DE2738905A1 - VOTING DEVICE FOR A TELEVISION RECEIVER - Google Patents

Description

(CU, I7 «uue

RCA 71,024 / 71, O24A

Ser.No. 718.455 / 779.126

Filing Date: August 30, 1976 / March 18,1977

RCA Corporation

New York N.Y. (V.St.A.) Tuning device for a television receiver

The present invention relates to a tuning device according to the preamble of claim 1. In particular, the invention relates to an electronic voting device for television receivers that work with phase control.

Phase-regulated circuits or phase regulators can be used with advantage in many applications because they allow to synthesize or generate a signal which has a fairly accurate and stable frequency that changes easy to control. A device with phase control typically contains a reference signal source, a controlled one Oscillator, a programmable counter for dividing the frequency of the oscillator output signal by a controllable one Factor, a phase demodulator for generating one of the phase or frequency relationship between the reference frequency signal and the signal corresponding to the output signal of the controlled oscillator and a low-pass filter for generating a direct current

809810/0826

Control signal for the controlled oscillator from the output signal of the phase demodulator. Examples of such phase lock loops and its applications are in the user note RCA Sigital Integrated Circuits, Application Note ICAII 6101 "The RCA COS / MOG Phase-Locked-Loop - A I ersatile Building Block for Micro-Power Digital and Analog Applications "described, e.g. in the RCA data book SSD-2O3B (COS / MOS Digital Integrated Circuits) from 1974 is included.

Recently, because of the advantages of programmability, accuracy, and stability the use of phase regulators in tuning devices for radio and television sets has been suggested. Phase-regulated Tuning devices for television sets are known, for example, from DT-OSs 2 651 297, 2 708 232 and 2 722 659.

The components of phase-regulated voting devices must be carefully selected so that their compatibility with the associated receiver is guaranteed. For example, phase-controlled tuners generally work with a phase detector as described in the above-mentioned user communication specified type, which generates pulses with the frequency of the reference signal, the duration of which the phase and frequency relationships between the reference frequency signal and the local oscillator signal. Because the low-pass filter, which is the control signal for the controlled oscillator generated from the output signal of the phase demodulator or phase detector, the output signal of the phase detector under certain circumstances does not filter sufficiently, the control signal can be undesirably transmitted with pulses of the reference frequency be modulated. The local oscillator signal generated as a function of the amplitude of the control signal can then contain a frequency-modulated component that is used when processing the receiver may cause undesired interference in the audio or video output signals of the receiver caused.

809810/0826

For example, frequency-modulated components of the local oscillator signal that are generated by a phase control working tuning device of an FM radio receiver generated after demodulation by the demodulator of the receiver audible interference signals disturbing the listener produce. The generation of such audible interference signals in SM broadcasting or high-frequency receivers that work with a phase-controlled tuning device can be reduced by that one chooses the reference frequency of the phase control higher than the highest frequency in the audio frequency range. The disturbing ones Portions of the reference frequency that are controlled by the phase Abstinuneinrichtung are generated, then lies outside the audio frequency range and are therefore for the normal listener no longer audible.

The use of a similar measure in a television receiver, namely the reference frequency of the phase-locked Tuning device higher than the highest signal frequency used to generate the image in order to be visible Effects of frequency-modulated components caused by the phase-locked Tuning device are generated, however, is not easily possible, since a reference frequency is then used which is much higher (e.g. higher than 4.5 MHz) than the digital ones currently available for phase regulators Circuits can be processed easily.

It is also desirable, while parts of the

phase-regulated tuning device at the same time for others Take advantage of parts of the television receiver to save costs, but care must be taken to ensure that the Cost savings do not affect the operating properties of the recipient as a whole. For example, it is in the publication "A Frequency Synthesizer for Television Receivers "from Eric Breeze and employees in the" IEEE Transactiond ", November 1974, and US Pat. No. 3,980,951 suggested

8U9810 / 0826

-A-

den, a signal at the frequency of 3.58 MHz (i.e. the subcarrier frequency according to the US standard), which is controlled by a crystal oscillator of a color demodulator part of a television receiver is generated to a phase detector in a phase regulator of a tuner of the receiver to the Reduce costs for the receiver by having a separate crystal oscillator for generating the reference signal saves. However, it is advisable to divide the frequency of the 3.58 MHz signal down to a sufficiently low frequency, which is compatible with the operating frequency range of the digital circuit used in the phase regulator. The factor, by which the 3.58 MHz signal is divided should expediently can also be chosen so that visible effects of modulation components of the local oscillator at the reference frequency be suppressed if possible. It is true in the above publication by Breeze and coworkers mentions on page 262 that an additional benefit of using the 3.58 MHz color subcarrier signal as the reference signal consists in the fact that any digital interference signals that arise are coherent with the 15.75 kHz grid frequency and therefore less annoying when they become visible on the screen, for reasons that will be discussed in more detail below, however, the reference signal frequencies obtained by dividing the 3.58 MHz color subcarrier frequency as an integer are suitable can be generated, not for extensive suppression of interfering images caused by reference signal frequencies that have not been filtered out Pulse components of the control signal of a phase-locked tuning device are generated.

The present invention is based on the object of avoiding the deficiencies outlined above, that is to say in particular Image interference due to a reference-frequency amplitude modulation of the control signal of a phase-regulated tuning device to avoid.

8U9810 / 0826

In one embodiment, a phase-locked Tuning device according to the invention, which is used to generate the Local oscillator signal is used for a television receiver, which a picture by scanning a picture display device generated with predetermined sampling frequencies, an arrangement for generating a reference signal is provided, whose Frequency in such a relation to the sampling frequencies stands that the visible influences are not filtered out Component of the local oscillator signal that corresponds to the reference frequency occurs, essentially cancel each other out in the formation of the image.

The single figure of the drawing shows a block diagram of a television receiver with a phase-regulated Voting device according to an embodiment of the present invention Invention.

The television receiver shown in the drawing contains an antenna 12 for receiving high-frequency television signals and an RF part 14 for amplifying and otherwise Processing the received signals. The amplified RF signals are in a mixer 18 with generation of an intermediate frequency signal (IF signal) mixed with a local oscillator signal, which is through a phase-controlled tuning device 16 is generated. The IF signal is in an IF part 2O amplified, filtered and otherwise processed and then fed to a further circuit part 22, the color, luminance, Synchronization and color signal components generated. That The color signal and the luminance signal are fed to respective electrodes of a dildo tube 24, while the sound signal a loudspeaker 26 is supplied.

The synchronization signal component of the output signal of the IF part 20 is separated from a synchronizing signal

809810/0826

28 supplied, the horizontal and vertical synchronizing pulses from the composite signal separates. The horizontal synchronization pulses are fed to a horizontal deflection circuit 3o, which controls the horizontal deflection of the electron beams in the picture tube 24. The horizontal deflection circuit 3O delivers also a signal to a high-voltage unit 31, which generates a high voltage for operating the picture tube 24. The vertical synchronization pulses are fed to a vertical deflection circuit 32 which controls the vertical deflection of the electron beams in the picture tube 24 controls.

The parts of the television receiver described so far can be constructed in a known manner, e.g. Receiver mentioned in the publication "RCA Television Service Data, File 1975 C-IO ", published by RCA Corporation, Indianapolis, Indiana, V.St.A., for the CTC-74 device.

The phase-controlled tuning device 16 contains an oscillator 34, for example a crystal oscillator, which supplies _{a signal with a stable and precisely defined frequency f v} _, _AI. The frequency of this fixed frequency signal is divided by the factor R by means of a divider 36. The divider 36 can contain, for example, a counting circuit and supplies a reference frequency signal of the frequency f _nr , _ equal to f _vrT , .. _r / R. The value

Ktr Λ I AL

of the factor R is chosen so that the reference frequency f. is sufficiently low to be compatible with the operating frequency range of other parts of the phase-controlled tuning device 16. Furthermore, as will be explained in more detail below, the value of the factor R is selected with respect to the value of the fixed frequency f _vrT1Jvr so that the reference frequency generated

Λ 1 AL

quenz is in a very specific relationship to the horizontal and vertical scanning frequencies H and V of the receiver, so that visible effects of undesired frequency-modulated components of the local oscillator signal caused by the phase control can arise, are largely suppressed.

809810/0826

The reference frequency signal becomes an input

a phase detector 38 directly, i.e. without further frequency division, fed. The output signal of a programmable divider 46 is fed to the other input of the phase detector. The phase detector 38 generates a signal which represents the phase and / or frequency deviation between the two input signals. A typical phase detector that works for the phase locked loop or the phase equalizer or phase controller 16, provides a series of pulses whose repetition frequency is equal to the reference frequency and the duration of which depends on the phase and frequency deviation between the two input signals. A phase detector this Art is in the already mentioned user notification RCA ICAM 6061 and included in the CD4O46 integrated circuit available from RCA Corporation Somerville, New Jersey.

The output signal of the phase detector is fed to a low-pass filter 40, which it to form a Integrated DC voltage signal, the amplitude of which corresponds to the phase and frequency deviations between the input signals of phase detector 38 fluctuates. This variable DC voltage signal becomes a voltage controlled Oscillator, which serves as a local oscillator 42, is supplied to control its oscillation frequency. The output signal of the local oscillator 42 is fed to the mixer 18 and a prescaler 44 which has the division factor K.

The prescaler 44 with the division factor K contains e.g. a counting circuit that counts the frequency of the local Divides the oscillator signal by a factor K, which is selected so that the divided output signal is one with the operating frequency range of the other components of the phase controller 16 has a tolerable frequency. The value of the factor K becomes particular chosen so that the programmable divider 46

809810/0826

supplied signal has a frequency that is lower than the highest frequency that the programmable divider can process.

The programmable divider 46 divides the frequency of the output signal of the prescaler 44 by a programmable factor N, which depends on the channel that a user of the television set has set by means of a channel selection unit 48. The programmable divider 46 can contain, for example, a counter that counts one per N cycles of the input signal
Cycle of the output signal generated. The factor N is controlled, for example, by binary-coded decimal number signals which are supplied by the channel selection unit 48. The output signal of the programmable divider 46 is fed to the phase detector 48 in order to close the phase locked loop of the phase controller 16.

In operation, the control signal emitted by the low-pass filter 4O adjusts the frequency of the local oscillator signal until the frequency and phase of the output signal of the divider 36 dividing by the factor R and the divider 46 dividing by the factor N are in a predetermined relationship, ie in are essentially the same. If this is the case, the phase regulator 16 can be described as having "fallen into step" or synchronized and the local oscillator signal then has a frequency f _T _ corresponding to the following

Xj (J

the equation:

f = NKy MKP

¹ LO R ¹ XTAL ** REF (1)

In the United States of America, the values of the frequencies of the local oscillator signal calculated in MHz for the channels that can be selected by a television subscriber contain prime numbers in a range between 101 and 931,
ie numbers whose least common divisor is 1. It is

809810/0826

therefore, it is desirable that for each channel used by a television subscriber is adjustable, N is equal to the frequency calculated in MHz of the corresponding local oscillator signal. Under these conditions, equation (1) can be written as follows:

1 MHz = Kf _REF (2)

Theoretically, according to equation (2), the frequency of the local oscillator is as stable as the reference frequency. If, however, a phase detector of the type described in the above-mentioned RCA application notice ICAN 6061 is used as the phase detector 38, residues of the error signal pulses that determine the phase and frequency deviation between the output signals of the divider 36 which divides by the factor R and that which divides by the factor N represent dividing divider 46 and occur with the reference _{frequency f REF} , a frequency modulation of the frequency f _Tr . cause of the local oscillator. The reason for this is that it is difficult in practice to use the low-pass filter 40 to suppress all traces of the error signal pulses in the generated DC voltage control signal. The control signal fed to the local oscillator 42 is therefore amplitude-modulated with the error signal pulse components that occur at the reference frequency f. The amplitude modulation components of the control signal result in a corresponding frequency modulation of the local oscillator signal.

When a local oscillator signal that contains frequency-modulated components with a high frequency Carrier is mixed in mixer 18, an IF signal is generated, which can also contain a frequency-modulated component. As the conventional IF circuits, like them normally are used in the IF amplifier 20, an unbalanced, z.

809810/0826

B. falling amplitude / frequency characteristic with respect to the video carrier frequency (e.g. 45, / 5 MHz), IF signal components whose frequency is above that of the video carrier are attenuated more than IF signal components whose frequency is below that of the video carrier. The video signal generated by the IF section 20 can thus have an amplitude modulation with a frequency corresponding to the reference frequency. After processing by the video part 22, this amplitude modulation of the output signal from the IF part 20 usually produces a visible interference pattern in the picture displayed by the picture tube 24, which disturbs the viewer. As already mentioned, the visible effects of the frequency modulation of the local oscillator signal with the reference frequency f _{DI? F} are eliminated or at least considerably reduced that the reference frequency is selected in a certain relationship to the horizontal and vertical scanning frequencies II and V, respectively. The reference frequencies that can be used for this purpose are specifically given by the equation

^f REF κ H ± nV (j)

given, where η is an integer and m is an odd integer Number are. So this equation defines a group of frequencies, all of which are the sum of an odd sub-multiple (Subharmonics) of the horizontal scanning or line frequency and a whole multiple (harmonics) of the vertical scanning frequency or screen frequency. Under these circumstances, the amplitude modulation components of the video signal are canceled out the frequency modulated with the reference frequency Components of the local oscillator signal correspond, when generating the image.

The equation (3) can be broken down into a short

Description of certain aspects of the recipient's operation 10 better understand when creating a color image. That from Receiver IO generated image is formed by three im

809810/0826

substantial converging, intensity-modulated electron beams, corresponding to the three primary colors i.e. red, green and blue, in a grid pattern over a fluorescent screen be deflected on the inside of the piston of the picture tube 24. The electron beams are along alternating lines deflected horizontally while a vertical deflection takes place at the same time. Two vertical deflections or parts are required for a complete picture. During the

the odd-numbered lines are scanned one field and the even-numbered lines are scanned during the next field. This type of raster scan is commonly referred to as "interlace scan" because of the scanning of the lines of a sub-picture every other line of the picture as -Gönz is skipped. According to the television standard in the United States of America, a complete picture has a total of 525 Lines scanned at a frequency H equal to the frequency of the line sync pulses, i.e. about 15734 kHz Two fields are scanned per image with the vertical or field frequency V, which is equal to the frequency of the Vertical sync pulses, namely 2 (H / 525) or about 60 Hz.

To make the transmission and reception of color television signals compatible with black and white televisions, signal groups, which represent the color formation, are frequency-wise nested between signal groups that represent the brightness information. As a result, they take the Signals representing color information have the same frequency band like the signals representing the brightness information. So that the color signals do not have any disturbing patterns on the screen of a black-and-white receiver, it has the color signals associated carrier has a frequency which is equal to an odd multiple of half the line frequency H, while the carrier assigned to the luminance signals has a frequency

8uaö10 / 0826

has sequence which is equal to an integral multiple of the line frequency H.

Because of this relationship to the horizontal or line frequency H, which in turn is in a certain relation stands for the vertical or field frequency V, a signal that represents brightness information passes through during the scan a whole number of periods for each given line or each given sub-picture. This means that changes in brightness return in phase either in the next line or in the next subbijd and thereby become strengthen. In the case of the signal representing the color information, however, the opposite relationships exist. Since the Frequency of a signal representing color information, an odd multiple of half the line frequency H, passes through a signal representing color information a certain number of cycles plus one during a line period half cycle. When the next line of the relevant partial image is scanned, that which represents the color information occurs Signal with a phase shifted by 180 ° again. Even when scanning the same line of the following sub-image it appears out of phase. As a result of this antiphase, a cancellation effect occurs and the human eye can do not perceive an interference pattern that is based on brightness fluctuations that appear on the screen of a black-and-white receiver can be generated by a signal that represents color information, so you can also use a black-and-white receiver receive a color television signal satisfactorily.

In the United States of America the

Color subcarriers have a frequency of 3.5795 ... MHz, i.e. about 3, b8 MHz. The color subcarrier frequency is equal to 455 times half the line frequency according to the US standard, i.e. 15734.26573 ... Hz (about 15734 Hz). The image disturbances generated by the path subcarrier therefore occur very often during each line and

8üäb10 / 0826

as mentioned, they are compensated or canceled from line to line. The picture disturbances that are in a given line are generated by the color subcarrier, are thus compensated for by the antiphase image disturbances that the color subcarrier in the next line (in numerical order) in the next sub-picture. So there are, for example, the color subcarrier image disturbances in line 1 of partial image 1 due to the antiphase color subcarrier image interference in line 3 of the Partial image 1 erased.

To understand equation (3), it is important to remember that the reference _{frequency f REF} for phase-controlled television tuning devices is limited in frequency by the highest frequency that the circuit parts concerned, in particular the programmable divider circuits, such as the divider 3b, des Can process phase controller. With the circuit units currently available for phase regulators, the reference frequency should be considerably less than 3.53 MHz. Under these conditions, the periods of the interference images associated with the reference frequency are so long that several lines are scanned during the interval. In other words, the interference signals associated with the color subcarrier would cause interfering patterns in the line direction if they are not compensated, while the interferences associated with the reference frequency signal lead to interfering image patterns in the vertical or image direction of the television picture if they are not eliminated .

So in order to keep the visibility of interference patterns low, which originate from a reference frequency signal, that is compatible with components that are currently intended to be available for phase-controlled tuning devices the image interference caused by the reference frequency signal cancel from drawing file to drawing file and not from line

809010/0826

-yi-

to line like the image disturbances caused by the color subcarrier. This means that the picture disturbances caused by the reference frequency signal in a field are out of phase with the should be image interference caused by the reference signal in the next field. This can be mathematically expressed by the express the following equation:

^f REF ⁼ => ^V - Ϊ (4)

where j is any integer. The term V / 2 corresponds to that required for the cancellation of vertical interference patterns Phase reversal.

Since every integer j is always called; Sunune one

Can express the difference between two other whole numbers η and ρ ..., equation (4) can be rewritten as follows:

^f REF ^{s (} P ^{in) V} - | ^{V =} " ^nV

Because according to the television standard in the United

States V = 2H / 525, equation (5) can be expressed as follows to write:

^f REF

Do one

(2p j I) ₌ 1 b25 ^m

(7)

where m is an integer, equation (6) can be written as follows:

809Ü10 / 0826

^f REF ^{= ± n} , y + i _ΑΛΛ (8)

-μ-

which agrees with equation (3). From equation (7) it can be seen that

(2p ^± D = ψ (9)

Since (2p - 1) is always an odd number, m must be an integer Factor of 525, so m must be one of the odd numbers 1, J, 5, 7, 15, 21, 25, 35, / 5, 105, 17b or 525.

The values of m, η and K given by equation (3) are sufficient by the expression

IMHz 0 K (^ - H t nV) (10)

given, which is obtained by combining equations (2) and (3J results. Taking into account the fact that V = 2 (H / b25) equation (10) can be written as follows:

IMHz = KH (- + - | ^) (11)

If possible, K should be an integer, since factors that divide by a non-integer divisor are proportional are complex and therefore relatively expensive. Unfortunately, however, there are no exact solutions to equation (11) for the K is an integer. However, there are a number of solutions for which K is an integer and which is a reference frequency within il Hz of an exact solution in terms of frequency. Such an inexact solution can be used a complete cancellation of the interfering signals, which are based on a frequency modulation of the local oscillator signal and recur with the period of the reference frequency, do not reach, however, a considerable reduction in the interference signal, e.g. by between 15 and 20 dB, is to be expected.

81) 9810/0826

An inexact solution of equation (11), which ensures a considerable reduction in the unwanted interference signal, is given by the values m = 5, η = 17 and K = 240. With this solution, the use of a 1 MHz crystal oscillator and the choice of R = K results in a reference frequency of 4166.66667 Hz, which is 0.8325 Hz from the corresponding exact solution of equation (11) deviates. This solution is particularly useful for the following reasons: Counters used for Parts of the frequency of relatively high frequency signals are used, e.g. the oscillator signal for channel 82, which is used in the United States has a frequency of 931 MHz should contain the largest possible number of binary or flip-flop stages without a return from the output of a stage to the input of a second stage, through which the second stage after a certain Number of counting steps is reset, are connected in series. The resetting of a binary divider stage is required namely a certain time, which considerably limits the maximum operating frequency of a meter. If one for K is the number 240, you can use a counter that contains four binary levels connected in series without feedback, the divide by 16 and follow the four binary levels with feedback that divide by 15. Because the first four levels of the counter work without feedback, they can easily divide the relatively high input frequency (by 16) and one proportionately supply low frequency that can be divided by the last four stages (by 15), the operating frequency of which is limited by the feedback.

Examples of other solutions that use both allow the last binary stages or flip-flops connected in series without a feedback hold. Let these solutions in the form of a tuning device containing a phase-locked loop with a 1 MHz crystal oscillator and a value of R equal to that of K. Digs

809810/0826

-Yf-

if m = b, η = -5 and K = 344, a reference frequency of 2906.97674 Hz is obtained, which deviates by 0.11616 Hz from the corresponding exact reference frequency. For the division with 344 one can use a counter which, for example, contains 3 binary divider stages connected in series without feedback, which cause a division by 8 and to which 6 binary divider stages connected in series with feedback, which cause a division 43, follow. If you choose m right away 5, η equals -1 and K 324, a reference frequency of 3085.41975 Hz is obtained, which is 0.4933 Hz from the exact one the reference frequency given by equation (5) differs. For the Division by 324, for example, nan can use a counter that has two binary divider stages connected in series without feedback circuit that divide by the factor 4, followed by 7 binary divider stages connected in series with feedback that divide by 81.

With regard to the above-mentioned publication by Eric Breeze in the "IEEE Transactions" November 1974, where it is suggested that the reference frequency for a phase-controlled tuning device from the 3.58 MHz color subcarrier frequency derive, it should be noted that there is no integer divisor with which the color subcarrier frequency can be converted into an odd-numbered sub-multiple of the line frequency H, as required by equation (3). According to the US television standard, the color subcarrier frequency is deliberately chosen to be an odd multiple of half the line frequency, so that signal components with the frequency of the color subcarrier are not visible in the image. In other words, is 3.57954 ... Mhz divided by 15734.26573 ... Hz equals 222.5 what is not an integer. In the Breeze publication mentioned above, two reference frequencies derived from the 3.58 MHz color subcarrier frequency are mentioned: a reference frequency of 10 kHz for VHP channels is obtained by one divides 3.58 MHz by 358 (i.e. 179 χ 2) and a reference frequency of 2.5 kHz for UHF channels is generated by

809810/0826

3, b8 MHz is divided by 1432/179 χ 8). The reference frequency, which is closest to the known reference frequency of IO kHz for the VHF channels and an exact solution of the equation (3) is 9.98001982 kHz (equation (J) with m = 3 and η = 79). So the reference frequency suggested in the Breeze publication for the VHF channels is 18.7 Hz away from the nearest reference frequency that is an exact Represents solution of equation (3). In a corresponding manner it can be shown that the known reference frequency of 2.5 kHz for the UHF channels removed by 12.2 Hz from the nearest exact reference frequency which corresponds to equation (3) (Equation (3) with m = 7 and η = 4. Since the solutions to equation (3) only use the reference frequencies according to the invention mutual distances of 59.95 Hz (i.e. equal to the vertical deflection or field frequency according to the US standard) the known reference frequencies mentioned above are quite poor solutions in terms of compensation of video signal components represented by reference-frequency amplitude modulation components of the phase-locked control signal develop.

By using a phase-locked tuner with a reference frequency that is essentially is equal to one of the frequencies defined by equation (3), not only are unwanted interference patterns avoided, the originate from a reference frequency frequency modulation of the local oscillator signal, but will also do so without additional Circuit complexity reached. In practice one can even use the circuit arrangement for the phase-controlled tuning device simplify. For example, the requirements to the low-pass filter, since the suppression of interference effects by a reference-frequency frequency modulation no longer has to be effected exclusively by the low-pass filter. So you can have a simpler and

809810/0826

so use cheaper low-pass filter. In addition, can if necessary, the synchronization time of the phase control, i.e. the time required for the fully synchronized state to occur in the case of a phase-regulated Tuning device, the frequency of which is substantially equal to one of the frequencies given by the equation (3J, shorten compared to the known phase regulators. The reason for this purpose, the reference frequency of a phase-regulated tuning device is essentially the same one of the frequencies given by equation (3) can use a low-pass filter with a higher cutoff frequency than it must be used in the known phase-controlled tuning devices in order to achieve sufficient high-frequency attenuation to reach.

Blank page

Claims (12)

Claims 1 . Tuning device for a television receiver having an image display device which is scanned by a scanning device in a predetermined direction at a first scanning frequency H can be scanned line by line, a predetermined number L of scanned lines resulting in a raster and each Pairs of successive rasters are scanned at a second scanning frequency V / 2, with a controllable oscillator for generating a local oscillator signal for tuning the television receiver to a selected channel accordingly the amplitude of a control signal, further comprising an arrangement for generating a reference frequency signal, and having a Arrangement for generating the control signal, which with the arrangement for generating the reference frequency signal as well as · - the controllable oscillator is coupled and generates a control signal that the frequency and phase relationships between the oscillator signal and represents the reference frequency signal and contains amplitude components occurring with the reference frequency, characterized in that the frequency of the reference frequency signal is in such a relationship to sampling frequencies is that when the image display device is scanned, there are visible influences of video components that arise from the amplitude-modulated components of the control signal, essentially cancel out from grid to grid and furthermore is less than or equal to the highest frequency which the arrangement (38, 44, 46, 48) for generating the control signal able to process. 8U9Ö10 / 032G ORIGINAL INSPECTED 273890 -U- 2. Tuning device according to claim L, d a through characterized in that the reference frequency essentially the same jv i Iv where j is an integer. 3. tuning device according to claim 1 or 2, characterized in that the co- reference frequency essentially the same i "t η V where m is an integer factor of L and η is a is an integer. 4. Tuning device according to claim 1, 2 or 'i, characterized in that the predetermined direction is substantially horizontal. 5. Tuning device according to at least one of claims 1 to 4, characterized in that that the arrangement (38, 40) for generating the control signal is a circuit arrangement (38) for generating a reference frequency Sequence of pulses with a property that depends on the phase and frequency relationship between the local Oscillator signal and the reference frequency signal depends, contains. 6. tuning device according to claim 5, characterized in that the arrangement (38, 40) for generating the control signal contains a circuit arrangement (40) for integrating the pulse train. 809810/0826 273890b -η- 7. Abstinuneinrichtung after at least one of the preceding claims, characterized in that the arrangement (34, 36) for generating of the reference frequency signal, a source (34) for a fixed frequency signal and a circuit arrangement (36) for dividing the Fixed frequency signal by a factor R contains. 8. tuning device according to at least one of claims 1 to 5, characterized in that the signal from the local oscillator (42) to a Circuit arrangement (44) is coupled, which divides the frequency of the local oscillator signal by a scaling factor K. and generates a pre-allocated local oscillator signal, and that the pre-allocated local oscillator signal of the arrangement (38, 40) for generating the control signal is supplied via a circuit arrangement (46) which divides the frequency of the pre-divided local oscillator signal by a factor N, which depends on the selected channel. 9. tuning device according to claim 7 and 8, characterized in that K is equal R is. 10. Tuning device according to claim 9, characterized in that the circuit arrangement (46) for dividing the frequency of the pre-divided local oscillator signal by the factor N contains a programmable counter, and that the factor K is chosen is that the frequency of the pre-divided local oscillator signal is less than or equal to the highest frequency that the programmable counter can process. 809810/0826 27389CJb U
-4jt- 11. Abstinuneinrichtung according to claim 10, characterized in that K is a whole Number is. 12. Abstinuneinrichtung according to claim 11, characterized in that the circuit arrangement (36) includes a first counter circuit for dividing the frequency of the fixed frequency signal by the factor R; that the circuit arrangement (44) for dividing the frequency of the local oscillator signal by the factor K a second counter circuit and that the factors K and R are equal to 240. 809810/0826