DD205799A1 - CIRCUIT ARRANGEMENT FOR COMPENSATING FREQUENCY AND PHASE FLAKES - Google Patents

Abstract

CIRCUIT ARRANGEMENT FOR COMPENSATING FREQUENCY AND PHASE FLAWS IN THE PLAYING OF STORED COLOR TRANSMISSION LIGHTS. OBJECT AND OBJECT OF THE INVENTION IS THAT CLOSED CONTROL SYSTEMS WILL NOT BE DISASSEMBLED IN THE SWITCHING OF THE SWITCH AND WILL BE USED AS A DIGITAL ELEMENT LARGELY. THE REGULATORY AGREEMENT FOR THE COMPENSATION OF FREQUENCY AND PHASE ERRORS SHOULD BE OBTAINED BY COMPARING THE SUPPLY SIGNAL DERIVED FROM THE CHEST WITH A HIGH CONSTANCE SIGNAL SIGNAL. THE RULES OF THE RULES OF THE INVENTION ARE USED IN ORDER TO INFLUENCE THE PHASE OF A SECOND AUXILIARY DIRECTOR DIRECTLY IN A WANTED SENSE OF A COMPARATOR AND A SWITCHER. EVEN THE CORRECTION OF THE STARTING PHASE OF THE COLOR SIGNAL TRANSMITTED TO THE ORIGINALLAGE IS POSSIBLE.

Description

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Title of the invention

Circuit arrangement for compensation of! Frequency and phase fluctuations

Anwendungsgel) iet the invention

The invention relates to a circuit arrangement for compensating for frequency and phase fluctuations in the reproduction of stored color television signals.

Characteristic of the known technical solutions

In the case of all mechanically moved information carriers or scanning elements, uniformity fluctuations occur in the movement, which can lead to considerable disturbances in the reproduction of the stored image information.

For Yideo cassette tape recorders for home use, the magnetic tape is in. A predetermined cassette ,, off. the tape is pulled out for playback and placed in the required position,

Video cassette recorders designed for home use have predominantly two magnetic heads, each of which alternately records one field in an oblique tracking position on the magnetic tape.

A recording of the brightness signals and the color signals, takes place simultaneously in a recording process and in one. Magnetic track. For the sake of optimal utilization of bandwidth

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of the memory channel and the storage of the low-frequency signals contained in television signals. Shares it is common to record the luminance signal frequency modulated in the upper frequency range and the color signal after Reaktion.im lower frequency range of the memory channel. The circuit techniques used for this purpose are generally known, "

Due to the recording process and during reproduction, deviations in the reproduction, the exact uniformity of the signal sequences, occur, for example. line frequency synchronous pulses "and the carrier frequency Earb signals, on.

The mechanical-electrical control devices for. the drive of the rotating magnetic head unit and the transport of the magnetic tape can be dimensioned so that the remaining residual error for the 'reproduction of a brightness signal remains small enough *. However, the Femsehwiedergabegeräte can the. Residual error, which is still present as a fluctuation of frequency, and phase of the carried color signal, can not be processed «

It is known to use circuit arrangements that reduce these fluctuations, which are referred to as Jitten ,, by using control and regulating devices so far that a, trouble-free operation is possible.

Figure 1 shows the circuitry used for this purpose in the operating state "recording" (DB-OS.23 42 884, DS-OS 21 23 626, Dl-AS 21 30 091, DS-AS 25 28 826).

Sinem input 1 is the full color television signal from a -SignalqueUe, z. In an amplitude filter 2, the line frequency synchronous pulses are separated and fed to a burst gate 3 after pulse shaping. Eggs become the characteristic impulses accommodated on the backside Schwarzschulter

separated and fed these signals referred to as a burst phase comparison ^ 4 · It takes place in this stage, a phase comparison with the output from ein.nachsteuerbaren quartz oscillator 5 carrier signal. The phase difference corresponding output voltage is applied via a. Low-pass filter 6 is used as a manipulated variable for changing the frequency of the quartz oscillator, so that in the closed control loop a defined phase relationship between the burst phase and the latches rsignalphase sets. At the output of the quartz oscillator 5 is a continuous. Carrier signal, in frequency and phase, with the burst rigidly chained, available.

A second oscillator 7 generates a second carrier frequency signal which has a certain relationship with the frequency of the line rate sync pulses as determined by the system. For the example in Figure 1, a frequency divider in conjunction with a phase comparator 9 and a low pass is used as the closed loop and so the frequency des.spannungsgesteuerten oscillator 7 set to the η-fold line frequency exactly.

The output signal of this oscillator 7 is fed together with the continuous carrier signal from the quartz oscillator 5 to a balance modulator 11. At the output of the balance modulator are carrier-frequency signals as the sum and difference frequency of the signals supplied. By a bandpass filter 12, the Suiamensignal is selected and fed to a second balance modulator 13, which at its second input, the lazy rfrequente color signal in the given by the transmitter or from the signal source frequency position, for. B. 4,433 MHz, supplied he-holds.

To separate the brightness signals, a bandpass filter 14 is connected upstream of the balance modulator. '

At the output from the balance modulator 13, a low-pass filter 15 is used, through which only the difference signals can pass. ITach the

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Low-pass filter provides the color information transposed to the .nu.-fold line frequency. It is combined with the frequency-modulated luminance signal in a summing stage (not shown here) and supplied to the magnetic heads for recording.

FIG. 2 shows a circuit arrangement for the reproduction of the dyeing signals.

An input 1, the reproduced brightness signal is supplied with the sync signals. Bin Amplitudensieb 2 is the separation, the sync signals. In a phase-locked loop, consisting of the voltage-controlled oscillator 7 "the frequency divider 8, the phase comparator 9 and the low-pass filter 10, a carrier-frequency signal of the n-times line frequency is generated as already described. While, however, in the reception branch, z. As in a Eternsehempfangsteil as a signal source, this n-fold line frequency to a very high extent considered., The arrangement described in Figure 2 causes the caused by "GIigförmichenchaltungen fluctuations frequency and phase fluctuations of the horizontal line pulses on the voltage-controlled At the output there is a subcarrier with the η-fold line frequency available, in which the frequency and phase fluctuations inherent in the line-frequency sync pulses are also n-fold.

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The color signals recorded with n-fold line frequency have the same error as the carrier signal of the oscillator 7 ", apart from the residual error, which remains as a control deviation in the phase locked loop described.

From a high-stability quartz oscillator 16, a reference signal for the color signals transposed back to the original position is obtained and in a balance modulator 11 with the signal of the

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Oscillator 7 merged. Am.Ausgang of the balance modulator 11 turn the band-pass filter 12 is provided for extracting the sum shares «The subcarrier thus obtained is fed to a balance modulator 17, the second input of the band coming, the input 19 .zugeführt, with frequency and phase errors afflicted, receives a color signal which has been freed from other signal components by a low-pass filter 20.

At the output of the balance modulator 1.7, the sum signal and any remnants of the color signal are suppressed by a bandpass filter 18. At the output, the color signal transposed back into the original position is available with largely reduced frequency and phase fluctuations.

Despite this measure, the extensive stabilization of jittery 'color signals during playback, of. Color TV records allow residual errors to persist, which can lead to errors.

The possibility of eliminating or reducing the remaining errors is shown in the prior art.

The generation of one with the. Supporting rs through the oscillator 7 is carried out as described. In a second loop, the output from the bandpass filter 18 becomes the burst gate. 3 supplied. The separated burst pulses are compared in a phase comparison stage 21 with the output signal of a highly stable oscillator 22 in the phase * The frequency of this Ossiilators is set as closely as possible to the lorm corresponding color subcarrier frequency. The resulting from the phase comparison voltage is passed through a 'low-pass filter 23 and controls a second quartz oscillator 24 in frequency. The output signal

This oscillator is used together with the carrier signal of the oscillator 7 for generating the rücktransponierenden carrier by means of balance modulator 11 and bandpass 12. The remaining branch for transposing the color signal into the original position has already been described.

In this circuit arrangement, the second control loop is formed from stages 3, 21, 22, 23, 24, 11, 12, 17 and 18.

Bine other known design for the correction of residual errors shows Pigur 4 (Dl-OS 27 51 285, DE-AS 24 42 403).

Ss only one loop is used, but the whole way of implementation is included. To describe the interaction should be assumed by the regulated state. The output signal from the bandpass filter 18 is supplied to the burst gate 3. In the phase comparator 21, the burst pulses are compared with the reference frequency generated by the highly stable crystal oscillator 22. The phase deviation corresponding output voltage is passed through the low-pass filter 23 and controls a voltage controlled oscillator 25 in frequency at about n-fold line rate.

As described in the balance modulator 11, a new carrier signal is formed from the carrier frequency of the quartz oscillator 22 and the output signal of the oscillator 25 and freed in the bandpass filter 12 of unwanted mixing products.

If a phase deviation is detected in the phase comparison stage 21 in the burst with respect to the reference carrier of the oscillator 22, then the oscillator 25 receives a manipulated variable which leads to a change in its phase position. In the further carrier preparation, the phase position of the converting carrier (via 11, 12) is thus also changed in a counter-coupling sense. At the output of the bandpass 18, the corrected color signal is available in the original position for playback.

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To ensure a "proper function, an additional control branch is necessary, which ensures that a locking of the control loop only in a specified range," based on a multiple of the line frequency, is possible. For this purpose, after frequency division in a frequency divider 26, the comparison with the separated in the Amplitudensieb 2 line frequency signals in a frequency comparison stage 27 made and therefrom in a discriminator 28 a control variable won, the "failure to comply with the desired conditions for the" snapping "of the control loop the voltage controlled oscillator 25 outputs a correction quantity.

The circuit arrangements described in the prior art are generally still with. Devices for the detection of color signals and .required to derive the switching criteria. In the interest of low cost, different parts of the circuitry are used in both recording and playback. Both. known solutions, a relatively high effort for the switching of the functions is necessary, in particular because the function switching requires the separation of control circuits and oscillator circuits.

In practice, the switchover of the operating modes "recording" and "playback" ^{11 is carried out} by electronic switches. Assuming that the signal sources are switched over anyway in the case of the operating mode setting, it can be seen that the expenditure of changeover switches is the same "Advantage of the double utilization of individual construction stages greatly reduces.

For the combination of electronic components to integrated circuits, the reduction of the connection points is particularly important and brings next to the reduction in complexity higher reliability.

Digital features are easier to integrate

dominate as analogue functions. It is therefore desirable to use digital elements in the circuit structure to a greater extent.

Object of the invention

The aim of the invention is to provide a circuit arrangement for the compensation of frequency and phase fluctuations in the reproduction of stored color television signal, in which the cost of switches and. Connection points is minimized and largely digital elements are used in the circuit arrangement.

Explanation of the essence of the invention

The invention has for its object to avoid in a circuit arrangement to compensate for frequency and phase fluctuations in the reproduction of stored color television signals switching the phase locked loop to obtain a phase-locked with the burst carrier signal and the control criteria for the compensation of the frequency and phase errors by the Comparing the derived from the burst carrier signal with a carrier signal of high constancy to win.

According to the invention, the control criteria are used to directly influence the phase of a second subcarrier in the desired sense or to correct the initial phase of the parosignal re-transposed into the original position in the desired sense.

For this purpose, it is assumed that a circuit arrangement includes the following stages:

Sin Amplitudensieb for the sharp-part sync pulses, at whose input the BAS signal is applied, a downstream

Burst gate for the separation of the burst, to which a closed loop,. consisting of phase comparator, low-pass filter and quartz oscillator, followed, on which the output side is a rigidly chained with the burst continuous carrier signal available, also a second oscillator with the η-fold line frequency, the frequency divider, phase comparator and. Low-pass to a closed loop, is complemented, further a high-stable reference oscillator burst frequency, a balance modulator, at whose inputs bear the signals of the second oscillator and highly stable reference oscillator, a downstream band pass for the sums, a downstream second balance modulator, at its second input the color signal coming from the recording is applied via a low-pass filter, and an output-side bandpass filter whose output containing the rearranged color signal is in turn connected to the burst gate.

According to the invention, the circuit arrangement is designed so that a phase comparator is provided, on the one hand, the continuous carrier signal of the first oscillator and on the other hand, the carrier signal of the highly stable. Reference oscillator is applied, that adjoins the sum signal suppressive low-pass filter, which is followed by a the direction of the phase deviation evaluating and then a switch actuated comparator, and that the. Changeover switch, which passes pulses coming from the Amplitudensieb in counting direction forward / backward to an additionally in the zv / eite control loop frequency divider connected, applied to its connected to the balance modulator output the phase correction variable.

In a further development of the invention, the signal comparison takes place instead of the phase comparator so that two further balance modulators are provided, on which on the one hand the carrier signal of the highly stable reference oscillator and on the other hand

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to be compared carrier signal of the first oscillator once directly and. once over. Phasendrehglied abuts that these balancemodulators via a respective low-pass filter, two balancemodulators are followed, on the other hand, the rücktransponierte color signal once directly and once applied via a phase shifter - and that the outputs of these Ba- "lancemodulatoren are connected to a summation whose output is the final jerked signal

In. Modification of this arrangement, it is expedient that the output of the summing is connected directly to the burst gate .. The requirements for the control behavior of the phase locked loop are hereby lower.

Execution sb e i spi e1

The invention will be explained below with reference to exemplary embodiments.

FIG. 5 shows an exemplary embodiment with digital correction of the phase of a second subcarrier.

FIG. 6 shows an exemplary embodiment. Correction of the initial phase of the color signal transferred back to the original position.

In the embodiment of Figure 5 is to be assumed that the two self-contained. Control circuits, consisting of the phase comparison 4, the voltage-controlled quartz oscillator 5 and dem.Tiefpaß 6 and the phase comparison 9> the frequency divider 8, the low-pass filter 10, a generator 29 'and a frequency divider 30) are in the "locked" state. Ss there is phase coincidence between the output signal and the carrier signal of the quartz oscillator 5 In a phase comparator 31, the

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continuous carrier signal of the oscillator 5 with your. Carrier signal of the highly stable reference oscillator 22 compared. At the output of the phase comparator 31, the unwanted mixing products consisting predominantly of the sum signal _{r are} separated by a low-pass filter 32.

The phase criterion is given by the difference signal. In. A comparator 33 is used to evaluate the direction of the phase deviation and, depending on your condition at the output of the comparator, if a threshold value is exceeded, a changeover switch y is actuated.

The switch periodic pulses z. B. fed from the Amplitudensieb 2 and ever. after the switch has been set, it is forwarded to the input "Counting forwards" or "Counting backwards". Each individual pulse changes the phase position of the carrier at the output of the frequency divider 30 by the amount 4V ⁵ = 2 a -.

The carrier of the n-fold line frequency supplied to the balance modulator 11 likewise receives the phase step & f = 2 a · =.

At the output of the 3andpasses 12 is thus as already described for Rücktransρónnie tion required carrier signal with the phase correction variable available.

FIG. 6 shows a further exemplary embodiment. To explain the operation, let it be assumed that the phase-locked loop, consisting of the phase comparator 4, the quartz oscillator 5 and the low-pass filter 6, is in the "latched" state.

For the determination of possible frequency and phase deviations from the reference carrier from the highly stable quartz oscillator 22, two balance modulators 35 and 36 are used, to which the carrier signal to be compared is supplied once directly and once via a phase shifter 37. At the exit of the balance. modulators 35 and 36 are each a low-pass 3S or

39. From the carrier signal of the quartz oscillator 22 and a TrägerignaL. an oscillator 40, a further carrier signal is obtained in the balance modulator 11 and as already described elsewhere be after. Selection of the sum signal by the bandpass filter 12 fed to the balance modulator 17, which receives the color signal from the band at its second input.

The rearranged color signal is available at the output of the band-pass 18. Bs is the branch B-A for. Input of the burst gate 3 returned ... The frequency and phase errors still contained in the rücktransponierten color signal are taken in the phase locked loop from the oscillator 5 and used for phase comparison with the highly stable crystal oscillator 22 as described above.

The compensation of the Frequenz.- and phase error in rücktransponierten color signal takes place in the branch after the bandpass 18 by two. Balance modulators 41 and 42 in conjunction with a phase shifter 43 and a summing 44th

In the arrangement described here, the correction of frequency and phase errors is made exclusively by the modulators after the return transposition.

In a modification of this arrangement, it is expedient ,, the return of the rücktransponierten signal to the burst gate 3 not from the output of the bandpass 18 via the signal path. 3-A, but due to the output of the summing 44 the rückranansponierte Sigr.al über'den signal path C-A to the burst gate 3.

The requirements for the control behavior of the phase-locked loop, consisting of the stages 4> 5 and 6, are hereby reduced.

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In addition to this arrangement, instead of the Oszilla gate.40 for the function "recording" already existing arrangement consisting of die.Stufen-7, 8, 9 and 10 in Figure 1, 2 and 3 or "stages S 9, 10, 29 and 30 are provided in Fig. 5. By such an arrangement, two control loops are sup- portingly effective and the demands on the individual control loops are reduced.

Claims (3)

lay a B indefinite claim 1. Circuit arrangement for. Compensation of frequency and phase fluctuations "Color television signal stored during reproduction, comprising an amplitude filter for the line frequency synchronizing pulses, to whose input the BAS signal is applied, a downstream burst gate for the separation of the burst, followed by a closed control loop consisting of phase comparator, low-pass filter and a next quartz oscillator, adjoining which a continuous carrier signal which is rigidly linked to the burst is available on the output side, furthermore comprising a second oscillator with the n-fold line frequency, which via frequency divider, phase comparator and low-pass filter to a closed carrier Continuous loop is added, further comprising a highly stable reference oscillator with burst frequency, a balance modulator, at whose inputs the signals of the second. Oscillator and highly stable reference oscillator abut, - a downstream bandpass for dia cumulative shares, a downstream eten second balance modulator, at the second input of which the color signal coming from the recording is applied via a low-pass filter, and an output-side bandpass filter, whose output the rücktransponierte color signal, in turn, is connected to the burst gate, characterized in that a phase comparator (31) is provided, on the one hand, the continuous carrier signal of the first oscillator (5) and on the other hand, the carrier signal of the highly stable reference oscillator (22) is applied, that adjoins the sum signal suppressive low-pass filter (32), the one evaluating the direction of the phase deviation and then a Switch (3 ² O actuated comparator (33) is connected downstream, and that one of the Amplitudensieb (2) in the count direction forward / rückv / arts via the switch (3 ^) impulses coming, in the second control loop switched frequency divider (3.0) on the output side has the phase correction amount and with the Ba Lancemodulator (11) is connected. - 15 - 239898 6 2. Circuit arrangement according to item 1, characterized in that two further Balancetaodulatoren (35; 36) are provided, on which on the one hand the carrier signal of the highly stable reference oscillator (22) and on the other hand, the carrier signal to be compared of the first oscillator (5) once directly and once over a phase shift element (37) is applied, in that these balance modulators (35, 36) are each followed by two low-pass filters (38, 39), followed by two balance modulators (415, 42) on which, on the other hand, the rearranged color signal is applied directly once and once through a phase shift element. (43) is applied, and that the outputs of these balance modulators (41 j 42) with. a summation stage (44) are connected, at whose.Ausgang the final rückransponierte signal is applied. 3. Circuit arrangement according to item 2, characterized in that the output of the summing stage (44) is connected directly to the burst gate (3). For this C sheet drawings