EP0708503A1 - Multiways electrical connector without electromagnetic shielding between the tracks - Google Patents

Abstract

The multichannel electrical connector includes a coaxial connection for each channel. This comprises a central conductor (7) and an outer conducting sleeve (10). The conducting rods (7) are situated within a box (3, 12) which consists of an L-shaped base (3) and a cover (12). The conducting rods are right-angled elements each with a section directed downwards to stand perpendicular to the printed circuit board (9) and a horizontal section (8) extending into a connector (9). The cover (12) of the box provides two earth planes (13,14) in its large surfaces and these are closer to the conducting rods than the conducting rods are to each other.

Description

The present invention relates to a multi-channel electrical connector without an electromagnetic barrier between the channels.

Miniature electrical connectors with several channels are already known, each channel being constituted by a coaxial contact element comprising a central conductor and an external conductor, means for connection to a printed circuit board and an electrically conductive rod connecting the central conductor of the contact element coaxial with said connection means.

In these known connectors, the conductive rods of the different channels are separated in pairs by a conductive partition which has the function of isolating them from the electromagnetic point of view to avoid any coupling between the signals carried by two neighboring rods.

Such connectors are generally satisfactory but they have a number of drawbacks.

In particular, their manufacture poses a problem because the partitions which separate the different conductive rods define channels inside the connector and that it is difficult, especially when the connector is bent, to introduce the conductive rods to the inside these channels.

In addition, the production of such partitions implies a relatively high cost price of the connectors.

In addition, these partitions constitute an obstacle to the miniaturization of the connector, which must necessarily comprise n − 1 partitions for n rods, hence a certain bulk.

The present invention aims to provide a multi-channel electrical connector which in particular does not have the drawbacks mentioned above.

The present invention relates to a multi-way electrical connector, in which each channel is constituted by a coaxial contact element comprising a central conductor and an external conductor, means for connection to a printed circuit board and an electrically conductive rod connecting the conductor central of the contact element coaxial with said connection means, characterized in that the conductive rods are housed in a housing which defines a continuous interior space, each conductive rod being arranged near at least one ground plane and being separated from the neighboring conductive rod (s) by a distance greater than the distance which separates it from its ground plane.

Thus, most of the electromagnetic radiation from each conductive rod is captured by the ground plane before reaching the neighboring conductive rod or rods.

It is understood that the connector according to the invention has the advantage of being able to be miniaturized in large proportions while being of a relatively low cost price.

In a preferred embodiment of the invention, the conductive rods are housed in a dielectric medium whose dielectric constant is determined so that, taking into account the diameter of each rod and the distance which separates this rod from its plane or planes mass, the impedance of each channel has a desired value.

In a variant of this embodiment, the connector comprises a second dielectric medium of different dielectric constant which separates the first dielectric medium from the ground plane (s).

For example, the conductive rods can be placed in a first dielectric medium consisting of air and bear against a layer of plastic material applied to the ground plane, this layer of plastic material constituting a second dielectric medium.

According to the invention, the housing is preferably made of an electrically conductive material and plays the role of shielding from the outside.

In a first embodiment of the invention, there is provided a single ground plane preferably formed by a wall of the housing, and in the vicinity of which the conductive rods are arranged.

In a second embodiment of the invention, two parallel ground planes are provided, preferably constituted by two walls of the housing and between which the conductive rods are arranged.

• la figure 1 est une vue en perspective d'un connecteur selon un premier mode de réalisation de l'invention,
• la figure 2 est une vue en coupe selon II-II de la figure 1,
• la figure 3 est une vue analogue à la figure 2 d'un connecteur selon un deuxième mode de réalisation de l'invention,
• la figure 4 est une vue en perspective d'un connecteur selon un troisième mode de réalisation de l'invention à l'état démonté, et
• la figure 5 est une vue en coupe selon V-V de la figure 4 du connecteur à l'état monté.

In order to better understand the invention, we will now describe three embodiments given by way of non-limiting examples, with reference to the accompanying drawing in which:

• FIG. 1 is a perspective view of a connector according to a first embodiment of the invention,
• FIG. 2 is a sectional view along II-II of FIG. 1,
• FIG. 3 is a view similar to FIG. 2 of a connector according to a second embodiment of the invention,
• FIG. 4 is a perspective view of a connector according to a third embodiment of the invention in the disassembled state, and
• Figure 5 is a sectional view along VV of Figure 4 of the connector in the assembled state.

In the drawing, there is shown a printed circuit board 1 on which is mounted a connector 2 comprising a metal support 3 in the shape of an L, the lower branch 4 of which is secured to the plate 1 and has holes 5 provided with insulating sheaths 6 through which the ends of two bent conductive rods 7 engage.

The metal support 3 and the ends of the conductive rods 7 are fixed to the printed circuit board 1 by conventional means, in particular by welding.

Each conductive rod 7 is connected to the central conductor 8 of a coaxial contact element 9 whose external conductor 10 is welded to the upper branch 11 of the metal support 3.

A metal cover 12 of parallelepiped shape, having an open bottom and front face, is removably mounted on the metal support 3 by fixing means, not shown, to constitute a housing within the meaning of the invention.

This housing defines a continuous interior space in which the two conductive rods 7 are housed.

As seen in the sectional view of Figure 2, the two large faces 13,14 of the cover 12 constitute parallel ground planes separated by a distance L = 1.1 mm.

The two conductive rods 7 are placed between these two ground planes. The outside diameter d = 0.6 mm of each conductive rod 7 and the dielectric constant K = 1 of the air, which here constitutes the only dielectric medium in which the conductive rods are placed, make it possible to determine the impedance Z of each line by applying the following approximate formula: $${\text{Z = 60 / <figure-callout id="1" label="K" filenames="imgf0001.png" state="{{state}}">K</figure-callout>}}^{\text{1/2}}\text{ln (4L / π d) ≅ 50 Ω}$$

The conductive rods 7 are spaced from each other by a distance D equal to 4 mm.

Thus, for alternating signals of frequency between approximately 100 MHz and 18 GHz, and of power between approximately 0.1 and 10 W, one observes a coupling between the channels of less than 30 dB, which can be considered as negligible .

In the embodiment shown in Figure 3, the conductive rods 7 are located near one of the walls 14 of the metal cover.

The distance between the conductive rods 7 of the other wall 13 of the metal cover is large enough that the influence on the conductive rods 7 of this other wall 13 can be considered negligible, or even zero, from the electromagnetic point of view.

However, the cover 12 fulfills a shielding function vis-à-vis the outside, as in the previous embodiment.

In this embodiment of Figure 3, there is provided, in addition to the air gap of dielectric constant K1 = 1 in which are placed the conductive rods 7, a second dielectric material 15 consisting of a layer of PTFE (polytetrafluoroethylene ), whose dielectric constant K2 is 2.

If the distance L ' which separates the axis of each conductive rod from the ground plane is approximately 0.5 mm, the impedance Z of each electrical line is approximately 50 Ω:

In this embodiment, the conductive rods are separated by a distance D '= 4 mm.

In this case, for signals whose power is at most 10 W, and whose frequency is between 100 MHz and 18 GHz, a coupling between the channels is observed below 30 dB, which can be considered negligible.

It may also be noted that the second dielectric medium 15 provides an advantage concerning the manufacture of the housing 12 by constituting a shim which makes it possible to position the conductive rods 7 at a desired distance from the ground plane 14 by applying them against this layer 15.

In the third embodiment, shown in FIGS. 4 and 5, the connector 2 ′ comprises a metal housing 3 ′ which has, in a plane parallel to the printed circuit 1, a U-shaped section visible in FIG. 5.

In its front part 16, which forms the base of the U in FIG. 5, the housing 3 'is full and has two bores 17 in which the external conductors 10 engage, which are welded or force-fitted into the bores 17.

In its rear part 18, which forms the two branches of the U in FIG. 5, the housing 3 'has two parallel flat walls 13', 14 '.

The rear end 19 of the housing 3 'is open.

The two conductive rods 7 are overmolded in a block of dielectric material 15 ′ made for example of polyimide.

The dimensions of the block 15 'correspond substantially to the internal dimensions of the space between the walls 13' and 14 'of the housing 3'.

The block 15 'is intended to be inserted into the housing 3' between its two parallel walls 13 'and 14', as seen in FIG. 5.

Each conductive rod 7 engages inside the corresponding external conductor 10 and its end 8 'directed towards the front part 18 of the housing constitutes the central conductor of a coaxial contact 9' thus produced.

Once the block 15 ′ is inserted into the housing 3 ′, the rear face 19 of the housing can be closed off by an electrically conductive plate, not shown, intended to constitute an electromagnetic shield against the exterior of the housing.

It is understood that the embodiments which have just been described have no limiting character and that they can receive any desirable modifications without departing from the scope of the invention.

Claims (7)

Multichannel electrical connector, each channel being constituted by a coaxial contact element comprising a central conductor and an external conductor, means for connection to a printed circuit board and an electrically conductive rod connecting the central conductor of the coaxial contact element to said connection means, characterized in that the conductive rods (7) are housed in a housing (3.12; 3 ') which defines a continuous interior space, each conductive rod (7) being arranged near at least one ground plane (13,14; 13 ', 14') and being separated from the neighboring conductive rod (s) by a distance (D, D ') greater than the distance which separates it from its ground plane (13,14 ; 13 ', 14'). Connector according to claim 1, characterized in that the conductive rods (7) are housed in a dielectric medium whose dielectric constant ( K1 ) is determined so that, taking into account the diameter ( d ) of each rod (7) and of the distance which separates this rod (7) from the ground plane (s) (13,14; 13 ', 14'), the impedance ( Z ) of each channel has a desired value. Connector according to claim 2, characterized in that it comprises a second dielectric medium of different dielectric constant ( K2 ), which separates the first dielectric medium from the ground plane (s) (14). Connector according to any one of claims to 3, characterized in that the housing (3,12; 3 ') has a single ground plane (14) in the vicinity of which the conductive rods (7) are arranged. Connector according to any one of claims 1 to 3, characterized in that the housing (3,12; 3 ') has two parallel ground planes (13,14) between which the conductive rods (7) are arranged. Connector according to claim 5, characterized in that the conductive rods (7) are overmolded in a block of dielectric material (15 ') inserted in the housing (3'). Connector according to claim 6, characterized in that the end (8 ') of a conductive rod (7) directed towards the corresponding coaxial contact element (9 ′) constitutes the central conductor of this coaxial contact element.

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