GB2325096A - Coaxial connector - Google Patents

Abstract

A coaxial connector (10) for rf applications comprises a C-shaped spring (12) of high strength spring material which forms a high force spring contact when press fitted with the mating component (20). A similar tapered female connector is also described (Figure 5).

Description

DESCRIPTION TAPERED-C PRESS FIT CONTACT SYSTEM The present invention relates generally to connectors.

More particularly the present invention relates to high performance coaxial connectors for radio frequency applications.

For radio frequency applications, high performance coaxial connectors often must be made from high strength spring materials. The contacts for the center and outer conductors especially often must be constructed of high strength spring materials. Such use of high strength spring materials, however, frequently results in increased materials cost, which can be a significant problem in constructing larger components.

To reduce materials cost, often a two-piece contact system is used, having high strength spring materials in the critical areas, that is, the areas closely associated with achieving the connection, and low strength materials for the rest of the connector.

The disadvantage of such two-piece systems in the past has been an additional assembly operation that the two pieces require, such as soldering or threading and applying a thread locking compound. However, soldering, threading and thread locking are highly variable processes which are difficult to automate. Moreover, they often increase assembly costs and have an adverse impact on product reliability and performance. Specifically, such traditional assembly processes for two piece systems often result in problems such as cold solder joints; insufficient solder, excess solder, insufficient thread locking compound, or excess thread locking compound which causes loss of electrical continuity.

A need continues to exist for improved high performance coaxial connectors.

I have discovered a coaxial connector for radio frequency applications and a method for obtaining a radio frequency connection that offers lower cost and higher performance and reliability than traditional connectors and methods. In my invention, a tapered C-shaped spring is pressed fitted :3to a mating component (or the mating component is press fitted into a tapered C-shaped spring) such that maximum contact pressure occurs near the interface surfaces of the spring and the mating component.

Degradation of return loss performance is thereby minimized.

The spring has a C-shaped cross-section.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 depicts a side view of the C-shaped spring and mating components of the coaxial connector of this invention.

Fig. 2 depicts an end view of the C-shaped spring of Fig. 1.

Fig. 3 depicts the components of Fig. 1 after assembly.

Figure 4 depicts a cross-sectional view of the tapered-C press fit contact of the assembly of Fig. 3.

Fig. 5 depicts an alternative view of the tapered-C spring and mating components of the coaxial connector of this invention.

The coaxial connector of this invention offers faster assembly, improved performance, and improved reliability when compared to coaxial connectors known in the art for radio frequency applications. The advantages of this invention are achieved through a tapered-C press fit contact system.

Referring to Figure 1, for example, a coaxial connector 10 has a section 12 comprised of high strength spring material, such as beryllium copper. Any material with electrical properties suitable for the purposes of the coaxial connector that has sufficient strength to have spring-like qualities may be used for section 12. Usually, non-magnetic spring materials are preferred to avoid magnetic interference with electrical performance and intermodulation distortion. Section 12 is tubular or cylindrical in shape, with a hollow interior and one slot 14, which results in the section 12 being C-shaped, as shown in Figure 2.

The front end of coaxial connector 10, end section 16, is shown in Figure 1 for example with four slots, but it may have other various appearances depending on the application of the connector. This part of the coaxial connector is not critical to this invention.

Section 12, which may also be viewed as a C-shaped compliant pin or spring, prod ices a tapered, or gradually increasing, spring force when inserted into the mating component 20, as shown in Figures 3 and 4. Section 12 thus makes a high force spring contact when fitted into mating component 20. Maximum contact pressure occurs at points 11 and 21 at or near interface surfaces of the two components 12 and 20, as shown in Figure 4, which minimizes any discontinuity to the current flow on the surface of the conductor, and thereby minimizes any degradation of return loss performance. This tapered-C press fit contact is solid, and stable, thereby minimizing intermodulation distortion which can be caused by nonlinear effects such as changes in either contact resistance or in the physical point of contact.

These features of the coaxial connector of this invention are a significant improvement over prior art, and particularly a significant improvement over prior art coaxial connectors employing traditional assembly methods. The main contact point in prior art devices typically occurs down inside a solder cup or a threaded hole, instead of at the interface, resulting in less than optimum and often degraded return loss performance. Traditional assembly methods also may allow environmental forces to cause the interface surfaces of prior art devices to open and close thereby generating intermodulation distortion.

An altemative embodiment of this invention is shown in Figure 5. In this embodiment, the tapered-C shaped spring 30 is the female part of the coaxial connector, instead of the male part of the connector, and the mating component 32 is the male component. The taper of spring 30 is formed by swaging the contact closed near the front of the spring at points 31 and 33. The principles of this invention discussed for the male embodiment of the tapered-C shaped spring remain the same for the female version.

The principle of the invention and the best mode contemplated for applying that principle have been described. It is to be understood that the foregoing is illustrative only and that other means and techniques can be employed without departing from the true scope of the invention defined in the following claims.

Claims (23)

1. A connector for making an electrical connection with a surface of a conductor for carrying radio frequency signals, said connector comprising a generally tubular end section having an end, the end section including a single slit extending longitudinally from said end along said end section so as to form a C-shaped spring, said spring being resiliently deformable for a tapered spring force press fit against the surface of the conductor for carrying radio frequency signals.

2. A connector as claimed in claim 1, in which the C-shaped spring is comprised of high strength spring materials.

3. A connector as claimed in claim 2, in which the C-shaped spring is comprised of a beryllium copper alloy.

4. A connector as claimed in any one of the preceding claims, in which the generally tubular end section is tapered so that the smallest diameter along the end section is at the end.

5. A connector as claimed in any one of the preceding claims, in which the generally tubular end section is not tapered prior to being inserted into said hollow conductor.

6. A connector as claimed in any one of the preceding claims, in which the connector makes an electrical connection with an inside surface of a hollow generally tubular conductor and the tapered force spring press fit is against the inside surface of the hollow conductor.

7. A connector as claimed in any one of claims 1 to 5, in which the connector makes an electrical connection with an outside surface of a generally tubular conductor and the tapered force spring press fit is against the outside surface of the conductor.

8. A connector assembly for carrying radio frequency signals comprising: a connector comprising a generally tubular end section, the end section including an end and having a generally circular cross section, said end section including a single slit extending from said end longitudinally along said end section so as to form a C-shaped spring; a hollow conductor for carrying radio frequency signals, said conductor having an inside surface, said C-shaped spring fitting resiliently inside said hollow conductor and being tapered such that maximum contact pressure between said inside surface and said spring occurs at a generally annular contact area furthest away from said end.

9. A connector assembly as claimed in claim 8, in which the spring is comprised of high strength spring material and said conductor is comprised of low strength material.

10. A connector assembly as claimed in claim 9, in which the spring is comprised of a beryllium copper alloy and said conductor is comprised of brass or phosphor bronze.

11. A connector assembly as claimed in any one of claims 8 to 10, in which the connector is a part of a coaxial connector and the hollow conductor is part of a coaxial cable.

12. A coaxial connector inner-conductor assembly for carrying radio frequency signals said assembly comprising: a coaxial cable having a hollow inner conductor, the inside surfaces of said hollow inner conductor being generally tubular; a connector having a generally tubular end section, said end section including an end, said end section including a slit extending longitudinally from said end along said end section so as to form a C-shaped spring, said Cshaped spring fitting resiliently inside said hollow inner conductor, the inside surface of said inner conductor resiliently deforming the C-shaped spring to taper it, the contact pressure between said inside surface and said C-shaped spring being at maximum along the annular contact area furthest away from said end.

13. A connector for making an electrical contact with a surface of a conductor, said connector comprising: a generally tubular tapered end section, the end section including an end and a single slit extending longitudinally from said end along said tapered tubular end section to form a tapered C-shaped spring for a press fit against the surface of the conductor.

14. A connector as claimed in claim 13, in which the connector is a coaxial connector.

15. A connector as claimed in claim 13 or 14, in which the end section has an outer surface and wherein said outer surface is tapered and wherein said outer surface is for a press fit against an inside surface of a hollow conductor.

16. A connector as claimed in claim 13 or 14, in which the end section has an inner surface and wherein said inner surface is tapered and wherein said inner surface is for a press fit against an outside surface of a conductor.

17. A method for making a radio frequency connection to a hollow conductor for carrying radio frequency signals, said hollow conductor having an inside surface, said method comprising the following steps: inserting into said hollow conductor a C-shaped spring, until said spring is press-fitted in said hollow conductor, said C-shaped spring formed in tubular end section of a connector by a single longitudinal slit extending longitudinally from said end along said tubular section such that maximum contact pressure occurs near the interface surfaces of the spring and the mating component, said C-shaped spring being tapered by the inside surface of said conductor so that the maximum contact pressure between said C-shaped tapered spring and said inside surface occurs at a generally annular contact area furthest away from said end.

18. A method as claimed in claim 17, in which the hollow conductor is a part of a coaxial connector.

19. A method for making a radio frequency connection to a conductor for carrying radio frequency signals, said conductor having an outside surface, said method comprising the following steps: inserting onto said conductor a tapered C-shaped spring, until said spring is press-fitted on the outside surface of the conductor, said C-shaped spring formed in tubular end section of a connector by a single longitudinal slit extending longitudinally from said end along said tubular section such that maximum contact pressure between the outer surface and the spring occurs at the generally annular contact area at the end of the tubular end section.

20. A coaxial connector-conductor assembly for carrying radio frequency signals, said assembly comprising: a coaxial cable having an inner conductor, said inner conductor having an outside surface, the outside surface of said inner conductor having a generally circular cross-section; a connector having a generally tubular end section, said end section including an end, said end section including a slit extending longitudinally from said end along said end section so as to form a C-shaped spring, said Cshaped spring press fitted against the outside surface of said inner conductor, the contact pressure between said outer surface and said C-shaped spring being at maximum along said end.

21. A connector substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

22. A method for making a radio frequency connection substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

23. A coaxial connector-conductor assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.