JPS62136189A - Secam chrominance signal reproducing device - Google Patents

Abstract

PURPOSE:To stabilize a color reproducing output at a fixed level, by inserting a fixed DC voltage by switching a current which is determined by a constant current during a blanking period and producing an inserting DC voltage at a constant-current source by making non-modulated parts match to the inserted fixed DC voltage. CONSTITUTION:When a transistor 24 is turned on in a blanking period, during which the transistor 24 is turned on, transistors 20 and 21 are cut off and transistors 22 and 23 are turned on. Then the current I1 of a constant-current source 31 is made to flow to transistors 25 and 26 through the transistor 22. In addition, the current I2 of another constant-current source 32 is made to flow to the transistors 25 and 26 through the transistor 23. Therefore, the inserted DC voltage V3 goes to V3=VCC-R7.(I1+I2)/2 at a load resistance 7 which is an R-T output and the inserted DC voltage V4 becomes V4=VCC-R 8.(I1+I2)/2 at another load resistance 8 which is a B-Y output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an SE camera used in a color television receiver capable of receiving SECAM color television signals.
Related to CAM color signal reproducing device 0 Conventional technology In recent years, the color television color signal transmitted by the SECAM system is demodulated in line-sequential form, the subcarrier oscillator output is modulated, and then the PAL signal is regenerated. A method of reproducing color signals using a demodulator has come into use.

First, this SECAM color signal reproducing system will be briefly explained using FIG. 5, and then the configuration of a conventional example will be explained.

As shown in FIG. 5, the SECAM composite video signal is first input to a bell filter 51, then amplitude-limited by a limiter amplifier 52, and color-demodulated in line-sequential form by a SECAM demodulator 63. At the same time, the blanking period is DC voltage is inserted into. Next, the color demodulated signal is guided to the R-Y clan 1 circuit 64 and the B-Y clamp circuit 55, and when the color signal is the R-Y line, the R-Y clamp circuit 54,
Also, when the color signal is B-Y Li/, the B-Y clamp circuit 5
5, the DC is clamped and the DC is regenerated. Thereafter, the line sequential signal is led to a line sequential signal extraction circuit 56, and the DC-regenerated line sequential signal is extracted.

This line sequential signal is then directed to a modulator 57 which modulates the output from the PAL subcarrier oscillator, which output is ACC
After being guided to the amplifier 58, one of the signals passes directly and the other passes through a one-line delay line 59 and is then guided to the switch 6o. This switch 60 functions to extract continuous signals of RY and BY from the line sequential signal.

The output of the switch 60 is connected to the PAL A-RY demodulator 61 and P
The continuous R-
This becomes the demodulated output of Y and BY.

The above is the SECAM color signal reproduction method described here.

The present invention relates to the SECAM demodulation and DC insertion part described above.

Hereinafter, with reference to FIG. 6, conventional SECAM demodulation,
An example of the DC insertion section will be explained.

First, the part A surrounded by a broken line in FIG. 6 is an FM detector for reproducing SECAM color signals, and is a quadrature detector. First, this quadrature detector will be briefly explained. 5, 6, 9. 10. 11 is resistance, 12, 1
3,14115116.17, 18, 19 are NPN) transistors, 27+28.29 is a capacitor, 3o is a coil, and 33 and 34 are constant voltage sources. In the quadrature detector configured in this way, the seventh terminal is connected to the terminal and
As shown in the figure, FM modulated subcarriers with opposite phases are input, and at the same time, they are input to the pace of transistor 1B919, and at the same time, they are phase shifted by capacitor 29, coil 3o, and resistor 9 via capacitors 27 and 28. , the base of transistor 139140 and the base of transistor 12115 through emitter follower transistor 16, respectively.
input to the base of transistor 18 + 19
+12.13 and 14.15 constitute a multiplier, and an FM-detected line-sequential signal appears at the output of the load resistor 8.7. The RY demodulated waveform appears on the load resistor 7 when the line is RY, and the inverted BY demodulated waveform appears when the line is the BY line. In addition, the B-Y demodulated waveform appears on the load resistor 8 when the B-Y line is present, and the R-Y
When it is a line, an inverted RY demodulated waveform appears.

Next, DC insertion during the blanking period will be explained.

In Figure 6, 1.2, 3, 4, 7° 8.37.38
is resistance, 21.22.24, 39.40.4-1.42
．． 43144 is an NPN) transistor, 31 is a constant current source,
35.36 is a constant voltage source.

As shown in FIG. 8, a signal that is at a high level only during the blanking period is input from terminal 0. Therefore, the transistor 24 is cut off during periods other than the blanking period. Therefore, outside the blanking period, the base potential of the transistor 21, which is determined by the division ratio of the resistor 3 and the resistor 40, is set by the constant voltage source 3.
When the voltage is set higher than the potential of the transistor 6, the transistor 21 is turned on, the transistor 22 is turned off, and the output of the quadrature detector A appears at the load resistor 7 and the load resistor 8. on the other hand,
Since the transistor 24 is turned on during the blanking period, by appropriately selecting the resistance value of 2.3t4, the base potential of the transistor 21 can be made lower than the potential of the constant voltage source 36, which is the base potential of the transistor 22. As a result, the transistor 21 can be turned off and the transistor 22 can be turned on. At this time, as shown in FIG. 8, the waveform of the terminal ◎ connected to the bases of the transistors 41 and 44 is on the B-Y line when the transistor 4
1.44 is a signal that turns on, and the waveform of terminal [F] is a signal that turns on transistors 42 and 43 when it is on the RY line.

Also, the current DQ39) flowing through the transistor 39 and the current flowing through the transistor 40 (IQ4o) are
．． 38 are R37 and R38, respectively, and the current of the current source 31 is 11. Here, the voltage of the constant voltage source 33 is vCC, and the resistors 7 and 8
Assuming that the values of are R7 and Rs, respectively, transistors 42 and 43 are turned on when the R-Y line is on, so the potential (vl) of the load resistor 7 is v1 = vCC - (R7 x engineering Q39)
......(3) When the line is B-Y, the transistors 41 and 44 are turned on, so the potential (v2) of the load resistor 7 is v2=vCC-(R7×IQ4o)...・
......(4).

Therefore, by adjusting the resistor 9 and the coil 3Q, as shown in FIG.
-Y's unmodulated Kya! Make sure that the demodulated output of J 74.406MH2 matches, and insert voltage v2 at B-Y line.
and the demodulated output of BY's unmodulated carrier 4.25MH2 are made to match. If this is not done, the unmodulated achromatic portion will be colored.

As described above, when a color bar signal is demodulated using the so-called figure-eight curve showing the SECAM-FM detection characteristics shown in FIG. 9, the result is as shown in FIG. 10.

At this time, the R-Y demodulated output is outputted with positive polarity, and the pB-Y demodulated output is outputted with negative polarity. In the B-Y output on the load resistor 8 side, the B-Y demodulated output has positive polarity and the R-Y demodulated output has negative polarity, contrary to the above.

Now, by matching the demodulated output of the non-modulated carrier to the DC voltage inserted in this way, and further clamping the inserted DC voltage portion, DC reproduction of the color demodulated output can be achieved. This reproduced color signal is guided to a modulator 57 shown in FIG.

Problems to be Solved by the Invention However, in the conventional configuration as described above, in order to match the demodulated output of the unmodulated carrier to the inserted DC voltage, color variations may occur due to variations in the resistance values of the resistors 37 and 38 in FIG. There was a problem in that the playback output level varied widely.

Now, considering the RY output (output of load resistor 7 in Figure 6), the RY reproduction output level ■v2-vl (see Figure 9) (
11: current flowing through the 31 current source), and R38=1. When it is lR37,
If Rsa is pressed 1 inch smaller, the R-Y playback output level will be 1.
0.5%, and the color reproduction output 9 level guided to the modulator 57 changes greatly due to variations in R37 and Rsa, which has the disadvantage of being impractical.

In view of the above-mentioned problems, the present invention provides S
The object of the present invention is to provide an ECAM color signal reproducing device.

Means for Solving the Problems In order to achieve the above object, the SECAM chrominance signal reproducing device of the present invention includes a first FM detector whose collector is connected to the first output terminal of an FM detector for reproducing SECAM chrominance signals. transistor and the second FM detector for reproducing the SECAM color signal.
a second transistor whose collector is connected to the output terminal of the first transistor, a first constant voltage source commonly connected to each of the first and second transistors, and each of the first and second transistors. a third and fourth transistors commonly connected to the emitters; a second constant voltage source commonly connected to the bases of the third and fourth transistors; and a third transistor whose emitters are connected to each other. A sixth transistor was connected, and its collector was connected as a constant current source for the FM detector differential amplifier, and its emitter was connected to the emitter of the fourth transistor, and its collector was connected to a third constant voltage source. a first constant current source commonly connected to the sixth transistor, each emitter of the third and fifth transistors, and a second constant current source commonly connected to each emitter of the fourth and sixth transistors; The fifth and sixth transistors are connected in common to the respective bases of the sixth and sixth transistors, and are configured to include a current source and means for cutting off the fifth and sixth transistors only during the blanking period.

Effect: According to this configuration, the third and fourth transistors are turned on during the blanking period. Therefore, the current of the first constant current source (I2) flows through the third transistor, the current of the second constant current source (I2) flows through the fourth transistor, and both of them flow through the third and fourth transistors. 4 transistor collectors, and the sum of 172 power; flows through the first and second transistors to the load resistors for the outputs of R-Y and B-Y, and (load resistor) X (11
+I2)/2 DC voltage is inserted. The magnitude of this inserted DC voltage is determined by the current value of the constant current source, and is sufficiently stable. That is, if the resistance ratio varies by one factor as in the conventional example described above, the color reproduction output will vary by 10.
A constant DC voltage is often inserted, and the non-modulated portion is matched to this inserted DC voltage, so that a color reproduction signal of a constant level can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows SECA in one embodiment of the present invention.
This shows the main parts of the M color signal reproducing device, and FIG. 2 shows its overall configuration. Common parts in Figures 1 and 2 are given the same numbers, and here
This will be explained with a diagram.

Also, the parts having the same configuration as those of the conventional example shown in FIG. 6 are given the same reference numerals, and the explanation thereof will be omitted.

In Figure 2, A is an FM detector for reproducing SECAM color signals, 1.2, 3, 4,798 are resistors, and 20.2112
2, 23, 24125126 is NPN) transistor, 3
1.32 is a constant current source, and 33 and 35.36 are constant voltage sources. The FM detector A for reproducing SECAM color signals is as described in the conventional example.

Next, as shown in FIG. 80, the base of the transistor 24 is input with a signal that is at a high level only during the blanking period, so that the transistor 24 is cut off at a certain portion of the video signal. each transistor 20.2
1 turns on. Here, a current from a constant current source 31 flows through the transistor 21, and a current from a constant current source 32 flows through the transistor 2o, but this current flows from a constant voltage source 33 (VCC). . Therefore, the operation of the FM detector is the same as in the conventional example.

Next, a blanking period in which the transistor 24 is turned on will be explained. When transistor 24 is turned on, transistors 20 and 21 are cut off and transistors 22 and 23 are turned on, as explained in the conventional example. Then, the current generator 1 of the constant current source 31 becomes the transistor 22.
through to transistors 25 and 26. Further, current 2 from the constant current source 32 flows through the transistor 23 to the transistors 25 and 26. Therefore, at the load resistor 7 which is the R-Y output, the DC voltage inserted is V3 = VCC-R7・(11+I2)/2, and B
- For the load resistor 8 which is the Y output, the inserted DC voltage is v4 = VCC-Re, (11-1-I2)/2
becomes.

At this time, by adjusting the coil 30 and the resistor 9, the center frequency of the S curve characteristic of the FM detector (color reproduction output of the video part and output when no subcarrier is input) can be the same frequency) is 4-328
MHz (4-25MHz +4.4C) 6mm/2)
By doing so, on the R-Y output side, the insertion DC voltage source can be aligned with the detection output at the unmodulated frequency of 4.406MH2 of R-Y, and on the B-Y output side, the insertion DC voltage v
4 and the detection output when the unmodulated frequency of B-Y is 4.25 oMH2 can be made the same.

As a result, the waveform of the R-Y output when the color par signal is demodulated and the B-Y waveform when the color par signal is demodulated become as shown in FIG.

The waveform shown in FIG. 4 is as shown in FIG.
For the Y line, the waveform on the load resistor T side, which is the RY output, is used, and for the BY line, the waveform on the load resistor 8 side, which is the BY output, is used. Then, both include the inserted DC voltage part and the unmodulated frequency (RY is 4.
If the output levels of 40e MH2 and B-Y (4.25MH2) match and the inserted DC voltage portion is clamped, DC regeneration can be performed for both.

Effects of the Invention As described above, according to the present invention, the current is switched between the blanking period and the video signal portion, a constant DC voltage is inserted during the blanking period, and R- is applied to the inserted DC voltage portion. By combining the demodulated outputs of the unmodulated subcarriers, which are the achromatic parts of Y and B-Y, and clamping the inserted DC voltage part, DC reproduction becomes possible.

Moreover, in the present invention, a constant DC voltage is inserted by switching the current determined by a constant current during the blanking period, and the non-modulated part is matched to the inserted DC voltage, so the inserted DC voltage is generated by a constant current source. By doing so, the level can be made extremely stable, and as a result, the color reproduction output can also be stabilized at a constant level, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the main parts of a SECAM color signal reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram of the entire device, and FIG. 3 is a frequency vs. demodulation diagram showing the S-curve characteristics of the device. Output voltage level characteristic diagram, Figure 4 is a waveform diagram when a color par signal is reproduced with the same device, Figure 6 is a SECAM-
A block diagram of the PAL conversion demodulation system, Fig. 6 is a circuit diagram of a conventional SECA1wi color signal reproducing device, Fig. 7 is a waveform diagram of the terminals shown in Figs. 2 and 6, and Fig. 8 is a waveform diagram at ■. The waveform diagram at terminal C10, ■ in Figure 6, and the waveform diagram at terminal C10,
FIG. 10, a characteristic diagram showing the curve characteristics, is a waveform diagram when a color par signal is reproduced by the same device. 1.21394 * 7 + 8...Resistance, 2
0,21.22.23.24.25126...
NPN) transistor, 31.32...constant current source, 33,35.36...constant voltage source. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure A Figure 4 R-Y 5-in 13-'I' 2-in Figure 7 Figure 8 Figure 9 Figure 10 R-Y (λ resistance 7) η2/(-out 7I&S

Claims (1)

[Claims] A first transistor having a collector connected to a first output terminal of an FM detector for reproducing SECAM color signals constituted by a differential amplifier, and a collector connected to a second output terminal of the FM detector. a second transistor, a first constant voltage source commonly connected to each base of the first and second transistors, and a third constant voltage source commonly connected to each emitter of the first and second transistors. and a fourth transistor, a second constant voltage source commonly connected to each base of the third and fourth transistors, the emitter of which is connected to the emitter of the third transistor, and the collector of which is connected to the emitter of the third transistor. a fifth transistor connected as a constant current source of the differential amplifier of the FM detector, and a sixth transistor whose emitter is connected to the emitter of the fourth transistor and whose collector is connected to a third constant voltage source. a first constant current source commonly connected to each emitter of the third and fifth transistors, and a second constant current source commonly connected to each emitter of the fourth and sixth transistors. a current source; and a switching means that is commonly connected to each base of the fifth and sixth transistors and cuts off the fifth and sixth transistors only during the blanking period, A SECAM color signal reproducing device characterized in that a constant stable DC voltage is inserted during a blanking period to obtain a color reproduction output at a constant level.