Characterization of each transducer group(s) of an acoustic transmitting and receiving antenna

Abstract

Characterization of each transducer group(s) of a transmitting and receiving acoustic antenna. The present invention relates to a method (30) for determining the voltage sensitivity in reception and current sensitivity in transmission of each transducer group(s) belonging to a plurality of reciprocal transducer groups of a transmitting and receiving acoustic antenna, comprising the following steps, - until each group is used as a transmitting group: - transmission (32) of an acoustic signal by one of said groups; - simultaneous near-field acquisition (34) of the current and voltage of said transmitting group and the receive voltage of each distinct group of said plurality; then: - obtaining (42) a reciprocal coupling matrix of said plurality of transducer groups;- from said matrix, determination (44) of the voltage sensitivity in reception and current sensitivity in transmission of each group. Figure for the abbreviation: Figure 2;

Description

Title of the invention: Characterization of each transducer group(s) of an acoustic transmitting and receiving antenna

[0001] The present invention relates to a method for determining the voltage sensitivity in reception and the current sensitivity in transmission of each transducer group(s) belonging to a plurality of N reciprocal transducer groups(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 transducer group(s) comprising at least one transducer.

[0002] 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 groups of a transmitting and receiving acoustic 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 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.

[0004] Regularly measuring the transmission and reception characteristics of the transducers constituting such an antenna typically requires disassembling the antenna, measuring the transducers one by one, and reassembling the antenna. It is therefore clear that only electrical characteristics, such as impedance, can be measured regularly during the lifetime of an antenna.

[0005] However, the transmission and reception characteristics are necessary, such as the transmission and reception sensitivity, to know the variations over time or the dispersion of these sensitivities over all the transducers constituting the antenna, and accordingly trigger or not a maintenance operation.

[0006] A current solution is generally based on a far-field measurement. However, such a measurement gives a response averaged over the transducers of the antenna, which does not allow for targeted maintenance to be carried out specifically to identify and maintain only the defective transducer(s).

[0007] The aim of the invention is then to propose a solution for monitoring the operation of the transducers of an acoustic transmitting and receiving antenna allowing a more precise identification of at least some of the transducers for which maintenance is necessary, and this by avoiding individual dismantling of transducers or by avoiding the use of acoustic means external to the antenna itself.

[0008] 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 groups of a transmitting and receiving acoustic 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,

[0009] said process comprising the following steps:

[0010] - emission of an acoustic signal by one of said transducer group(s) said plurality used as a grouping of emission transducer(s);

[0011] - simultaneous near-field acquisition of the current and voltage of said grouping of transmitting transducer(s) and the receiving voltage of each grouping of transducer(s) of said plurality distinct from said grouping of transmitting transducer(s);

[0012] said emission and acquisition steps being repeated until each group of transducer(s) of said plurality is used as a group of emission transducer(s);

[0013] - obtaining a reciprocal coupling matrix of said plurality of groups of transducers of said antenna of size NxN, said reciprocal coupling matrix associating, for each iteration, to each group of transducer(s) of said plurality distinct from said group of transmitting transducer(s), an impedance equal to the ratio of its receiving voltage to the current of said group of transmitting transducer(s), and associating to said group of transmitting transducer(s) its impedance measurement at the transmission 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 advantageously allows verification of the emission and reception response of reciprocal transducers, the monitoring of their characteristics over time, as well as the correct wiring of the transducers.

[0017] The near field being 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 emitted acoustic signal is of a type belonging to the group comprising less :

[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 this that the voltage sensitivity in reception and the current sensitivity in transmission 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 in transmission state of index n, a transducer group in reception state of index m, and a transducer group of index p distinct from m and n, whose value JP is a predetermined function of its sensitivity ratio, called the reciprocity term, such that: , with Shp its voltage sensitivity in reception and Sip Sip Its 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:

[0025] 7 y _£«.7 _ ü ; ^mn- [n -, ^mp— jp , ^pn— ia

[0026] çï 2 _ T ; m Jp 'Hmn.Hmp * Zpn

[0027] v; 2 _ _1_ n J p ' ^iim-Hpn ■ ^pn Zmp

[0028] with:

[0029] Znm the impedance equal to the ratio of the voltage Um of reception of the group of transducer(s) in the receiving state of index m to the current In of said group of transducer(s) in the transmitting state of index n;

[0030] Zmp the impedance equal to the ratio of the voltage Um of reception of the group of transducer(s) in reception state of index m to the current Ip of said reciprocal group of transducer(s) of index p;

[0031] Zpn the impedance equal to the ratio of the received voltage Up of the group of reciprocal transducer(s) of index p to the current In of said group of transducer(s) in transmitting state of index n;

[0032] Shm the voltage sensitivity in reception of the group of transducer(s) in reception state of index m;

[0033] Hpn the predetermined near-field propagation function from the group of transducer(s) of index n to the distinct group of transducer(s) of index p;

[0034] H„m the predetermined near-field propagation function from the group of transducer(s) of index n to the distinct group of transducer(s) of index m;

[0035] Hmp the predetermined near-field propagation function from the group of transducer(s) of index p to the distinct group of transducer(s) of index m;

[0036] If the current sensitivity at the emission of the group of transducer(s) with index n;

[0037] - the voltage sensitivity in reception of the transducer group(s) in state of reception index m, is obtained by arithmetic or geometric mean by considering a plurality of distinct triplets to which the group of transducer(s) in reception 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 transmission state;

[0038] - 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;

[0039] - said determination step is implemented by solving a system of equations in matrix form such that:

[0040] [Z] = [Sh]. [H]. [If]

[0041] [S / t] = [ J] ■ [«]

[0042] with:

[0043] [Z] said reciprocal coupling matrix;

[0044] [SA] the diagonal matrix of voltage sensitivities at the reception of the transducer group(s) of said plurality;

[0045] [H] the predetermined matrix of near-field propagation functions between the transducer group(s) of said plurality;

[0046] [If] the diagonal matrix of current sensitivities at emission of the transducer group(s) of said plurality;

[0047] [ . / ] the predetermined diagonal matrix of reciprocity functions for each transducer group(s).

[0048] 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,

[0049] said system comprising said antenna and the following modules:

[0050] - 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);

[0051] - an acquisition module configured to simultaneously acquire the current and the 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 to be connected / disconnected from each distinct transducer group of said transmitting transducer group(s), until, for each transmitting transducer group(s), each transducer group(s) of said distinct plurality of said transmitting transducer group(s) is used as a receiving transducer group(s);

[0052] - a obtaining module configured to obtain a reciprocal coupling matrix of said plurality of transducer groups of said NxN-sized 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 said group of transmitting transducer(s) its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current;

[0053] - 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.

[0054] 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 transducer(s) of an acoustic transmitting and receiving antenna, with N>3, comprises one or more of the following features, taken individually or in any technically possible combination:

[0055] - 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;

[0056] - each transducer is of a type belonging to the group comprising at least:

[0057] - piezoelectric acoustic transducers;

[0058] - electrodynamic acoustic transducers;

[0059] - assemblies of electromagnetic antennas.

[0060] 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:

[0061] [Fig-1] [Fig.1] is a schematic representation of a determination system of 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, with N>3, according to the present invention.

[0062] [Fig.2] [Fig.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) groups of an acoustic transmitting and receiving antenna, with N>3, according to the present invention.

[0063] Fig. 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 groups of transducer(s) of an acoustic transmitting and receiving antenna 12, with N > 3, according to the present invention.

[0064] As indicated previously, a reciprocal transducer is defined as a transducer 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.

[0065] Each transducer is of a type belonging to the group comprising at least:

[0066] - piezoelectric acoustic transducers;

[0067] - electrodynamic acoustic transducers;

[0068] - assemblies of electromagnetic antennas.

[0069] According to the embodiment illustrated in [Fig.1], the determination system 10 comprises said antenna 12.

[0070] On the example of [Fig.1], the antenna 12 comprises, by way of example, six transducers Tb T2, T3, T4, T5, T6, arranged in two rows, the upper row comprising the three transducers Tb 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 T1 and 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.

[0071] According to the present invention, a group of transducer(s) comprises at least one transducer.

[0072] Thus, according to a first example, each group of transducer(s) comprises a single transducer. Thus, according to [Fig. 1], the antenna 12 then comprises six (N=6) groups corresponding to the six individual transducers Tb T2, T3, T4, T5, T6.

[0073] According to a second example, each grouping of transducer(s) is a column of transducers when, as illustrated by [Fig. 1], the transducers of said antenna 12 are arranged in a plurality of rows and columns. Thus, according to [Fig. 1], the antenna 12 then comprises three (N=3) groups of transducers, namely the first column comprising the two transducers T1 and T4, the second column comprising the two transducers T2 and T5, and the third column comprising the two transducers T3 and T6.

[0074] According to a third example, each grouping of transducer(s) is a transducer line when, as illustrated by [Fig. 1], the transducers of said antenna 12 are arranged in a plurality of rows and columns. Thus, according to [Fig. 1], the antenna 12 comprises two (N=2) groups of transducers, namely the upper row comprising the three transducers T2, T3, and the lower row comprising the three transducers T4, T5, and T6.

[0075] The following describes the implementation of the invention according to the first example where each group of transducer(s) comprises a single transducer.

[0076] According to the example in [Fig.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).

[0077] In [Fig.1], the transmission module 14 is connected first of all to the transducer group comprising the single transducer Ti.

[0078] Said emission module 14 is suitable for being connected / disconnected from each group of transducers, according to the example in [Fig.1], each group corresponding to one of the individual transducers, at each iteration, until each group of transducer(s) (i.e. according to this first example until each individual transducer) of said plurality is used as the group of emission transducer(s).

[0079] In other words, the transmission module 14 is suitable for being connected to the transducer Ti, then disconnected from transducer Ti to be connected to another of the transducers T2, T3, T4, T5, T6, for example transducer T2, or even transducer T3, and so on until each individual transducer of said plurality is used as an emission transducer, and this in a predetermined or any order.

[0080] As illustrated by [Fig.1], the transmission module 14 includes in particular a signal generator G 14i whose output is connected to a signal amplifier A 142 whose output corresponds to the output of the transmission module 14 supplied at the input of each transducer.

[0081] As an optional addition, said emitted acoustic signal is of a type belonging to the group comprising at least:

[0082] - a fixed frequency pulse (CW from the English Continuons Wave);

[0083] - a frequency modulated pulse (FM from the English Frequency Modulation);

[0084] - a noise.

[0085] As an optional addition, said noise is periodic or aperiodic.

[0086] According to the example in [Fig. 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 transmitting transducer(s), the transducer Ti in the example in [Fig. 1], and the reception voltage of each group of transducers of said distinct plurality of said group of transmitting transducers (i.e., the module 16 can iteratively acquire the signals of a single group of transducers distinct from said group of transmitting transducers, or of several groups of transducers distinct from said group of transmitting transducers. simultaneously, so that the signals from all the receiving transducers are acquired), said acquisition module 16 being able to be connected / disconnected from each group of transducers distinct from said group of transmitting transducer(s), until, for each group of transmitting transducer(s), each group of transducers of said plurality distinct from said group of transmitting transducer(s) is used as a group of receiving transducer(s).

[0087] In [Fig. 1], the acquisition module 16 is shown, by way of example, connected to the transducer T5 while it is the transducer Ti that is transmitting. Not shown, when the transducer Ti transmits, the acquisition module 16 is able to be connected / disconnected successively or simultaneously from each transducer T2, T3, T4, T5, T6 until each group of transducer(s) (i.e., here each individual transducer) of said plurality is used as the receiving transducer group(s) when the transducer Ti transmits.

[0088] Similarly, when transducer T2 transmits, the acquisition module 16 is suitable to be connected / disconnected successively or simultaneously from each transducer 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 transducer T2 transmits, and so on until each group of transducer(s) of said plurality is used as a group of transmitting transducer(s).

[0089] As illustrated by [Fig.1], the acquisition module 16 includes an Acq 16i system for acquiring received signals optionally preceded by a PA 162 preamplifier (i.e., whose output feeds said 16i acquisition system).

[0090] 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 said transmitting transducer group(s) with its transmitting impedance measurement equal to the ratio of its transmitting voltage to its transmitting current.

[0091] Then the output of said gaining 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.

[0092] In the example of [Fig.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.

[0093] 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.

[0094] In the example of [Fig. 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 an acquisition program and a determination program 20. The processor 28 is then capable of executing each of the programs, namely the acquisition program and the determination program.

[0095] In an alternative not shown, the acquisition module and the determination module are each implemented in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or an integrated circuit, such as an ASIC (Application Specified Integrated Circuit).

[0096] When the electronic determination device 22 is implemented in the form of one or more software programs, i.e., in the form of a computer program, also called a computer program product, it is further capable of being stored on a computer-readable medium, not shown. The computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. By way of example, the readable medium is 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.

[0097] In relation to [Fig.2], an example of an embodiment of the operation, according to the present invention, of the 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) groups of an acoustic transmitting and receiving antenna 12 is described.

[0098] More specifically, the 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 groups of transducer(s) of an acoustic transmitting and receiving antenna, comprises all first a first step 32 of emission E of an acoustic signal by one of said transducer group(s) of said plurality used as emission transducer group(s).

[0099] As an optional addition, said emitted acoustic signal is of a type belonging to the group comprising at least:

[0100] - a pulse at a fixed frequency;

[0101] - a frequency modulated pulse;

[0102] -a noise.

[0103] Then the method 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).

[0104] More specifically, for an iteration of index i associated with the group of transmitting transducer(s), the acquisition is repeated, until, for each group of transmitting transducer(s), each group of transducer(s) of said plurality distinct from said group of transmitting transducer(s) is used as a group of receiving transducer(s).

[0105] During step 36, it is tested whether i=N which amounts to verifying that each group of transducer(s) of said plurality is used as a group of emission transducer(s).

[0106] In the negative 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.

[0107] In other words, during each iteration of index i with l <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.

[0108] In the affirmative (i.e. if i=N) according to arrow 40, the method then comprises 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.

[0109] More precisely, each term Zkj is the measure of the received voltage Uk divided by the transmitted current Ij regardless of the different transducers k of the emission transducer with index j, with l <j<N et l<k^j<N (i.e. Zk j est égal à Uj divisé par Ij), et chaque terme diagonal Zjj de la matrice [Z] est la mesure de l’impédance du transducteur] à l’émission (i.e. Zjj est égal à Uj divisé par Ij).

[0110] Finally, from said impedances of said reciprocal coupling matrix, the method 30 includes a step 44 of determining D_I the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

[0111] Not shown, the results of step 44 of determining D_I of the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality are stored over time to know the variations over time or the dispersion of these sensitivities over all the transducers constituting the antenna, and depending on this, trigger or not a targeted maintenance operation, targeting only the transducers detected as defective because they have variations over time greater than a predetermined variation threshold or a sensitivity dispersion greater than a predetermined dispersion threshold.

[0112] Several variants illustrated by [Fig.2] are suitable for use to achieve said determination of the voltage sensitivity in reception and the current sensitivity in transmission of each group of transducer(s) of said plurality.

[0113] According to a first variant 46, said determination step 44 comprises a plurality of iterations (not shown for simplicity) until the receive voltage sensitivity and the 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, whose value JP is a predetermined function of its sensitivity ratio, called the reciprocity term, such that: r_ with Shp its receive voltage sensitivity and JP~ Sip Sip, its 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:

[0114] y _ . y _ , y _ ; ^mn ~ I„ y ^mp - ip , ^pn - jn

[0115] here. 2 - t Hi>“ z,m 'Zmp ; m Jp 'Hmn.Hmp * Zpn

[0116] ç; 2_ 1 __^L_ Zmn ■ ^pn Jp ' fftm-ffpn ' Z»W

[0117] with:

[0118] Znm the impedance equal to the ratio of the voltage Um of the receiving transducer group(s) in the receiving state of index m to the current In of said transducer group(s) in the transmitting state of index n;

[0119] Zmp the impedance equal to the ratio of the voltage Um of reception of the group of transducer(s) in reception state of index m to the current Ip of said reciprocal group of transducer(s) of index p;

[0120] Zpn the impedance equal to the ratio of the received voltage Up of the group of reciprocal transducer(s) of index p to the current In of said group of transducer(s) in transmitting state of index n;

[0121] Shm the voltage sensitivity in reception of the transducer group(s) in reception state of index m;

[0122] Hpn the predetermined near-field propagation function from the group of transducer(s) of index n to the distinct group of transducer(s) of index p;

[0123] H„m the predetermined near-field propagation function from the group of transducer(s) of index n to the distinct group of transducer(s) of index m;

[0124] Hmp the predetermined near-field propagation function from the group of transducer(s) of index p to the distinct group of transducer(s) of index m;

[0125] If the current sensitivity at the emission of the group of transducer(s) of index n,

[0126] the functions Jp, Hpn, Hmn, Hmp having been previously determined and being used as inputs to said process.

[0127] For example, in relation to [Fig.1], the group of transducer(s) in transmitting state of index n includes only the transducer Tb, 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.

[0128] According to a first option 48 of this first variant 46, only one triplet S_T per iteration is considered.

[0129] According to a second option 50 of this first variant 46, the voltage sensitivity in receive of the transducer group(s) in receive state of index m is obtained by a substep 52 of calculating an arithmetic or geometric mean M by considering, according to this second option 50, a plurality P_T of distinct triplets to which the transducer group(s) in receive state of index m belongs, and from one triplet to another, at least one group of different transducer(s) between the reciprocal transducer group(s) and the transducer group(s) in transmitting state.

[0130] As an optional complement to this second option 50, the method 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.

[0131] According to a second variant 56, said determination step 44 is implemented by solving a system of equations in matrix form such as:

[0132] [Z] = [Sh]. [H]. [Sf]

[0133] [Sh] = [ J] . [Si]

[0134] with:

[0135] [Z] said reciprocal coupling matrix;

[0136] [SÆ] the diagonal matrix of voltage sensitivities at the reception of the transducer group(s) of said plurality;

[0137] [H] the predetermined matrix of near-field propagation functions between the transducer group(s) of said plurality;

[0138] [If] the diagonal matrix of current sensitivities at emission of the transducer group(s) of said plurality;

[0139] [ J] the predetermined diagonal matrix of reciprocity functions for each transducer group(s).

[0140] 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.

[0141] 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).

[0142] 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.

[0143] It is therefore advantageously feasible to carry out at the dock when said antenna is in particular a sonar antenna installed on a boat.

[0144] The reciprocal coupling measurement method also offers other advantages, namely highlighting the individual operation of each transducer, the ability to check the transmission and reception response and to track these characteristics over time, as well as the ability to verify the correct wiring of the transducers.

Claims

1. Demands 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 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); the said emission and acquisition steps being repeated until each group of transducer(s) of said plurality is used as a group of emission transducer(s); - obtaining (42) 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), 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 the said impedances of the said reciprocal coupling matrix, determination (44) of the voltage sensitivity in reception and sensitivity in current in transmission of each group of transducer(s) of said plurality.

2. Method according to claim 1 wherein said emitted acoustic signal is of a type belonging to the group comprising at least: - a fixed frequency pulse; - a frequency modulated pulse; - 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 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 group(s) of said plurality of N reciprocal transducer groups distinct from one iteration to another, 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, the value of which JP is a predetermined function of its sensitivity ratio, called the reciprocity term, such that: ._ with Shp its voltage sensitivity in receive and Sip its current sensitivity in transmit at receive, is used with said triplet to determine the voltage sensitivity in receive of the group of transducer(s) in receive state of index m and the current sensitivity in transmit of the group of transducer(s) in transmit state of index n, such that: y lll . y P * ^nm - In » ^mp- jp ; ^pn~ ju ci 2 _ j ^im ; -Jp * Hinn.Hmp * Z pu C' — 1 Jp ' Hpm.Hpa ' Zmp with: Zmn the impedance equal to the ratio of the voltage Um of receive of the group of transducer(s) in receive state of index m to the current In of said group of transducer(s) in transmit state of index n ;. Zmp the impedance equal to the ratio of the received voltage Um of the transducer group(s) in the receiving state of index m to the current Ip of said reciprocal transducer group(s) of index p; Z pu the impedance equal to the ratio of the received voltage Up of the reciprocal transducer group(s) of index p to the current In of said transducer group(s) in the transmitting state of index n; Shm the received voltage sensitivity of the transducer group(s) in the receiving state of index m; Hpn the predetermined near-field propagation function from the transducer group(s) of index n to the distinct transducer group(s) of index p; Hmn the predetermined near-field propagation function from the transducer group(s) of index n to the distinct transducer group(s) of index m;Hmp is the predetermined near-field propagation function from the group of transducers with index p to the distinct group of transducers with index m; Sin is the current sensitivity at emission from the group of transducers with index n.

5. A method according to claim 4, wherein the voltage sensitivity in receive of the transducer group(s) in receive state of index m is obtained by arithmetic or geometric mean by considering a plurality of distinct triplets to which the transducer group(s) in receive state of index m belongs, and from one triplet to another, at least one different transducer group(s) between the reciprocal transducer group(s) and the transducer group(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] = [Sh] . [H] . [Sz] [5½] = [J]. [Si] with: [Z] said reciprocal coupling matrix; [5½] 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; [Sï] the diagonal matrix of current sensitivities at transmission of the transducer group(s) of said plurality; [J] the predetermined diagonal matrix of reciprocity functions for each transducer group(s).

8. System (10) for determining the voltage sensitivity in reception and the current sensitivity in transmission of each transducer group(s) belonging to a plurality of N reciprocal transducer groups of an acoustic transmitting and receiving 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 transducer group comprising at least one transducer, said system comprising said antenna (12) and the following modules: - an acoustic signal transmission module (14) configured to initiate the transmission of an acoustic signal by one of said transducer groups of said plurality used as a transmitting transducer group(s),said transmission module being suitable for being connected / disconnected from each group of transducers, at each iteration, until each group of transducers of said plurality is used as a group of transmission transducers; - an acquisition module (16) configured to simultaneously acquire the current and voltage of said group of transmission transducers and the reception voltage of each group of transducers of said plurality distinct from said group of transmission transducers, said acquisition module being suitable for being connected / disconnected from each, grouping of transducers distinct from said grouping of transmitting transducer(s), until, for each grouping of transmitting transducer(s), each grouping of transducers of said plurality distinct from said grouping of transmitting transducer(s) is used as a grouping of receiving transducer(s); - a generation 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), 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; - 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 wherein 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. A system according to claim 8 or 9 in which each transducer is of a type belonging to the group comprising at least: - piezoelectric acoustic transducers; - electrodynamic acoustic transducers; - sets of electromagnetic antennas.

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