JPS588634B2 - TV Ghost House - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device that clearly measures the direction of arrival of a television ghost.

In recent years, with the diversification of economic activities, mid-to-high-rise buildings such as government buildings, public halls, telephone offices, and condominiums have been constructed in large cities, and TV ghosts reflected from these walls can cause disturbances far away, causing simple ghosts. , compound ghosts are occurring in various places.

A similar phenomenon occurs with power transmission lines, and as the position of the power transmission lines changes due to day/night temperature changes, the effects of ghosting change, resulting in unsightly screens.

Shinkansen trains and expressways also cause ghosts.

These damages are expected to increase in the future, and in order to prevent them, it is necessary to take measures such as communal reception and reception antennas for ghost countermeasures, but recently the cost of these measures has been made compulsory to be borne by the cause. It's starting to look like this.

Therefore, the person responsible for these problems needs to know how many ghosts are occurring in the relevant building.

In addition, since regulatory agencies need to control this, it is necessary to clarify the source of ghost occurrences.

Conventional measuring instruments for measuring TV ghosts have not been satisfactory, and in particular, there are almost no measuring instruments that can determine the direction.

Therefore, conventionally, the only way to know the direction of a ghost is to measure the delay time of the ghost, draw an ellipse on a map with the broadcasting station and measurement point as focal points, and visually check the buildings to find out the direction of the ghost. There wasn't.

Therefore, the method of determining the size of the ghost by rotating the directional antenna is possible because it is possible to stably determine changes in the ghost level while the level of the direct wave is large, but it is possible to determine the size of the ghost by rotating the directional antenna. When the value becomes equal to the level of the direct wave, synchronization becomes unstable and it becomes difficult to judge the intensity of the ghost on the screen.

The device of the present invention arranges three receiving antennas close to each other, uses one of them as a reference antenna, receives and detects the desired wave, performs synchronization separation, and uses this output to perform synchronization control of the oscilloscope. , the other two are the same type of receiving antennas, arranged in the same direction so that they can rotate at the same time, and their outputs are input to a π-type hybrid circuit to obtain a sum output and a difference output, and the sum output and difference output are respectively Detect and synchronously separate to obtain synchronous output.

This synchronized output is input to the oscilloscope as a narrow pulse (differential pulse) by a differentiating circuit, and
The present invention is characterized in that the arrival direction of the ghost wave is determined by simultaneously rotating the same type of book antenna and observing the magnitude of the differential pulse corresponding to the sum output and the difference output on the oscilloscope.

An embodiment of the present invention will be explained below with reference to the drawings. Fig. 1 shows an explanatory block diagram of an embodiment of the apparatus of the present invention.

In the present invention, a fixed antenna 1 for receiving desired waves and two rotatable antennas 2a and 2b for receiving ghost waves (reflected waves, interference waves) of the same type are used.
The antennas 2a and 2b are arranged close to each other so that the difference in distance from the ghost generation point is reduced.

The output of antenna 1 is added to tuner 3a, and the following IF
The signal is sequentially applied to the amplifier 4a, the detector 5a, the video amplifier 6a, and the synchronous separator 7a, and is synchronously separated.

This sync separator 7a is mainly composed of transistors, and the operating point of the transistor is adjusted to cut the video signal of the TV signal and take out only the sync signal. Only the synchronization signal is extracted.

The output of this synchronous separator 7a is applied to the external synchronous terminal of the oscilloscope 8, and synchronized with the differential pulse of the ghost wave output from differentiating circuits 20b and 20c that differentiate the outputs of synchronous separators 7b and 7c, which will be described later. .

A directional antenna is usually used as the antenna 1, which allows stable observation of differential pulse waveforms corresponding to ghost waves.

In addition, the antennas 2a and 2b should use the same type of directional antenna, and when the sum of the combined directivity is obtained, the arrangement should be sharp and have few side lobes. Install at intervals.

The outputs of the antennas 2a and 2b are sent to tuners 3b and 3c, respectively.
, IF amplifiers 4b, 4c to the π-type hybrid circuit 9.

This π-type hybrid circuit 9 has a configuration as shown in FIG.

In the same figure, 11 is an in-phase two-way distribution transformer, and 12 is an anti-phase two-way distribution transformer.
It is a distribution transformer, and both are connected at the respective secondary coils L2 and L4 as shown in the same figure, and the connection point is A.
,B.

The primary coil L1 and the secondary coil L2 of the in-phase two-distribution transformer 11 are connected at their neutral points, and the primary coil L
One end of 1 is grounded.

The neutral point of the primary coil L3 of the anti-phase two-way distribution transformer 12 is grounded.

With the above configuration, when high frequency signals S1 and S2 are applied to terminals A and B of this π-type hybrid circuit, respectively, a sum signal of S1+S2 is obtained at terminal C, and a difference signal of S1-S2 is obtained at terminal D. is obtained.

That is, the output of the sum and difference of antennas 2a and 2b can be obtained from this hybrid circuit 9.

Note that terminal E has S2, which has a phase difference of 180° from terminal D.
A difference signal -S1 is obtained.

These two output signals, that is, the sum signal and the difference signal, are sent to the detector 5, respectively.
b, 5c, and is vertically synchronously separated via video amplifiers 6b, 6c and synchronous separators 7b, 7c, and differentiated circuits 20b,
20c, the signals are differentiated into narrow pulse signals (differential pulses), and then applied to the vertical input terminal of the oscilloscope 8.

In addition, 10 is a local oscillator, and tuners 3a, 3b,
3c is a selection circuit that selects the TV channel frequency;
It consists of a high frequency amplifier circuit and a frequency mixer.

Furthermore, although equivalent pulses, vertical synchronizing pulses, horizontal synchronizing pulses, etc. can be used to synchronize the oscilloscope, it is more convenient to use the first two.

The case where a vertical synchronization pulse is used will be described below as an example.

As shown in Figure 2, when a desired wave from a broadcasting station is received by an antenna, the ghost wave reflected by a building is transmitted to the antenna 1.
, 2a, 2b, but since the input of the desired wave to antenna 1 is larger, the synchronization pulse outputs only the desired wave.

If the desired radio wave is now being reflected by a building and a ghost wave is coming from the θ direction, it is assumed that the antennas 2a and 2b are rotated and reach the position of θ degrees.

That is, the antennas 2a and 2b are aligned in the direction of the ghost wave.

The composite directivity at this time is shown in Figure 3. In Figure 3,
A is the combined directivity of the sum output of antennas 2a and 2b (output of C terminal), B is the combined directivity of the difference output (output of D terminal), and C is the single directivity of antenna 2a or 2b for comparison. This is shown for the purpose of

All are shown with adjusted levels for ease of understanding.

The sum of the directivity of the antennas 2a and 2b is output from the C terminal of the π-type hybrid circuit 9, and the difference of the directivity is output from the D terminal of the π-type hybrid circuit 9.

Therefore, the ghost wave output is the maximum in the sum output of the C terminal, and the ghost wave output is the minimum in the difference output of the D terminal.

To operate these effectively, it is necessary to keep the input signals at the A and B terminals of the π-type hybrid circuit 9 at the same level, so it is desirable to apply AGC to the tuners 3b and 3c, and connect them to the antennas 2a and 2b. It is assumed that the performance of each tuner 3b, 3c and IF amplifier 4b, 4c is the same.

If the antennas 2a and 2b are rotated here, as shown in Fig. 3, the directionality of the sum output is obtained at the C terminal of the π-type hybrid circuit and the difference output is obtained at the D terminal with respect to the arrival direction of each ghost wave. be able to.

Referring now to FIG. 4, a differential pulse obtained by subjecting the output (sum output) of the C terminal to vertical synchronization separation via the detector 5b, video amplifier 6b, and synchronization separator 7b and obtaining the differential pulse through the differentiation circuit 20b will be explained.

H indicates one horizontal scanning period.

FIG. 4-1 shows an enlarged view of one section of the vertical synchronizing pulse of the desired wave, in which the ghost wave arrives with a time delay of δ and overlaps with the desired wave as shown by the dotted line.

If the desired wave and the ghost wave are in phase and superimposed, the waveform will be as shown in FIG. 4-2.

When this pulse is passed through a differentiating circuit, the waveform becomes as shown in FIG. 4-3, and when the sweep speed of the oscilloscope is adjusted so that only the positive differential pulse is observed on the oscilloscope, the waveform becomes as shown in FIG. 4-4.

That is, the large output differential pulse of the desired wave appears at the left end, and the differential pulse of the ghost wave appears with a delay of δ time.

On the other hand, in the differential output of the D terminal, the ghost wave in the θ direction becomes zero, so only the waveform of the desired wave is present.

When the outputs of the sum signal and the difference signal from the differentiating circuits 20b and 20c are input to a two-phenomenon oscilloscope, they are observed as shown in FIG.

In the figure, the upper side is a sum differential pulse, and the lower side is a difference differential pulse.

Therefore, in order to clearly know the direction of the ghost wave, first point the antennas 1, 2a, 2b in the direction of the desired wave, which is the broadcasting station.

In this case, the point on the plan tube of the oscilloscope where the sum differential pulse, which is the desired wave on the left side, is maximum and the difference differential pulse is minimum is the direction of the desired wave, and this is defined as 0 degrees.

Next, the antennas 2a and 2b are rotated at the same time, so that when a ghost wave has arrived, the pulses separated by δ time have the maximum differential pulse of the sum and the minimum differential pulse of the difference.

Then, the antenna 2 eliminates the differential pulse while comparing the amplitude of each pulse observed with an oscilloscope.
Find the rotation angle θ of a and 2b.

This angle θ becomes the arrival angle of the ghost wave, and the arrival angle can be read with high accuracy.

The reading angle is based on the frequency band characteristics of the video band, the accuracy of the π-type hybrid circuit, and the ghost wave receiving antennas 2a and 2.
Although it depends on the difference in the input electric field strength with respect to b, a precisely adjusted circuit can obtain an azimuth accuracy of 1 degree or less.

In the embodiment, the π-type hybrid circuit 9 is the IF amplifier 4.
b and the detector 5b, but the antenna 2a
, 2b and the tuner 3b.

In addition, in the embodiment, it is converted to an intermediate frequency (IF), and the AGC
However, it is not necessarily necessary in places with strong electric fields.

Usually, many ghost waves arrive, so
In this case, first direct the antennas 2a and 2b toward the desired wave and move the desired ghost toward the ghost using the above method while rotating the antennas so that the sum differential pulse is large and the difference differential pulse is small for each delay time. All you have to do is detect it.

Furthermore, by measuring the time interval δ between the desired wave and the ghost wave, it is possible to calculate the position of the building that is the source of the ghost wave.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the device of the present invention, Fig. 2 is an antenna arrangement diagram, Fig. 3 is a composite directivity diagram of a rotating antenna, and Figs. 4 and 5 are for explaining the device of the present invention. The diagram, FIG. 6, shows a π-type hybrid circuit diagram. 1...Fixed antenna for desired wave reception, 2a, 2b
...Ghost wave receiving antenna, 3a, 3b,
3c...Tuner, 4a, 4b, 4c...
...IF amplifier, 5a, 5b, 5c...Detector, 6a, 6b, 6c...Video amplifier, 7a,
7b, 7c... Synchronous separator, 8... Oscilloscope, 9... π-type hybrid circuit, 10... Local oscillator, 11...・・・In-phase 2-distribution transformer, 12 ・・・・・・Reverse-phase 2-distribution transformer, 2
0b, 20c... Differential circuit.

Claims (1)

[Claims] 1. An antenna 1 that receives desired waves of television broadcast waves, two simultaneously rotatable antennas 2a and 2b of the same type that receive ghost waves, and a first receiving section that detects and amplifies the output of the antenna 1, A first synchronization separator 7a separates a synchronization signal for synchronizing the oscilloscope 8 from the output of this receiving section, and the outputs of the two antennas 2a and 2b are combined to obtain a sum output and a difference output π type hybrid circuit 9, second and third receiving sections that respectively detect and amplify the output of this π type hybrid circuit 9, and second and third synchronous separators 7b, 7c connected to the respective receiving sections.
and first and second differentiating circuits 20 for obtaining narrow differential pulses from the outputs of these synchronous separators 7b and 7c.
The outputs of the first and second differentiating circuits 20b and 20c are input to the oscilloscope 8, and the two antennas 2a and 2b are simultaneously rotated to correspond to the sum output and difference output. 1. A television ghost direction measuring device characterized in that the direction of arrival of a ghost wave can be determined by observing differential pulses.