JPS62140569A - Intercarrier receiver - Google Patents

Abstract

PURPOSE:To output a sound signal with excellent sound quantity by using a band pass filter so as to extract a sound intermediate frequency signal and a video intermediate frequency signal from an output signal of an intermediate frequency amplifier so as to exclude an undesired disturbing signal. CONSTITUTION:A video band pass filter 7 and a sound band pass filter 8 are set respectively to a narrow band through which a video intermediate frequency and a sound intermediate frequency pass and an undesired disturbing signal other than the video intermediate frequency signal and the sound intermediate frequency signal is eliminated. Further, the 1st AGC voltage applies automatic gain control to the base band video signal and the 2nd AGC voltage applies the automatic gain control of the sound intercarrier signal, then the level of the base band video signal and the level of the sound intercarrier signal are made respectively constant and the level difference between the base band video signal and the sound intercarrier signal is made to a desired value. Thus, no disturbing signal is superimposed on the sound signal demodulated and outputted to improve the sound quality.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intercarrier receiving device that improves the sound quality of an audio signal demodulated by a television receiver.

(Prior Art) FIG. 2 shows a block circuit diagram of an example of a conventional ink carrier receiving device in a television receiver. In FIG. 2, a television signal is tuned by a tuner, and an intermediate frequency signal whose frequency is converted to an intermediate frequency is amplified by an intermediate frequency amplifier 1.

The amplified intermediate frequency signal is fed to an intercarrier demodulator 3 after interference signals such as television signals from adjacent television broadcasting stations are removed by an intermediate frequency bandpass filter 2 . The intercarrier demodulator 3 outputs a baseband video signal, an AGC voltage corresponding to the level of the baseband video signal, and an audio intercarrier signal. The AGC voltage is applied to an intermediate frequency amplifier 1, and automatic gain control is performed so that the gain is adjusted and the level of the baseband video signal is constant. The audio ink carrier signal is passed through an ink carrier bandpass filter 4 to remove unnecessary interference signals such as video signal components, and then sent to an audio demodulator 5.
and demodulated into a baseband audio signal.

(Problems to be Solved by the Invention) By the way, in the conventional ink carrier receiving device described above, the intermediate frequency band pass filter 2 has a relatively low pass rate in order to pass both the video intermediate frequency signal and the audio intermediate frequency signal. Since the bandwidth is wide, it is not possible to completely remove the video intermediate frequency signal of an adjacent television broadcasting station, and the problem is that it is superimposed on the audio intermediate frequency signal, degrading the sound quality of the audio signal.

In addition, in order for the intercarrier demodulator 3 to output the baseband video signal and the audio intercarrier signal without interfering with each other, it is necessary to set the level of the audio ink carrier signal relative to the level of the baseband video signal, for example. It is desirable to have a predetermined value of −10 to 15 dB. However, at television broadcasting stations, video signals and audio signals are transmitted using separate transmission equipment, and the receiving level of the antenna and tuner on the receiving side tends to deviate due to differences in characteristics.As a result, the level of the baseband video signal The level of the audio intercarrier signal is 11 for
If it is lower than 5 dB, a problem arises in that interference due to the video signal component is superimposed on the audio ink carrier signal, and the sound quality of the demodulated audio signal deteriorates. On the other hand, if the level of the audio intercarrier signal is higher than 110 dB, interference caused by the audio signal component will be superimposed on the baseband video signal, causing problems such as screen deterioration such as striped patterns on the screen.・An object of the present invention is to solve the problems of the conventional ink carrier receiving device described above, and is to remove unnecessary interference signals from video intermediate frequency signals and audio intermediate frequency signals, and to remove unnecessary interference signals from baseband video signals. An object of the present invention is to provide an intercarrier receiving device in which the sound quality of a demodulated audio signal is excellent by setting a predetermined level difference between the audio intercarrier signal and the audio intercarrier signal.

(Means for Solving the Problem) In order to achieve the above object, the intercarrier receiving device of the present invention includes an intermediate frequency amplifier that amplifies an intermediate frequency signal, and an audio intermediate frequency signal and an audio intermediate frequency signal from the amplified output of the intermediate frequency amplifier. an audio bandpass filter and a video bandpass filter that respectively extract a video intermediate frequency signal; an audio intermediate frequency amplifier that amplifies the audio intermediate frequency signal extracted by the audio bandpass filter; and the audio intermediate frequency amplifier and the video band. A mixer that mixes the output signal of the pass filter, outputs a baseband video signal from the output signal of the mixer, outputs a first AGC voltage according to the level of the baseband video signal, and further outputs an audio intercarrier signal. an intercarrier demodulator that outputs a voice intercarrier signal, and a second intercarrier demodulator that outputs a
an intercarry 7-level detector that outputs an AGC voltage of 1!, adjusts the gain of the intermediate frequency amplification circuit with the first AGC voltage, and outputs the second AGC voltage of 1! The gain of the audio frequency amplifier is adjusted by the pressure.

(Function) Since the audio intermediate frequency signal and the video intermediate frequency signal are extracted from the output signal of the intermediate frequency amplifier by the audio bandpass filter and the video bandpass filter, respectively, the band of each bandpass filter is narrow and unnecessary. interference signals can be removed. moreover,
A first AGC voltage corresponding to the level of the baseband video signal output by the intercarrier demodulator is applied to the intermediate frequency amplifier to perform automatic gain control, and the intercarrier demodulator outputs the audio intermediate frequency signal to the audio amplifier that amplifies it. Since automatic gain control is performed by applying a second AGC voltage corresponding to the level of the audio intercarrier signal, it is possible to maintain a predetermined level difference between the baseband video signal and the audio intercarrier signal. Therefore, it is possible to output an audio signal with excellent sound quality.

(Description of Examples) Hereinafter, examples of the present invention will be described with reference to FIG. FIG. 1 is a block circuit diagram of an embodiment of an ink carrier receiving device of the present invention.

In FIG. 1, a television signal is tuned by a tuner, and an intermediate frequency signal whose frequency is converted to an intermediate frequency is amplified by an intermediate frequency amplifier 6. The amplified intermediate frequency signal is then given to a video band-pass filter 7 and an audio band-pass filter 8 to extract a video intermediate frequency signal and an audio intermediate frequency signal, respectively, and the audio intermediate frequency signal is an audio intermediate frequency signal. The video intermediate frequency signal is amplified by an amplifier 9 and provided to a mixer 10, and the video intermediate frequency signal is directly provided to the mixer 10. The video intermediate frequency signal and the audio intermediate frequency signal are mixed again by the mixer 10 and provided to the intercarrier demodulator 11 . The ink carrier demodulator 11 outputs a baseband video signal, a first AGC voltage corresponding to the level of the baseband video signal, and an audio intercarrier signal. The first AGC voltage is applied to an intermediate frequency amplifier 6, and automatic gain control is performed so that the gain is adjusted and the level of the baseband video signal is constant. The audio ink carrier signal has unnecessary interfering signals such as video signal components removed by an ink carrier bandpass filter 12, and is supplied to an audio demodulator 13, where it is demodulated into an audio signal.

Further, the audio ink carrier signal output from the intercarrier bandpass filter 12 is sampled by an intercarrier 7 level detector 314, and a second AGC voltage corresponding to the level of the audio intercarrier signal is output. This second AGC voltage is applied to the audio intermediate frequency amplifier 9, and automatic gain control is performed so that the gain is adjusted and the level of the audio ink carrier signal is constant.

In such a configuration, the video bandpass filter 7 and the audio bandpass filter 8 can be set to narrow bands through which the video intermediate frequency and the audio intermediate frequency pass, respectively, and prevent disturbing interference other than the video intermediate frequency signal and the audio intermediate frequency signal. The signal can be removed. Further, since the first AGC voltage performs automatic gain control of the baseband video signal, and the second AGC voltage performs automatic gain control of the audio intercarrier signal, the level of the baseband video signal and the audio intercarrier signal are The levels become constant, and the level difference between the baseband video signal and the audio ink carrier signal can be set to a desired value.

Therefore, the audio signal demodulated and output from the ink carrier receiving device has excellent sound quality without being superimposed with an interfering signal.

(Effects of the Invention) As described above, according to the intercarrier receiving device of the present invention, the output signal of the intermediate frequency amplifier is converted into an audio intermediate frequency signal and a video intermediate frequency signal by the audio bandpass filter and the video bandpass filter, respectively. , it is possible to remove unnecessary interference signals by narrowing the band of each bandpass filter. Furthermore, a first AGC voltage corresponding to the level of the baseband video signal output by the intercarrier demodulator is applied to the intermediate frequency amplifier to perform automatic gain control, and the ink carrier demodulator is applied to the audio amplifier that amplifies the audio intermediate frequency signal. Since automatic gain control is performed by applying 752 AGC voltages corresponding to the level of the audio ink carrier signal outputted by the ink carrier signal, it is possible to set the baseband video signal and the audio intercarrier signal to a predetermined level difference. Therefore, an excellent effect is achieved in that an audio signal with excellent sound quality can be output.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an embodiment of an intercarrier receiving device of the present invention, and FIG. 2 is a block circuit diagram of an example of a conventional intercarrier receiving device. 1.6: Intermediate frequency amplifier. 3.11: Intercarrier 2s1 modulator, 7: Video bandpass filter, 8: Audio bandpass filter, 9: Audio intermediate frequency amplifier, 10: Mixer, 14 knee (intercarrier level detector).

Claims (1)

[Claims] an intermediate frequency amplifier that amplifies an intermediate frequency signal; an audio bandpass filter and a video bandpass filter that extract an audio intermediate frequency signal and a video intermediate frequency signal, respectively, from the amplified output of the intermediate frequency amplifier; and extraction by the audio bandpass filter. an audio intermediate frequency amplifier that amplifies the audio intermediate frequency signal, a mixer that mixes the output signals of the audio intermediate frequency amplifier and the video bandpass filter, and a baseband video signal from the output signal of the mixer. an intercarrier demodulator that outputs a first AGC voltage corresponding to the level of this baseband video signal and further outputs an audio intercarrier signal; and an intercarrier demodulator that outputs a second AGC voltage that corresponds to the level of this audio intercarrier signal. an intercarrier level detector, configured to adjust the gain of the intermediate frequency amplifier circuit with the first AGC voltage, and adjust the gain of the audio intermediate frequency amplifier with the second AGC voltage. An intercarrier receiving device characterized by: