DE3435562C1 - Method for transmitting a colour television signal in time- and frequency-division multiplex - Google Patents

Abstract

To transmit a colour television signal which contains a luminance signal component and a modulated colour subcarrier, only the luminance signal is transmitted with the full bandwidth of the transmission channel during an arbitrary line and a frequency-division multiplex which consists of the luminance signal reduced in bandwidth and the modulated colour subcarrier is transmitted during the subsequent line. Together with the wide-band luminance signal and the frequency-division multiplex, a colour synchronisation signal (burst) is also transmitted. The high-frequency components of the luminance signal component are prefiltered in the vertical direction at the transmitter end in such a manner that the undelayed high-frequency luminance signal components are added in equal parts to the high-frequency luminance signal components delayed by one television line. As an alternative to this, the undelayed wide-band luminance signal component and the wide-band luminance signal component delayed by one frame can be used line-periodically as luminance signal at the receiver end.

Description

F i g. 3 shows the spatial frequency plane reproduced with the prefilter. The hatched areas show the Areas with 2 6 dB suppressed Resolution in the diagonal direction.

It goes without saying that instead of the simple vertical filter shown for the purpose of a changed attenuation curve also higher-grade vertical filters with multiple line delays and different coefficients can be used can.

The pre-filtered signal YH is added to the low-frequency signal in an adder 50 The YT component is added, from which the Y signal results. The Y * and YT signals become line-sequential used as the luminance signal to be transmitted.

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Claims (2)

Claims: 1. A method for transmitting a color television signal in time and frequency division multiplexing a luminance signal component and a contains modulated color subcarrier, in which only the luminance signal during any line with the full bandwidth of the transmission channel and during the following Line a frequency multiplex is transmitted, which from the reduced in bandwidth Luminance signal and the modulated color carrier consists, together with the broadband luminance signal and the frequency multiplex a color sync signal (Burst) is also transmitted, characterized in that the high-frequency Portions of the luminance signal component in the vertical range are pre-filtered, such that the undelayed high-frequency luminance signal components with the um a television line delayed high-frequency luminance signal components with the same Proportions are added. 2. The method according to claim 1, characterized in that the vertical Pre-filtering of the high-frequency portions of the higher-grade luminance signal component Vertical filters with multiple line delays can be used. The invention relates to a method according to the preamble of claim 1. Such a method is that of DE-PS 3338 192 on which it is based older patent application. Due to the need for compatibility with monochrome Signals are PAL, NTSC and SECAM in the television systems currently in use the luminance components and the two color components in frequency division multiplex transfer. As is known, this has the consequence that when reproduced in a color receiver Cross-talk effects (cross-color, cross-luminance) occur, which affect the image quality affect. In addition, the width of the luminance signal is also restricted Elimination of these effects becomes particularly desirable if major ones in the future Screens are used. In designing an improved television broadcast method, you must In particular, the following points must be taken into account: Adaptation of the signal to existing ones Transmission characteristics (RF transmission, cable transmission, recording on Video recorder) as well as compatibility with existing receiving equipment. Upward compatibility is also desirable in the sense that the improved system can also process signals from the existing system, d. H. productions recorded on magnetic tape. A color television broadcasting method that meets the aforesaid requirements fulfilled, shows practically no crosstalk effects and one in the horizontal direction provides improved resolution of the luminance signal is in the older DE-PS 3338 192 described. The basic idea of this improved method is based on the Spectrum according to FIG. 1 illustrates. Line 1 shows a broadband luminance signal transmitted, together with the normal PAL burst (no chrominance information). In line 2 the low-frequency components of the luminance signal (2.9 MHz 6 dB), the normal PAL color signal and also the normal PAL burst. This Change is repeated continuously. So it will only change the color every other line and the full luminance bandwidth is only sent every second line This means that the high-frequency components of the luminance signal component and the modulated Color carriers (PAL color signal) are transmitted in time division multiplex. Optionally, this line-alternating transmission take place in such a way that the phase position of the switchover of color and light signal is the same at the beginning of each full screen (full screen reset) or switch from full screen to full screen. In the receiver you get a broadband luminance signal for line 1; the luminance signal of line 2 is composed of the low-frequency com components of line 2 and the high-frequency components of the previous line 1. As far as the color is concerned, line 2 contains those transmitted in this line Signals with an everywhere bandwidth of e.g. B. 1.3 MHz 6 dB. In the following Line 3, in which no color is sent, simply becomes the color of the previous one Row 2 repeated. By transmitting the high-frequency luminance components in however, only every second line results in a reduced resolution of the luminance signal in a diagonal direction, causing certain disturbance structures. The object of the invention is to provide a method of the above mentioned type to the effect that the above interference structures transmitter to be suppressed. According to the invention, the object is achieved by the characterizing features of claim 1 solved. An advantageous development of the method according to the invention results from the subclaim. The invention is explained in more detail with reference to the drawings F i g. 2 shows a block diagram of a device for vertical pre-filtering at the transmitter end of the luminance signal, and F i g. 3 with the help of the device according to F i g. 2 reproduced spatial frequency plane. In Fig. 2 is the solution to the problem by means of a pre-filtering of the The luminance signal illustrates high-frequency components of the luminance signal Y is determined by means of the low-pass 10 and the high-pass 20 (each with a cut-off frequency from Z. B. 2.9 MHz) into a low-frequency component YT and a high-frequency component YH split up. The latter is subjected to vertical filtering, the vertical filter from a line delay element 30 (64 Us delay time), an adder 40 and a branch line 60 consists. The adder 40 is thus once Signal Y delayed by one line and once (via branch 60) the undelayed one Signal YH supplied. In the output signal of the vertical filter 30, 40, 60 are the input mentioned disturbance structures largely eliminated. The one shown in the example Vertical filter is the simplest interpolation filter (1.1 filter) with a zero in the amplitude frequency response with 144 active periods per picture height.