DE1303693C2 - CIRCUIT FOR CORRECTING THE PHASE OF THE MODULATED COLOR CARRIER OF A PAL COLOR TELEVISION SIGNAL - Google Patents

Description

(German P

With a phase-modulated color carrier of a 40 tion the color carrier consists of two ^temporally _n ^ ^f ^ " ^a " ^d _B ^e _e ^r -

Color television signal, phase errors occur easily in the following lines of voltage and unencumbered

Transmission path, which in the receiver to color tone tensile carrier of constant phase of a phase comparison

lead to falsifications. Such errors can, for example, lead to and with the intestine gained

arise from the fact that the phase shift of a control voltage increases the running time of a Laufze.tle.tung

Control transmission element of the respective amplitude 45, which in the signal path of the harb-

of the luminance signal to which the color carrier is the carrier. So this circuit works according to one

is stored. depends on (differential phase error). With the other principle than the invention

NTSC color television signal can such errors The correction according to the invention is carried out in such a way

only with complicated equalization circuits eliminate the fact that the color carrier to be corrected in the t-artv

and only if the dependence of the 5 ° carrier modifier on a modulation acnse

Error is known from the luminance signal. Error is reflected, the phase of which tolgi the phase error.

of any other kind cannot be eliminated, because each of the "rotrager

The temporary phase of the NTSC color subcarrier is not required - over two lines is not necessary

can be seen which proportion of the respective phase also results in the advantage that the amplitude of the

Useful modulation and what proportion of a phase 55 color carrier is not changed and the modulation

error is. tion content of the color carrier with an error-free signal

In the case of the PAL color carrier, the color cannot be influenced ·.

carriers from two consecutive lines The invention is described below with reference to the

determine the phase error because the phase error explains the drawing. Then show

Phase of the color carrier of a line from the fixed 60 Fig. 1, 2, 4 vector images to explain the effects

Modulation axis (whose phase is determined by the

Chronsignal is known) turns away and in the following- F i g. 3 shows an exemplary embodiment of the invention and

stcn line turns towards this axis. 5 shows a modification of the circuit according to FIG

the possibility of phase correction circuits Fig. 3 ...

to create the phase error independent of 65 In Fig. I the error-free color carriers / ·

eliminate its origin. and F is a phase opposite by the angle *

In a known circuit (Rundfunktech- the fixed axis Q is fixed. Χ is the respective niche messages ”1963, p. 93) is the angle that the modulation content, namely the

3 ⁴

Hue indicating. Added by a phase error in the over-. Thereby, ^^^ KffsSf ^ ⁸ tragungsweg the two Farbbtxäger are shifted by an 18, the angle with half the phase ^ nke ^ I de ^ gnak 17 ^ in the same direction, so that ie with the angle ,, ff. ^E ^ ^U gJh ^D P 'flawed color carriers F' and F 'arise. Reference oscillation 18 is fed to the modifier 1 via line 3. These two color carriers are no longer symmetrical. fnioende 'JVei · * - tric to the axis β like the error-free color carrier, the modifier itself works «d ™ gwkj ^. but symmetrical to a wrong axis Q \ die The in Figs. 1 and 2, the mirroring of the axis Q also J's _{shifted by the angle Ψ} with respect to an axis according to the ground is. In the case of a demodulation along the Q axis of the PAL system, a luiterden means that the color carriers F 'and F' do not provide falsified coloration and different phase modulations that do not affect signals. conjugates complex color carriers. The

According to FIG. 2, the error-prone emp- a modulation direction is the «^ ** ™ ^" ™

catch color carriers Γ and F 'according to the invention to the other modulation direction the lower K = j * «™ -

mirrored an axis represented by Q " and b ~ .nd. It is now assumed that the dem

with respect to the axis Q by half the error angle, 15 modifier 1 supplied J. ³ ™ ^ "/" _p f £. ™ T ~ "

i.e. φ / 2, is shifted. From the fifth. The direction of color modulation corresponds to that of the upper end

Carrier F 'is then the correct color carrier F of corresponds to. In modifier 1 this is indicated with «and 7 ·

Fig. 1. although this color carrier is actually. -Haste even modulated color carrier with the color carrier not marked with *, aDer mn

is not transmitted. From the erroneous Kirb-modulated Be / ugsschv in ^ ng 18 doppuitr tan

carrier / ', on the other hand, is created by the reflection at ao carrier frequency mixed. Denuutstieg enisicni uur,

the axis Q " the error-free color carrier F By this mixture as a difference frequency a farotrage

Reflection of the phase-faulty color carrier on the frequent signal, but now with the lower aeiui,

an axis whose phase is proportional to the fund, so that the modulation direction is also reversed

Phase error is modulated, so phase error is reversed. The reverse modulation direction tv

free color carriers won. _{but a5} indicates a reflection on an axis gcmai.

Fig. 3 shows an embodiment for the Fig. 1, 2. If the / ugled reference slip

Solution according to FIG. 2. The faulty color carrier F 'supply 18. For example the phase position Q according to Hg./ na.

or Γ is fed to a modifier 1. This is how the reflection takes place on you axis γ ui-

Modifier 1 causes the reflection of the color riger reference oscillation 18 double color carrier frequencies,

according to FIG. 2 and ran at a terminal 2 the 30 is modulated with the error angle ,, so UaU wu

error-free color subcarrier F or F The control of the related to the color subcarrier frequency, the AcnsL

Modifier 1, i.e. the information at which the reflection takes place, using the angle 7 ...

Acbj the mirroring is to take place is modulated according to the mode shown in FIG. The Be / ugsschwinguiK

fikator 1 via a line 3 supplied. The 18 with double the color subcarrier frequency, freed from the

Guided reference oscillation is in the following way 35 phase modulation χ of the color carrier, but modu

obtained: by means of a delay line 4 with liert with the error angle 7, thus effected in modes

the delay time of a line duration, a 180 - indicator 1 that the color carrier received in each case

Phase rotating element 5 and two adding stages 6 and 7, one dependent on the error angle 7 in the phase

the sum and difference of the conjugate korn axis (? "are mirrored and thus converted into a fenler-

plex color carrier of temporally consecutive time 40 free color carrier is converted.

len won. This results in a further example of extraction at the output of FIG. 5

Adding stages 6, 7 color carrier-frequency signals, which are derived from the reference oscillation for the mocjificator I. Lm

uzt phase modulation χ freed, but from the signal /, with color subcarrier frequency, modulated with the

Phase _{error angle Ψ are} dependent. This farocarrier error angle 7, which according to FIG. 3 by addition

Frequent signals are in frequency doublers, 45 or subtraction of the conjugate complex color

z. Overall carrier F, F of consecutive lines - as in Doppelwe-rectifiers 8 un i _t 9, 180 °

Phase jumps, which is also achieved on the modulation, from a terminal 20 to a module

depressed carrier are released and fed to gate 22, which is on the other hand of a Quar / -

to double the color carrier frequencies / implemented. With oscillator 23 a color carrier frequency signal / ₂ without

a phase shifter 10, the signals dop 50 are fed to each phase modulation. Through the

pelter color carrier frequency to the same phase modulation of /, with / ,. arises at a clamp

and put together in an adder stage 11, 21 at the output of the modulator ii.i modulation pro-

at the output of which there is a signal that, according to dukt u. a signal /., double color carrier circle /,

twice the color subcarrier frequency. with the double that is phase modulated with the error angle 7 and

th error angle 27 is phase modulated. This Si 55 as a reference oscillation Ϊ8 according to FIG. 4 for the control

Signal is used via a line 15 of an adder 12 tion of the modifier 1. for

fed. The adder 12 is, on the other hand, via the extraction of the reference oscillation, which in the mode

a line 14 a signal of double color carrier ficator the color carrier by a counter modulation

frequency, but supplied with a constant phase, which frees it from the phase error, thus becomes a constant

a crystal oscillator 13 from the color synchronous 60 frequency and the phase modulated with φ, the

impulses is obtained. Signal extracted frequency required. At the wic-

The operation of the adder 12 is based on Fland dergabe from the magnetic tape, the constant Freder F i g. 4 explained in more detail. The frequency of the clock generator system taken from the line 14, the incoming signal 16 of constant phase is the one before the pulses from which the magnetic tape of the line 15 comes signal 17, which is synchronized with the 65. The crystal oscillator can then be angle ψ2 modulated, with the same amplitude omitted.

For this 1 sheet of drawings

Claims (3)

™ proverbs: 1. Circuit for correcting the phase of the mo- zügeragι ui double amplitude won, dulierten color subcarrier of a PAL color television ⁵ ° S £ ^he ^ _"äßiee mirroring is carried out with a signal with a Farbträgermodifikator of a P" known ^ "'' ^B Silung Farbträgerdie Spiegelungsacnse by ugefiihrte Bezugsschwii. ₃ ungbtimt dulierten color subcarrier of a PALFarbfer S £ ^ _äßiee mirroring is carried out with a signal with a Farbträgermodifikator, a P "^""^ ^B Reflection known color carrier phase Light Reflection of the ink carrier at a ^mm .ii ^we r ~ _It i _st the Spiegelungsacnse by modulation axis causes the _fi by the Modin Kai ⁰ ^. zugefiihrte. Bezugsschwii. ₃ ung rh Bhi be "" ^^^ fST Modulation axis causes the durh Modifier associated reference oscillation determines ^^^ fSeTfreuuenz determined, is correct, characterized, "^^ ÄJScytimg takes place in that by addition (level 7) and subtraction ^" this ötjwn ^ _errorfmem ^^ (levels 5, 6) of the modulated, not corrected Nutzsignaiwj? ain ^. ^. ^ ^ Color carrier (F ', F) from two temporally successive- * ⁿ ^ ™ ^g X _un \, _{in the} vertical direction tracing lines color carrier frequency signals are generated by the solution _{be attested} that these signals in the frequency 15 «" ^^ "June, ieet based on the task, a doubled (steps 8,9), with a phase rotator The invention lies ι α e ^ b ^ _de f _pAL . _{Q: iriv} (10) brought to the same phase and then circuit ™> . · ■ novel i n- are added (Siu.e 11) and that the thus sluggish / u lh .... ■ ^ ^ ^ voltage gained after halving your zip works ud · ■ ■ fc | _ger than _wo /, η Phase modulation angle (2f /) as mountain vibra- 20 der / »grain; -. ^ ■■ - '· fc · ^gUngd ' ^ent · u, .1 u ^bC n !!! ^P r _r , indu.i »■■ ·» «. '^ From a switch 2. Circuit according to claim 1, characterized in that the LriinUun. n modulated color ti r _S indicates that the halving of the phase Koruk.ur f ₍ f ¹ - ^{1. A.} ^ J ^ ' modulation angle (2 ,,) takes place in that a PAL rarbf, ^ l ^ ™ JJ ^η ^> ™ / ^ to the voltage obtained by the addition «5 modiHkator. dc '''' ^ f ^, "^ 'axis effect-. _e (17) eme tension (16) Soppeher color carrier- color carrier to cmc, VJ ^^ _h ™, ^ frequency and constant phase is added. by a dun MoiiiiiKaior _t • 3. Switching «3 nad, claim 1, characterized in that« "» '"^^' vl.Si that by Add :,." draws that the f-re <) uen / .v »rdc, poppel and Hai- The hrnnuuii). . ^ c bation of the phase modulation angle thereby 30 and ^{Subtrakt.on der nM} ^ rttn ' _f that the add-on or subtract color carrier from / wc. / c hch au tion voltage obtained in a modulator lines color subcarrier trap., c signal. ^^ j (22) with a color carrier frequency voltage that these signals ..1 of the f'f ^ e ^ constant phase is mixed (Fig. 5). a phase rotator to g ^ ^ 8 ™ t. ,, d ^B 35 are then added, and that the Uauu.Lh voltage obtained after halving its phase modulation angle serves as a reference oscillation A circuit has also been proposed (German patent specification 1 227 507), one by Addid Fbä two ^temporally ^ ^f ^ " ^a " of ^the - hch ^^^ ^