JPH11289504A - Television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve disturbance caused by a signal that cannot sufficiently be eliminated by a SAW filter like a disturbing signal near a sound carrier frequency without giving effect on the sound sensitivity. SOLUTION: The television receiver is provided with an inter-carrier system video detection circuit 3 and with a trap filter circuit 5 that has a switching means with respect to a video signal that is detected, and activates the trap filter circuit 5 only when a specific channel is selected. Since the television receiver activates the trap filter circuit 5 only when a specific channel is selected, disturbance on a specific channel is improved without deteriorating the sound sensitivity. Moreover, this method has an action that does not give such an effect as deterioration in image quality for a channel not needing the trap filter circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A conventional television receiver is disclosed in
No. 4,489,893, in order to clear and receive an international standard for input terminal interference immunity such as the FTZ standard, a trap is provided in a tuner output using a regulation point frequency as a trap frequency, and a plurality of televisions There is known one that switches according to the John broadcasting system.

[0003]

However, such a conventional circuit has the following problems. In North America, the video carrier frequency of ch6 is 83.25 MH
z, the audio carrier frequency is 87.75 MHz, whereas the FM broadcast wave that can be an obstacle exists above 88.00 MHz. At this time, the voice carrier frequency of ch6 and
The difference between the FM broadcast waves is 250 KHz.

In an inter-carrier type video detection circuit, video and audio pass through the same circuit.
Can only be attenuated to a degree. That is, the above 250 KHz
As in the case of a high FM broadcast wave, it is not possible to remove an interference signal near the voice carrier frequency. As a result, F6 is applied to the signal of ch6.
When the electric field intensity of the M broadcast wave is strong, disturbing symptoms such as discoloration and image disturbance occur. For example, the interference can be improved by inserting a fixed trap filter between the tuner output and the video detection circuit. However, since the signal level of the audio carrier frequency is reduced, there is a problem that the audio sensitivity is reduced.

[0005]

In order to solve the above-mentioned problems, a television receiver according to the present invention comprises an intercarrier video detection circuit and a trap filter circuit having switching means for a video-detected video signal. And operating the trap filter only when a specific channel is selected.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises an intercarrier video detection circuit, a trap filter circuit having switching means for a detected video signal, and selects a specific channel. This is characterized in that the trap filter is operated only when the operation is performed. Since the trap filter circuit is operated only for the detected video signal, interference in a specific channel can be improved without lowering the audio sensitivity. In addition, there is an effect that a channel that does not require a trap filter circuit is not affected by image quality deterioration or the like.

[0007] The invention described in claim 2 of the present invention is characterized in that:
This is characterized in that the resonance frequency of the trap filter circuit is set in the range of 4.5 MHz to 7.0 MHz, and has an effect that it is possible to improve interference with FM broadcast waves on ch6 in North America. Hereinafter, an embodiment of the present invention 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
The V signal is input to the tuner 2. The tuner 2 outputs an IF signal of the channel selected by the tuning data 8 from the microcomputer 7. The video detection circuit 3 performs video detection on the IF signal and outputs a video signal. The trap filter circuit 4 is controlled by the microcomputer 7 in accordance with the switching signal 9, and operates the trap filter circuit 4 only on the channel for which interference needs to be improved.

At this time, since the trap filter circuit 4 is operated only for the video signal detected by the video detection, the audio sensitivity is not affected. The video signal that has passed through the trap filter circuit 4 is demodulated by a demodulation circuit 5,
Will be displayed.

For the FM interference with ch6 in North America, the resonance frequency of the trap filter is set to 4.5.
MHz to 7.0 MHz, and c
By operating the trap filter circuit only when h6 is received, interference can be improved without affecting the image quality of other channels.

In the description, the trap filter circuit is operated for the video signal after the video detection, but the same applies when the trap filter circuit is operated for the luminance signal or the chrominance signal after the Y / C separation. The effect can be obtained.

[0012]

As described above, according to the present invention, the sound sensitivity is reduced for an image generated by a signal which cannot be sufficiently removed by the SAW filter, such as an interference signal near the sound carrier frequency in a television receiver. It can be improved without doing it. According to this, for example, in North America c
h6 can be prevented from being interfered by the FM broadcast wave, and the trap filter is operated only for the video signal of the channel for which the interference needs to be improved. Therefore, an advantageous effect that the image quality of other channels is not affected at all is obtained. Can be

[Brief description of the drawings]

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

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuner 3 Video detection circuit 4 Trap filter circuit 5 Demodulation circuit 6 Image display part 7 Microcomputer 8 Tuning data 9 Switching signal

Claims (2)

[Claims] 1. An inter-carrier type video detecting circuit, and a trap filter circuit having a switching means for a video detected video signal, wherein the trap filter circuit is operated only when a specific channel is selected. A television receiver characterized by the above-mentioned. 2. The television receiver according to claim 1, wherein a resonance frequency of the trap filter circuit is in a range of 4.5 MHz to 7.0 MHz.