JPH09307828A - Beat component removal device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To effectively improve interference disturbance due to the same channel and the same offset. A pulse generation circuit (14) of an interfering wave detection unit (10)
Generates a pulse signal having a pulse width slightly narrower than the equalization pulse at the rising timing of the horizontal synchronizing signal separated from the video component f _V. Sample hold circuit 15
Detects the correction beat signal by sample-holding the tip portion of the horizontal synchronizing signal with the pulse signal supplied from the pulse generating circuit 14. The diode-type DC control attenuator 23 of the amplitude control unit 20 controls the video components f _V and D.
The beat signal for correction to which the C component is added is input, and the beat component included in the video component is inversely corrected to generate a video component that does not include the beat component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beat component removing device for removing from a television received signal beat components of other radio waves of the same channel and same offset mixed in the television received signal.

SUMMARY OF THE INVENTION According to the present invention, radio waves of another television broadcasting station or a relay broadcasting station of the same channel and the same offset are mixed in a received input wave of a television relay broadcasting station (hereinafter, relay broadcasting station). Then, when a beat disturbance occurs, paying attention to the frequency of this beat component being several kHz or less, detecting the received input wave, and then sampling the tip of the horizontal synchronization signal to extract only the beat component. By correcting the amplitude of the original television received input wave in the opposite direction with this signal, the amplitude component of the beat is removed to improve the image quality.

[0003]

2. Description of the Related Art When two radio waves of the same channel are received, a difference frequency between carrier waves of both stations appears as beat interference. In Japan, to prevent this beat interference,
An offset carrier system is adopted for the frequency of television radio waves. This offset carrier system is a system in which mutual carrier frequencies are shifted in order to reduce mutual interference between the same channels.

That is, when there is an interfering radio wave whose frequency is close to that of the desired reception wave, the reception electric field is amplitude-modulated by the difference frequency of the two radio waves and becomes a beat fringe on the screen. Now, if the carrier frequencies of the two stations are shifted by half or an odd multiple of the line frequency f _H , the density of the beat fringes will be reversed for each scanning line, canceling each other out, and becoming inconspicuous.

When the beat frequency is 1/2 of the horizontal synchronizing frequency, that is, 7.875 kHz, the degree of improvement in beat interference is greatest. However, in Japan, the improvement is somewhat sacrificed, but +10 kHz or -1 in consideration of interference between the three stations.
This ± 10, which is set to offset by 0 kHz
When an interfering wave separated by kHz is mixed, a device that removes the interfering wave by utilizing the frequency difference is put into practical use. This interference wave removing device is installed in a relay broadcasting station.

However, in this interference wave removing device,
Since waves having the same offset have the same frequency, it is difficult to detect and remove the interfering wave. Therefore, at the stage of station placement, the position of the receiving antenna and the transmission conditions are devised to prevent or prevent interference, but due to changes in environmental conditions, weather conditions, etc. Interference of the same channel and the same offset may occur in radio waves.

[0007]

As described above, as a method of improving the interference interference due to the same channel and the same offset, a countermeasure in the receiving antenna and a desired wave (a television broadcast wave which the relay broadcasting station is going to receive) Synchronous broadcasting, etc., in which the frequencies of interference waves (other television broadcasting waves that give interference) are made to coincide, are known, but a device that directly removes them at a relay broadcast station that has received interference waves has been put to practical use. Absent.

Among the methods according to the prior art, the improvement in the antenna system cannot be carried out unless some conditions are satisfied, and even if it can be carried out, the cost thereof is high.

In the improvement by the synchronous broadcasting, it is necessary to control the local oscillation device for both of the two relay broadcasting stations, resulting in a large system configuration and a high cost.

To solve the above problems, if there is a device capable of directly removing an interfering wave at a relay broadcasting station which is being disturbed, the structure is simple and the cost is low. However, since the beat frequency due to the same offset interference has a wide variation range from plus several kHz to minus several kHz, it is difficult to put such a removing device into practical use. It should be noted that the fluctuation of several kHz occurs due to the change of the internal oscillation frequency of the relay broadcast station apparatus (which is enlarged because it is multiplied) or the accumulation thereof.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a beat component removing apparatus capable of effectively improving interference interference caused by the same channel and the same offset.

[0012]

In order to achieve the above-mentioned object, the invention of claim 1 relates to the same channel mixed from a television reception signal to this television reception signal.
A beat component removing device for removing the beat component of another radio wave having the same offset, wherein the tip component of the horizontal synchronizing signal in the video signal obtained by demodulating the television received signal is sample-held to remove the beat component. It is characterized by further comprising: detecting means for detecting; and removing means for removing the beat component included in the video carrier by inversely correcting the amplitude of the video carrier of the television received signal by the detected beat component. It is a thing.

According to a second aspect of the present invention, in the beat component removing apparatus according to the first aspect, the removing means reproduces the carrier wave synchronized with the video carrier wave of the television reception signal, and the reproduced carrier wave. A means for performing balanced modulation with the detected beat component, and means for removing the beat component included in the video carrier by adding the signal obtained by the balanced modulation to the video carrier of the television reception signal. It is characterized by.

According to the above-mentioned structure, as the detecting means for detecting the beat disturbing component, attention is paid to the fact that the beat component is several kHz or less, and this is used as the horizontal synchronizing signal (15.7).
By generating a pulse that starts at the rising timing of 5 kHz) and sampling the leading end of the horizontal synchronizing signal, it is possible to extract only the beat component of the interfering wave without being affected by the image component of the desired wave. The extracted beat signal and the input beat portion of the television broadcast wave have substantially the same amplitude and phase. Then, a correction signal is created using this beat signal, and the amplitude component of the contained beat is removed by inversely correcting the amplitude of the television broadcast wave that has received interference.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> FIG. 1 is a block diagram showing the configuration of a first embodiment of a beat component removing apparatus according to the present invention.

The beat component removing apparatus 1 is mainly composed of an interfering wave (beat component) detecting section 10 and an amplitude control (inverse correction) section 20. The beat component removing apparatus 1 also includes an AGC amplifier 2 for controlling the gain of an input television reception signal, and a television reception signal output from the AGC amplifier 2 as a video component f _V and an audio component f _A. Demultiplexer 3 that separates the audio component f _A , an f _A level adjuster 4 that adjusts the level of the audio component f _A , and a distributor 5 that distributes the video component f _V to the interfering wave detector 10 and the amplitude controller 20.
And a synthesizer 6 for synthesizing and outputting the video component, which is inversely corrected by the amplitude control unit 20 and the beat component is removed, and the audio component f _A , the level of which is adjusted by the f _A level adjuster 4. .

The interfering wave detector 10 is an AM detector 11 for AM detecting the video component f _V in the television reception signal.
A divider 12 that distributes the demodulated video signal; a sync separation circuit 13 that separates the video signal supplied from the distributor 12 to extract a sync signal (horizontal sync signal); a monostable multivibrator (monomulti ), Is driven at the rising timing of the horizontal sync signal separated by the sync separation circuit 13, and generates a pulse signal having a pulse width slightly narrower than the equalization pulse.
A sample-hold circuit 15 for sampling and holding the video signal supplied from the distributor 12 by the pulse signal supplied from the pulse generation circuit 14, and a cutoff frequency of 5
A low-pass filter (LPF) circuit 16 that is set to kHz and filters the signal supplied from the sample hold circuit 15 to generate a smooth beat waveform, and a beat level adjustment circuit 1 that adjusts the level of this beat waveform.
7 and 7.

Further, the amplitude control section 20 outputs the DC voltage adjuster 21 for adjusting the DC voltage level added to the correction beat signal and the interference wave detection section 10 in order to provide an appropriate operating point. 2 for adding the DC voltage output from the DC voltage adjuster 21 to the beat signal to be generated
2 and a diode type DC control attenuator 23 for inputting the beat signal added with the video component f _V and the DC component supplied from the distributor 5 and inversely correcting the beat component contained in the video component. There is.

Next, the operation of the beat component removing device in the first embodiment configured as described above will be described.

The television received signal is sent to the AGC amplifier 2
After being gain controlled via the video component in the demultiplexer 3 f _V
Is separated into the voice component f _A. Separated video component f
_V is distributed by the distributor 5 to the interfering wave detection unit 10 and the amplitude control unit 20. The separated audio component f _A is level-adjusted by the f _A level adjuster 4 and then combined with the video component after being inversely corrected by the amplitude controller 20.

Image component f supplied to the interference wave detector 10
First, _V is AM-detected by the AM detector 11, and the detected signal (video signal) is distributed by the distributor 12 to the sync separation circuit 13 and the sample hold circuit 15.
The sync separation circuit 13 separates the sync signal from the video signal and supplies it to the pulse generation circuit 14. The pulse generating circuit 14 is driven by the rising edge of the horizontal synchronizing signal among the supplied synchronizing signals, and as described above, generates a pulse signal having a pulse width slightly narrower than the equalizing pulse and outputs the pulse signal to the sample hold circuit 15. .

In the sample hold circuit 15, the tip portion of the horizontal synchronizing signal in the video signal is sampled and held by the supplied pulse signal and the mixed beat component is detected. Since this beat signal has a stepwise waveform, it is shaped into a smooth signal by the LPF circuit 16, further level-adjusted by the beat level adjuster 17, and then output to the amplitude control circuit 20. Here, the level of the beat signal is adjusted so that the beat component included in the output signal of the device is minimized.

In the amplitude control circuit 20, first, the adder 22
Thus, the DC voltage is superimposed on the beat signal supplied from the interfering wave detection unit 10. Then, the beat signal on which the DC voltage is superimposed is supplied to the attenuator 23, where the gain of the video component f _V is controlled and the beat component is inversely corrected. The video component that has been corrected and does not include the beat component is re-synthesized with the audio component f _{A by the} synthesizer 6 and output.

FIG. 2 is a waveform diagram showing the state of beat removal. In the figure, the desired wave and the interfering wave are both unmodulated carriers (left column in the figure), and the desired wave is the modulating wave and the interfering wave is the unmodulated carrier. Waveforms of a wave, a received wave, a correction signal, and an output wave are shown.

In the above-described embodiment, the beat removal amount changes depending on the image level of the desired wave. As shown in FIG. 2, for example, when the level is adjusted by the beat level adjuster 17 so that the beat at the leading end portion of the horizontal synchronizing signal is minimized, a portion having a modulation degree of 50% and a white level (modulation degree 1
(2.5%), a considerable beat remains. This is a principle. This is because the interfering wave is added (or subtracted) regardless of the modulation degree of the desired wave, while the removal method is gain correction (corresponding to multiplication or division). Therefore, both the desired wave and the disturbing wave are 40-50%
The largest improvement is obtained by averaging and adjusting so that the beat is minimized. In the end, it is necessary to check the actual TV broadcast wave and make fine adjustments so that it looks best.

<< Experimental Results >> Next, experimental results in the circuit configuration of FIG. 1 will be described.

The disturbing wave is a carrier wave only, the amplitude ratio D / U (hereinafter, DU ratio) of the desired wave and the disturbing wave is set to 30 to 40%, and the improvement amount is changed by changing the image modulation level of the desired wave and the beat frequency. It was measured.

As a result, the DU ratio at the best point is 20 dB.
Although a value of the order of magnitude was obtained, the average value was 6 to 10 dB, and the worst values were 2 to 3 dB at the black level and the white level. The amount of improvement was almost constant with respect to changes in the DU ratio and beat frequency. An evaluation test was conducted on both the desired wave and the disturbing wave as ordinary television broadcast waves (programs), and an improvement of about half rank was obtained.

As described above, according to the first embodiment, the DU ratio can be improved with a simple device configuration, although the improvement amount is small.

<Second Embodiment> FIG. 3 is a block diagram showing a second embodiment of the beat component removing apparatus according to the present invention.

In the second embodiment, the structure of the interference wave detector 10 is the same as that of FIG. 1, but the interference wave remover 30 for removing the interference wave is the structure of the amplitude controller 20 of FIG. Different from Hereinafter, the configuration of the interference wave removing unit 30 will be mainly described, and the same components as those of the first embodiment shown in FIG. 1 will be assigned the same reference numerals and description thereof will be omitted.

The interference wave removing unit 30 includes a distributor 31 for distributing the video component f _V and a limiter circuit, and a carrier wave reproducing circuit 32 for reproducing a carrier wave from the supplied video component f _V.
And a phase adjuster 33 for adjusting the phase of the reproduced carrier wave.
A balanced modulator 34 that balance-modulates the phase-adjusted carrier wave with the beat signal supplied from the interfering wave detector 10 to extract only the beat component; and the beat component extracted by the balanced modulator 34. And a synthesizer 35 for generating a video component from which the beat component is removed by synthesizing the video component signal.

Next, the operation of the beat component removing apparatus according to the second embodiment having the above-mentioned configuration will be described with reference to the waveform chart of FIG.

The distributor 31 distributes the video component f _V supplied from the demultiplexer 5 into the video component signals e ₁ and e ₁ ′.
The image component signal e ₁ is supplied to the carrier wave reproduction circuit 32,
The video component signal e ₁ ′ is supplied to the synthesizer 35.

As shown in FIG. 4, the beat component is superimposed on the video component signal e ₁ output from the distributor 31. In the carrier wave reproducing circuit 32, this video component signal e ₁
The carrier wave is reproduced from. The phase of the reproduced carrier is adjusted by the phase adjuster 33, and the carrier e ₃ after the phase adjustment is supplied to the balanced modulator 34.

In the balanced modulator 34, the beat signal e ₂ supplied from the interfering wave detector 10 and the carrier e ₃ after the phase adjustment are applied.
Are input, and the carrier wave e ₃ is modulated by the beat signal e ₂ . As a result, a balanced modulated wave modulated by the beat signal can be obtained. The phase of this signal is the video component signal e
After the phase is adjusted so as to be opposite to the phase of ₁ ', it is supplied to the combiner 35 as the amplitude correction signal e ₄ .

The combiner 35 is supplied with the amplitude correction signal e ₄ and the video component signal e ₁ ′ having a phase opposite thereto. By synthesizing these, the video component e ₅ from which the beat component has been removed is provided. Is generated. The obtained video component is combined with the audio component f _{A by the} combiner 6 and output.

<< Experimental Results >> Next, experimental results in the circuit configuration of FIG. 3 will be described.

When only the carrier wave was used as the interfering wave, an improvement amount of about 15 dB was obtained regardless of the image modulation level of the desired wave. As a result of the evaluation test for both the desired wave and the disturbing wave as normal television broadcast waves, an improvement of about one rank was confirmed.

As described above, according to the second embodiment, the beat component is extracted by the balanced modulator 34, and the obtained beat component is added to the input video component signal. Alternatively, since it becomes a subtraction signal, it is possible to remove the beat component in the best state without depending on the image modulation level of the desired wave. For this reason,
Compared to the first embodiment, the number of high frequency circuits increases,
Although the configuration is slightly complicated, the effect of improving the interference wave is extremely large.

In each of the above embodiments, the low-pass filter (LPF) circuit 16 is provided in order to filter the signal supplied from the sample and hold circuit 15 to generate a smooth beat waveform.
The F circuit 16 may be omitted.

[0042]

As described above, according to the first aspect of the invention, the beat component can be effectively removed with a simple device configuration.

According to the invention of claim 2, the beat component is extracted by the balanced modulation, and the obtained beat component becomes an addition signal or a subtraction signal with respect to the input video component signal. The beat component can be removed in the best condition without depending on the image modulation level of the television reception signal, and the effect of improving the interfering wave becomes very large.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a beat component removing device according to the present invention.

FIG. 2 is an explanatory diagram showing an operation in the first embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration of a second embodiment of a beat component removing device according to the present invention.

FIG. 4 is an explanatory diagram showing signal waveforms of respective parts in the second embodiment shown in FIG.

[Explanation of symbols]

 1 beat component removal device 2 AGC amplifier 3 demultiplexer 5, 12, 31 distributor 6, 35 combiner 10 interfering wave (beat component) detection unit 11 AM detector 13 sync separation circuit 14 pulse generation circuit (mono-multi) 15 Sample-hold 16 Low-pass filter 20 Amplitude control section (inverse correction section) 21 DC voltage regulator 22 Adder 23 Diode type DC control attenuator 30 Interfering wave remover 32 Carrier recovery circuit 33 Phase adjustment circuit 34 Balanced modulator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takamitsu Yoshida 2-3 Kyomachi, Gifu City, Gifu NHK Gifu Broadcasting Station (72) Inventor Junichi Ando 1-66 Morisue-machi, Nakamura-ku, Nagoya, Aichi NHK Aitec Nagoya Branch Office

Claims (2)

[Claims] 1. A beat component removing device for removing, from a television reception signal, beat components of other radio waves of the same channel and the same offset mixed in the television reception signal, wherein the television reception signal is demodulated. Detection means for sampling and holding the tip portion of the horizontal synchronizing signal in the video signal obtained by detecting the beat component; and amplitude-inverse correction of the video carrier of the television reception signal by the detected beat component. A beat component removing device comprising: a removing unit that removes a beat component included in the video carrier. 2. The beat component removing apparatus according to claim 1, wherein the removing unit reproduces a carrier wave synchronized with an image carrier wave of the television reception signal, and the reproduced beat carrier unit detects the detected beat component. And a means for removing the beat component contained in the video carrier of the television reception signal by adding the signal obtained by the balanced modulation to the video carrier of the television reception signal. Component removal device.