Transducer arrangement.

0001The invention relates to a transducer arrangement with a plurality of transducer elements for a pivotable directional characteristic of the type mentioned in the preamble.

0002In radar and sonar technology, transducer arrangements or antennas are required to form directional characteristics in order to determine the direction and distance of wave-emitting or reflecting targets. The opening angle of a directional characteristic determines the accuracy of the direction determination or bearing to the target and is determined by the length dimension of the transducer arrangement. A clear determination of the direction is only possible, however, if a plurality of transducer elements are arranged equidistantly at a distance from the smallest half wavelength to be received over the length of the transducer arrangement. Then the directional characteristic consists of a main lobe of maximum sensitivity and damped side lobes. However, if the distances between the transducer elements are greater than half the wavelength, be it for reasons of cost or because of the geometric dimensions of the transducer elements themselves or because of heat problems that occur during active operation, a direction determination is only possible under certain conditions, since the directional characteristic in addition to the desired main lobe, other lobes has the same sensitivity, so-called grating praise. Wave incidence from one or more of the directions in which the grating lobes point would simulate a bearing from the direction in which the main lobe is pointing. In order to rule out such incorrect bearing, in an actively working location system, for example, only a narrow sector is irradiated with waves, so that the grating-praise directions lie outside the sector. If sector limitation is not possible, the grating praise is suppressed or damped, for example, by constructing the transducer arrangement from statistically arranged transducer elements, as described, for example, in US Pat. No. 3,553,703.

0003PCT application WO 88/10523 corresponding to EP application 0315689 discloses a flat transducer arrangement for transmitting electromagnetic waves, which is composed of transducer elements arranged on concentric circles. Transducer elements of different sizes are used per circle, so that the distances of the transducer elements in the radial direction are different due to the different transducer element sizes. The number of identical transducer elements per circuit is determined by the transducer element size. The length of the radii of the concentric circles does not increase periodically. The transducer element size increases from the center and decreases towards the edge of the transducer arrangement, the smallest transducer elements are in the middle. Due to the non-periodic structure of the transducer arrangement, grating praise, due to the amplitude evaluation of the radiated wave given by the different sizes of the transducer elements, is attenuated, the antenna gain being the same as in a transducer arrangement with transducer elements of the same size.

0004For locating tasks, a plurality of directional characteristics pointing in different directions or a pivotable directional characteristic can be formed by phase control of the transducer arrangement. For each spatial direction, a special phase control of the irregularly arranged transducer elements is necessary, so that the effort required for phase-shifting elements to form the direction is significantly greater, particularly in the case of a continuously monitored spatial area, than in the case of a regularly configured antenna configuration.

0005It is an object of the present invention to provide a converter arrangement of the type mentioned in the preamble of claim 1, in which a plurality of directional characteristics pointing in different directions or a pivotable directional characteristic can be formed by avoiding incorrect bearing by grating praise without great additional effort. This object is achieved by the features mentioned in the characterizing part of claim 1.

0006The advantage of a transducer arrangement according to claim 1 is that the manufacture is particularly simple, since the transducer arrangement is based on a grid at half the distance of the transducer elements from one another and thus a periodicity. This grid is also advantageous for dimensioning the directional pattern, so that when a directional characteristic swings or the simultaneous formation of several directional characteristics pointing in different directions, multiples of phase rotation or propagation time increments can be assigned to the transducer elements, and a special delay or phase value for time compensation of their received signals does not have to be calculated and provided for each transducer element.

0007The transducer elements within a group have the same distance and from group to group 1.5 times the value of this distance. This measure ensures that at a distance greater than half the wavelength of the associated operating frequency, an incident of waves from the grating-lobe direction does not lead to incorrect bearing, since transducer elements of adjacent groups do not use the distance d, but 1.5 · d and waves received at the grating-lobe angle are shifted from group to group by half a wavelength and their received signals are thus extinguished. The energy received with an equidistant arrangement of the converter elements from the grating-lobe direction is split and distributed into adjacent angular ranges in the converter arrangement according to the invention. For groups with the same number of converters, this results in a directional characteristic with a main lobe and a zero at the associated grating-lobe angle for each swivel angle.

0008The grating-lobe angle is, apart from the swivel angle into which the directional characteristic points, dependent on the frequency and the distance between equidistant transducer elements. The offset of the groups by 1.5 times the distance provides the advantage that the suppression of the grating praise is guaranteed for every swivel angle of the directional characteristic and every frequency. Thus, the transducer arrangement according to the invention can be used advantageously not only for narrowband reception, but in particular also for broadband reception, for example in waterborne sound technology for trailing antennas for direction finding of watercraft in the low-frequency range, because the transducer arrangement can be saved and therefore a price reduction can be achieved, without the bearing accuracy decreasing.

0009When used in the high-frequency, narrow-band range, in which, for example, the size of the transducer elements cannot be arranged at a distance smaller than half the wavelength of the received sound waves, good bundling can be achieved in a particularly cost-saving and advantageous manner in terms of production technology, since the large number of transducer elements is also possible large dimensions of the transducer arrangement can be reduced and costs and weight can be saved with the same performance. The transducer arrangement according to claim 1 can thus advantageously be used in mine hunting and mine avoidance systems in which incorrect direction finding would be particularly harmful.

0010Both in narrowband and in broadband operation, it is equally advantageous that the directional generator is realized by multiples of phase or transit time increments, which means that the cost of circuitry can be kept low.

0011The large number of transducer elements can, however, not only be arranged along a straight line, but also along a curved line which, for example, follows a vehicle wall, one then speaks of a so-called conformed array. When used in waterborne sound engineering, the transducer arrangement follows the contour of a ship, submarine or torpedo. The converter arrangement according to the invention can also be implemented for a cylinder base. In all of these converter arrangements, the directional characteristics are formed by compensating for the transit time or phases of the received signals from the installation location to a straight line perpendicular to the direction of incidence of the wave and summation. Starting from this straight line, the dimensioning of the transducer arrangement is to be carried out according to claim 1. The individual transducer element locations are obtained by vertically shifting from the virtual location on the straight line to the geometric location on the installation line, which is canceled again by the direction generator.

0012For a flat transducer arrangement with a bundling of its directional characteristics in azimuth and elevation, the surface is divided by lines crossing in the middle and the transducer elements are arranged in groups along the lines.

0013The plurality of transducer elements is arranged along a straight line according to the advantageous development of the transducer arrangement according to the invention and its number of groups along the straight line is chosen according to the advantageous further development according to claim 3 so that a required damping distance between the main lobe and fragmented grating praise in the The area around the grating-lobe angle is maintained. Receiving energy that would be received from the grating-lobe direction in an equidistantly arranged transducer arrangement is distributed by the transducer arrangement according to the invention into adjacent angular ranges between the grating-lobe angle and the pivoting angle. The angular ranges depend on the number of groups. This also means that with the same bundling, the individual transducer elements per group move closer together, since the group spacings are equal to 1.5 times the value of the transducer spacings within the group. If the groups of transducer elements are of the same size, the directional characteristic results in lobes that are significantly less sensitive than the main lobe. In the angular range around the grating lobe angle, the lobes are fragmented grating lobes that are symmetrical to the grating lobe angle, in the remaining angular range up to the main lobe periodically occurring lobes that can be understood as pseudo-grating lobes. Their sensitivity decreases towards the main club.

0014In order to obtain a directional characteristic that is similar to a directional characteristic that can be achieved with a transducer arrangement with noisy distances between the transducer elements that are not periodic but statistical, according to an advantageous development of the transducer arrangement according to claim 4, the groups have different numbers of transducers, wherein the groups are arranged symmetrically to the center of the transducer arrangement. A converter arrangement is particularly advantageous in which the number of converters of the groups closest to the center is greatest and decreases towards the edge of the converter arrangement. This measure also splinters the pseudo-grating praise and, apart from the main lobe, the directional characteristic is continuously attenuated over all angular ranges to approximately the same level, which is lower the larger the number of groups. An additional influencing of the directional characteristic by an amplitude evaluation of the received signals of the transducer arrangement according to the invention is possible and brings the known advantages with regard to its side lobes. Simulation calculations of the directional characteristic can be used to easily optimize the number of groups and their number of converters.

0015It is particularly advantageous to select the number of transducers in the groups such that the transducer arrangement, as stated in claim 5, consists of two identical sub-bases which are arranged nested one inside the other and are mirror-inverted side-to-side. Each of the two sub-bases has a grid that is equal to the distance between the transducers. However, the two sub-bases are shifted from each other by 1.5 times the distance. By this measure, the position and level of all lobes, except for the main lobe, are distributed such that when the main lobe is pivoted into the maximum swivel angle, incident wave energy from other angular ranges is damped uniformly, the damping in the angular range around the associated grating lobe angle all the more the greater the number of groups. The reduction in the angular range between the grating lobe angle and the direction in which the main lobe points is the same if the number of converters in the groups is not the same. The splintered grating lobes symmetrically around the grating lobe angle level off in particular to the same low level when the number of transducers decreases from the center to the outside.

0016It is particularly advantageous to dimension the number of converters of the groups according to claim 6. The specified rule is comparable to the Leverage Act. The distance between the center of the transducer arrangement and each individual transducer element of the groups belonging to a sub-base is summed up to the right and left of the center of the transducer arrangement. A directional characteristic with maximum sensitivity in the main lobe at maximum swivel angle and uniform damping in the other angular range is ensured in that the sum of the distances to the right of the center is equal to the sum of the distances to the left of the center. As a result, the focus of each sub-base is almost on the middle of the transducer arrangement. With this dimensioning it is assumed that the received signals of the transducer elements are added after an amplitude evaluation of "1" in the directional generator.

0017However, if a non-uniform amplitude evaluation is carried out to further improve the directional characteristic, according to the advantageous development according to claim 7, the product is formed from the respective distance and the amplitude evaluation factor and the sum of the products for each sub-base taking into account the position of the transducer with respect to the center " Zero". In such a transducer arrangement, the damping lies around the grating-lobe angle in an angular range of approx. 10 ° at more than 35 dB compared to the sensitivity of the main lobe. The fragmented grating praise that limits this angular range has an attenuation of a good 10 dB. The attenuation in the angular range up to the swivel angle of the main lobe increases continuously up to values ​​of 30 dB.

0018The dimensioning of the number of transducers in the groups depends on the application of the transducer arrangement and is, for example, different in the case of a broadband operation, as is necessary for monitoring a sea area in a trailing antenna, than in the case of narrowband operation, as is customary, for example, in actively working sonar systems in which a high degree of selectivity with regard to echoes from a wide-range, irradiated sector is necessary.

0019In active systems, it is particularly advantageous to dimension the transducer arrangement for reception according to claim 7, in which the average number of transducers in the groups is selected such that echoes from directions other than the direction of the main lobe are received with significantly less sensitivity. In the case of pulsed sound from the grating lobe direction, the measure according to claim 8 ensures that the same number of transducer elements always have received signals which cancel each other out while the pulse sweeps across the transducer arrangement.

0020The transducer arrangements described for the reception case are also suitable for transmission.

0021The invention is described in more detail below on the basis of exemplary embodiments shown in the drawing for a transducer arrangement with a plurality of transducer elements for transmitting and / or receiving sound waves, which is part of a sonar system. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd> a transducer arrangement with groups of transducer elements whose number of transducers are the same,</dd><dt>Fig. 2</dt><dd> 1 shows a directional characteristic of the converter arrangement according to FIG. 1,</dd><dt>Fig. 3</dt><dd> a directional characteristic for a transducer arrangement with statistically arranged transducer elements,</dd><dt>Fig. 4</dt><dd> a converter arrangement consisting of two sub-bases, the groups of which have different converter numbers,</dd><dt>Fig. 5</dt><dd> 4 shows a directional characteristic of the transducer arrangement,</dd><dt>Fig. 6</dt><dd> a diagram for standard dimensions over the angle, parameterized with the number of groups.</dd></dl>

00221 shows a transducer arrangement for a waterborne sound system with a large number N of transducer elements which are arranged along a straight line 10. The transducer elements are followed by a direction generator (not shown here), which consists of phase shifters with monochromatic reception or from delay elements with broadband reception. The received signals of the transducer elements are added instantaneously when sound waves are received from the perpendicular to the center 11 of the transducer arrangement and form a directional characteristic with a main lobe in the direction of the central perpendicular and secondary lobes. The larger the extension L of the transducer arrangement, the smaller its opening angle. With the transducer arrangement and the direction generator, the directional characteristic can be swiveled through angle enk by means of time-of-flight or phase control, the maximum swivel angle being the drawn angle ζ_Max is. Likewise, several directional characteristics can be formed, the main lobes of which point at different swivel angles.

0023N = 32 transducer elements are arranged on the straight line 10, each forming groups 21, 22, 23, 24 with eight transducer elements, q = 4 being the number of groups. Within each group 21 to 24, the transducer elements are at a distance d from one another, between groups 21 and 22 or 22 and 23 or 23 and 24 1.5 times the value of the distance d. The distance d between the transducer elements is greater than λ / 2, where λ is the smallest wavelength of the received sound wave. With a swivel angle ζ_Max In addition to side lobes, the directional characteristic is accompanied by another lobe with the same sensitivity as the main lobe, the so-called grating lobe, at a grating lobe angle β, such as in "Microwave Scanning Antennas" by RC Hansen, Academic Press, New York and London, 1964, shown on page 203. The relationship sin β = sin ζ - n λ / d applies. The number of grating-lobe angles β and their size depend on the distance d of the transducer elements with respect to the wavelength λ of the received wave and on the swivel angle ζ. Different grating-lobe angles β are set for each swivel angle obe and each frequency f.

0024The distance d of the transducer elements is calculated from the dimension L of the entire transducer arrangement, the plurality N of transducer elements and the number q of groups according to the rule (N-1) * d + (q-1) * 1.5 d = L for example d = 3 λ / 4. In the event of sound coming from the swivel angle ζ, the grating-lobe angle β results as follows for n = 1:<maths id="math0001" num=""><math display="inline"><mrow><mtext>sin β = sin ζ- 4/3.</mtext></mrow></math><img file="EP0450191A2_D0001.tif" /></maths> For the direction formation of a directional characteristic under a swivel angle ζ = ζ_Max 1 is the delay time τ_m between the outer transducer elements of each group 21, 22, 23, 24, for example between the transducer elements at the positions of B and A.<maths id="math0002" num=""><img file="EP0450191A2_D0002.tif" /></maths> necessary, where m is the number of converters z of each group reduced by one.

0025For the transducer element to the adjacent group 23, for example between the transducer elements at positions B and D, there is a delay time of<maths id="math0003" num=""><img file="EP0450191A2_D0003.tif" /></maths> If a sound wave falls from the direction ζ = ζ_Max on, so the received signal <maths id="math0004" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>0</mtext></mrow><mrow><mtext>)</mtext></mrow></msup></mrow></math><img file="EP0450191A2_D0004.tif" /></maths> of the transducer element at position B with the initial phase ωτ₀ and the angular frequency ω by the delay time τ_{m + 1}+ τ_m, the received signal <maths id="math0005" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>0</mtext></mrow><mrow><mtext>+ τ</mtext></mrow></msup><msup><mrow><mtext>m</mtext></mrow><mrow><mtext>)</mtext></mrow></msup></mrow></math><img file="EP0450191A2_D0005.tif" /></maths> of the transducer element at position A by (τ_m+ τ_{m + 1}-τ_m) delayed and the received signal<maths id="math0006" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>0</mtext></mrow><mrow><mtext>+ τ</mtext></mrow></msup><msup><mrow><mtext>m + 1</mtext></mrow><mrow><mtext>)</mtext></mrow></msup></mrow></math><img file="EP0450191A2_D0006.tif" /></maths> of the transducer element at position D by τ_m and the received signal at position E<maths id="math0007" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>0</mtext></mrow><mrow><mtext>+ τ</mtext></mrow></msup><msup><mrow><mtext>m + 1</mtext></mrow><mrow><mtext>+ τ</mtext></mrow></msup><msup><mrow><mtext>m</mtext></mrow><mrow><mtext>)</mtext></mrow></msup></mrow></math><img file="EP0450191A2_D0007.tif" /></maths> not delayed. The phase signals are added:<maths id="math0008" num=""><img file="EP0450191A2_D0008.tif" /></maths> If a sound wave occurs from the grating-lobe angle β during this direction formation, the received sound wave has a transit time difference t at the transducer element at position D compared to the transducer element at position E, which each form the outer transducer elements of group 23_m whose sign is negative compared to the delay times τ.<maths id="math0009" num=""><img file="EP0450191A2_D0009.tif" /></maths>

0026The transit time difference t_{m + 1} between the transducer element at position E and the transducer element at position A is calculated as follows:<maths id="math0010" num=""><img file="EP0450191A2_D0010.tif" /></maths> These runtime differences t_m and t_{m + 1} always result between the transducer elements at the borders of neighboring groups 24/23 or 23/22 or 22/21. Positions F, E, D correspond to positions D, A, B etc.

0027If one adds the delay time τ in the direction generator to the transit time difference t, the result at reception under the grating-lobe angle β is: at position E the received signal <maths id="math0011" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>)</mtext></mrow></msup><mtext>,</mtext></mrow></math><img file="EP0450191A2_D0011.tif" /></maths> where ω · τ_β is any initial phase. This reception signal at position E is not delayed, at position D the received signal <maths id="math0012" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ t</mtext></mrow></msup><msup><mrow><mtext>m</mtext></mrow><mrow><mtext>)</mtext></mrow></msup><mtext>,</mtext></mrow></math><img file="EP0450191A2_D0012.tif" /></maths> the un τ_m is delayed, and after the insertion of (1) and (3) the delayed signal<maths id="math0013" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ mλ / c)</mtext></mrow></msup><mtext>,</mtext></mrow></math><img file="EP0450191A2_D0013.tif" /></maths> at position A the receive signal <maths id="math0014" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ t</mtext></mrow></msup><msup><mrow><mtext>m + 1</mtext></mrow><mrow><mtext>)</mtext></mrow></msup><mtext>,</mtext></mrow></math><img file="EP0450191A2_D0014.tif" /></maths> that by the delay time τ_{m + 1} is delayed, and after the insertion of (2) and (4) the delayed signal<maths id="math0015" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ m λ / c + 3 λ / 2c)</mtext></mrow></msup><mtext>,</mtext></mrow></math><img file="EP0450191A2_D0015.tif" /></maths> at position B the receive signal<maths id="math0016" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ t</mtext></mrow></msup><msup><mrow><mtext>m + 1</mtext></mrow><mrow><mtext>+ t</mtext></mrow></msup><mtext>m),</mtext></mrow></math><img file="EP0450191A2_D0016.tif" /></maths> that around τ_{m + 1}+ τ_m is delayed, and after insertion of (1), (2), (3) and (4) the delayed signal<maths id="math0017" num=""><math display="inline"><mrow><msup><mrow><mtext>U · e</mtext></mrow><mrow><mtext>jω (t + τ</mtext></mrow></msup><msup><mrow><mtext>β</mtext></mrow><mrow><mtext>+ m · 2 · λ / c + 3 λ / 2c).</mtext></mrow></msup></mrow></math><img file="EP0450191A2_D0017.tif" /></maths> After addition you get<maths id="math0018" num=""><img file="EP0450191A2_D0018.tif" /></maths> It can be seen that the 1.5 times the distance d causes a phase shift between the received signals at D and A by 180 ° or λ / 2. Within groups 21, 22, 23, 24, the delayed signals are added in phase, but shifted from group 21/22 or 22/23 or 23/34 against each other by half a wavelength, so that the delayed received signals are summed at even Number of groups 22, ..., 24, zero results. In contrast to this, a compensation of the received signals is achieved by compensation in the directional generator when sound is incident from the swivel angle ζ.

0028FIG. 2 shows a diagram in which directional sensitivity R / dB is plotted against the angle ϑ for a directional characteristic of a converter arrangement according to FIG. 1, which consists of q = 20 groups, each group having, for example, a number of converters z = 5. The direction generator is set so that its main lobe 30 in the maximum swivel angle ζ_Max points. The grating-lobe angle β is located in an angular range 31, which is limited by the two highest fragmented grating praise 32, 33, which have an attenuation of R1 in relation to the directional sensitivity R of the main lobe 30. In the angular range 31 around the grating-lobe angle β, the damping is substantially larger, approximately three times as large as R1. In addition, so-called. Pseudo-grating praise 34, 35, 36, 37 and 38 are recorded, which have almost the same angular distances from each other and whose damping is greatest near the main lobe.

0029FIG. 3 shows the course of a directional characteristic over the angle ϑ at which the same number N = 100 of converter elements are accommodated with the same extension of the converter arrangement as in FIG. 2. However, their distances from one another are stochastic or noisy. The secondary level attenuation is almost constant over the entire angular range and is somewhat less than the fragmented grating praise 32 and 33 in FIG. 2. At the grating-lobe angle β itself, the attenuation R2 is not as high as in the converter arrangement according to the invention. The damping is comparable over the entire angular range.

0030In order to level the so-called pseudo-grating praise 33 to 38 according to FIG. 2, the number of converters z of the q groups is varied. 4 shows such a transducer arrangement with N = 100 transducer elements, which are arranged over an extension L of, for example, 1.20 m. 100 converter elements are divided into q = 20 groups 110, 111, ..., 129. The distance d is calculated from the dimension L:<maths id="math0019" num=""><math display="inline"><mrow><mtext>L = (N-1) d + (q-1) x 0.5 x d</mtext></mrow></math><img file="EP0450191A2_D0019.tif" /></maths><maths id="math0020" num=""><math display="inline"><mrow><mtext>L = 108.5 d.</mtext></mrow></math><img file="EP0450191A2_D0020.tif" /></maths> At a maximum frequency of 100 kHz, the distance d = 0.75 · λ. The individual transducer elements in each group are spaced 0.75 λ apart, the groups are spaced 1.5.0.75 λ apart.

0031The first group 110 located on the left outer edge has only one converter element, the neighboring group 111 two, the group 112 three converter elements, the group 113 four converter elements, the group 114 five converter elements, the groups 115 and 116 six converter elements, the group 117 seven converter elements and groups 118 and 119 each have eight converter elements. The number of transducers z in the following groups have the same size symmetrically with respect to the center 11. The groups with the even numbers 110, 112, ..., 128 form a sub-base 200, the groups 111, 113, ..., 129 with odd numbers form a second sub-base 300. The sub-bases 200, 300 are interleaved and reversed mirror symmetry. Each sub-base 200, 300 has a grid of d, which is shifted from one another by d / 2.

0032The number of transducers z of the q groups are selected so that a directional characteristic according to FIG. 5 with a corresponding directional element when pivoting by the maximum pivoting angle _Max is achieved. This directional characteristic is characterized by the fact that a maximum attenuation is achieved around the grating-lobe angle β and that no further periodic components in the directional characteristic are recorded. The secondary levels in the area of ​​the main lobe 30 are also particularly strongly damped. In order to obtain such a pattern of the directional characteristic, the following dimensioning instructions have been observed: Starting from the center 11, in the case of an amplitude shading of the transducer elements of "1", the product from the distance from the perpendicular to the transducer element is multiplied by the amplitude evaluation factor "1". All products for sub-base 200 are added with the correct sign and divided by the sum of the amplitude evaluation factors - here half of the plurality N of converter elements. If possible, this value must be zero. Then the focus of each sub-base 200 and 300 is on the middle 11. With this dimensioning specification it is achieved in particular that no pseudo-grating praise arises.

0033For subgroup 200, ie for groups 110, 112, ....., 128, the following must apply:<maths id="math0021" num=""><img file="EP0450191A2_D0021.tif" /></maths> The focus of subgroup 200 is thus in the middle 11 of the transducer arrangement. The same applies to the sub-base 300.

0034The arrangement shown in FIG. 4 can be used particularly advantageously in a waterborne sound system in which the pulse mode is used, the pulse duration being, for example, Δ t = 0.1 ms. 4, q = 20 groups are distributed over the entire extent L = 1.2 m, so that the average length of two groups corresponds to approximately 12 cm. When swiveled by ζ_Max= 45 ° and an incidence of sound waves at the grating lobe angle β = 39 °, on average at least two groups are simultaneously swept by sound waves, which corresponds to a length 1 on the straight line of the transducer arrangement of<maths id="math0022" num=""><img file="EP0450191A2_D0022.tif" /></maths> where c = 1500 m / s is the speed of sound. Length 1 is thus somewhat greater than the average length of two groups on the converter arrangement according to FIG. 4. Damping distance and damping of the fragmented grating praise 31, 32 with respect to the main lobe 30 in pulse operation is shown in dashed lines in Fig. 5 and much better than in monochromatic continuous sound operation with f = 100 kHz. Similarly favorable attenuation curves can be recorded for broadband reception around a center frequency of 100 kHz.

00356 shows a diagram in which the standard dimension R in dB for a different number q of groups is entered over the angle Winkel. It is at the angle ϑ = ζ_Max entered the sensitivity of the main lobe 30 and the sensitivity of the grating praise at the grating lobe angle β. The sensitivities are the same when the transducer arrangement has equidistantly distributed transducer elements whose spacing is greater than half the wavelength. The incident energy over the grating-praise angle β is distributed through the group-wise arrangement of the transducer elements to adjacent angular ranges, whereby an attenuation is achieved in the entire angular range, which is greater than the attenuation specified for q = 20, which is equal to the reduction R 1 Is the standard. For q = 20, two points are entered on two curves r and s, which limit the angular range 31 according to FIG. 2 and correspond to the fragmented grating praise 32, 33 in FIG. 2. The curves r and s indicate limit values ​​for the damping of the fragmented grating praise for the different number q of groups. For increasing number q of groups, the two curves r and s asymptotically approach a limit value R₀, which corresponds to the damping, if the transducer distances are statistically distributed. 6, the number q of groups is to be dimensioned as a function of the task of the entire sonar system.