EP0596313A2

EP0596313A2 - Connector element for a high frequency transmission path

Info

Publication number: EP0596313A2
Application number: EP93116836A
Authority: EP
Inventors: Dirk 3M Laboratories Heinrich (Europe)Gmbh
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1992-11-02
Filing date: 1993-10-19
Publication date: 1994-05-11
Also published as: DE4236945A1; EP0596313A3; KR940012709A; JPH06215819A

Abstract

A connector element for a high frequency transmission path which includes at least a pair of spaced conductor portions defining a signal and ground conductors. The conductor portions are retained by a dielectric retaining body. A part of the conductor portions has opposite surface portions having a space varying from that of the adjacent parts of the conductor portions to change the capacitance and thus the impedance of the connector element portion in the retaining body.

Description

The invention refers to a connector for a high frequency transmission path.

PRIOR ART

From the European patent application EP O 362 841 it has become known to connect a multiplicity of coaxial cables with a printed circuit board (PCB). The PCB has an array of contact pins onto which coaxial receptacles of coaxial cables are plugged. Usually, a coaxial cable has a predetermined impedance. The PCB usually is matched to this impedance, too. This is also valid for a connection of a contact pin with a receptacle.
From the US patent No. 4,995,815, the French patent No. 2,552,939 and the British patent No. 2,252, 578 is has become known to connect coaxial cables with a PCB extending parallel to the PCB through a connector element. For this purpose, the signal wire in the connector element is encircled more or less by a shielding which in turn is connected with the shielding of the coaxial cable and the mass conductor of the PCB. Due to the geometrical configuration of coaxial cable and PCB it is mandatory to bend the signal conductor in the connector element about 90^0. The screening of the signal wire portion inserted into the PCB is achieved by a plurality of pins located around the signal wire which are also inserted into the PCB. By means of such a connector element, an approximate impedance matching is accomplished for the connector elements. However, the manufacture of such connector elements is relatively expensive.
From the prospectus "Control Impedance of 50 Ohms in only 1/28 the Space" of "Chabin Transmission Line Applications 3 Electronic Products Division" dated January 1, 1988 it has become known to provide connectors for a coaxial cable wherein the signal and the mass conductors are not coaxially arranged, rather, are located in parallel and are enclosed by an electrically conductive housing. If such connectors are connected to a PCB, a mismatching may occur, particularly if for example contact pins on the PCB are not completely received by the female connector part, rather, a space is left between connector and PCB. Above all, this space cannot be avoided if coaxial cable or connector, respectively, and PCB include an angle unequal to 90°. Impedance mismatching in the conventional high frequency technology is not serious as far as predetermined limits are not exceeded. They lead, however, to undesired reflections if the transmission frequency attains high valves, e.g. above 500 MHz up to 1 GHz. The distortions occurring cannot be neglected.
From the US patent No. 4,789,357 it has become known to locate a conductive housing around the pins of a pin header as a continuation of the shielding of a coaxial cable or a shielded receptacle connected with the coaxial cable, respectively. From the European patent application No. 0,131,248, a header has become known wherein a conductive sheet extends partially around the contact pins, with the sheet connected to the conductive housing of a connector. The known header of the European patent application 0,747,205 has a channel-shaped part of conductive sheet associated with the signal contact pins, with the walls of the sheet contacting the conductive housing of the mating connector. From the German patent specification No. 39 04 461, a multi-terminal high frequency plug-type connection is known, wherein a connector of electrically conductive material and the signal conductors are separated by an insulating dielectric material.
With the embodiments described, a sufficient impedance matching may be achieved. However, the construction measures to achieve such matching lead to an expensive manufacture of the connector elements.

SUMMARY OF THE INVENTION

The invention provides a connector element for a high frequency transmission path which is adapted to interconnect components of the transmission path with a predetermined impedance.
This invention demonstrates that an expensive shielding in the area of the connector element is not necessary if a tuning of the impedance takes place in a specific manner. Non-shielded conductor portions of conventional connector elements normally have an impedance which is too high, i.e. higher than the usual impedance values of 50, 75, or 90 Ohm. The impedance of a high frequency transmission line depends upon the inductance and the capacitance of the path as well. If the capacitance of such a transmission path is increased, the impedance decreases and vice versa. The invention uses these principles in that the conductor portions of the connector element are provided with opposite surface portions being spaced from each other with an amount which deviates from that of adjacent parts of the conductor portions. In this manner for example the capacitance between the conductor portions can be increased significantly. By means of the invention, the impedance of a conductor element for a high frequency transmission path, thus, can be reduced or enlarged, with the space between the terminals of the conductor portions remaining unchanged.
As known, the capacitance is dependent upon the distance and the effective surface area of electrodes as well as upon dielectric constant of the medium between the electrodes. According to an embodiment of the invention, the surface portions may be at least partially enclosed by a dielectric material. By a selection of the mentioned parameter, the desired impedance value may be achieved and thus, the desired matching or mismatching with respect to the impedance of the transmission path.
Different geometrical configurations are conceivable to change the capacitance between two conductor portions of the connector element. In the following description only examples are outlined wherein the capacitance is increased and correspondingly, the impedance is reduced. In an embodiment of the invention, the surface portions are parallel to each other. They can be provided with a width larger than the width or the diameter of adjacent parts of the conductor portions. The conductor portions for example can be provided with a square or circular cross section. In the retaining member, the conductor portions may have a larger width than outside the retaining member. In order to accomplish such configuration, the conductor portions can be provided with a thickening which may be integrally formed with the conductor portions. The thickening can be for example circular or rectangular in cross section. A circular expansion leads to a relatively small increase in the capacitance. It has the further disadvantage similar to that of the rectangular thickening that the space between adjacent pairs of conductor portions is also reduced resulting in an improved electro-magnet coupling of adjacent signal conductors. This may cause undesired cross talk between adjacent signal conductors. Therefore, a preferred embodiment of the invention provides a thickening which is triangular in cross section, with the opposite sides of the triangle being approximately parallel. The triangular shape has the advantage that a significant increase in the capacitance between ground and signal conductor is achieved while the capacitance between adjacent ground or signal conductors, respectively, is substantially unvaried.
According to a further embodiment of the invention, the increased area may be an extension T-shaped in cross section, with the transverse web of the extensions of opposite conductor portions being approximately parallel. Also with the embodiment, cross talk can be substantially avoided.
In a further embodiment of the invention, the surface portions are formed by a coining of integral conductor portions. If conductor portions or pairs of conductors are coined in the common plane by bending them towards each other so that the coined portions extend parallel with a smaller space therebetween, the capacitance of this transmission portion is also increased. Preferably, the coined portions are flattened in order to enlarge the cooperating surfaces of the conductor portions. Furthermore, the coined area may have a larger width than adjacent parts of the conductor portions. Such conductor portions can be manufactured relatively simply. The blanks can be made by punching or cutting from wire material while the coined portions are made by a coining step.
It is also possible to produce the surface portions by separate parts which are suitably electrically attached to the conductor portions. The separate parts can be attached to the conductor portions by welding, soldering, adhering or the like. Alternately, the separate parts can be plugged onto the conductor portions. The separate parts can be formed as clips or the like in order to attach them to the conductor portions by a snapping connection. A further embodiment of the invention provides separate parts having projection legs at the end, with a slot formed in the legs from the free end thereof and adapted to accommodate the conductor portion in aligned slots. Preferably, the separate parts are made of sheet material. However, they can be also manufactured of solid material and they may be provided with a triangular, T-shaped, rectangular, circular or the like cross sections similar to the above discussed expansions.
The parts of the conductor portions outside the retaining member are preferably straight and parallel and for example may be pin-shaped to permit an insertion into correspondence receptacles or openings of PCBs. The part of the conductor portions outside the retaining member may include an angle, e.g. 90°. Inside the dielectric member, the part of the conductor portions providing the surface portions may be curved in order to achieve an increase of the capacitance throughout the total length within the retaining member.
As already mentioned, the parts of the conductor portions outside the retaining member may be pin-shaped. Alternatively, these parts can be formed as receptacles, e.g. to be connected with contact pins on a PCB.
The connector element according to the invention can be used for a number of applications. It can be for example used to establish a connection between two PCBs. The PCBs may be located parallel or include an angle relative to each other. The connector element for example can be located adjacent an edge of the PCB and be connected with a bus or the like. A further application for example is to interconnect a female connector part and PCB, with the connector part and the PCB may have an arbitrary angle therebetween.
A third application is to interconnect two female connector parts including an arbitrary angle therebetween. Finally, the connector element according to the invention may interconnect a male connector part and a PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is subsequently explained with reference to accompanied drawings, wherein

Fig. 1 is a perspective view of the connection of a plug-type connector with a PCB through a pin header with a connector elements according to the invention,
Fig. 2 is a perspective view of a further embodiment of a connector element according to the invention,
Fig. 3 is a perspective view of a third embodiment of a connector element according to the invention,
Fig. 4 is a perspective view of a fourth embodiment of a connector element according to the invention,
Fig. 5 is a perspective view of a fifth embodiment of a connector element according to the invention,
Fig. 6 is a perspective view of a sixth embodiment of a connector element according to the invention,
Fig. 7 is a perspective view of a seventh embodiment of a connector element according to the invention, and
Fig. 8 is a perspective view of an eighth embodiment of a connector element according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In Fig. 1, three parallelepiped female plug- shaped connector elements 10 are illustrated connected with coaxial cable 12. The housing 14 of conductive material is connected with the shielding (not shown) of cable 12. Further, a connector element 16 is depicted having a parallelepiped retainer member 18 of dielectric material and a plurality of similar pin-shaped elements 20. Member 18 rests on a printed circuit board 22 (PCB) which is diagrammatically illustrated. The pin-shaped elements or conductor portions 20 are arranged in pairs. The row of adjacent pins 24, for example, serve as signal conductors and the opposite row of conductor portions 26 are, for example, ground conductors. As can be seen, the conductor portions 24, 26 consist of three parts. One part or section 28 or 30, respectively, is embedded in the material of member 18. Contact pins 32, 34 rectangular in cross section extend above and below member 18, respectively. The contact pins 34 are accommodated by holes (not shown) in PCB 22. A connector 10 may be plugged onto each pair of contact pins 24, 26 as indicated in Fig. 1.
The intermediate portions 28, 30 of contact elements 24, 26 are identically shaped so that only portion 30 is discussed in more detail. It is U-shaped and includes two parallel spaced leg portions 38, 40 and a web portion 42 therebetween. The leg portions 38, 40 are triangularly shaped, with one peak attached to the contact pins 32, 34. The web portion 42 has the same width as the edge of the leg portions 38, 40 at the ends thereof. The U-shaped portions 28, 30 may be integrally formed with the elements 24, 26, e.g. through a suitable coining step. However, it is also conceivable to make portions 28, 30 separately and to attach them to the contact pins 32, 34 by welding or soldering.
As can be seen, the opposite surfaces of the web portions 42 of the intermediate parts 28, 30 are close to each other and have a larger surface area than the contact pins 32, 34 outside member 38 which serves as retaining body. The capacitance of the pairs of conductor portions 24, 26 in the range of the intermediate parts 28, 30, thus, is substantially higher than outside retaining member 18. On the other hand, the capacitance between adjacent signal conductor portions 24 or between adjacent ground conductor portions 26 is substantially constant if compared with intermediate portions would be merely throughgoing extensions of the contact pins 32, 34. Thus, the danger of cross talk is not higher than with conventional connector elements.
The Figures 2 to 5 depict modifications of the connector element 16 of Fig. 1. Therefore, similar parts are provided with the same reference number added by a character.
A connector element 16 a of Fig. 2 has a parallelepiped retaining member 18a of dielectric material. It includes a plurality of contact elements 20, i.e. pin-shaped signal contact elements 24a and pin-shaped ground contact elements 26a which are arranged in pairs. Each of the elements 24a, 26a includes contact pins 32a, 34a rectangular in cross section on opposite ends retaining member 18a. Thickened portions 44 are rectangular in cross section and are provided interiorly of the dielectric retaining member 18a. The contact elements 24a, 26a, or the pairs of conductor portions, respectively, have a significantly greater capacitance in the area of retaining member 18a. In contrast to the embodiment of Fig. 1, also the capacitance between adjacent signal conductor portions 24a or between adjacent ground conductor portions 26a is increased which increases the risk or cross talk. The thickening 44 may be integrally formed with conductor portions 24a, 26a, however, it can be separately formed and fitted onto the pins 32a, 34a.
Fig. 3 shows a connector element 16b including a parallelepiped member 18b of dielectric material. Pin-shaped contact elements or conductor portions 24b, 26b form pairs of contact elements 20b, with the contact pins 32b, 34b outside retaining member 18b having circular cross section. In the area of retaining member 18b, the conductor portions 24b, 26b are provided with an expanded portion 46 triangular in cross section, with the portion 46 arranged such that a surface 48 of a portion 46 is close and parallel to the corresponding surface of the portion 46 of the opposite conductor portion. Consequently, the axis of the pin portions 32b, 34b extend through the peaks of the triangle. Similar to the embodiment of Fig. 2, the capacitance between signal conductor portion 24b and ground conductor portion 26b is increased. The triangular shape reduces the cross talk if compared with the embodiment of Fig. 2 because the capacitance between adjacent signal conductor portions 24b or ground connector portions 26b, respectively, is only marginally influenced by expanded portion 46.
In the embodiment of Fig. 4, pin-shaped conductor elements 24c, 26c have extensions 46c T-shaped in cross section, with the transverse web thereof having a surface 48c and the surfaces 48c of opposite conductor portions 24c, 26c of the pairs of conductor portions being parallel and relatively close to each other. The contact pins 32c, 34c are rectangular or square, respectively, in cross section. Extensions 46c again increase the capacitance between signal conductor portions 24c and ground conductor portion 26c significantly, while the capacitance between adjacent signal conductor portions 24c or adjacent ground conductor portions 26c is only changed a small extent relative to a configuration without such extensions 46c.
In the embodiments of Fig. 3 and 4, the extensions 46 and 46c, respectively, are formed integrally with the conductor portions 24c, 26c. It is understood that separate parts could be formed which are attached to the conductor portions in a suitable manner. With the connector element 16d of Fig. 5, the conductor portions 24d, 26d are formed by throughgoing pins of square cross section constituting upper contact pins 32d and lower contact pins 34d. Parts 50, U-shaped in cross section, are attached to the conductor portions 24d, 26d. They are made of conductive sheet material and have parallel legs 52, 54 and a web portion 56 interconnecting the legs. Slots 58 are cut in the legs from the free end thereof which slots are adapted to accommodate the conductor portions 24d, 26d. The parts 50 can be clamped on the conductor portions 24d, 26d or attached thereto by welding or soldering. The opposite surfaces 60 of the web portions 56 are parallel and relatively close to each other. These surfaces increase the capacitance between signal conductor portion 24d and ground conductor portion 26d of pairs of contact elements.
In the embodiments of Figs. 1 to 5, the conductor portions are straight, i.e. the contact pins on both sides of the retaining member 18 to 18d are aligned or located on a common axis. In the embodiments of Figs. 6 and 7, the contact pins include and angle of 90°. A member or body 64 approximately trapezoidal in cross section of suitable dielectric material retains pairs of signal and ground conductor portions 66, 68, respectively, with the ends thereof defining contact pins of square cross section including an angle of 90° therebetween. Each pair of conductor portions 66, 68 are located in a common plane. Inside the retaining body 64, the conductor portions 66, 68 are flattened and broadened as shown at 70 and 72, respectively. Further, the flattened portions 70, 72 are closer to each other than the other parts of the conductor portions 66, 68 outside dielectric retaining body 64. The portions 70, 72 thus, define a range of higher capacitance.
In the embodiment of Fig. 7, curved conductor portions 66a, 68a of square cross section and curved approximately at an angle of 90 are retained by a dielectric retaining body 64a similar to retaining body 64. The conductor portions 66a, 68a are also provided with outer contact pins including an angle of approximately 90°. Bracket-shaped elements 50a include orthogonally extending legs 52a, 54a at the ends thereof having slots 76 formed from the free ends thereof for the accommodation of the curved part 78 of conductor portions 66a, 68a. The legs 52a, 54a are interconnected through a flat curved web portion 80. The curved web portion 80 follwos the course of the bent parts 68 of the conductor portions 66a, 68a. The parts 70 are also formed of sheet material. The web portions 80 are located on opposite sides of conductor portions 66a, 68a so that closely spaced parallel surfaces are formed in order to increase capacitance.
It should be mentioned that the connector elements 16 to 16d and 62, 62a are adapted to be connected with different components of a high frequency transmission path, e.g. with a PCB as shown in Fig. 1 or with connector elements including receptacles. It is also understood that instead of the contact pins disclosed, receptacles could be used without having the principles discussed above.
It is not necessary that the portions or surfaces altering the capacitance property of conductor portions are enclosed by rigid dielectric material, rather, the dielectric can be air. In Fig. 7, it is indicated by a dash-dotted line that the retaining body 62a may have smaller outer dimensions. The parts 50a including the legs 52a, 54a project beyond body 62a whereby a portion of the dielectric medium is air.
The retaining body 64b of the embodiment of Fig. 8 differs from that of Fig. 6 in that it includes square ports or openings 86 on one side which are aligned with receptacles 88 at the end of conductor portions 70b, 72b. The receptacles 88 are formed by two spaced tongues 90, 92, with tongue 90 being a part of the flat conductor portion 70b, 72b, respectively, and tongue 92 may be a separate flat part or attached to tongue 90 through a web (not shown).

Claims

1. A connector element for a high frequency transmission path, comprising at least a pair of spaced conductor portions defining a signal and a ground conductor, said signal and ground conductors having parts retained by a dielectric retaining member, said parts having opposite spaced surface portions, with the ends of said conductor portions including means for the connection with an adjacent electrical component, characterized in that order to change the capacitance along the length of the conductor portions, opposite surface portions of said conductor portions have a configuration and spacing changed from that of said conductor portions to afford a capacitance along the opposite surfaces portions of said retained parts to match the impedance between said conductor portions.

2. The connector element of claim 1, wherein said parts of said conductor portions including said surface portions are at least partially enclosed by said dielectric retaining member.

3. The connector element of claim 1 or 2, wherein said surface portions are parallel.

4. The connector element of claim 1, wherein said surface portions have a width larger than the width of adjacent parts of said conductor portions.

5. The connector element of claim 1, wherein said conductor portions are integrally formed and said surface portions of said parts are formed by an extension of said integrally formed conductor portions.

6. The connector element of claim 5, wherein said extension is circular in cross section.

7. The connector element of claim 5, wherein said extension is rectangular in cross section.

8. The connector element of claim 5, wherein said extension is triangular in cross secton with said opposite surfaces being sides of said triangular extensions and being disposed approximately parallel.

9. The connector element of claim 5, wherein said extension includes an extension T-shaped in cross section, with the transverse webs of said extensions forming said opposite surfaces and being approximately parallel.

10. The connector element of claim 1, wherein said surface portions are formed by a coining of said integrally formed conductor portions.

11. The connector element of claim 1, wherein said surface portion has a greater width than adjacent parts of said connector portions.

12. The connector element of claim 10, wherein said coined portion has a larger width than adjacent parts of said connector portions.

13. The connector elements of claim 1, wherein said surface portions are formed by separate parts attached to said connector portions.

14. The connector element of claim 13, wherein said separate parts are attached to said conductor portions by welding, soldering, adhering or the like.

15. The connector element of claim 13, wherein said separate parts are adapted to be plugged onto said conductor portions.

16. The connector element of claim 15, wherein said separate parts have cantilevered legs at the ends thereof with slots being formed from the free end in said legs and said aligned slots accommodating a said conductor portion.

17. The connector element of claim 14, wherein said separate parts are bent or flat material.

18. The connector element of claim 14, wherein said separate parts consist of solid material and are one of triangular, T-shaped, rectangular, circular or the like in cross section.

19. The connector element of claim 1, wherein with a plurality of adjacent pairs of said conductor portions said surface portions are formed such that the capacitance between said adjacent signal conductor portions or said ground conductor portions, respectively, is significantly changed and the capacitance between adjacent signal conductor portions or said ground conductor portions is left substantially unchanged.