1 AUSTRALIA Patents Act 1990 ATLAS ELEKTRONIK GMBH COMPLETE SPECIFICATION STANDARD PATENT Invention Title: An acoustic underwater antenna, a submarine with such an antenna, and also a method for establishing the bearing, location and/or classification of a target by means of such an antenna The following statement is a full description of this invention including the best method of performing it known to us:- 2 AN ACOUSTIC UNDERWATER ANTENNA, A SUBMARINE WITH SUCH AN ANTENNA, AND ALSO A METHOD FOR ESTABLISHING THE BEARING, LOCATION AND/OR CLASSIFICATION OF A TARGET BY MEANS OF SUCH AN ANTENNA 5 The invention concerns an underwater antenna to be fitted to a hull of a boat, a submarine with an acoustic underwater antenna, and also a method for establishing a bearing, location and/or classification by means of an acoustic underwater antenna. 10 On board a vessel, in particular a submarine, are usually located a plurality of acoustic underwater antennas, which are installed at different locations on board the submarine and are optimally designed for different receiving frequency domains (Fig. 1). 15 DE 199 09 485 Cl shows, for example, an electroacoustic transducer array for an underwater antenna in which a plurality of transducer elements with piezoelectric ceramic bodies; with head and tail masses in the manner of an acoustic mushroom, are mounted together on a support. Here the transducers have a standardised structure. 20 EP 0 654 953 B1 shows, an further electroacoustic transducer array for underwater antennas made up of a plurality of hydrophones arranged equidistantly vertically above one another on a support. These hydrophones are embedded, together with a reflector that is arranged behind them in the incident sound direction, in an acoustically transparent hard enclosing casting. A bar-shaped transducer array of this 25 kind is generally called a stave, and by virtue of the hydrophones being located vertically one above another, with suitable signal processing of the hydrophone output signals, possesses a directional characteristic with a sufficiently narrow main lobe, even in the vertical direction. 30 The underwater antenna represented here is embodied as a cylinder base, whereby the individual staves are positioned on a cylindrical support. Cylinder bases of 3 this kind, and also horseshoe bases, or conformal arrays, are primarily utilised for purposes of passive acoustic location in the frequency domain between 1 and 12 kHz, in order to detect the broadband noises associated with the movement of vessels. Such underwater antennas allow location over a panoramic angle of up to 360 degrees using 5 cylinder bases and a somewhat more limited location sector using horseshoe bases. In EP 2 010 936 B1 an underwater antenna is used to establish a bearing of sound-radiating, i.e. sound-generating or sound-reflecting, targets; this antenna is fixed to the starboard and port sides of an underwater vessel. An underwater antenna of this 10 kind, which is designated as a flank array or a lateral antenna, has a multiplicity of electroacoustic transducers, which are ranked one behind another, equidistantly spaced at a distance d from one another. Thus for purposes of establishing a bearing it spans a reception sector in the lateral angular domain of the vessel of almost 180 degrees. Since the receiving frequency domain can usually be exploited in the low and medium 15 frequency domains, an underwater antenna of this kind possesses a large coverage. DE 10 2006 045 686 B3 shows, for example, an unmanned underwater vessel for purposes of reconnoitring a sea area. For this purpose the vessel utilises lateral antennas arranged on the port and starboard sides, a flank array, and a bow sonar, 20 wherein the flank array receives low frequency sound signals and the bow sonar receives high frequency sound signals. When a vessel that is radiating sound is detected the bearing of this vessel is established. US 4 910 719 shows for example, a transducer array for the additional 25 determination of the distance of the vessel, in which three sensors are arranged in a line on the side of an underwater vessel, and have a predetermined spacing relative to one another. By this means a curved wavefront of an incident sound wave reaches each of the three sensors with a time difference. Here the time differences are dependent on the distance of the vessel and the direction of incidence of the sound waves. Thus the 30 distance and bearing of the vessel can be determined, for example by means of correlation. The method presented here, also known as the passive ranging sonar 4 method, operates more accurately in determining the distance of a sound radiating vessel, the larger the spacings are between the three sensors. DE 196 12 503 C2 shows an electroacoustic transducer module for the 5 perception of intercept functions. Such a transducer module serves to record high frequency sound pulses, which are usually transmitted by other sonar equipment, in order to locate the vessel carrying this sonar equipment. The sound pulses received are usually further analysed with regard to their frequency domain, type of modulation, pulse length and the pulse repetition frequency, in order to classify and identify targets. 10 DE 10 2004 037 987 Al shows an electroacoustic underwater antenna, in particular a lateral antenna that can be attached to the outer skin of underwater vessels, in which the hydrophones are arranged in rows and columns on a plastic body. An underwater antenna of this kind combines the acoustic advantages of a flank array with 15 regard to its receiving sensitivity in the low frequency range, and the advantages of a cylinder base or horseshoe base with regard to good directionality of the vertical reception domain. DE 36 33 991 Al shows a transducer array, which is configured so as to 20 generate a directional characteristic with a constant aperture angle within a wide frequency domain. For this purpose the frequency domain is subdivided into frequency bands and for each frequency band an equal number of transducers are combined to form a transducer group. The transducer groups are fitted over the length of the transducer array, nested within one another in a space-saving manner. 25 A multiplicity of underwater antennas of this kind disadvantageously leads to increasing manufacturing and maintenance costs. Since the underwater antennas conventionally form self-contained units, the diverse manufacturers of individual underwater antennas require special signal processing units for the processing of the 30 respective special functions of the respective underwater antenna.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the fidd relevant to the present disclosure as it existed. before the prority 5 date of each claim of this application. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of 10 any other element, integer or step, or group of elements integers or steps, In a first aspect, there is provided an acoustic underwater antenna to be fitted to a hull of a vessel, the antenna comprising a multiplicity of electroacoustic and/or optoacoustic transducers and/or transducer arrays, in particular staves, arranged with 15 spacings next to one another, for the transmission and/or reception of sound waves. wherein one or a plurality of the transducers and/or transducer arrays form an antenna seOgment, the antenna segments can be fitted to the hull of the vessel such that the range of 20 the antenna, depending on the dimensions of the vessel, extends from the stern region of the vssel along the side of the vessel as far as the bow, around the bow; and along the other side of the vessel as far as the stern region, and the density of the transducers and/or transducer arrays in at least one local area in the range of the antenna is greater than the density of the transducers and/or 25 transducer arrays in other areas in the range of the antenna, such that a zone of locally increased density of the transducers and/or transducer arrays can be provided at one or more desired locations on the hull of the vessel. In a second aspect, there is provided a submarine with an acoustic underwater 30 antenna fitted to its hull, the antenna comprising a multiplicity of electroacoustic and/or optoacoustic transducers and/or transducer arrays, in particular staves, arranged 6 with spacings next to one another, for the transmission and/or reception of sound waves, wherein: one or a plurality of the transducers and/or transducer arrays form an antenna segment, 5 the antenna segments are arranged on the hull of the submarine such that the range of the antenna, depending on the dimensions of the submarine, extends from the stem region of the submarine along the side of the submarine as far as the bow, around the bow, and along the other side of the submarine as far as the stern region, and the density of the transducers and/or transducer arrays in at least one local area 10 in the range of the antenna is greater than the density of the transducers and/or transducer arrays in other areas in the range of the antenna, such that a zone of locally increased density of the transducers and/or transducer arrays can be provided at one or more desired locations on the hull of the vessel. 15 In a third aspect, there is provided a method fbr establishing the bearing, location and/or for classification of a sound radiating target by means of an acoustic underwater antenna in accordance with the first aspect above, By providing the zone of increased transducer density, the spacing between the 20 transducers or transducer arrays is reduced and embodiments of the invention are able to process high frequency sound pulses, which facilitates execution of intercept funetions.
6a Disclosed heren is an acoustic underwater antenna to be fitted to a hull has a ndtiplicity of electroacouste andor optoacoustie transducers or transducer arrays arranged next to one another, for the transmission and/or reception of sound waves. The transducers or transducer arrays arranged next to one another also called staves, form 5 one or a plurality of antenna segments, which ranked together form the underwater antenna. These antenna segments are configured so as to be mounted on the hull of the vessel, and in particular such that this underwater antenna advantageously extends from the stern along the side of the vessel on the starboard side as far as the bow, around the bow, and along the side of the vessel on the port side as far as the stern, Since the 10 underwater antenna follows the external shape of the vessel the range/compass of the antenna is dependent on the dimensions of the vessel, An increase in performance may advantageously be achieved with an embodiment of the underwater antenna, with improved low and medium frequency detection, since the anterma area utiiised to cover 7 the functions of a conventional lateral antenna is longer by comparison than the length of a conventional lateral antenna. In a preferred form of embodiment of the invention a central signal processing 5 unit is advantageously installed downstream of the underwater antenna for purposes of further processing of the transducer signals. The signals transmitted and/or received by all transducers and/or transducer arrays are supplied to the signal processing unit for purposes of controlling the frequency domain and aperture of the total antenna. 10 In a further preferred form of embodiment of the invention a frequency domain in which sound waves can be transmitted and/or received can be selected for each antenna segment. The selection of the frequency domain is advantageously undertaken by the activation or deactivation of transducers or transducer arrays. Thus the antenna segments are advantageously configured so as to cover a multiplicity of diverse 15 frequency domains that are required for the detection and location of sound radiating targets. In accordance with a further preferred form of embodiment of the invention the zone of locally increased transducer density is located in the vicinity of the bow and/or 20 stem and/or the centre of the vessel. An increase of the transducer density at the bow, stem, and, if required, at the centre of the vessel, enables a passive estimation of the distance of the target, for example by the deployment of passive ranging sonar methods, with a high signal-noise ratio. In addition to establishing a bearing of a sound radiating vessel this also enables a determination of the distance to this vessel. 25 In a further form of embodiment of the invention the underwater antenna can be operated in parallel both actively and passively with selected transducers and/or transducer arrays for the transmission and reception of sound waves. Thus a parallel application of the active ranging sonar method and the passive ranging sonar method is 30 advantageously possible, whereby a more accurate estimation of the distance to the sound radiating vessel and thus a higher quality of target parameter analysis is effected.
8 In accordance with a further preferred form of embodiment of the invention all transducers and/or transducer arrays of the underwater antenna are standardised in their design. Thus the advantage of low manufacturing costs and maintenance costs for the 5 underwater antenna may be achieved. In a further form of embodiment of the invention any of the transducers can be selected to form antenna segments. Here the selected transducers can be utilised in one or a plurality of antenna segments, and the antenna segments can be formed such that 10 they are adjacent and/or overlapping and/or spaced apart. In this manner it is possible to produce special, function-oriented antenna segments, which advantageously cover special antenna functions. In a further preferred form of embodiment of the invention the individual 15 antenna segments can be controlled with respect to their utilisation and/or function. The control is advantageously undertaken by means of a control unit, in that one, a plurality, or all transducers and/or transducer arrays can be switched on and/or switched off by means of a switching device. This form of control is undertaken according to circumstances, as a result of which the advantage arises of saving power, because not 20 all the transducers are always in operation at the same time. By this means, for example, a submarine can travel greater distances while submerged. An alternative configuration of the invention provides for a submarine with an inventive acoustic underwater antenna, in which the antenna segments are arranged on 25 the hull of the submarine such that the compass of the antenna, depending on the dimensions of the submarine, extends from the stem region of the submarine along the side of the submarine as far as the bow, around the bow, and along the other side of the submarine as far as the stem region. 30 In accordance with a further alternative form of embodiment of the invention for purposes of establishing a bearing, location and/or classification by means of the 9 inventive underwater antenna, the antenna segments of this underwater antenna are fitted to the hull of a vessel, whereby the compass of the antenna, depending on the dimensions of the vessel, extends from the stern region of the vessel along the side the vessel as far as the bow, around the bow, and along the other side of the vessel as far as 5 the stem region. In a further preferred form of embodiment of the invention a first bearing is firstly established in a reception sector by means of one or a plurality of antenna segments of the inventive underwater antenna, and with the detection of a sound 10 radiating target a second bearing is established in this reception sector, whereby the resolution of the second bearing is improved compared with that of the first bearing, and the improvement in resolution is achieved by means of the activation of transducers or transducer arrays. By establishing bearings within a reception sector with different resolutions the advantage arises of saving energy since the number of transducers in 15 operation is varied as required. In accordance with a further form of embodiment of the invention antenna functions of at least two antennas from a group of antennas, namely a cylinder base, horseshoe base, intercept base, passive ranging sonar / active ranging sonar base, flank 20 array, laminar lateral antenna, are executed by means of the inventive acoustic underwater antenna, whereby the transducers and/or transducer arrays generate transmission signals and/or reception signals, which are processed by a central signal processing unit, The combination of separate antenna functions and the execution of these functions with one antenna has the advantage of economising on individual, 25 separate antennas on board the vessel. Further advantageous forms of embodiment of the invention ensue from the dependent claims and from the examples of embodiment elucidated in more detail with the aid of the attached drawing. In the drawing: 30 10 Fig. shows a submarine with a plurality of underwater antennas separately arranged in accordance with the prior art, Fig. 2shows a submarine with an integrated acoustic underwater antenna, 5 Fig. 3 shows a schematic representation of a linear antenna, and Fig. 4shows a schematic representation of a plurality of antenna segments. 10 Fig. I represents a submarine 2 with a plurality of separately arranged underwater antennas in accordance with the prior art. An intercept base 4 is located in each of the fore and aft areas of the submarine 2 for the reception of high frequency sound pulses. 15 On each of the two longitudinal sides of the submarine 2 is located a lateral antenna 6, also called a flank array, which is designed for operation in the low and medium frequency domains. 20 Also arranged on either side of the submarine 2 are three sub-bases of a passive ranging sonar base 8; these are used for the passive determination of the distance of a sound radiating target. By means of a cylinder base 10 on the bow of the submarine 2 the broadband 25 noises associated with the movement of a vessel are evaluated. Furthermore, the direction of incidence of a sound pulse is determined by means of the cylinder base 10. On the bow of the submarine 2 is also located a horseshoe base 12, also called a conformal array, for purposes of locating a sound source with a broadband radiation of 30 sound waves.
11 In contrast, Fig. 2 shows a submarine 2 with an inventive, integrated acoustic underwater antenna 14. The functions of the separately arranged underwater antennas 4, 6, 8, 10, 12, 14 5 represented in Fig. 1 are integrated in the inventive underwater antenna 14 represented in Fig. 2. In an alternative form of embodiment of the invention, however, individual functions of one or a plurality of the underwater antennas represented in Fig. 1 are also integrated in the inventive underwater antenna. 10 For this purpose this underwater antenna 14 runs from the right-hand side of the stern region to the bow, around the bow, and to the left-hand side of the stem, and is adapted to the shape of the submarine 2. An appropriate design of this underwater antenna 14 is provided with a support, 15 which corresponds to the dimensions of the underwater antenna 14, for purposes of fitting the underwater antenna 14 to the hull of the submarine 2. Transducers are attached to this support for the transmission and/or reception of sound waves. For purposes of matching the underwater antenna 14 to diverse 20 frequencies the transducers are arranged at various spacings within the underwater antenna 14. For purposes of processing the sound signals in the low frequency domain the transducers of the underwater antenna 14 are spaced further apart in the lateral region than in the bow region, since in the bow region the antenna 14 predominantly processes higher frequencies. 25 Fig. 3 shows a schematic representation of a linear antenna for purposes of elucidating the arrangement of the transducers of the underwater antenna. On a longitudinal axis 16 of the underwater antenna the transducers 18 are equidistantly ranked one behind another with a spacing d. Furthermore, the phase front of an incident 30 sound wave 20 is schematically represented in Fig. 3, which impacts onto the 12 transducers 18 at an angle ® relative to the direction 22 at right-angles to the underwater antenna 14. If the signals of a plurality of transducers 18 are connected together to form a 5 group, then the underwater antenna 14 has its highest sensitivity, i.e. its main lobe, in the direction 22 at right-angles to the underwater antenna 14. In order to swing the antenna sensitivity into other directions also, the signals received by the transducers 18 are provided with appropriate time delay coefficients and are then added without any phase displacement. The main lobe of the underwater antenna 14 can thus be directed 10 in any direction within a reception sector, in order to evaluate the signals there present with the maximum antenna gain. The maximum frequency that can be evaluated and the aperture angle of an underwater antenna 14 are on the one hand determined by the number of transducers 15 18, and on the other hand by the spacing d of the transducers relative to one other. From antenna theory the spacing d is given by d A/2, 20 where A is the wavelength of the incident sound waves 20. However, ambiguities arise in the evaluation of frequency components with a wavelength of A /2 s d, since secondary maxima, i.e. grating lobes, form on either side of the primary maximum in the directional characteristic. An unambiguous location of 25 sound sources is thus no longer possible. If one transfers this across to the lateral region of the inventive integrated underwater antenna 14, one obtains, for a maximum frequency that can be evaluated in the medium and low frequency domains, a related maximum transducer spacing d. 30 13 However, the intercept functions and the passive ranging sonar / active ranging sonar functions cited in the introduction process high frequency sound pulses. For purposes of integrating such functions the inventive underwater antenna 14 has local regions in which the spacing d of the transducers is reduced, i.e. the transducer density 5 is increased. A higher transducer density is preferably provided at the bow and/or at the stem and/or at the centre of the vessel. Here it is not absolutely essential to arrange the transducers 18 homogeneously with the same spacing d, since a downstream signal processing unit has the means to 10 process signals received by selected transducers 18. For this purpose a suitable means of selection selects according to the frequency domain that is to be evaluated the transducers 18 that are to contribute to the antenna function. An appropriate switching device switches the transducers 18 on and off respectively and can thus conduct an adaptation to frequency and can alter the aperture of the underwater antenna. For the 15 case in which not all transducers are in operation, but just the selected transducers, the spacing d of the transducers being used increases, and the power consumption of the underwater antenna 14 reduces. The transducers 18 are preferably functionally combined into antenna segments. 20 This enables a utilisation of the integrated underwater antenna 14 according to circumstances. For purposes of exercising a method for the location and/or classification of sound radiating targets by means of the inventive acoustic underwater antenna a first bearing is firstly established, also known as coarse listening, with one or a plurality of antenna segments in a reception sector. If the coarse listening results in 25 the detection of a target, a second bearing, also known as a fine bearing, is established in this reception sector. In order to obtain a more accurate detection of the target as the fine bearing is being established, the resolution of the bearing is increased compared with that for the coarse bearing. This is achieved by the switching in of further transducers or antenna segments. 30 14 Fig. 4 shows a schematic representation for the formation of antenna segments, A (linear) section of the underwater antenna 14 is represented, in which transducers 18 are combined into antenna segments 25, 26, 27. The combination of the transducers into an antenna segment 25, 26, 27 can be undertaken in any suitable manner. The 5 transducers 18 do not have to be in sequence; it is possible to combine every second, or third, or fourth transducer 18 etc. The combined transducers 18 are symbolically identified in Fig. 4 with a circle, an X, and a square, whereby fifteen "circle" transducers form the antenna segment 25, four "square" transducers form the antenna segment 26, and six "X" transducers form the antenna segment 27. 10 However, the selected transducers 18 utilised preferably have the same spacing d relative to one another within the antenna segment. The individual antenna segments 25, 26, 27 can also be arranged such that they overlap or are spaced apart, 15 The above described properties of a linear antenna can also be transferred across to non-linear antennas, such as find particular application in the bow region of the vessel. Since the conventional cylinder bases or horseshoe bases in the bow region of 20 the vessel are predominantly utilised in the single-figure and/or lower two-figure kHz domain, in order to detect the broadband noises associated with the movement of vessels the inventive integrated underwater antenna 14 has a higher transducer density in the bow region than in the lateral region. 25 For the purpose of their summation without any phase displacement, the signals received by the individual transducers 18 are delayed in time as though the incident sound waves 20 reach the transducers 18 simultaneously at their fictitious locations on a line aligned at right-angles to the main direction of the directional characteristic, whereby the fictitious locations are determined by means of a projection of the actual 30 locations of the transducers at right-angles onto the lines cited.
15 Here the transducers 18 that are operated together are combined into groups. These can either be adjacent transducers 18, or every second, or every third, or every fourth, etc; these then form an antenna segment. 5 The integrated underwater antenna 14 in accordance with Fig. 2 is roughly subdivided into three regions. These include two lateral regions and one bow region, whereby the regions merge from one to another without fixed structural boundaries. Conventionally an increase of the frequency to be resolved unambiguously leads 10 to a deterioration of the aperture angle, since for this purpose the aperture length of the antenna is reduced. By means of a central signal processing unit, however, the inventive underwater antenna 14 possesses the option of extending the individual antenna domains and thus, for example, maintaining the length of the antenna aperture used as frequency increases. 15 In the example of embodiment of the acoustic underwater antenna 14 described in accordance with Fig. 2 standardised transducers 18 are used for the construction of such an antenna 14. This ensures low manufacturing and maintenance costs, 20 An alternative configuration of the underwater antenna 14 envisages an application of transducer arrays, in particular staves, for the construction of an underwater antenna 14 of this kind. In one stave a plurality of electroacoustic or optoacoustic transducers are arranged spaced apart vertically one below the other. The number of transducers arranged vertically one below the other determines the vertical 25 aperture angle of the directional characteristic of the underwater antenna 14. The above described properties of the inventive integrated underwater antenna 14 can be analogously transferred across to an underwater antenna 14 with the use of transducer arrays or staves of this kind. 30 In a further alternative configuration of the underwater antenna 14 provision is made for the distribution of the transducers 18 or transducer arrangements, in particular 16 staves, to be homogeneous over the whole underwater antenna 14 on the basis of the highest frequency that is to be evaluated. The utilisation of low frequency domains is then achieved by the equidistant omission of transducers 18 or staves. 5 All the features cited in the above description of the figures, in the claims and in the introduction to the description can be deployed both individually and also in any suitable combination with one another. Thus the disclosure of the invention is not limited to the combinations of features that have been described and/or claimed. Rather all combinations of features are to be considered as disclosed.