JPS592232B2 - Multi-system color television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for identifying received color television signals in a multi-system color television receiver.

In the SECAM color television system, two color difference signals are FM-modulated and sent line-sequentially at different subcarrier frequencies.

To process this SECAM signal, the carrier color signal is
Delay line to delay horizontal scanning period IH and one horizontal scanning period I
The SECAM switch circuit is operated by a switch signal whose polarity is inverted every H, so that two
The system extracts two color difference signals. Therefore, the above S
The phase of the switch signal that drives the ECAM switch must always match that of the transmitting side. For this reason, SECA
The M color television signal includes identification information that can be used to control the phase of the switch signal. The first identification information is the original line sequential switching signal sent during the 9th line 9H of the vertical retrace period.

The second identification information is a subcarrier frequency signal corresponding to the unmodulated color signal inserted into the backport of the horizontal synchronization pulse. SECA that includes the above two types of line sequential switching information
In a reception processing device that processes an M color television signal, if it is equipped with an identification circuit that uses either the first or second identification information, it is possible to perform correct line sequential switching in the SECAM color television signal; When processing a SECAM color television signal that can be distinguished from other color television signals, such as a PAL color television signal, but has only one of the first and second identification information, the If the signal processing device is equipped with an identification circuit that matches the side, it is a correct SECA.
It is impossible to sequentially switch the M line and distinguish between received signals. In order to solve the above-mentioned problem, two types of identification circuits capable of processing the two types of line-sequential switching information may be used, but this has the drawback that the device is complicated and expensive.

This invention was made in view of the above-mentioned drawbacks, and the SECA
When processing the above two types of line sequential switching information of an M color television signal, two types of separate identification circuits are not required, and the same identification circuit can process only one of the above two types of line sequential switching information. Even if you receive a SECAM color television signal that does not arrive, if you always switch in the correct line sequence, when you receive another color television signal, such as a PAL color television signal that does not receive a SECAM signal, the PAL signal reception status will change. An object of the present invention is to provide a multi-scheme color television receiver capable of switching and receiving data.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a system that can automatically switch and process SECAM and PAL color television signals in accordance with received signals. In FIG. 1, a terminal 101 is a detection output terminal taken out from a video detector (not shown), and a luminance signal is applied to a picture tube 103 through a video amplifier 102.

The output of terminal 101 is also applied to chroma signal separation circuits 201 and 301. The chroma signal separation circuit 201 is composed of a take-off circuit and a bandpass filter.
The L chroma signal is extracted with predetermined band characteristics and output level. The other chroma signal separation circuit 301 is comprised of a take-off circuit, a bell-shaped filter circuit, etc., and is configured to extract the SECAM chroma signal with predetermined band characteristics and output level. Chroma signal separation circuit 20
The PAL chroma signal passed through the switch circuit 4 is supplied to the PAL color television signal processing device 202.
01 switch SWl is connected to the P side and the power supply voltage Vc
This works only if c is provided to the signal processing device 202, and B
-Y demodulation output and RY demodulation output appear. - On the other hand, the SECAM chroma signal passing through another chroma signal separation circuit 301 is supplied to a SECAM color television signal processing device 302.

The signal processing device 302 is constantly supplied with the power supply voltage Vcc, and when the SECAM signal arrives at the terminal 101, a BY demodulation output and an RY demodulation output appear at the terminals 302B and 303R, respectively. A part of the output of the signal processing device 302 is applied to a discrimination device 303 including a SECAM line sequential switching discrimination circuit, a color killer circuit, and a received television system discrimination circuit. The first output signal D1 of the discrimination device 303 is fed back to the SECAM color television signal processing device 302, and the second output signal D2 is connected to the switch circuit 401. 1st
The output signal D, is output from terminal 30 when the SECAM line sequential switching is incorrect and when the SECAM signal is not received.
The second output signal D2 is an output for switching SW1 to SW3 of the switch circuit 401 according to the received signal, and when a SECAM signal is received. In this case, SW1 to SW3 are respectively switched to the P side when a PAL signal is received on the S side.

PALl switched by the switches SW2 and SW3
The demodulated output of either SECAM is applied to a common circuit 501 comprising a color control circuit, a matrix circuit, etc., and the R-Y and B-Y outputs are taken out and applied to the picture tube 103 to obtain a color image. In the configuration shown in FIG. 1, the SECAM color television signal processing device 302 and the discrimination device 303 constitute the main parts of the present invention, so these parts will be explained in more detail below.
In FIG. 2, 1 is an input terminal for a chroma signal a which is obtained through a chroma signal separation circuit 301 that separates a chroma signal from a SECAM color television signal and includes a bell-shaped filter circuit, as shown in FIG. 4a. chroma signal a
are FOB and F of the back porch of the horizontal synchronization signal including the line sequential switching identification signal period FB and FRl, which have different frequencies every 1H of the 9 lines 9H period of the vertical retrace period.

R signal, and color signals DB' and DR.R during the horizontal scanning period.
’. SECAM chroma signal a mentioned above
is applied to a limiter circuit 2, and the output of the limiter circuit 2 is applied to a SECAM line sequential changeover switch 4 which branches into a path passing through a delay line 3 which delays the Taloma signal by 1H and a path not passing through the delay line 3. The SECAM switch 4 is driven by the output of a flip-flop 7 which operates in response to a flyback pulse 6 at its second input terminal 5.
At the two output terminals of the switch 4 and 4R, a signal that passes through the delay line 3 and a signal that does not pass appear alternately every 1H. When the output phase of the flip-flop 7 is correct, the DB' signal appears at the terminal 4B and the DR' signal appears at the terminal 4R temporally continuously. Terminals 4B and 4R are connected to BY demodulator 8 and RY demodulator 9, respectively, and two color difference signals BY and RY appear at terminals 302B and 302R. The output of the limiter circuit 2 is also connected to an FM detector 14.

The FM detector 14 has a tank circuit 15 constituted by a parallel resonant circuit of L and Cl, and has detection characteristics as shown in FIG. That is, the subcarrier frequencies f and F correspond to non-modulation of the FM waves DB' and DR' of the color signal for each scanning line to be inserted into the back porch of the horizontal synchronizing signal. R
The average value of is the center frequency F. It has an S-curve characteristic with a band spanning the frequencies FB and FR of the line sequential switching signal during the vertical retrace period. The PAL color television signal is also shown as a subcarrier frequency of 4.43 M[-1z. The FM detector 14 having the above-mentioned characteristics is
) When the SECAM signal is applied, the output terminal 16 shows the signal shown in Fig. 4b.
Detected output is obtained. That is, F. The detection output VD is positive during the input FR period, and the detection output VD is positive during the FOB and FB periods.
D appears with negative polarity. This output is applied to a phase discriminator 17. The phase discriminator 17 is supplied with the output of the flip-flop 7, and inverts the polarity of the output of the FM detector 14 every 1H, so that the flip-flop 77' and the flip-flop 70 invert the polarity of the output of the FM detector 14 so that the SECAM line sequential changeover switch operates correctly. F as shown in FIG. 4C when the output of F is applied. B, FB and D
The polarity of the period B' is reversed. The output of phase discriminator 17 is applied to sampling circuit 18. terminals 19 and 2
0 is the receiving end of the gate pulse applied to the sampling circuit 18, and the pulse corresponding to the line sequential switching identification signal period to be inserted into the vertical retrace period and the chrominance signal to be inserted into the back porch of the horizontal synchronizing signal, respectively. A gate pulse that matches the period of a carrier wave having a subcarrier frequency corresponding to non-modulation is applied, and the diodes D1 and D2 make each gate pulse an 0R gate, and the two gate pulses are made temporally continuous at the terminal 18a. The pulse shown in FIG. 4d is extracted and applied to the sampling circuit 18.
As shown in FIG. 4f, the output of the sampling circuit 18 is obtained by sampling the output of the phase discriminator 17 only during the period of the gate pulse applied to the terminal 18a. The output f of the sampling circuit is applied to an integrating circuit 21, and integrated by a resistor R and a capacitor C2 over a period from one pulse of the pulse train to at least the next pulse, resulting in a DC output of V as shown in FIG. 4g. appear. This output is compared by comparison circuit 22 with a reference voltage applied to terminals 22a and 22b. Terminals 22K and 221 are output terminals for comparing the integrated voltage V1 with the respective reference voltages K and VI, and are applied to the SECAM line sequential changeover switch 4 and flip-flop 7, respectively. The series of operating waveforms shown in FIG. 4 are shown when a normal SECAM signal is received and the phase of the flip-flop is correct; the outputs of the comparator circuit output terminals 22K and 22 do not appear, and the outputs of the comparator circuit output terminals 22K and 22 do not appear. Therefore, the SECAM line sequential changeover switch and flip-flop are not affected by the comparator circuit in any way. FIG. 5 illustrates a state in which a normal SECAM signal is received and the polarity of the flip-flop is incorrect.

In Figure 5, A and b are respectively FM as in Figure 4.
The input and output waveforms of the SECAM signal of the wave detector 14 are shown. Figure 5c shows S when the phase of the flip-flop is incorrect.
The output waveform of the phase discriminator 17 of the ECAM signal is shown, and the fourth
The phase is reversed from Figure c. Therefore, sampling circuit 1
8, an output with an opposite phase to f in FIG. 4 appears, as shown in f. When this output is applied to the integrating circuit 21, the integrated output becomes a voltage V1, which is smaller than the reference voltages VK and V of the comparing circuit 22. In such a state, the comparison circuit output terminal 22
Since outputs appear on K and 221, SECA
The M line sequential switching circuit 4 and flip-flop 7 are affected. That is, the output of terminal 22K causes SE as shown in Figure 2.
The operation of the CAM line sequential changeover switch 4 stops, and the terminal 4B
No color signal appears in and 4R. In addition, the output from the terminal 22 stops the operation of the flip-flop 7, and the phase discriminator 1
7, an output whose phase relationship matches that of FIG. 5b appears. Therefore, the output of the sampling circuit 18 is as shown in FIG. 5F. As shown in the figure, sampling outputs with different polarities appear every 1H. This output F. becomes a voltage VlO in the integrating circuit 21. Since the reference voltages VI and VK are respectively set so that this integrated voltage satisfies V1 >VlO<VK, an output appears at the terminal 22K, but no output appears at the terminal 221. Therefore, the flip-flop 7 starts operating again and repeats the above-described operation until the output of the phase discriminator appears at the phase shown in FIG. 4c, resulting in a correction of the phase of the flip-flop. Next, a case where a PAL signal is received will be explained.

The PAL color television signal is 9H in Figure 5a.
There is no signal during the period , a burst signal with a constant subcarrier frequency Fp of 4.43 MHz exists during the period FOR, fOB, etc., and a quadrature phase modulated chroma signal corresponds to the period DR', DB'. This is a signal to This Fp has a phase shift of ±45 for each horizontal scanning line, but the above-mentioned FM
When the wave is detected by the wave detector 14, the phase shift of 45 degrees has no effect, and an output according to the detection characteristics shown in FIG. 3 appears. That is, during the burst period, an output with a constant polarity is obtained for each line. When this output is applied to the phase discriminator 17 and passed through the sampling circuit 18, an output F similar to the sampling output that appears when the flip-flop is stopped when receiving the aforementioned SECAM signal is obtained. appears (excluding the vertical retrace period). This output produces an integrated voltage VIO independent of the flip-flop phase. Therefore, as is clear from the above explanation, the output appears only at the terminal 22K. On the other hand, when receiving a black and white broadcast, the signal shown in FIG. 4a or FIG. An output appears at output terminal 22K.

Further, in the receiving state of the SECAM color television signal, in a weak electric field state or in a state in which the color signal component decreases, the integrated voltage of the integrating circuit 21 approaches from V1 to V,O. That is, when V1 exceeds VK, an output appears at the output terminal 22K of the comparator circuit 22. The states in which an output appears at the output terminal 22K of the comparator circuit 22 in this manner are when a PAL color television signal is received, when a monochrome broadcast is received, and when a SECAM color television signal is received in a weak electric field, and the switch circuit 401 in FIG. It can be used as a signal to switch. The above explanation takes as an example a multi-system color television receiver that selectively receives SECAM color television signals and PAL color television signals.
Even if the NTSC system is directly substituted for L, the gist of the present invention does not change at all.

In the embodiment of the present invention, an example has been described in which the PAL color television signal processing device is automatically switched using the output of the comparison circuit included in the SECAM color television signal processing device. The status may be displayed and device switching may be performed manually. As described above, according to the present invention, when identifying whether or not a SECAM color television signal is received in a multi-system color television receiver, the original line sequential switching signal inserted in the vertical retrace period is used. and the received signal is sampled by each pulse of the gate pulse train corresponding to each signal period of the subcarrier frequency signal corresponding to the non-modulation of the chrominance signal inserted into the back porch of the horizontal synchronization signal, and from one pulse to at least the next integrating the sampled signal over a period up to the pulse;
Since the integrated voltage is compared with a reference voltage and a system switching signal is output, the same identification circuit can receive a SECAM system color television signal having only one of the above two types of line sequential switching information. In addition, since it has a signal processing device other than the SECAM system, it has the advantage of being able to receive television signals of other systems as well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a multi-system color television receiver according to the present invention, and FIG. 2 is a block diagram showing the main parts of a SECAM color television signal processing device and a received signal discriminating device, which are the basis of the present invention. Figure 3 is the second
The detection characteristics diagram of the FM detector shown in the figure, Figures 4 and 5 are
It is an explanatory diagram of the operation of the figure. 302 is a SECAM color television signal processing device;
303 is a discrimination device, 202 is a color television signal processing device other than SECAM system, 401 is a switch circuit,
14 and 15 are FM detectors, 17 is a phase discriminator, 18 is a sampling circuit, 21 is an integration circuit, 22 is a comparison circuit, 1
9 and 20 are gate pulse input terminals, and 7 is a flip-flop.

Claims (1)

[Claims] 1 comprising a SECAM color television signal processing device, a non-SECAM color television signal processing device, and a switch circuit for selecting either one of the output signals of the two signal processing devices; The John signal processing device has a center frequency that is the average value of the first subcarrier frequency and the second subcarrier frequency, and has a center frequency that is the average value of the first subcarrier frequency and the second subcarrier frequency. The output phase of the FM detector is determined by a line-sequential switching identification signal having a different polarity every horizontal scanning period. a phase discriminator for discriminating; a first gate pulse train coinciding with a period in which the first and second subcarrier frequencies are inserted; and a first gate pulse train coinciding with a period in which the line sequential switching identification signal is inserted in the vertical retrace period; a sampling circuit that samples the output of the phase discriminator with each pulse of the second gate pulse train, and an integrating circuit that integrates the output of the sampling circuit over a period from one pulse of the pulse train to at least the next pulse; and a comparison circuit that compares the integrated voltage of the integration circuit with a reference voltage and outputs a system switching signal, and the switch circuit receives the output of the comparison circuit and compares the output signals of both signal processing devices. A multi-system color television receiver characterized in that one of the methods is selected.