DE2840969C3 - Recording and playback device for SECAM color television signals - Google Patents

Description

Recording and playback devices or video tape devices with helical scanning have recently become known and have come into practical use making use of the azimuth effect. More precisely, at In a television tape recorder of this type, the magnetic gaps are used for recording and playback Adjacent tracks serving magnetic heads arranged in different directions, so that when playing back one track (hereinafter also referred to as the main track) the playback or Interference from the neighboring lane is suppressed to a minimum, even with simultaneous scanning.

In the case of the conventional video tape recorder used for recording and reproducing the composite color television signal, the signal to be recorded is separated into a luminance signal component Y ' and a chrominance signal component C , as shown in FIG. la is indicated by a broken line. The luminance signal! "is subject to angle modulation (for example frequency modulation), while the chrominance signal component C is subjected to a frequency conversion into a signal C" of a lower frequency band or frequency range (60 to 700 kHz) and superimposed on the modulated luminance signal Y 'is recorded as shown in FIG. Ib is shown.The modulated luminance signal with high frequency or shorter wavelength (for example 3.8 to 4.8 MHz) is practically immune to interference from the neighboring track, which is due to the azimuth effect, which can be mathematically defined as follows:

sin

ITW

tan Θ

wherein
La
θ

λ w

Azimuth loss

Azimuth angle between the magnetic heads

Wavelength for the recording
Width of a track

immilconnArutnr (7Δ. \ iinrl

TVireoKalttirinr / 7 * ϊ \ a.

understands, the reproduced chrominance signal component the phase comparison with the The output signal of the frequency divider (45) is made by the phase comparator (46), wherein the frequency divider (45) for dividing the output frequency of the voltage controlled oscillator (44) can be actuated, the output signal

In the case of the chrominance signal converted to the lower frequency band, on the other hand, a satisfactory Protection against interference can hardly be imparted by the azimuth effect, especially if the

Avimiitwmlrpl klpin is. In the case of the NTSC television

stems has been provided to convert the chrominance signal converted to the lower frequency band into frequency entanglement to be recorded between the adjacent recording tracks and that at the Reproduction of the chrominance signal obtained from the neighboring track by using a comb line filter to be eliminated, as is the case, for example, in the DE-OS

24 36 941 is described. However, in the case of the SECAM television signal, the use of the comb line filter to remove the interference encounters difficulties for the following reasons. Since the frequency-modulated color difference signals BY and RY with center frequencies of 4.25 MHz and 4.406 MHz are superimposed on the luminance signal Y in its high frequency band in line sequence, it becomes very difficult to determine the phase correlation of the FM carriers between the neighboring tracks in the method using the comb line filter to achieve, whereby the elimination of the stray interference becomes impossible.

In a known magnetic tape recording and reproducing device for SECAM color television signals Initially mentioned type (DE-PS 19 02 740) is through the use of the frequency divider and the frequency multiplier for the frequency conversion basically already the advantage of one over one Frequency conversion according to the heterodyne method significantly reduced the bandwidth of the frequency-reduced bandwidth Reached chrominance signal component, which is explained in detail in the description below However, the known device leaves the difficulty also explained in detail below completely disregarded the fact that the blanking gaps of the chrominance signal component cause noise interference will.

In contrast, the invention is based on the object of a magnetic tape recording and reproducing device for SECAM color television signals of the type mentioned to the effect that by the Blanking gaps in the chrominance signal component caused interference is effectively eliminated

According to the invention, this object is achieved by the characterizing features of claim 1

In the following description, the invention is based on exemplary embodiments in comparison to State of the art explained in more detail

Fig. La and Ib spectral diagrams of one with one Video tape recorder of known and conventional type recorded video signal,

F i g. 2 is a block diagram to illustrate the general structure of a recording and reproducing device according to one embodiment of the invention,

F i g. 3a to 3d recording spectral diagrams to illustrate the principle of the invention,

F i g. 4 is a block diagram to illustrate the general structure of a recording and playback device; in which the frequency conversion of the chrominance signal is carried out solely by frequency division will,

F i g. 5a and 5b representations of the level and the frequency of the interference from a neighboring track conditional demodulated overlay,

6 shows a diagrammatic representation of the arrangement of a horizontal synchronizing signal and a chrominance signal in a recording scheme on a magnetic recording tape,

7 shows a block diagram to illustrate the according to the teaching carried out by the invention, the energy conversion of the chrominance signal,

F i g. 8 the characteristics of a bell filter for the SECAM color television signal,

9 shows a waveform diagram to illustrate a frequency division according to the invention,

Fig. 10 is a block diagram of means for eliminating interference and to eliminate similar unwanted waveform diagrams for blanking period processing

Components during the blanking period of the chrominance signal according to the invention,

F i g. 11 an embodiment of a frequency multiplier, which is used according to the teaching conveyed by the invention,

Fig. 12 shows a frequency multiplier with phase locked Loop used in another embodiment of the invention,

Fig. 13 is a waveform diagram showing the operation of the frequency multiplier shown in Fig. 12;
Figures 14, 17 and 19
Illustration of
of the chrominance signal,

15, 16 and IS block diagrams of means for Generating a blanking control signal to perform blanking processing of the chrominance signal,

F i g. 20 shows another embodiment of the means for generating the blanking control signal,

Fig. 21 is an explanatory waveform diagram the mode of action of the in F i g. 20 means shown,

Fi g. 22 is a schematic representation of another Embodiment of the means for eliminating the blanking interference of the chrominance signal,

23 shows a circuit diagram of a clipping circuit as part of the embodiment shown in FIG. 22, F i g. 24 is a waveform diagram showing the operation of that shown in FIG Embodiment,

jo Fig. 25 a further embodiment of the invention, in which the frequency multiplier is designed in the form of a phase-locked loop structure,

FIG. 26 shows a modification of that shown in FIG Embodiment,

j5 Fig. 27 is an illustrative waveform diagram the mode of action of the one shown in Fig.25 Arrangement,

F i g. 28 is a spectral diagram for explaining a method for recording the chrominance signal, which is not subject to the influence of interference from a neighboring lane,

F i g. Fig. 29 is a block diagram showing the general arrangement of a video tape recorder according to still another Embodiment of the invention and

Fi g. 30 a modification of the arrangement of FIGS. 29

From Fig. 2 of the drawings it can be seen that a

Input terminal 1 is provided to which an input signal can be fed, which is magnetic recorded and played back. In which

Ή) is the input signal for the device according to the invention it is a composite color television signal in the SECAM system. The signal applied to the input terminal 1 is passed through a low-pass filter 2 and a Bandpass filter 3 separated into a luminance signal component and a chrominance signal component The luminance signal obtained is frequency modulated by a frequency modulator 4 and then fed to a mixing circuit 6 via a high-pass filter 5 to remove the low-frequency components.

In contrast, the modulated chrominance signal obtained by frequency conversion of the color difference signals RY and BY in a line sequence is amplitude limited by an amplitude limiter and is then passed to a frequency divider 7, which is used to reduce the frequency of the input modulated signal, for example by half. The frequency-modulated signal C 'from the frequency divider 7 is also a

Frequency converter 8, for example a push-pull modulator, and is subjected to frequency conversion by the output frequency signal of a carrier generator 9. The output of the frequency converter 8 is then passed through a low-pass filter 10, whereby a modulated chrominance signal C "with a frequency in a desired lower frequency band is obtained. The chrominance signal output of the low-pass filter 10 with the lower frequency is then used to superimpose the frequency-modulated luminance signal Y ' (FM ) given in its lower frequency band side to the above-mentioned addition or mixing circuit 6. The sum signal of the luminance and chrominance signal components generated by the mixing circuit 6 is sent to magnetic heads U and U ', the magnetic gaps of which are designed so that they are used in an azimuth effect suitably have different angles, so the sum signal is recorded on a recording medium such as a magnetic tape by means of the magnetic heads 11 and 11 '.

During playback or playback operation, the signal picked up by the magnetic heads 11 and II 'is separated into the frequency-modulated or FM luminance signal Y' (FM) and the chrominance signal C converted to the lower frequency by a high-pass filter 12 and a low-pass filter 13 being provided for this purpose . The FM luminance signal V (FM) is demodulated by an amplitude limiter 14, a demodulator 15 and a low-pass filter 16 to form the original luminance signal Y ' . The demodulated luminance signal is then sent to an addition or mixing circuit 17.

In contrast, the low-frequency converted chrominance signal C obtained from the low-pass filter 13 is subjected to frequency conversion in a frequency converter 18 on the basis of the output frequency of a carrier generator 20 and converted by a band-pass filter 19 into the signal C "of a high frequency band Signal C " is multiplied by a factor of 2 in a frequency multiplier 21 and brought back to the frequency of the chrominance signal C in the original frequency band by a bandpass filter 22, whereupon the signal finally goes to the mixing circuit 17 will.

The arrangement according to the invention, in which means for reducing at least the frequency of the frequency-modulated chrominance signal component of the SECAM television signal by performing a frequency conversion or division are provided in order to described way to carry out its recording in a lower frequency band, mediates the advantages listed below.

The FM chrominance signal component of the SECAM signal has a frequency profile like that shown in Figure 3a. The color difference signal RY haX has a center frequency of 4.40 MHz with maximum frequency deviations of + 35OkHz and -50OkHz, while the color difference signal BY has a center frequency of 4.25 MHz with maximum frequency deviations of + 50OkHz and -35OkHz. Both of these color difference signals have the maximum deviation range or the maximum deviation width is 850 kHz. The carrier frequency is in the range from 33 to 4.75 MHz.

In Fi g. 3b shows a frequency profile of a frequency-modulated chrominance signal in which the Fre frequency is reduced to a predetermined low frequency value fc by the superimposition conversion known from the prior art. As shown in FIG. 3b, this frequency conversion corresponds to a shift of the frequency 4.325 MHz, which is in the middle of the maximum frequency deviation width of 850 kHz, to a desired lower frequency fc. In other words, the frequency band of the frequency band shown in FIG. 3a is converted into a low frequency band, as is the case with the techniques known for this purpose. In such a case, the elimination of the interference from the adjacent recording tracks by applying the azimuth effect is subject to considerable variation in correspondence with the change in the carrier frequency due to the large width or wide range of the maximum frequency deviation of 850 kHz, and deterioration occurs to that extent how the frequency of the signal to be recorded decreases (or its wavelength increases). To achieve an adequate azimuth effect even at the lowest frequency fet in the maximum range of the frequency deviation of the chrominance signal, as in FIG. 3b, it is therefore necessary to choose the center frequency fc at a considerably high value, which in turn means that the bandwidth of the luminance signal must be reduced accordingly. In contrast to this, the frequency of the chrominance signal is reduced to half, for example, according to the teaching conveyed by the invention. Accordingly, the maximum frequency deviation width is correspondingly reduced to half or 425 kHz, while the carrier frequency is in the range from 1.95 to 2.375 MHz. If this signal is converted to the same center frequency fc by the usual frequency converter means, as shown in Fig. 3c, the lowest frequency in the maximum range of the frequency deviation of 425 kHz is the same (fcL + 850/4 kHz), which is around 850 4 kHz above that of the figure shown in FIG. 3b converted signal shown is located and a corresponding increase of the azimuth effect to contribute the reduction of Frequenzabweichbreite or the range of the frequency deviation by the above-mentioned division 4 ^r> the frequency of the chrominance signal means the reduction of the bandwidth of the chrominance signal (the sideband width stays the same) to give the Center frequency can be increased to fc , as shown in FIG. 3d is shown, where fc> fc, which has the effect that a better utilization of the azimuth effect can be ensured. More specifically, if the frequency is reduced by half by division, a center frequency fc increased by 850/2 kHz above the center frequency fc can be obtained. The frequency division of the chrominance signal allows a reduction in the maximum width or the maximum range of the frequency deviation, which is equivalent to a corresponding reduction in the modulation index of the frequency modulation and a level reduction of the sideband signal J \ for a given FM carrier signal Jo. This peculiarity in connection with the azimuth effect can effectively prevent the appearance of the so-called inversion of the chrominance signal, which brings out the color phase discontinuity in the image areas where the color phase and color saturation vary significantly.

In the embodiment described above, the dividing ratio of the frequency divider 7 is 1/2

is set and the additional frequency conversion to the predetermined value / c is performed by way of superposition conversion. However, it is possible to reduce the frequency directly to the predetermined frequency value / c- by increasing the division ratio (for example by using the ratio 1/4). It is obvious that the above-mentioned advantages become more pronounced the larger the division ratio is set. Is the division ratio of the frequency divider set _lu 1/4 7, so the maximum range of the frequency deviation of 850kHz in the example shown in Figure 3c chrominance signal to 850/4 kHz is - decreased 212.5 kHz, the center frequencies of the color difference signals R-Y and ß - equal to 1.10 MHz or 1.06 MHz. The carrier frequency is in the range from 0.97 to 1.19 MHz. With this precaution, the azimuth loss in the maximum range of the frequency deviation (212.5 kHz) of the chrominance signal converted to the lower frequency is essentially constant and the azimuth effect is significantly improved compared to the conventional superimposition conversion technique because of the center frequency, which is on the order of 1 MHz. Thanks to the noticeably narrowed bandwidth of the chrominance signal

(850-212.5 = 637.5 kHz), which could not be achieved with the previously known method, the bandwidth of the luminance signal shown in FIG. 1b also only needs to be reduced slightly. It goes without saying that the multiplication factor of the frequency multiplier 21 must be set to four for reproduction. The arrangement shown in Figure 4 does not require a frequency converter, which is dispensable in the known prior art recording system for low frequencies undecided ^ _5, and its circuit configuration, as compared with the F g in i. 2 can be considerably simplified, while at the same time a more effective elimination of the interference from the adjacent tracks is guaranteed. In FIG. 4 are those components whose functions are the same as those in FIG. Components shown in FIG. 2 are provided with the same reference numerals as there.

Since the chrominance signal is modulated in frequency in the SECAM television system, you may occurring scattering components from the adjacent recording track from those mentioned below Established to some extent by a limiter of a frequency dc modulator of a television receiver be eliminated.

In Fig. 5, the angle φ between the main signal S and the interference component from the neighboring lane is given by the following expression:

Since the azimuth loss of the chrominance signal C that is to be recorded is suppressed to a minimum (for example worst-case fulls about -15 dB), the frequency division or conversion according to the invention applies.

(2)

Under this circumstance, expression (1) can be approximated by the following expression:

Λ φ dt

Δω ■ CcosAwt

(3)

φ - tan

ι / __CsmAjut_ \ \ l + CcosAmt J

where Δω = ωό — co _u where ωό denotes the angular frequency of the main signal, α) ι the angular frequency of the litter component from the neighboring track, 1 the amplitude of the main signal 5 and C the amplitude of the litter component.

The demodulated output - £ ■ is then given as follows:

German

d /

Cd ω (C + cosΛ ω /) C ² + 2Ccos ^ ω / + 1

(D As can be seen from the equation (3), has the demodulated beat component is the angular frequency Δω and an amplitude equal to Δω · C. In other words, the demodulated beat component is in proportional dependence on the Wir.kelfrequenzdifferenz Δω and litter level C as Under these circumstances the carrier frequency f \ of the chrominance signal of the neighboring track is selected in a preferred embodiment of the invention so that it is at least substantially equal to the carrier frequency / _{2 of} the chrominance signal of the main track, ie / i « 4 One method in which the above relationship is embodied is shown by way of example in FIG.

Referring now to this figure, there is shown a recording scheme on a magnetic tape, wherein the reference symbol "A" denotes recording tracks for the first magnetic head 11 and the reference symbol "B" denotes recording tracks for the second magnetic head 11 '. It should be noted that the adjacent signals recorded in the mutually adjacent tracks are arranged in substantially the same line order. In other words, the signals for the adjacent horizontal scanning lines on the screen of a television receiver are recorded in the adjacent recording tracks with a small offset (1.5 horizontal scanning periods in the case of the illustrated example). The horizontal synchronous positions are unmistakably in alignment with one another, as shown in FIG. 6 is shown. The chrominance signal frequencies modulated by the color difference signals RY and BY are recorded in such a manner that the condition /! »/ 2 is essentially satisfied. In other words, chrominance signals of the same type are in alignment with one another, so that in each case a signal RY (or BY) in one track coincides with a signal R-Y (or B-Y) \ n in the neighboring track and so on.

If a recording scheme like the one described above is provided, each would be simultaneous Playback from the adjacent track in playback mode only to generate a beat or overlay with a sufficiently low frequency lead to an adverse effect on the quality of the 1, as the frequencies of the main track and the secondary track are different reproduced frequency-modulated chrominance signals essentially cover one another.

As can be seen from the above description, 5 the invention provides the teaching that the color signal mixture of the SECAM television system into the luminance signal component and the chrominance signal component is to be separated, whereupon those of the angular linear

tion is subjected while the chroininance signal subject to the frequency division for stepping down to a predetermined lower frequency and the vertically modulated luminance signal for azimuth recording is superimposed on a magnetic tape on a low frequency band. So it is according to the invention possible to use the azimuth effect effectively, thereby eliminating the chrominance signal interference between to prevent adjacent recording tracks, so that the color television signal on narrower tracks can be recorded at a high density without the need to provide a protective tape. The shortcomings of the prior art heterodyne frequency conversion system for converting the frequency of the chrominance signal to a lower frequency band can be switched off within the scope of the invention, as follows should be carried out in detail.

(1) The signal in the SECAM television system generally has a wide frequency deviation range of 850 kHz and requires a wider frequency band compared to the signals in the NTSC and PAL color television systems including the Scitenband. the Efforts to limit bandwidth are pulling the Recording of the chrominance signal after conversion to a lower band frequency is carried out with the Chrominance signal transmission band a frequency three times as high as the lowest frequency of the Carrier. Under these conditions, correspondingly high-frequency side harmonics (of third harmonics) are generated during playback and in mixed with the demodulated color signal (cy component of the color bar), which leads to eye-catching disturbances

ίο causes. In contrast, the lowest is Frequency of the carrier in the case of the method according to the invention of frequency scaling by frequency division in a ratio of 1 to 4 after all to 0.97 MHz, the Side harmonics of three times higher frequency than the lowest frequency of the carrier are outside the Frequency band of the chrominance signal and so this does not cause a problem.

(4) The invention enables very reliable consistent color reproduction with an im Ver the same to the NTSC and PAL system of the Fernsehsi Signal recording and playback significantly simplified circuit structure.

The above have outlined the basic arrangements for recording and reproducing the chrominance signal

undesired reversal phenomenon, as discussed for example according to the invention. A more specific one follows the color phase discontinuity mentioned above. In contrast to the description of the application of the invention

This allows the chrominance frequency to be scaled down by converting it to the lower frequency according to the invention a narrowing of the bandwidth of the chrominance signal including the sideband, without having to reckon with the possibility of undesired reversal phenomena.

(2) In the case of a video tape recorder using a recording and playback system without a guard tape, where azimuth heads are provided, there is a problem of interference from interference the neighboring lanes. Since the carrier for the chrominance signal in the case of the SECAM television signal is in the Frequency is modulated, it should be noted in this context that it is not possible to reduce the interference <to to be eliminated by recognizing the peculiarity of the Correlation in the phase of the carrier served for each horizontal interval because there is an exact correlation is not given.

According to the mediated by the invention Teaching, however, is the carrier frequency for the reduced by division to the lower frequency band Chrominance signal in the range from 037 to 1.19MHz. So it is possible to reduce one the intersection from the adjacent lane, up to a satisfactory level value, sufficient azimuth effect by selecting the relative speed between the head and the magnetic recording medium, the width of the track and the azimuth angle accordingly

Furthermore, in the case of the preferred embodiment of the invention, in which the concluding horizontal or transverse sections in the adjacent tracks on the magnetic tape are assigned the same color difference signal (R- V or B-Y), as described above in connection with FIG . 6 it was already described that the superimposition frequency between the interspersions from the neighboring tracks is essentially zero, which in connection with the azimuth effect according to the explanations of the preceding (, 5 section contributes to the further suppression of the interspersed disturbances.

(3) In the case of the known method thanks to suitable method of restoring the chrominance signal energy level, embodiments of the frequency divider and frequency multiplier chers, which make up the core of the invention, and of means for eliminating the adverse influences of noise components and other undesirable components generated during playback operation the blanking period of the chrominance signal will.

Reference is now made to FIG. The modulated chrominance signal component of the SECAM signal has a certain amplitude component because a Bell filter with the in F i g. 8 is placed in a transmission channel to a good Achieve signal-to-noise ratio even with narrowband transmission and / or point interference too avoid. The color television signal having such a constitution is input to the input terminal 1 for the SECAM-Signa! given and passed through a bandpass filter, which results in the separation of the modulated chrominance signal from the SECAM signal. the The energy level of the separated chrominance signal is essentially smoothed within the frequency band by means of an inverted bell filter 24 (anticloche filter), thereby reducing the amplitude component of the chrominance signal is eliminated. It must be mentioned here that the bell filter described is provided behind the frequency modulator and that therefore the sideband is emphasized relative to the carrier, and also the lower and the upper Sideband become unbalanced as a function of the carrier frequency. Should such a signal be received before the Frequency division are shaped by a limiter circuit, so will the upper and lower Sideband smoothed and the restoration of the original energy level during playback impossible. To circumvent this difficulty, the inverted bell filter 24 is provided. The exit of the inverted bell filter 24 is shaped by a limiter circuit 25 so that fore and Trailing edges are steep, which is preferable for frequency division The frequency of the output signal of the

IO

IS

Limiter circuit 25 is by a frequency divider 7 in the manner already described above Such a frequency divider 7 can can be formed by a counter consisting of a number of flip-flops. The output signal of the Frequency divider 7 is fed to a band-pass filter or low-pass filter 10, whereby the chrominance signal] with a desired frequency in the lower Band is generated. A subsequent equalization circuit 26 serves to equalize the sidebands. the Recording equalization circuit 26 may have a characteristic similar to that of the bell filter (AnUcIoche-Fdiers) of FIG. 8 corresponds to But it is preferred that the equalization circuit has such a characteristic that the sidebands are emphasized as much as possible without considering the properties of the electromagnetic system mentioned above College mistake occurs so when playing a good signal-to-noise ratio is ensured for the chrominance signal. It should be noted that the The output of the equalization circuit 26 is fed to a mixing circuit 6

When reproduced, the signal picked up by the video heads in the form of magnetic heads 11 and U 'is used a band-pass filter or low-pass filter 13 supplied, whereby the in superposition to the luminance signal on chrominance signal recorded on a low band is separated. The chrominance signal separated in this way is applied to an equalization circuit 27 for reproduction, the circuit structure of which is reversed to that of the equalization circuit 26 for the recording, and the signal is substantially smoothed in energy level within the frequency band. The output of the Equalizer circuit 27 for reproduction is formed by a limiter circuit 28 so that it has a steep Receives leading and trailing flanks. The output of the limiter circuit 28 is thereupon in a Frequency multiplier 2t quadrupled, the output signal of which is in turn passed to a bandpass filter 22 whereby the desired signal component is extracted. The output of the band pass filter 22 is via a bell filter 29 with the same characteristic (Fig. 8) as the bell filter for the SECAM signal passed and finally goes to a mixing circuit 17. In this way again becomes that Chrominance signal with the original energy with a good signal-to-noise ratio preserved, without prejudice the fact that the frequency modulation range is reduced by the frequency division

Next, some embodiments of the frequency divider 7 and the frequency multiplier 21 will be discussed to be discribed.

The frequency divider 7 can be constructed from flip-flops, as has already been mentioned. Let it be on Fig. 9, it can be seen that the chrominance signal output of the inverted bell filter 24 includes horizontal blanking periods and chrominance signal margins as shown at (i)

25th

JO Fi g. 9 arises in the course shown at βj. In this way, the desired frequency division or reduction can be carried out (in the illustrated embodiment in a ratio of 1 to 4). In this connection it should be noted that the signals (k) and (I) subjected to frequency division only have the levels "0" and "1" and do not include an average level X. As a result, the levels Sa and Sa of signals (k) and (I) are either logic "1" or "0" during the horizontal blanking period. In Figure 9, the level S _A and Se ün logic state "0" are shown is such a signal (k) or (I) passed through a low pass filter, a band pass filter or the equalizer circuit 26 for recording, so the energy is a function of the Frequency increased or attenuated, which has the consequence that the signal level Sa or Sb is subject to considerable fluctuations and assumes different values.In addition, due to the differentiating characteristics of the video heads in the form of magnetic heads 11 and 1Γ on the leading and trailing edge of the signal level Sa or Sb, there is an upper oscillation caused, the modulation noise being mixed with the level S _A or Sb during playback. These undesired signal components are consequently amplified during the reproduction by the limiter circuit 28, so that disturbances are generated in the horizontal blanking period which are mixed with the reproduced luminance signal. These disturbances are then associated with various disadvantageous influences, for example with incorrect actuations in the synchronous separation or in the color lock mode, with image fluctuations and color phase discontinuities in a color television receiver. In order to eliminate these deficiencies, the interference is eliminated by a blanking control signal in the manner described below, while the horizontal blanking signal is kept at an intermediate level Sb · , as shown in FIG. 9 is shown at f / »J.

There are numerous and quite different provisions for forming the frequency multiplier 21 conceivable, such as the extraction of a harmonic component from the reproduced chrominance signal alone or in combination with a superposition frequency conversion, a square modulation or the use of a phase-locked loop. In Fig. 10 there is shown a frequency multiplier 21 which operates on the basis of the extraction of a harmonic component in connection with the heterodyne conversion. Here is a circuit for Extraction of a harmonic with a frequency three times as high as that of the reproduced chrominance signal carrier formed by a bandpass filter 39, while a circuit for extracting a fundamental wave component by a low-pass filter 38 is formed. The low-pass filter 38 and the band-pass filter 39 are combined with a frequency converter 40 in such a way that the band-pass filter and a bell filter circuit 41 produce a chrominance signal of four times as high Frequency as that of the recorded and accepted

50

obtained at (j) . The frequency divider 7 can be designed so that it operates at a pulse signal level which is higher than the central axis X, so that the pulse frequency is divided by a factor of 2 by a flip-flop of the frequency divider 7. This results in the output signal of the curve shown at (k) , which is again divided by 2 by the other flip-flop of the frequency divider, whereby the signal with the in Circuit construction will provide a better signal-to-noise ratio of the frequency-multiplied chrominance signal ensured

In Fig. 11 is a further embodiment of the Frequency converter shown by a circuit with

quadratic characteristic is formed. If that

Input signal is represented by f ^ , which is in a

simplified form equals cos ωί, so it is

P. ° 25 will be? In Swis! nut de ™! in F! °. 9 ^h0 ü6ü Chromir.anzsi ^ nals get :! will. By, this: -J

Output signal / o <y of the frequency converter 40 as follows to express:

fills ~ JiUl 'JiU}

= cos ² ot

- - (1+ cos 2 Wf)

The amplitude term of the above equation represents the signal of the doubled frequency and does not contain any Fundamental wave component. To carry out the multiplication by 4, two stages of a frequency converter 40 can be connected in cascade. The frequency converter 40 can for example consist of a push-pull modulator.

In Fig. 12 is the direct frequency multiplication shown by a phase-locked loop. In this figure, reference numeral 46 is a phase comparator denotes, with the reference numeral 47 a filter, with the reference numeral 44 a voltage-controlled oscillator and with the reference numeral 45 a frequency divider. The signal applied to an input terminal is considered in terms of the Phase compared by the phase comparator 46 with the output signal of the frequency divider 45 and the output of the phase comparator 46 is passed through the filter 47 to the voltage-controlled oscillator 44 given to control its oscillation frequency. The output frequency of the voltage controlled oscillator 44 represents the output of the multiplier circuit and is subject to frequency division by the frequency divider 45. The output signal of the frequency multiplier is consequently in phase with that on the Input signal given input terminal and its frequency is multiplied to a value which is determined by the division ratio set on the frequency divider 45. The in The frequency multiplier shown in Fig. 12 has the circuit construction of a phase locked loop (PLL).

Fig. 13 shows the waveforms for the input and output signals of the frequency multiplier shown in Fig. 12, assuming that the frequency is to be multiplied by two. In the figure, the input signal is shown at (^, while the signal appearing at the variable- frequency voltage-controlled oscillator 44 is shown at (p) frequency-multiplied output signal without generating any amplitude fluctuations, as can be seen from the waveform (p) . Even if the input signal level should be temporarily lowered or reduced to zero during playback due to a failure or similar reasons, a possible deterioration in the color phase on the control screen can be counteracted or prevented.

uiiu uau

uig rai uifuauiai au ι

Control screen deteriorates, regardless of amplitude fluctuations or the temporary absence of the input signal to be reproduced. The means will now be described which are used to generate a blanking control signal for the Case that a circuit for processing a blanking noise in the recording channel and / or the Playback channel for the chrominance signal is set. Referring to Fig. 10, it should be noted that the chrominance signal obtained from the SECAM input signal through the inverted bell filter and bandpass filter 30 is maintained at a constant level by an automatic chrominance control circuit 31, shaped by the limiter circuit 25, and frequency divided by the frequency divider 7 will. The frequency of the chrominance signal output of the frequency divider 7 is converted simultaneously with the energy conversion to a level suitable for recording by the recording equalizer and the low-pass filter 32 to a low frequency band. A gate circuit 33 serves to eliminate the blanking noise. The chrominance signal output of the gate circuit 33 is then recorded by the magnetic heads 11 and 11 'on the recording medium after mixing with the luminance signal has been carried out by the mixing circuit 6. The chrominance signal output A (see also FIG. 14 at A) of the automatic chrominance signal circuit 31 also goes to an envelope demodulator 34, the output (B, FIG. 14) of which is the blanking control signal which is fed to the frequency divider 7 and a delay circuit 35 . If the blanking control signal of the envelope demodulator 34 does not go to the frequency divider 7 as an input, it should be noted in this context that its output then corresponds to the in FIG. 9 has the course shown at (^, where the blanking level S _A or Sb is either a logic "I" or "0." The blanking control signal B appears as the input of the frequency divider 7 at the reset connections of the flip-flops, which can form the frequency divider 7, for example whereby the pedestal level is constantly held at _Yl a predetermined value, either "1" or "0". is There is also the alternative possibility that Austaststeuersignal ßzur continuous adjustment of the level Se of the output signal (Sb "0" or "1" , as shown in Fig. 9 at /) of the frequency divider 7 to the mean level value Sb shown in Fig. 9 at (m) with the aid of addition or subtraction means Blanking control signal, as shown in Fig. 14 at C, which is used to control the gate circuit 33 in the sense of eliminating the blanking noise. The gate circuit 33 is used to eliminate an undesired component, which is possibly generated as a result of a non-uniform energy distribution in the recording equalizer and low-pass filter V) 32. It is therefore possible to carry out the blanking control process on the frequency divider 7 without the delay circuit 35 and the gate circuit 33, or vice versa.

During playback or playback operation, the playback signal taken from γ, the video heads in the form of magnetic heads 11 and 1Γ, is sent to the low-pass filter 36 serving as a playback equalizer, whereby the chrominance signal of the lower frequency band is taken and converted into a signal with a flat profile of the energy distribution. The reproduced

the automatic chrominance control circuit in the form of the automatic gain control circuit 37 is processed so that it shows a constant amplitude change - (, 5 tion, and is then shaped by the limiter circuit 28, by the frequency multiplier 21 translated or multiplied in frequency and then the bandpass filter and the bell filler

circuit 41 to restore the original chrominance signal. The blanking noise component of the chrominance signal thus obtained becomes eliminated by a gate circuit 43 which is controlled by the blanking control signal £ generated by the envelope demodulator 42 (see also FIG. 14).

In the circuit arrangement shown in Fig. 10, the blanking control signal is obtained from the means for demodulating the envelopes of the chrominance signal. To the To achieve a stable envelope demodulation, the energy distribution of the chrominance signal must be smoothed, the amplitude component also has to be reduced

In Fig. 15, another embodiment is one Circuit shown, which is used for more stable generation of the load control signal

In the arrangement of FIG. 15, the output signal of the envelope curve demodulator 34 (or 42) is applied to an input terminal of an AND gate 53, while a composite synchronous signal with the one shown in FIG. 14 or 17 is given to the input terminal 50 provided for this purpose and consequently to two delay circuits 51 and 52. The delay circuit 51 is used to delay the mixed sync signal by a period of time (from a few μββΰ) to 2 ¹ } at the beginning of each horizontal scan of the chrominance signal shown in FIG. 14 at A or a period of time slightly delayed over the initial part of the chrominance signal. The course of the output signal of the delay circuit 51 is shown in FIG. 14 or 17 shown at £. The signal f is applied to another input terminal of the AND gate 53.

The delay circuit 52 serves to delay the mixed synchronous signal by a period of time corresponding essentially to a single horizon; valley scan period at the end of each horizontal scan of the figure shown in FIG. 14 chrominance signal shown at A. The course of the output signal of the delay circuit 51 is shown in FIG. 14 or 17 at F , and this signal is applied to a further input terminal of the AND gate 53. The AND gate 53 thus has three input connections to which the signals B, E or Ferschcinen, and an output connection which supplies the blanking control signal with the curve G shown in FIG. 14, which the frequency divider 7 and / or -r, the frequency multiplier 21 is received.

Reference numeral 35 denotes a delay circuit which generates a blanking control signal, the pulse width of which is larger than that of the signal G, so that the delay time caused by the equalizing circuit in the form of the low-pass filter 32 is detected. The signal H has the level "0" during the interference suppression period.

In connection with the use of the output signal « B generated by the envelope curve demodulator 34, as was discussed with reference to FIG. 15 (or will be explained below in connection with FIG. in which the chrominance signal is missing cannot be processed with the aid of only the signals £ t> o and F , although the horizontal blanking processing can be carried out with the two signals. If signal B is used, the interference in such an area must be eliminated. Processing of that area b5 of the vertical blanking signal in which the chrominance signal is missing is of course possible by using the output of the envelope demodulator 34 together with the signals and F, while the envelope modulator 7 is blocked in the horizontal blanking period.

Another embodiment of the circuit for applying the blanking control signal is shown in FIG. 16. Here too, the aforementioned output of the envelope demodulator 34 goes to the AND gate 53. The mixed synchronous signal fed to the input terminal 50 is fed to the delay circuits 51 and 52 for generating the signals £ and F already mentioned. The signal £ represents the blanking control signal for the frequency divider 7 and is used to suppress interference during the period from the horizontal sync signal to the beginning of the chrominance signal. The other signal F with a duration corresponding to the time interval from the end of the horizontal scanning of the chrominance signal to the horizontal synchronizing signal goes to the AND gate 53. In addition, the composite synchronizing signal is fed to a further delay circuit 54, which generates the pulse signal / shown in FIG Detect the low-pass filter 32. The AND gate 53 generates the logical product of the input signals £, Fund /. The output signal of the AND gate 53 shown at H in FIG. 14 serves as a blanking control signal for controlling the gate circuit 33 (or the envelope curve demodulator 34) to remove the blanking noise. It should be noted that the waveform diagram of FIG. 17 are enlarged reproductions of the relevant signal profiles in FIG.

18 is another embodiment of the circuit for asserting the blanking control signal and Fig. 19 shows the waveforms of the signals in the circuit of FIG. 18 processed signals.

The output signal of the envelope demodulator 34 (signal B) is applied to a gate circuit 57. The output signal B is shown in Fig. 19 in field frequency.

The PG pulse signal / of 25 Hz, which is synchronized in phase with the rotary movement of a head drum, is applied to the input connection 55 provided for this purpose and thus to the delay circuit 56, which can be formed by a monostable multivibrator which is applied to the front and capable of addressing the trailing edge of the signal /, thereby generating a pulse signal K having a pulse width sufficient to detect a vertical blanking period. The signal K is applied to the gate circuit 57 together with the signal B , whereby the output signal L is generated which remains at the logic signal level "1" for the duration of the chrominance signal and assumes the logic level "0" during the blanking period. The signal L is applied to the AND gate 53 in place of the signal B in FIGS. 15 and 16, whereupon the output of the AND gate 53 serves as a blanking control signal.

In Fig. Figure 20 is yet another embodiment of the circuitry for generating the blanking control signal shown and FIG. 21 shows the waveforms in the circuit of FIG. 20 processed signals.

A component with the profile O, which has been separated from the synchronous signal mixture with the profile M applied to the input terminal 58, is separated into a horizontal synchronous signal of the profile P and a vertical sync signal of the profile Q

by a Horizontalsynchronsignalseparator 59 and a Vertikalsynchronsignalseparator 60. The abgeirennte horizontal synchronizing signal is applied to a Horizontaiaustastsignalgenerator 63 and a gate circuit 62, while the separated vertical synchronizing signal approching a gate control circuit 61, which can be provided in response to the leading edge of the vertical sync signal Q and which can be reset When the count in a horizontal sync signal counter 66 reaches a predetermined value, the horizontal sync signal of the course P from the horizontal sync signal separator 59 is converted into the signal of the course 5 by the gate circuit 62 under the control of the output signal R from the gate control circuit 61. Then the signal S is converted to the horizontal sync signal counter The horizontal synchronizing signal counter 66 generates output signals at the times which correspond to the beginning of the identification signal ID, its end or the end of the vertical blanking period for the color component, whereupon a signal of the course T is generated by a matrix circuit 67. The lower Pegelintervati of the blanking signal U corresponding to the blanking interval of the Chrominanzsignalkomponcnte, as shown in Figure 21 with N the inverted signal of the curve T and the output signal P from the Horizontalaustastsignalgenerator 63 are logically processed by the NOR gate 64 so that at one Output terminal 65 the blanking signal U appears. The horizontal synchronizing signal counter 66 is set so that the output signals are generated on the seventh, fourteenth and twenty-third lines of the odd fields and on the 320th, 329th and 336th lines of the even fields in the individual frames. The above identification signal ID is an index signal formed by frequency modulating a trapezoidal pulse signal which identifies the chrominance signal line of the SECAM color television signal and is on the seventh to sixteenth lines (odd field) and 320th to 328th lines (even field) in the vertical blanking period appears. A simple example of the blanking processing circuit is shown in FIG. 22, while that of the circuit of FIG. 22 processed signals in FIG. 24 are shown.

During recording (or reproduction) the output of the bandpass filter 3 (or 19) or, alternatively, the output of the inverted bell filter 24 (or the equalization circuit 27 for reproduction), shown in FIG Chrominance control circuit 31 (or the automatic gain control circuit 37) given. It is assumed that the chrominance signals of all of these output signals include a noise such as that shown in Fig. 24 at q. A clipping circuit 69 serves to remove the blanking noise from the chrominance signal. As shown in Fig. 23, diodes Dt and D _{2 are connected} in parallel in the signal line, and the output terminal of the diode circuit is grounded through a resistor. The signal r. from which the noise is removed is fed to a limiter circuit 70 which serves to remove fluctuations in the amplitude, to adjust the leading and trailing edges of the signal r and to generate the output signal s. The signal s is applied to the frequency divider 7 (or the frequency multiplier 21).

The above-mentioned method can be used in right

easily perform and is useful for eliminating a noise component of moderate or smaller in size. The noise can be suppressed to a significant extent by reducing the The cut-off circuit and the limiter circuit are provided in several stages

A phase locked loop frequency multiplier in which blanking processing is combined with frequency multiplication is shown in FIG. 25 shown

ίο With reference to this figure it should be noted that that the reproduced chrominance signal is compared in phase with the signal of a frequency obtained by dividing the output frequency of the variable frequency voltage controlled oscillator 44 is obtained by a frequency divider 45, the phase comparison being carried out in a phase comparator 46. The resulting phase difference signal is then placed on a clamping circuit 72 via a low-pass filter in the form of the filter 47 The frequenzvaria ble voltage controlled oscillator can through the

Output of the clamp circuit 72 controlled

which in turn are made by the blanking control signal a clamp pulse generator 73 is controlled.

The chrominance signal does not appear all the time, but

there are empty periods inserted at predetermined time intervals. So will such an intermittent signal on a phase-locked oscillator as shown in Fig. 12, the output signal frequency of the oscillator becomes during the Empty period irregular, with the result that at the beginning of the sampling period of the chrominance signal immediately after the end of the empty period a considerable time is required to restore the phase synchronization. This deficiency can be remedied by providing the clamping circuit 72 and the clamping pulse generator 73, as shown in FIG. The signal curve diagram of FIG. 27 shows the chrominance signal to be reproduced at V , the output signal of filter 47 at W, the output signal of clamping circuit 72 at X and the output signal of clamping pulse generator 73 at Y and 77 and between the times 78 and 79 at which the chrominance signal is blanked, the output signal of the filter 47 can assume different values, a random frequency output of the frequency multiplier inevitably coming into play. The phase alignment must be restored immediately after the end of the idle period. Since the

• u) Clamping pulse generator 73 is provided, which is able to generate a clamping or hold pulse during the idle period, as shown in FIG. 27 shown at Y , the output of the filter 47 is in the form shown in FIG. 27 in a manner shown at X in a predetermined manner

, 5 potential level locked or clipped with In other words, the reliability of the frequency multiplier is increased if the clamp circuit 72 and the clamp pulse generator 73 are added are provided.

The idle level can be set to zero by using the phase comparator 46 accordingly However, it is inevitable that the phasing process should be performed immediately after the Leei period becomes unstable.

The clamp pulse generator 73 is constructed so that it generates the pulse output during the entire idle period. This means that the output of the Clamping pulse generator 73 the above-mentioned output

represents control signal

In the case of the embodiment shown in FIG the blanking processing is done in the phase-locked loop. As, however, FIG. 26 shows it is possible, the output of the variable frequency voltage controlled oscillator 44 via a gate circuit 75 to be controlled by the blanking control signal of a gate pulse generator 74, which have the same structure can like the clamping pulse generator 73 in Fi g. 25. The circuit arrangement of FIG. 25 with that of Fig. 26 can be combined so as to make the frequency multiplying operation more stable or reliable.

As a design example for the above-described embodiments, it should be mentioned that a record Without protective tape at high recording density could be done with a video tape recorder with helical scanning, the two magnetic heads with an azimuth angle of ± 6 °, the relative speed being 4.8 m / sec, the tape speed 23.4 mm / sec, the track pitch 48.6 μΐπ, the head width to 48 to 60μηι and the Frequency modulation range of the luminance signal to 3.8 to 4.8 MHz.

If the track pitch is narrowed, the signal-to-interference ratio deteriorates proportionally. If this problem is to be remedied, the following modification can be envisaged within the scope of the invention. As a means of reducing the influence of interferences from the neighboring tracks, even in the case of recording without the use of guard bands, it makes sense to choose a high value for the azimuth angle. However, an azimuth angle that is too large leads to azimuth splitting in the event of positional deviations from the track, which gives rise to problems such as fluctuations in the image and a deterioration in the signal-to-noise ratio due to the reduced effective relative speed between the track and the head. As a second measure, the possibility can be considered, the chrominance signal, which has a small azimuth loss (due to the recording with a relatively large wavelength), in a track A (see FIG. 6) as a chrominance signal Ci (with intermediate carrier frequency fg and fs) to record after the frequency of the chrominance signal is converted to a first lower band, while recording in the adjacent track B as a chrominance signal Ci (with subcarrier frequency / «" and / β ") after the frequency of the chrominance signal is converted to a second lower band is converted, as shown in FIG. 28 shows the bandwidth of the chrominance signals C 1 and C ₂ is chosen so that no mutual superposition occurs, although a partial superposition is permissible. More precisely, since the bandwidth of the chrominance signal usually amounts to 1 to 1.2 MHz, the sum of the bandwidths for the first chrominance signal Q and the second chrominance signal C ₂ is 2 to 2.4 MHz. Since the frequency-modulated luminance signal / j and Λ in a conventional video tape recorder is in the frequency range from 3.8 to 4.8 MHz, i:> t the bandwidth of the luminance signal is noticeably reduced in such a case To restore the luminance signal to its original state, fs and Λ be 4.8 MHz and 5.8 MHz, respectively. Thus, in the case of a VTR for high density recording, the signal-to-noise ratio deteriorates and reversals occur appearance of the luminance signal. When the above frequency conversion system, however, combined with the inventive recording method, in which the Chrominanzsignalfrequenz is by Frequenztei- <i lung lowered, so it is possible to provide a video tape recorder, which is suitable for making a high-density recording, the luminance signal band of the previously assumed bandwidth corresponding to or slightly narrower

can do.

Let us now refer to FIG. 29 referenced, it should first be noted that the to be recorded SECAM signal is given to the input terminal 1. The chrominance signal C is from there via a

Bandpass filter for 3 is obtained. The separated chrominance signal is fed to the frequency divider and its frequency is reduced by half. The output signal C "of the frequency divider 7 is fed to a frequency converter, which is in the form of a push-pull module Lators o. The like. Can be formed, and is subject to frequency conversion by an undamped wave, such as described below so as to perform the conversion through the low-pass filter 10 and a band-pass filter 85 lower frequency bands as mentioned above

2 <y , whereby the chrominance signals C \ and Ci can be obtained. The undamped wave to be used for frequency conversion can be generated in the following manner. The reference numeral 80 denotes an input terminal for a rectangular

ID gnal of 25 Hz (frame rate) that is in phase with the Rotational movement of a rotating head drum is synchronized, this signal can be formed by a pulse signal of a pulse generator that by demodulating the head drum rotation or

j5 is generated by dividing the frequency of the vertical sync signal by 2 The signal of 25 Hz is used for Control of switch assemblies 82 and 81. The switch assembly 82 go to the relevant Input connections 83 and 84 with undamped waves the frequencies f \ and fi and their mode of action is that the undamped wave of the frequency Λ for the in F i g. A track 6 shown is selected when the square wave signal of 25 Hz logical "1", while the continuous wave frequency of h for the track B (Fig. 6) is selected when the undamped wave has the logic level "0". The other switch arrangement 81, however, serves to extract the chrominance signal Ci including the subcarrier frequencies [r and / is' on the basis of the undamped wave of the

% Frequency f \ and for extracting the chrominance signal Ci including the subcarrier frequencies / * "and / β" on the basis of the undamped wave of frequency 4 The switch arrangement 81 is connected to the mixing circuit 6 around the frequency-modulated luminance signal

■> 5 gnal the output signal of the switch arrangement 81 to overlay.

The bandwidth of the chrominance signal is divided in the frequency divider 7 in the ratio 1/2 425 kHz-850 kHz / 2 step down This applies to both Chrominance signals C \ and Ci Accordingly holds the required signal bandwidth for the chrominance signals 2 to 2.4 MHz in the range from 1.15 to 1.55 MHz, which is substantially equal to the bandwidth adopted so far.

In the playback mode, the output from the video heads is in the form of the magnetic head :; 11 and W removed signal output to the low-pass filter 13 and the edge-pass filter 89, from which the chrominance

signals Ci and C _{2 can be} taken. When reproducing the recording on track A , the signal Ci is selected by a switch arrangement 90 which is controlled by the square wave signal of 25 Hz, which is synchronized in phase with the rotary movement of the rotary drum and is applied to an input terminal 91 while the signal C _{2 is selected} when the track B is reproduced. These signals Q and C ₂ go to the frequency converter 18, to which the signal of the undamped wave of the frequency f \ is selectively fed when the recording track A is played back from the input connection 87, and the signal of the undamped wave from the input connection 88 via the selector switch arrangement 86 Wave of frequency / j, whereupon the signal C "is obtained from the bandpass filter 19, the frequency of which is translated by a frequency multiplier 21 to a frequency value twice as high as that of the signal C" , so that the original chrominance signal C is reproduced, which is the M ischkreis 17 approaches.

FIG. 30 shows a change in the circuit arrangement of FIG. 29, in which different frequencies of the chrominance signal are assigned to the different recording tracks in order to eliminate the interference. 2 ¹ p

To F i g. It should be noted that the chrominance signal C to be recorded is fed to the frequency divider 7 for frequency division by the factors 8 and 4, so as to obtain the signals Si and Si of the respective reduced frequencies. The signal Si is applied to the low-pass filter 10 to generate the chrominance signal Ci, while the signal Si is applied to a band-pass filter 92 _{to generate the chrominance signal C 2.} These signals G and Ci are recorded in the relevant one of the tracks A and B via the switch arrangement 81 which is controlled by the aforementioned signal of 25 Hz which appears at the input terminal 80.

When reproducing, the chrominance signals Ci and C _{2 are obtained} from the low-pass filter 13 and the band-pass filter 93. When reproducing along track A , the signal Ci is selected by the switch arrangement 90, which is controlled by the signal of 25 Hz, while when reproducing along track B _{, signal C 2} is selected, the frequencies of these signals Ci and C ₂ are multiplied in the frequency multipliers 96 and 95 with the factors 4 and 8, respectively. The switch arrangement 94 serves to select the output signal from the frequency multiplier 95 for track A and from the frequency multiplier% for track B under the control of the aforementioned signal of 25 Hz.

Since whose frequencies are converted to different frequency bands in the in connection with Fig. 29 and 30 ^n-described circuit arrangements chrominance signals are recorded, which brought forth in the reproducing operation of interference can be eliminated readily. ^B0 is also taken over the recording scheme shown in Figure 6 in conjunction with the example shown in Figure 29 recording and playback system in which the color difference signals of the same type, so for example, the R - V signals between the neighboring *>*> tracks align horizontally, the frequency bands of the chrominance signals Ci and C ₂ know to be partially overlapped, since the high carrier frequency of the the relevant signal or the main signal accompanied by a correspondingly high carrier frequency recorded in the adjacent track ^; - 'so that practically no superposition frequency is generated.

As is apparent from the above description, the present invention provides a television tape recorder or video tape recorder capable of recording and reproducing the color television signal in the SECAM system with a high degree of reliability using narrower tracks without this the use of a protective tape must be resorted to what the mediated by the invention Teaching is to be thanked, which goes to make the recording of the chrominance signal after it Frequency was reduced by frequency division, in addition to the fact that the azimuth effect is used effectively, thereby reducing the potential of being played back over the neighboring track Noise generated in the magnetic head can be effectively suppressed, so that the generation of a stable color image is guaranteed that has no color phase discontinuities

In the above description it has been assumed that the invention is applied to azimuth recording without protective tape application. It is readily apparent, however, that the invention also applies to the previously known recording and playback system for low frequencies can be used, in which a protective tape is provided and the azimuth effect not in the sense of the creation advantageous effects similar to that described above is utilized.

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14 sheets of drawings

Claims (15)

Patent claims: 1. A magnetic tape recording and reproducing apparatus for SECAM color television signals, in which the Färbfernsehsignal in a Luminanzsignallcomponente and a chrominance signal component is divided, wherein the Luminanzsignallcomponente is angle modulated, while the chrominance signal component _lu by an at least partly by means of the frequency of the chrominance signal component by passing frequency divider taking place frequency conversion is converted into a low frequency band below the modulated luminance signal component and the two signals processed in this way are added for recording on the magnetic tape and then fed to magnetic heads in order to write closely adjacent or overlapping parallel magnetic tracks, and in which, in playback mode, a standard-compliant color television signal is replaced by an inverse Signal processing is restored, in which the frequency reconversion of the reproduced chrominance signal to the original frequency at least partly by means of a frequency multiplier 2 ¹ S, characterized in that a device (34, 35) for switching off the chrominance signal during a period of at least one blanking period of the chrominance signal is carried out in a processing path for the chrominance signal at least either in the recording channel or in the playback channel a blanking control signal generated by detecting the blanking period is provided. 2. Recording and playback device according to An r, claim 1, characterized in that the switch-off Serving device (34, 35) a device controlled by the blanking control signal for During this period of time the level of the chrominance signal is permanently switched to one has mean value of the amplitude of the chrominance signal. 3. Recording and reproducing apparatus according to claim 1, wherein the frequency divider is composed of flip-flops, characterized in that a v> is provided by the Austaststeuersignal controlled means for resetting the flip-flops and for setting the frequency divider output signal corresponding to a mean value of this output signal during the blanking period . 4. recording and playback device according to claim 1, characterized in that the chrominance signal processing channels one that is used to switch off the chrominance signal during the period of time encompassing the blanking period, Clipping circuit (69) and limiter circuit (70) charged on the output side with the chrominance signal exhibit. 5. recording and playback device according to claim 1, characterized in that a device t> o device for generating the blanking control signal an envelope demodulator (34) for the envelope of the Chrominance signal, a delay circuit (51) to delay the sync signal at least until the beginning of each horizontal scan of the b5 Chrominance signal and a delay circuit (52) for delaying the synchronous signal until the end of or just before the end of each horizontal scan of the chrominance signal (Fig. 15). 6. Recording and playback device according to claim 1, characterized in that a device for generating the blanking control signal has an envelope demodulator (34) for demodulating the envelope of the chrominance signal, and means (56) for generating a pulse signal with a width corresponding to at least one vertical blanking period from a signal with a predetermined frequency, which is synchronized in phase with the rotational movement of a drum provided with recording and playback heads, means (57) for generating a HOlI curve demodulation output signal with a duration detected by at least one vertical blanking period from the pulse signal and the signal generated by the envelope demodulation, means (51) for delaying the synchronous signal until the beginning of each horizontal scan of the chrominance signal or until a point in time shortly thereafter and means (52) for delaying the synchronous signal until the end or up to a point in time shortly before the end of the horizontal scan (F i g. 16 to 19). 7. recording and playback device according to claim 1, characterized in that the device a vertical sync signal separator (60) and a horizontal sync signal separator for generating the blanking control signal (59) to reject a vertical sync signal and a horizontal sync signal from a mixed sync signal, as well as a horizontal sync signal counter which can be actuated in response to the vertical sync signal (66), a matrix circuit (67) for generating a blanking control signal for the vertical blanking period from the output signal of the Horizontal sync signal counter (66) and a horizontal blanking signal generator (63) for generating a horizontal blanking control signal for the chrominance signal from the horizontal sync signal, wherein the vertical blanking control signal and the horizontal blanking control signal as the blanking control signal are usable. 8. Recording and playback device, in particular according to claim 1, characterized in that the recording device has a device for making the recording with mutual alignment of the locations of the horizontal sync signals to be recorded in adjacent tracks (A. B) on the recording medium, and a device for recording the identical chrominance signals representing the same color difference in horizontally aligned sections of adjacent recording tracks and a device for making the recording by video heads in the form of magnetic heads (11, 11 ') each having an azimuth angle along the adjacent tracks. 9. recording and playback device, in particular according to claim 1, characterized in that in the recording channel of the separated chrominance signal component means (24) having a the working characteristic of a bell-shaped filter is provided which is opposite to the working characteristic. such as one in the recording channel for emphasizing the sidebands of the chrominance signal with the on the lower band serving frequency first equalization circuit (26), one in the reproduction channel of the chrominance signal for equalizing the Second equalization circuit serving sidebands of the reproduced chrominance signal component (27) and a bell filter (29) with the same working characteristic as the first-mentioned bell filter. 10. Recording and playback device, in particular according to claim 1, characterized in that the frequency multiplier (21) comprises a device (40) for converting the frequency of the reproduced chrominance signal as well as the frequency of a Hannonian component extracted from the reproduced chrominance signal, the three times is as high as the frequency of the reproduced chrominance signal, to the original frequency of the chrominance signal prior to its recording (Fig. 10). 11. Recording and playback device, in particular according to claim 1, characterized in that additional means for enabling the recording of the down-banded chrominance signal provided in the adjacent tracks with mutually different frequency ranges are. 12. Recording and playback device, in particular according to claim 1, characterized in that the frequency multiplier (21) means for multiplying of the chrominance signal scaled down into the lower frequency band with itself (Fig. 11). 13. Recording and playback device according to claim 12, characterized in that one of the is deformed with each other to be multiplied chrominance signals. 14. Recording and playback device, in particular according to claim 1, characterized in that the frequency multiplier (21) a phase comparator (46), a filter (47), a clamping circuit (72), a clamping pulse generator (73), a voltage controlled oscillator (44) and a frequency divider (45) includes, wherein the output frequency of the voltage controlled oscillator (44) by the Frequency divider (45) is divisible, its output signal in terms of phase by the phase comparator (46) is comparable to the reproduced chrominance signal, the output signal of the Phase Vergletehers (46) in turn after passing through the filter (47) and through the Clamping pulse generator (73) controlled clamping circuit (72) the voltage controlled oscillator (44) can be fed to its control and thereby by the voltage-controlled oscillator (44) a frequency multiplication signal can be generated. 15. Recording and playback device, in particular according to claim 1, characterized in that the frequency multiplier (21) has a phase comparator (46), a filter (47), a voltage controlled oscillator (44), a frequency divider (45), a gate the phase comparator (46) through the filter (47) to the voltage-controlled oscillator (44) can be fed and the frequency multiplier signal thereby forming output signal of the voltage-controlled oscillator (44) over the generated by the gate pulse generator (74) controlled gate circuit (75) can be removed.