Patent GB-1095608-A (GB)
Title: Improvements in or relating to colour television systems
IPC: H04N11/16
Filed: 1966-11-18
Abstract: 1,095,608. Colour television. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. Nov. 18, 1966 [Nov. 23, 1965], No. 51858/66. Heading H4F. The Specification is concerned with the PAL colour television system wherein, in order to separate out the two colour signals #U and Œ #jV from the chrominance signal sequence #F, #F*, F &c. chrominance signals of two consecutive lines, e.g. F and F* are added and subtracted. If the U colour signal, for example, shows a large colour change of #U from line 2 to line 3, along a given vertical line, Fig. 1(a) then the addition of the U colour signal of the previous line, Fig. 1(b), obtained by means of a one-line period delay line, gives the resultant U colour signal variation along said given line as shown in Fig. 1(c). The shaded portion indicates the error as compared with the actual colour signal variation of Fig. 1(a). If, however, half of the colour signal variation, i.e. ¢#U, is added to the U colour signal along said vertical, during line 3, giving the variation shown in Fig. 1(e), then the result of the addition process is shown in Fig. 1(g), wherein for lines 3 and 4, the error is halved, resulting in less final hue distortion. To extract the colour variation ¢#U and add to the original signal, the circuit of Fig. 3 may be used, wherein video consecutive colour signals U and U+#U for lines 2 and 3 are modulated on to the subcarrier fo in balanced modulator 1, to provide the corresponding carrier signals #U and #U+##U. The signal #U + ##U is applied directly to one input of a subtractor circuit 9 and the signal #U is applied to the other input thereof via a one line period delay 8. The output of the circuit 9 is ##U and this is halved by a potential divider 11. An adding circuit 7 combines the signals #U + ##U and 1##U/2 to give the predistorted signal U + 3#U/2. The V signal is similarly treated to give j#V+ j 3##V/2 and this is combined with signal U+ 3##U/2 in adder 5 to give the predistorted chrominance signal F. In the circuit of Fig. 4 the chrominance signals F, F*, F+E, F*+E*, F+F &c., equivalent to the colour variation of Fig. 1(a) are shown as input signals. Consecutive signals are subtracted by means delay 8 and subtracted means 17, to give, for lines 2 and 3 ŒjV+#U, whilst the output of adding means 21 gives ŒjV for said lines. Video signal #U is derived from signal ŒjV+#U by means of synchronous demodulator 18 and carrier signal #U is regained by synchronous modulator 19. In the same manner, but using a quadrature f 0  signal the carrier signal Œj#V is obtained. The two signals are added at 20 to give E, which is halved by attenuator 26 and added at 15 to the original chrominance signal F+E, to give the required predistorted chrominance signals, F, In the circuit of Fig. 5, the carrier signals U and ŒjV &c. are added at 5, to produce the chrominance signals (a) and the conjugate chrominance signals (b) and produced by subtractor 28. These are delayed to one line period to give signal (c), and subtracted at 29 from chrominance signal (a) to give colour change signal (d) having E=#U+j#V at the third line. This is halved by attenuator 26, and added to the chrominance signal at 27 to give the predetermined chrominance signal (e).