DE1766462C3 - Arrangement for filtering or equalization of electrical analog signals - Google Patents

Description

/ (. '. ¹ M / IMe

d /

with the required filter transfer factor H (Q essentially coincides; here D denotes a period of time which is shorter than the rotation time of the disk (2). Ω the angular velocity of the disk (2), f (t) the time function according to which the Afterglow subsides; the function / (Ut) is defined by the fact that l (x) is the light permeability of the screen (4) in any point (P)) SU lying on the image of the light path with respect to the image (A) of the light beam the system axis fA7 encloses the angle λ (Fig. 2).

4. Arrangement according to one of claims 1 to 3, characterized in that the rotating disc (2) is designed as a rotor of a synchronous motor, the supply voltage of which is from a through a mechanical oscillator, for example a quartz crystal, stabilized oscillator is derived.

5. Arrangement according to one of the preceding claims, characterized in that the speed of the rotating disc (2) is less than or at most equal to the reciprocal of the time duration (D) of a predetermined time function | 'Λ [τ]).

6. Arrangement according to one of the preceding claims, characterized in that in place the intensity modulation means for modulating the deflection angle of the light or Electron beam (1) 'is provided, which the light or Electron beam (t) in the cycle of the input signal from its rest position in the radial direction deflects, and that the light transmission of the screen (4) in the radial direction after a given function.

7. Arrangement according to one of the preceding claims, characterized in that at the point of the ^r me luminescent substance provided disc (2) of the iinier> i_ined! Icne LiUHu ';i> hiäv sigkeit having screen (4) rotates, and that the light - Or the electron beam (1) rotates synchronously with the screen (4) at a constant speed.

8. Arrangement according to claim 7, characterized in that for realizing a rotating Electron beam (1) and an afterglow disk (2) a cathode ray tube is used.

9. Arrangement according to one of the preceding claims, characterized in that on the Screen (4) several concentrically arranged tracks (7 ') with different light transmittance are applied, which run according to different predetermined functions that each of these tracks (7 ') independent, concentrically formed photosensitive elements (15) are assigned, which convert the luminous flux passing through the individual tracks (7 ') into electrical Convert signals, and that the light or electron beam! (1) in the radial direction like this it is extended that his picture sweeps over all traces (7).

10. Arrangement according to claim 9, characterized characterized in that to achieve the radial expansion of the light or electron beam (1) the disc (2) provided with the luminescent substance is preceded by a slit-shaped diaphragm is. whose slot extends in the radial direction.

11. Arrangement according to claim 9, characterized characterized in that to achieve the radial expansion of the light or electron beam (1) an astigmatic optic (3) is used.

12. Arrangement according to one of claims I to 8, characterized in that the tracer (6) on the disc (2) provided with the afterglowing layer of several electron or light beams offset from one another in the radial direction (la, \ b, ic is written), that 'are) applied whose ^Translucent: .gkeiten according to different predetermined functions extend, and that each of these traces (7' on the screen (4) a plurality of concentrically arranged tracks (7) independent of one another, concentrically formed light-sensitive elements ( 15) are assigned, which convert the luminous flux passing through the individual tracks (7 ') into electrical signals.

13. The arrangement according to claim 12, characterized in that instead of several concentrically arranged photosensitive elements only one photosensitive element is provided in to which the signals of the individual. Overlay traces of light.

The invention relates to an arrangement for filtering or equalizing electrical analog signals.

As is well known, this occurs again and again when messages are transmitted electronically Problem of dividing a frequency band into several sub-bands. To solve this problem, Filters labeled arrangements are used. Furthermore, arrangements called equalizers are required, to compensate for the so-called linear distortions, those that a signal suffers, if the attenuation or the group delay of the contribution path is not independent of the frequency Size is.

To build filters as well as equalizers, ohmic resistances are generally used, Wash. Capacitors and semiconductors, especially transistors, are used, but sometimes also mechanical ones Resonators, e.g. so-called oscillating crystals. depending on Task and required quality can be a filter or an equalizer all or only part of the included switching elements.

Each type of embodiment of a filter suffers from particular technical disadvantages. Such disadvantages are ι ζ. B. the relatively large space required by coils or the temporal inconsistency and - with justifiable Cost - relatively low accuracy of the semiconductors. All to be built up from individual switching elements Filters have the common feature that their ι < Transmission factor cannot have any given course, even if one is arbitrary frequency-independent Shifting the attenuation or the group delay allows; rather, a given Transfer factor only with a finite: Realize accuracy, and the higher the required Accuracy is, the more switching elements there are to spend.

Another disadvantage of the filters mentioned is their limited ability to be detuned. d. do when the trans-. · - If a filter is to be changed arbitrarily, all or most of the filters have to be changed Switching elements can be changed or even replaced. what - Tilt with the exception of the transversal filter - on one Replacing the whole filter will result.

The invention is based on the object of countering the above-mentioned difficulty in a relatively simple manner; the structure of an i liter is to be specified, which is particularly useful in the range of relatively low frequencies, at least in the frequency range between 1 Hz and 100 kHz Despite a space consumption that is smaller than that of RLC filters, a frequency characteristic that can be reproduced with photographic accuracy and can be changed at will over a wide range by exchanging a single element

The considerations made below on the basis of filters can also be applied to equalizers or use arder-like linear quadrupoles.

Based on an arrangement for filtering or j-equalization electrical analog signals, this object is achieved according to the invention in the wines that a V'odulationseinrichtung is provided, which the intensity of an electron or light beam in the cycle of the signal to be filtered is modulated so that a <■ A transparent disk that rotates at a constant speed and is provided with an afterglow substance is provided on which the modulated beam writes a light trace that this trace is on a Screen is mapped that this screen along the - < on their traces of light shown have a different light transmittance that this light transmittance runs according to a predetermined function, and that the luminous flux passing through the screen by means of a light-sensitive element into an electrical * ■■ Signal is converted.

In the case of the disk provided with a luminescent substance, the principle is un; an Aryan spoke, especially known for digital applications, such as Me S-.yspielsweis ^ - i ¹ "■» msrb. ^! 963. Issue <2 S 50 "bi- ~ \\. / iir ■ i.irMrii: ^ ioniser he connections describe sir ·. ' Re ¹ dc f-νίιηάιηι? However, not only the storage ·! ^ ·· ■ effect, but also the afterglow is used and the following considerations are based on the assumption.

Di? Filtering or equalization of a signal by a quadrupole consisting only of coils, capacitors and resistors, ie a so-called RLC filter, can be represented mathematically as follows.

Let s (t) & a ^ signal to be filtered and

Si / i

sf / ic "" 'if

its Fourier transform. also "Spectral Unit" or "Spectrum" for short.
Further be

IH '>

iJ.i

the complex transmission factor of the filter, with attenuation a (f) and phase b (ß
Then this is the filtered Signa!

s '/ IIS, I lic ^: ' d /. ι -ι

where the spectral function

S. (/ ι Si / ι ■ IH ι < '- <

by multiplying the unfiltered signal spectrum iii with the transmission factor of the filter.

You can also use the filtered signal through a Represent convolution integral. If you are with

/ ü, ¹ ! / // l / IC -A! Oi

the inverse Founertransform of the transfer factor tors or the "zoit function" of the filter, the with feasible filters for f <0 identically must disappear. then applies

In rl si /

s (rl /; I ¹

On the basis of these theoretical considerations, the Invention will be explained in more detail.

It shows in the drawing the

1 purely schematically an arrangement / in explanation of the subject matter of the invention,

F i g. 2 schematically a realized embodiment of the subject of the invention,

F i B. 3 the attenuation curve of a filter nact F i g. 2.

F i g. 4 a filter switch for splitting a: wide transmission band into several sub-bands.

F i g. 5 an arrangement for simultaneous filtersunj; p'.Ve-L. iir.ti. · -.thieii '''-.y ji ^ mle.

V; Hand over fig .; sol · first schematic. ¹ '! ■■■.: '- ■ vjrd'.n, in what way a realization tir: ·. · A _{; i} orJr.ur.g to ^r I ^! mwandiung electric Sigrid i.nter use ά ·: Γ; Ί · jngsintegraN £ <-: näß ^r 'i> • ■ hür.p (6) is possible.

A light or electron beam 1, which is intensity-modulated by a modulation device 9 with the time function s (i) , strikes an endless belt 2 'moving perpendicularly to it at the constant speed ν. The band 2 'is coated with an afterglow substance and is itself translucent. A light trail is thus created on the band 2 '; if it is assumed that the light intensity of the afterglowing substance decays exponentially with the time constant T , the intensity profile of the afterglow is along the tracer

;> ■■ '

for \ - I)

for ν · - D

I / I

where χ is the coordinate counted in the direction of movement from the point of incidence of the light beam and α is a constant dependent on the system of measurement. equation (7) only applies if s (t) is not negative; this can always be done by adding a sufficiently large constant - e.g. B. a bias - can be achieved and therefore means practically no restriction. Behind the band 2 'there is a screen 4' with light permeability l (x) which can be changed in the: * Α direction, on which the light track is imaged by an optical system 3 '. The lengths of the band 2 ', the system 3' and the screen 4 'are initially assumed to be unlimited. Behind the screen 4 'there is a light-sensitive element 5' which collects all of the light passing through the screen and converts it into electrical current.

The from the photosensitive element, such as. B. a photocell recorded time-dependent luminous flux is ^

/ 'If) =

/l.v)/(.Y)d v

where ei means a constant that depends on the system of measurement. If the course of the light transmission of the screen is designed so that it corresponds to the desired filter time function, multiplied by an exponential function that compensates for the decay of the afterglow, namely

then one obtains with (7) and (8)

pll) = c, C ₂ ί sit - τ) / ΐ (τ) ατ
ο

IiOl

thus the desired filtered signal except for a constant factor

As can be seen, non-linear distortions arise then when the afterglow intensity of the screen is not in the shape

IU) = Ht ₀ ) -f UI ₀ )

tiOa)

decays Such a non-linearity occurs in the case of luminescent substances in the vicinity of their saturation. she however, the blackening, i.e. H. so through the different light transmission of the screen 4 '

65 are compensated if the beam intensity is constant and the modulation, as in the following is effected by deflecting the beam. It is useful to move away from the saturation area keep it far enough away.

The F i g. FIG. 2 shows, in a schematic representation, an implemented embodiment of an optical filter, which is why the FIG. 1 equivalent components are provided with the same reference numerals, the only difference being that the apostrophes used in FIG. 1 have been omitted. For a better overview, FIG. 2 the individual components drawn relatively far apart, while a much more compact arrangement of the individual components can be achieved for the practical construction. The filter consists of a disk 2, an optical system 3, a screen 4 and a light-sensitive element 5. The individual parts are arranged along an axis X so that the axis X penetrates the center points of the components and that the planes of the components stand perpendicular to this X axis. The disc 2 consists of a transparent material which is provided with an afterglow substance. The disk 2 rotates at the angular velocity Ω and is driven, for example, by a synchronous motor. The screen 4 is also made of a transparent material and is provided with a dashed-line blackening 7, which thus results in a different light transmission in the circumferential direction of the screen and which is designed in such a way that it runs according to a certain, arbitrarily predetermined function. The course of these different light transmittance corresponds to the desired time function, that is to say the transfer function to be demanded from the filter, and is applied to the pane 4 in the form of a blackening with different gray levels.

The mode of action can again be explained as follows.

The light or electron beam 1 passes through a modulation device 9 and is modulated there with the signal to be filtered. On the pane 2 provided with the afterglowing substance, a tracer 6 is written, which fades away as the pane moves around and which, because of the transparency of the pane 2, is imaged on the screen 4 provided with the blackening 7 via the optical lens system 3 passing through the assembly is indicated by dashed lines on the basis of the product applied to the screen 4 blackening 7 is passing through the screen 4 luminous flux 8 of the desired predetermined time function is proportional, so that from the photosensitive member 5, for example a photocell, the individual signal components corresponding to the darkness of the screen converted into an electrical signal. If the pane 2 can be brought sufficiently close to the screen 4, the optical system 3 can also be omitted. In the case of higher imaging accuracies, however, an optical system will preferably be used which can consist of one or more lenses. IMe speed Q / 2st of the pulley must be less than or at most equal to MD ; the meaning of the variable D will be explained in the following.

The light transmittance of the screen 4, the light imaged on the track 6 is in any on the Bud the tracer ligand Hege point P must now a function / fojdes angle "be the one of the image P and

582

Λ. ι w \ * r x ^ *

A of the light beam is included with respect to the X axis of the system.

/ (■ Ι / il- <. '.' I e "'ι I2i

(Dear all of me

if the afterglow does not decay exponentially (see equation 10a).

In the practical embodiment, the modulated light or electron beam 1 hits the pane 2 not in one point, but in a light spot. This has the same effect as if the output signal were additionally filtered by a low-pass filter with the cutoff frequency Ω / ρ , where ρ is the radius of the light spot (in radians). It is therefore important to keep the light spot so small that the low-pass effect mentioned does not interfere.

In the case of ÄLC filters, the time function h (r) decays exponentially with increasing r without disappearing - except at discrete points in time. The error caused by the time limit with T = D is calculated back to the transmission factor of the filter.

I Hi t) ■ - -

"dl

(IS)

and must be determined separately for each time function.

But it is by no means necessary that optical filters be the same. Have frequency response like RLC filters. It is therefore possible to use time functions that are limited in time and cannot be implemented with discrete switching elements from the outset; A desired attenuation or phase curve can thus be achieved with any accuracy, if only the time duration D, which must be much less than the rotation time of the disk, is made sufficiently large how large D must be, can be determined by the following considerations .

From Shannon's sampling theorem follows. that with a time duration D of the time function hfr) the transfer factor H (F) at the equidistant frequencies

I.
D.

can pretend. H (f) can then be represented in the following form

sm.-rPt / - /,)

(20)

This results in an implementation process for H (f) prescribed within a tolerance range:

One takes certain values for A and D, calculates the H (f), and determines whether the preparation of H (f) is according to equation (20) within the tolerance range this is not the FAIL so must attempt having a greater D be repeated.

As can also be shown, a change in the pulley speed by the factor (1 + ε)

exactly like a replacement of the transfer factor what

This means that the same accuracy must be demanded for the constancy of the speed as for the most sensitive ones Resonance frequencies of an equivalent coil filter. If you demand quartz accuracy here, you have to In the case of the optical filter, stabilize the speed using an oscillator with crystal precision. the In practice, the effort required for this is much less than with conventional filters if you have a single filter Oscillator can be used to stabilize several optical filters.

In this case, the rotating disk 2 is expediently designed as a rotor of a synchronous motor, which is driven by the stabilized alternating voltage. The runner poles can because the required Drive power is very small, as the periodically changing magnetization of a ferromagnetic layer on Edge of the disc to be attached.

As investigations on which the invention is based have also shown, it sometimes causes technical difficulties to establish sufficient equality between the electrical signal to be filtered and the intensity of the light or electron beam modulated therewith. In order to avoid the effort required for this, it proves to be expedient under certain circumstances not to modulate the intensity, but rather the deflection angle of the beam in the radial direction. In this case, the blackening applied to the screen 4 must also change in the radial direction in such a way that the light transmission of the screen in the radial direction is proportional to a function g (β) or is at least a linear function of g (β) . where s (t) -g (β) represents the relationship between the modulating signal and the deflection angle β .

In further training it is a; s inventive concept also possible, not the disc provided with the afterglowing substance 2. but the one with dei To allow the screen 4 provided with blackening 7 to rotate. In this case, the disk 2 is stationary, but it must ensure that the beam 1 rotates synchronously with the screen 4 at a constant speed Ir In this case, the rotating electron beam and the luminescent disk can be realized a cathode ray tube of known design use the. The synchronism between the rotating Electron beam and the rotating screen 4 can be, for example, with the help of an electric coupling manufacture. Also for such an execution form have the above salvage their full validity

The F i g. 4 shows a further development of the concept of the invention in such a way that a feed switch for splitting a wide transmission belt ii is simulated several narrower sub-belts. In this case , several concentric tracks T are applied to the transparent screen , the light transmission of which runs according to different predetermined functions. Each of the tracks T thus forms a filter with a different predetermined transmission characteristic. The luminous fluxes passing through the tracks T are sensitive to light! Elements 15 caught, which are also arranged concentrically and which are dimensioned such that

609 630/61

i?

in each case one of the light or electron streams coming from the tracks T is converted into electrical signals only in one of the light-sensitive elements 15. In this way, output signals can be picked up at the output terminals 16a, 166 and 16c of the individual light-sensitive elements, which, for example, are offset in their frequency position by a certain amount according to the formation of the tracks T 1 narrower sub-bands can be removed. It is only necessary to ensure that the light or electron beam 1 ^{strikes all tracks 7 'of the transparent pane A} , for which purpose it is necessary to expand the beam 1 in the radial direction. For this purpose, a diaphragm 10, which is provided with a slot-shaped opening, is expediently used. Further possibilities for achieving the radial expansion of the beam 1 consist in using an astigmatic optical system instead of a converging lens according to the exemplary embodiment according to FIG. 2, or in generating the astigmatism of the steel electrically.

The arrangement according to FIG. 4 can also be modified in such a way that the same filter arrangement is used for filtering several signals. The corresponding structure is shown schematically in FIG. 5 drawn Namely, the disc 2 provided with the afterglow substance can be described by several modulated light or electron beams la, \ b, ic , so that each of these rays leaves a traces of light on the disc 2. For this purpose, it is useful to offset the incident light or electron beams in a radial direction, which can be done simply by slightly offsetting the radiation sources. The structure following the disk 2 corresponds to that in FIG. 4 and it can then, for example, at the output terminals 16a, the filtered signals of the beam la, to the

10

Output terminals t6b the filtered signals of beam ib and the filtered signals of beam Ic are picked up at output terminals 16c.

If the concentrically arranged light elements 15 are now replaced in the exemplary embodiment in FIG through a single photosensitive element, then the output voltage of this photosensitive element Elements contain all incident rays la to Ic, whereby a filter switch is simulated, the several narrow sub-bands combined to form a wide transmission band.

The arrangements according to FIGS. 4 and 5 an extremely space-saving structure can be achieved, because a whole series of filters are housed in a single arrangement with the same building blocks are.

Due to the structure according to the invention, apart from the relatively small space requirement, still achieved the following advantages:

The optics and the luminescent screen can be in exactly the same design for the most diverse Kinds of filters are used, which means that in series production an inexpensive production of these Can achieve components. The screen 4 as that which determines the frequency response of the signal to be converted Element can be reproduced cheaply and reliably by photographic means. In addition, it's through the blackening of the screen 4 fixed transfer factor no temporal and thermal Subject to signs of aging and is thus retained with a constancy that is found in LC filters can also not be achieved by the arbitrary blackening 7 of the screen 4 Realize exactly the filter transfer factors that can only be approximated with LC filters. in the In particular, there is also the possibility of producing ideal phase-linear filters.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Arrangement for filtering or equalization of electrical analog signals, characterized in that a modulation device (8) is provided which modulates the intensity of an electron or light beam (1) in time with the signal to be filtered, that continues with one constant speed rotating, transparent, provided with ι ο a luminescent substance provided disc (2) on which the modulated beam (1) writes a tracer (6) that this tracer (6) is shown on a screen (4), that this screen (4) has different light transmittance (7) along the traces of light shown on it, that this light transmittance runs according to a predetermined function, and that the luminous flux (3) passing through the screen (4) by means of a light-sensitive element ( 5) is converted into an : o electrical signal. 2. Arrangement according to claim 1, characterized that the image of the tracer (6) on the screen (4) via an optical system, in particular a lens (3) takes place. ; > 3. Arrangement according to claim 1, characterized in that that the course of the light permeability is chosen in such a way that the Fourier transform