JPS5831074B2 - Ghost Kansokuuchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for observing the state of ghosts in a television signal received by a television receiver or the like, and provides a device that can accurately and easily observe the state of ghosts. This is what we provide.

When receiving a television broadcast signal, reflected signals developed by objects such as buildings or mountains during transmission are often received as overlapping signals that directly arrive. A problem arises in that the signal becomes a ghost signal and a ghost image appears on the screen.

Therefore, as a means to reduce the negative effects caused by this ghost signal, the ghost signal is removed in the antenna system such as a diaperity antenna, and the detected video signal is delayed by the same amount of time as the delay time of the ghost signal so that it has an appropriate polarity and size. Many methods are known, such as one that cancels the ghost signal by adding it to the video signal that is not delayed, and one that removes the ghost component using a homogeneous detection circuit.

However, even if such a ghost removal method is implemented, it is necessary to accurately know the delay time, phase, and magnitude of the ghost signal, and it is also necessary to accurately know the state of the ghost signal, such as the delay time, phase, and magnitude. The ghost removal means must be adjusted while checking the state of the ghost.

However, in the past, the state of this ghost signal was observed by receiving a normal television broadcast signal and looking at the screen, but the contents of the screen were constantly changing, making accurate observation impossible and making adjustments difficult. The problem was that it became difficult.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an apparatus that can eliminate such conventional inconveniences and accurately and easily observe states such as delay time, phase, and magnitude of coast signals.

An embodiment in which the present invention is applied to a television receiver will be described below with reference to the accompanying drawings.

First, in order to easily observe the state of such ghosts, the transmitted television signal is superimposed with a pulse signal for ghost detection in any horizontal scanning period during the vertical retrace period, as shown in FIG. 5A. It is assumed that

The pulse width of this pulse signal a is made considerably narrower than the width of the horizontal synchronizing signal, and its position is superimposed at a portion slightly toward the front from the middle of the horizontal scanning period.

By narrowing the pulse width and selecting the position in this manner, reading during observation is easy, and observation can be made over a wide range of delay times.

Next, FIG. 1 shows the overall configuration of a device for receiving such a TenVision signal and will be described.

Here, 1 is an antenna, 2 is a tuner, 3 is an intermediate frequency amplification circuit, 4 is a video detection circuit, 5 is a video amplification circuit, 6 is a cathode ray tube, 7 is a chroma circuit, 8 is an audio circuit, and 9 is a speaker. , these are similar to those of ordinary television receivers.

Further, 10 is a ghost removal circuit for removing ghosts, and FIG. 2 shows a detailed configuration of a specific example configured in combination with the video detection circuit 4.

This ghost removal circuit 10 uses two synchronous detection circuits.
The signal is input to the first synchronous detection circuit 11 on the one hand.

The carrier wave regeneration circuit 12 for synchronous detection extracts the carrier wave (58.75 MHz in Japan) component from the VIP signal and shapes it into a single amplitude.

This is constituted by, for example, a tuned amplifier circuit or a PLL circuit.

The output of the carrier wave regeneration circuit 12 is added to the synchronous detection circuit 11,
As a result, the VIP signal is synchronously detected and a video signal is output.

On the other hand, the VIP signal is applied to the second synchronous detection circuit 14 via a variable delay line 13, such as a surface wave delay line with a tapped structure and variable delay time.

Here, the carrier wave is also regenerated by a similar carrier wave regeneration circuit 15, and the phase is controlled by a phase shifter 16 to an appropriate phase l, and then applied to the synchronous detection circuit 14.

The detection axis of this synchronous detection circuit 14 can be freely controlled by a phase shifter 16.

The detected output from the synchronous detection circuit 14 is sent to the variable delay line 17, further adjusts the delay time that could not be sufficiently controlled by the variable delay line 13, adjusts the magnitude using the gain control circuit 18, and then sends it to the adder circuit 19. In addition, ghost components are removed by adding the video signal of the detection output from the synchronous detection circuit 11.

At this time, the phase shifter 16 is adjusted so that the detection axes of the first and second synchronous detection circuits IL14 are shifted by the same amount as the phase difference between the desired signal and the ghost signal, and the magnitude thereof is adjusted. As a result, the ghost signal component included in the detection output of the first synchronous detection circuit 11 is transferred to the second synchronous detection circuit 14.
This can be removed by the desired signal component in the detected output.

Therefore, the objects to be adjusted are the delay times of the variable delay lines 13 and 17, the phase shift amount of the phase shifter 16, and the gain amount of the gain adjustment circuit 18. What is necessary is to observe the screen while receiving a and make these adjustments to remove the coast component.

Next, a portion for observing ghosts using such a pulse signal a will be explained.

As mentioned above, since the pulse signal a for ghost detection is superimposed on the horizontal scanning period during the vertical blanking period, it is not displayed on the screen of a normal television receiver as it is due to the blanking effect.

For this reason, conventional devices are configured to display images during the vertical retrace period of the television signal A.

In the conventional example shown in FIG.
In addition to the horizontal synchronizing signal separation circuit 23, a delay circuit 24 for delaying the phase of the vertical synchronizing signal is provided, and the deflection circuit 25 is controlled by the vertical synchronizing signal whose phase is delayed.

In this way, if the vertical synchronization signal is delayed, the cathode ray tube 6
The vertical position of the screen can be shifted, and the portion where the pulse signal a is superimposed can also be projected and displayed on the screen.

However, even with this display, the period in which pulse signal a can be superimposed is limited to several horizontal scanning periods during the vertical retrace period, so the images of pulse signal a and its ghost signal components are not displayed on the screen. However, it can only be displayed in a small portion and can be difficult to understand.

Therefore, in the device according to the present invention, the synchronization circuit 20 is not provided with the above-mentioned delay circuit 24, but is provided with only the synchronization separation circuit 21, the horizontal synchronization signal separation circuit 22, and the vertical synchronization signal separation circuit 23. , pulse signal a
A memory 26 is provided so that the image of the ghost signal component and its ghost signal component can be displayed in a wide range on the screen, and this memory 261 stores the signal of the period in which the pulse signal a is superimposed,
Thereafter, data is read out continuously from this memory 26.

A specific example of the configuration of this memory 26 is as shown in FIG. 4, and the illustrated one includes a memory element 27 with a storage capacity for one horizontal scanning line, a clock pulse generation circuit 28 for driving the memory element 27, and a clock pulse generation circuit 28 for driving the memory element 27. , a circulation amplifier circuit 29, a write signal switching circuit 30, and a write switching pulse generation circuit 31.

First, in the write switching pulse generation circuit 31, the monostable multivibrator 32 is triggered by the vertical synchronization signal as shown in FIG. 5B taken out from the synchronization circuit 20, and
A wide pulse as shown in FIG.

Next, a level detection circuit 36 composed of two sets of differential amplifier circuits 34 and 35 detects the level t1. of the triangular wave. Only during the period t2, a pulse having a width of approximately one horizontal period is generated as shown in FIG. 5E.

Since this pulse E is generated at two places, it is applied to one transistor 37 of the transistors 37 and 38 connected in parallel, and the pulse C is applied to the other transistor 38, as shown in FIG. 5F. Only the pulse is extracted and used as the write switching pulse.

Note that the integration time constant of the Miller integration circuit 33 and the level detection circuit 36 are set so that this write switching pulse F is generated with a pulse width of approximately one horizontal period during the period in which the pulse signal a is superimposed during the vertical retrace period. The detection level t1. of the differential amplifiers 34, 35 in Set t2.

This switching pulse F is applied via switch 39 to transistors 40 and 41 of write switching circuit 30, and the output of transistor 40 is applied to transistor 42.

The received video signal from the ghost removal circuit 10 is applied to the memory element 27 via the switching diode 43, and the memory read signal from the circulating amplifier circuit 29 is also applied to the memory element 2 via the switching diode 44.
Add to 7.

With this configuration, when the switch 39 is closed now, the transistor 42 is cut off, the transistor 41 is made conductive, and the diode 43 is made conductive during the period of the write switching pulse F, so that the received image from the ghost removal circuit 10 as shown in FIG. A video signal including the pulse signal a during the period of the write switching pulse F and its ghost signal component can be extracted from the signals as shown in FIG. 5G and stored in the memory element 27 for one horizontal period.

Note that if the memory element 27 is circulated in exactly one horizontal period, even if the pulse width of the switching pulse F is not exactly one horizontal period, as long as it is approximately one horizontal period, there will be no problem in the operation here. .

That is, when the switching pulse F is longer than one horizontal period, the video signal of the period exactly one thousand period back from the trailing edge of the switching pulse F is written in the memory element 27.
If it is a little shorter than one horizontal period, writing to the memory element 27 is not performed for the period that is short of one horizontal period, and the previously written contents remain as noise during that period. It is from.

After memorization, the conduction/cutoff state of the transistor 4L42 is reversed, so the diode 44 becomes conductive, and the memory element 2
7 memory contents are circulated.

As a result, the video signal G for one horizontal period can be repeatedly and continuously read out from the memory 27, and an image based on the components of the pulse signal a and the ghost signal can be projected over the entire screen of the cathode ray tube 6. can be displayed.

Therefore, the state of the ghost can be displayed very clearly, and its observation can be easily and accurately made.

When the memory 26 is not used, the interlocking switches 45 and 46 may be switched to short-circuit the memory 26 and allow the video signal to pass through.

In the above embodiment, the storage capacity of the memory 26 is set to one horizontal period, but it may be increased, and it goes without saying that an integer horizontal period is sufficient.

As described in detail above, the coast observation device of the present invention receives a television signal on which a pulse signal for ghost detection is superimposed during the horizontal scanning period during the vertical retrace period, and images the period in which this pulse signal is included. The signal is stored in a memory that circulates at a cycle that is an integral multiple of the horizontal cycle, and is read out continuously from this memory to display the image of the pulse signal and the image of the ghost signal on the cathode ray tube. Since it is a physical object, it is possible to display the state of a ghost in an extremely easy-to-understand manner, and it can be observed easily and accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a coast observation device according to an embodiment of the present invention, FIGS. 2, 3, and 4 are detailed block diagrams and circuit diagrams of a part of the same device, and FIG. 5A ,
B, C, D, E, F, and G are waveform diagrams for explaining the operation of the device. 4... Detection circuit, 5... Video amplification circuit, 6... Cathode ray tube, 10... Ghost removal circuit, 20... Synchronization circuit, 25... Deflection circuit, 26... Memory, 45,
46...Switch.

Claims (1)

[Claims] 1 With a period that is an integral multiple of the horizontal period for storing the video signal of the period in which the pulse signal is included in the received television signal in which the pulse signal for ghost detection is superimposed on the horizontal scanning period during the vertical retrace period. A circulating memory, means for continuously reading the stored contents of this memory from this memory, and a cathode ray tube to which the read signal is input and displays an image of the pulse signal and an image of the coast signal. A ghost observation device equipped with