JPS6187492A - Quiescent-carrier modulation method of chromaticity signal and color carrier modulator device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a carrier suppression modulated chrominance signal using a modulator device which is supplied with a carrier signal to be modulated and a color information signal to be modulated. It is about the method.

In a generally known modulator that performs carrier suppression modulation, for example in a PAL encoder, it is necessary to generate a final chromaticity signal from color difference signals U and V and a color carrier wave, and a luminance signal is added to this chromaticity signal. Added. Another field of application of this modulator is the field of generating test line signals, and these test line signals are also formed from a luminance signal component and a chromaticity signal superimposed thereon (20T pulse delay method). )0 Both of these applications require high stability over time for the modulation process. It is of primary importance that the carrier wave is reliably suppressed at the output of the modulator for each signal level of the U and V (envelope) that produces a colorless 1' pixel.

Defective carrier suppression can either cause a color cast in the colorless image portions or cause color errors in the colored image portions. In the case of test line signal generators, such instabilities or carrier residues result in unacceptable distortions of the measurement signal, thus making accurate measurements impossible.

According to the prior art, the color carrier modulator can be configured as an analog ring modulator (a double-sideband modulator with carrier suppression). In this case, significant effort and expense is required to obtain the desired symmetry and temperature compensation to achieve the required level of stability and carrier suppression. But it applies.

It is an object of the present invention to provide extremely high levels of stability and reliable suppression of unwanted color carrier portions, with relatively low manufacturing costs and design effort, and without the need for labor-intensive adjustment processes. We do not attempt to provide a method of the type described above in which the results are guaranteed.

The method of the invention comprises converting the carrier signal into a square wave signal in producing a carrier suppression modulated chrominance signal using a modulator device which is supplied with a carrier signal to be modulated and a color information signal to be modulated. The color information signal for modulation is supplied to the modulator device as a sequence of digital amplitude values, each amplitude value encoded with m bits, and the repetition frequency of these digital amplitude values is an integer multiple of the frequency of the carrier signal. and phase-locked to it, each bit of said digitally encoded amplitude value being inverted during one half-cycle of the carrier signal and not being inverted during the next half-cycle, thereby obtaining the Adding each bit to a signal having an intermediate duration value W in the inverting mode and a signal having an intermediate duration value Wn=Y-Z in the non-inverting mode;
The digital signal obtained by this addition operation is converted into an analog signal to produce a modulated chromaticity signal, and the amplitude value Ax at the position of the deviation Y from the driving average value is output on the input side of the modulator device. On the other hand, complete carrier suppression is achieved at the output of the modulator device, so that the carrier-suppressed output signal level is at the output of the modulator device at a deviation of 2 from the driving average value. It is characterized by

The invention also relates to a color carrier modulator device implementing the method described above, wherein the color carrier modulator device of the first embodiment modulates each bit of the digitally encoded amplitude value by means of a carrier signal. said modulator device comprising means for supplying a corresponding first input terminal of a binary adder via a logic element switching between inverting and non-inverting switching states, said modulator device being connected to a second input terminal of said binary adder; and this 2
A carrier/wave signal control switching device is provided to alternately supply values Wi and Wn to a binary adder, and m output terminals of the binary adder are connected to input terminals of a digital-to-analog converter. do.

A color carrier modulator device according to a second preferred embodiment of the present invention includes means for supplying digitally encoded amplitude values and carrier signals to m+1 address lines of a programmable read-only memory. the m data lines of said read-only memory are connected to the input terminals of a digital-to-analog converter, and the m data lines of said read-only memory are connected to the input terminals of a digital-to-analog converter,
is characterized in that the output values for are programmed into this read-only memory for complete carrier suppression.

In this second embodiment, the output value is programmed into the read-only memory even for amplitude values that differ slightly from the amplitude value Ax to achieve complete carrier suppression. It is preferable to make it moist.

The invention will be explained with reference to the drawings. ◇ FIG. 1 shows a first means of the solution according to the invention, namely the means for supplying a digital signal to the modulator arrangement l, i.e. a carrier wave T in the form of a square wave signal of the modulator arrangement l. Envelope of color information signal for modulation, fed to one input terminal ■
1 to another input terminal of the modulator device 1 in the form of a long word string of m bits. In this case, a long output word sequence of m bits is available at the output of this modulator arrangement. In FIG. 1, each digital input/output word string is shown as a string of equivalent analog values.

The amplitude value of the digitally encoded signal H is clocked by the repetition frequency of the clock signal being an integer multiple of the frequency of the carrier wave T to which it is phase-locked. By converting the output word string into an analog signal using a D-A converter 2 (see FIG. 2) and passing it through a filter (not shown), time and amplitude can be obtained from the quantized output signal shown in FIG. produces a continuous output signal.

Of course, the same requirements are satisfied for the output signals shown in FIGS. 4 and 5. The value Ax shown in FIG. 1 is a predetermined input amplitude value at which complete carrier suppression is achieved, which value lies at a deviation Y from the driving average value on the input side.

The resulting carrier wave suppression output amplitude value Am is located at a deviation amount of 2 from the driving average value on the output side. For both of these driving average values, an amount of 2 m−1 was considered,
2m-1-1 may also be considered. The values Y and 2 are important when considering the digital modulator described later. In general, for an optimal drive - and therefore an optimal solution, the deviations Y and 2 should preferably be equal to zero, respectively, or at least very small, but in general these deviations are necessary for plausibility. The displacement is considered to be different from zero in all instances.

The digital modulator device diagrammatically shown in FIG. 2 corresponds to block 1 in FIG. In this case, digital double sideband modulation with carrier suppression is performed as follows.

First, a digitally encoded envelope signal (
(represented by a long word string of m bits) is inverted about the driving mean value 2m-1 during each second half-cycle of the carrier T. This is done by m logic elements.

These logic elements transmit carrier waves to these control input terminals 11! , the input terminals 12 to which modulation signals are supplied and the output terminals 18 are alternately switched between inverting and non-inverting switching states.

It is very suitable to use exclusive OR gates or exclusive NOR gates as these logic elements.

Such an inverted envelope signal at the output terminal 18 of the logic element produces a double-sideband modulated signal (with various imperfections and limitations) when applied to a D/A converter. becomes. First of all, it is necessary to make the deviations Y and 2 zero, but in this case too, complete carrier wave suppression cannot be obtained, and in the best case, one least significant bit carrier wave is generated for the envelope value Ax, 2m-1. remains. (Ax-
Inverting zm-1 results in the value Ax-2-1, which differs from the value Ax by one. ) Y and 2 have zero values, in order to correct this residual carrier, it is necessary to apply the value 1 in each inverted state of the logic element and the value 0 in each non-inverted state to its output terminal 18. be. On the other hand, if Y and/or 2 are different from zero, a simple calculation shows that there is no need to further consider the addition of Wl (bits in phase, □J). In order to completely suppress the carrier wave excess value that occurs in
The value Wn=Yyz is obtained as the term to be added when YZ is in the non-inverted state of the logic element.

In the practical example of FIG. 2, an m-pole change-over switch U is used which is supplied with a carrier wave to the control input terminal 17, and the two terms Wi and Wn are alternately supplied via respective separate input terminals 15 and 16, respectively. The main contact 14 of this switch U is connected to a summing input terminal S'' of a binary adder B. The other summing input terminal S of the binary adder B is connected to a logic element Connect to output terminal 18.

The m data output lines of the binary adder B are connected to the corresponding input terminals 21 of the DA converter 2, and the carrier wave is completely suppressed and modulated at the output terminal 22 of the DA converter 2. A filtered envelope signal is obtained through a filter (not shown).

FIG. 2 also shows that a digital control circuit is included that controls m output signals via m+1 control input lines. Since this digital control circuit is a switching device without memory and feedback, a device equivalent to FIG. 2 can be realized with a programmable read-only memory F. This equivalent modulator, which can be realized fairly inexpensively, is shown diagrammatically in FIG. In this case, for example, an m-bit long FROM with at least m+1 address lines is required, so for example a 512x8 4096-bit FROM, such as the 82S140 type, 8g5147 type or similar types for m-B, is required. Become. The wiring of such a read-only memory can be seen from Fig. 8. In particular, this Fig. 8 shows that m digitally encoded envelope signals and carrier wave signal T are connected to m+1 address lines. supplied, m of memory F
It is shown that the data output line of the book is connected to the input terminal of the D-me converter 2.

The programming mode is evident from the features and functions shown in FIG. 2 for S and S''. This programming mode is shown in more detail in FIG. are activated alternately by the carrier signal T. More specifically, one memory half is activated when the carrier signal is at a high level, and the other memory half is activated when the carrier signal is at a low level. let me,
Also, in each of these memory halves, mutually opposite linear characteristics are programmed that compensate for the deviations Y and 2 and suppress the residual portion of the carrier wave.

A special variation of the two characteristics of FIG. 4 is shown in FIG. These characteristics allow the modulator to suppress a predetermined small signal level Δ surrounding the drive zero point Ax, such as interference signals, noise (α), etc., so that complete carrier suppression (α”) can be achieved with the modulator. The purpose is to process the value (actually the value of carrier suppression only) in memory exactly the same as Ax by programming the bend corresponding to the two characteristics, or even more simply. This is achieved by providing envelope values Mue+Δ and Ax−Δ that act on the output.

[Brief explanation of the drawing]

゛ Fig. 1 is an ls diagram showing the digital input/output signals of the modulator device provided according to the present invention and the relationship between these and each drive average value, and Fig. 2 is an ls diagram showing an embodiment of the modulator device according to the present invention. FIG. 3 is a block diagram illustrating another embodiment of a modulator device according to the invention; FIG. 4 is a block diagram illustrating the read-only memory programming characteristics and modulation processing functions of FIG. The line diagram showing Fig. 5 is the 4th
FIG. 3 is a diagram illustrating programming characteristics that are slightly modified from those in the figure;

Claims (1)

[Claims] 1. In producing a chromaticity signal subjected to carrier suppression modulation using a modulator device to which a carrier signal to be modulated and a color information signal to be modulated are supplied, the carrier signal is The color information signal for modulation, in the form of a square wave signal, is supplied to the modulator device as a sequence of digital amplitude values, each amplitude value encoded with m bits, the repetition frequency of these digital amplitude values being equal to the frequency of the carrier signal. each bit of said digitally encoded amplitude value is inverted during one half-cycle of the carrier signal and not during the next half-cycle; Each bit obtained by
A signal having _i=2A_x+1+Y-Z is added to a signal having a value W_n=Y-Z during the duration of the non-inverting mode, and the digital signal obtained by this addition operation is converted into an analog signal and modulated. complete carrier suppression is achieved at the output of the modulator device for an amplitude value A_x located at the input of the modulator device by a deviation Y from the driving average value, so that 1. A method for carrier suppression modulation of a chromaticity signal, characterized in that the level of an output signal subjected to carrier suppression is at a position of a deviation Z from a driving average value on the output side of a modulator device. 2. In producing a carrier suppression modulated chrominance signal using a modulator device supplied with a carrier signal to be modulated and a color information signal to be modulated, the carrier signal is in the form of a square wave signal. , the color information signal for modulation is supplied to the modulator device as a sequence of digital amplitude values, each amplitude value encoded with m bits, and the repetition frequency of these digital amplitude values is made to correspond to an integer multiple of the frequency of the carrier wave signal. and phase-locked to this, each bit of the digitally encoded amplitude value is inverted during one half-cycle of the carrier signal and not during the next half-cycle, so that each bit thus obtained is , the duration value W of the inversion mode
A signal having _i=2A_x+1+Y-Z is added to a signal having a value W_n=Y-Z during the duration of the non-inverting mode, and the digital signal obtained by this addition operation is converted into an analog signal and modulated. complete carrier suppression is achieved at the output of the modulator device for an amplitude value A_x located at the input of the modulator device by a deviation Y from the driving average value, so that In a color carrier modulator device implementing a carrier suppress modulation method for a chromaticity signal such that the carrier suppressed output signal level is at a position of a deviation Z from a driving average value at the output side of the modulator device,
The modulator comprises means for supplying each bit of the digitally encoded amplitude value to a corresponding first input terminal of the binary adder via a logic element which is switched between inverting and non-inverting switching states by means of a carrier signal. A device is provided, connected to a second input terminal of the binary adder, and configured to input the value W_ to the binary adder.
1. A color carrier wave modulator device, characterized in that a carrier signal control switching device for alternately supplying i and W_n is provided, and m output terminals of the binary adder are connected to input terminals of a digital-to-analog converter. The carrier signal is modulated in the form of a square wave signal in producing a carrier suppression modulated chrominance signal using a modulator device which is supplied with a carrier signal to be modulated and a color information signal to be modulated. A color information signal for a digital signal is supplied to the modulator device as a sequence of digital amplitude values, each amplitude value encoded with m bits, and the repetition frequency of these digital amplitude values is made to correspond to an integer multiple of the frequency of the carrier signal. , and each bit of the digitally encoded amplitude value is inverted during one half-cycle of the carrier signal and not during the next half-cycle, so that each bit thus obtained is inverted. For a signal having a value W_i=2A_x+1+Y−Z during the duration of the mode,
During the duration of the non-inverting mode, add the signal having the value W_n=Y-Z and convert the digital signal obtained by this addition operation into an analog signal to produce a modulated chromaticity signal, and The amount of deviation Y from the driving average value on the input side of the device
Complete carrier suppression is achieved at the output of the modulator device for an amplitude value A_x located at a position of In a color carrier modulator device implementing a method of carrier suppression modulation of a chrominance signal such that the chrominance signal is located at said modulator device comprising means for providing;
The m data lines of said read-only memory are connected to the input terminals of a digital-to-analog converter, and the output value for the amplitude value A_x is programmed into this read-only memory for complete carrier suppression. A color carrier modulator device characterized in that: 4. The color carrier modulator device according to claim 3, wherein the amplitude value A_x is such that output values are programmed in the read-only memory even for amplitude values that differ slightly from the selectable value. A color carrier wave modulator device characterized in that it is possible to achieve complete carrier wave suppression.