DE2254570B2 - CIRCUIT FOR DECODING THE COLOR SIGNAL IN A PAL COLOR TELEVISION RECEIVER - Google Patents

Description

(The modulation axis forms the parallel phase position and the reference color carrier. The

sine further, also via an upstream gate second APC chain from a phase discriminator 7,

stage controlled device, consisting of a reactance stage 8 and a feedback

Voistufe and a downstream, one of line generator 9. The generated by the two ÄPC chains

7u line cause alternating phase shift - 5 generated reference color carriers are assigned to the second de-

the switching stage, from the color sync signal and modulator 14 via an adder 10, a switch

the output signal of the generator stage is fed to the switching stage 11 and a phase rotation stage 12

other modulation axis parallel and from line leads.

to line by 180 ° phase alternating second loading The received PAL color television signal is formed by Zugsfarbträger, is characterized according to the invention by the image intensifier, not shown, a bandpass filter that the amplifier 1 connected upstream of the preliminary stage is supplied, and the chrominance signal A is a second gate stage from a control circuit (Fig. 3) is fed to the two gate stages 2, 6, which is the main line frequency-controlled gate stage and also the line sync signal B (Fig. 3) which blends the preliminary stage from the delay stage 16 and the pulse shaping stage for every second line Color sync signal and the output 15 17 supplied, so that the time duration At versginal of the first generator stage a continuous shifted signal C (Fig. 3) forms by a bistable phase constant reference color carrier signal, the multivibrator formed switching stage 18 is fed to sen phase one of the modulation axes becomes parallel. So, unlike the known one, and that the downstream switching stage, operated synchronously with the circuit, as a control signal for the switching stage 18 second gate stage, a phase 20 is not the color sync signal, but the time reversal of the phase reversal supplied by the pre-stage. shifted line sync signal used.
constant reference color carrier signal for every second line supplied to the switching stage 18 as a control signal. carried out impulses according to the impulse series C

Preferred embodiments of the invention act in the output circuit of the switching stage 18

the subject matter of claims 2 and 3. 25 square-wave signals G (Fig. 3). The differentiating

Further details of the invention result from stage 19 generates differentiated pulses H, the

from the description of preferred embodiments of the Schmitt trigger stage 20 are supplied. These

of the invention in connection with the drawing supplies due to the control by the different-

gen. It shows adorned pulses H output pulses / (Fig. 3), the

F i g. 1 shows the block diagram of a first invention- 30 have a period of 2 H alternating lines,

according to demodulator circuit, the gate stage 2 receives the control

F i g. 2 is a vector diagram to explain the pulses C and fades in successive

Circuit according to FIG. 1, lines (line period H) a color sync signal.

Fig. 3 shows the temporal relations of the faded out color sync signal of the goal

Figure 2, which explains the various signals occurring, is shown in line D in FIG. 3,

position, on the other hand the gate step receives 6 gate impulses / from

F i g. 4 shows the block diagram of a second output from the Schmitt trigger stage 20 and fades out a color guide of the invention, synchronous signal with double the pulse spacing 2 H

F i g. 5 the associated vector diagram. The pulses E and F (Fig. 3) pass through

F i g. 6 a phase discriminator with integra 40 the gate stage 6 faded out pulses again. If

tion stage for use in the invention, the gate stage 6, the color sync signal E or the

F i g. 7 A and 7 B for F i g. 6 relevant vector burst signal F supplies depends on under

diagrams and what conditions the switching stage 18 is currently in

F i g. 8 a provided in the invention is operated.

Phase turning circle. 45 The faded out burst signal D becomes

The circuits explained below are supplied to the first APC chain 1, which is provided by the

currently as particularly favorable versions of the phase discriminator 3, the reactance level 4 and the

Invention viewed. It should be emphasized, however, that reference color carrier generator 5 is formed, and as

that these explanations meet the general invention output signal, the two reference color

Do not restrict thought ideas, they serve much more sluggishly 50 / _So , f _So with a phase difference of 90 °

more just to explain the invention. against each other for demodulation with respect to

F i g. 1 is the block diagram of a circuit showing the demodulation axes [BY) and (RY).

according to the invention, which serves the purpose that leads in, as will be explained,

the composite PAL color television signal is similar to the other faded out color

hold chrominance signal to demodulate. This switching 55 sync signal E or F of the second APC chain 2

device has two automatic phase control APC supplied, which the second reference color carrier f _B.

Chains 3, 4, 5 or 7, 8, 9 and a control switch or f ' _Bi supplies, both of which are in phase by 90 °

device and two demodulators 13, 14. 15 is lagging behind the color sync signal / _ß , or f _{B 2} .

Generation of the color difference signals provided when the generator 9 uses the second reference color

Matrix circuit. The control circuit consists of όο carrier f ' _Bi supplies and at the same time the first reference

a delay stage 16, a pulse shaping color carrier f _{s 0} and the second reference color carrier f ' _B

stage 17, a switching stage 18, a differentiating the adding stage 10 in the relative ratio:

stage 19, a Schmitt trigger stage 20 and two Tor- Yl \} ' _{s 0} 1 = I f'e 11 are fed, so the result has

stages 2, 6. animal reference color carrier / ' _s j a phase that begins with de

The first APC chain to which the output signal of the 65 demodulation axis (BY) coincides. If there

first gate stage 2 is supplied, consists of a against the generator 9 the second reference color

Phase discriminator 3, a reactance stage 4 and carrier f ' _{B 2} and supplies the two reference color slices

a feedback oscillator for generating / ' _fl2 , f _So in the same way the adder 10 trains

leads, then the adder 10 delivers the pulses G of the switching stage 16 is activated, instead

Reference color carrier f _{s 2} , the phase of which with the De- of a switch that switches over the chrominance signal,

modulation axis - (B- Y) coincides. Fig. 4 shows a second preferred embodiment

The circuit according to the invention formed by vibrational composition. Only reference color carrier f ' _{s t} is used for the following reference 5 an APC chain 3 to 5. The synchromesh color carrier switchover stage 11 is supplied, and the chronsignal D is taken from the gate stage 2 and the reference color carrier / ' _st is fed to this unchanged to the APC stage, which takes the phase when the square pulse G of the switching discriminator 3, the reactance stage 4 and stage 18 is positive at time t _t , while it is formed as a loading oscillator 5 and generates a first reference color path color _{carrier y s 2} with reversed phase position ent io carrier f _s , which takes a phase delayed by 90 ° when the Square pulse G to is negative with respect to the resulting phase of the two at time f _2. Even if the composite has color sync signals j _{B v} j _{B 2} . setting reference color carrier formed f 'is supplied _{s 2} of the reference This first reference color carrier / _s, of the oscillator 5 color subcarrier switching circuit 11, is generated, is in phase in the direction of your Similarly, f two reference color carrier' _sv f _S2 15 modulation axis (RY ) (see Fig. 5). The supply with alternating phase position in the succession of the first reference color carrier / _s to the 90 ° -following lines is generated. Phase rotation stage 21 generates a second reference

The resulting reference color carriers f ' _sv f' _{s 2} color carriers / _{s 0} for the demodulation axis (BY). Since the phase rotation stage 12 is fed, which causes a part of the output signal of the oscillator 5 to the phase lead of 90 °, so that the third 20 phase discriminator 3 via the feedback ^ reference color carrier / _s j on the + (i? -Y) axis and is fed to the loop of the APC chain, the third reference color carrier / _{s 2} on the - (i? -Y) axis will be supplied upright in the _{correct phase of the reference color carrier / s.} In this way, correspondence is obtained. The gate stage 6 fades out with the double accordingly the switching of the color sync signals line duration 2 H color sync signals. The third reference color carrier is formed, which define the demodulation 25 dazzled color sync signal E and the reference axis + (RY) . Meanwhile, the color carrier / _{s of} the oscillator S are simultaneously the chrominance signal is fed through the bandpass filter 1 to a phase discriminator 22,
fed to the (BY) demodulator 13, whose loading F i g. 6 shows an embodiment of the phase _{discrete signal which is the fixed reference color carrier frequency / s 0} , minators 22, connected to a subsequent and the (.RY) demodulator 14 are used as a reference 30 integration stage. The color sync signal / _{ß t} is signals the reference color carrier / _{s 1} and f _{s 2} supplied, through the gate stage 6 of the primary winding L ₁ of the phases offset by 180 ° while on- transformer T _{1 is} supplied. The colors of successive lines are synchronized. The demodulation signals f _Bv - / _ßl , which are shown as vectors, lators 13, 14 therefore supply the color difference signals are induced _{in the secondary winding L 2.} There S (BY), S (RY), which are supplied to the matrix circuit 35, can also on the other hand become the reference color carrier / _s and there in the blue signals corresponding to the red, green and oscillator 5 of the primary winding L ₁ , where the reference color carrier / _s in Fig. 7 A can be converted as S (RY), S (GY) and S (BY) . Vector is shown. The voltage V ₁ ati of the phase

The circuit for the chrominance signal can be designed so _{that the external discriminator diode D 1} corresponds to the voltage that the polarity of the chrominance signal 4 ° vector sum (Zb ₁ + ^) 'while the voltage V _{s is} reversed for one line and the demodulation at the second phase discriminator diode D. ₂ dei using the reference color carrier / _{s v} f _Sz er corresponds to the vector sum [/ _ßl + (- f _s )]. It can be seen that instead of the fact that the output signal is provided with a DC voltage switching stage 11, instead of the reference color carrier. Such a possible signal Δ E is formed at the connection of the resistance is not shown in FIG. 1, but it is shown in 45 states R ₁ , R ₃ , the integration circuit 23 being discussed with reference to the circuit shown. the capacitances C ₃ , C ₄ and the resistance R ₃

Then the chrominance signal of the bandpass is formed. The DC voltage Δ E is positive, d £

Amplifier 1 to the (BY) demodulator 13 and a \ V _X > j K ₂ ! is. When the color sync signal f _B "dei

not shown switching stage supplied. The right primary winding L _{1 of} the transformer T ₁ supplied

corner pulse G from the switching stage 18 becomes that for 50, the DC voltage component Δ Ε ir

the phase reversal of the chrominance signal provided by the integration stage 23 is negative because for the span

Switching stage supplied so that the chrominance signal voltages V ₁ and V ₂ to the Phasendiskriminatordiodei

by 180 ° during the one line period for D ₁ , D ₂ according to Fig. 7B:
Entering the (i? -Y) demodulator 14 in reverse

will. 55 IV ₁ ] <\ V _S \.

At the same time, the reference color carrier / _So des

Oscillator 5 to the (B-Y) demodulator 13 for delivery. In this way, the reference color carrier /,

tion of the color difference signal S (BY) supplied. That of the oscillator 5 and the DC voltage comoo

Reference color carrier / ' _Sl or f _S2 is one component of the integration stage 23 of the phase shift

Phase shifting by 90 ° causing phase stage 24 is supplied, and thereby a third

rotary stage 12 supplied so that the color difference reference color carrier / _s j or f _Sz formed whose phase

signal S (RY) is on the demodulation axis (RY) when the composite axis is supplied . The third

th reference color carrier / sj, / _S z ^{of the} phase rotation reference color carrier / _st or / _{S2 also} corresponds

stage 12 to the (Ä-Y> demodulator 14 formed line K in Fig. 3.

will. 65 According to Fig. 8 consists of phase shifter stage 2-

The same result can be achieved if one of the transistors Q ₁ , Q ₂ , Q ₃ . If the reference

a push-pull demodulator, connected to a color carrier / _{s of} the primary winding L _{1 of} a transformer

Integration part, used, which is fed by the rectangle mators T ₃ , the reference color occurs

sluggish / c at the collector of transistor Q ₃ and the phase-inverted voltage at the base electrode. The reference color carrier / _{s of} the collector is fed to the interconnected emitters of the pair of transistors Q ₁ , Q _2.

The two transistors Q 1, Q _{2 are arranged so that the transistor Q 1 is switched on and the transistor Q 1} is switched off when a positive voltage AE is fed to the integration stage 23 of the base electrode of the transistor Q 1. In this way, the third reference color carrier f _{sx will appear} with the same phase as the first reference color carrier / _s on the secondary winding L _{2 of} a transformer T _x which connects the two collectors of the transistors Q ₁ , Q ₂ . If the two transistors Q ₁ , Q ₂ are connected in such a way that the first transistor Q _{1 is} blocked and the second transistor Q _{2 is} energized when a negative DC voltage signal - Δ Ε is fed to the transistor Q ₁ , the third reference color carrier / _{S2 is produced} with the phase inverted with respect to the reference color carrier / _s on the secondary winding L _{2 of} the transformer T ₄ .

In Fig. 4, the third reference color carrier corresponding to line K and the rectangular pulses G (FIG. 3) are fed to the switching stage 25, which alternately delivers the fourth reference color carrier Is ρ / s >> fsv ■ ■ ■ , from line to line each of the fourth Reference color carrier is inverted in phase by 180 °.

At the same time, the chrominance signal is supplied from the bandpass amplifier 1 to the (BY) demodulator 13 and to the (RY) demodulator 14. The (BY) demodulator 13 effects the (BY) demodulation according to the second reference color carrier / _So and thereby generates the color difference signal 5 (BY), while the (RY) demodulator 14 performs the (/? - Y) demodulation using the third reference color carrier / _{s v} f $ ₂ , fs _v ■ · · each effected for a line duration and the color difference signal S (RY) is generated. The two color difference signals are then converted in the matrix circuit 15 into the three color difference signals S (BY), S (GY) and S (RY) .

In the circuit according to the invention, the switching means are simple and inexpensive, since the line synchronization signal is used to control the bistable multivibrator. The time constant of the automatic phase locked loops APC can be selected so that the reference color carrier L (FIG. 3) is correctly generated even if the bistable multivibrator is randomly reversed by an interference signal.

For this purpose 4 sheets of drawings

Claims (4)

5. Decoding circuit according to claim 4, characterized in that the multi-vibrator (18) the gate stage (6) via a differentiating element (19) 1.Circuit for decoding the color signal and a Schmitt trigger (20) controls, in a PAL color television receiver, in which 5 6. decoding circuit according to claim 4 or 5, a first as a stabilized generator stage characterized in that the control input formed device with upstream gate stage of the switching stage (11; 25) with the output of the from the received multivibrator (18) bistable in the phase of line. to the line by 90 ° alternating color sync signal a first reference color carrier with kon- io constant phase position, parallel to a first modulation axis, and another, likewise The invention relates to a circuit for controlled via an upstream gate stage Device consisting of a preliminary stage and decoding of the chrominance signal in a PAL color one downstream, one from row to row 15 television receivers. causing alternating phase shift In the PAL color television process, the color Switching stage, from the color sync signal and artsignal as a phase-modulated signal in such a way to transmit the output signal of the generator stage that the phase of the color subcarrier is reversed parallel to the line of the other modulation axis and alternating to line. In the color distance from line to line by 180 ° phase alternating ao visual receiver is then for demodulation forms a reference second reference color carrier, which means that the phase is reversed, which indicates that the phase of the preliminary stage (7 to every second line is fed to the demodulator OK; 22 to 24) upstream second gate stage (6), this reference color carrier must have a phase change from a control circuit (16 to 20) which corresponds to the phase change of the half line frequency controlled gate stage 25 transmitted color carrier signal. This and the precursor (7 to 10; 22 to 24) from the reference color carrier a local generator in the television receiver of hidden for every other line Farbsyn- generated, the phasenmäßi "chronsignal (f _Bl or j _Bz) and the output with respect to two color sync signals is controlled, signal (f _so ; / _s ) of the first generator stage (3 to 5) which alternates from line to line on a phase of a continuous, phase-constant reference position of + 45 or ^{-45 C} with respect to the mode color carrier signal (f _Sl or / '_S2; / _Sl or f _S2 ) lation axis are reversed, forms whose phase to one of the modulation in general is parallel to the reference genes [(RY), (BY)] , and that the rator In accordance with the color sync signals, downstream switching stage (11; 25) operated synchronously with the second gate and discriminator using a timing stage (6) regulate a constant element with a correspondingly low timing phase reversal of the from the preliminary stage (7th until 10; constant a synchronization voltage for switching 22 to 24) supplied phase constant reference of the reference color carrier of the demodulation stage color carrier signal (f _s ! or f _{s 2} ; / _Sl or / _S2 ) derived for the supplying switch. Such causes every other line. However, circuit has the disadvantage that as a result of 2. Decoding circuit according to claim 1, da- 40 interference signals and noise signals of the discriminatoi characterized in that the preliminary stage tends to work incorrectly _{by 2U.} The faulty one as an APC loop (7 to 9) designed second mode of operation of the discriminator leads to a disturbance generator stage and an adder stage (10) formed tion of the switching rhythm for switching the is and that in the adder stage (10) the reference color carrier provided switch and dagangssignal (f _Bl or f _SS2) of the second generation ₄₅ with _a deterioration of image quality on the gate stage (7 to 9) and the output signal (f _So) screen of the television receiver, the first generator stage (3 to 5) in the Amplitude has already been used in various ways the ratio j / 2: 1 vectorially added, lines are developed that reflect the general disturbances (Fig. I) - should be avoided, e.g. in such a way that the 3. Decoding circuit according to claim 1, characterized in that the 50 line of the synchronization signals for the phase is indicated in that the preliminary stage by a switch from one of the phase control stage of the phase discriminator stage (22), the unabder generator stage (3 to 5) generated by the generator of the reference color carrier generating the reference - pending stage takes place. Such a circuit is color subcarrier (/ _s ) and "on the one which is described by the second, _e.g. in DT-PS 12 86 084, with the color sync signal 55 which is passed through the gate stage (6) and which is controlled by the phase-controlled oscillator, a connected to it Integral carrier vibrations and the inverter stages controlled by the integration stage (23) to the Ausgrationsstufe (23) and a gate of this integration stage (23) which are provided by the output signal dazzle, are combined in one stage (24), which combine the phase of the generator subtraction stage and the result level (3 to 5) generated reference color _{carrier (/ s} ) 60 output signal of the same for synchronization alternating inverted or not inverted, generation of the switch is used. forms is. The circuit for decoding the chrominance signal 4. Decoding circuit according to claim 2 or 3, in a PAL color television receiver, in which one characterized in that the control circuit is first designed as a stabilizing generator stage (16 to 20) for the gate step (6) one of the 65 device with an upstream gate step from the delayed and shaped line sync signal is received, in phase from line to line controlled bistable multivibrator (18) to 90 ° alternating color sync signal a first shows. Reference color carrier with constant, to a first