JPH07336623A - Video intermediate frequency amplifier - Google Patents

Abstract

PURPOSE:To reduce interference by other audio component by using one SAW filter in common for a video signal and an audio signal in the television receiver for plural audio signals employed in Europe. CONSTITUTION:The amplifier is provided with an audio mixer circuit 107 applying frequency conversion to an output signal from a high frequency amplifier 102, a local oscillator 108 for the mixer circuit 107, an audio SAW filter 110 located at an output of the audio mixer circuit 107, an audio signal demodulation circuit 111 located at an output of the audio SAW filter 110, and an audio signal discriminator 112 located at an output of the audio signal demodulation circuit 111. Then a signal from the audio signal discriminator 112 is fed to a microcomputer 109, which gives channel information to the local oscillator 108 for the audio mixer circuit 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a video intermediate used in a television receiver capable of receiving the broadcasting of different television broadcasting systems in neighboring countries such as Europe. Frequency amplifier.

[0002]

2. Description of the Related Art When neighboring countries such as Europe are broadcast by different television systems, for example, in France, the first voice is 6.5 MHz for AM and the NICAM voice is 5.85 MHz. In Germany, the first voice is FM at 5.5 MHz and the second voice is 5.74 MHz. Others In Northern Europe, audio multiplex broadcasting uses the same frequency band as Germany, but for NICAM audio, it is 5.85 MH.
z. Since the audio frequency band is different depending on the country, it is necessary to provide the SAW filter for the video intermediate frequency amplification circuit according to the audio frequency band.

FIG. 2 is a block diagram of a conventional PAL / SECAM video intermediate frequency amplifier for receiving. In FIG. 2, 201 is an antenna and 202 is a high frequency amplifier.
Reference numeral 03 is a mixer circuit, 204 is a local oscillation circuit, and 20
Reference numeral 5 is a video SAW filter, 206 is a video signal demodulation circuit, and 209 is a microcomputer.

Reference numeral 211 is a voice signal demodulation circuit, 212 is a voice signal discrimination device, 213 is an FM voice switch circuit, 214 is a NICAM voice switch circuit, 215
Is an AM voice switch circuit in VHFLOW, France.

Reference numeral 216 is a SAW filter for FM audio.
Reference numeral 17 is a SACAM filter for NICAM voice, and 218 is a SAW filter for AM voice reception in VHFLOW in France.

Reference numeral 219 is a control terminal for turning on the FM voice reception, 220 is a control terminal for turning on the NICAM voice reception, and 221 is a French VH.
It is a control terminal for turning on when receiving AM voice in FLOW.

As described above, referring to FIG. 2, the conventional PAL / SEC is used.
A video intermediate frequency amplifier for AM reception will be described. The signal received by the antenna 201 is amplified by the high frequency amplifier 202. Therefore, the signal whose frequency has been converted by the mixer circuit 203 is converted into the intermediate frequency band. The video signal in the intermediate frequency band is passed through the video SAW filter 205 to remove other audio signal components in the intermediate frequency band, and then demodulated by the video signal demodulation circuit 206.

When receiving the FM sound, the control signal from the microcomputer 209 turns on the FM sound switch circuit 213 through the control terminal 219 and transmits the signal to the FM sound SAW filter 216. Other switch circuit 2
The other SAW filters 2 and 14 and 215 are off.
No signal is transmitted to 17, 218. Further, the sound signal discriminating apparatus 212 indicates that the electric field strength has decreased, or that the number of errors in the sound demodulation signal has increased significantly for some reason.
If the judgment is made in step 1, the discrimination signal is switched to the other audio signal through the microcomputer 209, so that the other audio signal is transmitted from the control terminal to the desired switch circuit and the other audio signal is received. In this way, control is performed so that the most suitable audio broadcast can be received. The same applies when receiving other AM voice and NICAM voice signals.

[0009]

However, the above configuration requires three SAW filters for FM audio and NICAM audio, and for AM audio in VHFLOW in France, and is susceptible to interference by other audio components. .

In view of the above problems, it is an object of the present invention to configure one SAW filter for video and one for audio, and reduce the interference of other audio components.

[0011]

In order to solve the above problems, a video intermediate frequency amplifying apparatus of the present invention comprises a first mixer circuit for frequency-converting an output signal of a high frequency amplifier, and the first mixer circuit. A local oscillator, a video SAW filter to which the output of the first mixer circuit is input, and a video signal demodulation circuit to which the output of the video SAW filter is input are provided, and the output signal of the high frequency amplifier is frequency-adjusted. A second mixer circuit for conversion, a local oscillator of the second mixer circuit, an audio SAW filter having the output of the second mixer circuit as an input, and the audio SA
An audio signal demodulation circuit having the output of the W filter as an input, an audio signal discrimination device having the output of the audio signal demodulation circuit as an input, a microcomputer having the output of the audio signal discrimination device as an input, And means for transmitting channel information to the local oscillator of the second mixer circuit.

[0012]

According to the present invention, the video signal in the intermediate frequency band is converted to the video SA by the first mixer circuit by the above-mentioned configuration.
It is guided to the W filter and demodulated by the video signal demodulation circuit. The audio signal in the intermediate frequency band is guided to the desired SAW filter and demodulated by the audio signal demodulation circuit. Also, the audio signal discriminating device discriminates the audio signal and the discriminating signal is transmitted to the microcomputer, and channel information is transmitted from the microcomputer so that the optimum audio signal can always be received, and the oscillation frequency of the local oscillator of the second mixer circuit. Is controlled. In this way, one SAW filter for video and one for audio can be used, and since the SAW filter for audio only needs to pass the audio signal of one intermediate frequency band, the other intermediate frequency band of the other intermediate frequency band is used. The voice component can be attenuated, and the interference due to the voice component in the other intermediate frequency band can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A video intermediate frequency amplifying device according to one embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of a video intermediate frequency amplifier according to an embodiment of the present invention.

In FIG. 1, 101 is an antenna and 10
2 is a high frequency amplifier, 122 is a first mixer circuit,
Reference numeral 104 is a first local oscillation circuit, and 105 is a video SAW.
A filter 106 is a video signal demodulation circuit.

Reference numeral 107 is a second mixer circuit, 108 is a second local oscillation circuit, 110 is an audio SAW filter, 109 is a microcomputer, 123 is a control terminal for audio signals, and 124 is a video signal. , 111 is an audio signal demodulation circuit, and 112 is an audio signal discrimination device.

The operation of the video intermediate frequency amplifying device of one embodiment of the present invention constructed as above will be described with reference to FIG.

For example, when it is desired to receive a NICAM voice signal in France, the signal received by the antenna 101 is amplified by the high frequency amplifier 102. Therefore, the signal whose frequency has been converted by the first mixer circuit 122 is converted into the intermediate frequency band. The video signal in the intermediate frequency band is S for video.
After passing through the AW filter 105, other audio signal components in the intermediate frequency band are removed and then demodulated by the video signal demodulation circuit 106.

Here, when receiving the NICAM voice,
The control signal from the microcomputer 109 is transmitted through the voice control terminal 123 to the NICAM voice signal in the intermediate frequency band as the voice SA.
The frequency of the second local oscillation circuit 108 is controlled so as to be guided to the W filter 110, and the NICAM voice signal in the intermediate frequency band is transmitted to the voice SAW filter 110. The signal transmitted to the audio SAW filter 110 is demodulated by an audio signal demodulation circuit 111 and also an audio signal discrimination device 112.
Is determined by.

Therefore, when the voice signal discriminating apparatus 112 determines that the electric field strength is lowered or that the number of errors in the voice demodulated signal is greatly increased for some reason, the discriminant signal is transmitted to the microcomputer 109. . Then, in order to receive the other audio signal that can be more optimally received, the control signal is transmitted from the control terminal of the microcomputer 109 to the desired audio signal switch circuit. The AM audio signal, which is the audio signal of the other intermediate frequency band, is S for audio.
The frequency of the second local oscillation circuit 108 is controlled so as to be guided to the AW filter 110, and the AM audio signal in the intermediate frequency band is transmitted to the audio SAW filter 110.

Here, a description will be given using a television receiver for France. First, it is assumed that the E-55 channel is being received. Therefore, the intermediate frequency for video is 38.9.
Since it is MHz, the oscillation frequency of the first local oscillation circuit is 782.15 MHz. Therefore, the video signal in the intermediate frequency band is transmitted to the video SAW filter 105.

Assuming that a NICAM voice signal is received, the oscillation frequency of the second local oscillator circuit is 30 MHz at the center frequency of the voice SAW filter 110.
Then, it becomes 779.1 MHz. When the voice signal discriminating apparatus 112 determines that the number of errors in the voice demodulation signal has greatly increased due to a decrease in electric field strength or for some reason, the discrimination signal is transmitted to the microcomputer 109.

Then, in order to receive the AM audio signal which is the other audio signal which can be received more optimally, the AM audio in the intermediate frequency band is guided to the audio SAW filter 110 from the control terminal 123 of the microcomputer 109. The frequency of the second local oscillation circuit 108 is controlled to 779.75M.
Oscillates Hz. Then, the AM audio signal in the intermediate frequency band is transmitted to the audio SAW filter 110. Next, as for the bandwidth of the audio SAW filter 110, it suffices that the bandwidth is such that only one audio signal can pass, so that another audio signal can be attenuated and the interference is less likely to occur. can do.

[0023]

As described above, according to the present invention, it is possible to configure one SAW filter for video and one SAW filter for audio, and reduce interference of other audio components.

[Brief description of drawings]

FIG. 1 is a block diagram of a video intermediate frequency amplifier according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional video intermediate frequency amplifier.

[Explanation of symbols]

101 Antenna 102 High Frequency Amplifier 104 First Local Oscillation Circuit 105 Video SAW Filter 106 Video Signal Demodulation Circuit 107 Second Mixer Circuit 108 Second Local Oscillation Circuit 109 Microcomputer 110 Audio SAW Filter 111 Audio Signal Demodulation Circuit 112 Audio Signal Discrimination device 122 First mixer circuit 123 Control terminal for audio signal 124 Control terminal for video signal 201 Antenna 202 High frequency amplifier 203 Mixer circuit 204 Local oscillation circuit 205 Video SAW filter 206 Video signal demodulation circuit 209 Microcomputer 211 Audio signal demodulation Circuit 212 Voice signal discrimination device 213 FM voice switch circuit 214 NICAM voice switch circuit 215 AM voice switch circuit 216 FM voice SAW switch in VHFLOW, France Ruta 217 NICAM S for AM voice in the speech for the SAW filter 218 French VHFLOW
AW filter 219 Control terminal for turning on when receiving FM voice 220 Control terminal for turning on when receiving NICAM voice 221 Control terminal for turning on when receiving AM voice in VHFLOW in France

Claims (1)

[Claims] 1. A first mixer circuit for frequency-converting an output signal of a high-frequency amplifier, a local oscillator of the first mixer circuit, and a video SAW filter having an output of the first mixer circuit as an input. A video signal demodulation circuit that receives the output of the video SAW filter is provided, and further, a second mixer circuit that frequency-converts the output signal of the high frequency amplifier; and a local oscillator of the second mixer circuit,
An audio SA having the output of the second mixer circuit as an input
A W filter, an audio signal demodulation circuit that receives the output of the audio SAW filter, an audio signal determination device that receives the output of the audio signal demodulation circuit, and a microcomputer that receives the output of the audio signal determination device. And a means for transmitting channel information from the microcomputer to the local oscillator of the second mixer circuit.