EP0263314B1 - Transducer arrangement - Google Patents

Description

The invention relates to a transducer arrangement for the directed transmission and / or reception of sound waves of the type mentioned in the preamble of claim 1.

Sonar systems are used for reconnaissance or location tasks at sea or for presentations of combat situations or for coastal protection, with their transducer arrangements receiving waterborne sound over a wide frequency range. Bearings to targets are obtained via directional characteristics, which are formed with the received signals of the transducer arrangement. Target distances are determined in that directional sound is sent and received after reflection at the target, the transit time between sending and receiving indicating the distance to the target. In order to obtain comparable location data from targets which emit sound energy of different frequency contents, it is desirable that the directional characteristic has at least a constant opening angle in a wide frequency range.

From the magazine "Acustica", 1961, Vol. 11, "Constant-Beamwidth Arrays for Wide Frequency Bands" by JC Morris and E. Hands, a transducer arrangement is known in which the individual has an opening angle of the directional characteristic that is constant over the frequency range under consideration Transducers of the transducer arrangement are connected downstream of low-pass filters whose cutoff frequencies rise towards the center of the transducer arrangement, so that the transducer arrangement is effective over the entire length at low frequencies and its effective length is shortened towards higher frequencies. It is thereby achieved that the ratio of the effective length of the transducer arrangement and the wavelength of the sound received, which determines the opening angle, is the same for all frequencies. A directional characteristic pointing to the normal of the transducer arrangement, which is formed by summation of the received signals, has a constant opening angle over the entire frequency range.

In order to be able to form a direction for pivoting the directional characteristics with the filtered signals, the low-pass filters must have the same phase and amplitude responses in spite of different cut-off frequencies. A corresponding filter implementation is extremely difficult. Another problem is that secondary lobes of such a transducer arrangement are also frequency-dependent, since the transducers are arranged equidistantly over the length of the transducer arrangement and the effective number of transducers decreases with increasing frequency.

It is an object of the present invention to provide a converter arrangement of the type mentioned in the preamble of claim 1, with which directional characteristics with constant secondary lobe behavior can be formed over a wide frequency range, the opening angles of which are frequency-independent.

The object is achieved according to the invention in a converter arrangement of the type specified in the preamble of claim 1 by the features in the characterizing part of claim 1.

In the converter arrangement according to the invention, in order to form the directional characteristic within a frequency range which is divided into frequency bands, the same number of converters are combined to form a converter group for each frequency band and the converter groups are arranged nested one inside the other along the length of the converter arrangement. The distances between adjacent transducers are not the same if neighboring transducers belong to different transducer groups. The distance between transducers of the same transducer group is, however, of the same size and is selected depending on a minimum wavelength in the associated frequency band in accordance with the uppermost frequency of this frequency band.

For the transducers of the transducer group assigned to the lowest frequency band, the distances are greatest and, for example, half as large as the smallest wavelength resulting from the upper limit frequency of this frequency band. The transducers in this transducer group are distributed equidistantly over the entire length of the transducer arrangement. Using the same filter or bandpass, which pass the lowest frequency band, the transmit or receive signals of the transducers of this transducer group are processed to form the directional characteristic. For the adjacent, next higher frequency band, the same number of transducers is equidistant at a distance of half the wavelength corresponding to the highest frequency in this frequency band between the existing transducers, with a shorter one rather than the entire length of the transducer arrangement between the outermost transducers belonging to this transducer group Distance is. This shorter distance is equal to the number of transducers in the transducer group multiplied by their distance from one another. However, the ratio between the minimum wavelength in this frequency band or the distance between the transducers of this transducer group and the distance of the most distant transducers is again the same as the ratio between the smallest wavelength in the lowest frequency band or the spacing of the transducers of the first-mentioned transducer group divided by the entire length of the transducer assembly. The advantage of this dimensioning is that the dimensioning rule known for achieving a constant opening angle for the two frequency bands, namely a constant ratio of wavelength and effective antenna length, is guaranteed and, in addition, the same antenna assignment is achieved through the number and spacing of the transducers per transducer group is such that the opening angle and secondary lobe behavior of the entire transducer arrangement are the same for the directional characteristics comprising the two frequency bands.

The transducer group of transducers used to form the directional characteristic in the next higher frequency band are required, are arranged in the same way between the transducers already existing in length, with downstream filters matched to the corresponding frequency band ensuring that only signals from these transducers in the corresponding frequency band are used to form the directional characteristic.

The particular advantages of the transducer arrangement according to the invention consist not only in the fact that the directional characteristic has the same properties with respect to the opening angle and secondary lobe behavior in the entire frequency range, but also in the fact that the space requirement of such a transducer arrangement is determined solely by the lower limit frequency of the frequency range.

A directional characteristic is obtained for each converter group in a directional generator downstream of the filters with the same passband, for example by delay or phase compensation. The outputs of all directional formers are connected to a summing stage in which the directional characteristics for each frequency band are superposed and a directional characteristic with a constant opening angle and secondary lobe behavior is formed for the entire frequency range. The advantage of frequency-separated direction formation and subsequent superimposition is that the filters have the same properties with respect to the amplitude and phase response for each frequency band, so that compensation can be easily set in any direction angle in any direction generator.

If the frequency range is divided into frequency bands that are multiples of one another, the entire multitude of transducers on the transducer arrangement is reduced by the further development according to the invention. Selected transducers of a higher frequency band would have to be provided at locations where transducers of a transducer group of a lower frequency band are already arranged, so that these transducers can be assigned to both transducer groups. Signals of these selected transducers are frequency-divided according to the advantageous development according to claim 3 to form the directional characteristic.

In the advantageous further development of the transducer arrangement according to claim 4, only a single direction generator is required, since the transducers of the same transducer group are arranged symmetrically to the right and left of the central transducer. The middle converter is assigned to all converter groups.

The dimensioning of the different distances of the transducers for each transducer group according to claim 5, in which, for example, the fraction is a quarter of the smallest wavelength of the associated frequency band, ensures absolutely identical geometric relationships.

A particularly advantageous embodiment of the converter arrangement according to the invention is specified in claim 6. The division into octaves doubles the frequency band and halves the distance between the transducers of the associated transducer groups. Transducers assigned to the transducer group corresponding to the lowest octave in the frequency band belong thus also to transducer groups correspondingly higher octaves, since they are arranged in squares which correspond to even-numbered fractions of the maximum transducer distance, so that the multitude of transducers is further reduced over the entire length of the transducer arrangement. Each transducer that belongs to several transducer groups is followed by filters, the pass band of which includes the corresponding octaves. It is particularly advantageous for further signal processing to connect individual filters, each tuned to an octave, to the converters and to assign a summing stage to the filters of a converter. Even in the case of a converter arrangement according to claim 6, only a single direction generator is required to create the directional characteristic for the entire frequency range, which delivers directional characteristic signals for different swivel angles with the same properties in accordance with preset transit time compensation.

In order to improve the secondary zip field attenuation of directional characteristics, it is customary to evaluate transmit or receive signals of the transducers with so-called shading factors in accordance with the position of the transducer on the transducer arrangement.

Claim 7 specifies an advantageous development of the transducer arrangement according to the invention, with which such an improvement can be separated for each frequency band in a simple manner and can thus be carried out individually.

The invention is based on exemplary embodiments shown in the drawing for a transducer arrangement for transmitting and / or receiving sound waves within a wide range Frequency range shown.

Fig. 1

eine schematische Darstellung einer Wandleranordnung bei einer Aufteilung des Frequenzbereichs in Frequenzbänder unterschiedlichen Frequenzumfangs,

Fig. 2

eine schematische Darstellung einer Wandleranordnung bei einer Aufteilung des Frequenzbereichs in Oktaven und nachgeschalteter Richtungsbildung.

Show it:

Fig. 1

1 shows a schematic representation of a transducer arrangement when the frequency range is divided into frequency bands of different frequency ranges,

Fig. 2

a schematic representation of a transducer arrangement with a division of the frequency range into octaves and subsequent direction formation.

1 shows a transducer arrangement for transmitting and / or receiving sound energy, the directional characteristic of which has a constant opening angle β and the same secondary lobe behavior in a frequency range from 500 to 8000 Hz, for example. The opening angle ß is determined by the lower limit frequency f _u = 500 Hz and the length L₁ of the transducer arrangement, as described in the previously cited article by Morris and Hands.

wobei λ _u die zugehörige Wellenlänge und c die Ausbreitungsgeschwindigkeit der Schallenergie ist, so erhält man den Öffnungswinkel β zu:

If one sets for the lower limit frequency f _u =

where λ _{u is} the associated wavelength and c is the propagation speed of the sound energy, the opening angle β is obtained as follows:

The length L₁ of the transducer arrangement is dimensioned according to the desired opening angle β depending on the lower limit frequency. From Eq. (2) it can be seen that the opening angle β remains constant if the ratio λ _u / L₁ remains constant. However, the associated wavelength λ decreases by more than ten times over the frequency range from 500 to 8000 Hz and with a propagation speed c = 1500 m / s.

The assignment of the length L 1 with transducers determines the secondary lobe behavior of the transducer arrangement or its directional characteristic. The distance between the transducers depends on the smallest wavelength to be evaluated and is at most as large as half the wavelength in order to obtain clear direction finding results.

1, the frequency range is divided into three frequency bands, F₁ = 500 to 1000 Hz, F₂ = 1000 to 5000 Hz, F₃ = 5000 to 8000 Hz. The upper limit frequency of 1000 Hz in the lower frequency band F₁ determines the maximum transducer distance d₁ and thus the transducer assignment over the length L₁.

For L₁ = 2.25 m, the number of transducers is n = 4. Transducers 11, 12, 13, 14 are arranged in Fig. 1 at a distance d₁ = 0.75 m over the length L₁ = 2.25 m and form one Converter group. In practice you will occupy a much greater length L 1 with a much larger number n of transducers, the transducer arrangement shown in Fig. 1 is only to be understood as an example.

Each of the four transducers 11, 12, 13, 14 of this transducer group is followed by a filter 111, 112, 113, 114 with bandpass behavior which is tuned to the frequency band F 1, followed by a directional generator 150. In the case of reception, the direction generator 150 ensures the time delay of the received signals from the converters at the output of the filters 111 to 114 in accordance with the desired directional characteristic.

In the case of transmission not shown here, a transmission signal is fed into the directional generator and shifted in time with respect to one another. Outputs of the directional generator are followed by n filters 111 to 114, which are tuned to the lower frequency band F 1 and are connected to the n converters 11, 12, 13, 14.

Between the transducers 11, 12, 13, 14, four further transducers 21, 22, 23, 24 are arranged symmetrically to the center of the transducer arrangement, the distances d₂ of which are chosen depending on the upper limit frequency 5000 Hz of the frequency band F₂. Their distance from each other is d₂ = λ₂ / 2 = 0.15 m, the total length L₂ of the group of transducers 21, 22, 23, 24 is L₂ = 0.45 m. The ratio / L according to G1. (2) is the same for both groups of transducers 11 to 14 and 21 to 24 and is

Each of these converters 21, 22, 23, 24 is followed by a filter 221, 222, 223, 224, which is tuned to the frequency band F₂ and has bandpass behavior. In a directional generator 151, the directional characteristic for the frequency band F₂ is formed.

A third transducer group with transducers 31, 32, 33, 34 is used to form the direction in the upper frequency band F₃ = 5000 to 8000 Hz. Your distance d₃ is determined from the upper limit frequency of 8000 Hz to d₃ = 0.09 m. Each of the transducers 31 to 34 is followed by a filter 311 to 314, which is tuned to the frequency band F₃. The filters 311 to 314 are followed by a direction generator 152.

The direction formers 150, 151, 152 are connected to a summing circuit 400. When it is received, the directional characteristic signal at the output of the summing circuit 400 has constant properties with respect to the opening angle β and secondary lobe behavior for different swivel angles over the frequency range from 500 to 8000 Hz.

berechnet. Ein vorgegebenes Nebenzipfelverhalten wird durch entsprechende Belegung der Wandleranordnung realisiert. Hier ist als Wandlerabstand der maximale Wandlerabstand d = 1,5 m gewählt. Aus der Länge L und dem Wandlerabstand d wird die Anzahl n = 5 bestimmt. Symmetrisch zu einem mittig plazierten Wandler 1000 sind jeweils zwei Wandler 1001 und 1002 im Abstand d und zwei Wandler 1003 und 1004 im Abstand 2d angeordnet. Die Wandler 1000 bis 1004 bilden eine Wandlergruppe und sind mit Filtern 1010 bis 1014 verbunden, die das unterste Frequenzband Δf₁ durchlassen.The converter arrangement is simplified when the frequency range is divided into octaves. 2 shows such a converter arrangement for a directional characteristic within a frequency range from 250 to 2000 Hz Frequency range is divided into three frequency bands Δf₁ = 250 to 500 Hz, Δf₂ = 500 to 1000 Hz and Δf₃ = 1000 to 2000 Hz, each comprising an octave. Depending on the opening angle β, according to G1. 2 determines the length L of the transducer arrangement for the lower frequency band Δf₁. If the length L cannot be freely specified for design reasons, a specific opening angle β can be set by specifying the lower limit frequency of the frequency range. According to the highest frequency of 500 Hz in the lowest frequency band Δf₁, the maximum transducer distance is too

calculated. A predefined secondary lobe behavior is realized by appropriately assigning the transducer arrangement. Here, the maximum transducer distance d = 1.5 m is selected as the transducer distance. The number n = 5 is determined from the length L and the transducer distance d. Two transducers 1001 and 1002 are arranged at a distance d and two transducers 1003 and 1004 are spaced 2d symmetrically to a transducer 1000 placed in the center. The transducers 1000 to 1004 form a transducer group and are connected to filters 1010 to 1014 which pass the lowest frequency band Δf 1.

By dividing the frequency range into octaves, the distance between the transducers of the second transducer group, which is required to form the directional characteristic for the frequency band Δf₂, is just equal to d / 2 = 0.75 m. A converter 1005 is arranged between the middle converter 1000 and the converter 1001, and a converter 1006 is arranged between the converters 1000 and 1002, each of which relates to the center converter 1000 Have distance d / 2. The centrally located transducer 1000 and the transducers 1001 and 1002 not only belong to the first transducer group, but also to this second transducer group, since they are arranged in multiples of the transducer distance d / 2 from the centrally located transducer 1000. The five converters 1000, 1001, 1002, 1005, 1006 thus form the second converter group. They are each followed by filters 2010 to 2014, which are tuned to the frequency band Δf₂.

For the frequency band Δf₃, a transducer group of five transducers 1000, 1005, 1006, 1007, 1008 is also provided on the transducer arrangement, the distance d / 4 of which is a quarter of the maximum transducer distance d because the upper limit frequency of 2000 Hz of this frequency band Δf₃ four times as high as the upper limit frequency of 500 Hz of the lowest frequency band Δf₁. The middle converter 1000 thus belongs to all groups. In addition to the filters 1010 and 2010, it is followed by a third filter 3010, which is tuned to the frequency band Δf₃. The transducers 1005 and 1006 belong to two transducer groups. You are each two filters 2013, 2014 and 3013, 3014 for the middle frequency band Δf₂ and the uppermost frequency band Δf₃ downstream as a pass band, while the converters 1007 and 1008 each have only one tuned to the top frequency band Δf₃ filter 3011 and 3012. The different distances between the transducers of the three transducer groups form a geometric series since they are d, d / 2, d / 4.

To further improve the directional characteristic, the filters 1010 to 3014 contain evaluation circuits for Shading factors. Depending on the frequency band and the geometric position of the transducer, shading factors are stored in the evaluation circuits, with which the filtered received signals are multiplied before the direction is formed.

Due to the special geometric relationships of the transducer arrangement according to FIG. 2, the direction formation is simplified insofar as individually selected transducers 1000, 1001, 1002, 1005, 1006 are assigned to several transducer groups and their received signals require the same time delays to form the directional characteristic. Received signals from the selected converters 1000, 1001, 1002, 1005, 1006 are combined at the output of the filters 1010, 2010, 3010 or 1011, 2011 or 1012, 2012, ... in summing stages 4010, 4011, ..., 4014 , before they are further processed in a downstream direction generator 4400 for directional characteristics. A circuit arrangement according to DE-PS 21 36 780, for example, can be used as the direction generator 4400.

In the summing stage 4010, the received signal of the converter 1000 is combined in the entire frequency range after a frequency-dependent evaluation. Rated reception signals from the transducers 1001 and 1002, which belong to both the first and the second transducer group, are combined in the summing stages 4011 and 4012 for the two frequency bands Δf₁ and Δf₂. In the summing stages 4013 and 4014, the evaluated reception signals of the converters 1005 and 1006 for the frequency bands Δf₂ and Δf₃ are added. The two outer transducers 1003 and 1004 only belong to the transducer group that is required for direction formation in the lowest frequency band Δf 1. The converters 1007 and 1008 belong to that Transducer group, their evaluated received signals are fed directly into the direction generator 4400. A directional characteristic signal can be taken off at the output of the directional generator 4400 and has the same properties at different swivel angles over the entire frequency range.

Claims (7)

1. A transducer arrangement for the directional transmission and/or reception of sound waves within a wide range of frequency, having a plurality of transducers lined up over a length and filters which are connected to the transducers and whose output signals are combined to form a directional characteristic, characterized in that of the plurality each transducer group is formed by the same number (n) of transducers (11 to 14; 21 to 24; 31 to 34; 1000 to 1004; 1000, 1001, 1002, 1005, 1006; 1000, 1005, 1006, 1007, 1008); a frequency band (F₁, F₂, F₃; Δf₁, Δf₂, Δf₃) within the range of frequency is associated with each transducer group, the frequency bands (F₁, F₂, F₃; Δf₁, Δf₂, Δf₃) adjoining one another and covering the range of frequency; the transducers (11 to 14; 1000 to 1004) are disposed equidistantly within a transducer group at a distance equal to or smaller than half the smallest wave length contained in the particular frequency band (F₁; Δf₁); the number (n) of the transducers 11 to 14, 21 to 24, 31 to 34; 1000 to 1008) associated with a transducer group is determined by the length (L₁; L) and the maximum transducer distance (d₁; d) in the transducer group associated with the lowest frequency band F₁; Δf₁); and the filters (111 to 114, 211 to 214, 311 to 314; 1010 to 1014, 2010 to 2014, 3010 to 3014), which are connected to transducers (11 to 14, 21 to 24, 31 to 34; 1000 to 1004, 1000, 1001, 1002, 1005, 1006, 1000, 1005, 1006, 1007, 1008) of the same transducer group, are tuned to the frequency band (F₁, F₂, F₃; Δf₁, Δf₂, Δf₃) associated with said transducer group.
2. A transducer arrangement according to claim 1, characterized in that selected transducers (1000, 1001, 1002, 1005, 1006) belong to a number of transducer groups whose associated frequency bands (Δf₁, Δf₂, Δf₃) are multiples of one another.
3. A transducer arrangement according to claim 2, characterized in that a number of filters (1010, 2010, 3010; 1011, 2011, 1012, 2012; 2013, 3013, 2014, 3014) tuned to the associated frequency bands (Δf₁, Δf₂, Δf₃; Δf₁, Δf₂; Δf₂, Δf₃) are connected to each selected transducer (1000; 1001, 1002; 1005, 1006) corresponding with its association with a transducer group.
4. A transducer arrangement according to one of claims 1 to 3, characterized in that the transducers (1001 to 1004; 1001, 1002, 1005, 1006; 1005 to 1008) of each transducer group are symmetrical in relation to a centrally disposed transducer (1000), and the centrally disposed transducer (1000) is associated with all the transducer groups.
5. A transducer arrangement according to one of claims 1 to 4, characterized in that the different distances in the transducer group each have the same fraction of the smallest wave length in the associated frequency band (F₁ to F₃; Δf₁ to Δf₃).
6. A transducer arrangement according to one of claims 1 to 5, characterized in that an octave is associated as the frequency band (Δf₁, Δf₂, Δf₃) with each transducer group; the distances (d) of the transducers (1000 to 1004) of the transducer group associated with the lowest octave (Δf₁) are the largest; and the distances (d/2; d/4) in each of the transducer groups associated with the next higher octave (Δf₂; Δf₃) are half as large as in the transducer group which is associated with the subjacent octave (Δf₁; Δf₂).
7. A transducer arrangement according to one of claims 1 to 6, characterized in that each filter (111 to 114, 211 to 214, 311 to 314; 1010 to 1014, 2010 to 2014, 3010 to 3014) comprises an evaluation circuit for shading factors corresponding to the position of the transducer (11 to 14, 21 to 24, 31 to 34; 1000 to 1008) inside the transducer group.

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