AU2017201928B2

AU2017201928B2 - Bi-loop antenna for an underwater vehicle

Info

Publication number: AU2017201928B2
Application number: AU2017201928A
Authority: AU
Inventors: Didier CHULOT; Catherine Lamy-Bergot; Frédéric Ngo Bui Hung
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2016-03-22
Filing date: 2017-03-22
Publication date: 2021-05-13
Anticipated expiration: 2037-03-22
Also published as: FR3049397B1; BR102017005732A2; AU2017201928A1; EP3223360A1; FR3049397A1; MY187490A; EP3223360B1

Abstract

BI-LOOP ANTENNA FOR AN UNDERWATER VEHICLE ABSTRACT Transmitting and/or receiving antenna (1) intended to be borne by a submersible vehicle, characterized in that it comprises at least one of the following elements: • a support element (10); • a first loop (2) of a given shape comprising a first end (21) connected to a first point and a second end (22) connected to a common point; • a second loop (3) comprising a first end (31) connected to a second point and a second end (32) connected to the common point, having a shape similar to the shape of the first loop; • the two loops are symmetric with respect to the support element (10) and are supplied in phase opposition so that the currents returning to the common point balance each other out; • the first and the second loop being protected by an enclosure (8). Antenna system comprising an antenna according to the invention. (Figure 1) 1/4 A i38 22, 3 FIGIN . i1 i281 31 -- 4 50 ! - - . 9 - 90 FIG.1 BT - H FIG.3

Description

1/4

A

i38 22, 3

i1 i281

. 31 -- 4 50 ! FIGIN - - . 9 - 90

FIG.1

BT - H

FIG.3

BI-LOOP ANTENNA FOR AN UNDERWATER VEHICLE

Technical Field

[0001] The invention relates to a bi-loop transmitting and/or receiving antenna, intended to be installed on a vehicle that may be submerged and operates at high frequency in order to transmit and/or to receive high-frequency waves between said vehicle and a terrestrial base, for example. The antenna is used for transmissions in the frequency bands 1.5 to 30 MHz, for example, the transmission of data taking place via the ionosphere.

[0002] It relates to an antenna system allowing data of any format, audio, images or video, to be transmitted between a submersible vehicle and a terrestrial base, for example.

Background

[0003] Submersible vehicles generally transmit and receive signals via wire antennas towed or drawn by these submersible vehicles. These antennas are positioned so as to float on the surface of the water while the submersible vehicle is submerged at a greater depth.

[0004] When the submersible vehicle has to move from one location to another, the cable of the antenna must be wound in and wound onto a support, which may cause mechanical and electrical damage.

[0005] On the other hand, since the antenna floats on the surface, it is easy to repair.

[0006] As an example of an antenna according to the prior art, the patent application FR 2962854 discloses a wire antenna, for high-frequency submarine transmissions, comprising a coaxial cable and a radiating element, one end of which is connected to the coaxial cable, and which is dimensioned so as to transmit high-frequency waves.

[0007] The patent application FR 3003388 discloses an antenna comprising a coaxial cable and a radiating element, in which the antenna is towed behind a submersible vehicle and rises to the surface of the water, to the dioptre, in order to allow data exchanges and, in particular, HF transmissions.

[0008] The known antennas of the prior art are prone in particular to breakage of the connecting cable and mechanical problems during deployment or when winding the cable of the antenna onto a support. From a radiofrequency perspective, they offer low performance and may not be used as high-power transmission antennas, the transmission power typically being limited to a few watts.

[0009] The architecture of the antenna according to the invention is original in the sense that it comprises a double loop that is symmetric with respect to a support axis and which is isolated from the water in which it may be submerged by means of a dielectric enclosure, each loop being supplied with power in phase opposition so that the resultant of return currents to ground (water) cancel each other out, thereby substantially decreasing ohmic losses in the water.

Summary

[0010] It is an object of the present invention to substantially overcome or at least ameliorate one or more disadvantages of existing arrangements.

[0011] The invention relates to a transmitting and/or receiving antenna intended to be bome by a submersible vehicle characterized in that it comprises at least one of the following elements: • a support element made of a conductive material and adapted to distance the loops from the ground of the submersible vehicle and to electrically connect the assembly to this ground of the carrier; • a first loop of a given shape comprising a first end connected to a first point and a second end connected to a common point; • a second loop comprising a first end connected to a second point and a second end connected to the common point, having a shape similar to the shape of the first loop; • the two loops are symmetric with respect to an axis of symmetry A and are supplied with power in phase opposition so that the return currents to the common point balance each other out; • the first and the second loop being protected by an enclosure.

[0012] According to one embodiment, each of the second ends of the antenna is mechanically and electrically connected to the support corresponding to the axis of symmetry, the two other first ends of the antenna are adapted to be connected to the outputs of two identical tuning boxes.

[0013] An antenna loop is, for example, circular in shape, or else quadrilateral in shape.

[0014] The shape and the dimensions of an antenna loop are adapted for the antenna to operate in a frequency range [1.5 MHz, 30 MHz].

[0015] The antenna may also comprise a ferromagnetic core positioned in the centre of the two loops, which allows the size of the antenna to be decreased while maintaining a high level of performance.

[0016] The invention also relates to an antenna system characterized in that it comprises at least one antenna having one or more of the features mentioned above, said antenna being positioned on a ground reference-support and being supplied with power by a device comprising: Sa first tuning box having an output connected to the first end of the first loop; Sa second tuning box having an output connected to the first end of the second loop; • said reference-support is made of a conductive material and is adapted to distance the loops from the ground of the submersible vehicle and to electrically connect the assembly to this ground of the carrier; Sa power divider receiving, as input, a signal S transmitted by a transceiver and delivering a first signal S Isupplying the first loop with power and a second signal S2 in phase opposition with the first signal supplying a second loop with power.

[0017] The first tuning box, the second tuning box and the power divider may be integrated within one and the same assembly.

[0018] The antenna system is, for example, positioned on a submersible vehicle.

[0019] In a further embodiment of the present invention, the present invention seeks to provide a transmitting and/or receiving antenna intended to equip a submersible vehicle, wherein it comprises at least the following elements:

Sa support element made of a conductive material, Sa first loop of a given shape comprising a first end connected to a first point and a second end connected to a common point M, Sa second loop comprising a first end connected to a second point and a second end connected to the common point M, having a shape similar to the shape of the first loop, • means for supplying the first ends of the two loops in phase opposition so that the currents returning towards the common point M compensate for each other, Sa protective enclosure for protecting the first and the second loop, and wherein • the two loops are symmetric with respect to an axis of symmetry A corresponding to the support element, * the support element is mechanically and electrically connected to the second symmetrical ends and to the common point M, and • the support is configured to move the common point M and the loops away from the ground of the submersible vehicle and to electrically connect said two symmetrical ends to the ground of the submersible vehicle.

Brief Description of Drawings

[0020] Other features and advantages of the present invention will become more clearly apparent upon reading the description of exemplary embodiments given by way of wholly non limiting illustration, alongside the appended figures which show: • Figure 1, an example of an antenna according to the invention; • Figure 2, a functional representation of the antenna according to the invention; • Figure 3, an example of the use of an antenna system according to the invention on a submersible vehicle; • Figure 4A and Figure 4B, a variant embodiment for the tuning boxes installed in the system; • Figure 5, a variant of an antenna comprising a ferromagnetic core; and • Figure 6A and Figure 6B, examples of the geometry of watertight enclosures.

Description

[0021] In order to gain a better understanding of the structure of the antenna according to the invention, the description is provided for an antenna positioned on a submersible vehicle that can be submerged in seawater, the vehicle being located at a shallow depth. The antenna operates, for example, in a frequency range [1.5 MHz, 30 MHz].

[0022] Figure 1 shows an example of an antenna according to the invention intended to be positioned on a submersible vehicle (Figure 3, for example). The antenna 1 comprises a first antenna element in the shape of a loop 2 comprising a first end 21 connected to a first point corresponding to the output 4s of a tuning box 4 and a second end 22 connected to a common point M, the loop having a given shape, a second antenna element in the shape of a loop 3 that is symmetric with the first loop-shaped antenna element 2 with respect to an axis of symmetry A, the second loop 3 comprising a first end 31 connected to a second point corresponding, for example, to the output 5s of a second tuning box 5 and a second end 32 connected to the common point M, having a shape similar to the shape of the first loop, a power supply device, shown in detail in Figure 2, is designed to supply the two loops with power in phase opposition so that the ground return currents balance each other out. The second symmetric ends 22 and 32 are mechanically and electrically connected to a support 10 made of a conductive material corresponding to the axis of symmetry, thereby making it possible to distance the loops from the ground of the carrier (submersible vehicle) on which the antenna system is installed, and to fix and electrically connect the assembly to this ground of the carrier. The other first ends 21 and 31 are connected to the outputs of the two identical tuning boxes 4 and 5 (Figure 2), respectively, having the same operating characteristics.

[0023] The design and operation of the tuning boxes 4 and 5 are known to those skilled in the art and will not be described in detail in order to facilitate understanding of the invention.

[0024] As shown in Figure 1, the ground return currents i Iand i2 flow through the antenna elements or loops in opposite directions.

[0025] A loop may be a section piece made of a conductive material folded in order to form a first rectangular loop 2, which shape is used by way of example, and its symmetric counterpart, the second rectangular loop 3.

[0026] When used underwater (submarine equipment), the interior of the enclosure is filled, for example with a dielectric material, preferably polyurethane foam, for the purpose of providing resistance to hydrostatic pressure. When used on the surface, the interior of the enclosure is left filled with air.

[0027] The first end 21 of the first loop 2 is connected to the output 4s of the first tuning box 4, itself connected to one of the outputs 7s of a power divider 7 by means of a coaxial connecting cable 40. The input 7e of the power divider will be connected to a transceiver 11 by means of a coaxial cable 12 (Figure 2).

[0028] The first end 31 of the second loop 3 is connected to the output 5s of the second tuning box 5, itself connected to the other output 7s' of the power divider 7 by means of a second coaxial connecting cable 50.

[0029] The assembly is surrounded by a dielectric enclosure 8, composed, for example, of a radome made of reinforced plastic 81 and a foam filling 82.

[0030] The dielectric enclosure 8 is fixed to a metal fastening base 9 comprising holes 90 through which fastening screws are passed according to means known to those skilled in the art.

[0031] The protected antenna could thus be fixed to a submersible vehicle, as shown in Figure 3.

[0032] The shape, geometry and dimensions of an antenna element will be chosen in particular according to the operating frequency range of the antenna. These dimensions could also be chosen according to potential space constraints. The shape and the size of the assembly formed by the antenna and the watertight housing correspond, for example, to a parallelepipedal solid of approximately 2 m x 2 m x 1 m.

[0033] The antenna system thus formed may be installed in water on a submersible vehicle, on a surface vessel or else on land vehicles. It may be directly installed on the carrier without any offset, unlike the known structures of the prior art.

[0034] The antenna operates, for example, in the frequency range from 1.5 to 30 MHz and preferably between 2 and 12 MHz. The chosen radiation mode will be, for example, of near- vertical incidence ionospheric radio wave type, better known by the abbreviation NVIS for near vertical incidence skywave.

[0035] Figure 2 shows a functional diagram of the antenna according to the invention.

[0036] The antenna 1 is connected to a transceiver 11 by means of a coaxial cable 12. The radiofrequency signal S delivered by the coaxial cable is divided by the power divider 7 into two signals Sl, S2, which are in phase opposition.

[0037] The signal S Iis transmitted, via the first tuning box 4, to the first end 21 of the first loop 2. The second end 22 of the first loop is connected to a ground point M. The tuning box is composed, for example, of a first capacitor C1, of an inductor L and of a second capacitor C2 connected to a ground M, according to an arrangement known to those skilled in the art.

[0038] The second signal S2, which is in phase opposition with the first signal Sl, is transmitted, via the second tuning box 5, to the first end 31 of the second loop 3. The second end 32 of the second loop is connected to a ground point M. The second tuning box 5 is identical to the first tuning box 4 and is composed, for example, of a first capacitor C1, of an inductor L and of a second capacitor C2 connected to a ground M, according to an arrangement known to those skilled in the art.

[0039] By virtue of the symmetry of the radiating elements, the first loop and the second loop, and by virtue of the fact that they are supplied with power in phase opposition, the RF return currents are negligible, or even zero.

[0040] Placed within an isolating and watertight enclosure, the antenna is entirely isolated from its potentially conductive environment, e.g. from seawater. Ohmic losses are thus decreased.

[0041] Figure 3 is a diagram of the use of an antenna system according to the invention positioned on a submersible vehicle E. The vehicle is submerged at a depth H from the surface of the sea. The antenna communicates, for example, with a base BT located on land a reasonable distance away.

[0042] Figure 4A and Figure 4B show a variant embodiment in which the tuning box 4, the tuning box 5 and the power divider 7 are designed as and grouped into a single item of equipment 71.

[0043] Figure 5 schematically shows a variant in which a magnetic core 75, for example made of ferrite, is added to the centre of the two loops 2, 3. The ferromagnetic core is, for example, positioned and held in place by virtue of the filling foam 82. This advantageously allows the size of the antenna to be decreased while maintaining the same level of performance. Furthermore, the addition of mass makes it possible to compensate for upthrust in the configuration for use underwater.

[0044] Figure 6A schematically shows an example of an enclosure 60 having a parallelepipedal shape that may be mounted on a vertical wall. Figure 6B shows a variant 61 in which the parallelepipedal enclosure is mounted on a horizontal surface.

[0045] The antenna and the antenna system according to the invention may be used in numerous applications for the transmission of data between a submersible vehicle and a terrestrial base, the transmission of data taking place via the ionosphere.

[0046] The antenna according to the invention has, notably, the following advantages: Sa possibility of integrating the antenna into the structure of the carrier; • no deployment to place the antenna in operational configuration; • improved performance; Sa possibility of combining it with high-powered transmitters, typically of the order of 1 kW.

Claims

1. A Transmitting and/or receiving antenna intended to equip a submersible vehicle, wherein it comprises at least the following elements: Sa support element made of a conductive material, Sa first loop of a given shape comprising a first end connected to a first point and a second end connected to a common point M, • a second loop comprising a first end connected to a second point and a second end connected to the common point M, having a shape similar to the shape of the first loop, • means for supplying the first ends of the two loops in phase opposition so that the currents returning towards the common point M compensate for each other, Sa protective enclosure for protecting the first and the second loop, and wherein • the two loops are symmetric with respect to an axis of symmetry A corresponding to the support element, * the support element is mechanically and electrically connected to the second symmetrical ends and to the common point M, and • the support is configured to move the common point M and the loops away from the ground of the submersible vehicle and to electrically connect said two symmetrical ends to the ground of the submersible vehicle.

2. The Antenna according to claim 1, wherein the means for supplying the first ends of the two loops in phase opposition comprise two identical tuning boxes.

3. The Antenna according to claim 1, wherein a loop is circular in shape.

4. The Antenna according to claim 1, wherein a loop is quadrilateral in shape.

5. The Antenna according to one of claim 1 to 4, wherein the shape and the dimensions of a loop are designed for the antenna to operate in a frequency range [1.5 MHz, 30 MHz].

6. The Antenna according to one of the preceding claims, wherein it comprises a ferromagnetic core positioned in the centre of the two loops.

7. The Antenna according to claim 2, wherein the means for supplying the first ends, of the two loops in phase opposition further comprise a power divider receiving, as input, a signal S transmitted by a transceiver/receiver and delivering a first signal Si supplying the first loop with power and a second signal S2 in phase opposition supplying a second loop with power.

8. The Antenna according to claim 7, wherein the two tuning boxes, and the power divider are integrated within one and the same assembly.

9. A system comprising an antenna according to one of the preceding claims and a submersible vehicle on which said antenna is positioned.

THALES Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON