Ground plane for a filtered electrical connector

An improved ground plane for use in an electrical connector features a plurality of contact receiving openings (64) which are stamped into a sheet of conductive material. A spring contact (65) is disposed adjacent each opening (64) and is positioned to undergo both torsional and cantilever beam deformation upon insertion of a filter element (50) in order to urge the filter element (50) against a reference surface (66).

FIELD OF THE INVENTION 
This invention is related to electrical connectors and more particularly to 
a ground plane for use in a filtered electrical connector. 
BACKGROUND OF THE INVENTION 
In high frequency applications, it is often necessary to provide filtering 
in order to maintain signal integrity. The filtering can be accomplished 
by capacitively coupling each signal line passing through a connector to a 
common ground plane. The capacitive coupling can be accomplished in a 
number of ways including the use of chip capacitors or tubular filter 
components which surround each signal pin. One example of such tubular 
filter components is shown in U.S. Pat. No. 3,710,285. In this patent 
Schor et al. teach a plurality of ground planes which establish a low 
impedance ground return circuit for a filter pin connector having a 
connector pin, a tubular filter, and a housing. The ground planes consist 
of thin metal sheets which are in electrical contact with the outer 
surface of the tubular filter and are sandwiched between various 
insulators of the housing. Here the electrical contact between the tubular 
filter and the ground plane is formed by spring contact means 
therebetween. A problem exists with this interface in that precise center 
pin to center pin alignment is difficult to achieve due to the tubular 
filter diameter tolerances and the spring means which is used to make the 
electrical contact. 
An alternate approach to forming this electrical connection is shown in 
U.S. Pat. No. 4,952,896. Here, the filter components are soldered to the 
ground plane. A problem exists with this arrangement in that the soldering 
operation may cause short circuits between adjacent pins, flux entrapment, 
or fractured contact interfaces. All of these problems reduce the 
effective yield of the finished connectors. 
SUMMARY 
It is therefore an object of the present invention to provide an improved 
electrical interface between filter components and a ground plane which 
will achieve reliable electrical connections and proper pin to pin 
alignment. 
This and other objects have been achieved by providing an improved ground 
plane for use in an electrical connector. The improved ground plane 
consists of a plurality of openings formed in the planar surface. A 
plurality of spring members is also formed in a planar surface. Each 
spring member is formed adjacent a respective opening and has a contact 
point for engaging an inserted filter component at a single location to 
urge each respective filter component towards a reference surface of its 
respective opening.

DETAILED DESCRIPTION OF THE EMBODIMENTS 
The invention will first be described generally with reference to FIG. 1. 
The electrical connector (10) consists of a metallic housing (20), a 
dielectric spacer (40) which has a plurality of passages to accommodate 
tubular filter components (50) which surround signal pins (30). A pair of 
ground planes (60) are disposed within the dielectric spacer (40) and have 
a plurality of corresponding filter receiving openings (64) to accommodate 
the filter components (50). 
Each of the major components will now be described in greater detail with 
reference to FIGS. 2-6. Beginning with FIGS. 1 and 2, it can be seen that 
the conductive housing (20) consists of a face plate (22) from which a 
mating section (24) extends in a mating direction. The mating section (24) 
forms an enclosed interface area (26). A pair of jack screw openings (28) 
are formed in the face plate (22) along opposite sides of the interface 
area (26). 
Referring now to FIG. 3, the ground plane (60) is shown as viewed from the 
front end. This ground plane (60) is formed from a plate of metal which is 
simply stamped to form a plurality of filtered contact receiving openings 
(64) in a desired relationship to each other. Each opening (64) consists 
of a reference surface (66) opposite a spring member (68), each spring 
member being defined by a slot (61) and the opening (64) and being 
disposed therebetween. Each spring member (68) has a pair of torsional 
sections (69) adjacent a pair of attachment points (67). The generally W 
shaped spring member (68) has a contact tip (63) disposed approximately 
midway between the torsional sections (69) and extending into the opening 
(64). 
Referring now to FIG. 4 the spacer (40) will be described in greater 
detail. The spacer (40) is formed of a dielectric material and features a 
plurality of contact receiving passages (44) which extend through the 
spacer (40). The spacer (40) may be optionally profiled to have a slot 
extending therethrough from a top end (46) to the bottom end (48) for 
receiving the ground plane (60). Optionally, the spacer (40) could have a 
pair of slots or the slot may extend between the sides (47). As an 
additional option, the spacer 40 may be formed without any slots extending 
therethrough. 
Each of the tubular filters (50) which are shown in FIG. 1 are typically 
formed as a subassembly with the pin (30). The tubular (50) filter may 
consist of a ferrule, overlaid with a barrium titanate cylinder which is 
metallized on the inside and outside. Both ends of the sleeves are 
electroplated along the outer diameter. The pin (30) is soldered inside 
the filter element (50). It should be understood that while the filter 
element has been disclosed here as being of a certain composition, other 
filter elements well known in the art formed of other compositions would 
be equally suitable for surrounding the pins (30). 
Assembly of the electrical connector (10) will now be described in greater 
detail with reference to FIGS. 1 and 2. First, the ground planes (60) of 
FIG. 3 are assembled to the spacer (40) of FIG. 4. This assembly process 
can be accomplished by inserting a ground plane (60) into slot formed in 
the spacer (40). Alternately, a plurality of a spacers (40) without slots 
may be used to sandwich the ground planes (60) therebetween. The ground 
plane (60) and spacer (40) are inserted into the interface area (26) such 
that the ground plane (60) makes electrical contact along at least one 
edge with the mating section (24). Contact and filter subassemblies (30), 
(50) are then inserted into respective contact receiving passages (44), 
(64) such that the contact tips (63) each engage the outer diameter of a 
respective filter element (50). Upon insertion of the filter element (50) 
and engagement with the contact tip (63), the contact section (65) 
deflects to the position shown in FIG. 1. This will cause a torsional load 
on the torsional sections (69) so that the contact section (65) urges each 
contact and filter element subassembly (30), (50) towards its respective 
reference surface(66). It should be understood that the spring member (68) 
undergoes both torsional and cantilever deformation upon contact 
insertion. 
It should be understood that electrical connector assembly (10) shown here 
may then be assembled to an insulative housing having electrical contacts 
which mate with the pins (30). The housing may be assembled to face plate 
(22) in a conventional manner. A housing assembly is not shown here 
because a variety of housings may be utilized such as a right angle 
insulative housing or a simple straight through insulative housing. 
A first alternate ground plane (162) is shown in FIG. 5. A ground plane 
(160) is similarly formed of a sheet of conductive material and has a 
plurality of contact receiving openings (164). Spring members (165) extend 
adjacent each contact receiving opening (164) from an attachment point 
(167). Each spring member is defined by a contact receiving opening (164) 
and a slot (161) and is disposed therebetween. A contact point (163) 
extends into the contact receiving opening (164) from the spring member 
(165). A reference surface (166) is disposed inside the contact receiving 
opening (164) opposite the contact point (163). This spring member (165) 
also undergoes simultaneous cantilever beam and torsional deformation upon 
insertion of the filter element (50) to urge it against the reference 
surface (166). 
FIG. 6 shows yet another alternate embodiment of a ground plane (260) 
having a plurality of contact receiving openings (264) and a spring member 
(265) extending from an attachment point (267) adjacent each contact 
receiving opening (264). Spring member (265) is defined by a contact 
receiving opening (264) and a slot (261) and is disposed therebetween. A 
contact point (263) similarly urges the filter component (50) against a 
reference surface (266). The spring member (265) differs from a spring 
member (165) in that it is wider at the attachment point (267) than in the 
vicinity of the contact point (263). This will effect the spring 
properties and result in different cantilever and torsional deformations. 
It therefore should be understood that the shape and size of the spring 
contact (65), (165), (265) can be varied to achieve the appropriate spring 
property depending on such factors as the number of ground planes inside 
the connector, the size and the mass of each filter element (50), the 
tolerance in diameter of the filter element (50), the surface area 
required of the contact point (63), (163), (263), and other design 
considerations. 
An advantage of the present invention is that it provides a simply stamped 
ground plane which biases each filter element and pin assembly against 
reference surfaces to assure proper pin to pin alignment. 
An additional advantage of the present invention is that it provides a 
reliable electrical connection between each filter element and an outer 
metallic housing or shield member. It should be understood that while this 
invention is shown here embodied by the attached drawings and description, 
variations which would be obvious to one skilled in the art are intended 
to be within the scope of the invention and therefore the scope of the 
invention is intended to be limited only by the attached claims.