EP3430691A1

EP3430691A1 - Coaxial connector comprising a shunt, coaxial cable and method for manufacturing such a connector

Info

Publication number: EP3430691A1
Application number: EP17711164.8A
Authority: EP
Inventors: Jean-Luc Dubois; Bruno Cassany; Jérôme RIBOLZI
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2016-03-17
Filing date: 2017-03-16
Publication date: 2019-01-23
Anticipated expiration: 2037-03-16
Also published as: FR3049119B1; US11108198B2; ES2851850T3; US20190081444A1; EP3430691B1; FR3049119A1; WO2017158111A1

Abstract

The invention relates to a coaxial connector (1) comprising a shunt. Said coaxial connector (1) includes: a conductive core (10); a metal shield (20) surrounding the core (10); a dielectric (30) positioned around the core (10) and the shield (20) in order to electrically insulate them from one another, and a shunt for providing a resistive bridge between the core (10) and the shield (20). The shunt includes: an element made of graphite (40) positioned between the core (10) and the shield (20); and a first and a second metal deposit (51, 52) for providing an electrical and mechanical connection between the element made of graphite (40) and the core (10) and the shield (20), respectively. The invention additionally relates to a coaxial cable and to an electrical device, both including such a coaxial connector (1) and a method for manufacturing such a coaxial connector (1).

Description

COAXIAL CONNECTOR COMPRISING A SHUNT, COAXIAL CABLE AND METHOD OF

MANUFACTURING SUCH A CONNECTOR

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of high current measurements and more particularly relates to shunts and other shunt resistors for such measurements by deriving part of the current.

The invention relates more particularly to a coaxial connector comprising such a shunt, a coaxial cable comprising such a connector and a method of manufacturing a coaxial connector comprising a shunt. STATE OF THE PRIOR ART

In the context of certain measurements involving high current discharges over low times, it is known to use coaxial cables and connectors comprising shunts in order to discharge part of the current to ground. In this way, it is possible to perform these measurements while guaranteeing the protection of the measuring equipment.

It is recalled that in the technical field of high-current measurements, a shunt is, by definition, a resistive element of very low impedance, such as an electrical conductor, allowing the passage from one point to another. an electrical circuit using very little energy. Thus, within the scope of the invention, a shunt is a resistive element making it possible to provide a resistive bridge between a core and a shield of a coaxial connector.

Such coaxial connectors are known and in particular those marketed by T & M RESEARCH PRODUCTS under the reference SDN-414.

Such a coaxial connector comprises:

a conductive soul,

a metal shield surrounding the soul, a dielectric disposed between the core and the shield to electrically isolate them from each other, and

a shunt to provide a resistive bridge between the core and the shield.

This type of connector has the advantage of making it possible to protect certain electrical devices during measurement of intense current over times that can be relatively short, by diverting a portion of the current towards the ground plane. This type of connector thus has good current withstand (greater than 10,000A in nanosecond pulse) for a relatively large bandwidth, since it can reach 2 GHz.

This type of connector nevertheless has a number of disadvantages. Indeed, the shunt that it comprises does not have a constant frequency response and thus has higher resistance for frequencies above 100 MHz. In addition, the integration of the shunt in this type of connector is quite relative, since the volume of the connector is much greater than that of a conventional coaxial connector, and this integration is at the expense of the bandwidth that does not exceed 2 GHz.

STATEMENT OF THE INVENTION

The present invention aims to remedy many of these disadvantages and more precisely aims to provide a coaxial connector comprising a shunt, the shunt having a bandwidth greater than 12 GHz while offering an equivalent current withstand and greater compactness to that of the coaxial connectors of the prior art which comprises a shunt.

To this end, the invention relates to a coaxial connector comprising a shunt, said connector comprising:

a conductive soul,

a metal shield surrounding the soul,

a dielectric disposed between the core and the shield to electrically isolate them from each other, and a shunt to provide a resistive bridge between the core and the shield,

the shunt comprising:

a graphite element positioned between the core and the shield, and

a first and a second metal deposit for providing an electrical and mechanical connection between the graphite element and the core and the shield respectively, each of the first and second metal deposits being an electrolytic deposit.

Such a graphite element allows the shunt to benefit from an optimized bandwidth. Indeed, at high frequency, the current flows on the surface of the conductive materials and this to a thickness corresponding to the skin thickness. Graphite, due to its low electrical conductivity, has a large skin thickness. The graphite element is therefore little influenced by this phenomenon and thus provides a bandwidth greater than 12 Ghz. Moreover, because of this relative importance of its skin thickness, the graphite element makes it possible to obtain a homogeneous shunt behavior over a frequency range from 0 to 12 GHz.

It will be noted moreover that with such a device, the integration of the shunt is optimized since the latter is directly integrated in the coaxial connector. This integration is done without adverse influence on the mechanical strength of the graphite element relative to the rest of the connector and the electrical characteristics of the shunt this due to the use of two metal deposits. In this way, the coaxial connector, with the shunt that it includes, can equip both an electrical device, the connector then being intended to allow connection to a coaxial cable; a coaxial cable, the coaxial connector then being intended to allow connection to an electrical device, or even a coaxial connector.

Each of the first and second metal deposits may be made of a metal selected from the group consisting of copper, silver, gold, nickel, chromium, zinc, tin and lead. Such metals provide a good contact between the graphite element is respectively the core and the shield of the connector.

At least one of the first and second metal deposits may be copper.

Copper is particularly suitable for making it possible to contact the graphite element with the core and the shield respectively because of its good electrical conduction properties and because the core, or even the shielding, is usually made of copper.

At least one of the first and second metal deposits may comprise at least two metal layers, each of the layers being made of a metal selected from the group consisting of copper, silver, gold, nickel, chromium, zinc, tin and lead.

With such metal deposits comprising at least two layers, it is possible to provide a first layer to provide a good conduction, such as a copper layer, between the graphite element and the core and the shield respectively, and second layer to protect the first layer. This second layer may either act as a sacrificial anode, for example being formed of zinc, or act as a protective layer as such, for example being formed of chromium.

The coaxial connector may further include a second protective layer to protect at least one of the first and second metal deposits.

Such a second layer distinct from the first and second metal deposits may limit or even prevent contact of these metal deposits with air or water that could corrode them.

The graphite element may be in the form of a graphite plate sized to fit between the core and the shield.

The graphite element may have a thickness of between 5 and 250 μιη, preferably between 10 and 100 μιη.

Such a graphic element is particularly suitable for presenting a relatively low resistance and to provide a good resistance in current with a relatively high bandwidth, while occupying a low volume compatible with integration into a coaxial connector.

The shield may comprise a metallic connection tip shaped to cooperate with a complementary end of another coaxial connector in a male / female type cooperation,

the graphite element being positioned between the core and the metal tip, the second metal deposit providing an electrical and mechanical connection between the graphite element and the metal tip.

Such a coaxial connector is particularly suitable for allowing the connection of a coaxial cable or allow, when the connector equips a coaxial cable, the connection to an electrical device.

The coaxial connector may be an SMA type connector, the connection tip being a threaded tip.

Such a coaxial connector particularly benefits from having a shunt according to the invention because of its applications which are generally at frequencies above 2 GHz.

The invention also relates to a coaxial cable comprising at least one coaxial connector according to the invention.

Such a coaxial cable makes it possible to benefit from the advantages of the invention regardless of the electrical device to which it is connected.

The invention also relates to an electrical device comprising at least one coaxial connector according to the invention.

Such an electrical device benefits from the advantages associated with the use of a coaxial connector according to the invention.

The invention also relates to a method of manufacturing a coaxial connector comprising a shunt, the method comprising the following steps:

providing a coaxial connector comprising

o a conductive soul,

o shielding surrounding the soul, a dielectric disposed between the core and the shield to isolate them electrically from each other, and

supply of a graphite element,

installation of the graphite element on the coaxial connector positioned between the core and the shield,

forming a first and a second metal deposit to provide an electrical and mechanical connection between the graphite element and the core and the shield respectively, the formation of the first and second metallic deposits being performed by electrolysis.

Such a method allows the manufacture of a coaxial connector enjoying the advantages of the invention.

It can be provided a step of protecting a face of the graphite element by means of a first protective layer, said step of protecting a face of the graphite element being prior to the training step the first and second electro-conductive deposit,

and wherein the step of forming the first and second metal deposition comprises electrolytic deposition between the graphite element and the core and the shield respectively, the face of the graphite element being protected by the first layer.

With such a protective layer, it is possible to perfectly locate the positioning of the first and second metal deposit and thus to define the resistance offered by the graphite element.

It may be further provided a step of depositing a second protective layer to protect the first and second metal deposits.

With such a protective step, it is possible to protect the first and second metal deposits from corrosion.

During the step of supplying the graphite element, the graphite element can be oversized to position itself, and wherein the step of installing the graphite element comprises a sub-step of shear insertion of the graphite element so as to place the latter between the core and the shield with a suitable dimensioning.

Such a shear insertion step makes it possible to obtain a perfectly sized graphite element for placing the latter between the core and the shield.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments, given purely by way of indication and in no way limiting, with reference to the appended drawings in which:

FIGS. 1A and 1B are respectively a sectional view and a front view of a coaxial connector comprising a shunt according to the invention,

FIG. 2 illustrates an electrical device comprising two coaxial connectors according to the invention as illustrated in FIG. 1,

FIG. 3 is a sectional view of a coaxial connector before the placement of a shunt according to the invention,

FIG. 4 illustrates a front view and a sectional view of a graphite element intended for the formation of a shunt for equipping a coaxial connector as illustrated in FIG. 3,

FIGS. 5A and 5B illustrate, in section, the placement of the graphite element illustrated in FIG. 4 on the coaxial connector illustrated in FIG. 3, by shearing the graphite element to perfect its dimensioning. with respect to the coaxial connector,

FIG. 6 illustrates the step of protecting the coaxial connector illustrated in FIG. 4B so as to protect certain parts of the coaxial connector during the placement of metal deposits,

FIG. 7 illustrates the system used to carry out the electrolytic deposits between the graphite element and the rest of the coaxial connector,

FIG. 8 illustrates the coaxial connector illustrated in FIG. 6 after making the electrolytic deposits by means of the system illustrated in FIG. 7, FIG. 9 illustrates a coaxial connector according to a third embodiment according to the invention in which the coaxial connector is of the male type, said coaxial connector equipping a coaxial cable,

Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not being exclusive of each other and can be combined with one another.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 illustrates a coaxial connector 1 comprising a shunt according to the invention.

Such a coaxial connector 1 comprises:

a conductive core,

a metal shield,

a dielectric disposed between the core and the shield to electrically isolate them from each other,

a graphite element 40 disposed between the core and the shield 20, the graphite element 40 having first and second faces, the second face being coated with a first protective layer 42,

the first layer 42 of protection,

a first and a second metal deposit 51, 52 for providing an electrical and mechanical connection between the graphite element 40 and the core 10 and the shield 20 respectively,

a second protective layer 55 for protecting the first and second metal deposits 51, 52. The coaxial connector shown in Figure 1, being a coaxial connector 1 of the female type, the core 10 is provided by a hollow conductor for receiving the end of the core of a male connector. This same coaxial connector 1 is a connector of the SMA type (of the English terminology "SubMiniature version A" and in conformity with the IEC standard), as illustrated in FIG. 3, intended to equip an electrical device, as illustrated. in Figure 2, to allow connection with a coaxial cable comprising a complementary male connector.

Thus, the shield 20 of the coaxial connector 1 comprises a metal connector 21. This connecting end 21 has a substantially planar rectangular base 21A provided with a central orifice, and a hollow revolution cylindrical body 21B extending from the base 21A with its axis of revolution substantially perpendicular to the base 21A. . The base 21A is provided on either side of the central orifice of two peripheral screw passages to allow mounting of the coaxial connector on an electrical device 5.

The cylindrical body 21B extends from the base 21A with the hollow of the cylindrical body which extends the central orifice of the base 21A. In this way, the housing formed by the hollow of the cylindrical body 21B and the central orifice of the base 21A is able to accommodate the dielectric 30 and partially the core 10.

The cylindrical body is provided on the surface of its outer perimeter and opposite the base 21A of a thread. Such threading allows the screwing of the male connector equipping a coaxial cable on the connection tip 21 and therefore the coaxial connector. In this way, the connecting piece 21 is shaped to cooperate with a complementary end of another connector in a male / female type of cooperation.

The dielectric 30 is housed in the connecting piece 21 by interposing between the core 10 and the connecting piece 21. More specifically, the dielectric 30 fills the internal volume of the cylindrical body 21B left free by the core 10 by providing a mechanical support for the core 10. The dielectric 30 has a substantially cylindrical shape of revolution provided with a central passage for housing the core 10. The core 10 is positioned vis-à-vis the dielectric 20 of such way that: the core 10 is flush with the dielectric 20 at the base of the latter which is opposite the base 21A, and

the core 10 protrudes from the dielectric 20 at the base of the latter which is in the extension of the base 21A, such a projection making it possible to connect the core 10 to, for example, a treatment circuit, not shown, the electrical device 5 equipped with said coaxial connector 1.

The dielectric 30 is made of a dielectric material, such as polyethylene or polytetrafluoroethylene, which may be solid or in the form of foam.

The graphite element 40 is as shown in FIG. 4n in the form of a graphite disc provided with a central opening for the passage of the core 10. The graphite element is sized to position itself in the central opening of the base 21A between the base 21A and the core 10. The thickness of the graphite element 40 is between 10 and 100 μιη.

The graphite element 40 has the first circular face, by which it is in contact with the dielectric, and the second face, also circular, which is opposite to the dielectric. The first protective layer 42 covers the second face of the graphite element.

The first layer 42 is made of a dielectric material, such as a dielectric compound based on polymers or elastomers, so as to protect the second face of the graphite element 40 during the deposition of the first and second metal deposits 51, 52. This same first layer 42 has an acid resistance adapted to provide protection of the second face of the graphite element 40 over a period at least equal to the deposition time of the first and second metal deposits, c ' that is, typically from 5 to 6 hours.

Thus, for example, the first layer 42 may be made in the epoxy resin marketed by the company RS components ^® under the reference RS-196-5255 ^® and the English name "Tamper Evident Seal # 196-5245".

It may be noted that, according to a variant of the first embodiment, the graphite element 40 may not have the first protective layer 42. The first and second metal deposits 51, 52 are arranged to interpose between the graphite element 40 and respectively the core 10 and the base 21A. Thus, the first metal deposit 51 is interposed between the graphite element 40 and the core 10 and provides an electrical and mechanical connection between them. Similarly, the second metal deposit 52 is interposed between the graphite element 40 and the base 21A and provides an electrical and mechanical connection between them.

More precisely, as shown in FIG. 1, the first metal deposit 51 at least partially fills the space between the graphite element 40 and the core 10, and the second metal deposit 52 at least partially fills the space between the graphite element 40 and the base 21A and covers a portion of the surface of the base 21A. The portion of the surface of the base 21A is a free portion of the two peripheral screw passages. The first and second metal deposits 51, 52, in this first embodiment, are both made of a metal which is preferably copper because of these conductive properties.

The graphite element 40 and the first and second metal deposits 51, 52 together form a shunt to provide a resistive bridge between the core and the shield. Indeed, the graphite element 40, being disposed between the core 10 and the shield 20, allows to derive a large portion of the current flowing in the core to the shield 20 and therefore to ground plane to which is connected the shielding 20 (in particular by the base 21A which is generally referred to the frame of the electrical device 5).

In order to protect the first and second metal deposits 51, 52 of possible oxidation, the first and second metal deposits 51, 52 are covered by the second layer 55 of protection.

The second layer 55 is a waterproof and airtight layer. This second layer 55 can thus be produced in a compound exhibiting properties of impermeability to water and airtightness based on polymers or elastomers. Thus for example, the second layer 55 may be made in the epoxy resin marketed by the company RS components ^® under the reference RS-159-3957 ^® and the English name "High strength epoxy resin". Such a coaxial connector 1 can therefore, as illustrated in FIG. 2, be installed on an electrical device 5, such as a measuring device. To do this the coaxial connector 1 is introduced into an opening of the frame of the electrical device 5 and referred to the latter by means of the screw passages in the base 21A. The core 10 is then equipped with a cable to connect it to a measuring circuit, not shown. The chassis of such an electrical device 5 forms, in a usual configuration, a ground plane. Thus, the shield 20 is itself connected to the ground of the electrical device 5. In this way, in case of large current discharge over short times, that is to say, for example, 5 kA over a period of 1 ns, a significant portion of the current flowing through the core 10 will be derived by the graphite element 40 in the direction of the ground plane.

Such a coaxial connector 1 can be manufactured by means of a manufacturing method whose main steps are illustrated in FIGS. 3 to 9 and FIG. 1. Such a method comprises the following steps:

supply of a standard coaxial connector 1, such as the SMA female connector illustrated in FIG. 3,

providing the graphite element 40 with its second face coated with the first protective layer 42,

shear insertion, as illustrated in Figures 5A and 5B of the graphite element 40 between the core 10 and the base 21A so that the graphite element 40 is sized to fit between the core 10 and the base 21A, application, as shown in FIG. 6, of a third protective layer 56 on the base 21A at its screw passages so as to protect the parts of the base surface which comprise the screw passages,

forming the first and second metal deposits between the core 10 and the graphite element 40 and between the base 21 and the graphite element 40 so as to ensure the electrical and mechanical connection between the latter, this formation being performed during an electrolytic deposition as illustrated in FIG. 7 by means of an electrolytic solution 125,

neutralization of the electrolytic solution 125 by dipping the connector 1 in a bath of sodium hydroxide in order to neutralize the possible traces of electrolytic solution 125 which could lead to oxidation of the first and second metal deposits 51, 52 and to obtain the coaxial connector 1 as illustrated in FIG. 8,

removal of the third layer 56,

depositing the second protective layer 55 to protect the first and second metal deposits 51, 52 and to obtain the coaxial connector 1 comprising a shunt according to the invention.

In this method, the step of supplying the graphite element 40 can comprise the following sub-steps:

providing a graphite plate whose thickness is between 5 and 250 μιη, or even 10 and 100 μιη, and for example 75 μιη,

applying the first protective layer 42 on one of the faces of the graphite plate,

cutting in the graphite plate a graphite disk with a diameter greater than that of the central orifice of the base 21A,

arranging the central opening in the graphite disk to thereby provide the graphite element 40 provided with the first layer 42, as shown in FIG. 4.

It may be noted that in order to ensure the smooth running of the manufacturing process of the coaxial connector 1, it is preferable that during the step of supplying the standard coaxial connector 1 there is provided a substep of cleaning / degreasing of the connector. Such a substep of cleaning / degreasing of the connector may for example consist in soaking the connector in a phosphoric acid bath for a period of 5min, rinsing it in water, and drying it.

The step of shear insertion of the graphite element 40 between the base 21A and the core 10 can be performed, as shown in Figures 5A and 5B, by means of a tool 100 adapted. This tool 100 comprises a substantially cylindrical body 110 comprising a cylindrical cavity 111 of revolution and a cylinder 120 of revolution of deformable material to exert a homogeneous pressure force on the entire surface of the graphite element, said cylinder 120 being partly housed in the cylindrical cavity 111.

The body 110 is made of a relatively rigid material relative to the cylinder 112, such as for example a thermoplastic elastomer, a metal or wood. The body 110 can thus be made of polyvinyl chloride (better known as PVC). The body 110 is provided with the cylindrical cavity 111 which opens on one of its faces. The cylindrical cavity 111 is extended in the body 110 by a tube 112 making it possible to accommodate a portion of the core 10 during the step of shear insertion of the graphite element 40.

The cylinder 120 has an outer diameter substantially equal to or slightly smaller than the inside diameter of the cylindrical cavity 111 of the body 101 so as to allow its installation in the latter cylindrical cavity 111. This same diameter of the cylinder 120 is preferably equal to or greater than that of the graphite element 40 before its insertion by shear and is strictly greater than or equal to the diameter of the central orifice of the base 21A. The cylinder height 120 is greater than the depth of the cylindrical cavity 111 to allow the deformation of the cylinder 120 during the insertion of the graphite element 40. The height / depth difference between the cylinder 120 and the cylindrical cavity 111 can thus be between 1 and 3 mm, and preferably between 1.25 and 2 mm, this difference can typically be 1.5 mm. The cylinder 120 thus projects from the body 110 of this height / depth difference.

The cylinder 120 is pierced at its center and along its axis of symmetry a passage for the core 10 which is extended by the tube 112 thus ensuring that no stress is applied to the core 10 during insertion by shearing the graphite element 40.

The step of inserting the graphite element 40 with such a tool is carried out by means of the following sub-steps:

installing the graphite element 40 on the coaxial connector 1, the core 10 being inserted into the central opening of the graphite element 40 and the first face being placed on the dielectric 30, placing the tool 100 with the cylinder 120 bearing on the graphite element 40 and the core 10 introduced into the passage of the cylinder 120 and, depending on its length, the tube 112 of the body 110, as shown in Figure 5A

applying a pressing force on the body 120 in a direction from the body to the coaxial connector 1 to cause the cylinder 120 and the dielectric 30 to deform with insertion and shearing of the graphite element 40.

Indeed, during the application of the pressure force, the cylinder 120 has a central portion facing the central orifice of the base 21A, and therefore the dielectric 30, and a peripheral portion facing the base 21A. The base 21A is metallic, it has a relatively high rigidity vis-à-vis the cylinder 120, while the dielectric 30 and the cylinder has an equivalent rigidity. Thus during the application of the pressure force the deformations of the central and peripheral parts will therefore be different. Indeed, as shown in Figure 5A, the peripheral portion will sag to compensate for the displacement of the body towards the coaxial connector while for the central part, the displacement compensation is by a slump distributed on both the cylinder and on the dielectric 30. This results in a relative displacement, and therefore a shear, of the portion of the graphite element 40 disposed on the dielectric 20 relative to the portion of the graphite element 40se disposed on the 21A base.

The graphite element 40 thus sheared and moved inside the central orifice of the base 21A is found inserted between the base 21A and the core 10 with an adjusted dimensioning.

During the step of applying the third protective layer 56 on the base at its screw passages, the protective layer may be made of a dielectric material resistant to acidic media during the electroplating process. and can be made of the same material as that of the first layer 42. for example, the third layer 56 may also be carried out in the epoxy resin sold by RS components ^® company under the RS-196- reference ^® 5245 and the English name "Tamper Evident Seal # 196-5245". The step of forming the first and second metal deposits 51, 52 is carried out by means of, as illustrated in FIG. 7, an electrolysis cell 120 comprising:

a current source 121 for applying a voltage difference,

a first and a second copper electrode 122A, 122B, the first and second electrodes 122A, 122B being connected to the positive terminal of the current source 121, while the core 10 of the coaxial connector 1 is connected to the negative terminal,

a support 123 for supporting the first and second electrodes 122A and 122B and the coaxial connector 1, the support 123 housing the cylindrical body 21B of the connection piece 21 so as to protect the latter and a part of the base 21A during electrolytic deposition,

an electrolytic tank 124 containing the electrolytic solution 125, the latter being a weakly acidic solution (for example 8% acetic acid or boric acid) supersaturated with copper sulphate or copper nitrate.

The training step may thus comprise the following substeps: installation of the coaxial connector 1 and the first and second electrodes on the support 123,

immersion of the support 123 and the elements that it supports in the solution 125,

applying the voltage between the first and second electrodes 122A, 122B and the core 10 by means of the current source 10, so as to effect electroplating to form the first and second metal deposits 51, 52.

Due to the connection of the core 10 to the current source 121, the electrolytic deposition takes place firstly between the core 10 and the graphite element 40 thus making it possible to fill the space between them and to forming the first metal deposit 51. Once the electrical connection between the core 10 and the graphite element 40 established by means of the first deposit, the surface of the graphite element 40 being protected by the first layer 42, the electrolytic deposition takes place from the periphery of the graphite element 40 towards the base 21A. Thus, the electrolytic deposition takes place in a second time between the graphite element 40 and the base 21A to fill the space between them and form the second metal deposit 52. Once the electrical connection between the graphite element 40 and the base 21A established, the copper is also deposited on the surface of the base which is not protected by the third layer 56 and the support 123 thus making it possible to finish forming the second metal deposit 52 .

The copper deposition can be carried out at a constant current of 10 mA for a period ranging from 5 to 6 hours. With such a deposition condition, the voltage supplied by the current source 121 is between 0.3 and 0.4 V.

During the neutralization step, this can be carried out by means of a bath in a 10% sodium hydroxide solution for a period ranging from 12 hours to 72 hours. It may be noted that with a duration of 72 hours, the step of removing the third layer 56 is not necessary. Indeed, such a bath is sufficient to fully remove the epoxy resin of the first and third layers 42 and 56 of protection. It will be noted that this removal of the third protective layer 56 thus makes it possible to release the screw passages from the base 21A and allows a good electrical connection between the shield 20 of the coaxial connector 1 and the ground plane of the electrical device 5. Although Of course, if the removal of the layer 56 is generally necessary, that of the first protective layer 42 does not affect the operation of the coaxial connector 1.

In the case where provision is made for the removal of the third layer 56, the removal step can be carried out either chemically, that is to say by the use of a suitable solvent, or by physical means, that is to say, a scraping operation of the third layer. It may be noted, whatever the route chosen, this operation is facilitated by the prior neutralization step which makes it possible to weaken the third layer 56.

According to the variant of the first embodiment in which the graphite element does not have the first protective layer 42, it can also be provided a step of removing the first layer 42 of the same type as the step of removing the third layer 56. FIG. 9 partially illustrates a coaxial cable 3 according to a second embodiment of the invention. Such a coaxial cable 3 is equipped with a coaxial connector 2 of the male SMA type according to the first embodiment. Such a coaxial connector 2 differs from the coaxial connector 1 according to the first embodiment of not the shape of the connection piece 20 which is a male-type connection piece and by its installation at one end of the coaxial cable 3.

With such an installation of the coaxial connector 2 at the end of the coaxial cable 3, the coaxial connector 2 comprises a core 10 and a dielectric 30 which are common with the coaxial cable 3, and the connection tip 22 is electrically connected to the shielding 23 of the coaxial cable 3 which is itself coated with a dielectric coating 23.

Thus the connection endpiece 22 according to this third embodiment comprises a first cylindrical portion 22A of hollow revolution whose inner diameter is substantially equal to the diameter of the dielectric 30 so as to accommodate a portion. The connection tip 22 also comprises, in the extension of the first cylindrical portion 22A a second cylindrical portion 22B of hollow revolution having an inner diameter greater than that of the first cylindrical portion 22A while being coaxial therewith. The first and the second cylindrical portion 22A, 22B are connected to each other by a shoulder.

The second cylindrical portion 22B has a thread on its inner surface, so as to allow the screwing of the cylindrical body of a complementary coaxial connector. Thus the coaxial connector 2 is shaped to cooperate with a complementary nozzle, such as that illustrated in Figure 1, another coaxial connector in a male / female type of cooperation.

The second cylindrical portion 22B is empty except for the core 10 which protrudes from the first cylindrical portion 22A. The first cylindrical portion 22A houses, in addition to the dielectric 30 and the core 10, the graphite element 40 covered with the first layer 10 of protection. In this way, the graphite element 40 is positioned between the core 10 and the first cylindrical portion 22A. The first and second metal deposits 51, 52 are positioned between the graphite element 40 and respectively the core 10 and the first cylindrical portion 22A.

With such a configuration, it is possible with a single coaxial cable 3 comprising the coaxial connector 2 according to this third embodiment to protect several measuring devices intended to be connected in turn by means of the coaxial cable 3 to a measuring system generating very current pulses on very low times, this benefiting from the integration of the shunt according to the invention.

The manufacturing method of a coaxial connector 2 according to this second embodiment differs from the method of manufacturing a coaxial connector 1 according to the first embodiment of the protection to be provided to the connector 2 during the forming step of the first and second metal deposition 51, 52 and an adaptation of the tool for shear insertion the graphite element which must have a shape complementary to the connection tip 22.

In fact, to ensure conservation of the conformation to cooperate with a complementary endpiece of the end piece, it is necessary for the inner surface of the second cylindrical portion 22B to be protected during the step of forming the first and second metal deposits 51, 52. Such protection can be obtained in the same way as in the first embodiment by means of a layer similar to the third protection layer 56 described above.

Claims

A coaxial connector (1,2) comprising a shunt, said coaxial connector (1,2) comprising:

a conductive core (10),

a metal shield (20) surrounding the core (10),

a dielectric (30) disposed between the core (10) and the shield (20) to electrically isolate them from each other, and

a shunt for providing a resistive bridge between the core (10) and the shield (20),

the coaxial connector (1,2) being characterized in that the shunt comprises:

a graphite element (40) positioned between the core (10) and the shield (20), and

a first and a second metal deposit (51, 52) for providing an electrical and mechanical connection between the graphite element (40) and the core (10) and the shield (20), each of the first and second deposits metal (51, 52) being an electrolytic deposit. 2. Coaxial connector (1,

2) according to claim 1, wherein each of the first and second metal deposits (51, 52) is made of a metal selected from the group consisting of copper, silver, gold, nickel, chromium, nickel, zinc, tin and lead.

The coaxial connector (1, 2) according to claim 1 or 2, wherein at least one of the first and second metal deposits (51, 52) is made of copper.

The coaxial connector (1, 2) according to claim 1, wherein at least one of the first and second metal deposits (51, 52) comprises at least two layers of metal, each of the layers being made of a metal selected from the group consisting of copper, silver, gold, nickel, chromium, zinc, tin and lead.

The coaxial connector (1, 2) according to any of claims 1 to 4 further comprising a second protective layer (55) for protecting at least one of the first and second metal deposits.

The coaxial connector (1,2) according to any one of claims 1 to 5, wherein the graphite element (40) is in the form of a graphite plate sized to fit between the core ( 10) and the shield (20).

7. coaxial connector (1,2) according to claim 5, wherein the graphite element (40) has a thickness between 5 and 250 μιη, preferably between 10 and 100 μιη.

8. coaxial connector (1,2) according to any one of claims 1 to 7, wherein the shield (20) comprises a connecting piece (21, 22) metal shaped to cooperate with a complementary end of another connector coaxial according to a cooperation of the male / female type,

and wherein the graphite element (40) is positioned between the core

(10) and the metal tip (21, 22), the second metal deposit providing an electrical and mechanical connection between the graphite member (40) and the metal tip (21, 22).

The coaxial connector (1, 2) according to any one of claims 1 to 7, wherein the coaxial connector (1, 2) is an SMA type connector, the connection tip (21) being a threaded tip.

10. Coaxial cable (3) characterized in that it comprises at least one coaxial connector (2) according to any one of claims 1 to 8.

11. Electrical device (5) characterized in that it comprises at least one coaxial connector (1) according to any one of claims 1 to 8.

A method of manufacturing a coaxial connector (1,2) comprising a shunt, the method comprising the steps of:

providing a coaxial connector (1,2) comprising a conductive core (10),

a shield (20) surrounding the core (10),

a dielectric (30) disposed between the core (10) and the shield (30) for electrically isolating them from each other, and

providing a graphite element (40),

installing the graphite element (40) on the coaxial connector (1, 2) positioned between the core (10) and the shield (20),

forming a first and a second metal deposit (51, 52) to provide an electrical and mechanical connection between the graphite element

(40) and respectively the core (10) and the shield (20), the formation of the first and second metal deposit being achieved by electrolysis.

13. The manufacturing method according to claim 10, wherein there is provided a step of protecting a face of the graphite element (40) by means of a first layer (42) of protection, said step of protection of one face of the graphite element (40) being prior to the step of forming the first and second electroconductive deposition (51, 52),

and wherein the step of forming the first and second metal deposition (51, 52) comprises electrolytic deposition between the graphite element (40) and the core (10) and the shield (20), the face the graphite element (40) being protected by the first layer (42).

14. The manufacturing method according to claim 12 or 13, wherein there is further provided a step of depositing a second layer (55) of protection to protect the first and second metal deposits (51, 52).

15. Manufacturing method according to any one of claims 12 to 14, wherein during the step of supplying the graphite element (40), the graphite element (40) is oversized to position itself,

and wherein the step of installing the graphite element (40) comprises a sub-step of shear insertion of the graphite element so as to place the graphite element between the core (10) and the shield ( 20) with a suitable dimensioning.