DE689473C - Determination of vibration processes by comparing their total running times - Google Patents

Description

GERMAN EMPIRE

ISSUE Al
29th MARCH1940

REICH PATENT OFFICE

PATENT LETTERING

M 689473 CLASS 74 d GROUP 6

Gustav Guanella in Zurich, Switzerland,

has been named as the inventor.

by comparing their total runtimes

Patented in the German Empire on November 19, 1937 Patent granted March 7, 1940

To determine the direction of vibration processes, for example of electromagnetic vibrations or sound waves, methods are usually used Application in which the vibrations in different locations through each other recipients far enough away are checked and compared in an appropriate manner will. Either the recipient can be moved by special mechanisms or the processes recorded by stationary receivers delayed by special facilities for certain duration amounts. In both cases it is about the received or delayed processes in time to cover to bring what is possible through constant comparison. Usually it is two oscillation processes caused by two recipients that are sufficiently far apart from each other or groups of recipients.

The best known are the subjective comparison methods, namely the binaural method for acoustic oscillation processes. In the case of the generally applicable interference methods (maximum and miramuim methods) is always a maximum or minimum due to a subjective or electrical comparison to search.

As experience shows, these

680

same methods various disadvantages. The binaural method requires particularly experienced observers, with whom a relatively rapid fatigue cannot be avoided. The determination of the direction is e.g. Comparison of acoustic processes due to background noises from different origins is slightly strong impaired. Interfering noises also cause those to be set in the interference method Maxima or minima easily blurred in an inadmissible manner. By secondary maxima Depending on the frequency spectrum, or secondary minima can also be deceptions.

The invention relates to a method which largely avoids these deficiencies to compare vibration processes. With a relatively very low level of interference Disturbances of any kind make this possible

ao procedure an exact setting of two Operations on cover.

According to the method of the invention, two are determined to be compared to the two Vibration processes associated electrical voltages are generated whose frequency-identical components have the same phase differences as the associated ones components of the same frequency of the original processes from which assigned Tensions then a control spin is obtained through mutual modulation, that of the mutual phase position of the partial frequencies of the processes to be compared depends.

It is therefore referred to below as a modulation method. By Modulation generated control voltage depends on its mean value, as shown below will, from the runtime differences of the to be compared to vibrations. The vibration originally had the spectrum

«Η COS ((W _n ί 99«).

Therein by a _n is the amplitude, by (X) _n and the frequency of the respective phase position φ _η a "-th component of the vibration, respectively. The oscillation is received at different locations and the running time of the received processes may be further delayed by special delay devices, so that the two voltages to be compared are _{behind the original process by the total delay times T 1} and τ ₂ , which are therefore with the correct setting should be as equal as possible. By modulating these tensions, with an ideal piroduct pattern, apart from one factor,

Σ O _n COS [ω » (t ~ T ₁ ) φ _η ] · Σ« η COS [a> n (t T ₂ ) ψη),

where G and W denote the direct and alternating current parts. The direct current component G arising only from the component of the same frequency of the two modulated voltages is included

G = - · Σ al ~ cos ω «(T ₁ - T ₂ ).

2 η

(3)

It is easy to see that this sum becomes a maximum _{when both total transit times T 1 and Ta are equal.} One can therefore speak of a modulation maximum method in particular with this modulation method. Depending on the character of the noises, secondary maxima are also possible with certain differences in the total transit times T ₁ and T ₂ , mainly when individual frequencies occur with a particularly large amplitude. It should be pointed out, however, that these secondary maxima do not always have the same character as those known from the interferemetogram. In particular, it is not necessary that every secondary maximum or minimum of the interference method correspond to those of the modulation method. The avoidance of such secondary maxima by receivers with suitable directivity and suitable frequency response as well as by using special filters is indicated below.

A particular advantage of the modulation method is that it has little influence the control DC voltage due to interference, which may have similar frequency ranges like the processes to be compared. It turns out that local disturbances, which only affect one recipient hit, if the control voltage is sufficiently calming down, none at all worth mentioning Cause influencing the same.

One could, however, be expected that interference from the side lying distant noise sources, as far as they are received at all of the directed _uo receivers give an unwanted contribution to the control voltage. Such disturbances have naturally because of the large time differences correspondingly large ng phase differences of their relevant part of frequencies on which generally exceed 90 ^0th Accordingly, certain subfrequencies of the interference according to equation (3) result in positive components of the control voltage, while other Teilfrequen zen cause negative error components. In the with

689 47S

tel is deslialb 'the resulting interference voltage very small, provided that the disruptive processes have a sufficient frequency richness exhibit.

According to the previous explanations, the comparative method according to the invention can be (Modulation method) for example with the help of the schematically drawn in Fig ', ι Realize device in which all

ίο unimportant for understanding how it works Apparatus such as amplifiers, auxiliary instruments, etc., are omitted, although they are indispensable for practical implementation and can be of crucial importance for working with the modulation method.

By S ₁ and S ₂ , the two recipients, z. B. Microphones for comparing two noises shown, which are assumed to be pivotable about the X axis. The control voltage generated by the modulation device M is calmed down in the low-pass filter B and fed to the indicator /. The filter /? can be omitted from / if there is sufficient inertia and damping.

The indicator /, for example a direct current instrument, shows a maximum when the noises received by S ₁ and S _{2 are the same.} In practical work with the apparatus, it is a matter of always "keeping the maximum deflection" by making constant small search movements with the sound receivers.

In general, in the devices which are based on a comparison method, for. B. according to the interference method, the receivers are arranged to be pivotable about a certain axis, so that equality the total running times always by setting the recording direction accordingly the recipient is reached. But there are also methods and devices known in which the change in transit time for fixed receivers by means of a corresponding adjustment special delay devices is achieved. An advantage of such an arrangement consists in the larger basic distances of the receiver, which are no longer constructive Boundaries are bound.

It is clear that the method according to the invention can also be used with stationary receivers for the comparison of vibration processes and for setting the same total running time can be carried out, as is also shown in the schematic diagram of FIG.

N Through S ₁ and ^ ₂ , the receivers that are now stationary are shown again.

L ₁ and L ₂ denote two propagation delay devices. Such a device for delaying all transmitted signals by a certain predetermined and changeable time can consist, for example, of a steel band which is moved past a writing head and an acceptance head. The electrical signals are recorded by the write head in the form of a variable magnetization of the tape. After a certain time, which is given by the distance between the two heads and the tape speed, the magnetic recording is picked up by the pickup head, the original electrical signal being generated again with a corresponding time delay. Other means can also be used to delay the propagation time, e.g. B. acoustic transmission through a pipe system of a certain "length or electrical transmission via a coil line made up of series inductances and discharge capacities. Furthermore, the delay devices, if high-frequency alternating currents are to be delayed, consist of matched Lecher lines of suitable length. The transit time delay devices! L ₁ and L ₂ are always set in the practical work with the apparatus such that the total transit times of the compared with the modulation means M noises are the same. the control at the maximum DC component is performed again by an indicator /, if necessary after stabilization of the control voltage by low-pass filter B.

The modulation device M must be designed in such a way that the control voltage continuously corresponds to the product of the two applied voltages. If possible, it only has to form sum and difference frequencies, with the difference frequencies containing the direct current component, the control voltage, which is essential for the display. Modulation circuits which, in addition to these first sum and difference frequencies, also form further combination frequencies, have the disadvantage that such combination frequencies are not characteristic of the transit time differences and can thus give rise to unnecessary misdirections.

For example, FIG. 3 shows a double modulation circuit which is suitable for the present purpose. With the quadratic characteristic of the dry rectifiers G ₁ and G ₂ and after the necessary adjustment of the same by a suitable choice of the resistors R ₁ and R ₂ , the voltage e _k always corresponds to the product of the two applied voltages e _x and e ₂ . If the voltage across R ₁ , G _{1 is} equal to e _± + e ₂ and the voltage across R ₂ , G _{2 is} equal to - e _t + e ₂ ,

so are the currents across the rectifiers and resistances with a quadratic characteristic

H = CxXe ₀ + e _± + e ₂ ) ² over R ₁ , G ₁ ,

i ₂ = c ₂ '(e _g - e _t - \ - e%) ² over R ₂ , G ₂ ,

where C ₁ , C ₂ and e ₀ rectifier constants

Ct; ^^ = 2 (R _x C ₁ -j- i? 2 C ₂ ) · (#q ι · where Ii ₁ and k _{2 are} constants. The second term therefore contains the stress product e _x e ₂ , while the first term still contains The input voltage e _x alone is represented. Other circuits with the same effect are known from measurement technology, telecommunications and high-frequency technology, which are used, for example, for frequency analysis, for carrier wave modulation and for demodulation and which are also suitable for the present purpose 4 also mentions the so-called ring modulation circuit according to FIG. 4, which, in contrast to the circuit according to FIG the modulation method is characteristic of the fact that the calming control voltage when using two receivers of the same type is generally with the square of the au f increased amplitude. Accordingly, small changes in the receiver input voltage per se result in relatively large changes in the control voltage, as a result of which the directivity of the receiver is supported in a useful manner. On the other hand, it is not necessary with the modulation method that both receivers have the same directivity, because only such oscillation processes result in a direct current component in the control voltage, which are received simultaneously by both receivers. This essential difference compared to the apparatus based on the interference method enables the construction of apparatuses in which a pronounced directivity of the entire apparatus is achieved when using receivers with partially limited directivity. For example, a receiver with a very low directivity can work together with a receiver whose directivity has been chosen to be sufficiently large in accordance with requirements according to the modulation method, with the resulting directivity corresponding to this last receiver.

Especially with the ones described above. The voltage drop across the resistors R ₁ and R ₂ between the pair of terminals 2i is therefore

6k = i'i Ri ■ ΐ « R ₂ 's

if one now makes R ₁ C ₁ = R ₂ C ₂ , after calculation it results

Apparatus with artificial transit time delay and relatively far apart There is a great advantage for recipients in the analogous use of recipients limited directivity with changing direction of incidence of the one to be compared Vibration processes, whereby the tracking is simplified and facilitated. In an application of the subject matter of the invention For listening devices to locate aircraft, it is sufficient, for example, if a The only centrally located sound receiver with good directivity thanks to the appropriate Coupling with the electrical or acoustic delay device is always tracked while the other sound receivers, which are relatively distant from it, remain rigidly mounted.

But you can also use two receivers, each one strong in one level are sensitive to obtaining an apparatus that is only unidirectional, i. H. the Intersection of the planes, appeals when these planes of directional sensitivity of both Receivers are perpendicular to each other. The advantage of such a solution is in particular for listening devices in that a funnelless device as a sound receiver can be used in which a number of microphones are mounted on a straight beam, creating a distinctive Sensitivity for all sound waves is created that fall perpendicular to this beam. There is also the possibility of realizing this sound-sensitive beam with a single microphone of the appropriate shape, for example as a cylinder sound-sensitive surface.

When working in practice according to the new no Method for determining the direction of incidence of vibration processes, in particular of sound waves, can mainly be found when locating the noises or the recommend a temporary reduction in directivity for electric waves. this can be done by appropriate measures known per se to the recipients themselves, such as z. B. Shutdown of certain parts of recipient groups.

In general, the input voltages are sufficient or the tensions of the

Currents taken from delay apparatuses are not used for modulation and the following Actuation of the special indicators. Because of the modulation circuit there is an approximately quadratic relationship exists between the noise voltage and the control voltage, then there is an amplification of up to to a certain level minimum required.

ίο Depending on the distance of the vibration source and the propagation conditions of the The vibrations to be compared vary the amplitude of the processes to be controlled within very wide limits. Because of the above-mentioned quadratic relationship it is advisable to readjust the voltages to be modulated accordingly to be provided. This adjustment can, for example, by manual adjustment of reinforcement. It is more useful to use an automatic gain control, by which the noise voltage level at the output of the amplifier more or less at a constant Value is held. Such control circuits are known from amplifier technology. It it is recommended to generate the control voltage required for the control Rectifiers with a quadratic characteristic should be used, as also those caused by modulation obtained control voltage depends on the amplitude squares of the individual voltage components. The amplitude of the too controlling vibrations is generally very slow to change, so that the amplifier control voltage generated in this way has a time constant of several seconds can be reassured. Are now borrowed when determining the direction If receivers carry out rapid search movements, the gain is only slightly changed by the control activity, i.e. H. the rapid amplitude fluctuations occurring during these search movements, which the facilitate practical work, are not suppressed, and only those over a longer period of time averaged amplitude is regulated to an approximately constant value.

It should be noted that the amplitudes of both are mutually modulated Tensions need not be equal. A certain difference in these tensions may vary depending on the person Modulation circuit can even be useful and is naturally due to appropriate mutual adjustment of amplifiers easy to achieve.

• To reduce the disturbance caused by short-term disturbance oscillations of particularly large amplitudes, it is advisable to reduce the electrical voltages prior to the modulation in M by means of amplitude limiting circuits known per se, e.g. B. using dry rectifiers with bias or electron tubes with a correspondingly curved characteristic to limit to a certain value.

It is related to the nature of the comparison by modulation that the course the control tension thus formed depends to a large extent on the character, d. H. from the spectral Composition of the vibrations to be compared depends. Depending on the composition For example, the above-mentioned secondary maximum values can be more or appear less pronounced. Such secondary maxima. can naturally be avoided when using receivers with particularly strong directivity. According to what has been said above, however, a corresponding Changing the energy distribution in the frequency spectrum can be of great benefit. For example In listening devices, a strong preference for the low frequencies leads to fairly widely spaced minor extremes caused by directional sound receivers are easier to avoid. A preference for the high frequencies, on the other hand, enables the direction to be determined very precisely. The higher frequencies of the practically occurring noises also occur with such a richness of different frequencies Components on that secondary maxima of concern are no longer to be expected are.

Furthermore, since certain frequencies do not occur in the vibration processes to be compared, or only with a low amplitude, and since certain frequency ranges are also insignificant for determining the direction, so that they are advantageously suppressed for the sake of eliminating interference, it is advisable to filter the received vibrations in correct in an appropriate manner. This filtering can be carried out using a suitable frequency response of the receiver, amplifier and also using special electrical filters that can be changed or switched on and off if necessary. Naturally, both noises to be compared do not need to be filtered in the same way, although it is advisable to filter out the frequencies to be suppressed from both recorded oscillations for reasons of interference elimination, especially when the mode of operation of the modulation circuit M is not ideal, i.e. when higher-order combination frequencies are formed.

With listening devices it is particularly important to suppress unnecessarily high frequencies to reduce the noise voltage, d. H. through microphone and

increased noise caused interference. A temporary suppression of high noise frequencies in favor of low frequencies can be recommended when searching, while when chasing one already found noise source suppresses the low frequencies to increase it the accuracy see recommends. You can therefore have a search circuit and a ίο differentiate between working circuits.

It does not matter whether the phase position of the various frequency components of the two vibrations received by the receiver, amplifier, filter and possibly further transmission and converter equipment by certain frequency-dependent amounts is rotated. But it is important that the apparatus according to the present Invention work according to the Modulationsmaximumzo method, the components of the same frequency both oscillation processes are rotated by the same amount. Is this for some reason for certain? Frequencies originally not the case, so networks can become more frequency-dependent Phase rotation an improvement can be created. .

Taking into account the auxiliary equipment described above, starting from FIG. 1 and FIG. 2, a more complete scheme can now be given, for example according to FIGS. Extensions and modifications are possible. The amplifiers are represented by V ₁ and V ₂ in these figures, their amplification by feeding back the rectified output voltage via R ₁ and 40, respectively

Σ On ₁ COS [{co " + Q _n ) t Oi _n X _x - φ _η Ip _n ] or,

R _{2 is} regulated. F ₁ 'and F ₂ ' indicate the additional amplifiers required. The alternating current _{indicators Z 1} and Z ₂ are provided for level monitoring of the voltages at the input of the modulation circuit M. Since these instruments also display interference voltages from laterally incident waves, while such interference voltages do not result in any significant change in the deflection of /, by comparing the displays of Z ₁ and Z ₂ with the maximum deflection of / also on the amplitude of the interference getting closed. The filters mentioned above are represented by P ₁ and F _2. The other apparatus and designations are already known from FIGS.

According to the description so far, the partial frequencies assigned to the oscillation processes are of the same frequency as the voltages fed to the modulation device M. As the calculation shows, this does not always have to be the case. There may be certain and even frequency-dependent frequency differences between the components of the original oscillations assigned to one another and the voltages carried on M. However, the aforementioned condition of the phase position must always be met.

Let each component of the frequency Ci) _n and the original phase position φ _{η be} a component of the voltages to be compared by modulation with the changed frequency co " + Q _n , the phase position <p _ni + ψη _{ or 9?" ₂ + ψ _η , and the changed amplitude a _m or U _n . , so that _v can be written more generally for these voltages:

Σ On ₁ COS [(W _n + Q _n ) t CO _n T ₂ - ψη - ψη] . (4)

and for the direct current component of the control voltages:

Q _ | _ _. 2 a _ni a _lu cos JVa _n (T ₁ - T ₂ ) -f- ψ _ηι - ip _lh ].

2 η

(5)

If, according to the phase condition mentioned, the frequency transformation occurs

Occurring change ψ _± or ψ _{2 in} the phase position of a certain frequency component is the same for all components of the same frequency in both oscillations, i.e. if ψ W ₁ = ^ w ₂ , the direct current component of the con-

.55 troll tension again:

G = - · 0, Ji ₁ ^ Ji ₂ COS [ß) n (T ₁ - T ₂ )]. (6) ² η

Although the frequency change Q _{n may} in itself be frequency-dependent, the mechanisms that come into question in practice are generally a frequency-independent constant, no

Such a frequency transformation by frequency band shifting can be done by modulation take place with a certain carrier wave and filtering out a sideband from the alternating voltage thus formed. this is in the circuit diagram of Fig. 7 omitting all that are unimportant for understanding Parts shown.

The carrier wave of sufficiently high frequency is generated by a generator O. The modulation with the voltages to be compared takes place in the auxiliary modulation circuits.

sen H ₁ and H ₂ to form the upper and lower sidebands corresponding to the original processes. One of the sidebands is separated out by high-pass filters or low-pass filters P ₁ or P ₂ and fed to the comparison modulation circuit M already mentioned.

When used for listening devices, the frequency band shift can also advantageously take place in the sound receivers by using condenser microphones on which, instead of the constant bias voltage, there is a certain carrier frequency, although for sufficient suppression of the carrier wave that occurs with a relatively very large amplitude before the Modulation in M is to be provided. Ji ₁ and H _{2 are} unnecessary in this case.

The smaller resulting relative bandwidth of the voltages to be compared should be mentioned as an advantage of the frequency band shift. In-phase amplification is ■ facilitated. On the other hand, different oscillation processes axbOiduiMerte with different carrier waves, eg · for simultaneous height and azimuth determination, can be amplified with the same amplifiers.

The control voltage, if necessary calmed down by the calming device B, preferably a suitable low-pass filter, is fed to a direct current indicator 7, for example a direct current instrument, a cathode ray pointer or another suitable pointer of known construction. However, it can also be an indicator which, in conjunction with a control device, is used for the automatic detection and tracking of waves of variable origin.

A control voltage indicator 7 with non-linear characteristics can be useful in the optical-manual as well as in the automatic tracking of the direction of incidence. For example, an instrument with a scale that is pushed down to neglect the interference voltages that cannot be completely avoided, or an instrument with a scale that is pushed up with regard to the quadratic amplitude transfer of the modulation circuit M.

To make searching and tracking easier, it is advisable to visualize the alternating components contained in the control voltage by means of an alternating current indicator according to FIG. 8. This instrument is denoted by I _{w in FIG. 8.} The direct current component is suppressed by a high-pass filter K. The deflection of /, "'is due to differences in runtime. little dependent and is determined in its further course by the directional characteristic of the receiver. In contrast to this, 7 shows a pronounced when the transit times are the same. Maximum. The differences between the two displays can be used to draw conclusions about runtime differences. As has been shown, disturbances incident from the side do not result in any significant change in the. calmed control voltage, ie the deflection of the direct current vector J _w is not influenced. On the other hand, they result in additional alternating current components at the output of the modulation circuit M , which result in an increase in the deflection of /, “. By comparing the two readings, it is possible to conclude that there are stronger interference voltages. To make things easier, the above mentioned metrics Z ₁ and Z _{2 can also be} provided.

9 shows an arrangement in which two identical modulators M ₁ and M _{2 are} provided. A first control voltage is generated in M ₁ in the manner described above by modulating two voltages to be compared, calmed in B ₁ and indicated by J ₁ . In the second modulation circuit M ₂ , on the other hand, one and the same voltage is applied to the input terminal pairs. The modulation product of M ₂ is settled in B ₂ and fed to the trailing current instrument / _{s as a second control voltage.} A third direct current instrument / is used to display the difference between the control voltages indicated _{by Z 1} and I _2. If the amplitudes of the voltages are the same for the same sensitivity of the receiver and the same gain and if the two transit times are also the same, so that both voltages are the same at every moment, then the modulation products of both modulators M ₁ and M _{2 are the} same because the input voltages of these modulators are also the same cover each other. The instruments I ₁ and I ₂ therefore give the same deflections in this case, and the differential pointer 7 remains de-energized. If, on the other hand, the transit time of the two voltages to be compared changes while the amplitude remains the same, then naturally the deflection of I _{2 is} retained, while the deflection of I _{1 is} reduced in the manner described earlier. The voltage difference, which is characteristic of the transit time differences, is displayed by the instrument 7. The amplitude of the recorded voltages and thus the display of I _{2 are} only reduced if the receiver is set incorrectly. When working practically with the at hand. described by Fig. 9

Using the apparatus, a rough adjustment will first be made by regulating the receiver position to a maximum deflection of J ₂ . Then one looks for the exact setting which results in the same running times of both voltages by regulating the deflection of J ₁ to a maximum amount, ie one looks for the setting at which the differential voltage indicated by 7 tries

to dwindle.

Such arrangements are particularly suitable for listening devices with automatic tracking the sound receiver or the delay devices for the autotna-

Ί-5 tables find and track certain Sources of noise.

Claims (10)

Patent claims: i. Method and device for determining the direction of incidence of Vibration processes by comparing their total running times, characterized in that that two specific electrical voltages assigned to the two processes to be compared are generated, whose frequency components have the same phase differences as the associated components have the same frequency components of the processes to be compared and a control voltage from these associated voltages through mutual modulation is obtained from the mutual phase position of the partial frequencies which depends on the processes to be compared and their direct current component by setting their maximum value is used to produce the same total running times. 2. The method according to claim 1, characterized in that the voltages to be compared by modulation are passed through a delay device which is used to change the total running time differences in arrangements with two or more mutually relatively distant fixed receivers. 3. The method according to claim 1, characterized in that by modulation Processes to be compared are recorded by moving receivers and by moving the receivers at least approximately in the direction of incidence of the processes to be compared the comparison is made with regard to the running time. 4. The method according to claim 2 or 3, characterized in that one of the voltages to be compared are generated by means of a receiver arrangement, which responds at least to processes that occur in a certain first level, while the other of the voltages to be compared by means of a receiver arrangement which is essentially sensitive to processes which take place in a certain two " fall in the th plane that does not coincide with the first plane. 5. The method according to claim 1 or 4, characterized in that the mutually electrical to be modulated and assigned to the processes to be compared Tensions by modulating a carrier wave with these processes and, if necessary, by filtering out a Sideband of the resulting modulation products are generated. 6. The method according to claim 1 or the rest, characterized in that one first control voltage according to the modulation method from two of the two to voltages associated with comparative processes are generated and a second control voltage is generated by self-modulation one of the two associated voltages in a further modulation device The whole thing becomes an end, through the formation of the difference between these two KontroUspaimunigen clues! in terms of Existing running time differences of the vibration processes to be compared to obtain. 7. The method according to claim 1, characterized in that the control voltage is broken down into a direct current and an alternating current component and these components are visible to themselves are made for the purpose of determining runtime differences or excessive disruptions. 8. Device for performing the method according to claim 1 to 6 or 7, characterized in that amplifier 105. are provided with automatic gain control, the amplitudes using a suitable control constant the voltages assigned to the processes to be compared before the no Bring mutual modulation to a level that is as constant as possible. 9. Facility for carrying out the procedure according to claim 1 Ks 6 or 7, characterized by amplitude-limiting Transmission medium of preferably non-linear. Character for purpose, to prevent false displays caused by strong disturbances. 10. Facility for carrying out the. Procedure according to. Claims 1 to 6 or 7, 68947S characterized in that at least one of the two is assigned in the transmission path Voltages electrical filters are attached to the frequencies which are used for comparing the running time of the related Processes to be investigated in their direction are of no use, have sufficiently strong damping, so that the proportion of these frequencies in the control voltage is negligible. For this purpose ι sheet of drawings . PRINTED IN THE