JP2924230B2 - Multi-system television receiver with built-in audio multiplex receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-system television receiver with a built-in audio multiplex receiver designed to reduce audio noise and improve audio signal reception sensitivity.

[0002]

2. Description of the Related Art In recent years, countries that provide audio multiplex broadcasting have increased in overseas markets. In a country adopting the PAL or SECAM color television broadcasting system, a multi-system television receiver capable of receiving a plurality of television signals has been commercialized and sold, but has a channel bandwidth of 6 MHz. At present, multi-system television receivers that can also receive signals generally do not have a built-in audio multiplex receiver.

In the above-mentioned countries, many multi-system television receivers with built-in audio multiplex receivers can generally receive only signals having a channel bandwidth of 7 MHz and 8 MHz.

An example of the above-described conventional multi-system television receiver with a built-in audio multiplex receiver will be described with reference to the drawings.

FIG. 4 is a block diagram showing audio signal processing of a conventional multi-system television receiver with a built-in audio multiplex receiver.

As shown in FIG. 4, a video signal is output from an output of the tuner 1 through an IF filter 3 (including a video intermediate frequency amplifying circuit) and a video detector 4. On the other hand, the audio signal passes through an IF filter 5 (including an audio intermediate frequency amplifier circuit) and an audio detector 6, and then a 5.5 MHz F
The output from the M detector 7 and the FM detector 8 for 5.74 MHz is applied to a German audio multiplex demodulator 9. It comprises a first audio multiplex demodulation circuit. At the same time, the output of the audio detector 6 is subjected to signal processing by a second audio multiplex demodulation circuit having a 5.85 MHz QPSK detector 10 and a NICAM type audio multiplex demodulator 11. The output of the German audio multiplex demodulator 9 and the output of the NICAM audio multiplex demodulator 11 are switched by a signal switch 12, and then amplified by an audio amplifier 13 and output as audio from a speaker 14. Is configured.

[0007] Regarding the audio signal processing of the multi-system television receiver with the built-in audio multiplex receiver configured as described above,
The operation will be described below. First, a television signal input to the tuner 1 is converted to an intermediate frequency (IF). Then, first, the IF signal is filtered by the video IF filter 3 for amplitude and phase, detected by the video signal video detector 4, and output as a video signal.
On the other hand, the IF signal is filtered by the audio IF filter 5 and then detected by the audio signal detector 6 to become an audio signal which has become an audio intermediate frequency. When receiving the German audio multiplex signal, the first audio is 5.5MHz F
The second sound detected by the M detector 7 is FM for 5.74 MHz.
The audio signal detected by the detector 8 and input to the German-type audio multiplex demodulator 9 and demodulated is converted into a signal switch 12
Is input to When a NICAM audio multiplex signal is received, the digital signal detected by the 5.85 MHz QPSK detector 10 is converted to a NICAM audio multiplex demodulator 1.
The signal is demodulated by 1 and becomes an audio signal, which is input to the signal switch 12. The audio signal selected by the signal switch 12 is
After being amplified by the audio amplifier 13, it is input to the speaker 14 and output as audio.

[0008] As another example of the conventional example, when a system having a channel bandwidth of 6 MHz is received, as shown in FIG. 5, in addition to the circuit block diagram shown in FIG. A 4.5 MHz filter 15 for extracting a 4.5 MHz audio intermediate frequency component from the output signal is a FM for audio.
In this case, the F is connected to the detector 7.
The M detector 7 detects and outputs a 4.5 MHz component audio signal. Further, in the circuit shown in FIG. 6 as another conventional example, when a system having a channel bandwidth of 6 MHz is received,
An audio IF filter 16 (including an audio intermediate frequency amplifier circuit for a channel bandwidth of 6 MHz) and an audio detector 17 are provided on the output side of the tuner 1, and the other circuits are exactly the same as those in FIG.

[0009]

However, in the above-described conventional configuration, when a system having a channel bandwidth of 6 MHz is received, that is, when an audio signal having an SIF of 4.5 MHz is to be obtained, an intercarrier beat as shown in FIG. It is necessary to obtain an FM audio signal from the output of the video detector 4 or add an additional audio IF filter to the output of the tuner 1 as shown in FIG. The sensitivity is deteriorated, and in the latter case, the circuit is complicated and the cost is increased.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. A multi-system television with a built-in audio multiplex receiver including a channel band of 6 MHz having a good audio noise and audio signal reception sensitivity without adding an audio IF filter. It is intended to provide a receiver.

[0011]

In order to achieve the above object, a multi-system television receiver with a built-in audio multiplex receiver according to the present invention is switchable between a tuner and a video and audio IF filter for a channel bandwidth of 6 MHz. I / O for audio that can pass even traps and audio signals with a channel bandwidth of 6 MHz
An F filter is provided.

[0012]

According to the present invention, there can be provided a multi-system television receiver with a built-in audio multiplex receiver capable of receiving an audio signal including a channel bandwidth of 6 MHz with good reception of the audio noise and the audio signal.

[0013]

An embodiment of the present invention will be described below with reference to FIG.

As shown in the figure, the circuits below the tuner 1 and the IF filter 3 are the same components as those of the conventional example shown in FIG. In the present invention, a newly switchable adjacent video signal trap 2 for a channel bandwidth of 6 MHz is provided. The FM detector 7 has 4.5 MHz and 5.5 MHz.
This is an FM detector for 5 MHz. The audio IF filter 5 is an audio IF filter that also passes an audio intermediate frequency signal having a channel bandwidth of 6 MHz.

Regarding the audio signal processing of the multi-system television receiver with the built-in audio multiplex receiver configured as described above,
The operation will be described below with reference to FIGS.

FIG. 2 shows a trap for adjacent video signals for a switchable channel bandwidth of 6 MHz, which is composed of a bridge T-type trap and a transistor for switching a capacitance. 7 channel bandwidth depending on the signal
It can be switched between the MHz and 8 MHz systems and the 6 MHz system.

FIG. 3 (a) is a frequency characteristic diagram of the audio IF filter, and FIG. 3 (b) is a diagram showing the trap of FIG. 2 when the trap of FIG. 2 becomes an adjacent trap for a channel bandwidth of 6 MHz. 3A shows frequency characteristics up to the IF filter.

When a signal having a channel bandwidth other than 6 MHz is received, as described in the prior art,
Fig. 3 when a signal with a channel bandwidth of 6 MHz is received.
The IF signal that has passed through the audio signal IF filter having the characteristic (b) is video-detected by the audio detector 6 and
Is FM-detected and becomes an audio signal. As described above, according to the present embodiment, by providing a switchable adjacent video signal trap for a channel bandwidth of 6 MHz and an audio IF filter that also passes an audio signal of a channel bandwidth of 6 MHz,
SIF 4.5MHz monaural audio signal and SIF 5.5MHz
Can be received with good audio noise and good reception sensitivity for audio signals, respectively.

[0019]

As apparent from the above embodiments, according to the present invention, a switchable adjacent video signal trap for a channel bandwidth of 6 MHz and an audio IF filter for passing an audio signal having a channel bandwidth of 6 MHz are provided. By
A multi-system television receiver with a built-in audio multiplex receiver having good audio noise and audio signal reception sensitivity can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of audio multiplex signal processing according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of an adjacent video signal trap for a channel bandwidth of 6 MHz in the embodiment.

3A is a frequency characteristic diagram of an audio IF filter, and FIG. 3B is a frequency characteristic diagram of an audio IF filter for a channel bandwidth of 6 MHz.

FIG. 4 is a block diagram of a conventional audio multiplex signal processing circuit.

FIG. 5 is a block diagram showing a conventional voice multiplexed signal processing circuit with a built-in 4.5 MHz filter;

FIG. 6 is a block diagram of a conventional multi-system audio multiplex signal processing circuit including a channel bandwidth of 6 MHz.

[Explanation of symbols]

 1 Tuner 2 Adjacent video signal trap for channel bandwidth 6 MHz 5 IF filter for audio signal 6 Detector for audio signal 7 4.5 and 5.5 MHz FM detector 8 5.74 MHz FM detector 9 German audio multiplex demodulator 10 5. 85MHz QPSK detector 11 NICAM type audio multiplex demodulator 12 signal switch 13 audio amplifier

Claims (3)

(57) [Claims] 1. A tuner for receiving a color television signal, an audio signal IF filter to which an IF signal from the tuner is input, and an output signal of the audio signal IF filter.
A voice signal detector for detecting the item, the speech signal
2 for FM detection of the output signal of the detector for
A first audio multiplex demodulation circuit having an FM detector and an audio multiplex demodulator of the system, and an output from the audio signal detector.
QPSK that detects the output signal and outputs it as a digital signal
A second audio multiplex demodulation circuit having a detector and an audio multiplex demodulator; a signal switch for switching between the first audio multiplex demodulation circuit output signal and the second audio multiplex demodulation circuit output signal; Chi that is tuned between the audio amplifier connected to the signal output terminal of the signal switch, the output terminal and the input terminal of the IF filter for the audio signal of the tuner
The channel selection signal in accordance with the method of Yan'neru a trap adjacent video signal switching control, the neighboring image
Depending on the insertion state of the signal trap,
From the output end of the audio signal IF filter.
A multi-system television receiver with a built-in audio multiplex receiver , characterized by being changed . Wherein adjacent audio signal trap provided between the tuner output terminal and input terminal of the audio IF filter when receiving method of channel bandwidth 6MHz said channel
2. A multi-system television with a built-in audio multiplex receiver according to claim 1, wherein switching control is performed so as to be inserted and connected by a channel selection signal when a channel having a channel width of 6 MHz is selected. Receiver. 3. A 5.5 MHz FM detector and 5.74 MH.
A first voice multiplex demodulator circuit provided with a zFM detector and a German voice multiplex demodulator, and a second voice multiplex demodulator provided with a 5.85 MHz QPSK detector and a NICAM voice multiplex demodulator.
And an adjacent video signal trap for a switchable channel bandwidth of 6 MHz.
2. A multi-system television receiver with a built-in audio multiplex receiver according to claim 1, wherein a 5 MHz monaural audio signal, a 5.5 MHz SIF German audio multiplex signal and a NICAM audio multiplex signal can be received.