JPH062374Y2 - Television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a television receiver having a function of receiving either a positive or negative modulated video intermediate frequency signal.

[Conventional technology]

Generally, in an area where both positive and negative modulation television broadcasts can be received, it is desirable that the television receiver has a function of receiving both of the broadcast systems,
This type of television receiver is constructed, for example, as shown in FIG.

In FIG. 9, (1) is a video detection circuit for detecting the video intermediate frequency signal by inputting a positively or negatively modulated video intermediate frequency signal through the input terminal (2), and (3) is a detection circuit ( Polarity inversion circuit that inverts or non-inverts the polarity of the detection output of 1)
(4) is an inversion control circuit including a manual switch for controlling the polarity inversion circuit (3) according to the modulation polarity of the received television broadcast, (5) is a video processing circuit, the polarity inversion circuit (3)
A television signal, which is the detection output of the detection circuit (1), is input via the, and the input television signal is processed.

Then, for example, when receiving positively-modulated and negatively-modulated television broadcasts, it is assumed that the detection circuit (1) outputs positive-polarity and negative-polarity television signals, respectively, and the video processing circuit (5) has positive polarity. When a positively modulated television broadcast is received when a positive polarity television signal is required, a positive polarity television signal is output as a detection output from the detection circuit (1). It is not necessary to operate, and the positive polarity television signal from the detection circuit (1) is input to the video processing circuit (5) without being inverted in polarity by the polarity inversion circuit (3), and the video processing circuit (5) ), The inputted positive polarity television signal is processed.

On the other hand, when receiving a negatively modulated television broadcast, a negative polarity television signal is output from the detection circuit (1), so the inversion control circuit (4) must be operated, and the inversion control circuit (4) By the operation of, the polarity inversion circuit (3) outputs the television signal inverted to the positive polarity, and the video processing circuit (5) processes the positive polarity television signal from the polarity inversion circuit (4). To be done.

The same operation is performed when the video processing circuit (5) requires a television signal of negative polarity.

However, in this case, the inversion control circuit (4) has to be operated according to the modulation polarity of the received television broadcast, which is very troublesome.

Therefore, conventionally, a tuning unit capable of storing positive and negative polarity signals in advance for each program position is provided,
It is considered to control the polarity reversing circuit (3) by the tuning means.

[Problems to be solved by the invention]

However, in this case, when the receiving channel is changed for program selection after the program position is determined, the positive and negative polarity signals are determined for each program position. The polarity inversion of the detection output is performed by the polarity inversion circuit so that the modulation polarity of the received television broadcast and the polarity of the channel selection unit match so that the polarities eventually match. There is a problem that it must be done.

Further, as described in JP-A-60-224382 (H04N 5/46), a polarity determination circuit for determining the polarity of the detection output and the polarity determination circuit for determining either positive or negative polarity. And a flip-flop circuit which performs an inversion operation when the image intermediate frequency I
It is also considered that the control terminal of C is controlled to high and low levels and the polarity of the detection output from the video intermediate frequency IC is switched according to the modulation polarity of the received television broadcast. The polarity of the video detection output is automatically discriminated, and the modulation polarity itself of the received television broadcast is not discriminated, and the responsiveness of the discrimination is lacking.

In view of this, the technical problem of this invention is to make it possible to automatically and accurately determine the modulation polarity of a received television broadcast with good responsiveness.

[Means for solving problems]

Then, means for solving the above-mentioned problems of the prior art will be described with reference to FIGS. 1 and 2 corresponding to the embodiment.

That is, in this invention, a video detection circuit (1) that detects a positively or negatively modulated video intermediate frequency signal, and a sync separation circuit (7) that separates a sync signal from the detection output of the detection circuit (1). A horizontal discrimination circuit (8) for discriminating whether or not the frequency of the synchronization signal separated by the synchronization separation circuit (7) matches a horizontal frequency, and outputting a horizontal discrimination signal, and the synchronization separation circuit (7 ), A vertical discrimination circuit (9) for discriminating whether or not the frequency of the synchronizing signal separated by the vertical frequency coincides with the vertical frequency and outputting a vertical discrimination signal, and a modulation polarity discrimination signal for logical product of the both discrimination signals. AND gate (10) to output as, and the polarity inversion output to the video processing circuit (5) by inverting or non-inverting the polarity of the detection output of the detection circuit by the modulation polarity determination signal from the AND gate (10). A circuit (3) is provided.

[Action]

Therefore, according to this invention, the frequency of the signal separated by the synchronization separation circuit (7) is
It is determined by (8) and (9) whether or not they match the horizontal and vertical frequencies, respectively, and the logic of the horizontal and vertical discrimination signals output according to the discrimination results by both discrimination circuits (8) and (9). The product is obtained by the AND gate (10), and the modulation polarity of the received television broadcast is automatically determined.
(0) outputs a modulation polarity determination signal to the polarity inversion circuit (3), and the detection output of the video detection circuit (1) is inverted or non-inverted by the polarity inversion circuit (3) according to the modulation polarity determination signal, It is output to the processing circuit (5).

〔Example〕

Next, the present invention will be described in detail with reference to FIGS. 1 to 5 showing one embodiment thereof.

In FIG. 2, the same symbols as in FIG. 9 indicate the same or corresponding ones, and (6) controls the modulation polarity of the received television broadcast to control the polarity reversing circuit (3) to inversion or non-inversion. This is a polarity discriminating circuit and is configured as shown in FIG.

That is, in FIG. 1, (7) is a sync separation circuit for separating the sync signal from the detection output of the detection circuit (1), and (8) is the frequency of the sync signal separated by the sync separation circuit (7) for the television. A horizontal discrimination circuit that discriminates whether or not it matches the horizontal frequency f _H in the broadcasting system and outputs a horizontal discrimination signal, (9)
Is a vertical discriminating circuit that discriminates whether or not the synchronizing signal separated by the synchronizing separating circuit (7) matches the vertical frequency f _V in the television broadcasting system, and outputs a vertical discriminating signal (10).
Is an AND gate, and takes the logical product of both discrimination signals from both discrimination circuits (8) and (9), and outputs it to the polarity inversion circuit (3) as a modulation polarity discrimination signal, and the modulation polarity discrimination signal Thus, the polarity reversing circuit (3) inverts or non-inverts the detection output of the detection circuit (1) and outputs it to the video processing circuit (5).

By the way, the horizontal and vertical discriminating circuits (8) and (9) respectively have the third
It is constructed as shown in FIGS.

First, in FIG. 3 showing the horizontal discrimination circuit (8), (11) is an oscillation circuit that oscillates at a horizontal frequency f _H , and (12) is an oscillation circuit (11).
The phase discrimination circuit that performs feedback control so that the phase of the oscillating signal is synchronized with the phase of the signal from the sync separation circuit (7), and (13) is the phase comparison circuit, which is the phase of the signal from the sync separation circuit (7). And the phase of the oscillation output signal of the oscillation circuit (11).

At this time, the signal from the sync separation circuit (7) is
1) and the phase discrimination circuit (12) are within the specified pull-in range, the output signal of the sync separation circuit (7) and the oscillation circuit (1
The phase of the oscillation output signal in 1) matches well, and the sync separation circuit
Assuming that the frequency of the output signal of (7) matches the horizontal frequency f _H , the horizontal determination signal indicating “match” is output.

On the other hand, when the signal from the sync separation circuit (7) is outside the predetermined pull-in range of the oscillation circuit (11) and the phase discrimination circuit (12), the output signal of the sync separation circuit (7) and the oscillation Circuit (1
Assuming that the phases of the oscillation output signals of 1) do not substantially match and the frequency of the output signal of the sync separation circuit (7) does not match the horizontal frequency f _H , a horizontal discrimination signal indicating “mismatch” is output.

Next, in FIG. 4 showing the vertical discrimination circuit (9), (14)
Is an integration circuit to which the output signal of the sync separation circuit (7) is input and which extracts the vertical component by integrating the output signal, (15) an oscillation circuit that oscillates at a vertical frequency f _V , and (16) an oscillation circuit (15 ) Is a phase discrimination circuit that performs feedback control so that the phase of the oscillation signal matches the phase of the output signal of the integration circuit (14), and (17) is a phase comparison circuit that compares the phase of the output signal of the integration circuit (14). ,
The phase of the oscillation output signal of the oscillation circuit (15) is compared.

At this time, if the output signal of the integration circuit (14) is within the predetermined pull-in range of the oscillation circuit (15) and the phase discrimination circuit (16), the vertical component of the output signal of the sync separation circuit (7) And the phase of the oscillation output signal of the oscillation circuit (15) match well, and the frequency of the vertical component of the output signal of the sync separation circuit (7) is the vertical frequency f _V
The vertical discrimination signal indicating "match" is output.

On the other hand, when the output signal of the integration circuit (14) is outside the predetermined pull-in range of the oscillation circuit (15) and the phase discrimination circuit (16), the vertical component of the output signal of the sync separation circuit (7) And the phase of the oscillation output signal of the oscillator circuit (15) do not substantially match, and the vertical component frequency of the vertical component of the output signal of the sync separation circuit (7) does not match the vertical frequency f _V. The discrimination signal is output.

Then, for example, the video processing circuit (5) requires a positive polarity television signal, and when receiving a positively modulated television broadcast, from the horizontal determination circuit (8) and the vertical determination circuit (9),
A high-level signal is output as a horizontal / vertical discrimination signal indicating "match", and the polarity is determined by the high-level modulation polarity discrimination signal from the AND gate (10) based on the logical product of these high-level horizontal / vertical discrimination signals. It is assumed that the inverting circuit (3) is controlled to the non-inverting state.

Now, the positive modulation television broadcast is received, the detection circuit
When a positive polarity television signal as shown in FIG. 5 is output from (1) as the detection output, the sync separation circuit (7)
By inputting the signal separated by, both discrimination circuits (8),
Both outputs of (9) become high level and AND gate (1
The output of (0) also becomes high level and the received television broadcast is judged to be positive modulation, the polarity inverting circuit (3) is controlled to the non-inverting state, and the positive polarity from the detection circuit (1) shown in FIG. The television signal is input to the video processing circuit (5) without being inverted in polarity by the polarity inversion circuit (3) and processed by the video processing circuit (5).

Next, when a negatively modulated television broadcast is received and a negative polarity television signal as shown in FIG. 6 is output as a detection output from the detection circuit (1), the sync separation circuit
By inputting the signals separated by (7), both discriminating circuits
The outputs of (8) and (9) are both low level indicating "mismatch", and the output of the AND gate (10) is low level, and it is determined that the received television broadcast is negative modulation, and the polarity inversion circuit
(3) is controlled to the inverted state, and the television signal of the negative polarity shown in FIG. 6 from the detection circuit (1) is inverted to the positive polarity by the polarity inversion circuit (3), and the television is inverted to the positive polarity. The John signal is processed by the video processing circuit (5).

By the way, when the television signal having the waveform shown in FIG. 7 is output from the detection circuit (1), the synchronization separation circuit (7) causes
The so-called white level portion of the input signal of the waveform shown in the figure is synchronously separated, and in the case of FIG. 7, since the repeating frequency of the white level portion of the television signal matches the horizontal frequency f _H , the horizontal discrimination circuit The output of (8) becomes high level.

On the other hand, the waveform of the vertical synchronization portion of the television signal shown in FIG. 7 is considered to be as shown in FIG. 8. In the case of FIG. 8, the vertical synchronization of the signal separated by the white level portion is performed as described above. Since the component will be missing, the vertical discrimination circuit
The output of (9) goes low, and as a result, the AND gate
The output of (10) becomes low level, the received television broadcast is judged to be negative modulation, the polarity reversing circuit (3) is controlled to the reversing state, and the detection circuit (1) changes from FIG. 7 to FIG. The television signal shown is inverted, and the inverted television signal is processed by the video processing circuit (5).

At this time, the discrimination by the horizontal discrimination circuit (8) is performed at a speed of about 4 times or 5 times that of 1H (H is 64 μsec in the horizontal scanning period), and the discrimination by the vertical discrimination circuit (9) is 1 V (V is vertical). Since it is performed at a speed of about 5 times of 20 msec during a scanning period, when a negatively modulated television signal is received, the output of the horizontal discrimination circuit (8) becomes a low level at the above speed,
AND gate (10) regardless of the output of vertical discrimination circuit (8)
Output becomes low level, and it is determined that the received television broadcast has negative modulation.

That is, the received television broadcast is determined to be negative modulation at the determination speed of the horizontal determination circuit (8).

When a broadcast signal that is prone to error is received, such as a color bar signal or a pattern signal for synchronizing when a VTR signal is input to a television receiver in the UHF band, the horizontal discrimination circuit (8) The discrimination is performed at the discrimination speed of the vertical discrimination circuit (9) whose discrimination speed is slower than that.

Even when the video processing circuit (5) requires a negative polarity television signal, the same operation as described above is performed.

Therefore, according to the above embodiment, the frequency of the signal separated by the synchronization separation circuit (7) is
By providing horizontal and vertical discrimination circuits (8) and (9) for discriminating whether or not they match f _H and f _V , respectively, and by taking the logical product of the outputs of both discrimination circuits (8) and (9), It is possible to automatically determine the modulation polarity of the received television broadcast, and based on the result of the modulation polarity determination, the polarity of the detection output of the video detection circuit (1) is inverted or non-inverted by the polarity inversion circuit (3) to process the image. Therefore, it is possible to automatically switch and receive both positive modulation and negative modulation television broadcasts.

Further, since the modulation polarity is appropriately discriminated at the discrimination speeds of the horizontal discrimination circuit (8) or the vertical discrimination circuit (9),
For normal broadcast signals, the horizontal discrimination circuit (8) can discriminate at a high speed, and for error-prone broadcast signals such as color burst signals, the vertical discrimination circuit (9) can discriminate at a slow speed for response. It is possible to discriminate the modulation polarity with good performance and less error.

Needless to say, the configurations of both the discrimination circuits (8) and (9) are not limited to those described above.

[Effect of device]

As described above, according to the television receiver of the present invention, the horizontal and vertical discriminating circuits for discriminating whether or not the frequencies of the signals synchronously separated by the synchronous separating circuit match the horizontal and vertical frequencies, respectively, are provided. Since the logical product of the outputs of both discriminating circuits is taken, the modulation polarity of the receiving television broadcast can be automatically discriminated, and the polarity of the detection output of the video detection circuit is determined by the polarity reversing circuit based on the discrimination result of the modulation polarity. Inverted or non-inverted video processing can be performed, and both positive modulation and negative modulation television broadcasts can be automatically switched and received, and the effect is great.

[Brief description of drawings]

1 to 8 show an embodiment of a television receiver of the present invention. FIG. 1 is a block diagram of essential parts, FIG. 2 is an overall block diagram, and FIGS. 3 and 4 are respectively. First
FIG. 5 is a block diagram of the horizontal / vertical discriminating circuit, FIG. 5 to FIG. 8 are signal waveform diagrams for explaining the operation, and FIG. 9 is a block diagram of a conventional example. (1) ... video processing circuit, (3) ... polarity reversing circuit, (5) ... video processing circuit, (7) ... sync separation circuit, (8) ... horizontal discrimination circuit, (9)
… Vertical discrimination circuit, (10)… and gate.

Claims (1)

[Scope of utility model registration request] 1. A video detection circuit for detecting a positively or negatively modulated video intermediate frequency signal, a sync separation circuit for separating a sync signal from a detection output of the detection circuit, and the separation circuit separated by the sync separation circuit. A horizontal discriminating circuit that discriminates whether the frequency of the synchronizing signal matches the horizontal frequency and outputs a horizontal discriminating signal, and whether the frequency of the synchronizing signal separated by the synchronizing separating circuit coincides with the vertical frequency. A vertical discriminating circuit that discriminates the vertical discriminant signal and outputs a vertical discriminant signal, an AND gate that takes a logical product of both discriminating signals and outputs the signal as a modulation polarity discriminating signal; A television receiver provided with a polarity reversing circuit that inverts or non-inverts the polarity of the detection output and outputs it to the video processing circuit.