JPS58100582A - Television signal automatic discrimination and switching circuit - Google Patents

Abstract

PURPOSE:To attain stable switching without malfunction, by using a crystal filter for a discrimination path of a reference signal and increasing amount of information through the use of a delay line and a synthesizer. CONSTITUTION:A burst signal picked up at a burst gate circuit 22 is inputted to a 4.25MHz crystal filter 23 and a burst signal in the SECAM signal is picked up at 1/2fH. The output of a crystal filter 23 and its 1H delayed output are synthesized at a synthesizer 25 to obtain an output of a burst signal in fH frequency. This output is inputted to a 4.25MHz crystal injection lock circuit 29 and a synchronizing detection circuit 28 via an amplifier 26 and a limiter circuit 27 for synchronizing detection. The SECAM discrimiation output can be obtained by providing the output of the circuit 28 to a discrimination output switch circuit 31 via a detection hold circuit 30.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a television signal automatic discrimination switching circuit, and is suitable for use, for example, in switching the signal mode of a video tape recorder (hereinafter referred to as VTR).

Invention technology fishing background The current televisual signal system is NT8C.

Since there are PAL and ilEcAM systems, VTRs have been developed that can be used by switching the signal reception mode to suit these systems. VTR signal processing 114
- In order to automatically switch the input signal format, it is necessary to determine the format of the input signal, but conventionally PAL, IiE
A slope detection method using an OK ceramic filler is used to determine the CAM method. This is a method that utilizes the fact that the burst signal frequency is different between the normal signal and the second signal. That is, the burst signal frequency of the armpit signal is 4.43 MHZ, and the number of burst signals IIB#jL of the seven-cam signal is sequentially divided into horizontal scanning lines (its annual wave number is 15.625 KHz) and 4.43 MHZ. 40MH
K, 4.25MHz. If you want to take advantage of this difference in signals, select the power of Seraba, Kutsuiltar, and the to-off frequency to be close to 4.40 km x m.
/4-str-) The burst signal taken out by the 1m path is sent to the cellar 2. The tough (when passed through Luther) arm signal has no level change because it is within the passband, and the 4.25 MHs component of the seven cam signal is sufficiently attenuated. : Horizontal frequency) A paddle strike signal of 440 Mus, 4.25 MH whose level changes in the thoracic phase is obtained. This (DAfv
By extracting the tM period signal using a C resonance circuit, it is possible to distinguish between the /parson signal and the second signal.

Figure 1 is a circuit that discriminates between a pulse signal and a second signal as described above, and from the circuit filter (characteristics shown in Figure 2), when a pulse signal is input, it is 4.43 MH.
When the 7-cam signal is input, the level changes at the 'Afm period'.T b 4.40
Burst signals of 4 MHz (no attenuation) and 25 MHI (attenuated) are obtained.

Therefore, when receiving a seven-cam signal, a burst signal is extracted from the output terminal KFi of the ceramic filter 11 in the form shown in Figure 3 (a) K, and this is input to the 'Afx detection circuit ZjK via the amplifier 12. . In this tumor fx detection circuit z3, a sine wave with a period of KVxfg is generated as shown in Figure 3), which is a strong fHL C resonant circuit 141fC.
is input. Since this [, C resonant circuit 14 resonates with the signal of the 'Afm period, the output of 5 so O is as shown in Fig. 3(e).
As shown, the signal is output as a sine wave of the number KAfHjIIItIL, and is converted into a DC voltage by the detection circuit 15. This DC voltage drives the discrimination output switch circuit 16,
SECAM discrimination output can be obtained. On the other hand, when the /4 signal is received, the KFi, 'AfxlU phase component cannot be obtained, so the '4fHLC resonant circuit 14 cannot obtain a resonant output. Therefore, the discrimination output switch circuit 16 does not respond, and its output is Can be used for pulse signal discrimination.

Problems with the Background Art The above-described discriminating circuit has the drawback that the KIA operation is likely to occur when there is a lot of noise, such as during a weak electric field of a /4 signal or when a still image (still reproduction in a VTRK) is generated.

This is slow when the noise component is around 4.25 Wm*! This is because the signal is condensed and detected as an AfM cycle signal by wave detection. In order to reduce such malfunctions, it is possible to set the switching threshold and hold level in consideration of noise components, or to increase the time constant of the detection circuit, that is, to use a capacitor with a large capacity. The time until switching becomes longer, and the detection output level fluctuates due to fluctuations in the burst signal level.
Nurefushi in anticipation of those fluctuations. Hold levels must be set, resulting in design difficulties.

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an automatic telephonic signal discrimination switching circuit that is free from malfunctions, provides stable switching, and has good responsiveness.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned objects, the present invention uses: a judgment path k for the strike signal, that is, a reference signal, a crystal filter 23 which is strict with respect to the wave number response, and a delay line 24;
By using the 0 synthesis gain 25 to convert the reference signal in the 'AhslRr period into a reference signal in the fm period to increase the amount of information, and furthermore to drive the injector and inlotter circuit to obtain synchronous detection, it is possible to further increase the amount of information. This is a circuit with strict control over frequency.

Embodiments of the Invention Embodiments of the invention will be described below with reference to the drawings.611
In Fig. 14, numeral 21 is an input terminal to which a cut signal from a norl or a seven-cam system is input, and is connected to a parse) r-) circuit xzK@. The burst signal extracted by the Perstgut converter 22 is transmitted to a 4.25 MHz crystal 74.
1131fC is input. This crystal filter 2
J is capable of extracting only the 4.25 MHz signal due to its high narrowband filter characteristics.
The 4.25 MHz burst signal is K when the seven cam signal is input and is taken out at the 'Ahs period. The output of the crystal filter 21 is input to the synthesizer 25 via an IH delay f124 having a delay time of one horizontal period, and -K is directly input to the synthesizer @ZS. Therefore, when a seven-cam signal is input, a burst signal of 4.25 Wnix is obtained at the output of the combiner 25 at the fH period. This is after this
Compared to the 4.25 MHz component that cannot be darted when burst extraction is performed at the arm of the 'Afm period's ff-) Therefore, it is 4.25 k to do it with fH period.
The 0-order button ζ has the meaning of being able to increase the amount of information at 1Hz and reducing the fluctuation factors by controlling the subsequent detection level.
The Hz burst signal is amplified by an amplifier 26, stabilized by a limiter circuit 21, and then sent to a synchronous detection circuit 21 and 4.2.
5 kl; Hs is input to the crystal lock circuit 29.

As shown in Figure 5, the injector, engine, and recircuit circuit 29Fi has a red burst dart pulse (fH frequency IA> K Yob
) is turned on, and the oscillation circuit oscillates at the burst signal frequency in synchronization with the input burst signal. That is, the vibration output of the crystal oscillator 41 is the transistor (Qs) (Q
A limiter is applied via a differential amplifier consisting of
However, the output is outputted through the crystal oscillator 41 (D
It is designed to affect the vibration output, and can be affected by odd strike signals.

On the other hand, as shown in FIG.
Transistor (Qy) (Q
s ) , (Qs ) (Qte ) , (Qtt XQ
tm)K, and the transistor (Q) acts as a voltage rlLIli. Then, the base Kd of the transistor (Q@) that constituted the current source, the burst f-)
A pulse is applied to the base of the transistor (Q7), and the oscillation output of the above-mentioned injection, flow, and recirculation circuit 2# is applied to the base of the transistor (Q7). Also, the transistor (Qs) (Qst
), the outputs of the front distribution and the two-way road 2r are added to the common base. Furthermore, the base of the transistor (Qi) is a direct current/quier power supply (Es), and the transistor (Qte)
The common pace of (Qtt) is DC/blue ear power supply Oi:
m) is given.

Since the synchronous detection circuit IIK is set so that the oscillation output and the output of the limiter circuit 21 are inputted in the same phase,
When a 25 MHz burst signal is input, the output during the blue strike period becomes high level. The output of this synchronous detection circuit 28 is input to a detection hold circuit xoK.

Therefore, when the signal of the seven cam signal is input, the detection hall and circuit 5OFi output a high DC voltage, which drives the discrimination output switch circuit 11 and outputs the seven cam judgment output. Obtainable.

On the other hand, when an odd pulse signal is input to the input terminal ff1fK or when there is no signal #'i, no signal is output to the synchronous detection input, so no DC voltage is output from the detection hold circuit 10. Therefore, at this time The output of the determination output switch circuit S1 is a determination output of 4 or no signal.

According to MK Honguchi, who gave an F on the effect of the invention, a crystal filter 21 is used, and crystal is also used in the Ota, Innoexi, and Nlock 1-way 2#. For this reason, the crystal filter's steep filter effect and in-zoexy and in-lotta features extremely strict response performance to frequencies, reducing disturbance.

It is possible to obtain stable switching output that is not affected by noise and does not malfunction. Further, there is no need to increase the time constant in anticipation of slippage and hold, and it is possible to obtain a switching output that is accurate and has a quick response. In addition, a limiting circuit is provided at the input stage of the synchronous detection circuit, and its output can provide a stable and accurate discrimination output regardless of fluctuations in the input level on the first stage side. Furthermore, according to this circuit, the burst signal taken out at the 'Afm period is converted to the fx period using the IHjl line and the synthesizer,
The aim is to obtain more stable in-execution, in-rotation, and error states and synchronous detection.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of a conventional television signal automatic discrimination switching circuit, and Fig. 2 is a configuration diagram of the circuit of Fig. 1. Detection characteristic diagram, Fig. 3 (,) (b) (,) is a signal waveform diagram of each part of the circuit of Fig. 1, Fig. 114 is a configuration explanatory diagram showing an embodiment of the present invention, Fig. 5 is a diagram of Fig. 4 Figure 6 is a circuit diagram showing the synchronous detection circuit of Figure 4. 21...Crystal filter, 24...IH delay line, 2
5...Synthesizer, 27...Limit circuit, 28...
Same a detection mim path, z9... Insocket lock circuit, 10... Detection hold circuit, 31... Discrimination output switch (b) path.

Claims (2)

[Claims] (1) r-) - Reference signals of different frequencies are inputted alternately in the horizontal period, and one of the reference signals of the different frequencies is extracted in the horizontal period. a crystal filter that extracts the reference signal; an injector/reinforcement circuit that receives the reference signal and obtains an oscillation output with the same frequency as this signal; A synchronous detection circuit that obtains synchronous detection during a period in which a signal exists, a hold circuit that holds the output of this synchronous detection circuit, and an output that determines whether or not the reference signal is input according to the output level of this hold circuit. What is claimed is: 1. A switching path for automatically discriminating television signals, comprising: a judgment output switch circuit for obtaining a judgment output switch circuit. (2) The output of the water 47M router passed through one horizontal period by IHjl extension and the direct output from the crystal 74 router are combined, and this composite signal is used as the reference signal. The television signal automatic discrimination switching circuit according to claim 1.