DE102019204840A1 - Location signal receiver for the detection of an underwater object with distorted directional characteristics - Google Patents

Abstract

A location signal receiver 20 for detecting an underwater object is shown. The locating signal receiver has a receiving arrangement 22 comprising a plurality of receiving units 22a, 22b, 22c, the receiving units 22a, 22b, 22c being designed to receive sound waves 26 and to generate an output signal 28. Furthermore, the locating signal receiver has an evaluation unit 24, which is designed to impart a directional characteristic 30 to the receiving arrangement 22 by processing the output signal 28, the directional characteristic 30 for sound waves 26 being distorted from a predetermined direction 32, so that the receiving arrangement 22 is in the predetermined direction 32 has a reduced sensitivity. The evaluation unit 24 is designed to evaluate the processed output signal 28 and to detect the underwater object 21 in the evaluated output signal 28.

Description

The invention relates to a location system that can detect underwater objects, in particular by means of sonar.

Conventional location systems to detect underwater objects have the disadvantage that the transmitter of a sonar signal or another interferer superimposes received location signals and therefore any underwater objects cannot be identified or can only be identified with difficulty. Methods such as adaptive beamforming can help here by hiding the interferer, but are very computationally intensive due to their continuous dynamic adaptation, for example by changing their covariance matrix.

The object of the present invention is therefore to create an improved concept for the detection of underwater objects.

The object is achieved by the subject matter of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

Exemplary embodiments show a location signal receiver for the detection of an underwater object. The locating signal receiver has a receiving arrangement and an evaluation unit. The receiving arrangement comprises a plurality of receiving units, the receiving units being designed to receive sound waves and to generate an output signal. The output signal is advantageously a signal, in particular an electrical signal, corresponding to the sound waves. A receiving unit can be a hydrophone. The evaluation unit is designed to impart a directional characteristic to the receiving arrangement by processing the output signal, the directional characteristic for sound waves being distorted from a predetermined direction, so that the receiving arrangement has a reduced sensitivity in the predetermined direction. The output signal can have one signal per receiving unit, the evaluation unit processing each signal separately. Furthermore, the evaluation unit is designed to evaluate the processed output signal and to detect the underwater object in the evaluated output signal. Such a directional characteristic that is asymmetrical about a main lobe of the directional characteristic can be regarded as a distorted directional characteristic. In an alternative consideration, a distorted directional characteristic is considered to be a directional characteristic which has a zero, in particular as wide as possible, in a predetermined direction, in particular the direction of a jammer. The main lobe is the lobe in the directional characteristic that points in the main receiving direction. The zero point becomes wider if, in addition to the zero point, the derivative of the directional characteristic in the specified direction is zero.

Such a location signal receiver is advantageous because it is not based on a dynamic adaptation of its directional characteristic but statically on a static adaptation of the same. This means that the adaptation of the directional characteristic in order to mask out the interferer is based on preliminary information about the reception conditions, in particular the position or at least the direction of the transmitter. The preliminary information can be known a priori, for example when a watercraft sends out a location signal and the reflections are received with a towing antenna. The towing antenna can then block out the direct sound of the location signal and / or noises from the watercraft. The direction from which the interfering noises come is then known, and the directional characteristic can be set once. The same applies to other sound sources whose direction is known.

The directional characteristic can be generated by a suitable control vector which is applied to the output signal of a receiving unit. In this way, each receiving unit can be assigned a weighting value, in particular a complex one (i.e. for amplitude and phase). The control vector can be selected appropriately for a special viewing direction. A further corresponding control vector can be determined for each further viewing direction (or main receiving direction) in which the receiving arrangement is to be directed. The directional characteristic can also be frequency-selective, i.e. the directional pattern lobes can have different shapes for different frequency bands. Then there is a control vector per frequency band or the control vector has individual weights for each frequency band.

In any case, the distorted directional characteristic is known in advance or is determined once, so that in comparison to classic beamforming, in which a static undistorted directional characteristic is used, there is no or only a minimally increased computing effort. Thus, with a significantly reduced Computing power compared to known methods provides the same results in terms of masking out interferers in the output signal. Classic beamforming is called delay-and-sum beamforming.

A frequency-selective directional characteristic also has the advantage that a jammer that transmits in a different frequency band than the underwater object, but is essentially in the same direction as the underwater object, can be suppressed or at least damped.

In exemplary embodiments, the evaluation unit is designed to determine the predetermined direction (also referred to as bearing) from the received or processed sound waves and to distort the directional characteristic for subsequent sound waves. This is particularly advantageous if the interferer, in particular its direction in relation to the receiving arrangement, is not known.

In exemplary embodiments, the directional characteristic can then only be distorted for one frequency band. This is advantageous if the interferer transmits essentially in a (known) frequency band. In further exemplary embodiments, the evaluation unit is designed to determine a frequency band from the received or processed sound waves in which interference noises occur and to distort the directional characteristic for the determined frequency band for subsequent sound waves in order to suppress the interference noises. This means that the frequency band to be distorted can be determined individually for the current situation using the evaluation unit, for example if the interferer is an unknown object. Additionally or alternatively, the frequency band can also be determined in advance, especially if the interferer is known. The frequency band can have any width, it being advantageous if the frequency band comprises at least dominant frequencies of the interferer. Outside the frequency band, the receiving arrangement is also designed to detect sound waves.

In further exemplary embodiments, the evaluation unit is designed to transform the output signal for processing into the frequency range and to generate the directional characteristic in the output signal by adapting a phase and / or an amplitude of a signal from one (or more) receiving unit. This means that the various hydrophone signals can be (each) delayed (phase adjustment), but individual amplitudes of frequencies or frequency bands can also be weighted, in particular attenuated. In this case, the frequencies or the frequency band can be adjusted via all hydrophone signals.

A location system for detecting an underwater object is also disclosed. The location system has the location signal receiver described above and a location signal transmitter. The locating signal transmitter is designed to emit a locating signal that can be received by the locating signal transmitter. In particular, the location signal transmitter is arranged remotely from the location signal receiver. The evaluation unit can distort the directional characteristic for the direction in which the locating signal transmitter is arranged. This makes it possible to block out the (very loud) direct sound of the location signal transmitter, so that only any reflections (also called echoes) of the location signal are detected. For example, the location signal can be transmitted by means of a watercraft, for example a ship or a submarine. The locating signal in particular has a sonar pulse or a sequence of sonar pulses. Reflection from the underwater object can be received by means of a towing antenna arranged on the watercraft. By distorting the directional characteristic, however, the direct sound that hits the receiving arrangement, that is to say the towing antenna, from the watercraft in a short time can be masked out. This is done without great computational effort, which would require adaptive beamforming, for example.

In exemplary embodiments, the location signal receiver moves on a predefined route, which can have changes in direction. The evaluation unit is then designed to adapt the directional characteristic in accordance with the predefined route, so that the reduced sensitivity is continuously aligned in the direction of the locating signal receiver. In the case of the previous example, the watercraft can thus perform a predetermined maneuver and use the position of the watercraft to the receiving arrangement, which position is known through the predetermined maneuver, in order to distort the directional characteristic in the direction of the watercraft and so to suppress or at least dampen the direct sound thereof. Furthermore, any curvature of the trailing antenna can be taken into account when shaping the directional characteristic. Thus, at the beginning of the predefined route, a sequence of control vectors can be determined or provided, which the evaluation unit applies to the output signal of the receiving arrangement at predetermined intervals.

Exemplary embodiments show a method for detecting an underwater object with the following steps: receiving sound waves with a plurality of receiving units, which form a receiving arrangement, and generating output signals by the receiving units; Impressing a directional characteristic onto the output signals, the directional characteristic for sound waves being distorted from a predetermined direction, so that the receiving arrangement has a reduced sensitivity in the predetermined direction; Evaluation of the processed output signals in order to detect the underwater object in the evaluated output signals.

The method can be implemented in a program code of a computer program for carrying out the method when the computer program runs on a computer.

• 1: eine schematische Darstellung eines Ortungssignalempfängers; und
• 2: eine schematische Darstellung eines Ortungssystems.

Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. Show it:

• 1 : a schematic representation of a location signal receiver; and
• 2 : a schematic representation of a location system.

Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally identical or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that they are shown in different exemplary embodiments Description of these elements is interchangeable or can be applied to each other.

1 shows a schematic representation of a location signal receiver 20 for determining a position of an underwater object 21 , The location signal receiver 20 has a receiving arrangement 22 with a plurality of receiving units 22a . 22b . 22c and an evaluation unit 24 on. The receiving unit 22 is trained to sound waves 26 to receive and, equivalent to the sound waves, an output signal 28 to create.

The evaluation unit 24 receives the output signal 28 from the receiving arrangement 22 , By processing the output signal 28 characterizes the evaluation unit 24 the receiving arrangement 22 a directional characteristic 30 on. The directional pattern 30 is distorted to sound waves 26 ' from a jammer 34 extinguish or at least dampen, so the influence of sound waves 26 ' in the output signal 28 is reduced. The distortion of the polar pattern 30 is in the circle 36 highlighted.

$$\lambda ={\left({\mathbf{C}}^H\mathbf{C}\right)}^{-1}{\mathbf{C}}^H{\mathbf{w}}_{\text{DSBF}}.$$

The distortion can in particular cause a zero in the directional characteristic in the predetermined direction. Starting from classic, ie non-adaptive, beamforming, the complex weights w _{DSBF of} the control _{vectors are} adjusted in the frequency domain. It is required that the optimized weights be selected so that the deviation of the directional characteristic on the one hand has a zero in the direction of the fault and on the other hand has a minimal deviation from the conventional directional characteristic. Optionally, this requirement can be extended by the additional condition that the derivation of the directional characteristic for the direction of the fault is also zero. The solution arises from $$\mathbf{w}={\mathbf{w}}_{\text{DSBF}}-\mathbf{C}\lambda .\text{in which}$$

$$\lambda ={\left({\mathbf{C}}^H\mathbf{C}\right)}^{-1}{\mathbf{C}}^H{\mathbf{w}}_{\text{DSBF}},$$

wird zusätzlich die Nullstelle der Ableitung gefordert, gilt $$\mathbf{C}=\left[{\mathbf{w}}_{\text{DSBF}}\left({\vartheta }_S\right),-\iota {\mathbf{r}}_x\circ {\mathbf{w}}_{\text{DSBF}}\left({\vartheta }_S\right)),-\iota {\mathbf{r}}_y\circ {\mathbf{w}}_{\text{DSBF}}\left({\vartheta }_S\right)),-\iota {\mathbf{r}}_z\circ {\mathbf{w}}_{\text{DSBF}}\left({\vartheta }_S\right)\right]$$

Here {} ^{H stands} for transposed and complex conjugate (or Hermitian). The choice of C depends on the secondary conditions, whether only the zero in the directional characteristic or also a zero for the derivation of the directional characteristic in the direction of the disturbance ϑ _{S is} desired. If only the zero of the directional characteristic is required, the following applies $$\mathbf{C}=\left[{\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)\right].$$

if the zero point of the derivation is additionally requested, applies $$\mathbf{C}=\left[{\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right).-\iota {\mathbf{r}}_x\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)).-\iota {\mathbf{r}}_y\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)).-\iota {\mathbf{r}}_z\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)\right]$$

und r_x, r_y bzw. r_z die x -, y - und z -Komponente der Hydrophonposition angibt. Das Symbol ◯ steht für das Hadamard-Produkt bzw. die punktweise Multiplikation.In which $\iota =\sqrt{\left(-1\right)}$

and r _x , r _y and r _z respectively indicate the x, y and z components of the hydrophone position. The symbol ◯ stands for the Hadamard product or the point-by-point multiplication.

In exemplary embodiments, equation (3) and equation (4) can also be extended by the mirror bearing, so that the beamformer not only suppresses the interference, but also the proportions of the mirror targets in a triplet array, if this is desired. In the case of a triplet array, the direction of incident sound signals from the secondary directions can also be determined by means of a measurement, for example by arranging three parallel line arrays. In triplet beamforming, the conventional control _vector w _{DSBF is converted} into an optimized control _vector w _Opt . The starting point for the suppression of the mirror bearing is the system of equations $$\begin{array}{l}{w}_{\text{opt}}^H{w}_{\text{DSBF}}=1\\ w_{\text{opt}}^H{w}_{\text{DSBF}.\text{mirror}}=\mathrm{0th}\end{array}$$

mit $$D=\left[w_{\text{DSBF}},w_{\text{DSBF},\text{Spiegel}}\right]$$

und $$g=\left(\begin{array}{c}1\\ 0\end{array}\right).$$

The solution comes from $$w_{\text{opt}}=D{\left(D^{H}D\right)}^{-1}G$$

With $$D=\left[w_{\text{DSBF}}.w_{\text{DSBF}.\text{mirror}}\right]$$

and $$G=\left(\begin{array}{c}1\\ 0\end{array}\right),$$

In a further exemplary embodiment, in addition to the direction finding, the direct sound of the interferer can also be suppressed. In this case, the system of equations (5) is expanded as follows: $$\begin{array}{l}{w}_{\text{opt}}^H{w}_{\text{DSBF}}=1\\ w_{\text{opt}}^H{w}_{\text{DSBF}.\text{mirror}}=0\\ w_{\text{opt}}^H{w}_{\text{DSBF}.\text{direct sound}}=\mathrm{0th}\end{array}$$

Equations (7) and (8) are expanded accordingly and the resulting weight vector then still results from the solution of equation 6.

By means of the distorted directional characteristic, the sound waves 26 ' of the troublemaker 34 can be hidden in the processed output signal or at least significantly attenuated. So these sound waves can 26 ' the sound waves 26 no longer overlay the underwater object and the detection of the underwater object in the processed output signal is simplified. The detection can also be carried out by an operator or by means of known algorithms for evaluating sonar signals. A mixed form, for example a preselection by an algorithm and an assessment of the preselection by the operator, is also possible.

Since the methods described above define the weights of the control vectors in the frequency domain, the directional characteristic can also be influenced selectively for individual frequency bands.

2 shows a location system 38 with the location signal receiver 20 , The location signal receiver 20 can in a tow antenna 40 be arranged. The troublemaker 34 is, for example, a watercraft that uses the tow antenna 40 pulls behind. The watercraft 34 can the sound waves 26 ' , in particular a location signal. A bi-static location scenario can thus be set up in that a non-actively transmitting underwater object reflects the location signal of the watercraft and the reflected location signal 26 from the location signal receiver 20 is recorded. However, the direct sound of the location signal hits 26 ' from the watercraft to the locating signal receiver in a short time after its transmission. Because of the volume of this location signal 26 ' can override the location signal receiver, although the signal is typically only received from a side lobe of the directional characteristic. By distorting the directional characteristic in the direction of the watercraft, however, the influence of the direct sound is minimized, so that there are also quieter noises from the location signal receiver 20 can be detected.

Although some aspects have been described in connection with a device, it goes without saying that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously, aspects that have been described in connection with or as a method step also represent a description of a corresponding block or details or features of a corresponding device.

Depending on the specific implementation requirements, exemplary embodiments of the invention can be implemented in hardware or in software. The implementation can be performed using a digital storage medium, such as a floppy disk, DVD, Blu-ray disc, CD, ROM, PROM, EPROM, EEPROM or FLASH memory, hard drive, or other magnetic or optical memory are carried out, on which electronically readable control signals are stored, which can cooperate with a programmable computer system or cooperate in such a way that the respective method is carried out. The digital storage medium can therefore be computer-readable. Some exemplary embodiments according to the invention thus comprise a data carrier which has electronically readable control signals which are able to interact with a programmable computer system in such a way that one of the methods described herein is carried out.

In general, exemplary embodiments of the present invention can be implemented as a computer program product with a program code, the program code being effective to carry out one of the methods when the computer program product runs on a computer. The program code can, for example, also be stored on a machine-readable carrier. Other embodiments include the computer program for performing one of the methods described herein, the computer program being stored on a machine readable medium.

In other words, an exemplary embodiment of the method according to the invention is thus a computer program which has a program code for performing one of the methods described here when the computer program runs on a computer. Another exemplary embodiment of the method according to the invention is thus a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for carrying out one of the methods described herein is recorded.

A further exemplary embodiment of the method according to the invention is thus a data stream or a sequence of signals which represents the computer program for performing one of the methods described herein. The data stream or the sequence of signals can, for example, be configured to be transferred via a data communication connection, for example via the Internet.

A further exemplary embodiment comprises a processing device, for example a computer or a programmable logic component, which is configured or adapted to carry out one of the methods described herein.

Another embodiment includes a computer on which the computer program for performing one of the methods described herein is installed.

In some embodiments, a programmable logic device (e.g., a field programmable gate array, an FPGA) can be used to perform some or all of the functionality of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. In general, in some embodiments, the methods are performed by any hardware device. This can be a universally usable hardware such as a computer processor (CPU) or hardware specific to the method, such as an ASIC.

The above-described embodiments are merely illustrative of the principles of the present invention. It is to be understood that modifications and variations in the arrangements and details described herein will be apparent to those skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented based on the description and explanation of the exemplary embodiments herein.

LIST OF REFERENCE NUMBERS

20

Locating signal receiver

21

Underwater object

22

receiving arrangement

22a, b, c

receiver unit

24

evaluation

26, 26 '

sound waves

28

output

30

directivity

32

predetermined direction

34

disturbers

36

distortion

38

tracking system

40

trailing antenna

Claims (14)

Location signal receiver (20) for the detection of an underwater object with the following features: a receiving arrangement (22) comprising a plurality of receiving units (22a, 22b, 22c), the receiving units (22a, 22b, 22c) being designed to receive sound waves (26) and to generate an output signal (28); an evaluation unit (24), which is designed to impart a directional characteristic (30) to the receiving arrangement (22) by processing the output signal (28), the directional characteristic (30) for sound waves (26) being distorted from a predetermined direction (32), so that the receiving arrangement (22) has a reduced sensitivity in the predetermined direction (32); the evaluation unit (24) being designed to evaluate the processed output signal (28) and to detect the underwater object (21) in the evaluated output signal (28). Location signal receiver (20) according to Claim 1 , wherein the evaluation unit (24) has one or a plurality of control vectors in order to impress the directional characteristic (30) on the receiving arrangement (22). Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to distort the directional characteristic (30) only for one frequency band. Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to determine the predetermined direction (32) from the received or processed sound waves (26) and for subsequent sound waves (26) the directional characteristic (30) distort. Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to determine a frequency band from the received or processed sound waves (26), in which interfering noises occur and for subsequent sound waves (26) to distort the directional characteristic (30) for the determined frequency band in order to suppress the interfering noises. Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to transform the output signal (28) for processing into the frequency range and by adapting a phase and / or an amplitude of a signal of a receiving unit in the output signal (28 ) to produce the directional characteristic (30). Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to set a zero in the predetermined direction (32) by distorting the directional characteristic (30). _{Location signal receiver} (20) according to one of claims 2 to 7, wherein the evaluation unit (24) is designed to adapt the control _vector such that weights w _{DSBF of} a delay-and-sum beamforming algorithm are replaced by weights w: $$w=w_{\text{DSBF}}-C\lambda .$$

With $$\lambda ={\left(C^{H}C\right)}^{-1}{C}^H{w}_{\text{DSBF}},$$

and $$C=\left[w_{\text{DSBF}}\left({\theta }_S\right)\right]$$

where ϑ _{s describes} the predetermined direction (32). Location signal receiver (20) according to one of the preceding claims, wherein the evaluation unit (24) is designed to set a zero in the predetermined direction (32) by distorting the directional characteristic (30) and to distort the directional characteristic (30) such that the derivative of the directional characteristic (30) in the predetermined direction (32) is zero. Location signal receiver (20) according to one of Claims 2 to 9, wherein the evaluation unit (24) is designed to adapt the control _vector such that weights w _{DSBF of} a delay-and-sum beamforming algorithm are replaced by weights w: $$w=w_{\text{DSBF}}-C\lambda .$$

With $$\lambda ={\left(C^{H}C\right)}^{-1}{C}^H{w}_{\text{DSBF}},$$

and $$\mathbf{C}=\left[{\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right).-\iota {\mathbf{r}}_x\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)).-\iota {\mathbf{r}}_y\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)).-\iota {\mathbf{r}}_z\circ {\mathbf{w}}_{\text{DSBF}}\left({\theta }_S\right)\right]$$

where ϑ _{s describes} the predetermined direction (32) and where $\iota =\sqrt{\left(-1\right)}$

and r _x , r _y and r _z indicate the x, y and z components of the receiving unit. Location system (38) for the detection of an underwater object with the following features: a location signal transmitter, which is designed to transmit a location signal; a location signal receiver (20) according to any one of claims 1 to 10; wherein the evaluation unit (24) is designed to distort the directional characteristic (30) for the direction (32) in which the locating signal transmitter is arranged. Location system (38) according to Claim 11 wherein the location signal receiver (20) moves on a predefined route; wherein the evaluation unit (24) is designed to adapt the directional characteristic (30) in accordance with the predefined route, so that the reduced sensitivity is continuously aligned in the direction (32) of the location signal receiver. Method for detecting an underwater object with the following steps: Receiving sound waves (26) with a plurality of receiving units (22a, 22b, 22c) forming a receiving arrangement (22) and generating an output signal (28) by the receiving units (22a, 22b, 22c); Impressing a directional characteristic (30) on the output signal (28), the directional characteristic (30) for sound waves (26) being distorted from a predetermined direction (32), so that the receiving arrangement (22) in the predetermined direction (32) reduces one Has sensitivity; Evaluation of the processed output signal (28) in order to detect the underwater object (21) in the evaluated output signal (28). Computer program with a program code for performing the method according to any one of claims 13, when the computer program runs on a computer.

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