Transition Device Between Coaxial And Microstrip Lines

Abstract

A conversion device for an ultra-high frequency coaxial line and a metal strip without welding comprises a brass support body in which a base plate, held tight by screws forces the metal strip against the central conductor and a plate spring to ensure an electrical contact between the ground wires of the two lines along a particularly short path free from stationary waves.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns transitions employed at ultra-high frequencies between a coaxial line and a dielectric microstrip line, allowing a connection to be detached and restored at will.

2. Description of the Prior Art

In known devices of this kind, a casing is specially constructed for this purpose. Holes are first made in the dielectric plate to receive screws and the plate is then locked to the casing by nuts fitted on these screws. It is thereby possible to make the electrical connection between the earth plate of the microstrip line and the casing itself, which is assembled with the coaxial connector by its end member, which is in turn connected to the external sheathing of the coaxial line. Thereafter, in order to make the connection between the central conductor of the coaxial line and the microstrip line, a joint is necessary. Such devices require specially made matchings, which can be used only once. This fixing and matching work is particularly lengthy, especially as it is necessary at ultra-high frequencies to determine characteristics which are variable as a function of frequency, such as the standing wave ratios and the insertion losses, which determine the behavior of any adapter.

SUMMARY OF THE INVENTION

The device according to the invention obviates these disadvantages, since it is possible to obtain a transition which ensures a good performance and which is simply and universally fitted for any dimension of the dielectric plate and the connection is made without any soldering.

The device according to the invention comprises an ultra-high frequency transition between a coaxial line and a microstrip line and consists of a dielectric plate having on a first face an earth metallization and on the second face a conductive strip. The device has the object of making a "primary" connection between the axial conductor of the coaxial line and the conductive strip and a "secondary" connection between the external conductor of the coaxial line and the ground metallization. It comprises a plug-type connector adapted to receive the end of the coaxial line and is provided with a plug which is connected by its "forward" part to the axial conductor of the coaxial line and a metallic end member connected to the external conductor of the coaxial line. It is characterized by the fact that it also comprises a conductive support on which the plug-type connector is mounted so as to establish electrical contact between the end member and the support. The plug extends through the support without contact therewith, while its "rear" end projects from the support. A base plate adapted to move perpendicularly to the said plug is pressed against the first face of the plate by gripping means so that the second face of the plate bears, by way of the conductive strip, against the plug. This establishes the "primary" connection by simple juxtaposition by means of a member which establishes an electrical contact between the support and the base plate, and establishes the "secondary" connection along a short electrical path which avoids as far as possible the creation of standing waves.

In accordance with one embodiment of the invention, the support has a right-angled arrangement and the base plate is provided with two arms surrounding one of the branches of the right angle. The two arms extend towards one another at their ends to a distance which is smaller than the width of the support, so as to prevent the plate from moving away from the branches.

In accordance with another embodiment of the invention, the gripping means comprise locking screws extending through the screw-threaded holes in the support and urge the second face of the plate, without electrical contact, against abutments forming part of the support.

In accordance with another embodiment of the invention, the member which establishes electrical contact is a spring lamina secured to the face of the base plate which comes into contact with the first face of the plate; the lamina exterting a pressure on the support in a direction parallel to the plug.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the diagrammatic figures, there will be described, in the following, an example of the application of the present invention, which is given purely by way of illustration and has no limiting character. The elements illustrated in more than one of these figures bear the same reference numerals in each figure.

FIG. 1 is an exploded perspective view of the transition device with its coaxial connector, its support body, its base plate and its spring.

FIG. 2 is a general perspective view of the transition device mounted on a microstrip line.

FIG. 3 is a section through the transition device of FIG. 2 in a plane perpendicular to the plate of the microstrip line.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There will be seen in FIG. 1 a spring lamina 1 which may consist of beryllium bronze, which is permanently welded to a base plate 2, which is provided with two arms into which there are adapted to be screwed two rods 3 and 4, which have the function of securing the base plate 2 on the support body 5. The support body, like the base plate, consists of brass or the like. By way of example, the overall dimensions of the support body are 3 .times. 1.8 .times. 1 cm. The base plate bears, through the intermediary of its spring 1, on one of the walls of the support body 5 and rests on the screws 6 and 7 extending through another wall, which is perpendicular to the first. Two abutments 8 and 9 project from the support body 5 to stop the travel of the screws 6 and 7. An end member 10 comprises a truncated plate and supporting a coaxial connector 11, for example of the type R 29 330, marketed under the trade name RADIALL, is secured to the support body 5 by two screws 12 and 13.

The core of the central conductor of the coaxial connector 11 emerges, in the form of a flattened rigid rod 14, through the central orifice 15 in the support body 5. The rigid rod 14 does not come into contact with the support body 5.

In FIG. 2, there is seen a dielectric plate of a microstrip line 16 introduced between the base plate 2 and the abutments 8 and 9 of the support body 5. The plate has a face 17 supporting conductive strips and a metallized face 18 (ground).

In FIG. 3, it will clearly be seen that the base plate 2 is pressed by the screws 6 and 7 against the dielectric plate of the microstrip line 16, which is stopped by the abutments 8 and 9. There is thereby ensured a contact between the rigid rod 14 and the introduced portion of a conductive strip disposed on the face 17 of the dielectric plate of the microstrip line. It will be observed that, regardless of the thickness of the dielectric plate 16, the spring lamina 1 exerts a pressure on one of the walls of the support body 5. Contact is thus ensured between the body of the support and the spring lamina 1.

Electrically, the ground return is effected from the ground 18 of the microstrip line to the external sheathing of the coaxial line along the following path: surface of the spring lamina 1, support body 5 and end member 10. At ultra-high frequencies, this is a short path because its length does not exceed 5 mm., i. e. one-thirtieth of the wavelength of 2,000 Mc/s. As is known, the discontinuity becaomes considerable only at lengths of more than .lambda. /8. This would be the case with an electrical path extending through the screws 6 and 7 if the spring lamina were not present.

Up to 10 Gc/s, the standing wave ratio is lower than 1.1:1, while the insertion losses are negligible.

Although the device just described appears to be the most advantageous for the application of the invention, it will be appreciated that various modifications may be made therein without departing from the scope of the invention, while some of its elements may be replaced by other elements capable of performing the same technical function.

The device according to the invention may be employed in all cases where any dielectric microstrip line is to be joined to a coaxial line.

Particularly interesting applications are to be found in the field of ultra-high frequency connections.

Claims

What is claimed is:

1. In an ultra-high frequency transition device coupling a coaxial line and a microstrip line consisting of a dielectric plate having on a first face a ground and on the second face a conductive strip, and wherein the device makes a primary connection between the axial conductor of the coaxial line and the conductive strip and a secondary connection between the external conductor of the coaxial line and the ground, and said device comprising a plug-type connector adapted to receive the end of said coaxial line and provided with a central conductor which is connected by a forward part to the axial conductor of the coaxial line, and a metallic end member connected to the external conductor of the coaxial line, and also comprising a conductive support on which the plug-type connector is mounted so as to establish electrical contact between the end member and the said support, said central conductor extending through said support without contact therewith, while its rear end projects from the said support; the improvement comprising: a base plate movably connected to said support so as to be displaceable perpendicular to the axis of said central conductor, a first face of the said base plate being pressed against the first face of the said dielectric plate by means bearing on said support, the said second face of the said dielectric plate bearing by way of the said conductive strip against said central conductor to establish said primary connection by simple juxtaposition, and a flexible connecting member establishing an electrical contact between said support and said ground to establish said secondary connection along a short electrical path which avoids as far as possible the creation of standing waves.

2. The device according to claim 1, wherein: said support comprises a right-angled arrangement with the base plate provided with two arms surrounding a first branch of the right-angle, and locking means carried by said two arms at their ends and extending towards one another to define a distance which is smaller than the width of the support to prevent the plate from separating from said first branch.

3. The device according to claim 2, characterized in that the said arms carry two screwthreaded rods in their ends movable towards one another.

4. The device according to claim 2, wherein said base plate bearing means bear between the second face of said base plate, and the second branch of said right-angled member, said first branch of the right-angled member carries on either side of the said conductive strip two abutments, whereby said bearing means urges said second face of the said dielectric plate against said abutments without electrical contact.

5. The device according to claim 2, wherein said flexible conducting member establishing electrical contact is a metallic spring lamina fixed on said first face of the base plate, and exerts a pressure on said support in a direction parallel to the axis of said plug which tends to move said base plate away from said first branch of the right-angled member.

6. The device according to claim 3, wherein said base plate bearing means bear between the second face of said base plate and the second branch of said right-angled member, said first branch of the right-angled member carries on either side of the said conductive strip two abutments, whereby said locking means urges said second face of the said plate against said abutments without electrical contact.

7. The device according to claim 3, wherein said flexible conducting member establishing electrical contact is a metallic spring lamina fixed on said first face of the base plate, and exerts a pressure on said support in a direction parallel to the axis of said central conductor which tends to move said base plate away from said first branch of the right-angled member.

8. The device according to claim 4, wherein said flexible conducting member establishing electrical contact is a metallic spring lamina fixed on said first face of the base plate, and exerts a pressure on said support in a direction parallel to the axis of said central conductor which tends to move said base plate away from said first branch of the right-angled member.