Characterisation of each transducer array of an acoustic transmission and reception antenna

Abstract

The present invention relates to a method (30) for determining the sensitivity in terms of reception voltage and transmission current of each transducer array belonging to a plurality of reciprocal transducer arrays of an acoustic transmission and reception antenna, comprising the following steps, - until each array is used as a transmission array: - transmission (32) of an acoustic signal by one of the arrays; - simultaneous near-field acquisition (34) of the current and voltage of said transmission array and of the reception voltage of each distinct array of said plurality; then: - obtaining (42) of a reciprocal coupling matrix of said plurality of transducer arrays; - determination (44), based on the matrix, of the sensitivity in terms of reception voltage and transmission current of each array.

Description

[0001] TITLE: Characterization of each transducer group(s) of an acoustic transmitting and receiving antenna

[0002] The present invention relates to a method for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, a reciprocal transducer being defined as having a sensitivity ratio, equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer.

[0003] The present invention also relates to a system for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, a reciprocal transducer being defined as having a sensitivity ratio, equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer.

[0004] The invention lies in the field of evaluating the operating state of each of the transducers of an acoustic transmitting and receiving antenna, and aims, for example, to be exploited preferentially for maintenance in operational condition (MCO) once said antenna has been installed on its carrier, such as, for example, a sonar antenna installed on a boat.

[0005] Regularly measuring the transmission and reception characteristics of the transducers in such an antenna typically requires disassembling the antenna, measuring each transducer individually, and then reassembling it. Therefore, it is clear that only electrical characteristics, such as impedance, can be measured regularly throughout an antenna's lifespan.

[0006] However, transmit and receive characteristics are necessary, such as transmit and receive sensitivity, to understand variations over time or the dispersion of these sensitivities across all the transducers that make up the antenna, and thus determine whether or not maintenance is required. The article "Underwater acoustics - Hydrophones - Calibration of hydrophones - Part 1: Procedures for free-field calibration of hydrophones" IEC 60565-1 deals generally with underwater acoustics, hydrophones, hydrophone calibration, and in particular, free-field hydrophone calibration procedures.

[0007] The article "Determination of an ultrasonic transducer's sensitivity and impedance in a pluse-echo setup" by Ana L. LOPEZ-SANCHEZ et al. focuses on the determination of the sensitivity and impedance of an ultrasonic transducer in a pulsed echo setup.

[0008] A current solution is generally based on a far-field measurement. However, such a measurement provides an average response across the antenna transducers, which does not allow for targeted maintenance to identify and maintain only the faulty transducer(s).

[0009] The aim of the invention is therefore to propose a solution for monitoring the operation of the transducers of an acoustic transmitting and receiving antenna, allowing for a more precise identification of at least some of the transducers for which maintenance is necessary, while avoiding individual dismantling of transducers or the use of acoustic means external to the antenna itself.

[0010] To this end, the invention relates to a method for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, a reciprocal transducer being defined as having a sensitivity ratio equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer, said method comprising the following steps:

[0011] - emission of an acoustic signal by one of said transducer group(s) of said plurality used as emission transducer group(s);

[0012] - simultaneous near-field acquisition of the current and voltage of said transmitting transducer group(s) and of the receiving voltage of each transducer group(s) of said plurality distinct from said transmitting transducer group(s); said transmission and acquisition steps being repeated until each transducer group(s) of said plurality is used as a transmitting transducer group(s);

[0013] - obtaining a reciprocal coupling matrix of size NxN of said plurality of transducer groups of said antenna, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s), an impedance equal to the ratio of its receiving voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current;

[0014] - from said impedances of said reciprocal coupling matrix, determination of the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

[0015] Thus, the present invention aims to take advantage of an acquisition of signals obtained by at least one acoustic coupling measurement, which makes it possible to highlight the individual operation of each group of transducer(s), unlike a far-field acoustic measurement which gives an averaged response over the antenna transducers.

[0016] Near-field acoustic coupling is advantageous for verifying the emission and reception response of reciprocal transducers, monitoring their characteristics over time, and ensuring proper transducer wiring.

[0017] The near field is defined as the space in which all the antenna transducers are located.

[0018] According to other advantageous aspects of the invention, the method for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal groups of transducer(s) of an acoustic transmitting and receiving antenna, with N>3, comprises one or more of the following features, taken individually or in all technically possible combinations:

[0019] - said acoustic signal emitted is of a type belonging to the group comprising at least:

[0020] - a pulse at a fixed frequency;

[0021] - a frequency-modulated pulse;

[0022] - a noise;

[0023] - said noise is periodic or aperiodic.

[0024] - said determination step comprises a plurality of iterations until the voltage sensitivity in receive and the current sensitivity in transmit of each transducer group(s) of said plurality are determined, and considers at each iteration at least one triplet of transducer groups of said plurality of N reciprocal transducer groups distinct from one iteration to the next, said triplet being composed of a transducer group(s) in transmit state of index n, a transducer group(s) in receive state of index m and a transducer group(s) of index p distinct from m and n, whose value J P is a predetermined function

[0025] Sh p of its report of sensitivities, called the term of reciprocity, such as: J p = with Sh p its Sensitivity in voltage during reception and Si pIts current sensitivity in transmit and receive modes is used with said triplet to determine the voltage sensitivity in receive mode of the transducer group(s) in receive mode with index m and the current sensitivity in transmit mode of the transducer group(s) in transmit mode with index n, such that: u m

[0026] 7 minutes = - days >

[0027] 'n with: z mn the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current i n said group of transducer(s) in transmitting state of index n; z mp the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current l p said reciprocal transducer group(s) of index p; z pn the impedance equal to the ratio of the received voltage u pof the reciprocal transducer group(s) of index p on the current i n said group of transducer(s) in emission state of index n;

[0028] Sh m the voltage sensitivity in reception of the transducer group(s) in reception state of index m;

[0029] H pn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index p;

[0030] H mn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index m;

[0031] H mp the predetermined near-field propagation function from the group of transducer(s) with index p to the distinct group of transducer(s) with index m;

[0032] If nthe current sensitivity at emission of the group of transducer(s) with index n;

[0033] - the voltage sensitivity in reception of the group of transducer(s) in the receiving state of index m, is obtained by arithmetic or geometric mean by considering a plurality of distinct triplets to which the group of transducer(s) in the receiving state of index m belongs, and from one triplet to another, at least one different group of transducer(s) between the reciprocal group of transducer(s) and the group of transducer(s) in the transmitting state;

[0034] - said average is obtained by using a predetermined weighting of the voltage sensitivities in reception of the group of transducer(s) in reception state of index m associated with each triplet;

[0035] - said determination step is implemented by solving a system of equations in matrix form such as:

[0036] [Z] = [Sft] . [H] . [Si]

[0037] [Sh] = [J] . [Si] with:

[0038] [Z] said reciprocal coupling matrix;

[0039] [Sh] the diagonal matrix of voltage sensitivities at the reception of the transducer group(s) of said plurality;

[0040] [H] the predetermined matrix of near-field propagation functions between the transducer group(s) of said plurality;

[0041] [If] the diagonal matrix of current sensitivities at emission of the transducer group(s) of said plurality;

[0042] [ / ] the predetermined diagonal matrix of reciprocity functions for each group of transducer(s).

[0043] The invention also relates to a system for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, a reciprocal transducer being defined as having a sensitivity ratio equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer, said system comprising said antenna and the following modules:

[0044] - an acoustic signal emission module configured to initiate the emission of an acoustic signal by one of said transducer group(s) of said plurality used as emission transducer group(s), said emission module being able to be connected / disconnected from each transducer group, at each iteration, until each transducer group(s) of said plurality is used as emission transducer group(s);

[0045] - an acquisition module configured to simultaneously acquire the current and voltage of said transmitting transducer group(s) and the receiving voltage of each transducer group(s) of said distinct plurality of said transmitting transducer group(s), said acquisition module being able to be connected / disconnected from each distinct transducer group of said transmitting transducer group(s), until, for each transmitting transducer group(s), each distinct transducer group(s) of said distinct plurality of said transmitting transducer group(s) is used as a receiving transducer group(s);

[0046] - a generation module configured to obtain a reciprocal coupling matrix of size NxN of said plurality of transducer groups of said antenna, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s), an impedance equal to the ratio of its receiving voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current;

[0047] - a determination module configured to determine from said impedances of said reciprocal coupling matrix, the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

[0048] According to other advantageous aspects of the invention, the system for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal groups of transducer(s) of an acoustic transmitting and receiving antenna, with N>3, comprises one or more of the following features, taken individually or in all technically possible combinations:

[0049] - each group of transducer(s) comprises a single transducer, or corresponds to a column of transducers or a line of transducers, when the transducers of said antenna are arranged in a plurality of lines and columns;

[0050] - each transducer is of a type belonging to the group comprising at least:

[0051] - piezoelectric acoustic transducers;

[0052] - electrodynamic acoustic transducers;

[0053] - assemblies of electromagnetic antennas. The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0054] [Fig. 1] Figure 1 is a schematic representation of a system for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, according to the present invention.

[0055] [Fig 2] Figure 2 is a flowchart of the main steps of a method for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) group(s) of an acoustic transmitting and receiving antenna, with N>3, according to the present invention.

[0056] Figure 1 illustrates an embodiment of a system 10 for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna 12, with N>3, according to the present invention.

[0057] As previously stated, a reciprocal transducer is defined as a transducer with a sensitivity ratio equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer.

[0058] Each transducer is of a type belonging to the group comprising at least:

[0059] - piezoelectric acoustic transducers;

[0060] - electrodynamic acoustic transducers;

[0061] - sets of electromagnetic antennas.

[0062] According to the embodiment illustrated in Figure 1, the determination system 10 includes said antenna 12.

[0063] In the example shown in Figure 1, antenna 12 comprises, for example, six transducers TT, T2, T3, T4, T5, T6, arranged in two lines, the upper line comprising the three transducers T2, and T3, the lower row comprising the three transducers T4, T5, and T6, which also amounts to three columns, the first column comprising, for example, the two transducers T4, the second column comprising, for example, the two transducers T2 and T5, the third column comprising, for example, the two transducers T3 and T6. According to the present invention, a grouping of transducer(s) comprises at least one transducer.

[0064] Thus, in a first example, each group of transducers comprises a single transducer. Therefore, according to Figure 1, antenna 12 then comprises six (N=6) groups corresponding to the six individual transducers. T2, T3, T4, T5, T6.

[0065] According to a second example, each grouping of transducer(s) is a column of transducers when, as illustrated in Figure 1, the transducers of said antenna 12 are arranged in a plurality of rows and columns. Thus, according to Figure 1, antenna 12 then comprises three (N=3) groups of transducers, namely the first column comprising the two transducers and T4, the second column comprising the two transducers T2 and T5, the third column comprising the two transducers T3 and T6.

[0066] According to a third example, each grouping of transducer(s) is a transducer line when, as illustrated in Figure 1, the transducers of said antenna 12 are arranged in a plurality of rows and columns. Thus, according to Figure 1, antenna 12 comprises two (N=2) transducer groups, namely the upper row comprising the three transducers T2, and T3, the lower line comprising the three transducers T4, T5, and T6.

[0067] The following describes the implementation of the invention according to the first example where each group of transducer(s) comprises a single transducer.

[0068] According to the example in Figure 1, the determination system 10 according to the present invention further comprises an acoustic signal emission module 14 configured to initiate the emission of an acoustic signal by one of said transducer group(s) of said plurality used as an emission transducer group(s).

[0069] In Figure 1, the transmission module 14 is initially connected to the transducer group comprising the single transducer T r

[0070] The said transmission module 14 is suitable for being connected / disconnected from each transducer group, according to the example in Figure 1, each group corresponding to one of the individual transducers, at each iteration, until each transducer group (i.e. according to this first example until each individual transducer) of said plurality is used as the transmission transducer group.

[0071] In other words, the transmission module 14 is designed to be connected to the transducer Ti, and then disconnected from the transducer. to be connected to another of the transducers T2, T3, T4, T5, T6, for example transducer T2, or transducer T3, and so on until each individual transducer of said plurality is used as a transmitting transducer, in a predetermined or arbitrary order. As illustrated in Figure 1, the transmitting module 14 includes, in particular, a signal generator G 14^ whose output is connected to a signal amplifier A 142 whose output corresponds to the output of the transmitting module 14 supplied as the input to each transducer.

[0072] As an optional addition, the emitted acoustic signal is of a type belonging to the group comprising at least:

[0073] - a fixed frequency pulse (CW, from the English Continuous Wave)',

[0074] - a frequency modulated pulse (FM from the English Frequency Modulation);

[0075] - a noise.

[0076] As an optional addition, the noise is either periodic or aperiodic.

[0077] According to the example in Figure 1, the determination system 10 according to the present invention further comprises an acquisition module 16 configured to simultaneously acquire the current and voltage of said group of emitting transducer(s), the transducer as in the example of Figure 1, and the receiving voltage of each transducer group(s) of said distinct plurality of said transmitting transducer group(s) simultaneously or iteratively (i.e., module 16 can iteratively acquire the signals from a single distinct transducer group(s) of said transmitting transducer group(s), or from several distinct transducer groups of said transmitting transducer group(s) simultaneously, so that the signals from all the receiving transducers are acquired), said acquisition module 16 being able to be connected / disconnected from each distinct transducer group of said transmitting transducer group(s), until, for each transmitting transducer group(s), each distinct transducer group(s) of said distinct plurality of said transmitting transducer group(s) is used as a receiving transducer group(s).

[0078] In Figure 1, the acquisition module 16 is shown, as an example, connected to the transducer T5, even though it is the transducer that emits. Not shown, when the transducer The acquisition module 16 is designed to be connected / disconnected successively or simultaneously from each transducer T2, T3, T4, T5, T6 until each group of transducer(s) (i.e., each individual transducer) of said plurality is used as a group of receiving transducer(s), when the transducer emits.

[0079] Similarly, when the transducer ^ transmits, the acquisition module 16 is suitable to be connected / disconnected successively or simultaneously from each transducer TT, T3, T4, T5, T6 until each group of transducer(s) (i.e. here each individual transducer) of said plurality is used as a group of receiving transducer(s), when the transducer T2 transmits, and so on until each group of transducer(s) of said plurality is used as a group of transmitting transducer(s).

[0080] As illustrated by Figure 1, the acquisition module 16 includes a 16T Acq system for acquiring received signals optionally preceded by a PA 162 preamplifier (i.e., whose output feeds said 16- acquisition system).

[0081] The output of said acquisition module 16 is transmitted into the input of a gain module 18 configured to obtain a reciprocal coupling matrix of said plurality of transducer groups of said antenna, of size NxN, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s) (current during said iteration), an impedance equal to the ratio of its receive voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current.

[0082] Then the output of said obtaining module 18 is transmitted into the input of a determination module 20 configured to determine from said impedances of said reciprocal coupling matrix, the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

[0083] In the example in Figure 1, the acquisition module 18 and the determination module 20 are optionally integrated within an electronic device 22 for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) groups of an acoustic transmitting and receiving antenna.

[0084] Optionally, said electronic determination device 22 includes an information processing unit formed for example of a memory 26 and a processor 28 associated with the memory 26.

[0085] In the example shown in Figure 1, the acquisition module 18 and the determination module 20 are each implemented as a software program, or a software component, executable by the processor. The memory 26 of the electronic determination device 22 is then capable of storing both an acquisition program and a determination program 20. The processor 28 is then capable of executing either the acquisition program or the determination program.

[0086] In an alternative not shown, the acquisition module and the determination module are each implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array), or an integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0087] When the electronic determination device 22 is implemented as one or more software programs, that is, as a computer program, also called a computer program product, it is also capable of being stored on a computer-readable medium (not shown). A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. Examples of such a readable medium include an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (e.g., FLASH or NVRAM), or a magnetic card. A computer program comprising software instructions is then stored on the readable medium.

[0088] An example of an embodiment of the operation of the system 10 for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducers belonging to a plurality of N reciprocal groups of a transmitting and receiving acoustic antenna 12 is described in relation to Figure 2. More specifically, the method 30 for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducers belonging to a plurality of N reciprocal groups of a transmitting and receiving acoustic antenna comprises, firstly, a first step 32 of transmitting an acoustic signal by one of said groups of transducers of said plurality used as the transmitting transducer group(s).

[0089] As an optional addition, the emitted acoustic signal is of a type belonging to the group comprising at least:

[0090] - a pulse at a fixed frequency;

[0091] - a frequency-modulated pulse;

[0092] - a noise.

[0093] Then the process 30 includes a step 34 of simultaneous near-field acquisition of the current and voltage of said group of transmitting transducer(s) and of the receiving voltage of each group of transducer(s) of said distinct plurality of said group of transmitting transducer(s).

[0094] More precisely, for an iteration indexed i associated with the transmitting transducer group(s), the acquisition is repeated until, for each transmitting transducer group(s), each transducer group(s) of said plurality distinct from said transmitting transducer group(s) is used as a receiving transducer group(s). In step 36, it is tested whether i=N, which amounts to verifying that each transducer group(s) of said plurality is used as a transmitting transducer group(s).

[0095] If not, according to arrow 38, the emission and acquisition steps 32 and 34 are repeated until each group of transducer(s) of said plurality is used as the emission transducer(s) group.

[0096] In other words, during each iteration of index i with 1 <i<N, le principe est d’émettre, lorsque que l’on considère notamment le cas où un groupe de transducteur(s) comprend uniquement un seul transducteur, sur un transducteur et d’acquérir le signal sur tous les autres transducteurs de l’antenne.

[0097] In the affirmative (i.e. if i=N) according to arrow 40, the process then includes a step 42 of obtaining OBT of a reciprocal coupling matrix [Z] of said plurality of transducer groups of said antenna, of size NxN, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s), an impedance equal to the ratio of its receiving voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current.

[0098] More specifically, each Z term kj is the measurement of the voltage U k reception divided by the transmission current lj regardless of the transducers k other than the transmission transducer of index j, with 1 <j<N et 1<k j<N (i.e. Z kjis equal to llj divided by lj), and each diagonal term Zjj of the matrix [Z] is the measure of the impedance of transducer j at emission (i.e. Zjj is equal to llj divided by lj).

[0099] Finally, from the said impedances of the said reciprocal coupling matrix, the process 30 includes a step 44 of determining D_l the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of the said plurality.

[0100] The results of step 44, which determines the receive voltage sensitivity and transmit current sensitivity of each transducer group in the array, are recorded over time to track variations or dispersion of these sensitivities across all transducers constituting the antenna. Based on these findings, a targeted maintenance operation is triggered, focusing solely on transducers identified as defective due to time variations exceeding a predetermined threshold or sensitivity dispersion exceeding a predetermined threshold. Several variations, illustrated in Figure 2, can be used to determine the receive voltage sensitivity and transmit current sensitivity of each transducer group in the array.

[0101] According to a first variant 46, said determination step 44 comprises a plurality of iterations (not shown for simplicity) until the voltage sensitivity in receive and the current sensitivity in transmit of each transducer group(s) of said plurality are determined, and considers at each iteration at least one triplet of transducer groups of said plurality of N reciprocal transducer groups distinct from one iteration to the next, said triplet being composed of a transducer group(s) in transmit state of index n, a transducer group(s) in receive state of index m and a transducer group(s) of index p distinct from m and n, whose value J P is a predetermined function of its ratio of sensitivities, called the term reciprocity, such as: J p = with Sh p his sensitivity in voltage in reception and Si pIts current sensitivity in transmit and receive modes (this predetermined function being inherently variable with frequency and acoustic conditions) is used with said triplet to determine the voltage sensitivity in receive mode of the transducer group(s) in receive mode with index m and the current sensitivity in transmit mode of the transducer group(s) in transmit mode with index n, such that: with: z mn the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current l n said group of transducer(s) in transmitting state of index n; z mp the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current i p said reciprocal transducer group(s) of index p; z pn the impedance equal to the ratio of the received voltage up of the reciprocal transducer group(s) of index p on the current l n said group of transducer(s) in emission state of index n;

[0102] Sh m the voltage sensitivity in receive mode of the transducer group(s) in receive mode with index m; H pn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index p;

[0103] H mn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index m;

[0104] H mp the predetermined near-field propagation function from the group of transducer(s) with index p to the distinct group of transducer(s) with index m;

[0105] If nthe current sensitivity at the emission of the group of transducer(s) of index n, the J functions p , H pn , H mn , H mp having been previously determined and being used as inputs to said process.

[0106] For example, in relation to Figure 1, the grouping of transducer(s) in emission state with index n includes only the transducer the group of transducer(s) in receiving state of index m includes only the transducer T5, and the reciprocal group of transducer(s) of index p includes only the transducer T3.

[0107] According to a first option 48 of this first variant 46, only one triplet S_T per iteration is considered.

[0108] According to a second option 50 of this first variant 46, the voltage sensitivity in reception of the group of transducer(s) in the receiving state of index m, is obtained by a substep 52 of calculation of an arithmetic or geometric mean M by considering, according to this second option 50, a plurality P_T of distinct triplets to which the group of transducer(s) in the receiving state of index m belongs, and from one triplet to another, at least one different group of transducer(s) between the reciprocal group of transducer(s) and the group of transducer(s) in the transmitting state.

[0109] As an optional complement to this second option 50, the process 30 said average is obtained by using a predetermined weighting substep 54 of the voltage sensitivities in reception of the group of transducer(s) in reception state of index m associated with each triplet.

[0110] According to a second variant 56, said determination step 44 is implemented by solving a system of equations in matrix form such as:

[0111] [Z] = [Sft] . [H] . [Si]

[0112] [Sh] = [J] . [Si] with:

[0113] [Z] said reciprocal coupling matrix;

[0114] [Sh] the diagonal matrix of voltage sensitivities at reception of the transducer group(s) of said plurality; [H] the predetermined matrix of near-field propagation functions between the transducer group(s) of said plurality;

[0115] [If] the diagonal matrix of current sensitivities at emission of the transducer group(s) of said plurality;

[0116] [J] the predetermined diagonal matrix of reciprocity functions for each group of transducer(s).

[0117] A person skilled in the art will understand that the invention is not limited to the embodiments described, nor to the particular examples of the description, the embodiments and variants mentioned above being capable of being combined with each other to generate new embodiments of the invention.

[0118] A person skilled in the art will also understand that the voltage sensitivity at emission and the power sensitivity at emission of a group of transducer(s) is obtained by calculation using the current sensitivity at emission and the impedance of said group of transducer(s).

[0119] The present invention, based on a measurement (i.e. an acquisition) by reciprocal coupling, thus makes it possible to measure the sensitivity in transmission and reception of each transducer or group of transducers (in line or in column for example) of an acoustic transmitting and receiving antenna, uses the transducers of the antenna to measure themselves, and is therefore simplified by the fact that it does not require acoustic means external to the antenna itself.

[0120] It is therefore advantageously feasible to carry out it at the dock when said antenna is in particular a sonar antenna installed on a boat.

[0121] The reciprocal coupling measurement method also brings other advantages, namely the highlighting of the individual operation of each transducer, the possibility of checking the transmission and reception response and of monitoring these characteristics over time, as well as the possibility of verifying the correct wiring of the transducers.

Claims

DEMANDS 1. A method (30) for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal transducer(s) of an acoustic transmitting and receiving antenna, with N>3, a reciprocal transducer being defined as having a sensitivity ratio equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer, said method comprising the following steps: - emission (32) of an acoustic signal by one of said transducer group(s) of said plurality used as emission transducer group(s); - simultaneous near-field acquisition (34) of the current and voltage of said transmitting transducer group(s) and of the receiving voltage of each transducer group(s) of said plurality distinct from said transmitting transducer group(s); said transmitting and acquiring steps being repeated until each transducer group(s) of said plurality is used as a transmitting transducer group(s); - obtaining (42) a reciprocal coupling matrix of size NxN of said plurality of transducer groups of said antenna, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s), an impedance equal to the ratio of its receiving voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current; - from said impedances of said reciprocal coupling matrix, determination (44) of the voltage sensitivity in reception and of the current sensitivity in transmission of each group of transducer(s) of said plurality.

2. A method according to claim 1, wherein said emitted acoustic signal is of a type belonging to the group comprising at least: - a pulse at a fixed frequency; - a frequency-modulated pulse; - a noise.

3. Method according to claim 2 wherein said noise is periodic or aperiodic.

4. A method according to any one of the preceding claims, wherein said determination step comprises a plurality of iterations until the receive voltage sensitivity and transmit current sensitivity of each transducer group(s) of said plurality are determined, and considers at each iteration at least one triplet of transducer groups of said plurality of N reciprocal transducer groups distinct from one iteration to the next, said triplet being composed of a transmit transducer group(s) of index n, a receive transducer group(s) of index m, and a transducer group(s) of index p distinct from m and n, the value of which J P is a predetermined function Sh p of its report of sensitivities, called the term of reciprocity, such as: J p = with Sh p its sensitivity to voltage in reception and Si pIts current sensitivity in transmit and receive modes is used with said triplet to determine the voltage sensitivity in receive mode of the transducer group(s) in receive mode with index m and the current sensitivity in transmit mode of the transducer group(s) in transmit mode with index n, such that: with: z mn the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current l n said group of transducer(s) in transmitting state of index n; z mp the impedance equal to the ratio of the voltage u m reception of the transducer group(s) in reception state of index m on the current i p said reciprocal transducer group(s) of index p; z pn the impedance equal to the ratio of the received voltage u p of the reciprocal transducer group(s) of index p on the current in said group of transducer(s) in emission state of index n; Sh m the voltage sensitivity in reception of the transducer group(s) in reception state of index m; H pn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index p; H mn the predetermined near-field propagation function from the group of transducer(s) with index n to the distinct group of transducer(s) with index m; H mp the predetermined near-field propagation function from the group of transducer(s) with index p to the distinct group of transducer(s) with index m; If n the current sensitivity at emission of the group of transducer(s) with index n.

5. Method according to claim 4, wherein the voltage sensitivity in receive of the group of transducer(s) in receive state of index m, is obtained by arithmetic or geometric mean by considering a plurality of distinct triplets to which the group of transducer(s) in receive state of index m belongs, and from one triplet to another, at least one different group of transducer(s) between the reciprocal group of transducer(s) and the group of transducer(s) in transmit state.

6. Method according to claim 5, wherein said average is obtained by using a predetermined weighting of the voltage sensitivities in receive of the group of transducer(s) in receive state of index m associated with each triplet.

7. A method according to any one of the preceding claims 1 to 3, wherein said determination step is implemented by solving a system of equations in matrix form such that: [Z] = [Sft] . [H] . [Si] [Sh] = [J] . [Si] with: [Z] said reciprocal coupling matrix; [Sh] the diagonal matrix of voltage sensitivities at the reception of the transducer group(s) of said plurality; [H] the predetermined matrix of near-field propagation functions between the transducer group(s) of said plurality; [If] the diagonal matrix of current sensitivities at emission of the transducer group(s) of said plurality; [ / ] the predetermined diagonal matrix of reciprocity functions for each group of transducer(s).

8. System (10) for determining the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) belonging to a plurality of N reciprocal groups of a transmitting and receiving acoustic antenna (12), with N>3, a reciprocal transducer being defined as having a sensitivity ratio equal to its voltage sensitivity in reception to its current sensitivity in transmission, said ratio being independent of the electromechanical characteristics of said transducer, a group of transducer(s) comprising at least one transducer, said system comprising said antenna (12) and the following modules: - an acoustic signal emission module (14) configured to initiate the emission of an acoustic signal by one of said transducer group(s) of said plurality used as an emission transducer group(s), said emission module being able to be connected / disconnected from each transducer group, at each iteration, until each transducer group(s) of said plurality is used as an emission transducer group(s); - an acquisition module (16) configured to simultaneously acquire the current and voltage of said transmitting transducer group(s) and the receiving voltage of each transducer group(s) of said distinct plurality of said transmitting transducer group(s), said acquisition module being suitable for being connected / disconnected from each distinct transducer group of said transmitting transducer group(s), until, for each transmitting transducer group(s), each distinct transducer group(s) of said distinct plurality of said transmitting transducer group(s) is used as a receiving transducer group(s); - a acquisition module (18) configured to obtain a reciprocal coupling matrix of size NxN of said plurality of transducer groups of said antenna, said reciprocal coupling matrix associating, for each iteration, to each transducer group(s) of said plurality distinct from said transmitting transducer group(s), an impedance equal to the ratio of its receive voltage to the current of said transmitting transducer group(s), and associating to said transmitting transducer group(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current; - a determination module (20) configured to determine from said impedances of said reciprocal coupling matrix, the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

9. System according to claim 8 in which each group of transducer(s) comprises a single transducer, or corresponds to a column of transducers or a line of transducers, when the transducers of said antenna are arranged in a plurality of rows and columns.

10. System according to claim 8 or 9 wherein each transducer is of a type belonging to the group comprising at least: - piezoelectric acoustic transducers; - electrodynamic acoustic transducers.

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