DE2156290B2 - Television receiver circuit for decoding a PAL color television signal - Google Patents

Description

3 V 4

Delay line is connected. Since with these two vectors the resulting chrominance

SECAM system the color difference signals (RY) and signal F _n , ie a complex voltage that is in

(BY) transmitted in consecutive lines of the form

appear at one exit of the double / £ - E) + / (E _R - Ey) _n

Switch successively the (R- Y) signal 5 ^BY "

of the first line, the delayed (R- Y) signal that lets you write.

first line etc. and at the other output of the Dop- F i g. 1 also shows the phase relationship for the

pelumschalters the (B- Y) signal of the second line, following line η + 1. The chrominance component E _B - E _Y

the delayed (B-Y) signal of the second line etc. is also on the carrier with the modulation

In the PAL decoding circuit _{according to} the invention io fa * _modulated . _{The Fa} rbartkom-

On the other hand, they appear at the outputs ° 2

of the double switch the component E _R —E _Y still to be demodulated is on the other hand on the carrier

Chrominance signals. Since here the one output of a modulation axis of the phase Φ _ο - π, ie - Φ _ο ,

the demodulator connected to the double changeover switch is modulated, d. H. opposite to the phase of the

only the chrominance signals of the first, third, etc. line 15 of the preceding line n. The resulting chrominance signal

and to those with the other out F _{n + 1} is given by the expression

transition of the double switch connected demodula- / p _ ρ \ - '(F - E}

tor only the chrominance signals of the second, fourth, etc. \ ^b B ~ ^ y) _n + 1 H R yJn + i

Line, the two demodulators can be played.

are supplied with color carrier oscillations, which ao The chrominance signal contains a color synchronous signal

a constant mutual phase shift to- B + or B-. As shown in Fig. 2, the color syn-

point. Due to the elimination of the line-frequency chroning signal B + in the signal F _n by 45 ° compared to the

switching of the color phase required for demodulation Φ _ο before, while the color sync signal B -

carrier vibrations, the structure of the signal F _{n + 1} is simplified by 45 ° compared to the phase - Φ _ο

Decoding circuit essential. The appearance of a 35 lags behind.

Phase distortion of the chrominance signals successively F i g. 3 shows an embodiment of the winning Lines also has in the circuit according to the invention. Through a band filter circuit (as will be explained in detail below) only amplifier 1 is the chrominance signal from the color one negligibly small change in saturation image signal separately. The chrominance signal arrives at Consequence, so that there are no image interferences 30 on the one hand directly to the one input 3 of a dop, pel switch 2 and on the other hand via a delay

Some embodiments of the invention are in branch line 5 to the other input 4 of this double

illustrated in the drawing. It show pelum switch 2. The delay line 5 delayed

F i g. 1 and 2 vector diagrams to explain the chrominance signal by one line duration,

of a PAL color television signal, 35 A flip-flop 6 is provided by the (not shown)

F i g. 3 actuates the block diagram of an embodiment line deflection circuit and switches the toggle

game of the circuit according to the invention, switch 2 with line frequency. The diodes 11 and

F i g. 4 to 6 vector diagrams for explanation 12 are, for example, in the first, third,

the function of the circuit according to FIG. 3, fifth, etc. line conductive, in which, for example, the

F i g. 7 shows the block diagram of a second embodiment 40 demodulation axis for the red color difference signal

r'ngsbeispieles the circuit according to the invention, which has phase Φ _ο , while the diodes 13 and 14

F i g. 8 and 9 vector diagrams for explanation during the second, fourth, sixth, etc. lines

the function of the circuit according to FIG. 7. are conductive, where the modulation axis for the

The essence of the PAL color television system consists in the red color difference _{signal which has the phases - Φ ο} , the phase relationship between the two color differences repetition modulated with a carrier to form a chrominance signal - signals of the first, third, fifth are. This phase relationship is shown in Fig. 1 line, so ... F _n , F _n , F _{n + 2} , F _{n + 2} , F _{n + 4} , F _{n + 4} ... Am represents. One of the chrominance components, E _B -E _Y , the other output 9 occurs against it - each also contains information about the blue components 50 because with repetition - only signals of the second, of the image, the other component, E _R - E _Y , a fourth, sixth, etc. row, ie ... F _n-1 , F _n-1 , information regarding the red components. The F _{n + 1} , F _{n + 1} , F _{n + 3} , F _{n + 3} .

Modulation of these two chrominance components The output 7 of the double switch 2 is with

follows on the same subcarrier, but separately with a demodulator 8 and the output 9 with a

changes and such that during a certain time 55 demodulator 10 is connected.

Interval, corresponding to a line η of the image, the output 7 of the double switch 2 is also

Chroma component E _R - E _{Y connected} to the carrier with a gate circuit 15, which consists of the

a modulation axis of phase Φ _{ο is} modulated. their supplied chrominance signal F _n the contained therein

During the same time interval, the other burst B + wins. The gate circuit

Chroma component E _B -E _Y on the carrier with 60 15 is provided by a signal source 16 for this purpose

a modulation axis of phase Φ, = ⁿ - modulated. fed and controls an oscillator 17, 18 of the

⁰ 2 a color carrier oscillation (with the

The chrominance component (E _B - Ey) _n , which supplies the blue phase B +), the information supplied to the demodulator 8 during the predetermined line inter-. Furthermore, the output signal of the oscillatory ball η is reproduced, that is, as a horizontal vector 65 gate 17, 18 via a phase reversal circuit 19 and the chrominance component (E _R - E _Y ) _n , which carries the red. The color information phase shifted in this way during the same line interval η carrier oscillation is returned to the demodulator 10 as a vertical vector. An addition that directs.

5 6

The from the oscillator 17, 18 to the demodulator 8 to B - Y _ _{0 0}

guided color carrier oscillation S ₁ (see. Fig. 4A) "T ^ ₃ ^ cos 45 + y cos 45.
therefore leads by 45 ° in relation to the axis Φ _ο . the

the demodulator 10 supplied color carrier frequency This results

supply is S ₂ with respect to the color carrier wave S ₁ 5 tf - Y = 1.14 cos 45 ° (P + Q) = 0.81 (P + Q)
180 ° out of phase. In the demodulator 8 _ _ _o . , Dv _{-1 A} <- _(n , "-,
thus the chrominance signal F + (the first, third, five- ^{ö r} ~ ^Z ' ^{UJ cos 4D} ^ ⁺ "' ~ ^{i>4;> 1} ^ ^{+ Π} '
th, etc. line) through the color carrier oscillation Sj One can thus obtain the signs RY and BY with a phase leading by 45 ° compared to Φ _ο by demodulating the output signals P. In the demodulator 10 the chrominance and Q are fed to a matrix circuit which satisfies the two signal F— (the second, fourth, sixth, etc. line) last-mentioned equations,
by the signal S ₀ with an opposite to the axis The exemplary embodiment in FIG. 7 corresponds to _π ' ,,. , largely - especially as far as the same reference Φ _ο -2 demodulates by 45 ° lagging phase (Vg _{1. zdchen are twisted} _ _the circuit according to

Fig. 4B). is Fig. 3. The output of the bandpass filter amplifier 1 is

Are reversed (in a different way of working here via one of the flip-flop 6 with line frequency

Double changeover switch 2) the demodulators 8 and 10 controlled switch 21 with the gate circuit 15

from the outputs 7 and 9 the chrominance signals of the bound. This switch 21 leaves the chrominance signal

second, fourth, sixth, etc. or the first, third - in each case then (in the circuit shown in FIG. 7)

th, fifth line fed, the gate switch ao position) wins through to gate circuit 15, if on

device 15 the color sync signal B - the chrominance output 7 the chrominance signals of the first, third,

signals of the second, fourth, sixth, etc. line. The fifth, etc. line (and accordingly at output 9 the

Oscillator 17, 18 then generates a chrominance signal of the second, fourth, sixth, etc.

generation S ₃ (see Fig. 5 A), the same phase as the line) appear. The gate circuit 15 wins

Color sync signal B -, ie at 45 ° opposite that in the chrominance signals of the first,

over the axis - Φ _ο lags. This color carrier - third, fifth, etc. line containing color synchronous

oscillation S ₃ is fed to the demodulator 8, signal B +, so that the oscillator 17, 18 has a color

while a color carrier oscillation of the corresponding phase is generated for the demodulator 10. at

movement S ₄ arrives, the phase of which is 180 ° compared to that of a reversed function of the double changeover switch 2

is replaced by S ₃ /. As a result, the de- 30 (in which at output 7 the chrominance signals of the two

modulator 8 supplied chrominance signal F— (signal of the th, fourth, sixth, etc. line appear) lets the

second, fourth, sixth, etc. line) through the color switch 21 the chrominance signals of the second, fourth,

carrier oscillation S _{3 is} demodulated and the line to the gate circuit 15 passes through to the sixth, etc.

modulator 10 supplied chrominance signal F + (signal that generates the color sync signal contained therein

the first, third, fifth line) by the signal S ₄ 35 B- wins.

(see Fig. 5B). One can therefore use the demodula- In both exemplary embodiments explained gates 8 and 10 demodulated chrominance signals independently, the demodulation is also carried out in this way from the switching status of the double changeover switch 2 that the demodulation axes correspond to the dashed take, i.e., even if the switching function correspond to lines in Figs. 4B and 5B. To this of the flip-flop 6 is reversed. The starting 40 purpose is carried out in the embodiment of FIG signals from demodulators 8 and 10 are shown in FIG. 3 the chrominance signal from output 9 of the double matrix circuit 20 supplied, where from these signals toggle switch 2 of the gate circuit 15 to; in the and a luminance signal Y, the color signals formation according to FIG. 7, switch 21 is operated will. opposite to the mode of operation described above.

In the described embodiment of FIG. 45, the above description has been made for the case that

circuit according to the invention are thus the the original chrominance signal and the one line

Demodulators 8 and 10 supplied chrominance signals permanently delayed chrominance signals alternately on the sel-

do not appear with axis Φ _ο , ie with axis RY, ben output of the double changeover switch. Instead of

,. , _A , _Λ -τ j u _{t A} α v, _{c <x} π γ of which it is of course also possible to am

and mrt the axis Φ _ο - ^ - ie with the axisi? -] _{5o se} , _{ben output alternately the original} ° _chromaticity .

demodulated - as usual - but with a signal and an axis with an odd number multiple to take off the signal delayed in phase or in phase opposition to a line duration.
The color sync signal is available. The output signals of the From the F i g. 8 and 9 is finally still to er-Demodulators 8 and 10 are accordingly not as seen, as is usual when a phase distortion α occurs, demodulated red and blue color difference 55 the saturation difference in the signals according to the invention (RY) or (BY). However, they can be decoding (FIG. 9) much smaller than in the case of the PAL decoder (FIG. 8) which is customary by using a simple matrix circuit. In the PAL decoder, which is borrowed from the usual signals (R - Y) or (BY), the phase shapes change with one. If the output signals of the distortion α and the amplitudes of the demodulated simodulators 8 and 10 are referred to as P and Q, then 60 signals F _n and F _{n + 1 can be seen} in the opposite direction, which can be seen from FIG. 6 the following relationships can easily lead to considerable image disturbance. Derive at: the decoding circuit according to the invention (FIG. 9)

occurs, however, through the other phase position of the de-

^R ~ = ρ cos 45 ° + Q cos 45 ° modulation axes only a negligibly small one

1.14 65 change in amplitude.

For this purpose i sheet of drawings

Claims (4)

modulators with mutually phase-shifted claims: color carrier vibrations supplied, furthermore with a line-frequency controlled electronic double 1. Color television receiver circuit for deco switch, which is connected to the input and output on the input side a PAL color television signal with a 5 gang of the delay line connected and p.us line delay line, two demodulators, connected on the output side to the demodulators, one controlled by the color sync signal and, during a first line, the chrominance color carrier oscillator, which the two demodula signal undelayed and during the following two ports with mutually phase-shifted th line again the delayed chrominance signal of Color carrier vibrations supplied, also supplies with io first line. a line frequency controlled electronic With the usual color television receiver circuits Double changeover switch, which is connected on the input side to the inputs for decoding a PAL color television signal and output of the delay line (cf. for example German Patent 1286 084) are closed and on the output side is connected to the modulators of the chrominance signals of all lines in each case to two demolators and fed during a first 15 dulators. For demodulation, the line must each have the chrominance signal without delay and the phase position of the color carrier oscillation fed to the (R- Y) demodulator during the following second line must be reversed by 180 ° in successive lines. To diefert, characterized in that this purpose is the color carrier oscillator, which feeds the two outputs (7, 9) of the double switch (2) ao (B - Y) demodulator with a fixed phase position, each with one of the two demodulators (8, 10) a line frequency controlled switch are connected downstream, whereby at one output (ζ. B. 7) the phase of the (R - Y) demodulator successive the chrominance signal of the first led color carrier oscillation with line frequency by line, the delayed chrominance signal of the first 180 ° reverses. Line, the chrominance signal of the third line, the * 5 This line-frequency switching of the phase of the If the chrominance signal of the third line etc. hesitated to the color carrier signal fed to a demodulator, while at the other output (ζ. B. 9) oscillation becomes consecutive with the object of the older one the chrominance signal of the second message P 20 64 153.6 is avoided in that only line, the delayed chrominance signal of the second, the chrominance signals of every second line are used. the chrominance signal of the fourth line, the 30 den, by alternately each time an original color delayed Chroma signal of the fourth line, etc. artsignal and then one by one line duration occur that further a gate circuit (15) delayed repetition of this chrominance signal appeared is that which is used from one of the outputs. The two demodulators can go into each other (7, 9) of the double changeover switch (2) in front of the hand in this case are supplied with color carrier vibrations Chrominance signals or from one of the before the 35 den that a constant phase shift Delay line (5) present chrominance against each other. signals the color sync signal contained therein The invention is based on the object wins, and that by this color synchronizing a color television receiver circuit of the above signal-controlled color carrier oscillator (17, 18) of the type described so that the last two Demodulators (8, 10) with the constant 40 mentioned requirement is met, d. H. a special one Simple supply of the two demodulators phase-shifted by 180 ° with respect to one another Color carrier vibrations supplied. the necessary color carrier vibrations is achieved. 2. Color television receiver circuit according to this object is claimed according to the invention 1, characterized in that the gate releases that the two outputs of the double switch circuit (15) directly connected to an output 45 each with one of the two demodulators (z. B. 7) of the double changeover switch (2) are connected, with one output successively is. the chrominance signal of the first line, the delayed 3. Color television receiver circuit according to the chrominance signal of the first line, the chrominance signal of the Claim 1, characterized in that the third line, the delayed chrominance signal of the third circuit (15) via a line frequency controlled 50 line etc. appear while at the other output th switch (21) to the input of the delay successively the chrominance signal of the second line (5) is connected. Line, the delayed chrominance signal of the second line, 4. Color television receiver circuit according to the chrominance signal of the fourth line, the delayed Claim 1, characterized in that the off chrominance signal of the fourth line, etc. occur that Gang of the color subcarrier oscillator (17, 18) with the 55 also a gate circuit is provided, which consists of a a demodulator (8) directly and with the one in front of the other at the outputs of the double changeover switch Demodulator (10) via a phase-encompassing chrominance signals or from one of the before the reversing circuit (19) is connected. Delay line existing chrominance signals color sync signal contained therein wins, and ⁶ ° that the controlled by this color sync signal Color carrier oscillator with the two demodulators consistently phase-shifted by 180 ° Color carrier vibrations supplied. The invention relates to a color television receiver with color television receiver circuits for de- : Attitude towards the decoding of a PAL color television 65 encoding of a SECAM color television signal is beginning with a line delay line, two already the use of a double switch belemodulatoren, one knows about the color sync signal (cf. French patent specification 1 511 098), the s controlled color subcarrier oscillator, which connects the two input sides to the input and output of one