JPH0248889A - PAL color subcarrier phase synchronizer - 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 Field of the Invention The present invention relates to a PAL color subcarrier phase synchronizer.

Conventional Technology The color television system used in Europe is called PAL (Phase Altered Line).
It is an integer of 4 cycles plus the small fraction of cycles that occur while scanning each line. In this case, between fields the subcarrier has a phase that is 180 degrees different from the phase it had when we started scanning the just completed field, so that the subcarrier has a phase of two 174 degrees at the beginning of the next field. This also reduces the perceivability of the dots formed by the presence of color subcarriers in the image formed on the screen of the television receiver due to the following reasons:
If there were an integer number of 1/4 cycles occurring during the time of a line scan (so that we could see dots occurring at sharp vertical corners within a single field) it would not be particularly noticeable (-but If the dots are formed in a continuous field, they will appear to move very slowly in a diagonal direction, so the eye will have a strong tendency to follow them.

Therefore, instead of using a subcarrier frequency of 1135/4 times the line scan frequency Fh, which gives an integer number of cycles during the line scan time, the chrominance subcarrier frequency in a PAL system te1/
The dots are increased by 25 Hz to achieve a non-integer number of 4 cycles, i.e. a fraction of a cycle occurs between each line to an integer number of 1/4 cycles. As they move in the direction, the tendency of the eye to track them is significantly reduced, thereby making them less noticeable.Problems the invention seeks to solve It can also cause serious problems in digital signal generators, processors, time base collectors, and other digital equipment, and
Whether locking to the color subcarrier must be done at field intervals equal to an integer number of cycles.
A single sideband heterodyne circuit or a multiphase locked loop is required, resulting in a complicated circuit configuration.The present invention addresses the above problem and aims to provide a PAL color subcarrier phase synchronization device with a simple circuit configuration. A. Means for Solving the Problems The first invention is an apparatus characterized by comprising field signal generating means that changes polarity between fields, and means for inverting the phase of a subcarrier thereby.

The second invention is a device characterized by having a field signal generating means that changes the polarity between fields, and means for inverting the phase of the color difference signal thereby.The third invention is a field signal generation means that changes the polarity between the fields. According to the invention, the chrominance subcarrier used is divided into 1/4 cycles along one line. In order to have an integer of 1,135/4 of the line scanning frequency, i.e., IH, the field signal generating means changes polarity between fields. , thereby converting the carrier during the blank interval between fields by providing means to invert the phase of the subcarrier or color difference signal. chrominance subcarrier conversion (similar to their position in a PAL system) chrominance subcarrier conversion (i.e. converting the phase between fields before the phase is modulated by the chrominance signal, or the phase they are used to modulate that subcarrier) This can be achieved by converting the phase of the chrominance signal between fields or by converting the phase of the chrominance signal between fields formed by modulating the subcarrier with the chrominance signal. This figure shows the first embodiment of this.The operation will be explained below.1/4 that occurs during the line scanning time
Before the phase of the color subcarriers with an integer number of cycles is shifted by 180 degrees between fields before they are modulated with the color difference signal, the color subcarrier SCl & signal source 2 with an integer number of 1/4 cycles occurs during the line scan time. The field signal 6 is generated by a multiplier 1 that multiplies the line scanning frequency H derived from 1135 by 1135 and a divider 3 that divides the output 1135H of multiplier 1 by 4. is input to the clipper 7 to obtain the color recovered carrier wave SC and the field signal 6 which reverses the polarity between fields is input to the double balanced modulator 4. The subcarrier at the output of the double-balanced modulator 4 has one phase, and the subcarrier at the output of the modulator 4 has one phase during the next field when the field signal 6 has the opposite polarity.
SC has opposite phase. This subcarrier MOD SC
is coupled to one input of the dual-balanced color modulator 5, while the color difference signal from the color signal source 4 is applied to the other input of the color modulator 5. Standard PAL subcarriers are generated during line scanning. Since it does not have an integer of 18 cycles, its phase moves throughout the field during the line scan time, but at the beginning of the next field the accumulated movement is 180 degrees. The subcarrier of 1/4 occurs during line search so that it can be easily locked with the line synchronization signal.
The power has an integer number of cycles (but because of the modulator 4, the subcarrier undergoes a 180 degree phase shift to make it identical to the PAL subcarrier and starts the next field with 4-color modulation. The output of the adder 5 is connected to the output terminal T1 through a bandpass filter that passes the color signal.One input of the adder 9 is TIK, and its other input is the studio equipment 10.
A second embodiment of the invention is shown in FIG. 2.

Here, instead of modulating the subcarrier SC with the modulator 4 in FIG. 1, the color signal is inverted for each field in the color inversion circuit 11 to calculate the color signal MOD D.
D and the subcarrier SC to obtain the same modulated color signal as shown in Figure 1.The output of the color modulator 5 is passed through the bandpass filter 8.
The luminance signal Y may be coupled to one input terminal T2 of the adder 9 via the input terminal T2 of the adder 9 to produce a new overall video signal that can be coupled to the studio equipment 10. FIG. 3 shows a third embodiment of the present invention. The color subcarrier having an integer number of quarter cycles occurring during the line scan time changes the phase between fields by converting the polarity of the color signal. In this embodiment, as shown in FIG. 1, the field signal 6 is input to the modulator 4 to invert the phase of the subcarrier for each field. By inverting the phase of the modulated color signal for each field, the same modulated color signal as in Figure 1 is obtained.In Figure 3, the modulated color signal is added through a bandpass filter 8 that passes the color signal. Another input of the adder 9 is also connected to receive the luminance signal Y from the signal source 2 to provide a new composite video signal to the studio equipment 10. The effect of this is that the subcarrier phase shifts by one half cycle during the line scanning period. By providing a circuit that generates a color signal that is simultaneously reversed between fields, the circuit scale can be reduced, and the standard PA
Dot interference can be reduced to the same extent as is done in L color television systems.

[Brief explanation of the drawing]

Figures 1 and 3 are block diagrams of PAL color subcarrier phase synchronization devices according to different embodiments of the present invention.

Claims (3)

[Claims] (1) The video signal generator 2, the color modulator 5 having first and second input sections and one output section, and the color subcarrier signal generation means 1 and 3, changing the polarity between fields. a field signal generating means 7; a subcarrier modulator 4 for inverting the phase of the color subcarrier by the field signal;
first coupling means for coupling a second subcarrier signal, which is the output of this subcarrier modulator 4, to a first input of said color modulator 5; A PAL color subcarrier phase synchronization device comprising second coupling means for coupling color difference signals of the video signal generator. (2) The video signal generator 2, the color modulator 5 having first and second input sections and one output section, and the color subcarrier signal generation means 1 and 3, changing the polarity between fields. a field signal generating means 7, a color inverting circuit 11 for inverting the color difference signal output from the video signal generator 2 by the field signal, and a second color difference signal output from the color inverting circuit 11 being applied to the color modulator. PAL color subcarrier phase synchronization device comprising first coupling means for coupling the subcarrier to a first input of the color modulator 5 and second coupling means for coupling the subcarrier to a second input of the color modulator 5. . (3) Video signal generator 2 and color subcarrier signal generation means 1
3, field signal generating means 7 whose polarity changes between fields, color modulator 4 which modulates the color difference signal output from the video signal generator 2 with this color subcarrier, and A PAL color subcarrier phase synchronization device comprising a modulator 5 for inverting the phase with said field signal.