DE2911190C2 - Circuit arrangement for the polarity of the phase of SECAM color television signals - Google Patents

Description

The invention relates to a circuit arrangement for the phase alignment of color television signals the SECAM method, which is recorded magnetically, especially in gapless Sc! '- ägspuren should be.

In video recording equipment, it is common practice to convert the composite color video signaJ into the luminance and split the carrier-frequency color signal, with the luminance signal a carrier wave in the To modulate frequency and convert the color signal into a frequency range below that of the frequency-modulated luminous density signal occupied frequency band is for improved utilization of the magnetic tape, it is still customary to record a field per helical track and the helical tracks to write next to each other without space. In order to play such a gapless Adjacent tracks are used to reduce crosstalk from track to track Azimuth offset recorded and scanned, although the azimuth offset only applies to the higher Frequencies, d. H. for the frequency-modulated light density signal, but not for the frequency-converted one Color signal is sufficiently effective. Therefore, the color signal becomes whole before recording reversed certain line rhythm, so that the crosstalk components with simple comb filter circuits can be extinguished.

The aforementioned polarity reversal of the color signal before the recording is based on the precondition that the color carrier is always present in the same phase position at the beginning of each line. This requirement is with SECAM color television process only met to a limited extent, namely only if, for example, test images from simple service generators are supplied; with standard-compliant SECAM color signals, however, the Carriers reversed in polarity in every third row, so that polarity reversal is necessary every third row.

The object of the invention is to provide a circuit arrangement with which both the reverse polarity of each The third line of a standard-compliant SECAM color signal takes place automatically as well as this polarity reversal is omitted if a non-standard, i.e. always the same polarized color signal is present The problem is solved by claim 1

The invention is based on the knowledge that, provided that a standard SECAM color signal is present, the polarity reversal of every third line is simply carried out at the rate of the line frequency divided by 3

in can be, but that there may be a circuit must to match the phase of the switching frequency with the incoming color signal bring. This should be based on the F i g. 1 will be explained in more detail.

i ⁼ . Fig. 1, line A shows the line frequency of the television signal, the arrows drawn below are intended to represent the phase position of a standard-compliant SECAM color signal. A counter dividing by 3 is triggered by the positive-going edges of the line frequency, the output voltage of which actuates the polarity reversal switch for the color signal.If this output voltage has a phase position corresponding to line B, according to line C the desired alignment of the color carrier in each line is obtained. If, on the other hand, the output voltage of the counter has a phase position as in line D, the result in line E shows that the same polarity is not achieved. In order to automatically shift the switching voltage to the correct phase position, the

JO line frequency is also fed to a binary divider, which is controlled by the negative going edges of the line frequency and which always begins to divide when it is determined at the output of the circuit arrangement in a manner to be described later that the correct equalization according to line C is not present. The numerically exact value of the division ratio 2 "of this binary divider is largely unimportant for the invention and can be selected according to aspects that have nothing to do with the invention itself

Line F shows the output voltage of such a binary divider for π = 3; the divider thus jumps in that shown in FIG. 1 shown example with the negative going edge of the third line pulse.

The output voltage of this binary divider is fed back to the counter dividing by three that the Counter is always stopped, i.e. does not emit switching pulses if there is a logical 1 appears; run through during these times

μ therefore the SECAM signals from row A unchanged the circuit arrangement. If the counter, which divides by three, emits a pulse again at point χ, its phase position corresponds to line B, and only occurs at the output of the circuit arrangement

■> ■> lines with the same polarity, the binary counter is switched off and remains at the logical zero.

In the circuit example F i g. 2 becomes the SECAM color signal at terminal I and once directly and simultaneously via an inverter 2 an electronic switch 3 out. The line pulses are at terminal 4 and are a by three dividing counter 5 and fed via an AND gate 6 to a binary divider 7, the Output voltage can stop the counter 5. Of the

h ^r> output of the electronic switch 3 is again supplied via a two-line retarder 8 a subtractor 9 directly and simultaneously. If and only if the switching voltage for the switch 3 is a

Phase position according to line B in F i g. I have arises at the output of the subtracter 9 always the difference zero, the UN D-Güed 6 remains blocked, and the The circuit produces a color signal with the same polarity in each line at terminal 11. In each other The phase position of the switching voltage results in 9 finite differential voltages at the output of the sub-circuit. which are rectified in the time-keeping element 10 and stored for a long enough time to the AND element 6 and put the binary divider 7 into operation.

If, on the other hand, it is assumed that for some reason non-standard, i. H. already polarized SECAM color signals corresponding to line C in FIG. I at the terminal 1 are present, and in line G, Fig. 1, the same phase for the switching voltage is arbitrarily as based on line B, the results in Fig. 1,

Line H indicated polarity of the color signal. The binary counter 7 jumps after the third line pulse at. As can be seen from line H, no difference signals arise at the output of the subtracter 9 more, so that the divider 7 with the logical 1 am

turns off in the output and stops the counter 5 continuously; thus no switching voltages arise at the output of 5, and the changeover switch 3 always remains same switch position.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Circuit arrangement for Gleichpoiung the phase position at the beginning of each line of its carrier frequency Color signal according to the SECAM method with the aid of a polarity reversal switch, characterized in that that the switching voltage for the changeover switch (3) from a dividing by 3 and by the positive going line pulses driven counter (5) is supplied that the counter (5) by one of the two logic states in the output voltage of a binary divider (7) is stopped and that the binary divider (7) is controlled by the negative going line pulses and only when Color signals with unequally polarized lines appear at the output of the switch (3). 2. Circuit arrangement according to claim 1, characterized in that the output of the changeover switch (3) is fed directly and via a two-line delay (8) to a subtracter (9), its output voltage according to the corresponding Rectification and smoothing puts the binary divider (7) into operation