DE2458198A1 - SYSTEM FOR COUPLING THE FREQUENCY MODULATED COLOR CARRIERS IN THE SECAM COLOR TELEVISION PROCESS - Google Patents

Description

? /, 5R 13ft

ROBERT BOSCH GMBH PEI / Ss / Et

3.12.74

RI. 3ffr. 1655/74 "

The invention relates to a system for doubling the frequency-modulated color carriers in the SSCAK color television method, with x ^ elchem a level signal is derived during the horizontal blanking, which is used to track the
Fax "bträgerfrequenzen serves on the color carrier idle frequencies corresponding to the SEGAH standard.

In the SECAIT color television method, a color carrier is alternately transmitted with one of two color difference signals (SY). (3-Y) frequency modulated. For improvement; the coapability and the signal-to-noise ratio, the frequency of the color carrier is switched over when the two color difference signals are monitored. Switching takes place between the frequencies F _QR = 282.f _H =
4.40625 HHz + 2 IcSz and F _QB = 272.% = 4 * 250 HHa + 2! Sa, where fj is the horizontal frequency. The implementation of such a frequency modulator is relatively difficult because the rest frequencies fq-q and f ^ g in the frequency modulator
must be changed from line to line with the aforementioned frequency accuracy.

It is confused, the frequency of the; frequency-modulated color carrier in a phase comparison circuit with the respective color carrier idle frequencies. Compare Έ ^ and F _Q g and derive a sailing signal. Since the frequency tracking may only take place in the side in

S0982U0591

ROBERT BOSCH 6MBH

Rl. Mr. 1655 / 74- "- 2 -

that the frequency modulation is definitely zero will be the respective spanxomgspegel of the control signal only during the Horizontal blankings are scanned and then stored for the duration of one line. The loop of the phase locked loop: xfird thus only for a fraction of a horizontal period (A - 10 / isec.) closed. It is therefore necessary to adjust the noise bandwidth of the phase locked loop so that a! your Hegel time is obtained. Accordingly, will the level steepness of the phase-locked loop is largely granted. There but the properties of a phase comparison circuit through Raiisch bandwidth, control steepness and capture range are determined can be used with a frequency offset of the frequency modulator, which is greater than that of the capture range, the frequency of the Frequency modulator no longer responds to the required idle frequency to be pulled. In this case, external intervention in the phase-locked loop is necessary in order to get back into the capture range of the Phasemrergleichsaltung to come.

The object of the present invention is therefore to provide a system of Specify the type mentioned at the beginning, "in which the capture range of the Paasenregolkreis is enlarged without the control slope a

This object is inventively achieved in that a first control signal is derived initially in dependence of the frequency deviations between the Farbträgerfrecpienzen and thy the SBCAM standard corresponding FarbtragerriiEiefrequenzen * which on the Segari-Standarid regulates the frequency of the color subcarrier corresponding color subcarrier resting frequencies, and in that in dependence of remaining phase deviations between the. color carriers regulated in frequency and the. a second sailing signal is derived which tracks the phase position of the color subcarriers to that of the color subcarrier idle frequencies corresponding to the SEGAM standard.

$ 0982.440591

BAD ORfGWAt

ROBERT BOSCH GMBH

Bl. ITr. 1655/74 ·. - 3 -

Developments and advantageous embodiments of the erfindungr According to the system, the characteristics of the subclaims are assigned remove.

The system according to the invention has the advantage that the Phase discriminator now on a very large Eegel steepness is dimensioned while the, now by the frequency discriminator "influenced capture range, disregarded" can remain.

For a more detailed explanation, an embodiment of the system according to the invention will now be described with reference to figures. Show it:
Figure 1 is a block diagram of a known system for coding sequential color difference signals according to the SEGAH standard,

Figure 2. a block diagram of a first embodiment of the system according to the invention and

Figure 3 is a block diagram of a second embodiment of the system according to the invention.

In the figures, the same parts are provided with the same reference numerals.

In Figure 1 is an excerpt from a block diagram of a known SECAM coder shown. Via terminal 1 a 'First input of an adder stage 2 sequential color difference signals - (E-Y) and (B-Y) supplied. These color difference signals were obtained in a manner known per se from the three color value signals R, G and 3 of a color signal source (not shown) generated by hatrization. Furthermore, the ~ color difference signals were given identification impulses in the form of

609 8 24/05 91

ROBERT BOSCH GMBH

Rl. No. 1655 / 74- - 4- -

Sawtooth pulses added in the Vcrtikalaustastlücke and subjected to a video pre-emphasis. Furthermore, these were Color difference signals amplified at terminal 1, with the Color difference signal (R-Y) according to the SECAM standard a phase shift took place by 180 °. The color difference signals that had previously existed in parallel were switched via an electronic switch into a sequential series of color difference signals converted.

A meandering signal of half the line frequency is fed to a third input of the adder 2 via terminal 3. The meandering signal is used to support the catching process in the subsequent phase-locked loop. The signal that can be picked up at the output of adding stage 2 is clamped to a fixed reference potential in a clamping stage. The clamping is usually done by controlling with horizontal-frequency pulses on terminal 5 fraf the rear porch of the horizontal blanking of the color difference signals. The signal clamped in this way is limited in amplitude by a limiter 6 and fed to a first input of an adder 7. The output of the adder 7 is connected to the modulation input of a frequency modulator stage 8. After another amplitude limitation with a limiter 9 is connected to terminal 10 the modulated color carrier signal F. Part of the frequency-modulated color carrier signal at terminal 10 is fed to one input of a phase discriminator 12 via terminal 11. The quiescent frequency color carrier signals Fq ^ and F _{QB are applied to the other input of the phase discriminator with terminal 13} sequentially switched from line to line. The signals at terminals 13 and 13 are compared to derive a control signal in phase discriminator 12. The control signal at the output of phase discriminator 12 is filtered with a low-pass filter 14 and via a terminal 15 of a device

609-β * 24 / θΒ ^? 91

ROBERT BOSCH GMBH

El. ITr. "1655 / 74- - 5 - '

for time-selective sampling and storage (sample & hoId circuit) fed. Devices for time-selective sampling and storage are "known and essentially exist from a storage capacitor, in which the voltage level of the input signal at the output of the low-pass filter 14 periodically by control with a sampling signal at terminal 17 is saved. In the storage capacitor of the device 16 for time-selective sampling and storage thus a voltage is stored which is proportional to the phase deviation between the modulated! color signal and the quiescent frequency 3? color carrier signal during the horizontal blanking is. The stored voltage provides a correction signal which is fed to a second input of the adder 7. By superimposing the correction signal (ecgel signal) with the supplied at the first input of the adder 7 Signal in the adder 7 is achieved that at the output of the IT frequency modulator 8 is a frequency modulated Parb carrier signal will be removable, whose resting frequency in the horizontal stop interval (back porch) is regulated exactly to one of the carrier resting frequencies.

However - as mentioned at the beginning - the dimensioning of such a phase-locked loop 7, 8, 9, 11, 12, 14-, 15 and 16 is only possible with a compromise between control steepness and catch range is shown in FIG. 2 after a first one Execution of the system according to the invention in parallel with Phase discriminator an event discriminator 18 is provided, depending on the frequency deviation of the frequency-modulated Parbtragersignal at terminal 11 with respect to a predetermined center frequency (resting frequency) a control signal derives which is the frequency offset of the erection modulator tracks. The Hsgelsignal of the Frequenridiskriminators 18 and the control signal of the phase discriminator 12 are in a Adding stage 19 superimposed and via terminal 15 on the input

'■ 603824/0591

2AER1-M.

ROBERT BOSCH OFiHBH

El. No. 1655/74 - 6 -

supplied to the device 16 for time-selective sampling and storage. The voltage levels of the "two control signals are the Adjust control conditions. It is beneficial to control of the frequency discriminator stronger than that of the Phase discriminator to choose so that there are no pseudostable Set areas in the level loop that "snap into place" of the frequency modulator 8 cause.

As a circuit for a phase discriminator, the a double push-pull arrangement ". Such a phase discriminator with a double push-pull arrangement is described in U.S. Patent 3,550,04-0. As a frequency discriminator a transit time demodulator whose circuit arrangement is particularly suitable. ' essentially that of the phase discriminator in corresponds to the aforementioned US patent, but one input of which, via a delay line, whose delay duration at a color subcarrier resting frequency (I // 4. f) or a is an odd multiple of what the terminal atKLemmeH, lying frequency-modulated color carrier signal is supplied. The delay device advantageously consists of active or passive filter elements with a linear phase Transfer factor.

The block diagram shown in FIG. 3 shows a second embodiment of the system according to the invention. Instead of a phase discriminator, a frequency difference detector 20 is used here. Such frequency difference detectors are known. By comparing the frequencies of the signals at terminals 11 and 13, a PL control signal is derived in the frequency difference detector 20, which controls the frequency modulator 8 to the required color subcarrier idle frequency. As Frequenc difference detector is' also advantageously a Quadri-Ife? _S relator whose Sohaltungsan-

- 7 -

09824/05 91 bad original

ROBERT BOSCH GMBH

¹ St. 1655/74 - 7 -

Orders and instructions from Zeitscarij, for example "Proceedings of IRE", 1959, pp. 288-299.

609824/0591

Claims (11)

ROBERT BOSCH GMBH St. ITr. 1655 / 74- - 8 - System for doubling the frequency-modulated color inertia in SECAM color television failure, in which during the Horiζoiital blanking a control signal is derived, that for tracking the color subcarrier frequencies to the color subcarrier idle frequencies corresponding to the SECAM standard serves, characterized in that depending on the frequency deviations between the color carrier frequencies and the color subcarrier idle frequency corresponding to the SECAI-I standard a first Rogelsignal is derived, which the frequency of the color carrier on the SECAIl standard corresponding color carrier idle frequencies regulates, 'and that then depending on the remaining phase deviations between the frequency-controlled color carriers and the dye carrier dormant frequencies corresponding to your SECAI-I standard a second control signal is derived, which the phase position of the color carrier to that of the SECAIi standard tracks corresponding color carrier idle frequencies, 2. System according to claim I _1, characterized in that the voltage of the first control signal is greater than that of the second control signal. 3. System according to claim 1 and 2, characterized in that the first and the second control signal are added to form a common control signal. 4. System according to claim 3 _}, characterized in that the common control signal "is fed to a device (16) for time-selective sampling and storage, which 6 0 9 8 2 4/0591 bad original ROBERT BOSCH GMBH Rl.-Hr. 1655 / 74- - 9 - is connected to the input of a frequency modulator (8), at which. The output fi-equenzmodulicrte Färbträgersignal (F ·) ^v is abnehmbai. nod -. ' 5. System according to claim 1 to 4, characterized gekermr, eichnöt that with a frequency discriminator (18), which the frequency-modulated color carrier signal (^ _Γ10 ^) is supplied, the first fly signal is derived. ■ 6. System according to claim 5? characterized in that the frequency discriminator (18) consists of a known quadrature demodulator with two pairs of transistors, in which each pair is controlled by an input transistor, the frequency-modulated Parbträgersignal C ^ L ^ t) "supplied directly to one input and the other input via a delay line whose electrical length at a color subcarrier frequency is (1/4 f \ or an odd multiple dax ^r on. 7. System according to claim 6, characterized in that the Delay device consists of an active or passive filter with a linear phase transmission factor. 8. System according to claim 1 to 4, characterized in that a phase discriminator (12) to which the frequency-modulated _{color carrier signal (^ m0} ^) ^and - si ^ color carrier idle frequency signal (Fqtj and ^ Vyo) is supplied, the second control signal is derived. 9. System according to claim 8, characterized in that the ge2cennzeicb.net Frequency discriminator (12) from a known double-G self-clock modulator with two pairs of transistors in which each pair is controlled by an input transistor. _ 609824/0591 BADORiQWAL ROBERT BOSCH GMBH Rl. Mr. 1655 / 74- - 10 - 10. System according to claim. 1 "to 4, characterized in that the first control signal is derived with a frequency difference detector (20) to which the frequency-modulated © color carrier _{signal (^ nocl} ) and ^the color carrier frequency signal (Pq _R and P _{QB) are supplied.} 11. System according to claim 10, characterized in that the frequency difference detector (20) from a per se "known Quadri-Correlator ". 60 9824/059 1