Note: Descriptions are shown in the official language in which they were submitted.
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EMI FILTERED CONNECTORS USING INTERNALLY
GROUNDED FEEDTHROUGH CAPACITORS
BACKGROUND OF THE INVENTION
This invention relates generally to ElVll filtered connectors. More
specifically, the present invention relates to EMI filtered connectors which
utilize
one or more internally grounded feedthrough capacitors.
Internally grounded ceramic feedthrough Biter capacitors greatly
improve the reliability and reduce cost of E1V11 filters for medical implant
terminals. Exemplary internally grounded feedthrough capacitors are shown
and described in U.S. Patent No. 5,905,627 entitled INTERNALLY GROUNDED
FEEDTHROUGH FILTER CAPACITOR, the contents of which are incorporated
herein.
Ceramic feedthrough capacitors are used in a wide range of electronic
circuit applications as EMI filters. Feedthrough capacitors are unique in that
they
provide effective EMI filtering over a very broad frequency range. For
example,
this can be from a few Kilohertz to fens of Gigahertz. The mounting or
installation of feedthrough capacitors in a typical electronic circuit is
always
problematic. For one thing, in order to provide proper shielding and
attenuation
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the EMI filter must be installed as a continuous part of the overall EMI
shield.
This overall EMI shield is usually metallic. Because of the metallic nature of
most EMI shields, the installation of a relatively brittle barium titinate-
based
ceramic capacitor is inherently problematic. This is due to mismatches in
~ thermal coefficient of expansion and resulting nnechanical stresses, which
can
fracture the relatively brittle monolithic ceramic capacitor and lead to
either
immediate or latent electrical failures. The internally grounded capacitor
described in U.S. Patent No. 5,905,627 was designed to overcome these
difficulties.
Figure 1 illustrates filtered connectors 20a-201 that are typically used
in the military, aerospace, medical, telecommunication and other industries.
In
an EMI filtered connector, such as those typically used in aerospace,
military,
telecommunications and medical applications, it is very difficult to install
the
feedthrough capacitor to the connector housing or back shell without causing
excessive mechanical stress to the ceramic capacitor. A number of unique
mounting schemes are described in the prior art, which are designs that
mechanically isolate the feedthrough capacitor while at the same time provide
the proper low impedance ground connection arid RF shielding properties. This
is important because of the mechanical stresses that are induced in a filtered
connector. It is problematic to install a relatively brittle ceramic
feedthrough
capacitor in a filtered connector because of the resulting mismatch in thermal
coefficient of expansion of the surrounding materials, and also the
significant
axial and radial stresses that occur during connector mating.
By definition, connectors come in female and male versions to be
mated during cable attach. The EMI filtering is typically done in either the
female or the male portion, but usually not both. During the insertion or
mating .
of the connector halves, significant mechanical forces are exerted which can
be
transmitted to the feedthrough capacitor.
As described in U.S. Patent No. 5,905,627, the capacitor ground
electrode plate is internally attached to one or more lead wires; which can
pass
all the way through the device or to one or more grounded studs: In the '627
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patent, these capacitors were shown uniquely mounted to a variety of
implantable medical hermetic terminals such as those used in cardiac
pacemakers, implantable defibrillators and the like. By way of example, U.S.
Patent No. x,905,627 illustrates a rectangular feedthrough capacitor with an
internally grounded electrode, which is also shown as Figure 2 through 6
herein.
More particularly, an internally grounded feedthrough filter capacitor
assembly is generally designated in Figure 6 by the reference number 22. The
feedthrough fitter capacitor assembly 22 comprises, generally, at feast one
conductive terminal pin 24 and a conductive ferrule 26 through which the
terminal pin passes in~non-conductive relation. An insulator 28 supports each
conductive terminal pin 24 from the conductive ferrule 26 in electrically
insulated
relation, and the assembly of the terminal pins, the conductive ferrule and
the
insulators comprises a terminal pin sub-assembly 30. The feedthrough filter
capacitor assembly 22 further includes a feedthrough filter capacitor 32 that
has
first and second sets of electrode plates 34 and 36. A first passageway 38 is
provided through the feedthrough filter capacitor 32 through which the
terminal
pin 24 extends in conductive relation with the first set of electrode plates
34.
The feedthrough filter capacitor 32 further includes a second passageway 40
into which a ground lead 42 extends. The ground lead 42 is conductively
coupled to the second set of electrode plates 36 and the conductive ferrule
26.
Typically, the conductive ferrule 26 is canductively mounted to a conductive
substrate 44 that may comprise, for example, the housing for an implantable
medical device.
The internally grounded feedthrough filter capacitor assembly 22
eaiminates the need for external conductive connections between the capacitor
and a ground by connecting the internal ground plates to a ground pin,
tubelet,
or similar ground lead structure. This is' a particularly convenient and cost
effective approach for certain implantable cardioverter defibrillators (ICDs}
that
already employ a grounded terminal pin in order to use the titanium housing of
30. the implanted ICD as one of the cardiac electrodes. As there is no
external
electrical connection, the need for external capacitor metalization around the
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capacitor perimeter or outside diameter has been eliminated. This not only
reduces expensive metaNlization firing or plating operations, but also
eliminates
the joining of materials which are not perfectly matched in thermal
coefficient of
expansion.
The feedthrough filter capacitor 32 comprises a monolithic, ceramic
internally grounded bipolar feedthrough filter capacitor having three
passageways extending therethrough. The outer two passageways are
configured to receive therethrough respective conductive terminal pins 24, and
the internal diameter of the first passageways 38 are metallized to form a
conductive link between the first sets of electrode plates 34. As is well
understood in the art, the first sets of electrode plates 34 are typically
silk-
screened onto ceramic plates forming the feedthrough filter capacitor 32.
These
plates 34 are surrounded by an insulative ceramic material that need not
metallized on its exterior surfaces.
Similarly, a second set of electrode plates 36 is provided within the
feedthrough filter capacitor 32. The inner diameter of the central or second
passageway 40 through the feedthrough filter capacitor 32 is also metallized
to
conductiveiy connect the second set of electrode plates 36 which comprise the
ground plane of the feedthrough filter capacitor 32. The second passageway 40
is configured to receive therethrough the ground lead 42 which, in this
particular
embodiment, comprises a ground pin.
With referencetoFigure 5, the terminaN pin subassembly 30 comprises
a~ plate-like conductive ferrule 26 having three apertures therethrough that
correspond to the three passageways through the feedthrough filter capacitor
32. The conductive terminal pins 24 are supported through the outer apertures
by means of an insulator 28 {which also may be hermetic), and the ground pin
42 is supported within the central aperture by a suitable conductor 46 such as
a solder, an electrically conductive thermal setting material or
welding/brazing.
The feedthrough filter capacitor 32 is placed adjacent to the non-body
fluid side of the conductive ferrule 26 and a conductive attachment is
effected
between the metallized inner diameter of the first and second passageways 38
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and 40 through the fieedthrough fiilter capacitor 32 and the respective
terminal
pins 24 and ground lead 42. As was the case described above in connection
with the attachment of the ground lead 42 to the conductive ferrule 26, the
conductive connection 48 between the terminal pins 24 and the ground lead 42
with the feedthrough filter capacitor 32 may be effected by any suitable means
such as a solder or an electrically conductive thermal setting material or
brazing.
The result is the feedthrough filter capacitor assembly 22 illustrated in
Figure 6
which may then be attached to the conductive substrate 44.
EMI filtered connectors are typically manufactured using monolithic
ceramic capacitor arrays 50a and 50b. Examples of these multi-hole capacitor
arrays are shown in Figure 7. Planar arrays can vary in the number ~of
feedthrough holes from one all the way up to several hundred in some cases.
In the planar arrays 50a and 50b shown in Figure 7, both the inside diameter
of
the feedthrough holes 52 and the entire outside perimeter 54 are metallized.
The purpose of the metallization is to connect the electrode plates in
parallel and
to provide a surface for electrical attachment to the capacitor. The
metallization
usually consists of a fired-on silver loaded glass frit, plating, or the like
(sometimes gold terminations are used). The general material used for the
dielectric is barium titivate. Accordingly, these devices, when fired, are
very
brittle (and mechanically weak). In an EMl filtered connector, the brittle
ceramic
capacitor does not match the thermal coefficient of expansion of the
surrounding
connector metallic material (such as the connector housing or back shell).
Because ofi this, mechanical stresses are introduced during capacitor
installation, mechanical connector mating and during temperature cycling.
Figure 8 is a cross-sectional view of a typical filtered connector 56 in
a~ rr filter configuration. As can be seen the two ceramic discoidal
capacitors 58
are directly attached to the inside diameter of the connector. This results in
an
area of high stress concentration, which can lead to fractures of the
monolithic
ceramic capacitor. These fractures can result in either immediate or latent
electrical failure. A number of manufacturers of filtered connectors have gone
to great lengths to mechanically isolate the ceramic feedthrough capacitor.
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Figure 9 is an illustration of such a system, which shows spring contact
fingers
60, fit which isolate the capacitors 58 (disposed on either side of an
intermediate ferrite inductor 64) mechanically, loth for the ground
connections
to the connector 56 and the connection between the lead wire 66 and the
capacitor inside diameter. This allows the capacitors 58 to structurally float
thereby making them much less sensitive to damage during connector insertion
or during thermal cycling:
Figure 10 is a connector manufactured by Amphenol utilizing beryllium
copper contact resistance clips 68, which ,provide the ground spring as
previously ,described in Figure 9. Figure 10 also illustrates that a beryllium
copper EMI grounding spring 70 has been used at the inside diameter contact
of the ceramic capacitor. This assembly has been very successful in the
industry; however, it is quite complicated and expensive to manufacture.
Figure
1.0 further illustrates a machine aluminum alloy shell 72, a stainless steel
socket
hood 74, front removable machine copper alloy contacts 76, a silicone rubber
interfacial seal 78, a high temperature dielectric insert 80, a monolithic
planar
capacitor array 82, sealing and stress isolating elastomeric gaskets 84, a
fixed
rear nation contact 86, and a ferrite inductor 88.
Figure 11 il[ustrates yet another prior art Amphenol connector which
has utilized grounding springs 68 and 70 in order to isolate the monolithic
ceramic capacitor arrayfrom the mechanical stresses due to the connector
itself.
Components illustrated in Figure 11 that are equivalent to the components of
the
connector of Figure 10 show the same reference number.
In summary, Figures 8 through 11 illustrate various methods of
installing ceramic capacitor arrays inside of a connector back shell or
housing.
As can be seen, the capacitors as installed in Figure 8 are subject to damage
caused by both mechanical and thermal stre:;ses. Solutions as indicated in
Figures 9, 10 and 11, are effective; however, they are expensive, complicated
avd not very volumetrically efficient:
Accordingly, there is a need far novel filter connectors which utilize the
internally grounded feedthrough capacitor as described above in. a variety of
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filtered connector applications. Modification of the connector is needed to
adapt
it to be compatible with the internally grounded capacitors. Such
modifications
must provide a low impedance electrical connection that will operate to
several
gigahertz white at the same time mechanically isolating the ceramic capacitor
so
that excessive mechanical stresses do not result. The present invention
fulfills
these needs and provides other related advantages.
SUMMARY OF THE INVENTION
The present invention resides in an improved EMI filtered connector
which provides the proper degree of both thermal and mechanical isolation of
an array of feedthrough filter capacitors from the connector housing and yet
at
the same time provides a low impedance RF connection so that a high degree
of EMI filtering effectiveness is maintained. The EMI filtered connector of
the
present invention comprises, generally, a plurality of conductive terminal
pins,
a grounded conductive connector housing through which the terminal pins pass
in non-conductive relation, and an array of feedthrough filter capacitors each
having a distinct first set of electrode plates, .a non-distinct second set of
, electrode plates, and a first passageway through which a respective terminal
pin
extends in conductive relation with the first set of electrode plates. As used
herein, a distinct set of electrode plates refers to a set of electrode plates
which
are distinctly separate and associated with a particular capacitor of the
feedthrough filter capacitor array. A non-distinct set of electrode plates
refers
to those plates which are common to two or more of the distinct capacitors in
the
array of feedthrough filter capacitors. At least one ground lead is
conductively
coupled to the conductive connector housing, and extends into a second
passageway through the array of feedthrough filter capacitors in conductive
relation with the second set of electrode plates.
In a preferred form of the invention, the outer peripheral surtace of the
array of feedthrough fitter capacitors is non-conductive. Further, an
insulator is
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disposed in or adjacent to the connector, for mounting the conductive terminal
pins for passage through the conductive connector with the conductive terminal
pins and the connector is non-conductive relation. The insulator may provide
means for hermetically sealing passage of the terminal pins through the
connector housing, as well as means for hermetically sealing passage of the
ground lead through the connector housing.
The array of feedthrough filter capacitors may be symmetrical about
the ground lead or asymmetrical. The ground lead may form a portion of the
connector housing. Further, an insulative washer may be disposed between the
array of feedthrough filter capacitors and the connector housing.
In one illustrated embodiment, a grounding ring is conductivelycoupled
to the ground lead and to the connector housingl. The grounding ring is
secured
to the ground lead utilizing a conductive washer and a retaining clip. As
shown,
a plurality of ground leads in conductive relation with the second set of
electrode
plates are provided, wherein all of the ground leads are conductively coupled
to
the grounding ring.
A plurality of arrays of feedthrough filter capacitors may be provided
within a single grounded conductive connector. In this case, each ofthe
plurality
of arrays of feedthrough capacitors may be provided with its own non-distinct
second set of electrode plates.
A novel feature of the internally grounded feedthrough capacitor is the
elimination of all electrical and mechanical attachments to the outside
diameter
or the perimeter of the feedthrough capacitor. This allows the filtered
capacitor
to float on the connector pins thereby eliminating the problems with
conventional
connectors. The result is a more cost effective and much more reliable
filtered
connector assembly.
Other features and advantages of the present invention will become
apparent from the following more detailed description, taken in conjunction
with
the accompanying drawings, which illustrate, by way of example, the principles
of the invention.
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BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention. In such drawings:
FIGURE 1 illustrates prior art filtered connectors that are typically used
~ in the military, aerospace, medical, telecommunication and other industries;
FIGURE 2 iifustrates a prior art internally grounded feedthrough
capacitor in accordance with U.S. Patent No. 5, 905,627;
FIGURE 3 illustrates the active electrode plate pattern of the capacitor
of FIG. 2;
FIGURE 4 illustrates the ground electrode plate pattern of the
capacitor of FIG. 2;
FIGURE 5 illustrates a hermetically sealed terminal which includes the
capacitor of FIG. 2;
FIGURE 6 illustrates the internally grounded capacitor of FIG. 2
mounted to a hermetic seal terminal and housing of an implantable
defibrillator;
FIGURE 7 shows examples of typical prior art multi-hole capacitor
arrays;
FIGURE 8 is a cross-sectional view of a typical prior art filtered
connector in a n filter configuration, with direct c~D (outer diameter) attach
and
resultant high mechanical stress #o the capacitors;
FIGURE 9 is a cross-sectional view of a prior art feedthrough capacitor
with spring attachments;
FIGURE 10 is a cross-sectional view of a prior art Amphenol filtered
connector;
FIGURE 11 is a cross-sectional view of a prior art Amphenol filtered
connector with EMI grounding springs;
FIGURES 12A-12F illustrate a sub D-type filtered connector with
twenty-five pins and utilizing an internally grounded feedthrough capacitor;
FIGURE 13 shows an hermetic connector with a novel grounding ring
for providing one or more grounded pins for the internally grounded capacitor;
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FIGURES 14A-1.4E show an hermetically sealed connector with
internally grounded feedthrough capacitor with rlovel locking clips and
retaining
ring;
FIGURES 15A-15F illustrate a circular quadpolar connector with an
internally grounded feedthrough capacitor; and
FIGURES 16A-16i illustrate how two or more individual internally
grounded feedthrough capacitors can be used to provide filtering in a very
large
connector array or connector block.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a method for mounting a monolithic
ceramic capacitor to an electronic connector in a manner which provides the
proper degree of both thermal and mechanical isolation from the connector
housing and yet at the same time provides a low impedance RF connection so
that a high degree of EMI filtering effectiveness (attenuation) is maintained.
A
feature of the present invention is that an internally grounded electrode
plate can
be grounded at multiple points (not just at its outside diameter or
perimeter).
This overcomes a serious deficiency in prior art filtered connectors that are
physically large. In a large conventional prior arf filtered connector, the
pins
closest to the center are a relatively long distance from the outside diameter
or
perimeter ground. This creates inductance which tends to reduce the filtering
efficiency (attenuation in dB) ofthese pins. This situation is remedied by the
use
of a grounded pin near to the center of the array. A multipoint ground
attachment assures that the capacitor ground plane will present a very low RF
impedance to ground which guarantees that the feedthrough capacitor will
operate as a broadband filter with a high level of attenuation. Moreover, use
of
an internal ground eliminates the outer diameter (OD) termination on the
capacitor, and also eliminates of the need for an electrical/mechanical
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connection between the shielded case or housing and the capacitor OD (or
perimeter in the case of rectangular feedthrough).
In the following description of the preferred embodiments, elements
which are functionally equivalentto those described above in connection with
the
internally grounded feedthrough filter capacitor assembly 22 of Figures 2-6
will
share common reference numbers in increments of 100. Thus, the D-type filter
connector of Figs.12A-12F is referred to generally by the reference number
122,
the hermetic connector of Figures 13 and 14A-14E is designated generally by
the reference number 222, the circular quadpolar connector of Figs.15A-15F is~
designated generally by the reference number 322, and the connector shown in
Figs. 16A-161 is designated by the reference number 422.
In accordance with the invention, EMI filtered connectors 122-422 are
provided which utilize one or more internally grounded feedthrough capacitors
132-432. Novel filtered connectors incorporating internally grounded
feedthrough capacitors provide a number of very important advantages
including:
1. The elimination of the capacitor's OD or perimeter termination;
2. Reduced cost because of elimination of the metallization and firing
steps for the OD termination;
3. Greatly reduced mechanical. stress because the capacitor is free
to float on its pins;
4. The capacitor is much more rugged and resistant to both thermal
shock and mechanical stresses due to mismatches in thermal coefficients
of expansion;
5. Capacitor installation is greatly simplified;
6. Reliability is improved; and
7. The capacitor is much less subject to damage during the insertion
stresses created during connector mating.
With reference to Figures 12A-12F, there is shown a sub D-type
filtered connector 122 utilizing an internally grounded capacitor 132. A novel
feature of this approach is that two of the ground pins 142 (the one furthest
from
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the left and the one furthest from the right) are grounded right to the
metallic
case 144 of the connector itself (the pins may be attached by welding,
brazing,
soldering, conductive adhesives, swadging, press-in or the like). The
capacitor
feedthrough.holes 138, 140 are then attached to each one of the pins 124, 142
(including the two grounded pins 142). The attachment to the ground pins 142
connects the capacitor ground electrode plate stack 136 in accordance with the
principles of the internally grounded capacitor. These . pin to capacitor
feedthrough hole attachments can be made by automated wave soldering
processes, conductive adhesives, spring contact fingers, or the like. This
novel
connector design method allows the capacitor 132 to float entirely on the pins
124, 142 with no mechanical connection at all between the capacitor outside
perimeter and the case itself. This completely eliminates the need for
capacitor
outside perimeter metallization which is itself an expensive process. The
active
feedthrough holes 138 of fihe capacitor of Figure 12 are connected to the
other
connector pins 124 which provides effective EMI filtering. In Figure 12F, the
ground electrode plate is cut away so that the active electrode plates are
' partially exposed. A.plurality of ground and active electrode plate sets
136, 134
are stacked up to achieve the desired capacitance value.
Generally, the active area of each capacitor is adjusted by controlling
the area of the active electrode plate (silk screen design and metal laydown
control). Those pins that have a smaller active electrode area will have less
capacitance. The voltage rating of the capacitor is dependant upon the
dielectric
thickness between the electrode plates and the width and accuracy of the
capacitor margin areas. In order to manufacture such large planar array
capacitors successfully, accurate registration of the active and ground
electrode
plates is critical. In order to accomplish this, large planar array capacitors
are
typically manufactured using full or modified wet stack techniques which
includes
automated silk screening of the electrodes. Accurate hole drilling is also
critical.
A significant amount of process "art" is involved in this manufacturing
operation,
particularly in light of the non-linear shrinkage characteristics of the large
ceramic arrays wherein the hole to hole spacing may vary.
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Figures 13 and 14A-14E illustrate a novel military-style filtered hermetic
connector 222 incorporating an internally grounded feedthrough capacitor 232.
in this case, a special grounding ring 256 is slipped over the connector pins
224,
242. In Figure 13, two different grounding ring options are illustrated which
shows that the designer can select any of the pins to be grounded. An
attachment is made of the grounding ring 256; 256' to the connector housing
244. This attachment can be either through welding, brazing, soldering, press
fit and the like. An electrical connection is also made from the grounding
ring
256, 256' to two or more of the connector housing pins 242. As one can see the
grounding ring 256, 256' could ground as.many pins 242 as desired around the
circumference of the connector housing 244. Further, an insulative washer 257
is disposed between the capacitor array 232 and the connector housing 226.
In the section view of FIG. 14E, the ground electrode is partially cut away to
reveal the active electrodes.
There are a number of other methods for providing grounded pins 242
for use in an internally grounded filtered connector 222. For example, the
grounding ring 256 as shown in Figure 13 could be omitted and instead the
inside diameter of the connector housing 244 could be machined in such a way
to ground one or more of the connector pins. Figures 14A-14E illustrate such
a' connector, which has a number of ground pins 242, which are integral to the
connector housing 244.
Internally grounded feedthrough capacitors 232 can be attached in a
variety of unique ways. One such way is shown in Figures 14A-14E wherein
conductive rubber washers 258 are used along with a retaining clip 260. An
alternative to the retairiing clip 260 and conductive rubber washer 258 is to
use
a push nut which exerts a spring force again st the capacitor to seat it to
the
ground post(s).
Figures 15A-15F illustrate a smaller quadpolar hermetic connector 322
wherein the pins 324 are glass sealed into the connector housing 344. There
is a centered ground pin 342 which is brazed orweided and becomes an integral
part of the housing. This pin 342 may also be formed during housing
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manufacturing or screw machine manufacturing of the pin. It is not necessary
that this ground pin 342 protrude all the way through the connector. In other
words, the connector could be a tripolar connector wherein the ground pin 342
is only used to connect to the ground electrode plates 336 of the feedthrough
capacitor 332. In the sectional view of FIG. 15F, the ground electrode 336 is
partially cut away to reveal the active electrodes.
Figures 16A-161 illustrate how two or more individual internally
grounded feedthrough capacitors 432 can be used to provide filtering in a very
large connector array or connector block 422. One or more grounded pins 442
are provided for convenient attachment to the internal ground electrode plates
436 of each feedthrough capacitor. The array that is shown in Figures 16A-161
uses two internally grounded fieedthrough- capacitors 432. It will be obvious
to
one experienced in the art that four, six or even more capacitors could be
used
depending on the number of pins and the geometry of the connector. In the
section view, the ground electrode is partially cut away to reveal the active
electrodes.
It is important that the number of ground pins 442 and their spacing be
adjusted such that the internal inductance of the ground electrode not be too
high. The grounding pin 442 does cause a small amount of inductance which
appears in series with the feedthrough capacitor equivalent circuit. It is a
matter
of geometry and design to make sure that this inductance is small enough so
that the capacitor's self resonant frequency is always above 10 GHz. This is
important for military and space applications, which typically specify
attenuation
up to 10 GHz. For implantable medical device applications the upper frequency
is 3 GHz. This is because of the body's tendency to both reflect and absorb
EMI
fields above 3 GHz.
From the foregoing it will be appreciated that a novel feature of the
present invention is thatthe internally grounded electrode plate can be
grounded
at multiple points (not just at its outside diameter or perimeter). This
overcomes
a serious deficiency in prior art filtered connectors that are physically
large. In
a large conventional prior art filtered connector, the pins closest to the
center are
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a relatively long distance from the outside diameter or perimeter ground. This
creates inductance which tends to reduce the filtering efficiency (attenuation
in
dB) of these pins. This situation is remedied with the novel internal grounded
connector by the addition of a grounded pin near to the center of the array.
This
multipoint ground attachment assures that the capacitor ground plane will
present a very low RF impedance to grownd which guarantees that the
feedthrough capacitor will operate as a broadband filter with a high level of
attenuation.
Another novel feature of the internal ground is the elimination of the
OD termination and also the elimination of the need for an
electricallmechanical
connection between the shielded case or housing and the capacitor OD (or
perimeter in the case of rectangular feedthrough).
A variety of alternate methods of grounding the pins for the internally
grounded feedthrough capacitors) to be mounted in filtered connectors will be
apparent to those skilled in the art. There are literally thousands of
connector
configurations in the market place. !., PI, T and other low pass EMI filter
circuit
configurations simply involve adding one or more inductors, ferrite beads, or
ferrite slabs to the concepts that have been described herein. The
illustrations
herein are intended to demonstrate novel methods of adapting the internally
grounded feedthrough capacitor to filtered connector applications but are not
intended to limit the scope of the invention.
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