JPH11289499A - Television receiver - Google Patents

Abstract

(57) [Summary] In a television receiver having two tuners, a reception state is optimized for a signal state in an actual use environment. SOLUTION: A signal level difference between a reception channel and an adjacent channel is determined by using respective RF-AGC and IF.
The gain of the TV signal distributor 2 is optimally set for each channel based on the voltage difference of the AGC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a television receiver (H04N).

[0002]

2. Description of the Related Art As a conventional television receiver, as shown in Japanese Patent Application Laid-Open No. 9-247561, each desired signal level at the time of desired channel selection and adjacent channel selection is determined by RF-AGC voltage. Based on this,
It is known that the control operation characteristic of the RF-AGC is corrected for each selected channel so as to have a characteristic capable of suppressing the adjacent channel interference signal, and the RF-AGC is performed according to the corrected characteristic.

[0003]

However, such a conventional circuit has the following problems. For example, in a television receiver having two tuners, it is necessary to split a TV signal input from an antenna into two, so a TV signal distributor is required. At this time, in order to correct the deterioration of the signal-to-noise ratio due to the distribution, a TV signal distributor with an amplifier is generally provided. However, the signal is input to the tuner by setting a gain switch of the TV signal distributor. Since the signal level changes, RF-A
The optimal set point of GC changes.

[0004] Further, the signal level of the tuner is used to judge the signal level.
Since only the F-AGC voltage is used, the RF-AGC
For signals below the operation start point, the RF-AGC voltage does not change, so that there is a problem that the signal level cannot be determined.

[0005]

In order to solve the above-mentioned problems, a television receiver according to the present invention comprises a divider for dividing a TV signal into two, an amplifier for correcting a signal loss caused by the divider, and By providing a TV signal distributor having means for switching the gain of the amplifier, and having means for determining the signal level of the receiving channel and means for determining the signal level difference between the receiving channel and the adjacent channel, T
The gain of the V signal distributor is set optimally for each channel.

[0006] Thus, even in a television receiver having two tuners, an optimum reception state with respect to a signal state in an actual use environment can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a divider for dividing a TV signal into two, an amplifier for correcting a signal loss caused by the divider, and means for switching the gain of the amplifier. And a means for determining the signal level of the receiving channel and a means for determining the signal level difference between the receiving channel and the adjacent channel, so that the gain of the TV signal distributor can be optimized for each channel. It is characterized by setting, and has an effect that an optimal receiving state can be obtained in a television receiver having two tuners.

According to a second aspect of the present invention, a means for determining a signal level of a receiving channel and a means for determining a signal level difference between a receiving channel and an adjacent channel include:
RF-AGC voltage of tuner and IF-A of video detection circuit
It is characterized in that it is used in combination with GC voltage.
No special circuit is required for determining the signal level, and the combined use with the IF-AGC voltage has the effect that the determination can be made for a wide range of signal levels from a weak electric field to a strong electric field.

The third aspect of the present invention is characterized in that the setting of the gain switching of the TV signal distributor is performed at the same time as the automatic channel setting of the television receiver, and a special operation is performed for the setting. There is an effect that it is not required. Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a block diagram of a television receiver according to the present invention. Circuits deemed unnecessary for the explanation are omitted. T input from antenna 1
After switching the gain of the V signal by the gain switching signal from the microcomputer 9 by the amplifier 3, the V signal is divided into two by the distribution circuit 4 and input to the tuners 5 and 6. Tuner 5
Outputs an IF signal of the channel selected by the tuning signal from the microcomputer 9.

The video detection circuit 7 performs video detection of the IF signal,
The gain of the tuner 5 is controlled by the RF-AGC voltage 11 according to the level of the TV signal, and the IF-AGC voltage 12 is output. RF-AGC voltage 11 and IF-AG
The C voltage 12 is input from an A / D port or the like of the microcomputer 9 and stored by a storage unit such as a memory. At this time, the microcomputer 9 compares the difference between the RF-AGC voltage 11 and the IF-AGC voltage 12 in the previously stored adjacent channel and calculates the difference in signal level. For example, when it is determined that the signal level of the adjacent channel is higher than that of the reception channel, there is a possibility of interference from the adjacent channel. Therefore, the gain of the TV signal distributor is set lower.
Make it less susceptible to interference. When it is determined that the signal level of the adjacent channel is lower than the reception channel, T
The gain of the V signal divider can be set high to achieve the best signal-to-noise ratio.

FIG. 2 shows the RF-AGC voltage characteristic of the tuner with respect to the level of the TV signal and the IF-AG of the video detection circuit.
It is a figure showing C voltage characteristic. R set by microcomputer
For signal levels higher than the F-AGC operation start point, R
The F-AGC voltage increases, and conversely, the IF-AGC voltage increases for low signal levels. R for signal level determination
If only the F-AGC voltage is used, a signal lower than the RF-AGC operation start point, that is, the difference between the signal level at (point A) and the signal level at (point B) in FIG. 2 cannot be determined. By using both the RF-AGC voltage and the IF-AGC voltage, a determination can be made for a wide range of signal levels from a weak electric field to a strong electric field.

The above-described gain setting of the TV signal distributor can be performed in the automatic channel setting flowchart shown in FIG. When the automatic channel setting is executed, a channel is selected (13), and it is determined whether a signal exists in the channel (14). In that case, the channel number, the RF-AGC voltage and the IF-AGC voltage are stored (15). This is performed (16) for all channels. Then, it is determined whether there is an adjacent channel for the stored channel number (17).
If there is no adjacent channel, the gain of the TV signal distributor is set high (20). If there is an adjacent channel, the RF-AGC voltage of the receiving channel and the IF-AG
The RF voltage and the IF-AGC voltage of the adjacent channel are compared with the C voltage, and when it is determined that the signal level of the adjacent channel is high (18), the gain of the TV signal distributor is set low (19). ). If it is determined to be low, the gain of the TV signal distributor is set high (20).
I do. This setting is executed for all the stored channels (21) to complete the setting.

[0014]

As described above, according to the present invention, in a television receiver having two tuners, the reception state can be optimally set to the signal state in an actual use environment. Also, an advantageous effect that no special operation is required for setting can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of RF-AGC voltage and IF-AGC voltage characteristics according to one embodiment of the present invention;

FIG. 3 is a flowchart of automatic channel setting according to an embodiment of the present invention;

[Description of sign]

 Reference Signs List 1 antenna 2 TV signal distributor 3 amplifier 4 distributor 5 tuner 6 tuner 7 video detection circuit 8 video detection circuit 9 microcomputer 10 gain switching signal 11 RF-AGC voltage 12 IF-AGC voltage

Claims (3)

[Claims] 1. A splitter for splitting a TV signal into two, an amplifier for correcting signal loss caused by the splitter, and a TV signal splitter having gain switching means for switching the gain of the amplifier.
By having means for determining the signal level of the receiving channel and means for determining the signal level difference between the receiving channel and the adjacent channel, the gain of the TV signal distributor is optimally set for each channel. Television receiver. The means for determining the signal level of the receiving channel and the means for determining the signal level difference between the receiving channel and the adjacent channel are obtained by using both the RF-AGC voltage of the tuner and the IF-AGC voltage of the video detection circuit. The television receiver according to claim 1, wherein: 3. The television receiver according to claim 1, wherein the setting of the gain switching is performed simultaneously with the automatic channel setting of the television receiver.