JPH01154673A - Television offset beat removing device - Google Patents

Abstract

PURPOSE:To always suitably remove an offset beat interference by subtracting an interference signal to occur due to the offset separated by an interdigital filter from a receiving signal. CONSTITUTION:An input signal is given to a frequency converting circuit 2, the output is distributed into two and one side of them is filtered so as to pass through a luminance signal component band excluding chrominance components by a BFF 4. Next, the offset beat component signal is attenuated and removed by an interdigital filter 6, subtracted from the signal through an attenuator 9 in a subtracter 10 and the offset beat component signal is formed. The offset beat component signal is subtracted from the signal through a delaying circuit 5 with a subtracter 11. A desired TV signal is outputted from a frequency converting circuit 12 as an output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an offset beat removal device in same frequency television broadcasting.

[Summary of the Invention] This invention relates to improving beat disturbances caused by an offset of Hz or 20 KHz in lO when receiving television broadcasts on the same frequency at a relay broadcasting station. By adjusting the attenuation frequency of the shaped filter to match the interference wave or desired TV signal, an interference wave signal is formed, and by subtracting it from the original human signal, the interference wave due to the offset beat is removed and the interference is improved. It is something.

[Conventional technology] As a conventional technology, by controlling the directivity of the antenna,
How to reduce beats (Reference: Isobe, Okubo, Kaijima, "
“Offset Beat Canceller,” Television Society Technical Report,
EMCJ83-70 (1983)) or a method of extracting, subtracting, and removing a part of the offset beat spectrum using a crystal filter (narrow band filter) (
FY 1960, NHK National Technical Report Meeting Preliminary, November 1986
P63, 64: Patent Application 1986-115213 r Interfering Wave Removal Method (filed on May 30, 1986), or a method that extracts the beat component by orthogonal synchronous detection of the TV signal containing the beat and subtracts and removes the offset beat. There are some cases where methods have been tried.

[Problem to be Solved by the Invention J] However, the method using directivity control of the antenna has the drawback that it cannot improve this when offset radio waves arrive from the same direction as the desired television broadcast waves.

Furthermore, the method using a narrow band crystal filter has the disadvantage that the amount of improvement is limited because it cannot remove the sideband components of the offset beat spectrum and only removes the video carrier wave.

Furthermore, the method using orthogonal synchronous detection has the disadvantage that the amount of improvement is limited because the lower side wave components of the video signal are not sufficiently separated and remain.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a television offset beat removal device that eliminates the above-mentioned conventional drawbacks and eliminates the problems and can always appropriately remove offset beat interference.

[Means for Solving the Problems J] In order to achieve such an object, the present invention uses a comb filter to separate the television signal component and the interference signal component due to the offset, The interfering signal component is subtracted from the signal.

That is, the present invention provides filtering means for receiving broadcast waves of the same frequency due to a television offset and filtering a luminance component band signal from the received received signal, and a desired television signal outputted from the filtering means. and a comb filter for separating the interference signal caused by the offset, forming means for forming an interference wave signal based on the separated signal, and means for subtracting the output from the forming means from the received signal. It is characterized by

[Function 1] According to the present invention, the offset video component spectrum can be separated and removed from the television signal over a wide band by the comb filter, regardless of the arrival direction of the interference wave due to the offset.

Furthermore, even if offset interference waves are present either above or below the television broadcast carrier, either interference can be removed.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

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

In FIG. 1, 1 is an input terminal, 2 and 12 are frequency conversion circuits, and 3 is an OSC (oscillator). 4 is BPF
(bandpass filter), 5 and 7 are delay circuits, 6 is a comb filter, 8 and 9 are attenuators, IO and 11 are subtracters, and 13 is an output terminal.

FIG. 2 is a layout diagram showing an example of the human power signal spectrum in the embodiment shown in FIG. 1, and FIG. 3 is a frequency characteristic diagram showing an example of the operation of the comb filter 6 described above.

Next, the operation of each part of the embodiment shown in FIG. 1 will be explained in detail with reference to FIGS. 2 to 4.

A TV (television) signal including an offset beat signal as shown in FIG. 2 is input from the input terminal 1.

That is, in FIG. 2, the upper and lower side waves of the carrier frequency fC correspond to the television's horizontal scanning line frequency 1.
T occurring every frequency interval H of 5.75 KHz
This signal includes the spectrum of the V signal and the spectrum of an offset signal that occurs at a position shifted by a frequency interval of 10Hz.

An input signal from input terminal 1 is supplied to frequency conversion circuit 2 . Here, frequency conversion is performed to match the attenuation frequency of the comb filter 6 shown in FIG. 3 to the frequency of the offset beat signal included in the human signal.

Next, the output of the frequency conversion circuit 2 is divided into two parts, one of which is filtered by a BPF 4 so as to pass the luminance signal component band excluding the color signal. The offset beat component signal is attenuated and removed by the comb filter 6. Then, a subtracter IO subtracts the signal passing through the attenuator 8 with an attenuation amount of a/2 from the signal passing through the delay circuit 7 and the attenuator 9 with an attenuation amount of a-1 to form an offset beat component signal. .

The other divided into two from the frequency conversion circuit 2 described above passes through the delay circuit 5 as it is, and from its output is sent to the subtracter 1 described above.
The offset beat component signal output after being subtracted by G is subtracted by a subtracter 11 and then supplied to a frequency conversion circuit 12 . Here, the signal is converted back to the original television carrier (carrier wave) frequency, and a desired TV signal is obtained as an output signal at the output terminal 13.

The delay circuits 5 and 7 and the attenuators 8 and 9 allow the timing and level of the signal to be adjusted, thereby making it possible to adjust the timing and level of the TV after removing the offset beat component signal.
The level of the signal can be kept constant over the TV signal band. Here, the attenuation amounts of the attenuators 8 and 9 may be selected to a value of about a=1.21 in the case of a Hz offset in lO.

The frequency characteristics of the output signal at the output terminal 13 are as shown in FIG. In addition, in FIG. 4, in order to make it easier to understand the effect of the embodiment shown in FIG. 1, the frequency characteristics of the output signal are shown assuming that the respective spectra of the TV signal and the offset signal have constant amplitude over the entire frequency range. It shows.

FIG. 5 is a block diagram showing the configuration of another embodiment of the present invention.

In FIG. 5, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted.

A comb filter 14 removes the spectral components of the desired TV signal. 15 is an attenuator.

FIG. 6 shows the comb filter 14 in the embodiment shown in FIG.
FIG. 2 is a frequency characteristic diagram showing an example of operation.

Next, the operation of each component in the embodiment shown in FIG.
This will be explained with reference to the figures.

The output signal from the frequency conversion circuit 2 is divided into two parts, one of which passes through the BPF 4 and the luminance component signal is sent to the comb filter 14.
In addition to this, the desired signal, the TV signal, is removed due to the wave characteristics shown in FIG. It will be done. The other output signal from the frequency conversion circuit 2 described above is applied to the subtracter 11 through the delay circuit 5.

The output of the subtracter 11 becomes a TV component signal from which the offset beat component signal has been removed, and is supplied to the frequency conversion circuit 12.

Here, the original television carrier frequency is returned again, and the desired TV signal is taken out from the output terminal 13 as an output signal.

FIG. 7 is a block diagram showing a well-known configuration of an example of a comb filter.

In Fig. 7, 71 is an input terminal, 72 and 75 are attenuators, and 73 and 74 are IH (63,5p 5ec)
A delay circuit, 76 is an adder, and 77 is an output terminal.

With the above configuration, the filtering characteristics of a comb filter can be easily obtained.

[Effects of the Invention] As is clear from the above, according to the present invention, even if the direction of arrival of the offset radio wave is the same as that of the desired television radio wave, it can be accurately removed.

Furthermore, almost all of the spectrum components of the offset beat signal can be removed within the required band, and no unnecessary residual components are output.

Moreover, no damage is caused to the desired television signal itself.

Furthermore, the configuration of the device is simple and easy, and is advantageous from an economic standpoint.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a layout diagram showing an example of a human signal spectrum in the embodiment shown in the first diagram, and FIG. 3 is a comb diagram in the embodiment shown in the first diagram. FIG. 4 is a characteristic diagram showing an example of the output signal spectrum in the embodiment shown in FIG. 1, and FIG. 5 is a block diagram showing the configuration of another embodiment of the present invention. , FIG. 6 shows the comb filter 14 in the embodiment shown in FIG.
FIG. 7 is a block diagram showing the configuration of an example of a comb filter. 1... Input terminal, 2.12-... Frequency conversion circuit, 3... OSC (oscillator), 4... BPF. 5.7...Delay circuit, 6.14...Comb filter, 8.9.15...Attenuator, 10, 11...Subtractor, 13...Output terminal.

Claims (1)

[Claims] 1) A filtering means for receiving broadcast waves of the same frequency due to a television offset and filtering a signal in a luminance component band from the received received signal, and a signal output from the filtering means. a comb filter for separating a desired television signal from a disturbance signal caused by the offset; a forming means for forming the disturbance signal based on the separated signal; and an output from the forming means for receiving the signal. A television offset beat removing device comprising: means for subtracting from a signal. 2) The comb filter has a characteristic of attenuating the interference wave signal, and the forming means is a means for subtracting the output of the comb filter from the output of the filtering means. The television offset beat removing device according to item 1. 3) The television offset beat removing device according to claim 1, wherein the comb filter has a characteristic of attenuating the television signal, and the forming means is the comb filter itself. .