Patent GB-1061885-A (GB)
Title: Improvements in or relating to colour television transmission systems
IPC: H04N11/22
Filed: 1964-03-04
Abstract: 1,061,885. Colour television. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. March 4, 1964 [March 9, 1963], No. 9156/64. Heading H4F. The invention relates to transmitting and receiving in addition to the luminance signal (Y<SP>1</SP>) two combined colour signals which are so derived from the colour signals (R<SP>1</SP>, B<SP>1</SP>) of the basic colours and the luminance signal (Y<SP>1</SP>) that their linear combinations at the receiver result directly in the colour different signals R<SP>1</SP>-Y<SP>1</SP> and B<SP>1</SP>-Y<SP>1</SP> or the colour signals I<SP>1</SP> and Q<SP>1</SP> of the N.T.S.C. system. The invention further comprises a receiver which will receive SECAM (Trade Mark), PAL and N.T.S.C. type signals. Fig. 2 shows a receiver for receiving amplitude modulated signals U<SP>1</SP>, V<SP>1</SP> with suppressed carrier in successive lines, i.e. according to the SECAM system, wherein the combined colour signals U<SP>1</SP> = (R<SP>1</SP>-Y<SP>1</SP>) - (B<SP>1</SP>-Y<SP>1</SP> and V<SP>1</SP>= (R<SP>1</SP>- Y<SP>1</SP>) + (B<SP>1</SP>-Y<SP>1</SP>). The colour carrier frequency signal from which the luminance signal Y<SP>1</SP> has been filtered out appears on lead 1 and is fed as shown to adding stages 5 and 6 via a 180 degrees phase shifter 8, a line period delay member 2, amplifier 3 and adjustable phase shifter 4. The output from adding stage 5 is U<SP>1</SP>-V<SP>1</SP> = - 2(B<SP>1</SP>-Y<SP>1</SP>) or V<SP>1</SP>-U<SP>1</SP> = 2(B<SP>1</SP>-Y<SP>1</SP>) and the output from adding stage 6 is U<SP>1</SP>+V<SP>1</SP> = 2(R<SP>1</SP>-Y<SP>1</SP>). For demodulation the colour carrier, which is not transmitted, is added in stages 5 and 6 by means of a reference carrier oscillator 10 which is synchronized over lead 11 by the colour sync. pulses produced by filtering out line impulses 19. The reference carrier is fed to adding stage 5 via a switched phase shifter 14, Fig. 4 (not shown), which is switched by means of a half line-switching pulse wave 34 and serves to equalize the signs of the colour difference signal (B<SP>1</SP>-Y<SP>1</SP>) which reverses from line to line. The colour carriers are demodulated by amplitude demodulating rectifiers 15, 16 to produce the two colour difference signals B<SP>1</SP>-Y<SP>1</SP> and R<SP>1</SP>-Y<SP>1</SP>. Fig. 5 shows a receiver for receiving SECAM signals and PAL signals and the parts corresponding to those of Fig. 2 are designated by the same references. For receiving SECAM signals with suppressed carrier, switch 19 is closed so that a 90 degrees phase shifter 20 is shorted out and the operation is as described for Fig. 2 except that the reference carrier is fed into the clamping demodulators 15, 16 serving as rectifiers, colour difference signals B<SP>1</SP>-Y<SP>1</SP> and R<SP>1</SP>-Y<SP>1</SP> being obtained at outputs 17, 18. For reception of PAL signals switch 19 is opened and the output of adding stage 6 yields a colour carrier frequency signal + 2Q<SP>1</SP> on every line since the I<SP>1</SP> signals cancel, and adding stage 5 yields the signal components modulated along the I<SP>1</SP> axis since the Q<SP>1</SP> signals cancel. The I<SP>1</SP> signals from adding stage 5 are alternatively shifted through 90 degrees in one direction and then through 90 degrees in the other direction relative to the Q<SP>1</SP> axis and thus the reference carrier used for demodulation must be shifted in successive lines through Œ90 degrees. This is achieved by means of 90 degrees phase shifter 20 and switched phase shifter 14 which is alternately switched to produce phase shifts of 0 degrees and 180 degrees. The opening or closing of switch 19 thus enables the receiver of Fig. 5 to receive either PAL or SECAM signals. In a further embodiment a SECAM signal is transmitted so that by using the receiver shown in Fig. 5 the outputs at 17, 18 yield the signals + 2Q<SP>1</SP> and + 2I<SP>1</SP>. The two amplitude modulated combined colour-signals alternately transmitted for this embodiment comprise the signals Q<SP>1</SP> = Q<SP>1</SP> + I<SP>1</SP> = 1À22 (R<SP>1</SP>-Y<SP>1</SP>) + 0À145 (B<SP>1</SP>- Y<SP>1</SP>) and P<SP>1</SP>= Q<SP>1</SP>-I<SP>1</SP> = -0À26 (R<SP>1</SP>-Y<SP>1</SP>+0À68 (B<SP>1</SP>-Y<SP>1</SP>). As before the output of adding stage 6 is + 2Q<SP>1</SP> and the output of adding stage 5 is +2I<SP>1</SP>, - 2I<SP>1</SP>, the different signs of Œ2I<SP>1</SP> being equalized by phase reversal of the reference carrier. Therefore by switching switch 19 the receiver will receive either SECAM signals O<SP>1</SP>, P<SP>1</SP> or PAL signals, the outputs 17, 18 yielding the signals 2Q<SP>1</SP> and 2I<SP>1</SP>. A receiver circuit for receiving frequency modulated SECAM signals, modulated with combined colour signals U<SP>1</SP> and V<SP>1</SP> is described, Fig. 6 (not shown). The invention may also be used in conjunction with a normal N.T.S.C. system in which the two colour signals are of the form U<SP>1</SP>=¢ (R<SP>1</SP>-Y<SP>1</SP>) -¢ (B<SP>1</SP>-Y<SP>1</SP>)=¢ (R<SP>1</SP>-B<SP>1</SP>) and V1=¢ (R<SP>1</SP>-Y<SP>1</SP>)+¢ (B<SP>1</SP>-Y<SP>1</SP>)= ¢ (R<SP>1</SP> + B<SP>1</SP>) - Y<SP>1</SP>, the receiver forming the sum of V<SP>1</SP> and U<SP>1</SP> to produce R<SP>1</SP>-Y<SP>1</SP>, and the difference to produce B<SP>1</SP>-Y<SP>1</SP>.