JPH01194773A - Television multiple system detection circuit - Google Patents

Abstract

PURPOSE:To eliminate the influence of a chrominance signal at a PAL by constituting an intermediate frequency filter of a split/parallel SAW filter, constituting an IC of a complete synchronization detecting IC, using an intercarrier system for 4.5MHz, and setting a parallel system for 5.5MHz/6.0 MHz/6.5MHz. CONSTITUTION:Only a video signal is inputted to the video intermediate frequency amplifier circuit 18 of the complete synchronization detecting IC13 by the split/parallel SAW filter 12, and a video is detected 20, and is amplified 21. A component of 4.5MHz is inputted a voice detection circuit 23 at a SIF filter 16 from the video signal that is the output of the amplifier 21, then, a voice signal is taken out. The voice of 5.5MHz/6.0MHz/6.5MHz at the PAL, after being amplified at a voice carrier amplifier 19 by the filter 12, are inputted to a mixer 22, and the detection of the voice is performed by a voltage controlled oscillator 24, and is inputted to a SIF filter 14 of 5.5MHz/6.0MHz/6.5 MHz, and only a required voice component is extracted, and is inputted to the IC15 for FM detection, then, the voice is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television multi-system detection circuit for a receiver of a video tape recorder (VTRL television, etc.).

2. Description of the Related Art In recent years, high image quality, high sound quality, and low cost have been required for RF demosimulators for VTR and television receivers, and the same requirements have also arisen for demosimulator multi-system types.

Hereinafter, an example of the above-mentioned conventional RF demosimulator multi-system type will be described with reference to the drawings.

FIG. 2 shows the circuit configuration of a conventional RF demosimulator multi-system type. In FIG. 2, 81 is an NTSC mode adjacent video trap and PA in the IF band.
This is a tuning circuit that adjusts the chroma band in the adjacent video trap in LB&G mode and the selectivity characteristic in NTSC mode. 82 is a helical filter that takes the frequency characteristics of the intermediate frequency amplification circuit. 83 is a pseudo synchronous detection IC;
Reference numeral 4 denotes an SIF filter for sending SIF from the video signal to the detection stage using the intercarrier method. 86 is an audio trap (to prevent interference with the audio of the video amplification circuit).
NTSC self-voice trap/PALB&G self-voice trap/PALI self-voice trap) circuit. 86
is an FM detection IC.

The operation of the conventional RF demosimulator multi-system type configured as described above will be described below.

First, in the trap circuit 81, each mode (N
A trap circuit corresponding to TSC-M/PALB&G/PALI is made compatible by performing nuitching with a diode using an external voltage input.

Further, the helical filter 82 has frequency characteristics in a wide band so as to be compatible with all modes, and the trap circuit 81 switches the frequency characteristics to each mode. Reference numeral 83 is a pseudo synchronous detection IC which has intermediate frequency amplification, video amplification, and detection circuits, and is used to weave audio interference when performing video amplification in the self-audio trap circuit 85, but the frequency of the self-audio trap varies depending on each mode. Because of the difference in voltage, an external voltage is applied to the diode to prevent the switching interference beat. Reference numeral 84 is a circuit that outputs SIF using only the intercarrier method, and the SIF filter is also configured to perform nwitching on a diode using an external voltage so as to be compatible with each mode.

Problems to be Solved by the Invention However, in the case of the above configuration, a trap circuit is required depending on each broadcasting system, and the cost is high.
An IF filter is used, but PAL, 5MHz/8.
0M1-h/6.5MHz) and 4.5MH of NTSC
When using the z filter at the same time, in the case of PAL, the color signal is 4.43MH2, and the color signal 4 passes through the aMH2 SIF filter and affects the audio side, so another FM detection IC is required. The problem is that it is expensive and difficult to design.

In view of the above problems, the present invention provides an intermediate frequency filter.
Parallel SAW filter, the IC is a fully synchronous detection IC4. sMh using intercarrier method, and 6.6M
Hermitage/6. OMH, /6.5M ratio split parallel S
To provide a television multi-system detection circuit which uses a parallel system using an AW filter', eliminates the influence of color signals in PAL, and can be inexpensive.

Means for Solving the Problems In order to solve the above problems, the television multi-system detection circuit of the present invention includes completely synchronous detection means having a video intermediate frequency amplification circuit, an audio amplification circuit, and an audio detection circuit, and from the output of a tuner. An intermediate frequency characteristic trap circuit that switches the self-audio trap in the IF band, and a video signal from the signal trapped by the intermediate frequency characteristic trap circuit as an intermediate frequency filter is output to a video intermediate frequency amplification circuit, and an audio signal is output to an audio amplification circuit. The audio intermediate frequency filter outputs an audio intermediate frequency component from the amplified video signal to the audio detection circuit.

Effect The present invention has the above-described configuration, for example, extracts audio from the 4.5 MHz side using the intercarrier method, inputs it to the audio detection circuit of the fully synchronous detection means, and detects s, aMH, /e.
, o MF-Iz/ 6.5 MH2 by a Nufrit parallel SAW filter.
FM detection is performed using an external detection IC.
Detection can be performed using the FM detection IC, the influence of color signal components on audio is eliminated, and only one external FM detection IC can be used, making the design easy and inexpensive.

Embodiments Hereinafter, television multi-system detection circuits according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a television multi-system detection circuit according to a first embodiment of the present invention. In Figure 1, 11 is I
I fp in NTSC mode in F band 4-5
12 is a split parallel SAW filter that takes the intermediate frequency characteristic and inputs it to the video circuit and the audio circuit. 13 is a fully synchronous detection IC whose phase is synchronized with the video intermediate frequency by a voltage controlled oscillator 24. 14 is s, s
MHz/6.0MHz/6.5 MHz audio intermediate frequency (hereinafter referred to as SIF) filter; 15 is an FM detection IC; 1ei is a 44.5MHz SIF filter; 1 is a tuner.

The operation of the television multi-system detection circuit configured as described above will be explained below with reference to FIG.

In FIG. 1, split parallel SAW filter 1
2, only the video signal is input to the video intermediate frequency amplification circuit 18 of the fully synchronous detection ICl 3, and then the phase is synchronized with the voltage controlled oscillator (VCO) 24, the video is detected by the detection circuit 2o, and the video is amplified by the video amplification circuit 21. let From the output video signal, the 4.tsMH component is completely synchronously detected by the SIF filter 16 for 4.6MH.
The signal is input to the audio detection circuit 23 of No. 3, and the audio signal is extracted.

FIG. 3 shows the frequency characteristics of the 4.5 MH, S IF filter 16, which has frequency characteristics so that only the 4.5 MH, S M 82 component can be extracted from the video signal. Based on the above contents, the 4.5 MHz audio component is extracted. Also, F
AI, 6.5 MHz / 6.0 M) h /
6.5 M)h audio is input to the audio carrier amplifier 19 of the fully synchronous detection ICl 3 by the split parallel SAW filter 12 and amplified, and then input to the mixer 22 and detected by the voltage controlled oscillator 24. 5.5 Ml-1,/6.0M)h/6.5
M) h(7) S I F 7 is inputted to the file p14 to reduce only necessary audio components, and inputted to the FM detection ICl3 to perform FM detection and output audio.

Figure 4 shows PAL no 5.5 MHz/6. O
MHz/e,s is the SIF frequency characteristic of Peng, and the required frequency is 5.0 Peng/e,o MHz/e,t
It has frequency characteristics so that only the component of s M )tz can be extracted.

As described above, according to this embodiment, the 4.5 MHz audio component is based on the intercarrier system from the video, 5.5 MHz).

/ 6. By using a split parallel SAW filter, the audio component of OM ) lz / 6.5 M Hl / 6.5 M) can be processed in parallel mode, and by using the intercarrier method and parallel method simultaneously, it can be processed in PAL mode (5,5 M Hl / 6.5 M Hl / 6.5 M Hl / 6.5 M). OMda/e, csMH
, ) are eliminated from the influence of the color signal on the sound, and the design can be done at a low cost.

Effects of the Invention As described above, the present invention provides an excellent television multi-system detection circuit in which the influence of color signal components on audio is eliminated, the design is easy, and the design can be done at a low cost. effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a television multi-system detection circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional television multi-system detection circuit, and FIG. 3 is a block diagram of a conventional television multi-system detection circuit. .5M) h side frequency characteristic diagram, Figure 4 shows the 5.0M) 4z/6. OM)-
It is a frequency characteristic diagram of 1z/6.5MHz. 11...Intermediate frequency characteristic trap circuit, 12.
...Split parallel SAW filter, 13.
...Fully synchronous detection IC, 14...5.5M
)h/6. OMHz/6.5 MH, S IF filter, 15-°-FM detection IC.

Claims (1)

[Claims] Completely synchronous detection circuit means used for multiple broadcasting systems in high frequency signal demodulation circuits of receivers including VTRs and televisions, and has a video intermediate frequency amplification circuit, an audio amplification circuit, and an audio detection circuit, and an IF from the output of a tuner. an intermediate frequency characteristic trap circuit that switches self-sound traps in the band;
A split parallel SAW filter outputs a video signal from the signal trapped by the intermediate frequency characteristic trap circuit to the video intermediate frequency amplification circuit, and outputs an audio signal to the audio amplification circuit; A television multi-system detection circuit comprising: an audio intermediate frequency filter that outputs frequency components to the audio detection circuit.