JPH07110048B2 - Television offset detection circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a beat level detection determination circuit of an offset beat detection circuit in television broadcasting.

[Conventional technology]

Fig. 5 shows the system of this type of conventional circuit. In the figure, (1) is a television signal, and (2) is an offset beat component extracted from the television signal (1).
Beat detection circuit, (3) an amplifier for amplifying the beat signal extracted by the beat detection circuit (2), (4) Detection for detecting the beat signal amplified by the amplifier (3) And (5) is an analog switch which passes the beat level signal detected by the detector (4) other than the vertical synchronization signal section by the vertical synchronization signal (6), and (7) is the output of this analog switch (5) Beat level signal, which is
(8) is a voltage comparator for comparing the beat level signal with the reference voltage (9), and (10) is a beat level judgment output which is an output of the voltage comparator (9).

FIG. 6 shows an example of the voltage waveform of each part of the conventional circuit shown in FIG. 1, and (a) is an output waveform example of the detector (4),
(B) is an output waveform example of the analog switch (5), (c)
Is an output waveform example of the voltage comparator (8).

Next, the operation will be described. A desired reception wave (hereinafter referred to as D wave) and an interfering wave (hereinafter referred to as U wave) are input to the television signal (1). The frequency relationship between D wave and U wave is 10
From this TV signal, which has a relationship of generating KHZ or 20 KHz offset beat, by the beat detection circuit (2)
Extracts beat component of 10KHz or 20KHz. The beat component is amplified by the amplifier (3) and then converted into a DC signal (hereinafter referred to as a beat level) by the detector (4). This signal waveform is shown in FIG. This beat level is then input to the analog switch (5), and the output of the beat level in the vertical synchronization section is prohibited. The output waveform of this analog switch (5) is shown in FIG. 6 (b). This occurs in the vertical sync signal section.
The KHz20KHz component is a component that is prohibited because it is not originally the offset component that you want to extract. The beat level of the output of the analog switch (5) is then input to the voltage comparator (8). In the voltage comparator (8), the reference voltage (9) is compared with the beat level, and when the beat level is lower than the specified beat level value determined by the reference voltage, a good judgment is made, and when the beat level is high, a non-judgment is made. .

[Problems to be solved by the invention]

The conventional beat level value determination circuit is configured as described above and is not affected by the beat component included in the vertical synchronizing signal, but the 10KHz and 20KHz components included in the television video signal are included. However, if there is a video component having a large 10 KHz component or 20 KHz component, the determination value becomes inaccurate as shown in FIG. 6 (c).

The present invention has been made to alleviate the above problems, and it is an object of the present invention to obtain a television offset beat detection circuit capable of accurately determining an offset beat level value without being affected by image components. An object [Means for solving the problem] A television offset beat detection circuit according to the present invention is to provide a "reject" signal when the "reject" signal period of the detection output is equal to or shorter than a predetermined time. A determination means for determining and outputting the period as a "good" signal is provided.

[Action]

The television offset beat detection circuit according to the present invention determines that a "no" signal pulse within a predetermined time is a beat detection caused by a video signal component, and outputs a "good" signal during the detection period, False detection due to video signal components is prevented, and accurate beat detection is possible.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) is a television signal, (2) is a beat detection circuit for extracting an offset beat component from the television signal (1), and (3) is a beat extracted by the beat detection circuit (2). Magnifier to increase the signal,
(4) is a detector for detecting the beat signal amplified by the amplifier (3), (5) is a vertical synchronizing signal by the vertical synchronizing signal (6) from the beat level signal detected by the detector (4) An analog switch that passes through the section, (7) is a beat level signal which is the output of this analog switch (5), (8) is this beat level signal, and a reference voltage (9)
(10) is the output of the voltage comparator (8), (11) is the re-trigger mono-multi circuit operated by the output of the voltage comparator (8), and (12) is the re-trigger mono-multi circuit. It is an OR circuit that outputs the sum of the output of the circuit and the output (10) of the voltage comparator (8).

Next, the operation will be described. As described in the conventional example, the determination as to whether the beat level order in the output of the voltage comparator (8) is good or not is inaccurate due to the influence of the image component. Also, even when there is no offset beat, 10
When the KHz and 20 KHz components are large, it may be determined whether or not the beat is large.

The output (10) of the voltage comparator (8) is erroneously judged as shown in FIG. 2 (a), but this output (10)
By passing the re-trigger mono-multi circuit (11)
The output shown in FIG. This mono-multi circuit (11) outputs a constant pulse width by the down edge trigger of the output (10) of the voltage comparator (8),
Further, even when a down edge trigger is input during the pulse output, the re-trigger mono-multi circuit outputs the re-output pulse by the trigger. By taking out the sum of this output and the output (10) of the voltage comparator (8) by the OR circuit (12), as shown in FIG. What is important in this circuit is the pulse width of the pulse output by the re-trigger mono-multi circuit (11). The setting of this pulse width is to reduce the probability of malfunction and
It may be determined in consideration of the reaction time when the control is performed by using the beat level value determination output output from the output of the OR circuit (12).

In the above embodiment, the effect was obtained by using the re-trigger mono-multi circuit (11) and the OR circuit (12), but a CPU may be used. A system diagram of the embodiment in this case is shown in FIG. In this embodiment, it is assumed that the CPU (16) determines whether the beat level is good or bad at a constant sampling interval as shown in FIG. 4 (b). When the number of times of determination of the data continues for a certain number of times continuously, it is determined that the beat level is really high, and when it is sporadic or when the number of times is short, it is determined that the determination is an error. The method of determining the fixed number of times may be considered in the same manner as the determination of the pulse width of the retrigger monomulti (11) of the above-described embodiment.

〔The invention's effect〕

As described above, according to the present invention, since the determination circuit for eliminating the false detection due to the 10 KHz and 20 KHz components due to the video is added to the beat level determination, the offset beat level determination with higher accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a system diagram showing a television offset beat detection circuit according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a system diagram showing a television offset beat detection circuit according to an embodiment, FIG. 4 is an operation waveform diagram for explaining the operation of FIG. 3, FIG. 5 is a system diagram of a conventional television offset beat detection circuit, FIG. 6 is an operation waveform diagram for explaining the operation of FIG. In the figure, (2) is a beat detection circuit, (4) is a detector, (5) is an analog switch, (6) is a vertical synchronization signal, (8) is a voltage comparator, and (11) is a re-trigger mono-multi circuit. , (12) is an OR circuit, and (16) is a CPU. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A beat detection circuit for detecting a beat component of a predetermined frequency from a television signal, a detector for detecting a beat component detected by the beat detection circuit and outputting a beat level signal, and a beat level of this detector. A signal is input, a switch that prohibits the output of beat level signals in the vertical synchronization section, a voltage comparator that compares the output of this switch with a reference voltage, and a pulse of a predetermined pulse width that is triggered by the output of this voltage comparator. A re-trigger mono-multi circuit for outputting, a logical sum circuit for outputting a logical sum of the output of the re-trigger mono-multi circuit and the output of the voltage comparator, and the predetermined frequency component included in the video signal of the television signal Television offset beat detection circuit characterized by preventing false detection. 2. A beat detection circuit for detecting a beat component of a predetermined frequency from a television signal, a detector for detecting the beat component detected by the beat detection circuit and outputting a beat level signal, and a beat level of this detector. A signal is input, a switch that prohibits the output of the beat level signal in the vertical synchronization section, a voltage comparator that compares the output of this switch with a reference voltage, the output of this voltage comparator is determined by the sampling pulse interval of a constant cycle, When the output of the switch is lower than the reference voltage continuously for a predetermined number of times,
A television offset beat detection circuit comprising a CPU for performing erroneous detection due to the predetermined frequency component included in the video signal of the television signal.