DE2164015A1 - PROCEDURE AND ARRANGEMENT FOR TUNING HF RECEIVERS, IN PARTICULAR TELEVISION RECEIVERS - Google Patents

Description

Graetz limited partnership 2164015

Altena

R.Schimmeyer-G.Bless-H.Pieren 11-3-3

Method and arrangement for tuning HP receivers, especially television receivers

The invention relates to methods and arrangements for tuning HP receivers, in particular television receivers, the work according to the superimposition procedure, their coordination electronically is changeable and provided for the reception of transmitters whose carrier frequencies are within a channel grid are at the same frequency spacing.

For arrangements of the type mentioned, it is expedient to set the respective desired channel without errors and / or the To be able to identify the set channel without errors, whereby a setting according to channel number, correspondingly supraregional Agreement or postal specification, is advantageous. It is also advisable to use the frequency that has been set to keep it as constant as possible at a given value in order to avoid signal corruption due to frequency drift.

It is known to make the channel setting by means of latching switches, with frequency and range-determining elements can be switched on or changed in stepped values one after the other. At the same time, the position of such a Switch a display of the number of the set channel derived, for example in the form of a pointer or a button marking in front of a circular number field or a number disc, which is arranged behind a window that only the Shows the number of the set channel.

However, this method can only be used at relatively low frequencies and a relatively large grid spacing. At higher

15th December 1971

str / mü /

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Frequencies and narrow channel spacing, such as in TV areas IV and V ₅ , result in great difficulties with regard to reproducible scale setting and constancy of the set frequency or the pass band _s because reactances in the form of concentrated components in the required gradation are practically no longer realizable.

Another widely used technique is channel tuning to be carried out by means of continuously changeable means, such as coil variometers, variable capacitors or electrically changeable To couple reactance elements (e.g. capacitance diodes) and with the setting element constantly moving pointers or scales, whereby the fc The channel number is also displayed using a number field.

Here it is difficult to come to a standard, reproducible and aging-resistant setting and display because Variations in component properties and mechanical deviations in the transmission and adjustment elements affect the relative position influence of the pointer and scale. In addition, as a result of the constant variability of the adjustment elements, any intermediate positions are possible possible, which on the one hand allow an inappropriate coordination of the recipient and on the other hand a clear one Can prevent assignment of the position of the display element to the number of the set and / or the received channel.

In order to keep the set frequency constant, a frequency control circuit is often used in which the intermediate frequency converted carrier is fed to a frequency discriminator, whose detuning-dependent output voltage by means of electronically changeable reactance elements are used to correct frequency deviations. The corrective effect is here however, it is limited, since the error reduction cannot be made arbitrarily large for reasons of dynamic behavior. aside from that can cause errors due to the signal composition and external

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Effects such as hum and noise interference occur (see, for example, Funksehau 1971, issue 17, page 535 ff and German Offenlegungsschrift 1 916 83 ¹ *, 21a4-29 / 01).

Furthermore, methods have become known in which one in stages by means of digitally operating electronic circuits A variable voltage is generated and used in a known manner by means of varactor diodes to tune a receiver will. A specific number of levels is assigned to a channel number. This can work with digitally Means are selected and displayed.

The method, when applied to closely spaced high frequency channels, requires elaborate precautions to achieve a reproducible voltage-frequency relationship and to compensate for external disturbances such as ripple voltages and exposure to temperature and is prone to aging.

In another, known method, the frequency of a conventional one by means of digital electronic circuits Measured by means of a tuned oscillator (frequency counter) and displayed (Nixie tubes), but not the number of the set channel {see 'e.g. "Radio mentor" magazine 1969, issue 9, pages 6I9 ff).

Furthermore, a principle of programmed, digital voting is known (see e.g. "radio mentor" 197I, issue 8, page 455 ff), in which an electronically, e.g. by means of capacitance diodes tunable oscillator is provided, the output frequency of which is used not only in the mixer, but also one Frequency divider is supplied, the division ratio of which is externally programmable. The divided frequency becomes with this known arrangement in a frequency and phase comparator compared with the reference frequency generated in a crystal oscillator. With the signal resulting from this comparison, becomes

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the electronically tunable oscillator is adjusted to the correct frequency. For television receivers, however, this would be the case reach very high frequencies of e.g. 800 MHz. It would be very difficult to count these exactly by conventional means prepare.

Above all, there is the disadvantage that for the receiver intermediate frequency, or the frequency for the associated oscillator, in the choice is no longer free, so that one does not Has the opportunity to bypass the area formed by harmonic interference, for example, and this leads to unfavorable interference radiation conditions .

The invention is based on the object of a tuning arrangement and / or a digital display of the set channel, in particular to create for television receivers, in conjunction with an AFC circuit and program selection according to channel number, in which the aforementioned disadvantages are avoided. It should therefore be possible to reproduce the number of a desired channel, digitally preselect and / or display the set channel with digital (electronic) means, to undertake and maintain the frequency tuning with the greatest possible accuracy, and the influence of component properties on this (Scatter, drift, aging) or interference (ripple voltage, temperature, signal quality) to be largely eliminated. * minimize and also the operation of such a receiver to simplify.

According to the invention, this object is achieved in that the oscillation voltage of the receiver oscillator which is already present with a spectrum which is an integral multiple of the channel spacing frequency exists and is generated by means of a coordinated auxiliary oscillator and a distortion circuit, is compared by means of a non-linear mixer circuit, which outputs a low-pass filter and an auxiliary intermediate frequency

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contains frequency matched filter, the auxiliary intermediate frequency is chosen so that it is equal to the distance between the oscillator frequency and one, of Channel to channel different component of the spectrum mentioned and the output voltage of the auxiliary intermediate frequency filter a frequency discriminator matched to the auxiliary intermediate frequency is supplied so that the voltage determining the frequency of the receiver oscillator runs in a sawtooth shape and comes from a voltage generator that can be configured, stopped or reset by additional signals can that the output voltage of the frequency discriminator over an electronically controllable switch is added to the output voltage of the sawtooth generator by means of an adder circuit is that the output voltage of the low-pass filter continues after rectification and conversion into pulses by means of suitable circuits, in particular an electronic Schmitt trigger Counter is supplied, which can be started, stopped and reset by additional signals, that in addition a logic circuit block is present, which in a known manner, by means of suitable programming means predetermined number corresponding to the number of a channel or a corresponding binary code with the number of the counter compares supplied pulses or one of these corresponding binary code and derives a signal therefrom, which in the event of coincidence of the preselected and actual number of pulses or code, the sawtooth voltage generator stops and the controllable Activates the switch and, in the event of a loss of coincidence, of the preselected and the actual number of channels set as a result of programming changes, the sawtooth generator and the counter resets and starts again and that finally actuates the programming means with the aid of an operating member or can be set in function and the logic circuit block for outputting the desired signals when changing channels or Change the specified channel number is initiated.

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According to one embodiment of the invention, the auxiliary oscillator is frequency-stabilized by means of a quartz oscillator.

In the course of the invention, electrical manipulated variables are taken from the programming device, with the aid of which in an known way by means of switching diodes or capacitance diodes the setting of the waveband in the receiver input part and oscillator, the frequency of the auxiliary oscillator and the tuning the filter and the frequency discriminator can be changed.

Another embodiment of the invention consists in that for the television band III ^f _d = 7 MHz and f = 0.25 MHz and in the ranges IV / V f _d = 8 MHz and f _& - 7.25 MHz one can be used for both ranges Receiver intermediate frequency f ^ = 38.9 MHz and auxiliary intermediate frequency f ₂ = 9.85 MHz is selected, with f, the grid spacing frequency generated by the auxiliary oscillator and with f the frequency offset between the channel and reference grid is designated.

According to a further embodiment of the invention is a display device present, which in a manner known per se converts an output signal of the logic circuit block into a visible, converts a number that corresponds to the number of the set channel.

The advantages achieved with the invention are in addition to the freedom from defects of setting and reading the channel number and the ease of use - fully automatic range setting - above all in the fact that the frequency tuning takes place independently of the signal quality with great accuracy and undisturbed from external influences such as operating voltage fluctuations and temperature expansion or aging effects remains, due to the use of an interference-free reference spectrum generated with quartz accuracy instead of a

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received carrier and avoidance of voltage-frequency-re-r lations. Elaborate, tension and temperature stabilizing Circuits are not required.

An embodiment of the invention is shown in the drawing and described in more detail below. Show it

FIG. 1, in the form of a block diagram, the basic structure of a receiver constructed according to the invention

FIG. 2 shows a frequency scheme to explain the mode of operation the invention.

In the following the invention is first explained with reference to FIG. 1, The input frequency f reaches the 1st mixer 2 via the antenna and preamplifier circuit 1 with the oscillator frequency f of the electronically tunable oscillator 3, the receiver intermediate frequency f> arises. This reaches the intermediate frequency amplifier and the demodulator, block 4, its output voltage, signal voltage U. forwarded to the playback device 5 and there in known Way is further processed.

With the help of a selector switch as a programming device or program memory 6 a channel number is selected from which, with the aid of logic circuits 7, the waveband to be set and the corresponding auxiliary intermediate frequency f ~ determined and the manipulated variables for setting the HF receiving part 1 and the discriminator 8 or the quartz oscillator 11 and the oscillator 3 be won.

As a result of a start signal in the operating part 9 (key press at Channel change) the sawtooth generator 10 is started via 7, whose output voltage U changes approximately linearly in time and thereby causes a constant change in frequency of the receiver oscillator 3. Except for the electronically tunable

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Oscillator 3, an auxiliary oscillator 11, for example a quartz oscillator, is also provided, which oscillates at a frequency f, which is equal to the grid spacing or channel spacing frequency. With the help of the spectrum generator 12, a harmonic spectrum or the reference frequency f 'is formed from the frequency f _{d , which is compared in the 2nd mixer 13 with the oscillator frequency f Q} , and from its mixing products with the help of the IFg filter lh the discrete and relative low auxiliary intermediate frequency f ~ is filtered out and fed to the frequency discriminator 8.

When the tuning voltage U. . When the individual components of the reference spectrum overflow, difference frequencies f ^ arise from the difference between the frequencies f of the electronic tunable oscillator and the components of the reference spectrum f ^f exist. This gives the possibility of filtering out the lower frequencies of f ^ that arise shortly before the difference 0 with a low-pass filter 15 and pulse shaper (so that there is one pulse when crossing the respective grid and the oscillator frequency itself does not have to be counted).

These differential frequency voltages are at the output of the low-pass filter 15 rectified and converted into pulses 16 by means of a Schmit trigger, for example. Each impulse thus signals the scanning of a channel and is registered in a counting circuit 17. Now if the preselected number agrees with the If the number of overflowed channels and thus the counting pulses match, the logic block 7 is used to determine the run or count. the sawtooth generator stopped. At the same time, the frequency discriminator 8 is released with the aid of the controlled switch 18. The correction voltage U.

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leads the electronically tunable oscillator 3, which is now already in the vicinity of the SoHab tuning, completely to its setpoint frequency. For this purpose, a closed control loop is formed via the 2nd mixer, mixer 13, IF filter 14, frequency discriminator 8 and oscillator 3, which now keeps the vote constant, the output voltage ϋ ^ _ΟΓΓ via the electronically controllable switch 18 by means of an adder 19 of the Output voltage U of the sawtooth generator is added. In the event of a loss of coincidence of the preselected and actually set number of channels as a result of a change in the programming, the sawtooth generator IO and the counter 17 are reset and restarted by means of the logic circuit block 7.

It is advisable to design the circuit in such a way that the tuning and holding ranges match.

From Figure 2, the frequency connection is in the case of target tuning of any channel. The upper ladder gives the frequency relationships in relation to the channel spacing and the lower ladder with respect to the reference spectrum. The grid spacing frequency, which is also the frequency at the same time, with which the auxiliary oscillator 11 oscillates is denoted by f. Of the The distance f ^ of the individual links is therefore the same in both conductors and constant. There is a frequency offset f between the channel grid and the reference grid. The multiples of f are therefore

ei Q.

drawn offset by f on both conductors. In addition, the input frequency with f,
the target tuning frequency with f,

the frequency of the electronically tunable receiver oscillator 3 with f,

the reference frequency with f,
the receiver intermediate frequency with f., the auxiliary intermediate frequency with f. >
and the interference frequency f - f 'is denoted by f.

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Since, as mentioned, the distance between the individual links in both conductors with f, is the same and constant, results from comparison from Figure 1 and Figure 2, for each meaningful vote - in Figure 2 with f = f drawn and through the from above coming arrow pointing to f marked f = f - the same constellation. The following applies:

^f z2 · ^f '»- ^f o
and (1) inserted in (2):

This can also be read from the lower ladder.

Furthermore, at So Hab, mood applies to what is present here flilfs-) spectrum width χ * f,

W ^f z2 * ^x ' ^f d - ^f zl - ^f a where χ is an integer and can be selected within certain limits.

For the case of correct adjustment to the setpoint frequency, the difference frequency, referred to as f ^, between the receiver oscillator and the auxiliary spectrum = f _z2 . If f _{z2 is chosen to be} relatively low, about 1 % of the range otter limit and the reference spectrum is generated by means of a quartz-controlled oscillator, the set oscillator frequency is stabilized practically with quartz accuracy, which is only reduced by the tolerance and drift of the frequency discriminator and the residual errors due to finite loop gain. Both can, however, be kept very small by choosing a relatively low auxiliary intermediate frequency, since it is fixed but freely selectable. If the receiver is to be used for several reception areas in which the grid spacing and / or offset between the grid and reference spectrum are different, the auxiliary wiping frequency must be changed; that means discriminator and fiI-

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R. Schimmeyer 11-3-3 -11- 216401b

ter must be retuned, expediently by means of switching or Capacitance diodes »which are activated by signals from the logic block. With a clever choice of f _, a

z2

Switching can be avoided. For example, in TV band III with f = 7 MHz and f = 0.25 MHz and also in the areas IV / V

Q α

with f = 8 MHz and f = 7.25 MHz with a receiver intermittent a

frequency f _zl = 38.9 MHz, the auxiliary intermediate frequency f _z2 = 9.85 MHz can be used.

A digital display 20, for example with digit display tubes, can be obtained from the number of registered pulses by means of known circuits or light-emitting diodes can be derived in order to be able to read the actually set channel optically.

To simplify operation, it is advisable to design the logic block in such a way that when the channel preselection is changed as As a result of the loss of coincidence, a new setting cycle with possibly changed setting of range selection and auxiliary intermediate frequency is triggered. This preselection change can be done, for example, by adjusting a preselection switch or by switching on another, already preset programming means happen, with a combination of several pushbuttons and electromechanical preselection switch is particularly useful.

5 claims
1 sheet of drawings

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Claims (3)

R.Schimmeyer 11-3-3 -12-? 1 R Λ f) 1 ^Γ Claims f 1 .J Method for tuning HP receivers, in particular television receivers that work according to the superimposition method, the tuning of which can be changed electronically and are intended for the reception of transmitters whose carrier frequencies are within a channel grid with the same frequency spacings, characterized in that, that the oscillation voltage (f) of the already existing receiver oscillator (3) with a spectrum which consists of integer multiples of the channel spacing frequency (f,) and is generated by means of a coordinated auxiliary oscillator (11) and a distortion circuit (12), by means of a non-linear mixer (13) is compared, which output contains a low-pass filter (15) and a filter (I ¹ _{I) tuned to an auxiliary intermediate frequency (f 2} ), the auxiliary intermediate frequency (f ₂ ) being selected so that it is in each case at the setpoint tuning (f) equal to the distance between the oscillator frequency (f) and a component of the mentioned spectrum (f ') which differs from channel to channel and the output voltage of the auxiliary intermediate frequency filter (I ¹ Q a to the auxiliary intermediate frequency
criminator (8) is fed. _(f?) to the auxiliary intermediate frequency tuned Frequenzdis- that the frequency (f) of the receiver oscillator (3) determining Voltage (U) runs in a sawtooth shape and one Comes from the voltage generator (10), which can be started, stopped or reset by additional signals, that the output voltage (U, _orr ) of the frequency discriminator (8) via an electronically controllable switch (18) by means of an adding circuit (19) of the output voltage (U _) of the Sä- so called tooth generator (10) is added, that furthermore the output voltage of the low-pass filter (15) after rectification and conversion into pulses (16) by means of suitable Circuits, in particular Schmitt trigger an electro- 309829/0558 niche counter (17) is supplied, which can be stopped and reset by additional signals started, that also a logic circuit block (7) is present, which in a known manner by means of suitable Programming means with predetermined number corresponding to the number of a channel or a corresponding binary code compares the number of pulses (16) supplied to the counter or one of these corresponding binary codes and a Signal derives which, if the preselected and actual pulse number or code coincide, the sawtooth voltage generator (10) stops and sets the controllable switch (18) in puncture and in the event of a loss of coincidence of the preselected and actually set number of channels as a result of a change in the programming the sawtooth generator (10) and the counter (17) resets and starts again and that finally with the help of an operating member (9) the programming means (6) is actuated or set in puncture and the logic circuit block (7) for outputting the desired signals in the event of a channel change or a change in the specified Channel number is initiated. 2. Arrangement for performing the method according to claim 1, characterized in that the auxiliary oscillator (11) is frequency stabilized by means of a quartz oscillator. 3. Arrangement for carrying out the method according to claim 1 or 2, characterized in that the programming device (6) electrical manipulated variables are taken, with the help of which in a known manner by means of switching or capacitance diodes, the setting of the wave range in the receiver input part (1) and Oscillator (3), the frequency of the auxiliary oscillator (11) and the tuning of the filter (14) and the frequency discriminator (8) can be changed. 30982 9/0558 R.Sehimmeyer 11-3-3 - 14 - 216401- Arrangement for carrying out the method according to one of the preceding claims, characterized in that for the television band III f = 7 MHz and f = 0.25 MHz and in the ranges IV / V f = 8 MHz and f = 7.25 MHz one for there receiver intermediate frequency that can be used in both ranges ^f zl * ^{58ϊ9 MHz and auxiliary intermediate frequency f} _Z 2 ⁼ 9 » ⁸⁵ MHz is selected, with f, the grid spacing frequency generated by the auxiliary oscillator and with f the frequency offset between the channel and reference grid is designated. Arrangement for carrying out the method according to one of the preceding claims, characterized in that there is a display device (20) which converts an output signal of the logic circuit block (7) into a visible number corresponding to the number of the set channel in a manner known per se .