DE2754511C3 - PAL decoder for processing a color carrier frequency PAL chrominance signal - Google Patents

Description

The invention relates to a PAL decoder for processing wincs direct frcqtientGn PAI. Color bar signals according to the preamble of claim I.

There is already a color television receiver for a color-accurate NTSC system (DE-PS 12 52 7Jl) to which the Basic principle of a standard PA L decoder, namely a circuit for electronic averaging of a PAI. color television signal, / u. This Standard PAI decoder, from which the generic term des Claim I is based on FIG. J explained in more detail.

There is also a decoder for PAL color television signal known with two delay units each consisting of transmission elements and reactive elements (DE-OS 19 IO J87), Daoei consists of every delay device from a series circuit with the transmission elements and capacitors, with which but no synchronous demodulation can be carried out.

in this well-known decoder are therefore additionally Pulse generators and gate circuits for synchronous demodulation of the chrominance signal is provided, which significantly increases the circuit complexity will.

ι -, Finally there is a delay line • wrclnung for the color decoder of a PAL color television receiver. at which the delay lines are off Shift registers exist (DE-AS 20 56 276). In this delay line arrangement, too, the

> (i delay lines therefore not for synchronous demodulation, so that demodulators must also be provided.

As shown in Fig. I, in the PAL color television system during a certain horizontal

Ji sampling period a color carrier frequency (R- V ^ color signal F ⁺ , whose modulation axis coincides with the positive (R- V7 "axis, as well as eiti color sync signal B * with a lead of 135 ° with respect to the (B- V ^ -axis and during the following Horizon

J ₀ tal sampling period a color carrier frequency (RY) chrominance signal F-, the modulation axis of which coincides with the negative R- VT axis, as well as a color sync signal B with a phase replica of 135 ° with respect to the (B- > 9-axis

π is also shown in detail in Fig. 2, in which successive chrominance signals and other signals are represented by phase diagrams during the (n- 1) th, (n) -icn, (n + 1) -th and (n + 2) -s Horizontal scan time periods are shown.

4Ii F i g. J shows a block chak shield as an example of his Standard PAL decoder for processing a color carrier frequency PAL chrominance signal (see. DE-PS 12 52 731). In this case, an input terminal I from a second detector (i.e., "one not

ι, shown video detector) fed mixed video signal in a Bandpaßfilicr 2 and a Baridpaßvcrstarkker 3 processed so that a color subcarrier-frequency chrominance signal A is filtered out. A color sync signal ff is generated by the chromaticity

vi signal A separated in a color sync gate 4. The chrominance signal A is output to two comb filters comprising an IH delay line 5 (IH = one horizontal scanning period), an adder 6 and a subtractor 7.

γ, A signal A ' generated by the IH delay line is delayed by one Honzontal sampling period with respect to the original signal A , as shown in lines A and A ' in FIG. 2 is shown. When these signals are mixed in the adder 6, results

,, ο in each sampling period one in line B of the Γ i g. 2 shown farbträgerfrequentes (B V ^ Farbartsignul .SV When these signals are mixed in the Subtrahicrer 7, there arises a g in line ( "F i shown farbträgerfrequcntcs (R 2 -. VT-Earbartsignal S ₂ with decreasing

,, -, alternating reversed form in successive Sampling periods.

If the frcqiicnzspcklrcn these signals accordingly F i g. 4a are examined, has in the color carrier

quenien PAL chrominance signal, the farbträgerfrequente (I) - V> Farbiirisignal a spectrum of a / ugsfarbträgersignals (vgl.2l) is distributed at a frequency U in a frequency interval of the horizontal scanning frequency in both sides lle as 22 Jargestellt is by full arrows, while the color carrier frequency (R - Y) chrominance signal has a spectrum distributed on both sides lcs reference color carrier signal in a frequency interval of the horizontal scanning frequency fu , the components with the next frequencies to the reference color carrier signal being spaced from this by fnl2, as indicated by dashed arrows 23, which is based on the above-mentioned alternating phase reversal in successive horizontal scanning periods.

The 1 H-Verzögerungslcitung 5 and the adder 6 and subtracter 7 each form so-called comb filter having frequency characteristics Einei period fu (see FIG. 4b and 4c) for screening out the farbträgerfrequenten (B- V> chrominance signals B (Sl) and the farbträgerfrequenten ( R-Y) - chrominance signals C (S2) depending on their transmission characteristics 24 and 25.

The color carrier frequency (R- V9 chrominance signal C, which is screened out in this way and whose phase is alternately reversed in successive horizontal scanning periods, as shown by arrows S> in FIG Each horizontal scanning period is switched by a flip-flop 18 which is controlled by a horizontal frequency pulse signal which is fed from a horizontal deflection element (not shown) into a connection 20 directly or via a phase inverter 8. In this way the electronic switching element 9, which alternately generates the output signals of the subtracter and the inverter 8 at its -m output terminal, emits a signal Sj which has a continuously corrected phase over the horizontal scanning periods, as shown in line or in FIG. 2 is shown.

The color subcarrier frequency (B- Vy chrominance signal ß and the color subcarrier frequency (R- VT chrominance signal D, which are screened out in this way) are then fed into a color signal demodulator 10 and 11, which synchronously record the fed-in signals, on the one hand with a reference color subcarrier signal F ( S * in Fig. 2), which is synchronous with the burst signal E , which is based on the generation by a voltage-controlled oscillator 16 which is controlled by an output signal from a phase detector 15, into which the burst signal E filtered out by the burst gate 4 and the output signal . the spaonungsgesteuerten oscillator ·· 16 are fed, and on the other hand, out of phase with a reference carrier color signal O (St in F i g. 2), the degrees to the reference color carrier signal F by a +90 phase shifter 19 thus become the farbträgerfreqiiente (B- ^. - The chrominance signal and the color subcarrier frequency (R- V / color signal at the output terminal 12 and 13, respectively) are reproduced.

A control element 17 controls the phase of the flip-flop 18 and the operation of a color blocking circuit 14 with the output signal of the phase detector 15 to ensure an accurate To ensure switching of the switching element 9, and it causes the color distortion circuit 14 to pass the bandpass amplifier3 for color erasing.

Although the PAL decoder of FIG. J the chrominance signals can filter out, he needs the I H delay line 5, which can also be a glass delay line (see GB-PS 10 66 < V8).

In such a glass delay line, an electrical signal is transmitted at one of its input ends in converted into an ultrasonic wave signal, which is transmitted through a glass body acting as a delay medium propagates, and the ultrasonic wave signal is converted back to an electrical signal at the output end, so that the electrical signal is delayed by the propagation time in the vitreous humor. Therefore, it is in principle difficult to achieve a constant delay characteristic over a wide frequency band, and unwanted reflected components are easily generated in the glass body. Besides, they are The temperature characteristics of the delay line are inadequate in many fills. So that's a delay line very expensive with satisfactory operational behavior.

In addition, if the decoder is integrated, it is to provide the delay line outside of a semiconductor body as a separate component, what the Reduced benefits of integration. Therefore, the construction of this well-known decoder, .jfw, is finite, and for Manufacture and adjustment will cii.t t-r increased number of processing steps required, the effort increases.

It is therefore the object of the invention to provide an integrated Specify manufacturable PAL decoder, in particular characterized by a particularly simple structure with regard to the delay line.

The solution to this problem is with a PAl.-decoder according to the preamble of claim 1 according to the invention by the features of given characteristic part.

In the case of the PAL decoder according to the invention, the two pairs of charge-coupled elements des Adders and subtractors a delay of the color carrier-frequency chrominance signal and a synchronous demodulation to generate two colors achieved. As a result, on the one hand, the deterioration properties improved, d. H. the frequency band for the signal delay is broadened, and on the other hand the production of the entire decoder in integrated technology is made easier.

So two pairs are charge-coupled Limbs used. In each pair, the two charge-coupled members lead a synchronous diiodula tion of the fed-in chrominance signal at high frequency off, and the signal transmission time through one of the two charge-coupled members is increased by one Horizontal scanning periodc longer than set by the other charge coupled device by a delay time from one horizontal scanning period.

The PAL decoder according to the invention does not see any separate delay device. but instead uses the charge-coupled links that by clock signal? are operable, which are synchronous with the reference color carrier signal, whereby the scanning and Delaying the chrominance signal for demodulation can be achieved at the same time. This allows the structure of the PAL decoder is simplified and the integrated execution is facilitated, since there is no complex and difficult to integrate delay line is provided.

In addition, since the signal transmission time of the charge-coupled members is essentially determined by the Frequency of the Taklisgnals is determined for a given structure of the decoder and not by one Temperature change depends and there is no unwanted

reflected signals are present, becomes a more reliable one Decoder with good lies enables.

The discovery on the basis of animal / calibrated methods is not sufficient explained in more detail. Ils shows

I "ig. I a phase diagram to explain the Transmission of PAL chrominance signals,

I "ig. 2 a group of phase diagrams; for lirlüuierung the operation of a shown in Fig. i Block diagram.

Γ ig. J a block diagram of a herkommlxheri PAI. Decoder for processing a no-carrier-free swelled PAI. Chrominance signal.

I'ig. 4a to 'te I frequency specs of the color defect frequencies Chroma signals and filter characteristics for running the signals.

I 'i g. 5 shows a block diagram of an exemplary embodiment of the decoder according to the invention for processing a chrominance signal with a color carrier frequency and l "ij :. tJ. 7 üi'iu oi im ·» ϊΐι lyiitjiic'ifi'iiVrO / in 'ι .i ιιμπι.Tüi'ig

the operation of the in Γ ι g. ^r i shown decotiers

Fig. ^R> is a block diagram of a Ausfülirungsbeispicls of erfindungsgemäUeii PAI.-Deeoilers. Iliti essential difference to the circuit diagram of the I i g. 3 is that the delay line ΐ and the I aibdeniodiilaloren IO and I 3 are omitted and instead a first pair of charge-coupled (CCD) 2h and 27. a second pair of charge-coupled (components 28 and 29 and low-pass filters 30 and 31 In I i g. 5, I ¹ IItSPrCcIH ¹ IuIc I'eile mn the same reference drawing are seen in Γ ι gi

Kin larbiriigerlrequeii'es l-'arharlsignal from the tape paßversiarker 5 is delivered to the two pairs of hidtingsgekoppeller members 2h, 27 and 28, 29 in order to filter and delay the chrominance signal with the following signals used, ils clock signals: The first pair charge-coupled ^ Members 2h and 27 is with a clock or. Bi-Zugslarblrägersignal / Y-Si in I "i g. 2) is applied, the", from the color synch signal I ' isi. What is based on the Frzeugimi. ¹ dun.li the voltage-controlled (oscillator lh, which is based on the output signal id ¹ " * PhM ^ i ¹ MiIi ¹ Ii ¹ L Ii u ν I ^: i ^, 'UtMitirt iu in iltMl rl: »*.

I arbsv nclironsignal / and the output signal of the voltage control unit are fed in; read pair of charge-knotted Cilieder 28 and 29 is with a 90 phase-shifted modification C / of the reference Marhtragersignales I ( see in I ι g. 2) \ ersorgl.

The above Betneb is based on the I'ig. b closer explained in the / own:

a) a l'arbirägeilivc; lertes l'arbartsignal. which is fed into the charge-coupled links 26-29. A dash line 32 indicating the color subcarrier frequency (B- Vf color signal component and a solid line 33 indicating the color subcarrier frequency (R- > 7 color signal component.

b) a clock signal G am / wide pair of charge coupled members 28 and 29.

d) a clock signal Farn first pair of charge-coupled devices Links 26 and 27.

c) the amount of a charge 37 of the color carrier frequency. Chrominance signals *, which is sampled for transmission by the clock signal G in the charge-coupled elements 28 and 29. and

e) the amount of a charge 35 of the color carrier frequency I arbartsignaies. that for transmission by the clock signal F in the. charge-coupled links 2h \ utd 27 abLVUM.i. <. <

There. As explained above, the clock signal / ■ 'at the first pair of charge-coupled elements 26 and 27 is the reference color carrier signal .V4 which is synchronous with the color sync signal. and since the clock signal G on the second pair of charge coupled devices 28 and 2 ⁵ J is a + 90 ^r or .τ / 2 phase shifted modification of the clock signal c / " and 27 is scanned, only that of the color carrier frequency (B- VT-farbartsigmil 32. and the amount of charge 37. which is scanned for transmission by the second pair of charge-coupled circuit members 28 and 29. is only that of the color carrier frequency (R- > 7 -F ^; arbartsignal 33 Thus, the color carrier frequency (B -)> larbart signal 32 in the first pair of charge-coupled elements 2 (· and 27 and the color carrier frequency (R- >7-F'arbartsi signal 33 in the second pair of charge-coupled elements 2C

As in lig. 7 shown isl. is by sampling the color carrier-frequency l'arban signal 39. which was modulated onto a reference color carrier signal 38 of a frequency / j, with the clock signal ! ■ ' or G. which is synchronous therewith. a multiplication is carried out in such a way that the chrominance signal 39, which has a frequency of color carriers, is converted in frequency to a low frequency band for transmission in the form of a chrominance signal (C) converted to a low frequency.

By creating a difference between transmissions / ei ten. d. H. Signal delay lines, in the charge-coupled devices Members 26 and 27: ind a difference / between these in the charge-coupled members 2f and 29 both selected equal to a horizontal scanning period c (1 U) and the respective output signals through the adder 6 and the subtracter 7 are processed, the sampled chrominance signals with dei Clock frequency are generated.

The frequency spectrum of the low frequency converted l'arbart signal is shown in Fig. 8 (a), in which the (B- > V chrominance signal component 41 and the (R- V / Marbard signal component 42 cyclically at points on) red, which are spaced from each other by .τ / 2.

By thus adjusting the charge transfer time of the first unc: the second pair of charge-coupled elements 26 bi> 29 in the manner explained above by adding and subtracting! the first pair of charge-coupled elements 26 and 27 and the adder 6 form a comb filter with the one shown in FIG. 8 (b) characteristic shown, and the second pair of charge-coupled gates 28 and 29 and the subtracter 7 form a comb filter with di_i ir Fig. 8 (c), characteristic curve, wherein the sampled (B V ^ chrominance signal 43 at the output of the adder 6 and the sampled (R- Y) chrominance signal 44 arr output of the subtractor 7. Since the phase of the (R- Y) chrominance signal is demodulated in successive horizontal scanning periods like the chrominance signal S shown in line Cdei FIG is alternately reversed, it is taken directly or alternately via the phase inverter 8 from the output connection of the electronic switching element 9, which is switched by the flip-flop 18 for each horizontal scanning period as in the decoder of FIG. 3, so that it is converted into a signal constant polarity is converted which is passed through the low pass filter 31 to eliminate unwanted high frequency components urr In this way the (B-VT-Farbdifferenzsigna be at Ausgangsanschl uß 12 and the (R- V> color difference

signal at the output terminal 13 reproduced.

The delay time of the charge-coupled element is defined as the product of the number of delay stages of the charge-coupled element and the period of a clock signal applied to the delay stages, the delay stages having one or more gate electrodes on which the clock signal is applied. In addition, in the PAL color television system, the reference color carrier frequency f _c and the horizontal scanning frequency (» meet the following relationship: f _c = (284-1 / 4) Λ /. By determining the number of delay stages of the charge-coupled elements 26 to 29, that the difference between the numbers of delay stages of the charge-coupled

Pelten members 26 and 27 and the difference between the numbers of charge-coupled members 28 and 29 both have the value 284 and by choosing a frequency with the value f _c for the clock signal frequency, the differences in delay time between members 26 and 27 and are accordingly between members 28 and 29 are both 1 // Ή + (1/4) f _c , which ensures that the phases of the charge-coupled members which are subjected to addition or subtraction coincide with one another.

The control element controls as in the circuit diagram of FIG 17 the flip-flop 18 and the color blocking circuit 14, so as to ensure accurate switching and color deletion.

In addition 6 sheets of drawings

Claims (2)

Patent claims: 1. PAL decoder for processing a color carrier frequency PAL chrominance signal, with a comb filter for forming a first and a second chrominance signal component from the color subcarrier frequency PAL chrominance signal, the second chrominance signal component alternating has reversed phases in successive sampling periods, a synchronous demodulator for synchronous demodulation the first and second chrominance signal components, and a phase reverser for reversing the phase of the / wide chrominance signal component before or after synchronous demodulation, characterized in that the comb filter and the synchronous demodulator are made up of: a first and a second pair of charge coupled members (26, 27; 28, 29) Zcim receiving the Farbiragerfrequenten PAL chrominance signal, with a charge-coupled element in each pair a horizontal scan time longer delay time than the andcie charge-coupled member. a device (15, 16, 19). the in the first and the second pair of charge-coupled members (26, 27; 28, 29) a first and a second clock pulse signal (F. C) in sync with the PAL chrominance signal contained in a synchro signal for frequency conversion of the color. Kcrfrcq "onten feeds PAL chrominance signal to a low frequency band, the second clock pulse signal (G) being phase-shifted with respect to the first clock pulse signal (Fjum Till, an adder (6) connected downstream of the first pair of charge-coupled elements (26, 27) for generating a sum signal from the output signals of the first pair of charge-coupled elements (26, 27). wherein the sum signal represents the synchronous democratic first chrominance signal component, and
a subtractor (7) connected downstream of the second pair of charge-coupled elements (28, 29) for generating a difference signal from the output signals of the second pair of charge-coupled elements (28, 29), the difference signal representing the synchronously demodulated second chrominance signal component (Fig. 5). 2. PAL decoder according to claim!, Characterized through a first and a second low-pass filter (.JO, 13), which follow the adder (6) or the phase inverter (8) to their output signals process (Fig.>).