JPS6316954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an NTSC carrier color signal generation device, and more particularly to a device for generating an NTSC carrier color signal from line-sequential color difference signals.

Prior Art In order to generate a carrier color signal conforming to the NTSC system from a line-sequential color difference signal, it is usually necessary to pass the signal through a device having the configuration as shown in FIG. In the figure, a line-sequential color difference signal obtained by reproducing a recording medium or via another transmission path enters an input terminal 1, and is supplied to switch circuits 2 and 3, respectively. Switch circuits 2 and 3 are alternately opened and closed every horizontal synchronization period (1H) by switching pulses from input terminals 4 and 5, and one of switch circuits 2 and 3 is During the 1H period in the open state, the other switch circuit is in the closed state. As a result, only the first color difference signal (for example, (RY) signal or I signal) is extracted from the switch circuit 2 every 1H period (every 2H period), and the first color difference signal (for example, the (RY) signal or I signal) is extracted from the switch circuit 3 every The second color difference signal ((B-Y) signal or Q signal) is generated every 1H period when the first color difference signal is not extracted.
only is taken out.

The first color difference signal is a 1H delay circuit 6 and an adder 7.
The first color difference signal of the same H period is extracted every 2H period by a circuit consisting of the following, and is supplied to the modulator 8.
Here, the signal is balanced-modulated with a 3.58 MHz carrier wave of a predetermined phase from terminal 9 and then supplied to mixer 10 . On the other hand, the second color difference signal is also connected to the 1H delay circuit 1 in the same manner.
1 and the adder 12 during the 1H period in which the second color difference signal is not taken out from the switch circuit 3.
The previous second color difference signal is replaced and inserted into the modulator 13.
is supplied to A 3.58MHz carrier wave having a phase difference of 90 degrees from the carrier wave entering terminal 9 is supplied to this modulator 13 from a terminal 14, and the 3.58MHz carrier wave is balanced by the second color difference signal from the modulator 13. A modulated wave signal obtained by modulation is extracted.

Both modulated wave signals taken out from the modulators 8 and 13 are band-sharing multiplexed together with a color burst signal in a mixer 10 and outputted to an output terminal 15 as a carrier color signal of the NTSC system.

Problems to be Solved by the Invention However, the above-described conventional carrier color signal generation device includes two switch circuits 2 for separately extracting the first and second color difference signals from the line-sequential color difference signals.
3, two 1H delay circuits 6 and 11, and two modulators 8 and 13, the circuit requires a large number of components and is expensive, and there are many adjustment points, making adjustment work troublesome. Ta.

Therefore, the present invention alternately switches two types of color subcarriers with the same frequency of 3.58 MHz and a phase difference of 90 degrees from each other every 1H period and supplies them to the modulator.
After modulating the line sequential color difference signal with a single modulator
An object of the present invention is to provide a device capable of generating an NTSC carrier color signal.

Means for Solving the Problems The present invention provides a first color difference signal (B-Y) and a second color difference signal (B-Y).
The color difference signals (R-Y) are synthesized alternately in time series every horizontal synchronization period to form a line sequential color difference signal, which is transmitted immediately before the first color difference signal and has a period of two horizontal synchronization periods. Adding circuit means for adding and combining the burst flag pulses with polarity opposite to that of the first color difference signal; a single balanced modulator to which the output signal of the adding circuit means is supplied as a modulation signal; and a color subcarrier frequency of the NTSC system. a carrier wave generation circuit that alternately supplies first and second color subcarriers having the same frequency as the frequency and having phases different from each other by 90 degrees to the balanced modulator every horizontal synchronization period; A first color subcarrier obtained by balanced modulating the first color subcarrier with the burst flag pulse and the first color difference signal.
a delay circuit that delays a time-series composite signal of the modulated wave and a second modulated wave obtained by balanced modulation of a second color subcarrier with the second color difference signal for one horizontal synchronization period, and balanced modulation. The drawbacks of the conventional device are eliminated by comprising a subtracter that subtracts the time-series composite signal taken out from the device and the output signal of the delay circuit, respectively, and outputs the obtained signal as a carrier color signal. An embodiment thereof will be described below with reference to FIGS. 2 to 4.

Embodiment FIG. 2 shows a block system diagram of an embodiment of the apparatus of the present invention. In the figure, a first color difference signal (B-Y) and a second color difference signal (R-Y) are alternately synthesized in time series at the input terminal 16 every horizontal synchronization period (1H). A line-sequential color difference signal is input, a burst flag pulse with a period of 1H is input to the input terminal 17, and a symmetrical rectangular wave with a pulse width of 1H whose phase is synchronized with the horizontal synchronization signal is switched to the input terminal 18. It comes in as a pulse. switch circuit 20
The burst flag pulse shown in FIG. )
and (RY), only the burst flag pulse of the phase immediately before the color difference signal (B-Y) is passed. As a result, the line-sequential color difference signal schematically shown in FIG. 3A that has entered the input terminal 16 and the burst flag pulse with a period of 2H shown in FIG. be synthesized.

Here, in FIGS. 3A and 3D, (B-Y) _i is the color difference signal (B-Y) of the i-th scanning line, and (R-Y) _i is the color difference signal (R- Y), (B-Y) _i+1 indicates the color difference signal (B-Y) of the i+1st scanning line. In the adder circuit 19, the color difference signal (B-Y)
The burst flag pulse shown in FIG. 3C that is added to the position immediately before is added with the opposite polarity to the color difference signal (B-Y). A composite signal of the burst flag pulse and the line-sequential color difference signal extracted from the adder 19 is applied to the balanced modulator 21 as a modulation signal.

The carrier wave supplied to the balanced modulator 21 is generated as follows. The oscillator 22 oscillates and outputs the same frequency as the color subcarrier frequency of 3.58 MHz in the NTSC system, and supplies the output signals to a 90° phase shifter 23 and a switch circuit 24, respectively. The switch circuit 24 receives the second carrier wave taken out from the oscillator 22,
The first carrier wave whose phase is delayed by 90 degrees with respect to the second carrier wave by the 90 degree phase shifter 23 is selectively outputted alternately every 1H and outputted to the balanced modulator 21.

Balanced modulator 21 is supplied with a burst flag pulse followed by a color difference signal (B-Y).
During the 1H period, the first carrier wave is balanced-modulated with these signals and the first modulated wave is output. Here, since the burst flag pulse and the color difference signal (B-Y) are combined with mutually opposite polarities as described above,
The phase of the carrier wave balanced-modulated with the burst flag pulse is shifted by 180° from the phase of the carrier wave balanced-modulated with the color difference signal (B-Y). This means that the modulated wave balanced-modulated with the burst flag pulse is a regular color burst signal of the NTSC system. In addition, the balanced modulator 21
is the 1H period when the color difference signal (R-Y) is supplied,
A second modulated wave obtained by balanced modulating the second carrier wave with the color difference signal (RY) is output. As mentioned above, the second carrier wave has the same frequency as the first carrier wave.
3.58MHz and out of phase with respect to the first carrier.
Since they are advanced by 90 degrees, the color difference signals (B-Y) and (R-Y) are each subjected to quadrature two-phase modulation based on the NTSC system.

In this way, from the balanced modulator 21,
As schematically shown in FIG.
A signal is obtained by time-seriesly synthesizing the modulated waves alternately every 1H. In addition, Figure 3D
In the middle, d ₁ and d ₂ indicate the modulated waves obtained by balanced modulation of the first carrier wave with the burst flag pulse shown in C of the same figure (however, as mentioned above, the phase of the carrier wave is different from that of the first carrier wave). (It is shifted by 180° with respect to the carrier wave.) The time-series composite signal taken out from the balanced modulator 21 is delayed by 1H in a 1H delay circuit 25 and then supplied to a subtracter 26, while being directly supplied to the subtracter 26 without being delayed. Subtractor 26
is 1H from the output time series composite signal of the balanced modulator 21
After subtracting the output delay signal of the delay circuit 25, the signal shown in FIG. 3E is outputted to the output terminal 27.

Here, as is well known, the color subcarrier frequency of 3.58MHz in the NTSC system is equal to the horizontal scanning frequency of 15.734kHz.
227.5 times, and for fractions of 0.5 the color subcarrier is
At the beginning and end of 1H, the phase is 0.5 period, i.e.
They are 180° different. Therefore, since the time-series composite signal supplied to the 1H delay circuit 25 is a modulated wave obtained by modulating a 3.58MHz carrier wave, the input and output of the 1H delay circuit 25 are out of phase by 180 degrees with respect to each other. It becomes different. However, the output modulated wave of the 1H delay circuit 25 is transmitted to the balanced modulator 2 in the subtracter 26.
Since it is subtracted from the output modulated wave of 1H delay circuit 25, it ends up being in phase with the input modulated wave of the 1H delay circuit 25 and balanced modulator 2.
It is added and combined with the output modulated wave of 1.

That is, _in the output signal of the subtracter 26 shown in _FIG .
Y) _i-1 is the composite signal with the 1H delayed modulated wave obtained by balanced modulation of the second carrier wave, and _e2 is the color difference signal (B
_-Y ) A composite signal of the 1H delayed modulated wave obtained by balanced modulation of the first carrier wave with i and the modulated wave obtained by balanced modulation of the second carrier wave with color difference signal (R-Y) _i . Furthermore, e ₃ is a composite signal of a modulated wave with (B-Y) _i+1 as a modulation signal and a 1H delayed modulated wave with (R-Y) _i as a modulation signal, and these Combined signal e ₁ ,
The phase of the carrier wave of the modulated wave constituting e ₂ and e ₃ is both relative to the phase of the carrier wave of the modulated wave (this is expressed as ∠0°) with the modulating signal as (B-Y). Therefore, the different phase of the carrier wave of the modulated wave whose modulation signal is (RY) is ∠90°, which complies with the NTSC system.

Further, the phase of the carrier wave of the modulated wave using the burst flag pulse as the modulation signal is ∠180°, and is outputted to the output terminal 27 as a color burst signal repeatedly twice. Therefore, from the output terminal 27, the two color difference signals are quadrature two-phase modulated and output as NTSC.
A carrier color signal (including a color burst signal) conforming to the system is extracted.

FIG. 4 shows a circuit diagram of an embodiment of the main part of the device of the present invention. In the figure, the same components as in FIG. 2 are given the same numbers. In Figure 4, input terminal 2
The time-series composite signal from the balanced modulator 21 that enters the NPN transistor Q1 is applied to the base of the NPN transistor _Q1 . The transistor _Q1 constitutes an emitter follower, and outputs the input time series composite signal from its emitter to the 1H delay circuit 25 via the capacitor _C1 , while also outputting the input time series composite signal to the 1H delay circuit 25 via the resistor _R1 and capacitor _C2 in series. Output to 26.

The 1H delay circuit 25 is composed of a 1H delay line 30, a resistor R ₂ and a coil L ₁ connected to its input side, and a variable inductance element L ₂ and a variable resistor VR connected to its output side. , the input time series composite signal is delayed by 1H and the delayed signal is applied to the base of transistor _Q3 via capacitor _C4 . Here, the above input time series composite signal is
Since it is a modulated wave with a carrier wave of 3.58MHz,
As the 1H delay line 30, a delay line made of glass, which is the most common and inexpensive medium, can be used.

On the other hand, the subtracter 26 includes NPN transistors Q ₂ ,
Q ₃ , base bias resistance R ₃ of transistor Q ₂ ,
R ₄ , R ₅ , base bias resistance of transistor Q ₃ R ₉ , R ₁₀ , emitter resistance of transistor Q ₂ , Q ₃
R ₆ , R ₁₀ , a resistor R ₇ and a capacitor C ₃ connected in series between the emitters of transistors Q ₂ and Q ₃ ,
It consists of the collector load resistor _R11 of transistor _Q3 , etc.

The time-series composite signal taken out from the balanced modulator 21 is impedance-converted and taken out from the emitter of the transistor _Q2 constituting the emitter follower, and then sent to a circuit consisting of resistors _R6 , _R7 , _R8 and a capacitor _C3. to the emitter of transistor _Q3 . On the other hand, transistor Q ₃
The time-series composite signal delayed by 1H is supplied to the base of . As a result, a signal obtained by subtracting the base input signal from the input signal of the emitter of the transistor _Q3 is extracted from the collector of the transistor _Q3 as a carrier color signal.

Effects As described above, according to the present invention, the burst flag pulse is inserted at a position immediately before the color difference signal (B-Y) in the line-sequential color difference signal with a predetermined polarity, and then balanced modulation is performed. The number of balanced modulators and the number of 1H delay circuits can be halved compared to the previous model, and the number of parts can be reduced, making it simple and inexpensive to configure.Also, since there are fewer adjustment points, it is easier to make adjustments than conventional equipment. The required time can be shortened, and since the input signal of the 1H delay circuit has the same frequency as the color subcarrier of the NTSC system, it is possible to use a commercially available, inexpensive delay line with a glass medium. It is something that you have.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of a conventional device, Fig. 2 is a block system diagram showing an embodiment of the device of the present invention, and Figs. The figure shown in FIG. 4 is a circuit diagram showing an embodiment of the main part of the device of the present invention. 1, 16...Line sequential color difference signal input terminal, 2,
3, 20, 24...Switch circuit, 4, 5, 18
...Switching pulse input terminal, 6, 11, 2
5...1H delay circuit, 7, 12, 19...adder,
15, 27... Carrier color signal output terminal, 17... Burst flag pulse input terminal, 21... Balanced modulator, 22... Oscillator, 23... 90° phase shifter, 26
...Subtractor, 30...1H delay line.

Claims (1)

[Claims] 1 The first color difference signal (B-Y) and the second color difference signal (R-Y) are synthesized alternately and in time series for each horizontal synchronization period to form a line-sequential color difference signal. Adding circuit means for adding and synthesizing burst flag pulses transmitted immediately before the color difference signal and having a period of two horizontal synchronization periods with a polarity opposite to that of the first color difference signal;
a single balanced modulator to which the output signal of the summing circuit means is supplied as a modulating signal;
a carrier generation circuit that alternately supplies first and second color subcarriers that differ by 90 degrees to the balanced modulator every horizontal synchronization period; A first modulated wave obtained by balanced modulation of the first color subcarrier with a color difference signal, and a second modulated wave obtained by balanced modulation of the second color subcarrier with the second color difference signal. A delay circuit that delays the time-series composite signal of the wave by one horizontal synchronization period, and a signal obtained by subtracting the time-series composite signal taken out from the balanced modulator and the output signal of the delay circuit, respectively, is used as a carrier color. An NTSC carrier color signal generation device characterized by comprising a subtracter that outputs as a signal.