JPH06284358A - Television receiver - Google Patents

Abstract

PURPOSE:To provide a television receiver capable of effectively utilizing intercarrier ICs and also reducing the number of the intercarrier ICs. CONSTITUTION:This television receiver for demodulating television signals including AM-modulated audio signals and video signals and taking out the autio signals and the video signals is constituted of a video/audio SAW filter 13, a video AM detection part 15 and an audio filter 18 for extracting audio intermediate frequency signals from the television signals, an electronic volume amplifier 19 and a limiter 20 for amplifying the audio intermediate frequency signals at a level where the limiter is not operated and an AM detector 21 for AM-detecting the amplified audio intermediate frequency signals and taking out the audio signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver for demodulating an AM-modulated audio signal such as a SECAM television broadcast.

[0002]

2. Description of the Related Art FIG. 2 shows a separate carrier circuit for demodulating an AM-modulated audio signal in a conventional SECAM television broadcast. That is, the SECAM television broadcast signal is received by the receiving antenna 1 and input to the tuner 2. This tuner 2 is a receiving antenna 1
A desired frequency is selected from the television broadcast signal input from the converter, converted to an intermediate frequency signal, and output to the video SAW filter 3 and the audio SAW filter 4. The image SAW
The filter 3 extracts the intermediate frequency signal of only the image from the intermediate frequency signal input from the tuner 2 and outputs it to the image AM detection section 601 of the first intercarrier IC 501 including the image AM detection section 601 and the audio FM detection section 701. To do. The video AM detection unit 601 performs AM detection demodulation of the video intermediate frequency signal input from the video SAW filter 3 and outputs a video signal SV. On the other hand, the audio SAW filter 4 extracts the intermediate frequency signal of only the audio from the intermediate frequency signal input from the tuner 2, and the video AM detection unit 60
2 and the audio FM detection unit 702, and outputs to the video AM detection unit 602 of the second intercarrier IC 502. The video AM detection unit 602 performs AM detection demodulation on the audio intermediate frequency signal input from the audio SAW filter 4 and outputs the audio signal SS.

[0003]

However, in the conventional separate carrier circuit, the audio FM detectors 701 and 7 in the two intercarrier ICs 501 and 502 are provided.
02 is unnecessary, inter-carrier IC and SA
There is a drawback that two W filters are required for each.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a television receiver capable of effectively utilizing intercarrier ICs and reducing the number of intercarrier ICs.

[0005]

In order to solve the above problems, a television receiver of the present invention is a television receiver for demodulating a television signal containing an AM-modulated audio signal and a video signal to extract an audio signal and a video signal. In the machine, an audio intermediate frequency signal is extracted from the television signal, the audio intermediate frequency signal is amplified at a level at which a limiter does not work, and the amplified audio intermediate frequency signal is subjected to AM detection to extract an audio signal. It is a thing.

Further, the television receiver of the present invention includes a receiving means for receiving a television signal including an AM-modulated audio signal and a video signal, and a television radio wave received by the receiving means to a video / audio intermediate frequency signal. And a video / audio AM detection means for AM-detecting the video / audio intermediate frequency signal converted by the frequency conversion means to extract the video-audio intermediate frequency signal AM-detected, and the video / audio AM
A video signal extracting means for extracting a video signal from the video / audio intermediate frequency signal AM-detected by the detecting means, and an audio intermediate frequency signal extracting means for extracting an audio intermediate frequency signal from the AM-detected video / audio intermediate frequency signal. , An amplifying means for amplifying the audio intermediate frequency signal extracted by the audio intermediate frequency signal extracting means at a level at which the limiter of the FM detecting section does not work, and the audio intermediate frequency signal amplified by the amplifying means is AM detected to obtain a voice signal. And a voice AM detecting means for extracting the voice AM.

Further, the television receiver of the present invention includes an antenna for receiving a television signal including an AM-modulated audio signal and a video signal, a tuner for converting the television signal received by the antenna into an intermediate frequency signal, and a tuner for converting the television signal to an intermediate frequency signal. Video / audio SAW filter that extracts the video / audio intermediate frequency signal from the intermediate frequency signal converted by the tuner, and video AM of the inter-carrier IC that AM detects the video / audio intermediate frequency signal extracted from this video / audio SAW filter A detection unit, an audio trap for extracting a video signal from the AM detection video / audio intermediate frequency signal output from the video AM detection unit, and an audio filter for extracting an audio intermediate frequency signal from the AM detection video / audio intermediate frequency signal The audio intermediate frequency signal extracted from this audio filter is used as the intermediate frequency signal of the video AM detection section. An electronic volume amplifier for controlling to a level at which the limiter does not work by using a gain control signal, a limiter provided in an audio FM detection section of an intercarrier IC for amplifying an audio intermediate frequency signal output from the electronic volume amplifier, and An AM detector that demodulates the audio intermediate frequency signal output from the limiter and extracts the audio signal is provided.

[0008]

According to the present invention, the number of intercarrier ICs is reduced by the above means by effectively utilizing intercarrier ICs and performing voice demodulation by the intercarrier system in the SECAM system in which the voice modulation system is amplitude modulation. be able to.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a structural explanatory view showing an embodiment of the present invention. That is, the SECAM television broadcast signal is received by the receiving antenna 11 and input to the tuner 12. The tuner 12 selects a desired frequency from the television broadcast signal input from the receiving antenna 11, converts it into an intermediate frequency signal, and outputs it to the video / audio SAW filter 13. The video / audio SAW filter 13 extracts the video / audio intermediate frequency signal from the intermediate frequency signal input from the tuner 12, and the video AM detector 15 and the audio F
The signal is output to the video AM detection unit 15 of the intercarrier IC 14 including the M detection unit 16. This video AM detector 15
Is an audio filter 18 that AM-detects the video / audio intermediate frequency signal input from the video / audio SAW filter 13.
And output to the voice trap 17. This voice trap 1
Reference numeral 7 extracts the video signal SV from the AM detection signal input from the video AM detection unit 15. On the other hand, the video AM detection section 15 is an IF corresponding to the voltage level of the video / audio intermediate frequency signal input from the video / audio SAW filter 13.
An AGC (intermediate frequency automatic gain control) signal is output to the electronic volume amplifier 19. The audio filter 18 extracts an audio intermediate frequency signal from the AM detection signal input from the video AM detection unit 15 and outputs it to the electronic volume amplifier 19. The electronic volume amplifier 19 changes the voltage level of the audio intermediate frequency signal input from the audio filter 18 to
The limiter 2 in the audio FM detector 16 is controlled by the IF AGC signal input from the video AM detector 15.
0 outputs an audio intermediate frequency signal of a voltage level at which the limiter does not operate and outputs it to the limiter 20. The limiter 20 amplifies the audio intermediate frequency signal input from the electronic volume amplifier 19 at a voltage level at which the limiter does not operate, and outputs it to the AM detector 21. This AM detector 21 is a limiter 20.
The audio intermediate frequency signal input from is demodulated to extract the audio signal.

As described above, since it is possible to demodulate by the intercarrier system, the intercarrier I
There is an advantage that only one C is required. Further, since the limiter effectively amplifies, an amplifier is not required in the previous stage of the AM detector and can be directly input to the AM detector. Furthermore, since the audio filter is used to beat down the 39.2 MHz video / audio intermediate frequency signal to the 6.5 MHz audio intermediate frequency signal, it is not necessary to use a high frequency AM detector. There is.

[0012]

As described above, according to the present invention, it is possible to reduce the number of intercarrier ICs by effectively utilizing the intercarrier ICs and performing voice demodulation by the intercarrier system.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2A in conventional SECAM television broadcasting
It is a structure explanatory view which shows the separate carrier circuit which demodulates the audio signal which carried out M modulation.

[Explanation of symbols]

11 ... Receiving antenna, 12 ... Tuner, 13 ... Video
Audio SAW filter, 14 ... Intercarrier I
C, 15 ... Video AM detector, 16 ... Audio FM detector, 1
7 ... Voice trap, 18 ... Voice filter, 19 ... Electronic volume amplifier, 20 ... Limiter, 21 ... AM detector.

Claims (3)

[Claims] 1. A television receiver that demodulates a television signal containing an AM-modulated audio signal and video signal to extract an audio signal and a video signal, extracts an audio intermediate frequency signal from the television signal, and outputs the audio intermediate frequency signal. A television receiver characterized by amplifying a signal at a level at which a limiter does not work, AM-detecting the amplified audio intermediate frequency signal, and extracting an audio signal. 2. A receiving means for receiving a television signal including an AM-modulated audio signal and a video signal, a frequency converting means for converting a television radio wave received by the receiving means into a video / audio intermediate frequency signal, and this frequency. Video / audio AM detection means for AM-detecting the video / audio intermediate frequency signal converted by the conversion means and extracting the video / audio intermediate frequency signal subjected to AM detection, and video AM-detected by this video / audio AM detection means Video signal extracting means for extracting a video signal from the audio intermediate frequency signal, audio intermediate frequency signal extracting means for extracting an audio intermediate frequency signal from the AM-detected video / audio intermediate frequency signal, and the audio intermediate frequency signal extracting means Amplifying means for amplifying the audio intermediate frequency signal extracted in step 2 at a level at which the limiter of the FM detection part does not work, and AM detecting the audio intermediate frequency signal amplified by this amplifier A television receiver comprising: an audio AM detection means for oscillating and extracting an audio signal. 3. An antenna for receiving a television signal containing an AM-modulated audio signal and a video signal, a tuner for converting the television signal received by this antenna into an intermediate frequency signal, and an intermediate frequency signal converted by this tuner. A video / audio SAW filter for extracting a video / audio intermediate frequency signal from a video / audio SAW filter, and a video AM detection section of an intercarrier IC for AM detection of the video / audio intermediate frequency signal extracted from the video / audio SAW filter. The audio trap for extracting the video signal from the AM detected video / audio intermediate frequency signal output from the unit, the audio filter for extracting the audio intermediate frequency signal from the AM detected video / audio intermediate frequency signal, and the audio filter extracted from this audio filter The audio intermediate frequency signal is limited by using the intermediate frequency automatic gain control signal of the video AM detection section. The electronic volume amplifier for controlling the level at which the audio does not work, the limiter provided in the audio FM detection section of the intercarrier IC for amplifying the audio intermediate frequency signal output from the electronic volume amplifier, and the audio output from this limiter. A television receiver comprising: an AM detector for demodulating an intermediate frequency signal to extract an audio signal.