DE2138826A1 - Decoding system for a color television receiver - Google Patents

Description

Patent attorneys

Dip! - In ₉ . H. MITSCHERLICH ZI 000 ^ 0

Dipl.-Ing. K. 6ÜNSCHM4NH

Dr. rer. not. W. KORSER
MANCHEN 22. SteinsdorfsU. 18 3 August 1971

Patent type notification

SONY CORPORATION, 7-35 Kitashinagawa 6-chome Shinagawa-Ku, T ο ky ο, Japan

Decoding system for a color television receiver

The invention relates to a color television receiver which is suitable for receiving signals which are transmitted with a line-sequential phase change in accordance with the PAL system. In particular, the invention relates to a decoding system which can be used in a color television receiver which is suitable for receiving PAL color television signals _#

In the PAL system, two become one chrominance information containing color difference components simultaneously to a color carrier within the video frequency band by quadrature amplitude modulation modulated with suppressed carrier. If there is any phase disturbance on the transmission path occurs between the bait of the transmitting station and the demodulators of the receiver, this interference remains with a high degree of probability constant over a period of time that is longer than a line duration. The hue of the off The television picture reconstructed from the received signal by the receiver is derived from the phase angle of the chrominance signal determined and is therefore in undesirable

209817 / 12Ai

Way through which affects live fault unless that Phase disturbance is compensated. Done through the PAIr system the compensation of phase errors by the inversion the color sequence at the end of each file. The phase of the burst signal, which precedes each line is linked to the information about the color sequence of the line in question encodes that the phase of the burst signal for the one Line is shifted 90 ° forwards and for the next line by backwards. Live disturbances that occur during a color phase sequence represented by a line would shift the image into the blue rope of the spectrum, will still produce the same phase error in the following line · Due to the difference in In the phase sequence between the first line and the following line, this phase error shifts the hue however in the red part of the spectrum. Provided that the brightness remains basically constant and taking into account the fact that the information on a line differs very little from the information on the next line differs, the hue shifts in the blue direction and in the red direction the tendency to compensate each other.

In the so-called simple PAL receiver, this compensation is carried out by visually averaging the lines. Included however, an effect is created which appears in the picture as "Venetian curtains", which line by line crawl forward. With a somewhat more complex PAL receiver the averaging takes place by delaying the chrominance signal by exactly one line duration. That delayed Signal is then combined with the signal representing the next line. That way will the annoying line pattern in the form of the "Venetian curtains" avoided; however, it must have the disadvantage must be accepted that the vertical color resolution is reduced and the structure of the receiver is more complicated will,

209817/1243

The PAL-system has the advantage ₉ that it eliminates phase errors which lead to larbtonänderungen, but at the same time it makes it "impossible in such a PAL receiver., Adjust the color tone vonlfend. Such a setting is" sometimes desirable effects to correct that have nothing to do with phase errors «,

There is already a system for DekocSerung in the earlier German application P 20 64 153.6 of the same applicant Sound PAL color television signals have been proposed, which avoids some of the disadvantages of the known PAL decoders will. This new system is theoretically able to receive signals from either a PAL transmitter or a so-called ITTSC broadcaster (like the one in the USA is used} broadcast even though the actual broadcast carrier frequencies used in these two broadcast television systems -used-making it impossible to actually take advantage of this last-mentioned property to take advantage of.

The coding system of the referenced copending application includes a switch and a delay line through which the received chrominance signal is routed. This The chrominance signal is first fed directly to the demodulators during a line interval. After that, the same information during the next line interval delayed by one line, again via the switch, forwarded to the demodulators. The chrominance information broadcast by the television broadcaster during the second time interval is not used by the receiver «The signal transmitted during the third time interval is then passed back to the demodulators without delay. During the fourth time interval, the demodulators receive again that broadcast during the third time interval " signal now delayed by line duration.

209817/1242

An improved one is also from the same applicant A decoding system has been proposed in which a separate switch and an inverter are used to generate burst signals or to obtain inverted replicas of the same with which one of the auxiliary carrier generators is controlled will. This subcarrier generator is used to generate a reference carrier signal of suitable phase for one of the demodulators. The other reference carrier signal for the other demodulator is controlled by a separate oscillator generated using the successive burst signals. The burst signals are integrated or averaged and, if necessary, inverted to a second reference carrier signal to generate whose phase is shifted by 90 ° with respect to the phase of the first reference carrier signal. In each of the Embodiments of the mentioned proposal of the same Applicant has used each subsequent burst signal to adjust the phase of the reference carrier signal in the desired Way to adjust, this was done despite the fact that by the combination of the switch and the Delay line only every second chrominance signal was evaluated.

The object of the present invention is to provide an improved system for decoding the chrominance signals of a PAL color television signal.

The invention relates to a decoding system in which a reference carrier signal is generated which has a constant Has phase angle, and in which the reference carrier signal for the other chrominance component is generated at an angle different from the correct angle. Either the last-mentioned reference carrier signal is corrected by vector addition, or the resulting demodulated signals are corrected with the aid of a matrix operation.

209817/1

Further features can be found in the following description and the drawings.

According to the invention, separate oscillator systems are used to generate reference carrier signals for the two chrominance components to create. The chrominance components themselves are modulated onto a subcarrier in phase quadrature, with one of the components has a constant modulation axis while the other component has a modulation axis, whose phase changes by 180 ° at the end of each line. The modulation axis with the changed phase is either shifted by + or by - 90 ° with respect to the constant axis. The instantaneous chrominance signal is the Vector sum of the two component signals. The phase of The vector sum corresponds to the hue of the chrominance signal.

According to the present invention, the signal whose modulation axis remains constant is in one Synchronous demodulator, which is supplied with a locally generated reference carrier signal. This reference carrier signal has a phase suitable for demodulating the signal. In one embodiment, the same chrominance signal is used fed to a second demodulator and demodulated with the aid of a reference carrier signal which is the same Phase as the alternating burst signals did. This phase is shifted by 45 ° compared to the correct phase, so that the demodulated signal in a matrix circuit with the other demodulated signal and the Luminance signal must be combined in order to do this generate the three primary color signals which are fed to the cathode ray tube of the television receiver.

Alternatively, the locally generated reference carrier signal may be vectorial to the locally at an incorrect angle generated reference carrier signal with the correct constant angle can be added. The vector sum

209817/1242

results in a second reference carrier signal, which is the desired Has phase angle that is 90 ° with respect to the reference carrier signal is shifted with the constant phase angle. Furthermore, this vectorial addition automatically with the burst signal that is the one passing through the delay line and the switch Chrominance signal corresponds. The resulting locally generated reference carrier signal not only has one phase, which is shifted by 90 ° with respect to the constant reference carrier signal, but it is also automatically in the Desired angle orientation shifted.

Embodiments of the invention are described below with reference to the drawings.

Show it:

1 shows a vector diagram for explaining the coding and the decoding in a PAL Parb television system;

Pig. Figure 2 is a block diagram of one embodiment of a decoding system according to the invention;

Pig. 3 to 5 vector diagrams showing the relative phase angles between the burst signals, the reference carrier signals and show the chrominance signals and their components;

Pig. 6 is a block diagram of a modified embodiment of the invention;

Pig. 7 is a block diagram of another modified embodiment of the invention;

209817/1242

Pig. 8 and 9 vector diagrams to explain the in Pig. 7th illustrated decoding system;

Pig.10 is a block diagram of another embodiment the invention;

Pig. 11 vector diagrams of signals, which during operation des in Pig. 10 are generated decoding system;

Pig.12 an adding circuit which is used in the decoding system after Pig. 10 is used |

Pig. 13 demodulation vector diagrams for the in Pig. 10 circuit shown.

The essence of the PAL color television system is the phase relationship between the two color difference signals that are modulated onto a common color carrier to form a chrominance signal. This phase relationship is in Pig. 1 shown. The Chrorainance component Eg - Ey contains information relating to the blue components of the television picture. The other chrominance component E _R - Ey contains information which corresponds to the red components of the television picture. Both chrominance components are modulated onto the same carrier, or more precisely, the same subcarrier. The modulation is carried out separately, however, in such a way that the carrier on which the chrominance component E _R - Ey is modulated has the phase ^ ₀ in a predetermined time interval which corresponds to the duration of a line of the color television picture. During the same time interval, the carrier on which the other chrominance component E ₁₃ -Ev is modulated

m · ΰ Χ

fm · ΰ Χ

- —rj— · For this reason one can use the

Chrominance component (E _B - Ey) _n , welohe during one

2098 17/1 242

" ⁸ " 2139826

given time interval η with line duration the blue one Information represented by a horizontal arrow while then the red chrominance component (EL - Εγ) during the same time interval η then through a vertical arrow can be displayed. By vector addition of these two chrominance components, generates a resultant signal F which is defined by a complex voltage according to the following equation is

The phase relationship between the following line η + 1 is also shown in FIG. In this case, the blue chrominance component during the line is η + 1 = (EQ - Ey) + ι · Εί · ^Θββ "blue chrominance component has the same direction as the component (Eg - Εγ) _η · However, according to the PAL system, the red chrominance component (Er, ^"1 V) _{11 +} I η inverted with respect to the chrominance component for the preceding line. This results in

F + 1 following equation!

In order to simplify the description of the present invention, the terms "+" and "-" shall be used in relation to the burst signals and the chrominance signals. The expression "plus" is intended to be used to identify those line intervals in which the red difference component Er, - Εγ has a modulation axis that runs vertically upwards in the direction of Ψ ~ . During such a time interval the vector sum of the chrominance components can be denoted rait F ₊ . This vector sum is in FIG. 1 in the first quadrant. The burst signal for the same interval is _{labeled B +} and is in the second quadrant.

209817/1242

It is phase shifted by 45 ° with respect to the axis j '. If the modulation axis for the red color component is - γ and the red color difference signal is represented by the expression - (Er, - Ey-), then the burst signal B lies in the alternating line intervals in the third quadrant and is opposite to the - γ ~ - Axis 45 out of phase. The chrominance signal can be identified as F__ and is in the fourth quadrant.

Pig. Fig. 2 shows a block diagram of a decoding system that may be used in a color television receiver which is suitable for receiving PAL signals. The entrance of the Decoding system is formed by a bandpass amplifier 1, which is based on the chrominance signals of a composite Color television signal is matched. The output signal of the bandpass amplifier 1 is the input of a 'delay circuit 2 and an input terminal 3 of a switch 4 is supplied. The output signals of the delay circuit 2 are fed to the second input terminal 5 of the Switch 4 supplied. The switch 4 works as a single-pole changeover switch. The switch 4 also has an output connection 6 which is connected to the input connection of two demodulators 7, 8, in which the color difference signals are separated from each other. The switch 4 is with a flip-flop 9, which controls the switching of the switch 4.

The output terminal 6 of the switch 4 is also connected to a burst gate 10. The output of the burst gate 10 is in turn connected to a generator 11 which generates a signal with a continuous waveform. The generator 11 can be a crystal oscillator. The output signal of the generator 11 is fed to an oscillator 12 in order to control it. Those generated by the oscillator 12 Signals are fed to the demodulator 7.

209817/1242

~ ¹⁰ ~ 2138825

The output product of the bandpass amplifier 1 is also connected to a second burst gate 13. The burst gate 10 and the burst gate 13 are connected to a generator 14, which generates gate switching pulses with which the Burst gates 10 and 13 are gated on. The starting product of the burst gate 13 is fed to a generator 15 which generates a signal with a continuous waveform generated. The '15 generator can be a crystal oscillator be. Its output product is fed to an oscillator 16 in order to control its function. The output signal of the oscillator 16 is in turn fed to an inverter 17. The inverter 17 inverts the signals generated by the oscillator 16 and feeds them to the demodulator 18. the Output products of the two demodulators 7 and 8 are fed to a matrix circuit 18. The matrix circuit 18, the luminance signal Ey- is also supplied via an input terminal 19.

The function of the in Pig. The circuit shown in FIG. 2 will now be described in connection with the phase diagrams 3 to 5. The chrominance signal, which is given by the sequence ^Έ η * * n + 1 ^{f F} n + 2 * \ + 3 '* "

fed to the bandpass amplifier and then in the Yer—

f delay circuit delayed by one line duration. The delayed signal shall be identified by adding a prime to each of the components. This delayed signal F « _n , F« _{n + 1} , ⁵ V + 2 ' ¹ V + 3' ^ ¹ " ^{1 as}

continuous signal fed to the input terminal 5 of the switch 4. The original chrominance signal F _n , ^ _{n +} -Jt F ₊ 2 » ¹ Ii + 3 '* * * * ^w ^ ^{rd is} also fed directly to the input terminal 3. The signals fed to the connections 3 and 5 are alternately transmitted from the switch 4 by the control action of the flip-flop 9. The output signal at terminal 6 of the switch 4 is thus _n F ^ 'n ^1' ^ n + 2 "^ 'n + 2" · ^{"The ers" te} T ^erm> ^ _n * consists of an undelayed signal during a Line

209817/1242

errinterval occurs when the terminal 3 is connected to the output terminal 6 as shown in the drawing. During the next line interval, the flip-flop 9 toggles the switch 4 so that the input terminal 5 is connected to the output terminal 6. As a result, the same signal occurs at the output connection 6 as F ¹ . In the third line interval the switch is switched back to the starting position (see FIG. 2), so that now a new undelayed signal F. ^ occurs, which was sent two lines later than the first instantaneous signal. These signals are fed to the demodulators 7 "and 8. In the fourth time interval the switch is switched back to the reverse switching state in which the output terminal 6 is connected to the input terminal 5. As a result, the delayed signal F occurs at the output terminal 6 as a result of the delay switch 2 ^1, ₂ , which was transmitted during the third time interval. This signal is again fed to the demodulators 7 and 8. The demodulators 7 and 8 therefore each receive the same signal in two successive time intervals with a line duration Line duration, a different signal is then fed to the demodulators, etc.

If the signals ^ _n * _n ^ + 2 ^ n + 4 "·" ·· ^as occurs and the switch 4 at the time of arrival of these plus signals are in the position shown in FIG. 2 position, it is a sequence of plus color difference signals are generated at the output of the demodulator. During the alternating line intervals, which correspond to the arrival times of the signals ■ * n + 1 '^ n + 3'"^ n + 5 '·' · '^{eni; s} P ^{rec]: ien} » where the last • mentioned signals must be minus signals, since the other signals were plus signals, switch 4 is in the opposite position. The consequence of this is that only plus signals are sequentially derived from switch 4,

209817/1242

twice in the order F _n , Ρ ' _η , F 2 »····! whereas minus signals are not derived. The demodulator 8 receives the same plus chrominance signal F. In order to demodulate the signals in the demodulator 8 in such a way that correct blue color difference signals are generated, reference carrier signals must be fed to the demodulator 8, which have a phase ^ ₀ 3> -

to have. The output product of the demodulator would then be a sequence of color signals in the order: (En -%) _n »(E _B - Ey) V ( ^E _B - Ey) _n + 2 '( ^E B" ² Y ^' n + 2 »···

If the arrival of the plus signals F ", F". ₉ , F ",, ...

XX Xl T ^ Xl "ι τ *

the flip-flop 9 is toggled to set the switch in the position opposite to the position shown, the switch 4 derives only minus signals twice in succession in the following order: ^ _{n +} -, »Ι " _η + 1 ' ^P n + 3' ¹ ^ n + 3 '···» whereas plus signals are not derived from the switch.

In this case, the demodulator 8 must receive reference carrier signals ₀ - -Tj- (as in the case described above)

be supplied because their phase remains constant. As a result, the demodulator 8 derives a sequence of demodulated color signals (^ - Ey) _{n + v} (B _{B n +} 2, · · · ·.

The chrominance signal separated by the bandpass amplifier 1 is fed to the burst gate circuit 13. _{The burst signals B +} and B _- shown in FIG. 5, which are contained in the plus and minus signals η, are alternately transmitted by the burst gate, the control of the burst gate 13 being controlled by the gate pulse generator 14 off takes place. The burst signals are fed to the generator 15, which _{turns them into a signal S 2} with a continuous waveform, the phase of this signal being set to a mean value between the phases of the signals B ₊ and B,

209817/1242

This signal S ₂ with a continuous waveform is fed to an oscillator 22, which uses it to generate a signal which has the same phase as the signal S ₂ . This signal is fed to the phase inverter 17, which forms a reference carrier signal S, with the phase f _Q - -ry-, from it at any point in time. This reference carrier signal Sz is fed to the demodulator 8. As a result, a color signal demodulated in a certain way can be produced by the demodulator in the sequence (E ^ - Ey), (Eg - Ey) ¹ , (E ₅ - Ey) _{+ 2} , (E _B "" ¹ V) ¹ V _{1 +} 2 " ···· be derived. This demodulated color signal is fed to the matrix circuit 18.

The extraction of the signal which is fed to the demodulator 7 as a carrier begins with the output signal of the switch 4 being fed to the burst gate 10. This output signal is the same ominance signal that is also fed to the demodulators. Assuming that it is a plus chrominance signal S, then this signal contains a burst signal B ₊ . This burst signal is separated from the rest of the signal by the burst gate 10, which is controlled by the gate pulse generator 14. Instead of the burst signal being taken from the burst gate of each row, the burst signal is. taken from the gate only every second row. This means that the burst signal always has the same phase. The generator 10 therefore does not need to set itself to an average value between different phase angles, which would be possible due to the time constant of the generator, but the generator 10 simply generates a signal that has the same phase as the burst signal. The output signal of the generator 10 is fed to the oscillator 12, which generates an output signal S- which is shifted by 45 ° with respect to the axis yr, as shown in FIG. 3A.

209817/1242

If that in Pig. 3A is used to demodulate the S chrominance signal, as shown in Pig. 3B, the resulting demodulated signal has the same axis as the S ₁ signal. However, this axis does not lie on the vertical axis, which would be correct for the red parabolic difference signal. On the other hand, the blue Parbdifferenzignal (Eg - Ey-) is correct, and if this signal! - is supplied to the matrix circuit 18 together with the output signal of the demodulator 7, and the luminance signal is also supplied to the matrix circuit via the terminal 19, the three primary color signals become EL, E _G and Eg generated.

If the switch 4 at the time of the arrival of a minus-Ghrominanzsignales p_ in the Pig. 2, the B_ burst signal is derived from the burst gate 10. This B_ burst signal causes the oscillator 12 to do so in Pig. 4A to generate signal S. If this signal is fed to the demodulator 7 and the signal S * is fed to the demodulator 8 in order to demodulate the P ^ chrominance signal, the blue Parbdifferenzsignal (E _B - Ey) is obtained correctly as before; from the demodulator 7, however, a signal is derived which runs along the axis determined by S 1. In the case of the P signal, if these demodulated signals are fed to the matrix circuit 18 together with the luminance signal, the correct primary color signals E _R , Eq and Eg are obtained.

Pig. 6 shows another embodiment of the invention similar to that disclosed in Pig. 2 is similar to the embodiment shown except that the signal switching operation occurs before the delay. The chrominance signals, which the band-pass amplifier 1 have passed are of the alternating parts of the composite TV signal separated by switch 4. The Sehalter 4

209817/1242

is in its effect a single pole changeover switch, its Output product the demodulsfcoren 7 "and 8 over two different ones Paths is fed. One of these paths is a direct path, while the other path leads via the delay circuit 2 with which the signals are for a period of time be delayed.

With the in I ¹ Xg. 6, exactly the same demodulation process can be effected as with the circuit shown in FIG. The vector diagrams shown in Fig. 3 are applicable when F chrominance signals are demodulated. The vector diagrams shown in FIG. 4 relate to the F chrominance signals.

Fig. 7 shows another embodiment of the invention in which a diode switching arrangement for separating the delayed and undelayed chrominance signals is included. That from the rest of the composite television signal Chrominance signals separated by the bandpass amplifier 1 are fed directly to one input terminal 21 of a diode switch 22 supplied. In addition, these chrominance signals are fed to a delay circuit 2. The starting product the delay circuit is fed to another input terminal 23 of the diode switch 22. Of the Switching operation of the diode holder 22 is performed by the flip-flop circuit 9 controlled, which the switchover from one switching state to the other at the end of each Line makes.

The diode switch 22 has an output terminal 24, the is connected to the input terminal of the demodulator 7. Furthermore, the diode switch has another output connection 25, which is connected to the input connection of the demodulator 8 is connected.

209817/1242

The diode switch 22 contains four diodes 26 to 29. Two of the diodes 26 and 27 are connected to one of the output terminals of the flip-flop 9 so that they become conductive at the same time. The two other diodes 28 and 29 are connected to the other output terminal of the flip-flop 9, so that these two diodes are simultaneously conductive when the diodes 26 and 27 are not conductive. The diodes are activated by the output signal of the flip-flop biased in such a way that one of the demodulators is supplied _{only with the plus signal F +} and the other of the two demodulators only with the minus signal F _-. Although the demodulator 7 is only supplied with the plus signal and the demodulator 8 only with the minus signal or vice versa, the switching state of the switch 22 depends on the signal received by the receiver.

The reference signals which are fed to the demodulators 7 and 8 so that the chrominance signals are demodulated are generated in the same way as has already been described in connection with the circuit shown in FIG. FIG. 8 shows the demodulated components of a plus-chrominance signal F ₊ which are used by using the signals S ₁ and S ₅ (FIG. 3A) as carriers for the demodulators 7 and 8; FIG. 9 shows the demodulated components of the minus -Chrominanzsignales F_, the signals S ^ and S ^ (Fig. 4) as carrier signals for the demodulators 7 and 8 are used.

Fig. 10 shows a further embodiment of the invention, when several of the components are used which are also used in the embodiment according to FIG. the The embodiment shown in Fig. 10 also includes the delay circuit 2, the switch 4 and the demodulators 7 and 8. The switch is operated again by the flip-flop 9. The input of the burst gate 10 is connected to the output terminal 6 of the switch 4

209817/1242

tied together. The output of the burst gate 10 is with the Generator 11 connected, which has an output signal with continuous Waveform generated. The input of the other burst gate 13 is connected to the output of the bandpass amplifier 1 connected. This burst gate 13 transmits the burst signals to the generator 15, which also generates a signal with a continuous waveform.

The output product of the generator 11 is the one input an adder circuit 31 via a level control circuit

30 supplied. The output product of the generator 15 is fed to the oscillator 16 via a phase inverter. In addition, the output product of the generator 15 becomes a second level control circuit 33 is supplied. The starting product the level register circuit 33 becomes the adding circuit

31 supplied. The output product of the adder circuit 31 is used to control the oscillator 12, which is connected to the demodulator 7 and this carrier signals feeds. The oscillator 16 generates the carrier signals for the other demodulator 8.

When operating the Pig. 10 are derived from the switch 4 either plus-ear dominance signals F or minus-ear dominance signals F_ and fed to both demodulators 7 and 8 and the burst gate 10. If it is currently assumed that the signals are plus-ear dominance signals P ₊ , then they contain burst signals B ₊ , which in Pig. 5 are shown. These signals pass through the burst gate 10 and control the generator 11 so that it generates a signal which has a continuous waveform and the same phase as the burst signals B ₊ . The output signal of the generator 11 is fed to the level control circuit 30, which automatically regulates the amplitude of this signal to a fixed value.

209817/1242

Yon the level control circuit 30, the signal is then with A predetermined constant amplitude of the adding circuit 31 is supplied.

The chrominance signals derived from the other burst gate 13 contain both B ₊ and B _- -KBu rst signals. As a result, the phase of the signal with a continuous waveform generated by the generator 15 is set to a mean value between the "two phases of the B ₊ and B_ burst signals. The output signal of the generator 15 is shown in Figure 5 as a vector Sg. This signal is inverted in the phase inverter 31 and used to control the oscillator 16, so that the output signal S ^ of the oscillator 16 has the same phase as the inverted signal S _2. The output signal of the oscillator 16 therefore also has that for the demodulation of the plus color difference components (E ^ - Ey) of the chrominance signal the correct phase.

The signal S .. at the output of the level control circuit 30 is in Fig. 11 shown. This signal is added to the signal S i in the adder circuit 31. The relative amplitudes these signals are chosen so that the vector sum is S ^ and in alignment with the ^ .- axis, which is the right Axis for the demodulation of the red color difference components of the F chrominance signals. The output signal of the Adding circuit 31 is supplied to oscillator 12 so that the latter generates a signal which corresponds to the phase of the oscillator 12 shown in FIG. shown signal S ^ has.

When the relationship between that of the bandpass amplifier 1 output signal and the switching state of the switch is such that the demodulators 7 and 8 and the burst gate 10 F ^ chrominance signals are supplied, it results the operation shown in Fig. 11B. Under these circumstances, the signal S1, as previously described, is passed through the oscillator 16 generated; however, those from the burst gate cause

209817/1242

2138526

Passed minus burst signals B_ that the signal generated by the oscillator has the same phase as the signal generated by the generator 11 and fed to the adding circuit 51 via the level control circuit 30. At the adding circuit 31, the signal occurs with a phase and amplitude which are reproduced by the pointer S. The vector sum of this signal with the signal S, is, given a suitable amplitude, the pointer Sg shown in FIG. 11B. This runs along the minus-Jf ₀ -AChSe. The signal Sg is thus in the correct position for the demodulation of the red color difference components and. of the ^ -hrominance signals.

As a result of this automatic generation of the signal Sj- or the signal Sg, which depends on whether the chrominance signal F ₊ or F__ is evaluated, the demodulated components shown in FIGS. 13A and 13B result. The demodulated components have the correct relative angular displacement which simplifies the matrix operation for generating the signals E ™, E ~ and E ^; however, in order to maintain this correct phase relationship, it is essential that the relative amplitudes of the signals S- and S- * on the one hand or the signals S. and S ^ on the other hand are maintained. The phase of the vector resultant representative signals S ₅ and Sg depends on the relative amplitude of the component signals which form the vector sum.

FIG. 12 shows a suitable adding circuit which can be used as circuit 31 in FIG. The collectors of the two transistors 34 and 35 are connected to a common load resistor 36. The emitter of the transistor 34 is connected to ground via a resistor 37. The emitter of transistor 35 is connected to Hasse via a resistor 38. The base terminal 39 of transistor 34 is _f with aera output of Pegelre '-; elsclialtun {5 30 vex'bunden. The base connection 4 0 des

209817/1242

Transistor 35 asfc to the output of the level control circuit 32 connected. The common collector connection of the transistors 34 and 35 is connected to the base of a transistor 41 connected. The output signal is taken from the collector terminal 42 of the transistor 41. The collector base 42 can be connected to the oscillator 12 in FIG. 10 in order to control the oscillator 12.

In the above description, the instantaneous original chrominance signal and alternatively the chrominance signal delayed by the duration of one line with respect to this used to generate a continuous selected chrominance signal. As an alternative, it is possible to to use a line of the original chrominance signal and a signal that is an odd multiple of a Line duration is delayed. The invention is also not limited only to the generation of reference carrier signals, which run along the E - Y axis and the B - Y axis. The invention is also applicable to the generation of carrier signals necessary for the demodulation of I and Q signals or similar signals are suitable.

The present invention makes the circuit particularly simple; a reduction in the quality of what is reproduced Image is not conditioned by this. Between the bandpass amplifier 1 and the demodulators 7 and 8 lie in the receiver according to the invention only the delay circuit 2 and a switch. Compared with the so-called Standard PAL decoding system, the circuit according to the invention is extremely simple. In the simplified PAL decoding system the signals emitted by the bandpass amplifier were fed directly to the demodulators. If - as shown in Fig. 14 - a phase error p ( occurs, the size of the demodulated color signals of adjacent lines varies in opposite directions, and the saturation difference between the color signals

209817/1242

adjacent lines will be so large that the quality of the reproduced image is affected. In the decoding system according to the invention, on the other hand, none occurs Difference in saturation between adjacent lines of the same signal. Besides, it's through the phase error oil between adjacent lines of different Signals caused the difference in saturation so little that the quality of the reproduced image was not is affected. This is clear from the vector diagram in]? Ig. 15 can be seen. Furthermore, with the Decoding system according to the invention alternately generates two reference signals. One of these two reference signals has the same phase as the selected burst signals which occur in those lines in which the modulation axis of the one I-color signal that has a phase. The other reference signal has a phase which is 180 ° with respect to the phase of the integrated burst signals of the successive Lines is shifted. These reference signals are generated in that first a non-delayed chrominance signal and then a line duration or an odd multiple of the line duration delayed chrominance signal is extracted. The one for demodulation The subcarrier signals used are generated by the control action of the aforementioned reference signals. Accordingly The chrominance · s signals fed to the demodulators can always be demodulated with subcarrier signals of specific phases The phases are independent of the alternating extraction of the undelayed and the delayed Signals are. Furthermore, this extraction does not have to be controlled, which further simplifies the process the circuit according to the invention is given.

209817/1242

Claims (14)

PATENT CLAIMS ij) Decoding system for a color television receiver, which is suitable for receiving composite color television signals, which consist of color sync signals (burst signals), luminance signal components and first and second chrominance signal components, the first and second chrominance signal components being modulated on a common subcarrier W have modulation axes and the color phase sequence of the first and second chrominance signal components is periodically reversed, marked d υ r ο h: A. a delay circuit part (2) for delaying the chrominance signal components by a certain amount Time j B. a holder part (4,22) for transmitting the chrominance signal components during selected time intervals, the duration of which is equal to the delay time of the delay circuit part (2), so that the delay circuit part (2) and the switch part (4,22) together form a selected continuous one Generate chrominance signal; G. a first and a second demodulator circuit part (8,7) for demodulating the selected continuous chrominance signal; D. a first and a second generator circuit part (15,11) for generating a first and a second signal, the vector of the first signal is fixed on one of the modulation axes and the vector of the second signal is in phase with au a ce selected burs I, signals coincide; 2098 17/1242 E. a control circuit part that rait the generator circuit part (15,11) for controlling the phase of the Signals connected; P. a connection circuit part which the first generator circuit part (15) with the demodulator circuit part (8) connects j such that from the first DetQodulatorehaltungsteil (8) the first ear dominance signal components can be derived; and G. a connection circuit part which the second generator circuit part (11) with the second demodulator circuit part (7) connects, such that of the second Demodulator circuit part (7) a demodulated Signal can be derived, 2. Decoding system according to claim 1, characterized in that that the control circuit part contains a viewer unit, the rait is connected to the second generator circuit part (11) and to maintain the phase of the second signal is used in such a way that the phase of the second signal with the phase of the burst signal in the selected continuous chrominance signal coincides. 3. decoding system according to claim 2, characterized in that that with the deraodulator circuit parts. (8.7) and one A matrix circuit (18) is connected to the source point for the luminance signal components, from which the Parb component signals can be derived. 4. Decoding system according to claim 1, characterized in that the control circuit part following so-holding units having: 209817/1242 A, a first burst gate (13) to which at least the Colored ear signals (brush signals) are supplied} and B. a pulse generator (14) for generating gate pulses, which are fed to the first burst gate (13), so that the burst gate receives the burst signals durchläset and the first generator part (15) feeds, 5. Decoding system according to claim 4, characterized in that the first generator holding part (15) has a time constant for averaging the phase of the burst signals supplied to it, whereby the first generator circuit part (15) generates the first signal with a phase, those in the middle between the phases of the successive burst signals supplied by the burst gate (13) lies, 6, decoding system according to claim 5, characterized in that the first generator circuit part (15) the following Holding units has: A. a generator (15) that generates a signal with continuous Waveform generated and connected to the first burst gate (13) so that it duroh the of the first burst gate (13) supplied burst signals is controlled? B. a first oscillator (16) connected to the first generator (15) is connected so that the first oscillator (16) is controlled by the first generator (15), wherein the first generator (15) and the first oscillator (16) oscillate the frequency of the burst signal and generate a phase which is 180 ° with respect to one of the two modulations is shifted; and 209817/1243 2138828 C. a phase inverter (17), which with the first Oscillator (16) is connected and inverted the oscillations to generate the first signal. 7. Decoding system according to claim 4, characterized in that a second burst gate (10) is provided, the the selected continuous aural dominance signal is supplied is, and that the second burst gate (10) is connected to the gate pulse generator (14), so that it is controlled by the gate pulses in such a way that it carries the burst signals from the selected continuous Ohrominanzsignal transmits to the second generator circuit part (11). 8. decoding system according to claim 7, characterized in that A. The delay circuit part (2) contains it (1) an input terminal that connects to a source for the ear dominance signal components is connected, and (2) an output terminal} and B. dal the circuit part (4) contains ι (1) a first and a second input terminal (3, 4) and (2) an output terminal (6), the first input terminal (3) is connected to the source of the chrominance signal components, the second input port (5) being connected to the output port of the delay hold-up part (2) is, and where the output terminal (6) 209817/1242 of the switch part (4) with "two demodulator circuit parts (8,7) and the second Burat gate (10) is connected, so that these circuit units the selected continuous Chrominanza signal is supplied. (Fig. 1, 10) 9. Dekodiersyatem according to claim 7, characterized in that that A. the switch part (4) contains: (1) an input connector (3) connected to a source for the chrominance signal components, and (2) an output terminal (6); and that B. includes the retardation component (2); (1) an input terminal which is connected to the output terminal (6) of the holder part (2) is and ) (2) an output port that connects to the demodulators (8,7) and the second burst gate (10) connected is, so that these holding units the delayed Repetitions of the chrominance components are supplied during the corresponding time periods will. (Fig. 6) 10. decoding system according to claim 11, characterized in that A. the delay circuit part (2) contains: 209817/1242 2138820 (1) an input terminal connected to a source for the ear dominance signal components are connected, and (2) an output terminal} and that B. the switch part (22) contains: (1) a first input terminal (21) connected to the source of the chrominance signal components is, (2) a second input connector (23) with the The output terminal of the delay hold-up part (2) is connected, (3) a first output terminal (24) connected to the first demodulator circuit part (7) and the second Burst gate (10) is connected, so that these circuit units the selected continuous Chrominance signal is supplied, and (4) a second output terminal (25) which is connected to the second demodulator circuit part (8) is connected, so that these so-holding units of the selected continuous chrominance signal is supplied. (Big. 7) 11. Decoding system according to Claim 1, characterized in that the connecting circuit part between the second Generator circuit part (15) and the second demodulator circuit part (7) an adder circuit (31), which with the first generator circuit part (15) and the second generator circuit part (11) is connected, so that the two so-holding parts (15, 11) emitted signals vectorially to an output signal 209817/1242 are added whose phase corresponds to the other of the two quadrature phase modulation axes. (Fig. 10) 12. Decoding system according to claim 11, characterized in that that further a signal level control circuit part (30,32). eggs is provided, which the relative level / the adding circuit (31) applied signals to determine the Controls the output phase of the yector sum of these signals. (Fig. 10) 13. Decoding system according to claim 12, characterized in that ^ that the signal level control circuit part following holding units contains: A. a first automatic level control circuit (33) which is connected between the first generator circuit part (15) and the adder (31)} and B. a second automatic level regulation maintenance (30), the between the second generator holding part (11) and the adding circuit (31) is connected. (Fig. 10) 14. Decoding system according to claim 13, characterized in that an oscillator (12) is further provided with k the adding circuit (31) is connected so that it is controlled by the adding circuit (31) and oscillations generated which has the same phase as the output signal the adding circuit (31), and that the oscillator (12) is connected to the second demodulator circuit part (7) and feeds a reference carrier signal to it, whose phase corresponds to the other of the two quadrature phase modulation axes. The patent attorney 209817/1242