JPH02113781A - Muse system discriminating circuit - Google Patents

Abstract

PURPOSE:To discriminate whether the signal system of a video signal is a MUSE system or not by detecting the subcarrier of a MUSE signal. CONSTITUTION:The video signal received by an antenna 1 is low-pass-converted by a converter 2, thereafter, converted to an intermediate frequency signal by a frequency converting circuit 3, demodulated by an FM demodulator 4 and conducted to a switching means 5 and a MUSE system discriminating circuit 6. Here, the video signal is inputted to a band-pass filter 11, and the frequency components of 5.7MHz are outputted from the band-pass filter 11. When the signal is the signal in the MUSE system, the subcarrier is successively outputted, a carrier detecting circuit 12 outputs an H signal, and when the signal is the signal in an NTSC system, the carrier detecting circuit 12 outputs an L signal. Thus, whether the received video signal is in the MUSE system or not can be discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a MUSE system determination circuit that determines whether the signal system of a video signal is the MUSE system.

[Summary of the Invention] The first invention is capable of determining whether or not the MUSE system is used by detecting subcarriers of the MUSE signal.

The second invention is capable of determining whether or not the MUSE system is used, by changing the number of frame synchronization pulses.

In the third invention, it is possible to determine whether or not the MUSE method is used, depending on whether the keyed AFC circuit outputs a keyed AFC pulse.

[Prior Art and Problems to be Solved by the Invention] Current satellite broadcasting is based on the NTSC system, but in a few years, broadcasting using the MIJSE system will begin. At the beginning of broadcasting, there were few MUSE system software, so MUSE system and N
It will be broadcast in both T'SC and T'SC formats. Therefore,
A receiving device that can receive both types is required. But 1,
The NTS C system is f)+-"I5, 75KI
lz, f5, = 59, 7 t-1z and scanning line 525
It is a book, and the M LJ S E method is fo-3], 5KH
Since there are 1125 scanning lines for z, fs, and 60 I-I z, it is necessary to determine whether the received signal is of the M LJ SE system.

Therefore, an object of the present invention is to provide a MUS+ε system discriminating circuit that determines whether or not television broadcasting is based on the MUSE system.

[Means for Solving the Problems] A MUSE method discriminating circuit according to the first invention for achieving object L includes a filter that passes a subcarrier band of the MUSE method, and a filter that continuously outputs subcarriers. It consists of a carrier detection circuit and a carrier detection circuit that detects whether the

The MUSE method discrimination circuit according to the second invention includes a pulse detection circuit that detects one pulse per frame, and a pulse detection circuit that counts the number of one pulse per frame detected by this detection circuit. It has seven counters, and it is determined whether the MtJ SE method is used or not based on the count number of this counter.

According to the third invention, the key 1 outputs the geared AFC pulse at the timing when the signal is input. ” It has an AFC circuit, and from the output of this key F'AFC circuit, the MU
This is the part of Party B that determines whether or not it is an SE method.

"Operation" According to the first invention, the demodulated video signal is input to the filter, and if it is a MUSE system signal, the subcarriers are continuously output from the filter.
If the signal is a signal other than the MUSE system, the subcarrier frequency components will not be continuously output from the filter, and by detecting this with the carrier detection circuit, it can be determined whether or not the MUSE system is used.

According to the second invention, the pulse detection circuit Caffreno detects synchronization pulses from the video signal, and the counter detects the number of frame synchronization pulses. MLJ
You can tell whether it is an SI deer type or not.

According to the third invention, when a video signal is input to the keyed AFC circuit, if it is a MUSE method, it outputs a keyed AF'0 pulse, and if it is not a MUSE method, it does not output a keyed AFC pulse. MUSE method or not?'
I can separate from l'JI.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, to explain the outline of the MUSE method, fn (horizontal scanning frequency) = 31, 5 K, Hz, f
v (vertical scanning frequency) = 601-iz, the number of scanning lines is 1125, and 5.7272MF (z subcarriers are used.The horizontal synchronization signal is placed at the beginning of each line, and the frame The synchronization signal uses two lines and consists of 17 pulses with a 4-transmission lock width on the - line and 18 on the other lines, and a clamp reference signal is inserted at a specific position on a specific line. There is.

FIG. 1 shows a partial circuit block diagram of a receiving device to which the present invention is applied.

In FIG. 1, an antenna 1 receives a video signal and sends the received video signal to a converter 2. The converter 2 performs low-frequency conversion of the video signal, and the low-frequency converted video signal is guided to the frequency conversion circuit 3 via an amplifier (not shown). The frequency conversion circuit WPi3 consists of a mixer and a VCO (voltage controlled oscillator), and mixes the video signal with a local oscillation signal to convert it into an intermediate frequency signal. The output of frequency conversion circuit 3 is FM
The signal is sent to a demodulator 4, and the FM demodulator 4 demodulates the intermediate frequency signal. This demodulated video signal is led to the selection terminal a of the switching means 5 and the MUSE system discrimination circuit 6, respectively. The - selected terminal of the switching means 5 is MU.
In the SE signal processing circuit 7, the other selected terminal C is NTS.
The switching means 5 selectively sends the demodulated video signal to either the MUSE signal processing circuit 7 or the N'I'SC signal processing circuit 8. Supplied to 4-ru.

M1. J S E ) j style? The lj separate circuit 6 determines whether the manually input video signal is in the Ni t, J s iε format, so if it is in the MUSE format, is it f-? For other methods, a signal of 1 degree is output to each microcomputer 9. The meinon 9 is configured to control the switching position of the switching means 5 in a convex manner. M+, JS
When the 11 signal is output from the E system discrimination circuit 6, a switching control signal is output to switch to the - selected terminal l] side, and the L signal is output from the M'U S E system 1' JI separate circuit 6. Then, the other selected terminal C side? A switching control signal is output to switch this.

FIG. 2 shows a first example of a specific configuration of the MUSE method discriminating circuit 6. As shown in FIG. In Figure 2, the demodulated video signal is filtered by a bandpass filter (
BPF)l Guided by I. This band-pass filter 11 has a frequency band in the vicinity of 5,7 M I-1z as its pass band, and the band-pass filter 7
The output of 7 is supplied to the carrier detection circuit 12, and the key/rear detection circuit 12 determines whether or not the output of the band pass filter 11, that is, the carrier of 5.7 MIIz is continuously detected L7. .5.7If the gear of Ml1z is continuously detected 4', the signal I(signal 1) is output.

In Fig. 3 (J, [11j M IJ S I!; method discrimination oki] the second example of route 6 is shown. In Fig. 3)
Then, the decoded video signal is guided to the pulse detection circuit 13 or 21.

This pulse detection circuit 13 detects a frame synchronization pulse with a width of 4 transmissions.
Output υ1 pulse to counter 14 1, counter 1
4t until the first counter section 14a and the second counter section +4
b, and both counter parts 14a, I
4 bi,: The output of the pulse detection circuit I3 is led. When the first counter section 14a counts 17 1-nome synchronization pulses, it outputs an on signal for 1 line (1 line).
t■) Output to timer 15. When the I-line timer 15 inputs the on signal, the transmission time for one line (I'
Outputs the drive signal to the second counter section +4b.
The counter unit 141] counts the frame synchronization pulses from the pulse detection circuit 13 for the period in which this drive signal is output, and when the count is 5.17, outputs it to the ■■ double signal microcomputer 1.0. Otherwise, the I7 signal is output.

In FIG. 1, I) η MUSE method discrimination circuit 6
A third example is shown. In FIG. 4, the demodulated video signal is supplied to the GyF'A FC circuit I6. This gear F' AFC circuit 16 detects the frame same 1υ1 pulse and the horizontal synchronizing pulse, applies phase synchronization with this pulse, and outputs the gear AFC pulse ([(signal)) at the timing when the clamp W quasi-signal is input. , is configured to also guide this keyed AFC pulse to the microcomputer IO.

The operation of the above configuration will be explained below.

The video signal received by the antenna 1 is low-frequency converted by the converter 2, and then converted to an intermediate frequency signal by the frequency conversion circuit 39.The video signal converted to the intermediate frequency signal is
The demodulated signal is demodulated by the M demodulator 4, and the signal is sent to the I-ding means 5 and the M
The signal is guided to the IJSE method discrimination circuit 6.

Here, when the M+, JSE method discriminating circuit 6 is in the first example shown in FIG.
, 7 M I-i Z 17S wavenumber components are output. If it is a signal of the M [, J S E type, the sub gear rear of 57 mm 4 H2 is on board, so the sub gear rear is continuously output and the carrier detection circuit 12 outputs ■ [signal 4]. Also, if it is an NTS C type signal, it is 5.7MII
The gear rear detection circuit 12 outputs the 7 signal without continuously outputting the frequency component of z.

In the case of the second example shown in FIG. 3, the video signal is input to the pulse detection circuit 13. Freno outputs the same 1υ1 pulse and the first ('X
'I counter section ivy a counts the number 4-.

When it reaches 17, the first counter part 14a
outputs an on signal, and the I-line timer 15 outputs a drive signal to the second counter section 14)). Then, the frame synchronization pulse of the next line is counted by the second counting section 14b, and an 11 signal is outputted. In addition, if it is an N'rS C type signal, 4 transmissions will be required [because many knock width pulses are not on one line, the second
The counter section 14bi outputs only the LL signal.

Furthermore, when the MUSE system discrimination circuit 6 is the third example shown in FIG.
is input. If the video signal is MUSE type, Ghee F'
The A FC circuit I6 is the key A Fc which is the I-1 signal.
Output circuit I6. Further, in the case of the NTS C type, the keyed AFC circuit 16 does not output a keyed AFC signal, and therefore outputs only the I7 signal.

In this way, the MUSE system discriminating circuit 6 of the first to third examples determines the H signal if the video signal is the MUSE system.
If it is the N'T'SC type, the I7 signal is output to the microcomputer 10, respectively. If it is an I-1 signal, the microcomputer IO switches the switching means 5 to the - selected terminal side, and the video signal output from the FM demodulator 4 is sent to the MLJ SE signal processing circuit 7. Also, if the microcomputer 10 is an I signal, it switches the switching means 5 to another selected terminal C side, and outputs the video signal from the demodulator 4 to the output signal N'r.
Send to the SC signal processing circuit 8.

[Effects of the Invention As mentioned above, according to the first invention, MUS
According to the second aspect of the present invention, the subcarrier of the M tJ S E type signal is counted. Therefore, according to the third invention, the keyed A FC circuit is
Since it is configured to detect whether the pulse is output or not,
Each of them has the effect of being able to determine whether the received video signal is Rikishima/fLlsE type or not.

[Brief explanation of drawings]

1 to 1 show an embodiment of the present invention, FIG. 1 is a partial circuit block diagram of the receiving device, and FIG.
A block diagram showing a first example of the S Iε method discriminating circuit, and FIG. 3 are block diagrams showing a second example of the M U S Iε method discriminating circuit. It is a block diagram showing a third example of a separate circuit. 6. MUSE system discrimination circuit, II. Band pass filter (filter), 12 carrier detection circuit, 13
Pulse detection circuit, 14 counter, 16 keyed AF
C circuit. Figure 2 Figure 4 Figure 4b Block diagram of MUSE Ga 2 Shun, 8be Road (2nd example) Figure 3

Claims (3)

[Claims] (1) A MUSE method discrimination circuit comprising a filter that passes a MUSE method subcarrier band and a carrier detection circuit that detects whether or not this filter continuously outputs subcarriers. (2) It has a pulse detection circuit that detects frame synchronization pulses and a counter that counts the number of frame synchronization pulses detected by this detection circuit, and determines whether or not the MUSE method is used based on the count number of this counter. Characteristic MUSE method discrimination circuit. (3) It has a keyed AFC circuit that applies phase synchronization using frame synchronization pulses and horizontal synchronization pulses and outputs keyed AFC pulses at the timing when the clamp reference signal is input.The output of this keyed AFC circuit determines whether or not the MUSE method is used. A MUSE method discriminating circuit characterized by discriminating.