrated; however, the input side of the differential amplifier/3 is Since the negative feedback input terminal and the video signal input terminal can be separated from each other in R, there is also the advantage that matching with the amplifier provided in front of this removal circuit is facilitated.

Next, still another configuration example of the energy spread signal removal circuit of the present invention is shown in FIG. In the illustrated configuration example,
In the configuration example shown in Figure 70, instead of the clamp pulse applied to the clamp circuit l, two differential amplification outputs of the differential amplifier /3 are used, and the switching of the clamp diodes DI+D2 is used. The combined content 9
The differential amplified output image of the one that is supplied to the clamping diode and clamped via the Ce capacitor (No. 6 and the bell) must be kept small at all times, so an attenuator ATT/N is connected in series with the connecting capacitor Cc. In addition, attenuator A
TT- is for aligning the two-man power of the 1M unit of the synthesizer 10, and ArTJ is for adjusting the amount of negative feedback.

As is clear from the above description, according to the present invention, in order to equalize the in-band spectral energy distribution of satellite broadcasting waves, the energy spread signal added to the video signal is removed from the received demodulated output video signal. In the energy diffusion polarization removal circuit for.

At 15 o'clock in the game world, I took over and sat down to pretend to be there.I suppressed the low frequency noise that was causing the deterioration and produced a good image. I can do it.

[Brief explanation of drawings]

Figure 1 shows the structure of the conventional A/L amplification signal removal circuit. #! Figure 2 (AJ grounder and CB) is also a peak clamp type used for that configuration? and a circuit diagram showing the construction of a balanced type clamp circuit, Figure 3L.
A) to C, D) are also graphs showing the low-frequency noise component EE compression in the clamp circuit in sequence, and the second figure is the characteristic curve that shows the shape of the low-frequency noise component compression. Figures 5 and 6 are respectively explanatory pictures of a new mode of low-frequency noise generation by the Kranzub circuit, and Figure 7 is an illustration of the mode of low-frequency noise generator such as Wfr. The isometric diagram shown in Fig.
σ) Equivalently shown bronch set diagrams, Figures 1 and 1, respectively, show other configuration examples of the energy dispersion signal removal circuit of the present invention. It is durable. l...7N repeater, λ, reference, 7...video amplifier. J, j, lr...clamp circuit, 6.-subtractor. D...phase inverter, 10...synthesizer, //
...Low pass filter, ll...Attenuator. 13...Differential amplifier, 8N, , 8N,
...Noise source, Cc・
・・Coupling capacitor, D, D, , D, ・・・Clamp diode, ATT/, ATTJ, ATTJ・
...Attenuator. Patent applicant: Japan Broadcasting Corporation λjT]! ,・ Angers 2

Claims (1)

[Scope of Claims] 1) A first synthesis circuit that synthesizes an image input signal including the energy diffusion signal X and a feedback signal, a clamp circuit that clamps the synthesized signal from the first synthesis circuit, and a phase inversion circuit that inverts the phase; a second synthesis circuit that synthesizes the phase inversion signal with the output of the clamp circuit;
a low-pass filter that passes at least signal components in the frequency band of the energy spread signal output from the second combining circuit; - An energy diffusion signal removal circuit characterized in that the energy diffusion signal is suppressed by supplying it to the sweet-acid circuit in the form of negative feedback. 2. In the removal circuit according to claim 1, the separate clamp ip! The circuit is composed of a flat pulse clamp circuit, and the synthesized signal is generated by the first synthesis circuit. Diffusion member removal circuit. Phantom IRF Claim 1. In the Mr2 ridge removal circuit, the circuit comprises the first combining circuit and a differential amplifier;
1il! The input signal is supplied to one terminal of the amplifier, and the feedback signal is supplied to the other terminal of the amplifier, and the input signal is input from the first output terminal of the amplifier, and the input signal is input from the second output terminal of the amplifier. An energy dispersion 1d removal l1g circuit characterized by reliable vkU output.