JPH05199432A - Energy dispersal signal eliminating circuit - Google Patents

Abstract

PURPOSE:To obtain a high produced picture quality by inputting the output of a selector circuit and the MUSE signal, on which an energy dispersal signal is superposed, to the negative input terminal and the positive input terminal of an analog subtractor respectively to perform substraction of a triangular wave. CONSTITUTION:An ATT 1 of a signal amplitude adjusting circuit 3 and an ATT 2 of a signal amplitude adjusting circuit 4 perform the amplitude adjustment in accordance with the energy dispersal signal amplitude for BS transmission and that for CS transmission respectively. An analog signal selector circuit 5 is so constituted that it selects one of two signals outputted from the ATT 1 (B) and the ATT 2 (4) and a ground GND. The output of the selector circuit 5 and the MUSE signal on which the energy dispersal signal is superposed are inputted to the negative input terminal and the positive input terminal of an analog subtractor 6 respectively to perform substraction of a triangular wave. Thus, energy dispersal signal components in the input MUSE signal are almost all eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy diffusion signal removing circuit of a signal demodulator for demodulating and reproducing a high-definition television video signal which has been band-compressed and transmitted.

[0002]

2. Description of the Related Art Broadband high-definition television image signals are currently N
In order to maintain compatibility with the transmission channel of TSC satellite broadcasting, the signal transmission rate at the transmission modulation side is 1 /
The signal is converted into a signal compressed to 4 (generally referred to as MUSE signal) and transmitted as an FM modulated wave. At that time, in order to avoid concentration of the FM modulated wave in the frequency spectrum, 30Hz called energy spread signal
The triangular wave signal of is superimposed. The video signal component on which the triangular wave signal is superimposed causes image quality interference on the reception demodulation side, and therefore must be removed at the pre-processing stage of the A / D converter of the signal demodulator.

Further, the superposition level of this energy spread signal is different between broadcasting satellite transmission (hereinafter abbreviated as BS transmission) and communication satellite transmission (hereinafter abbreviated as CS transmission), and is superposed in reproduction of a MUSE signal recorded on a disk. Not not.
Therefore, the signal demodulator side requires an energy spread signal elimination circuit corresponding to these MUSE signal types.

An energy spread signal removing circuit of a conventional signal demodulator will be described below.

First, (1) and (2) in FIG.
FIG. 7 is a waveform diagram showing an amplitude value and a superimposing level of an energy spread signal superimposed on an FM-modulated demodulated MUSE signal during S transmission. As shown in the figure, the amplitude level of the original MUSE signal is 400 mvp-p, but 23.5 mvp-p during BS transmission in (1).
At the time of CS transmission of p and (2), 86.3 mvp-p triangular wave energy spread signals are added and superposed, and the frequency in this case is 30 Hz which is equal to the frame frequency.

FIG. 3 is a block diagram showing an example of an energy spread signal removing circuit of a signal demodulator according to the prior art.
In this circuit, 1 is a clamp circuit, which is composed of a differentiating circuit composed of so-called capacitors and resistors and a clamp pulse controlled analog switch, and a clamped signal (MU) is generated by a clamp pulse S1.
The SE signal) is fixed to a predetermined DC level.

[0007]

However, since a differential circuit is basically formed in this circuit configuration, the triangular wave energy spread signal superimposed on the clamped signal is suppressed but not completely removed. The triangular wave is converted into a square wave signal having the same frequency that has been subjected to the differential processing, and the component of this square wave signal remains. This residual square wave signal component is proportional to the superposition level of the energy diffusion signal and appears as a vertical line disturbance on the reproduction screen after MUSE signal demodulation, and its strength is proportional to the amplitude level of the residual square wave signal. ..

The present invention solves the above-mentioned conventional problems by completely removing the energy spread signal superimposed on the MUSE signal at the time of BS transmission and CS transmission, and providing a vertical line on the reproduction screen after the MUSE signal demodulation. It is an object of the present invention to provide a high-quality reproduced image quality that does not disturb the image.

[0009]

According to the present invention, there is provided a constant current type integrating means for inputting a frame signal having a duty ratio of 50% and a frequency of 30 Hz generated as a processing timing signal of a digital signal processing section in a demodulator, Amplitude adjusting means for adjusting the integrated output signal of the constant current type integrating means into two signals having different amplitudes, selector means for selecting and blocking the two signals, and subtracting the integrated output signal and the MUSE signal. It is characterized in that a subtraction means is provided.

[0010]

According to the present invention, a triangular wave signal having the same phase and the same frequency as the energy spread signal superimposed on the MUSE signal can be generated from the frame signal, so that the addition or subtraction processing of the analog signal is superimposed on the MUSE signal. It is possible to cancel the generated energy diffusion signal and obtain a high-quality reproduced image quality without vertical line interference on the reproduced screen.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention. In FIG. 1, 2 is a constant current type integrating circuit, 3 and 4 are signal amplitude adjusting circuits, 5 is an analog signal selector circuit, Reference numeral 6 is an analog subtractor, and 7 is a clamp circuit. The constant current type integrating circuit 2 is composed of an operational amplifier, and is for keeping the amplitude linearity of the triangular wave signal which is the output signal S3 of this circuit good. On the other hand, the frame signal S2 which is the input signal of this circuit has a duty ratio of
50% is necessary to obtain a triangular wave signal similar to the energy spread signal. Therefore, this frame signal S
2 is 1/2 the field timing pulse of frequency 60Hz
It is obtained by frequency division, and as a result of 1/2 frequency division, a frame signal having a duty ratio of 50% and a frequency of 30 Hz is obtained. Since this frame signal is easily obtained from the inside of the MUSE signal demodulator circuit and is generated by the logic gate processing, an ideal input signal with a small processing delay time and a small timing phase error can be obtained.

As a result of the above, a triangular wave signal very similar to the energy diffusion signal can be obtained as the output signal S3 of the constant current integrating circuit 2. Therefore, in the subsequent processing, the subtraction processing of this triangular wave signal and the MUSE signal on which the energy diffusion signal is superimposed may be realized by the analog subtractor 6.

First, ATT1 of the signal amplitude adjusting circuit 3 is B
Corresponding to the energy spread signal amplitude during S transmission, the ATT2 of the signal amplitude adjusting circuit 4 is amplitude adjusted according to the energy spread signal during CS transmission. The analog signal selector circuit 5 is configured to select one of the output 2 signals of the ATT1 (3) and ATT2 (4) and the ground GND. The output of the selector circuit 5 is input to the negative side input terminal of the analog subtractor 6, and the positive side input terminal of the analog subtractor 6 has the energy diffusion signal superimposed on the MUSE.
A signal is input and the triangular wave is subtracted.

Here, the ground GND input to the selector circuit 5 corresponds to the MUSE signal reproduction from the package software or the like, and the reproduction MUS at these package sources.
Since the energy spread signal is not superposed on the E signal, the subtraction process using the triangular wave signal is not necessary. Therefore, the negative input terminal of the analog subtractor 6 is set to zero input. The selector circuit 5 has three functions of BS reception / CS reception / disk reproduction.
The figure shows the configuration for selecting the input modes of types (a), (a), and (c). The clamp circuit 7 is the A /
It works only to fix the input signal to the D converter to a predetermined value flow reference value.

[0016]

As described above, the energy diffusion signal removing circuit of the present invention is used as the optimum input signal of the constant current type integrating circuit for converting the frame signal easily obtained from the inside of the MUSE signal demodulator circuit into the triangular wave signal. Since it can be used, the energy diffusion signal component in the input MUSE signal can be almost completely removed only by setting the amplitude value of the triangular wave signal to the optimum value corresponding to each input mode and subtracting it. As described above, an excellent effect of removing the energy diffusion signal can be realized only by a simple analog signal processing circuit, and a high quality reproduced image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an amplitude value and a superimposing level of an energy spread signal superimposed on a demodulated MUSE signal that has been FM demodulated during BS transmission and CS transmission.

FIG. 3 is a block diagram showing an example of an energy spread signal removal circuit of a conventional signal demodulator.

[Explanation of symbols]

1, 7 ... Clamp circuit, 2 ... Constant current type integration circuit, 3
... Signal amplitude adjusting circuit (ATT1), 4 ... Signal amplitude adjusting circuit (ATT2), 5 ... Analog signal selector circuit, 6
… Analog subtractor.

Claims (1)

[Claims] 1. A constant current type integrating means for inputting a frame signal having a duty ratio of 50% obtained from a signal processing circuit of a MUSE signal demodulator and outputting an integrated output signal, and a plurality of energy spread signals having different signal amplitudes. Amplitude adjusting means for adjusting the amplitude of the integrated output signal, selector means for selecting one of the plurality of integrated output signals whose signal amplitude has been adjusted, and the selected and adjusted amplitude. An energy spread signal removing circuit comprising a subtracting means for performing a subtraction process on the integrated output signal and the MUSE signal on which the energy spread signal is superimposed.