AU2003200979A1

AU2003200979A1 - Underwater antenna

Info

Publication number: AU2003200979A1
Application number: AU2003200979A
Authority: AU
Inventors: Siegfried Kruger; Norbert Wittschief
Original assignee: Atlas Elektronik GmbH
Current assignee: Atlas Elektronik GmbH
Priority date: 2002-03-20
Filing date: 2003-03-12
Publication date: 2003-10-16
Anticipated expiration: 2023-03-12
Also published as: ES2374883T3; AU2003200979B2; ATE532087T1; EP1347310B1; PT1347310E; AU2003200979A8; EP1347310A3; DE10212291C1; EP1347310A2; AU2003200979B8

Abstract

The device has at least one hydrophone (10) and an associated symmetrical electrical amplifier circuit (11) with two identical charge amplifiers (12), each with an inverting and a non-inverting input, of which two similar inputs are connected to null voltage and two are connected to the hydrophone. The hydrophone has two series connected electroacoustic transducer elements (17,18) and the connection (19) between them is set to null potential.

Description

AUSTRALIA

Patents Act 1990 STN ATLAS ELEKTRONIK GMBH COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Underwater antenna The following statement is a full. description of this invention including the best method of performing it known to us:- The invention concerns an underwater antenna of the type defined in the preamble of claim 1.

Underwater antennae of contemporary construction for receiving sound have a plurality of electro-acoustic transducers called hydrophones that are combined into an array. Underwater antennae of contemporary construction are cylinder bases, flank array, PRS bases, intercept bases, etc. An amplifier circuit is connected downstream to the microphones to amplify the electric output signals of the hydrophone.

A known electric amplifier circuit (DE 100 47 396 Al, published on 26.3.2002) has a symmetrical construction and has two equal charge amplifiers with a voltage amplifier the voltage amplification of which can be changed in stages connected to them. The non-inverting amplifying inputs of the charge amplifiers are set to zero potential and their inverting inputs are connected to the hydrophone. As charge amplifiers so called low-noise charge amplifiers are used, like, for example, those offered by the Analog Devices company, www.analog.com, with the type designation of AD 745. Such a charge amplifier has a high charging sensitivity and low current and voltage noise and consequently is particularly suitable for hydrophones, that supply only a low charging current.

The object of the invention is to modify an underwater antenna of the type mentioned in the introduction in such a manner, that the inherent noise of the charge amplifier in the underwater antenna could be influenced with the aim of reducing it.

According to the invention the object is achieved by the features of claim 1.

The underwater antenna according to the invention has the advantage that the hydrophones have a mid-terminal between two electro-acoustic transducer elements that is connected.to zero potential or earthed and thus the downstream connected charge amplifiers have a capacitance set to zero potential. Due to this and the introduction of correspondingly dimensioned RC member into the amplifier inputs, said RC member being matched to suit the respective source impedance, therefore in this case the impedance of the connected transducer element, each charge amplifier can be balanced. In contrast to an unbalanced charge amplifier a balanced charge amplifier has only low voltage noises, particularly in the range of smaller capacitances, like the ones hydrophones have.

Appropriate embodiments of the underwater antenna according to the invention with advantageous developments and constructions of the invention become apparent from the further claims.

According to a preferred embodiment of the invention each transducer element of the least one hydrophone comprises a hemispheric shell made from radially polarised, piezo-electric material, the internal and external surfaces of the shells being coated with an electrode. Both hemispheric shells have opposite polarisation and assembled along their edges into a hollow sphere by interposing an electric insulator between them. Both external electrodes of the hemispheric shells are connected to zero potential, and both internal electrodes of both hemispheric shells are connected via a lead each to one of the charge amplifiers. By virtue of this construction of the hydrophone from two hemispheric shell and by virtue of the described wiring of the electrodes the external electrodes of both hemispheric shells are earthed and simultaneously form a shielding of the hydrophone against radiated electric interferences in the surrounding region.

To enable the contact between the internal electrodes of both hemispheric shells, according to an advantageous embodiment of the invention at least one hemispheric shell has a radial bore, through which the leads to'the internal electrodes are guided. In this conjunction, as an alternative, both leads can be conveyed through a single radial bore or a radial bore for one lead may be provided in each hemispheric shell.

According to an alternative embodiment of the invention a hollow sphere is used for each electro-acoustic transducer element of the hydrophone, the hollow sphere being assembled from two hemispheric shells made from'a polarised, piezoelectric material by interposing an insulation and the internal and external shell surfaces of which are coated with an electrode each. If the two hemispheric shells are opposite polarised, then both internal electrodes in each hollow sphere are brought into contact with one another and an external electrode on one hemispherical shell of one of the hollow spheres and an external electrode on the opposite polarised hemispheric shell of the other hollow sphere are connected together to zero potential or earthed, whereas the remaining internal and external electrodes on both hollow spheres are connected to one each of the amplifier inputs of the two charge amplifiers.

The advantage of such an arrangement of the electro-acoustic transducer elements of the hydrophone is that the bores in the hollow spheres for passing through a lead to the internal electrodes are avoided. By virtue of the series connection of two electroacoustic transducer elements, each having two hemispheric shells, obtained by this, the hydrophone has only half the capacitance as the hydrophone built from a single hollow sphere with two hemispheric shells, however, advantageously it has a higher voltage sensitivity. By virtue of the capability to balance the charge amplifiers made feasible by the invention, the reduced capacitance does not affect its current and voltage noises.

According to an alternative embodiment of the invention a hollow sphere is used for each electro-acoustic transducer element of the hydrophone, said hollow sphere being assembled from two hemispheric shells made from polarised, piezoelectric material by interposing an insulation and the internal and external shell surfaces of which are coated with an electrode each. Both hemispheric shells are polarised in the same direction and the external electrodes of both hemispheres are connected to zero potential, whereas the internal electrodes of one hollow sphere and the internal electrodes of the other hollow sphere are connected to each of the two charge amplifiers. By virtue df the achieved by this parallel connection of two electroacoustic transducer elements, each having two hemispheric shells, this hydrophone has twice the capacitance of the hydrophone built from a single hollow sphere with two hemispheric shells and, in addition, shields against radiated electric interferences in the surrounding region due to the earthing of the external electrodes of the hollow spheres. However, a bore has to be provided in each hemishell of both hollow spheres to pass through a connecting lead to both internal electrodes.

The invention is explained in detail on the basis of embodiments illustrated in the drawing. They show in: Fig. 1 a circuit diagram of a circuit arrangement of a hydiophone with a symmetrical electric amplifier circuit allocated to it, Fig. 2 a schematicallyi illustrated cross-section of the hydrophone of Fig. 1, Fig. 3 a schematically illustrated cross-section of a modified hydrophone of Fig. 1, Fig. 4 an equivalent circuit diagram of the hydrophone of Figs. 2 and 3, MOMMEM4 Fig. 5 a cross-section of a hydrophone of Fig. 1 according to a further embodiment, Fig. 6 an equivalent circuit diagram of the hydrophone of Fig. Fig. 7 the same illustration as Fig. 5 with a modification of the hydrophone of Fig. Fig. 8 an equivalent circuit diagram of the hydrophone of Fig. 7, Fig. 9 the same illustration as Fig. 7 with a further modification of the hydrophone.

The underwater antenna used in this case as a receiving antenna has a plurality of electro-acoustic transducers described here as hydrophones 10, of which only one is illustrated in Fig. 1. To each hydrophone 10 a symmetrical, electric amplifier circuit 11 is allocated, that has two equal charge amplifiers 12 each with one inverting and noninverting amplifier input and with a voltage amplifier 13 the voltage amplification of which can be changed in stages. To the output of the voltage amplifier 13 a digitaliser.

block 14 that comprises the analog/digital transducer and the adapter amplifier connected upstream to it. The amplifier circuit 11 and the digitaliser block 14 form a so called hydrophone channel 15, on the output 151 of which the amplified and digitalised output signal of the hydrophone 10 can be picked up for the purpose of conveying it to a signal processing unit. The components of the hydrophone channel are provided on a printed circuit board that is accommodated in a housing that is enclosed in a casting in the underwater antenna together with the hydrophone Both non-inverting amplifier inputs of both charge amplifiers 12 are connected to zero potential or earthed via an RC member 16 each, and both inverting inputs are connected to the hydrophone 10. The charge amplifiers 12 have an identical construction and have the same amplification. To realise the charge amplifier, operation amplifiers of the AD 745 type of the Analog Devices company, www.analog.com with corresponding circuits are used with a corresponding design of the feedback path.

MOMMM"

The hydrophone 10, the schematic cross-section of which is illustrated in Fig. 2, has two hemispheric shells 21, 22 made from radially polarised, piezo-electric material, that are assembled into a hollow sphere 20. Between the abutting, annular faces of the two hemispheric shells 21, 22 an electric insulating ring 23 is provided.

The internal and external shell surfaces of both hemispheric shells 21, 22 are coated with an electrode each. Thus, according to Fig. 2, the hemispheric shell 21 has the internal electrode 211 and the external electrode 212 and the hemispheric shell 22 the internal electrode 221 and the external electrode 222. The hemispheric shells 21, 22 have opposite polarisation, so that for example the direction of polarisation of the hemispheric shell 21 runs from the interior to the exterior and the polarisation of the hemispheric shell 22 from the exterior to the interior as this is indicated in Fig.2 by arrows 31 and 32. Each hemispheric shell 21, 22 forms an electronic transducer element 17 and 18, respectively, the electric equivalent circuit of which is illustrated in Fig. 4. Both transducer elements 17, 18 are connected in series as this becomes obvious from the equivalent circuit diagram of Fig. 4, and the electrical connection 19 between the two transducer elements 17, 18 is connected to zero potential or earthed.

To enable to realise the connections to the internal electrodes 221, 222 for the hollow sphere 20 according to Fig. 2, a radial bore 24 is introduced in the hemispheric shell 22, through which two connecting leads 25, 26 are passed to the internal electrodes 211 and 221, respectively, of the hemispheric shells 21 and 22. The connecting leads 25 and 26 are fitted with the connecting terminals 1 and 2 of the hydrophone 10, that are to be connected to the two charge amplifiers 12. Both external electrodes 212 and 222 of both hemispheric shells 21, 22 are connected with one another and are connected to the mid-terminal 0 of the hydrophone 10 via a connecting lead 27. It is, of course, also feasible to connect both external electrodes 212 and 222 of the two hemispheric shells 21, 22 to the connecting terminals 1 and 2, respectively, and to connect both internal electrodes 211 and 221 to the mid-terminal 0. The first-mentioned circuitry has, however, the advantage that both external electrodes 212 and 222 of the hollow sphere are earthed and consequently form a shielding of the hydrophone 10 against radiated electrical interferences from the surrounding region.

By a suitable design of the RC members 16 on the non-inverting inputs of the charge amplifiers 12, which now can be singly and without reciprocally influencing one another adjusted to suit the impedance of the allocated transducer element 17 and 18, respectively, the charge amplifiers 12 can be balanced, thus considerably reducing their voltage and current noises which are relatively high in the case of non-balanced charge amplifiers due to the small capacitances of the hydrophone 10, as a matter of fact to a magnitude that the non-balanced charge amplifier has only in the case of a hundred times greater input capacitance.

The hydrophone 10, the cross-section of which is schematically illustrated in Fig. 3, is once again assembled from two transducer elements 17, 18, it has the same hollow spherical construction as the hydrophone according to Fig. 2. The only difference is that the hemispheric shell 21 has the same radial bore 24 that is provided in the hemispheric shell 22. The two connecting leads 25, 26 cbnnected to the internal electrodes 211 and 221 and the connecting terminals 1 and 2 are passed through the radial bores 24. Otherwise the construction of the hollow sphere 20 of Fig. 3 concurs with that of the hollow sphere 20 of Fig. 2, so that the same components are designated with the same reference numerals.

In the case of the hydrophone 10 schematically illustrated in Fig. 5 each transducer element 17 and 18 is formed by a hollow sphere 20 or 20', as this was already described in conjunction with Fig. 2. The equivalent circuit diagram of the hydrophone 10 according to Fig. 5 is illustrated in Fig. 6, while the illustration of the resistances also present has been omitted. Accordingly, each electro-acoustic transducer element 17, 18 of the hydrophone 10 has two capacitors connected in series, which, in turn, are also connected in series. Thus the capacitance of the hydrophone 10 according to Fig. 5 is-only half of the capacitance of the hydrophone according to Fig.2. The internal electrodes 211 and 221 of both hemispheric shells 21, 22 are in electrical contact with one another in each hollow sphere 20 and 20'. Of the external electrodes 212 and 222 of both hollow spheres 20, 20' one external electrode 212 on one hemispheric shell 21 of a hollow sphere 20 together with the external electrode 222 on the hemispheric shell 22 having an inversed direction of polarisation to the other hollow sphere 20' is connected to the mid-terminal 0 via the connecting lead 27, whereas the remaining external electrode 222 of one hollow sphere 20 and 212 of the other hollow sphere 20' are brought into contact with the connecting terminal 1 and connecting terminal 2, respectively, via the connecting leads 25 and 26, respectively. This construction of the hydrophone 10 has the advantage that the radial bores in the hemispheric shells 21, 22 of the hollow spheres 20, 20' are omitted.

The hydrophone 10 illustrated in Fig. 7, just like the hydrophone 10 according to Fig. 5, is made up from two hollow spheres 20, 20', of which.each is assembled from two hemispheric shells 21, 22 made from radially polarised, piezo-electric material, while between the abutting faces of the two hemispheric shells 21, 22 once again an insulating ring 23 is inserted. The radial polarisation of the hemispheric shells 21, 22 is in the same direction. The two internal electrodes 211 and 221 of one hollow sphere are in contact with one another and connected to the connecting terminal 1 of the hydrophone 10 via the connecting lead 25, that is passed through a radial bore 24 in the hemishell 21. The two external electrodes 212 and 222 of the other hollow sphere together are brought into contact with the connecting terminal 2 of the hydrophone via the connecting lead 26. Both remaining internal electrodes 211, 221 of one hollow sphere 20 are connected to the mid-terminal 0 via the connecting lead 27, that is passed through a radial bore 24 in the hemispheric shell 22. The two remaining external electrodes 212 and 222 of the other hollow sphere 20' are also connected to this connecting lead 27. The equivalent circuit diagram of this hydrophone 10 is illustrated in Fig.8, while once again the resistances present have been omitted. In each electro-acoustic transducer element 17 and 18 of the hydrophone 10 the capacitors of both hemispheric shells 21, 22 are connected in parallel. The capacitors of both hollow spheres 20, 20' are connected in series. Consequently the hydrophone 10 according to Fig. 7 has twice the capacitance of the hydrophone 10 according to Fig. 2.

The construction of the hydrophone 10 schematically illustrated in Fig. 9 corresponds to that of the hydrophone 10 in Fig. 7, however, the internal electrodes 211 and 221 and the external electrodes 212 and 222 of both hollow spheres 20, 20' are differently allocated. Thus the external electrodes 212 and 222 of both hollow spheres 20' are connected to the mid-terminal 0 via the connecting lead 27, whereas both internal electrodes 211 and 221 of the hollow sphere 20 are brought into contact with the connecting terminal 1 via the connecting lead 25 and of the hollow sphere 20' with the connecting terminal 2 of the hydrophone 10 via the connecting lead 26. The advantage of this is that the external electrodes 212 and 222 of both hollow spheres are earthed and due to this the hydrophone 10 is again shielded. The electrical equivalent circuit diagram of this hydrophone 10 corresponds to that of Fig. 8.

The invention is not limited to the embodiment described here. Thus the hydrophone 10 does not need to be connected to the non-inverting amplifier inputs of the two charge amplifiers 12, the inverting inputs of which are connected to zero potential with an appropriate RC circuit to balance the charge amplifiers 12. It is not necessary either to make the electro-acoustic transducer elements as hemishells from piezo-electric material and to assemble two transducer elements to form a hollow 9 sphere. The transducer elements can be produced also as full cylinders or parallelepipeds, with an electrode each applied to the surfaces opposing one another.

Claims

1. An underwater antenna with at least one hydrophone and a symmetrical electric amplifier circuit allocated to the hydrophone, said amplifier circuit having two equal charge amplifiers with an inverting and non-inverting amplifier input each, of which two amplifier inputs of the same kind are connected to the zero potential and two amplifier inputs of the same kind are connected to the hydrophone, characterised in that the hydrophone has two electro-acoustic transducer elements connected in series and that the connection between the transducer elements is connected to zero potential.

2. An underwater antenna according to claim 1, characterised in that between each of the amplifier inputs of the charge amplifier connected to zero potential and the zero potential an RC member is provided to balance each one of the two charge amplifiers.

3. An underwater antenna according to claim 1 or 2, characterised in that the electro- acoustic transducer elements of at least one hydrophone have at least approximately the same capacitance.

4. An underwater antenna according to any one of claims 1 to 3, characterised in that each electro-acoustic transducer element of the least one hydrophone comprises a hemispheric shell made from radially polarised, piezo-electric material, the internal and external surfaces of the shells being coated with an electrode each, that both hemispheric shells have opposite polarisation and assembled along their edges into a hollow sphere by interposing an electric insulator between them and that both external electrodes of the hemispheric shells are connected to zero potential and both internal electrodes of the hemispheric shells are connected via a connecting lead each to one of the charge amplifiers.

An underwater antenna according to claim 4, characterised'in that the connecting leads are passed through a radial bore in one of the hemispheric shells.

6. An underwater antenna according to claim 4, characterised in that each of the two hemispheric shells has a radial bore and that leads are conveyed to the internal electrodes through at least one of the radial bores.

7. An underwater antenna according to any one of claims 1 to 3, characterised in that each electro-acoustic transducer element of the least one hydrophone is constructed from a hollow sphere assembled from two 'hemispheric shells with an interposed electric insulation and that the hemispheric shells of each hollow sphere are made from a radially polarised, piezo-electric material and the internal and external shell surfaces of the hemispheric shells are coated with an electrode each.

8. An underwater antenna according to claim 7, characterised in that both hemispheric shells of each hollow sphere have opposite polarisation, that both internal electrodes in each hollow sphere are brought into contact with one another, that one external electrode on one hemispheric shell of one of the hollow spheres and an external electrode on the opposite polarised hemispheric shell of the other hollow sphere are connected to zero potential and that the remaining two external electrodes of both hollow spheres are connected to one each of the charge amplifiers.

9. An underwater antenna according to claim 7, characterised in that both hemispheric shells of each hollow sphere are polarised in" the same direction, that the external electrodes of one hollow sphere together with the internal electrodes of the other hollow sphere are connected to zero potential and that the remaining external electrodes of one hollow sphere and the remaining internal'electrodes of the other hollow sphere are connected to one each of the charge amplifiers.

An underwater antenna according to claim 9, characterised in that both internal electrodes of each hollow sphere are connected with one another and can be brought into contact on the outside via a connecting lead passed through a radial bore.

11. An underwater antenna according to claim 7, characterised in that both hemispheric shells of each hollow sphere are polarised in the same direction and that the external electrodes of both hollow spheres are connected to zero potential and the internal electrodes of one hollow sphere and the internal electrodes of the other hollow sphere are connected to one each of the charge amplifiers.

12. An underwater antenna according to any one of claims 1 to 11, characterised in that the hydrophone is connected to the inverting amplifier inputs of the charge amplifier. DATED this twelfth day of March 2003 STN ATLAS ELEKTRONIK GMBH Patent Attorneys for the Applicant: F.B. RICE CO.