Acoustic transmitting antenna

Patent metadata

Field	Value
Publication number	US-12487348-B2
Application number	US-201917287097-A
Country	US
Kind code	B2
Filing date	Oct 16, 2019
Priority date	Oct 22, 2018
Publication date	Dec 2, 2025
Grant date	Dec 2, 2025

Abstract

An acoustic antenna intended to equip a sonar, the antenna being centred around a first longitudinal axis and includes at least a first assembly of at least two transducers and a second assembly of at least two transducers stacked along the longitudinal axis, each transducer having at least a radial mode having a resonance frequency, referred to as the radial frequency, and a cavity mode having a resonance frequency, referred to as the cavity frequency, wherein the transducers of the first assembly are configured to transmit sound waves in a first continuous frequency band extending at least between the cavity and radial frequencies of the transducers of the first assembly and the transducers of the second assembly are configured to transmit sound waves in a second continuous frequency band extending at least between the cavity and radial frequencies of the transducers of the second assembly, in that the cavity frequency of a transducer of the second assembly is equal to the radial frequency of a transducer of the first assembly plus or minus (fr 1 −fc 1 )/10, fr 1 being the radial frequency of the transducer of the first assembly and fc 1 being the cavity frequency of the transducers of the first assembly and wherein the transducers of the second assembly are positioned between the transducers of the first assembly and in that no transducer of the first assembly is positioned between the transducers of the second assembly.

First claim

The invention claimed is:

1 . An acoustic antenna (ANT) intended to equip a sonar, the antenna being centered around a first longitudinal axis (A 1 ) and comprising at least a first set of at least two transducers (T 1 ) and a second set of at least two transducers (T 2 ) stacked along said longitudinal axis, each transducer having at least one radial mode having a resonance frequency, referred to as a radial frequency, and one cavity mode having a resonance frequency, referred to as a cavity frequency, wherein the transducers of the first set are configured to transmit sound waves in a first continuous frequency band extending at least between the cavity frequencies and the radial frequencies of the transducers of the first set and the transducers of the second set are configured to transmit sound waves in a second continuous frequency band extending at least between the cavity frequencies and the radial frequencies of the transducers of the second set, in that the cavity frequency of a transducer of the second set is substantially equal to the radial frequency of a transducer of the first set plus or minus (fr 1 -fc 1 )/10, fr 1 being the radial frequency of the transducer of the first set and fc 1 being the cavity frequency of the transducer of the first set and wherein the transducers of the second set are placed between the transducers of the first set and in that no transducer of the first set is placed between the transducers of the second set;
wherein said acoustic antenna further comprises:
at least a first phase-shifter (D 1 ) arranged so as to introduce a first phase shift (Δϕ 1 ) between an excitation signal of the transducers of the first set and an excitation signal of at least a sub-group of transducers of the second set; and
at least a second phase-shifter (D 2 ) arranged so as to introduce a second phase shift (Δϕ 2 ) between excitation signals of different sub-groups of transducers of the second set.

2 . The acoustic antenna as claimed in claim 1 , wherein the transducers of the second set are divided into sub-groups, each sub-group comprising at least two transducers of the second set, a spacing between each sub-group being greater than or equal to a spacing between two transducers of one and the same sub-group, and each sub-group having at least one cavity mode having a resonance frequency, referred to as the group cavity frequency.

3 . The acoustic antenna as claimed in claim 2 , wherein the second set comprises seven transducers divided into three sub-groups, the first sub-group (SG 1 ) comprising two transducers, the second group (SG 2 ) comprising three transducers, the third sub-group (SG 3 ) comprising two transducers, and the second sub-group being placed between the first and the third sub-group.

4 . The acoustic antenna as claimed in claim 2 , wherein the group cavity frequency of at least one sub-group is equal to the radial frequency of the transducers of the first set plus or minus (fr 1 -fc 1 )/10 and the group cavity frequency of at least one other sub-group is equal to the cavity frequency of the transducers of the first set plus or minus (fr 1 -fc 1 )/10.

5 . The acoustic antenna as claimed in claim 1 comprising passive elements (P 1 ) stacked along the first longitudinal axis, surrounding the transducers of the second set and having at least one radial mode having a resonance frequency, referred to as the radial frequency, equal to a radial frequency of the transducers of the second set plus or minus 0.1×fr 2 , advantageously equal to a radial frequency of the transducers of the second set plus or minus 0.05×fr 2 , with fr 2 the radial frequency of the transducers of the second set and also having at least one cavity mode having a resonance frequency, referred to as the cavity frequency, within the first continuous frequency band.

6 . The acoustic antenna as claimed in claim 5 , wherein the passive elements are made of a material such that the E/ρ ratio of this material is higher than that of the material forming the transducers of the second set, E being the Young's modulus and ρ the density of the materials.

7 . The acoustic antenna as claimed in claim 6 , wherein the passive elements are cylinders having a diameter larger than that of the transducers of the second set.

8 . The acoustic antenna as claimed in claim 1 , wherein the transducers of the first set and of the second set are FFR (“free-flooded ring”) transducers made of piezoelectric ceramic or of magnetostrictive ceramic or of electrostrictive ceramics.

9 . The acoustic antenna as claimed in claim 1 , wherein the transducers of the first set and of the second set have a circular, trapezoidal or polygonal cross section.

10 . The acoustic antenna as claimed in claim 1 comprising at least a third set of at least two transducers (T 3 ) stacked along K longitudinal axes (A 2 , A 3 ) parallel to the first longitudinal axis (A 1 ), K being greater than 1, the transducers of the third set having at least one radial mode having a resonance frequency, referred to as the radial frequency, and one cavity mode having a resonance frequency, referred to as the cavity frequency, equal to the radial frequency of the transducers of the second set plus or minus (fr 2 -fc 2 )/10, fr 2 being the radial frequency of the transducers of the second set and fc 2 the cavity frequency of the transducers of the second set, the transducers of the third set being configured to transmit sound waves in a third continuous frequency band extending at least between their cavity frequency and their radial frequency, the third continuous frequency band having at least one frequency higher than the frequencies of the first and second continuous frequency bands, and a meeting of the first, second and third continuous frequency bands forming a continuous frequency band.

11 . The acoustic antenna as claimed in claim 10 , wherein the K longitudinal axes are coincident with the first longitudinal axis.

12 . The acoustic antenna as claimed in claim 1 comprising N+1 groups of transducers of the same type and N phase-shifters arranged so as to introduce a phase shift between an excitation signal of the transducers of the first group and an excitation signal of another group, N being an integer greater than 1.

13 . A method for calibrating an acoustic antenna as claimed in claim 1 , further comprising the following steps:
a: exciting a first group of transducers of the same type and shorting the other transducers; b: far-field measuring a phase of the pressure waves generated by the transducers of the first group; c: exciting a second group of transducers of the same type and shorting the other transducers; d: far-field measuring a phase of the pressure waves generated by the transducers of the second group; e: calculating the phase difference between the phase obtained in step b and the phase obtained in step d; f: adjusting a phase-shifter so that it introduces a phase shift equal to the difference calculated in step e to the excitation signal sent to the transducers of the second group.

Assignees

• Thales Sa

Inventors

• Lagier Yves
• LARDAT Raphaël
• Todesco Jérémie

Classifications

• G10K11/008 Primary

  Arrays of transducers (seismic streamers, see G01V1/20) · CPC title

• B06B2201/74

  Underwater · CPC title

• G01S7/52004 Primary

  Means for monitoring or calibrating (short-range imaging G01S7/5205) · CPC title

• B06B1/0633

  Cylindrical array · CPC title

• G01S7/534 Primary

  Details of non-pulse systems {(short-range imaging G01S7/52017)} · CPC title