JPS5841711B2 - Ghost Kansokuuchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for observing the state of ghosts in television signals received by a pre-vision 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 reflected from reflective objects such as buildings or mountains during transmission are often received as overlapping signals arriving in a straight line. becomes a ghost signal, resulting in a ghost image on the screen.

Therefore, as a means to reduce the negative effects of this ghost signal, there are devices that remove the ghost signal in the antenna system such as a diaperity antenna, and delay the detected video signal by the same amount as the delay time of the ghost signal. Many methods are known, such as one that cancels out the ghost signal by adding it to the undelayed video signal and one that removes the ghost signal using a synchronous detection circuit.

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

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 ghost signals.

An embodiment of the present invention 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 such that a pulse signal a for ghost detection is superimposed on 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 such a television signal receiving apparatus 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 synchronous detection carrier regeneration circuit 12 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, phase shifted to an appropriate phase by a phase shifter 16, and 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 11 and 140 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 170, the phase shift amount of the phase shifter 16, and the gain amount of the gain adjustment circuit 18. All you have to do is observe the screen while receiving and make these adjustments to remove ghost components.

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

As described 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 in a normal preview receiver as it is due to the blanking effect.

For this reason, this device is configured to display video during the vertical retrace period of the television signal A.

In the illustrated embodiment, the synchronization circuit 20 is provided with a delay circuit 24 that further delays the phase of the vertical synchronization signal in addition to the usual synchronization separation circuit 21, vertical synchronization signal separation circuit 22, and horizontal synchronization signal separation circuit 23. The deflection circuit 25 is controlled by the delayed vertical synchronization signal.

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 image during the vertical retrace period of the television signal can be projected on the screen, and the part on which the pulse signal a is superimposed can also be projected on the screen. can be displayed.

Furthermore, as described above, the vertical blanking period including the pulse signal a can be displayed on the cathode ray tube 9, but this pulse signal a is usually superimposed on the black level signal in the direction of the white level. Therefore, if the polarity of the video signal of the ghost signal component is reversed depending on the phase of the ghost signal, it is difficult to observe this.

Therefore, in this device, in order to eliminate such inconvenience, a brightness level switching circuit 26 is installed before or after the video amplification circuit 5.
is provided so that the video luminance level during the period in which the pulse signal a is superimposed is changed toward the white level.

A specific example of the configuration of the brightness level switching circuit 26 is as shown in FIG. 4, and one of the two transistors 27 and 28 connected to the differential amplifier circuit receives the received image as shown in FIG. 5A. In addition to applying the signal, a bias switching transistor 29 is provided to the other transistor 28, and a switching pulse as shown in FIG. The transistor 27 is switched on only during the period of the switching pulse C indicating the ghost observation period including the period in which the pulse signal a is superimposed.
, 28 are changed, and the level of the video signal is changed toward the white level only during this period as shown in the fifth diagram.

As the switching pulse generating circuit 30, a monostable multibiflator or the like can be used, for example, and the switching pulse C is generated by being triggered by a vertical synchronizing signal as shown in FIG. 5B extracted from the synchronizing circuit 20.

31 is an inversion transistor.

By changing the video brightness level during the ghost observation period on which pulse signal a is superimposed in the direction of the white level in this way, it is possible to clearly display whatever ghost signal component is occurring. and can facilitate accurate observation.

In this way, by displaying an image of the pulse signal a and its ghost signal components on the cathode ray tube 6, the state of the ghost can be easily and accurately observed, and the ghost removal circuit 10 can be adjusted while observing this. By doing so, it is possible to easily adjust to the best ghost removal state.

The items added to a normal pre-vision receiver to observe and remove ghosts are shown in Figures 1 to 4.
These are the brightness level switching circuit 26, the ghost removal circuit 10, and the delay circuit 24 in the figure.

As described above, according to the present invention, when a pulse signal for ghost detection is superimposed on the horizontal scanning period during the vertical retrace period, an image during the vertical retrace period is projected on the cathode ray tube screen. In addition, during the ghost observation period, the brightness level is switched toward white so that images containing ghosts can be clearly displayed, so that ghosts can always be clearly displayed without being disturbed by the video signal. This provides an indication of the signal.

Then, while viewing this display, the ghost can be removed by manually adjusting the ghost removal circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a ghost observation device according to an embodiment of the present invention, FIGS. 2, 3, and 4 are detailed block diagrams and circuit diagrams of three parts of the device, and FIG. ,
B, C, and D are waveform diagrams for explaining the operation of the device. 4...Detection circuit, 5...Video amplification circuit, 60900. . Cathode ray tube, 10...Ghost removal circuit, 20.
... Synchronization circuit, 22 ... Vertical synchronization signal separation circuit, 24 ... Delay circuit, 25 ...
Deflection circuit, 26... Brightness level switching circuit.

Claims (1)

[Claims] 1. A ghost removal circuit is provided which takes the received television signal as an input signal, removes the ghost signal in the television signal by manual adjustment, and applies the output of this ghost removal circuit to the cathode ray tube via a brightness level switching circuit. means for controlling a deflection circuit so as to project an image during the vertical retrace period of the television signal on the cathode ray tube, and a signal indicating a ghost observation period of the vertical retrace period; The ghost observation device is provided with a switching pulse generation circuit that generates a switching pulse, and an output signal of the switching pulse generation circuit is applied to the luminance level switching circuit to change the video luminance level during the ghost observation period toward the white level.