JPS60139079A - Channel selection circuit of television receiver - Google Patents

Abstract

PURPOSE:To simplify the constitution of a channel selection circuit and to attain the assured automatic discrimination of a broadcast system, by switching an IF selecting circuit which discriminates the broadcast system from the inter-carrier component obtained through an IF amplification/wave detection circuit. CONSTITUTION:A VHF low channel of a CCIR-B system is selected by a channel selection circuit main body 10 and converted into IF signals by an electronic tuner circuit 1. These IF signals are applied to an IF selecting circuit 2 and a tuning circuit 8. A sound carrier wave of the CCIR-B system is extracted through the circuit 8 at a prescribed level and applied to an OR circuit 11. The IF signal selected by the circuit 2 is applied to the circuit, and added with the sound carrier wave. The output of the circuit 11 is applied to an IF amplification/wave detection circuit 3, and the signal amplified and wave detected by the circuit 3 is applied to a discrimination circuit 7. The circuit 7 discriminates that a channel of the CCIR-B system is selected. Then the circuit 3 is controlled to select the IF signal assuredly out of the circuit 11. Thus the automatic discrimination is possible for a broadcast system with a simple circuit constitution.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a channel selection circuit for a television receiver, and in particular, it has a CCI R-L system VHF tuner and a CCI R-L system VHF tuner.
The present invention relates to a channel selection circuit for a television receiver that also receives R-B broadcasting.

[Prior art]

Conventionally, there has been a device of this type as shown in FIG.

In the figure, l is an electronic tuner circuit having a CCI R-L system tuner, and 2 is an intermediate frequency (hereinafter referred to as IF).
iI! The selection circuits 3 and 6 are the first and second selection circuits, respectively. A second IF amplification/detection circuit, 4 a tuning voltage supply tuning circuit, 5 a band selection switch, and 7 a discrimination circuit, the electronic tuner circuit 1 and the tuning voltage supply tuning circuit 4 connect the tuning circuit main body 1.
0 is configured.

Next, the operation will be explained.

First, when selecting a channel, switch the band selection switch 5 to select the three stations VL and VH.

U (corresponding to VHF low channel, VHF high channel, and UHF channel respectively), change the tuning voltage of the tuning circuit 4 from low to high, stop at the desired channel, and adjust the tuning at that time. Store the voltage and band status in this.

The predetermined television broadcast signal thus selected is converted into an intermediate frequency by a frequency conversion circuit provided within the tuner circuit 1. Next, the signal converted to this intermediate frequency is passed through an IF with IF selection characteristics as shown in Figure 3.
It is input to the first IF amplification/detection circuit 3 via the selection circuit 2, and is amplified and detected by the circuit 3 to produce a video signal and a video signal, respectively.
An audio signal is output.

Here, the CCIR-L method and the CCI R-B method differ in the modulation method etc. of the video carrier wave, and therefore
This receiver has a CIR-L tuner.
When receiving a CIR-B broadcast, it is first necessary to determine that the received broadcast is a CCI RB-B broadcast, and thereby change the demodulation method in the first IF amplification/detection circuit 3. At this time, both types of discrimination are performed by using the difference in frequency (intercarrier frequency) between the video carrier wave and the audio carrier wave, but C
As for the VHF low channel of the CIR-L system, the hetero gain system is different, so the configuration for discrimination is extremely complicated.

This will be explained in more detail. First, the CCI'R-L type VHF tuner is an upper hetero gain type in the VIIF low channel, and this CCI'R-L type VHF tuner is an upper hetero gain type in the VIIF low channel.
In the V 11 F low channel of the L system, the broadcast video carrier frequency is higher than the audio carrier frequency. On the other hand, C
In the case of the CI R-B system, the video carrier wave of VHF low channel broadcasting is lower in frequency than the audio carrier wave.

Now, if we assume that the conventional configuration shown in Fig.
By adding the output of the first IF amplification/detection circuit 3 to the discrimination circuit 7 without providing the IF amplification/detection diagram g & 6, the V
Consider the case of receiving an HF low channel.

In this case, the V HF tuner of this device is set to V HF tuner as described above.
The HF low channel uses an upper hetero gain system, so when receiving CCIR-B broadcasting, the audio carrier frequency should originally be higher than the video carrier frequency in that system, but that frequency is higher than the video carrier frequency. The vertical relationship is reversed and input to the IF selection circuit 2. This IF selection circuit 2 has an IFii as shown in FIG.
! For each carrier in the CCI R-L system, the video carrier has 21 points and the color subcarrier has C1.
The audio carrier wave is in the receiving state at 31 points. When each carrier wave of the CCI R-B system whose frequency relationship is reversed is input to such an IF selection circuit 2, the video carrier wave is in the receiving state at 21 points, and the audio carrier wave is in the receiving state at 8 points.
At 2 points, the reception status is reached. Therefore, this audio carrier wave is considerably attenuated compared to the video carrier wave, and the first IP amplification/detection diagram vPi3
Therefore, the corresponding! No frequency component (intercarrier) of the difference between the video carrier wave and the audio carrier wave is generated in the output of the F amplification/detection circuit 3, and the result is that it cannot be determined that the broadcast is based on the CCIR-B system.

Therefore, in the conventional device, a second IF amplification/detection circuit 6 is provided, which amplifies and detects the signal that does not pass through the IF selection circuit 2, and a discrimination circuit 7 detects the presence or absence of an intercarrier in the CCIR-B method. That's what I was doing.

Conventional television receivers perform CCIR as described above.
Although the system is designed to automatically determine the difference between the two broadcasting systems, the -L system and the CCIR-B system, the configuration is complicated and the cost increases.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and extracts the audio carrier wave of a predetermined broadcasting system from the signal before passing through the IF selection circuit, and combines this with the output of the IF selection circuit. By adding this to the IF amplification/detection circuit to generate intercarrier components for each broadcasting system, or by providing an IF selection circuit for each broadcasting system, it is possible to generate intercarrier components from the intercarrier components obtained by the above IF amplification/detection circuit. The purpose of the present invention is to provide a channel selection circuit for a television receiver that can reliably automatically discriminate the broadcasting system with a simple configuration by discriminating the broadcasting system and switching the IF selection circuit to be used. .

[N embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a channel selection circuit for a television receiver according to an embodiment of the first invention of the present application, and in the figure, the same reference numerals as in FIG. 1 indicate the same parts. 8 is a tuning circuit to which the signal before passing through the IF selection circuit 2, that is, the output signal of the electronic tuner circuit 1 is inputted.

This tuning circuit 8 resonates in series at a frequency lower than the video carrier frequency of the CCI R-L system, which is the intercarrier frequency of the CCI R-B system, and therefore the output of the tuning circuit 8 has CCI I? -The audio carrier wave of the B method is extracted at a predetermined level. 1
Reference numeral 1 denotes an OR circuit which simultaneously applies output signals from the IF selection path 2 and the tuning circuit to the IF amplification/detection circuit 3. 7 is a discrimination circuit, which is the IP selection/detection circuit 3
According to the output of the IF amplifying/detecting circuit 3, it is determined which broadcasting system, CCI R-L or B, is being received, and the operating state of the IF amplification/detection circuit 3 is switched according to the result of the determination.

Next, the operation will be explained.

Operations other than when receiving the VHF low channel of the CCI R-B system are performed in exactly the same manner as in the prior art, and therefore their explanation will be omitted.

In this embodiment, when the Vl (F low channel of the CCIR-B system is tuned by the tuning circuit main body 10, the received signal is converted to an intermediate frequency by the electronic tuner circuit 1, and the I
The F-fold signal is input to the IF selection circuit 2 and the tuning circuit 8.

Here, the audio carrier wave of the signal that has passed through the IF selection circuit 2 is considerably attenuated and applied to the IF amplification/detection circuit 3 as in the conventional case. The extracted CCI R-B audio carrier wave is also added, and therefore the level of the CeIR-B audio carrier wave input to the IF amplification/detection circuit 3 increases. The level of each carrier wave input to the IF amplification/detection circuit 3 at this time is shown in FIG. Therefore, an intercarrier component of the CCI R-B system is generated in the output of the IF amplification/detection circuit 3, and the discriminator circuit 7 that receives this determines that the received broadcasting system is the CCI R-B system, and The reception state of the IF amplification/detection circuit 3 is switched by the discrimination output.

In this way, in the device of this embodiment, by simply adding one tuning circuit 8, the IF for generating the signal to be applied to the discrimination circuit 7 can be
The amplification/detection circuit can be omitted, and the circuit can be simplified and the number of parts can be reduced by two.

FIG. 5 shows an embodiment of the second invention of the present application,
This is used by the discrimination output of the discrimination circuit 7! The F selection circuit is switched. In the figure, the second
The same reference numerals as those in the figure indicate the same parts, and 2a and 2b are respectively shown in FIG. Reference numeral 10 denotes a first IF selection circuit for selecting either one of the IF selection circuits 2a and 2b according to the discrimination output of the discrimination circuit 7.
．． This is the second switch.

Next, the operation will be explained.

In this device, the changeover switch 9.10 typically
As shown in FIG. 5, it is connected to the IF selection circuit 2a for the CCI R-L system. In this situation, CCI
When R-B broadcasting is selected, the operation is similar to that of the device shown in FIG. Therefore, the output of the IF amplification/detection circuit 3 is CC
IRB intercarriers occur. As a result, the determination circuit 7 determines that the received broadcasting system is the CCIR-B system, and the first . The second switches 9 and 10 are switched to the IF selection circuit 2b side for the CCIR-B system.

Therefore, the signal from the electronic tuner circuit 1 is input to the IF selection circuit 2b for the ccrR-B system, and the IF is selected using the IFili selection characteristic shown in FIG. Amplified by amplification detection circuit 3,
The signals are detected, thereby obtaining the video signal and audio signal of the desired channel.

In the apparatus of this embodiment as well, automatic discrimination of the broadcast system can be reliably performed with a simple circuit configuration.

〔Effect of the invention〕

As described above, according to the channel selection circuit of the television receiver according to the present invention, the audio carrier wave of a predetermined broadcasting system is extracted from the signal before passing through the IF selection circuit, and this and the audio carrier wave of the above-mentioned IF selection circuit are extracted.
The output of the selection circuit is added to the IF amplification/detection circuit at the same time to generate intercarrier components for each broadcasting system, which simplifies the circuit configuration and reduces costs by reducing the number of parts and improves reliability. There is an effect that can be done. In addition, an IF selection circuit for each broadcasting system is provided, and the IF selection circuit that uses the IF selection circuit, which distinguishes the broadcasting system from the intercarrier components obtained by the above-mentioned IF amplification/detection circuit, is switched. It has the effect of automatically determining the

[Brief explanation of drawings]

FIG. 1 is a block diagram of a tuning circuit of a conventional television receiver, FIG. 2 is a block diagram of a tuning circuit of a television receiver according to an embodiment of the first invention of the present application, and FIG.
1 is a diagram showing the IF selection characteristics of the device in FIG. 1, FIG. 4 is a diagram for explaining the operation of the device in FIG. 2, and FIG. 5 is a television according to an embodiment of the second invention of the present application. FIG. 6 is a block diagram of the channel selection circuit of the receiver (al Tbl is a diagram showing the IF selection characteristics of each of the two IP selection circuits of the device in FIG. 5. 2, 2a, 2b - IF selection circuit , 3 ・IF amplification・
Detection circuit, 7... Discrimination circuit, 8... Tuning circuit (audio carrier wave extraction means), IO... Tuning circuit main body. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent: Masuo Oiwa Figure 1 Figure 3 Figure 4 Miao Lang Soft → M Attacking Chichi → Figure 5 Figure 6 River Wave -

Claims (1)

[Claims] (11) A channel selection circuit for receiving a predetermined television broadcast in a television receiver receiving broadcasts of two different systems, the CCI R-L system and the CCIR-B system. a main body, an IFF selection circuit that selects an IF with a predetermined IFF selection characteristic for the output of the channel selection circuit main body, and an audio carrier wave of a predetermined broadcasting system by inputting the signal before passing through the IFF selection circuit. output signals from the audio carrier extraction means, the IFF selection circuit and the audio carrier extraction means are simultaneously applied, and the output signals are amplified;
An IF amplification/detection circuit for detection, and a discrimination circuit that discriminates the received broadcasting system based on the frequency difference between the video carrier wave and the audio carrier wave output from the IF amplification/detection circuit, and adds the discrimination output to the IF amplification/detection circuit. A channel selection circuit for a television receiver, characterized by comprising: (21 CCI R-L method and CCI R-B method
In the channel selection circuit of a television receiver that receives broadcasts of two different systems, the main body of the channel selection circuit for receiving a predetermined television broadcast, and the channel selection circuit for the CCT R-L system and the CCTR-B system (DTP selection) are used. 1st and 2nd I which have characteristics and perform ■F selection for the output of the above-mentioned tuning circuit main body.
The F selection selection path is provided at the input/output section of both IF selection circuits, and the IFF selection circuit is connected to the first IF selection circuit. The first IFF selection circuit switches to either one of the second IFF selection circuits. a second changeover switch; an audio carrier extraction means for inputting a signal before passing through the first or second IP selection circuit and extracting the CCIR-B or -LL system audio carrier; and the second changeover switch. and the output signal from the audio carrier extraction means are simultaneously applied and the output signal is amplified. l! in the output of the IP amplification/detection circuit and the IF amplification/detection circuit. ! 1! The received broadcasting system is determined based on the frequency difference between the image carrier wave and the audio carrier wave, and the determined output is sent to the above-mentioned IF amplification/detection circuit and the first. A channel selection circuit for a television receiver, comprising a discrimination circuit added to a second changeover switch.