JP3328926B2 - Television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a television receiver, and more particularly to a television receiver capable of controlling the output gain of a tuner.

[0002]

2. Description of the Related Art Conventionally, as a television receiver of this type, a signal selected and received by a tuner is passed through a SAW filter or the like, and a signal of an adjacent channel is removed to extract a required signal. Amplifies the high frequency and outputs the intermediate frequency signal. The output intermediate frequency signal is subjected to intermediate frequency amplification and then detected to extract an actual video signal. In many cases, an AGC function is added in order to obtain a stable video output. The function of the AGC is to feedback-control the gain of the high-frequency amplification in the tuner in accordance with the magnitude of the amplitude of the detection output, and a video signal of a constant amplitude can be obtained by the function of the AGC.

On the other hand, in the device disclosed in Japanese Utility Model Laid-Open Publication No. Sho 61-40077, data relating to the optimum rise time of the AGC circuit is stored for each channel, and the timing of the gain control of the tuner is determined based on this data. Is controlled.

[0004]

The above-mentioned conventional television receiver has the following problems.
When an adjacent channel of a receiving channel in the tuner is an actual broadcast channel, a commonly used S
The AW filter cannot completely remove the signal of the same adjacent channel, so that the video output may be disturbed. Of course, the SAW filter should have high performance,
If the signal becomes expensive and there is no disturbing signal in the adjacent channel, a normal performance SAW filter is sufficient. Therefore, if an expensive SAW filter is applied when an interfering signal does not always exist in an adjacent channel, the balance between cost and external performance may be lost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a television receiving apparatus capable of obtaining an excellent video output by reducing the influence of signals of adjacent channels with an inexpensive configuration. I do.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a channel selection receiving means capable of selectively receiving a television broadcast signal corresponding to a plurality of channel frequencies and controlling an output gain. The preset channel function detects the reception channel in the selected channel receiving means, stores information on the actual broadcast channel, searches this information, and selects one of the channels before and after the received channel in the selected channel receiving means. Output gain control means for lowering the output gain of the tuning reception means when one of the channels is an actual broadcast channel.

[0007] In the invention according to claim 1 configured as described above, the channel selection receiving means can selectively receive a television broadcast signal corresponding to a plurality of channel frequencies and control the output gain. If the channel adjacent to the reception channel in the channel selection receiving means is an actual broadcast channel, the output gain control means detects this and reduces the output gain of the channel selection receiving means. Then, as the gain decreases, the signal level of the adjacent channel also decreases. Of course, a trap or another filter may be provided at the output side to further reduce the signal of the adjacent channel. The application of the television receiver according to the present invention is not particularly limited and can be incorporated in any device that receives a television broadcast signal. Therefore, it may be incorporated in a normal television or a VCR.

Here, various modes can be considered as a specific method of detecting whether or not the channel adjacent to the reception channel in the channel selection receiving means is an actual broadcast channel. Many televisions have a so-called preset channel function and store the actual broadcast channels in a storage medium such as a memory.
By using such stored contents, it is possible to easily determine.

Therefore, the output gain control means detects the reception channel in the channel selection reception means and stores information on the actual broadcast channel. It is configured to detect whether the broadcast channel is a broadcast channel. That is, the output gain control means stores information on the actual broadcast channel by the preset channel function, and searches this information to determine whether one of the channels before and after the reception channel in the channel selection receiving means is the actual broadcast channel. If so, the output gain of the tuning receiver is reduced.

As a method of controlling the output gain of the channel selection receiving means, an AGC function has been conventionally used, and an example of a specific configuration using the AGC function is as follows. According to the invention, in the television receiving apparatus according to claim 1, the channel selection receiving means amplifies a required signal from a received signal by high frequency and outputs an intermediate frequency signal, and outputs the signal from a predetermined AGC circuit. A tuner for increasing or decreasing the output gain in accordance with the level of the AGC voltage. The output gain control means instructs the selection of the reception channel and, when the adjacent channel of the reception channel is an actual broadcast channel, the AGC. The configuration includes a microcomputer that reduces the AGC voltage output from the circuit.

In the invention according to claim 2 configured as described above, the reception channel of the tuner is selected by the microcomputer, and the tuner amplifies a required signal from the received signal at a high frequency and outputs an intermediate frequency signal. Further, this tuner is provided with an AGC output from a predetermined AGC circuit.
The output gain is increased or decreased according to the magnitude of the voltage. When the adjacent channel of the reception channel is an actual broadcast channel, the microcomputer detects and outputs A from the AGC circuit.
Decrease the GC voltage. Then, the output gain of the tuner decreases, and the signal level of the adjacent channel also decreases.

In recent years, video processing circuits including the AGC circuit are often configured as one-chip ICs.
This one-chip IC can be digitally controlled by a microcomputer via a so-called IIC bus. Therefore, in the television receiver according to claim 3,
The AGC circuit is integrally formed with a one-chip IC for video processing, and the microcomputer is a one-chip IC for the same.
C is connected to a bus so that communication is possible, and an AGC voltage output from the AGC circuit via the bus is controlled.

According to the third aspect of the present invention, the AGC circuit includes one chip I for image processing.
The one-chip IC is connected to a microcomputer via a bus so that it can communicate with the microcomputer. The microcomputer performs control to lower the AGC voltage via the bus when the channel adjacent to the reception channel in the tuner is an actual broadcast channel. Then, the AGC voltage output from the AGC circuit decreases, and the output gain of the tuner also decreases. The one-chip IC for video processing here includes various circuits related to video processing, and if it has at least an AGC circuit,
Any circuit configuration may be used. In many cases,
A video intermediate frequency circuit that amplifies the intermediate frequency signal output from the tuner, a video detection circuit that detects the amplified output, and the like are integrated into one chip.

On the other hand, there may be cases where control of the microcomputer via the bus cannot be performed, such as when the AGC circuit is an independent analog circuit. 3. In the television receiver according to 2, the AGC circuit amplifies a predetermined input voltage to output the AGC voltage, and responds to a signal input transmitted when the microcomputer reduces the AGC voltage. The configuration includes a voltage dividing circuit for dividing the input voltage.

According to the fourth aspect of the present invention, the AGC circuit amplifies a predetermined input voltage and outputs an AGC voltage, and the microcomputer sends a signal when the microcomputer lowers the AGC voltage. I do. The voltage dividing circuit operates by inputting this signal and reduces the input voltage. Then A
The AGC voltage output from the GC circuit decreases, and the output gain of the tuner also decreases.

[0016]

As described above, according to the present invention, when the adjacent channel of the reception channel is an actual broadcast channel, the output gain of the channel selection receiving means is reduced, so that the signal of the adjacent channel can be inexpensively used. It is possible to provide a television receiver capable of reducing the influence and obtaining a good video output.

Further, it is possible to easily detect whether or not the adjacent channel is an actual broadcast channel.

Further, according to the invention of claim 2,
The function of the AGC can be used, and a simple circuit configuration can be achieved.

Further, according to the invention of claim 3,
The influence of adjacent channels can be easily reduced by a simple method of controlling the bus of a one-chip IC.

Further, according to the invention of claim 4,
Even in an analog circuit that cannot be controlled by a bus, the influence of an adjacent channel can be easily reduced.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a television receiver according to a first embodiment of the present invention.
In FIG. 1, a tuner 10 tunes and receives a television broadcast wave via a receiving antenna, extracts only a required signal, amplifies it at a high frequency, and converts the signal into an intermediate frequency signal using a mixing circuit and a local oscillation circuit (not shown). Convert and output.

The tuner 10 can change the receiving channel based on an instruction from the microcomputer 20. In this embodiment, when the desired receiving channel is input by a remote controller (not shown), the microcomputer 20 detects Then, predetermined channel data corresponding to the reception channel is output to the tuner 10, and the tuner 10 tunes to a desired channel frequency based on the channel data. Also, the tuner 10 has an AGC function,
The gain of the high-frequency amplification is increased or decreased according to the level of an AGC voltage (RF AGC) input via an AGC input terminal (not shown).

The television receiver has a so-called channel preset function. When a channel preset is instructed through the remote controller, the microcomputer 20 similarly detects the instruction and continuously sets the reception channel of the tuner 10. While changing, it is determined whether or not each reception channel is an actual broadcast channel based on the presence or absence of a synchronization signal. Then, when it is determined that the broadcast channel is an actual broadcast channel, it is stored in the EEPROM 30. Then, the stored contents of the EEPROM 30 are as shown in FIG. 2, and if the microcomputer 20 searches the EEPROM 30,
It is possible to detect which channel is the actual broadcast channel. In the present embodiment, as is apparent from FIG. 3, it is assumed that television broadcast waves exist on continuous channels of “4ch” to “6ch”.

The intermediate frequency signal output from the tuner 10 is input to the one-chip IC 50 after passing through the SAW filter 40 to remove the signal of the adjacent channel. The one-chip IC 50 includes a video intermediate frequency circuit for amplifying an input signal at an intermediate frequency, a video detection circuit for video detection based on the amplified output, an AGC circuit for outputting an AGC voltage according to the magnitude of the detection output, and the like. You. And this AGC
The output gain is controlled by feeding back the voltage to the tuner 10. Of course, the gain of the intermediate frequency amplification may be controlled using the AGC voltage.

The microcomputer 20 and the one-chip IC are
It is connected by a bus and can communicate.
The one-chip IC 50 is controlled by the microcomputer 20 via the bus. Specifically, the microcomputer 20 has a clock terminal (SCL) and a data terminal (SDA),
While transmitting a clock signal of a predetermined frequency via the clock terminal, actual control data is transmitted from the data terminal in synchronization with the clock signal.

When the channel adjacent to the receiving channel in the tuner 10 is an actual broadcast channel, the signal of the adjacent channel is removed by the SAW filter 40 installed on the subsequent stage of the tuner 10 as described above. You. However, since there is usually little TV broadcast radio wave on continuous channels, high-performance S
AW filters are rarely installed. Therefore, SA
Although the signal of the adjacent channel is removed by the W filter 40, it cannot be completely removed, and noise may be mixed into the video output.

Therefore, in the present embodiment, the microcomputer 20 selects a receiving channel in the tuner 10. At this time, when the storage content of the EEPROM 30 is searched and the adjacent channel of the receiving channel is an actual broadcasting channel, One-chip IC 50 via IIC bus
To lower the AGC voltage. For example, in the present embodiment, as described above, “4ch” to “6ch”
Since TV broadcast waves exist in the continuous channel "ch", when selecting these channels, it is determined that the adjacent channel is an actual broadcast channel, and an instruction is issued to lower the AGC voltage.

Then, as shown in FIG.
The AGC circuit in 50 receives the instruction and
An AGC voltage lower than the GC voltage (indicated by a dashed line in the figure) is output. Accordingly, although the output gain of the tuner 10 also decreases, as shown in the figure, as the gain decreases, the adjacent channel component at the output of the tuner 10 also drops below the original level (two-dot chain line in the figure). , SAW filter 4
0 indicates a level that can be completely removed. Therefore, no noise is mixed into the obtained video output, and a good video output can be obtained.

Next, the operation of this embodiment configured as described above will be described. First, when a channel preset is instructed by a remote controller (not shown), the microcomputer 20 detects and continuously changes the reception channel of the tuner 10 and determines whether or not each reception channel is an actual broadcast channel based on the presence or absence of a synchronization signal. Judge. Then, if it is determined that the broadcast channel is an actual broadcast channel, E
It is stored in the EPROM 30. The microcomputer 20 uses this EE
According to the information stored in the PROM 30, predetermined channel data is sent to the tuner 10, and the tuner 10 changes the receiving frequency by changing the receiving frequency based on the channel data.

The output of the tuner 10 is the SAW filter 4
After removing signals of adjacent channels via 0,
The data is input to the one-chip IC 50. This one-chip IC 50
Is firstly subjected to intermediate frequency amplification by a video intermediate frequency circuit, then video detected by a video detection circuit, and video output. Further, the AGC circuit outputs an AGC voltage according to the level of the detection output, and the AGC voltage is fed back via the AGC input terminal of the tuner 10 to control the output gain of the tuner 10.

As described above, the microcomputer 20 selects the receiving channel of the tuner 10. However, as in the case of each of the channels “4 ch” to “6 ch” in the present embodiment,
When a channel whose adjacent channel is an actual broadcast channel is selected, it is detected from the stored contents of the EEPROM 30. Then, the microcomputer 20 instructs the one-chip IC 50 to reduce the AGC voltage via the IIC bus, and in response to this instruction, the AGC circuit inside the one-chip IC 50 generates an AGC voltage lower than the original AGC voltage. Output. Then, although the output gain of the tuner 10 also decreases, the adjacent channel component at the output of the tuner 10 also drops below the original level with the decrease in the gain, and S
The level can be completely removed by the AW filter 40. Therefore, no noise is mixed into the video output,
Good video output can be obtained.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing a television receiver according to a second embodiment of the present invention.
In this case, as in the first embodiment, an AGC function for controlling the output gain of the tuner 110 is added, but the video intermediate frequency circuit (VIF) 152
And a video detection circuit (DET) 154 and an AGC circuit 15
Reference numeral 6 denotes an independent circuit.

The microcomputer 120 operates similarly to the EEPRO
When it is detected from the stored contents of M130 that the channel adjacent to the receiving channel of tuner 110 is an actual broadcast channel, the AGC voltage is reduced, but microcomputer 120 and AGC circuit 156 are not bus-connected, and Unlike the first embodiment, the AG
The C circuit 156 cannot be controlled. Therefore, in the second embodiment, a predetermined control signal is output from the microcomputer 120, and this control signal is output to the D / A converter 125.
Is input to the AGC circuit 156 as an analog signal voltage.

The AGC circuit 156 is generally configured as shown in FIG. 5, and outputs the detection output of the video detection circuit 154 to the AGC circuit 156.
The AGC voltage is detected by the detection unit 156a and the AGC amplification unit 156b performs negative feedback amplification on the divided output of the predetermined input voltage (+ B). That is, the output AGC voltage increases when the level of the detection output in the AGC detection unit 156a is low, and the output AGC voltage decreases when the level of the detection output is high. Here, a resistor R is connected between the input terminal of the input voltage to the AGC amplifier 156b and the AGC amplifier 156b.
1 and a voltage dividing circuit composed of the switching transistor STr, the signal voltage from the D / A converter 125 is applied to the base of the switching transistor STr.

That is, when the channel adjacent to the reception channel in the tuner 110 is an actual broadcast channel, the microcomputer 120 and the D / A converter 125
, A signal voltage is applied to the base of the switching transistor STr, and the collector-emitter conducts.
Then, the input voltage to the AGC amplifier 156b is the resistance R
The pressure is further reduced by being divided by 1. As a result, the output AGC voltage is reduced, the output gain of tuner 110 is reduced, and the adjacent channel component is also reduced. Of course, also in the present embodiment, since the SAW filter 140 is provided on the subsequent stage of the tuner 110, adjacent channel components in the output of the tuner 110 are completely removed, and a good video output is obtained.

As described above, the tuner 10 includes the microcomputer 2
0 when the desired channel is received based on the instruction of 0 and the output gain is controlled based on the AGC voltage generated in the one-chip IC 50.
0 indicates that the AGC voltage output from the one-chip IC 50 is reduced when the adjacent channel of the receiving channel in the tuner 10 is an actual broadcast channel. A television receiving device capable of obtaining a good video output by using the same can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a television receiver according to a first embodiment of the present invention.

FIG. 2 is a table schematically showing contents stored in an EEPROM.

FIG. 3 is a timing chart showing a relationship between an AGC voltage and an adjacent channel component in a tuner output.

FIG. 4 is a block diagram of a television receiver according to the first embodiment of the present invention.

FIG. 5 is a simple block diagram illustrating a circuit configuration of an AGC circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Tuner 20 ... Microcomputer 30 ... EEPROM 40 ... SAW filter 50 ... One chip IC

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03G 3/30 H04N 5/52 H04B 1/10

Claims (4)

(57) [Claims] 1. A channel selection receiving means capable of selectively receiving a television broadcast signal corresponding to a plurality of channel frequencies and controlling an output gain, detecting a reception channel in the same channel reception means by a preset channel function, and The information on the broadcast channel is stored, and this information is searched for, and if one of the channels before and after the reception channel in the channel selection receiving means is an actual broadcast channel, the output gain of the channel selection receiving means is adjusted. A television receiver comprising: output gain control means for reducing the output gain. 2. The television receiver according to claim 1, wherein said channel selection receiving means amplifies a required signal from a received signal at a high frequency, outputs an intermediate frequency signal, and outputs a signal from a predetermined AGC circuit. A tuner for increasing or decreasing the output gain according to the level of the AGC voltage to be received. The output gain control means selects and instructs the reception channel, and when the adjacent channel of the reception channel is an actual broadcast channel, A television receiver comprising a microcomputer for reducing an AGC voltage output from an AGC circuit. 3. The television receiver according to claim 2, wherein the AGC circuit is formed integrally with a one-chip IC for video processing, and the microcomputer is connected to the one-chip IC via a bus. A television receiver which controls the AGC voltage output from the AGC circuit via the bus. 4. The television receiver according to claim 2, wherein the AGC circuit amplifies a predetermined input voltage to output the AGC voltage, and when the microcomputer reduces the AGC voltage. A television receiver, comprising: a voltage dividing circuit that divides an input voltage according to a transmitted signal input.