U.S. patent number RE46,958 [Application Number 15/248,438] was granted by the patent office on 2018-07-17 for controlled-impedance cable termination using compliant interconnect elements.
This patent grant is currently assigned to Ardent Concepts, Inc.. The grantee listed for this patent is ARDENT CONCEPTS, INC.. Invention is credited to Sergio Diaz, Gordon A Vinther.
United States Patent |
RE46,958 |
Vinther , et al. |
July 17, 2018 |
Controlled-impedance cable termination using compliant interconnect
elements
Abstract
An apparatus for terminating a controlled-impedance cable using
compliant electrical contacts to provide an interface to another
device. The terminator includes an anchor block for securing the
cable. Optionally, the anchor block is electrically non-conductive.
A conductive ferrule is installed on the cable shield and the cable
end is dressed. The ferrule/cable assembly is installed in a
through hole in the anchor block so the cable end is flush with the
anchor block face. An insulating or conductive plate mounted to the
anchor block holds the signal contact that electrically connects
the center conductor to the device and optional ground contacts
that electrically connect the ferrule to the device. The ground
contacts surround the signal contact in a pattern that closely
mimics the impedance environment of the cable. When using a
conductive plate, the signal contact is insulated from the plate by
an insulating centering plug or a non-conductive coating.
Inventors: |
Vinther; Gordon A (Seabrook,
NH), Diaz; Sergio (Cambridge, MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
ARDENT CONCEPTS, INC. |
Seabrook |
NH |
US |
|
|
Assignee: |
Ardent Concepts, Inc. (Hampton,
NH)
|
Family
ID: |
1000003175592 |
Appl.
No.: |
15/248,438 |
Filed: |
August 26, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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14238215 |
|
8926342 |
|
|
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PCT/US2012/061662 |
Oct 24, 2012 |
|
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61550543 |
Oct 24, 2011 |
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Reissue of: |
14534241 |
Nov 6, 2014 |
9160151 |
Oct 13, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01R
13/6473 (20130101); H02G 1/14 (20130101); H01R
12/00 (20130101); H01R 9/0512 (20130101); H02G
1/14 (20130101) |
Current International
Class: |
H01R
12/00 (20060101); H01R 12/50 (20110101); H02G
1/14 (20060101) |
Field of
Search: |
;439/79,80,97,100,581,660 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
International Search Report and Written Opinion for PCT Application
No. PCT/US2012/061662, dated Mar. 25, 2013. cited by applicant
.
Extended European Search Report for European Patent Application No.
12843021.2, dated Jul. 14, 2016. cited by applicant.
|
Primary Examiner: Nguyen; Tuan H
Attorney, Agent or Firm: Altman & Martin Martin; Steven
K
Claims
What is claimed is:
1. A controlled-impedance cable termination for a
controlled-impedance cable, the cable comprising at least one
center conductor, a dielectric surrounding the at least one center
conductor, and a ground shield surrounding the dielectric, the
termination comprising: (a) an anchor block having a face and at
least one cable through hole, the cable through hole having an
opening in the face; (b) a electrically-conductive ferrule adapted
to be installed on the ground shield at the end of the cable, the
ferrule adapted to be captured in the cable through hole .Iadd.such
that the at least one center conductor and the dielectric are flush
with the face of the block.Iaddend.; (c) a plate attached to the
face, the plate having a face surface abutting the face and a
device surface, the plate including at least one signal through
aperture extending between the face surface and the device surface,
the signal .Iadd.through .Iaddend.aperture having a signal block
opening adjacent to and aligned with the cable through hole
opening, the signal .Iadd.through .Iaddend.aperture having a signal
device opening in the device .[.face.]. .Iadd.surface.Iaddend.; and
(d) an electrically-conductive compliant signal contact captured
within each of the at least one signal .Iadd.through
.Iaddend.aperture, the signal contact having a signal block contact
point extending from the signal block opening and a signal device
contact point extending from the signal device opening.
2. The cable termination of claim 1 wherein the anchor block is
composed of an electrically-nonconductive material.
3. The cable termination of claim 1 wherein the ferrule is captured
in the cable through hole by a press fit.
4. The cable termination of claim 1 wherein the ferrule is
removably captured in the cable through hole.
5. The cable termination of claim 1 wherein the plate is composed
of an electrically insulating material and the cable termination
further comprises: (a) the plate including a plurality of ground
through apertures spaced from and surrounding the at least one
signal aperture, each of the ground apertures extending between the
face surface and the device surface, the ground apertures each
having an anchor block opening in the face surface and a ground
device opening in the device face; and (b) an
electrically-conductive compliant ground contact captured within
each of the ground apertures, the ground contact having an anchor
block contact point extending from the anchor block opening into
electrical contact with the ferrule and a ground device contact
point extending from the ground device opening.
6. The cable termination of claim 1 wherein the plate is composed
of an electrically-conductive material and the signal aperture is
within an electrically-nonconductive plug in the plate.
7. The cable termination of claim 6 further comprising: (a) the
plate including a plurality of ground through apertures spaced from
and surrounding the at least one signal aperture, each of the
ground apertures extending between the face surface and the device
surface, the ground apertures each having an anchor block opening
in the face surface and a ground device opening in the device face;
and (b) an electrically-conductive compliant ground contact
captured within each of the ground apertures, the ground contact
having a ferrule contact point extending from the anchor block
opening into electrical contact with the ferrule and a ground
device contact point extending from the ground device opening.
8. A controlled-impedance cable termination assembly comprising:
(a) at least one controlled-impedance cable having at least one
center conductor, a dielectric surrounding the center conductor,
and a ground shield surrounding the dielectric; (b) an anchor block
having a face and at least one cable through hole, the cable
through hole having an opening in the face; (c) an
electrically-conductive ferrule installed on the ground shield at
the end of the cable to form a ferrule/cable assembly, the
ferrule/cable assembly captured in the cable through hole such that
the .[.cable end is.]. .Iadd.center conductor and the dielectric
are .Iaddend.flush with the block face; (d) a plate attached to the
face, the plate having a face surface abutting the face and a
device surface, the plate including at least one signal through
aperture extending between the face surface and the device surface,
the signal .Iadd.through .Iaddend.aperture having a signal block
opening adjacent to and aligned with the cable center conductor,
the signal .Iadd.through .Iaddend.aperture having a signal device
opening in the device .[.face.]. .Iadd.surface.Iaddend.; and (e) an
electrically-conductive compliant signal contact captured within
each of the at least one signal .Iadd.through .Iaddend.aperture,
the signal contact having a signal block contact point extending
from the signal block opening into electrical contact with the
center conductor and a signal device contact point extending from
the signal device opening.
9. The cable termination of claim 8 wherein the anchor block is
composed of an electrically-nonconductive material.
10. The cable termination of claim 8 wherein the ferrule is
captured in the cable through hole by a press fit.
11. The cable termination of claim 8 wherein the ferrule is
removably captured in the cable through hole.
12. The cable termination of claim 8 wherein the plate is composed
of an electrically-insulating material and the cable termination
further comprises: (a) the plate including a plurality of ground
through apertures spaced from and surrounding the at least one
signal aperture, each of the ground apertures extending between the
face surface and the device surface, the ground apertures each
having an anchor block opening in the face surface and a ground
device opening in the device face; and (b) an
electrically-conductive compliant ground contact captured within
each of the ground apertures, the ground contact having an anchor
block contact point extending from the anchor block opening into
electrical contact with the ferrule and a ground device contact
point extending from the ground device opening.
13. The cable termination of claim 8 wherein the plate is composed
of an electrically-conductive material and the signal aperture is
within an electrically-nonconductive plug in the plate.
14. The cable termination of claim 13 further comprising: (a) the
plate including a plurality of ground through apertures spaced from
and surrounding the at least one signal aperture, each of the
ground apertures extending between the face surface and the device
surface, the ground apertures each having an anchor block opening
in the face surface and a ground device opening in the device face;
and (b) an electrically-conductive compliant ground contact
captured within each of the ground apertures, the ground contact
having an anchor block contact point extending from the anchor
block opening into electrical contact with the ferrule and a ground
device contact point extending from the ground device opening.
Description
.Iadd.This application is a Reissue Application of U.S. Pat. No.
9,160,151 issued on Oct. 13, 2015 from Application Ser. No.
14/534,241 filed on Nov. 6, 2014. The entirety of the
above-mentioned patent application is hereby incorporated by
reference herein and made a part of this application..Iaddend.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM
LISTING COMPACT DISK APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical cable terminations,
more particularly, to controlled impedance cable terminations which
are generally used to transmit high-frequency signals in electronic
equipment.
2. Description of the Related Art
The purpose of a cable termination is to provide an interconnect
from the cable to the electrical device and to provide a separable
electrical interconnection between the cable and its operating
environment. The characteristic of separability means that the
cables are not interconnected by permanent mechanical means, such
as soldering or bonding, but by temporary mechanical means.
Currently cables are terminated using a conventional type connector
which is also controlled-impedance, such as an SMA (SubMiniature
Version A) connector, or the cables are soldered to a printed
circuit board (PCB) which is then separably connected to the
working environment. The SMA connectors, while being generally the
same impedance environment as the cable, have impedance mismatches
which cause high-frequency attenuation at the point of interface
between the cable and the connector and the connector and its
working environment, such as like a PCB. Additionally, these cable
terminations often require through holes in PCB's for mounting and,
consequently, it can be difficult to design the best possible
controlled impedance environment. These types of cable terminations
are generally for a single cable and require a substantial amount
of PCB area to terminate, thus decreasing the density capability of
connections.
Another form of prior art is a system which uses two independent
parts to mate several cables to its electrical environment. This
system uses one part that is generally soldered to a printed
circuit board and another part that is generally mated to several
cables. The two pieces can be plugged together to form the
controlled impedance interconnection. These systems are
better-controlled impedance environments but are limited in the
densities at which the cables can be used. That is, the cables
require a minimum space between them to achieve the controlled
impedance environment and thus only a small number of cables can be
terminated in a given area.
Another form of prior art, disclosed in U.S. Pat. No. 7,544,093, is
a system which employs removable cables that are held to the device
by means of a spring. The cable has a terminal end which makes the
signal conductor protrude from the cable terminal end. The terminal
is then pressed to the device by means of a spring and the ground
shield of the cable is connected to the device by a conductive
rubber ground shield that shorts the terminal ground to the device
ground.
BRIEF SUMMARY OF THE INVENTION
The present invention is an apparatus and method for terminating a
controlled-impedance cable that uses a compliant contact element at
the point of termination minimizes detrimental electrical effects
of the termination.
The present invention includes a cable terminator that employs
compliant electrical contacts to provide an interface between the
controlled-impedance cable (hereinafter, simply "cable") and
another device. The assembly is removably attached to the
electrical device by a compression force in a direction of
compression typically provided by jack screws that may not compress
the assembly and device together linearly. Compliant contacts
compensate for noncoplanarities between the conduction points of
the electrical device.
Each embodiment of the terminator includes an anchor block for
securing the cable, one or more compliant signal contacts for
making the electrical connection between the cable center
conductor(s) and the electrical device, optional compliant ground
contacts for making the electrical connection between the cable
shield and the ground plane of the device, and a plate mounted to
the anchor block that holds the contacts.
The anchor block can be either electrically conductive or
nonconductive. When conductive, the ground shield of all of the
cables are electrically connected to the anchor block. The present
invention contemplates several different methods to accomplish this
including soldering the cable ground shield, crimping the ground
shield, potting with a conductive adhesive, insert molding, press
fitting a rigidized ground shield, threading, and twist-lock. Once
the cables are anchored in the anchor block, the anchor block face
and cable ends are dressed to make a reliable electrical contact
with compliant contacts. Dressing may include polishing by some
mechanical means, such as by milling, grinding, or sanding, in
order to make sure that the cable center conductor is positioned at
a known depth with respect to the anchor block face.
When the anchor block is nonconductive, a conductive ferrule is
installed on the ground shield of each cable. The cable ends are
dressed to make a reliable electrical contact with compliant
contacts and the ferrule/cable assemblies are installed into holes
in the anchor block. The present invention contemplates several
different methods to accomplish this including, press fitting,
threading, and twist-lock.
Example compliant contacts for use with the present invention
include spring probes, electrically-conductive rubber contacts,
fuzz button contacts, stamped metal contacts, chemically etched
contacts, and skewed coil contacts.
The plate holds the contacts. Features of the plate include a face
surface that abuts the anchor block face, a device surface that
generally abuts the device, and at least one through aperture for
the contacts. Each aperture has an anchor block face opening and a
device face opening. The apertures for the signal contacts are
aligned with the corresponding cable hole in the anchor block.
The cable center conductor is connected to the signal conduction
point of the electrical device by the compliant signal contact. In
most configurations, the signal contacts are surrounded by a number
of ground contacts that connect either the conductive anchor block
or the cable shield to the device in a pattern that closely mimics
the impedance environment of the cable. The impedance of the system
can be changed by changing the position of the ground contacts with
respect to the signal contact or by changing the insulating
material.
The skewed coil contact is captured in a through aperture in the
plate. The aperture has a larger center section that narrows to a
smaller block opening at the side adjacent to the anchor block and
to a smaller device opening at the other end. The length of the
contact leads is such that the leads extend from the openings.
Alternatively, the block opening is as wide as the center section.
Optionally, the contact area between the center conductor and
device and the corresponding contact lead can be increased by a
pair of conductive bosses that the contact is captured in that is
as wide as the cable center conductor. Optionally, the remaining
space of the aperture is filled with a compliant, electrically
conductive elastomer that adds resiliency and aids in electrically
shorting the coil loops.
The fuzz button contact is cylindrical and forced into an aperture
that is narrower at the center than the ends. The contact ends
extend from the plate.
The conductive rubber contact for the signal contact can be
cylindrical with a centrally-located annular depression that fits
on an annular protrusion in the aperture. The contact ends extend
from the plate. The conductive rubber contact for the ground
contact can be the same structure as the signal contact or can be
circular, surrounding the signal contact.
The etched or stamped contact is a strip of conductive material in
a C shape that is captured in a C-shaped aperture.
The electrical connection between the center conductor and the
signal contact and the electrical connection between the ground
block/cable shield ferrule and the ground contacts are compression
connections. With the contacts installed in the plate, the plate is
mounted to the anchor block with mechanical attachments, thereby
forcing the end of the signal contact against the end of the center
conductor and the ends of the ground contacts against the anchor
block/cable shield ferrule. Alternatively, the electrical
connection between the center conductor and the signal contact is a
solder connection. Alternatively, the end of the center conductor
is formed into a compliant spring like the skewed coil contact.
The plate can be either insulating or conductive. The insulating
plate is made of a non-electrically-conductive material. A
conductive plate is preferably composed of an
electrically-conductive metal that couples the ground contacts,
thereby providing more precise impedance matching to the signal
contact. Alternatively, the conductive plate is composed of a
non-conductive material plated with a conductive coating. The
signal contact is insulated from the conductive plate by an
insulating centering plug or a non-conductive coating.
Alternatively, the signal contact aperture is within a conductive
boss. The boss is surrounded by an insulating annulus that
insulates the boss from the conductive plate.
Also disclosed is a method and apparatus for assembling cables to
the anchor block so that the cables are the same length to within a
very small tolerance. To facilitate the method, a soldering fixture
is used that has a frame, a connector jig, a block jig, and legs.
The frame is generally rectangular and stands vertically. The
connector jig is mounted to the lower cross piece of the frame. The
block jig is mounted to the upper cross piece of the frame. Four
legs extend from the bottom corners of the frame in generally
opposite directions at an angle of at least 10.degree. from
horizontal so that they prevent the frame from falling over but
allow the user to tilt the frame.
The connector jig locks the cable connectors at a fixed distance
away from where the other end of the cable will be soldered to the
anchor block. The connector jig locks the connectors in an upwardly
open arc so that the cables are the same length to the anchor
block.
The anchor block is secured to the block jig, face up, which is
secured to the upper cross piece. A tensioning plate is mounted to
the upper cross piece. Jack screws are threaded into holes at the
end of the tensioning plate.
The cable sheath is stripped and the stripped portion is fed
through the hole in the anchor block and a corresponding cable hole
in the tensioning plate. A coil spring is placed on each cable and
a collar is tightly secured to the cable.
After putting the connectors in the connector jig, the jack screws
are tightened until there is adequate tension on the cables. Each
cable shield is soldered to the anchor block. The angled legs allow
the user to tilt the fixture for easier access to each side of the
anchor block. After the solder and anchor block have cooled
sufficiently, the jack screws are loosened, and the collars,
springs, and tensioning plate are removed. The anchor block is
removed from the frame and the connectors are removed from the
connector jig.
The anchor block face is finished smooth and evenly flat by
sanding, milling, planing, skiving, broaching, or any other
appropriate method.
Objects of the present invention will become apparent in light of
the following drawings and detailed description of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and object of the present
invention, reference is made to the accompanying drawings,
wherein:
FIG. 1 is an isometric view of the cable termination assembly of
the present invention for use with coaxial cables;
FIG. 2 is a front view of the cable termination assembly of FIG. 1
connected to a device;
FIG. 3 is a cross-sectional detail view of the cable termination
assembly connected to a device;
FIG. 4 is a side view of the cable termination assembly of FIG.
1;
FIG. 5 is an exploded view of the cable termination assembly of
FIG. 1 with a conductive anchor block;
FIG. 6 is a top cross-sectional view of the cable termination
assembly of FIG. 2 taken along the line A-A;
FIG. 7 is a front cross-sectional view of the cable termination
assembly of FIG. 4 with a conductive anchor block taken along the
line B-B;
FIG. 8 is a cross-sectional view of a method of removably attaching
the cable to the anchor block;
FIG. 9 is a cross-sectional view of another method of removably
attaching the cable to the anchor block;
FIG. 10 is an exploded view of the cable termination assembly of
FIG. 1 with a nonconductive anchor block;
FIG. 11 is a front cross-sectional view of the cable termination
assembly of FIG. 4 with a nonconductive anchor block taken along
the line B-B;
FIG. 12 is a cross-sectional view showing the common features of
the plate;
FIG. 13 is an isometric view of an angled anchor block;
FIG. 14 is an isometric view of a parallel anchor block;
FIG. 15 is an isometric view of a right-angle anchor block;
FIG. 16 is a cross-sectional side view of a configuration of a
right-angle anchor block;
FIG. 17 is bottom view of the cable termination assembly of FIG. 1
with an insulating plate;
FIG. 18 is a detail view of a configuration of the bottom of the
coax cable termination assembly of FIG. 17 taken at C;
FIG. 19 is a detail view of another configuration of the bottom of
the coax cable termination assembly of FIG. 17 taken at C;
FIG. 20 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with a conductive
anchor block and an insulating plate having mirror-image
sheets;
FIG. 21 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with a nonconductive
anchor block and an insulating plate having mirror-image
sheets;
FIG. 22 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with an insulating
plate having asymmetrical sheets;
FIG. 23 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with an insulating
plate having an elongated center section;
FIG. 24 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with an insulating
plate and conductive bosses;
FIG. 25 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a fuzz button contact with an insulating
plate;
FIG. 26 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a conductive rubber contacts with an
insulating plate;
FIG. 27 is a cross-sectional view of FIG. 26 taken at E-E;
FIG. 28 is a cross-sectional view of FIG. 27 taken at F-F;
FIG. 29 is bottom view of the cable termination assembly of FIG. 1
using stamped or etched contacts embedded in an insulating
plate;
FIG. 30 is a detail view of the bottom of the coax cable
termination assembly of FIG. 29 taken at H;
FIG. 31 is a cross-sectional view of the plate of FIG. 29 before
installation on the anchor block;
FIG. 32 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using stamped or etched contacts embedded in an
insulating plate;
FIG. 33 is an exploded view of the cable termination assembly using
the anchor block of FIG. 14 with an insulating plate;
FIG. 34 is a cross-sectional view of the cable termination assembly
using the anchor block of FIG. 14 with an insulating plate;
FIG. 35 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact for the ground
contacts and a shaped cable center conductor for the signal contact
with an insulating plate;
FIG. 36 is bottom view of the cable termination assembly of FIG. 1
with coaxial cables, a conductive plate, and insulating plug for
the signal contact;
FIG. 37 is a detail view of the bottom of the coax cable
termination assembly of FIG. 36 taken at J with a conductive plate
and insulating plug for the signal contact;
FIG. 38 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with a conductive
plate and insulating plug for the signal contact;
FIG. 39 is bottom view of the cable termination assembly of FIG. 1
with coaxial cables, a conductive plate, dielectric annulus, and
conductive boss for the signal contact;
FIG. 40 is a detail view of the bottom of the coax cable
termination assembly of FIG. 39 taken at K with a conductive plate,
dielectric annulus, and conductive boss for the signal contact;
FIG. 41 is a detailed view of FIG. 7 taken at D showing the coax
cable termination using a skewed coil contact with a conductive
plate, dielectric annulus, and conductive boss for the signal
contact;
FIG. 42 is an isometric view of the cable termination assembly of
the present invention for use with twin-axial cables;
FIG. 43 is a front view of the cable termination assembly of FIG.
42;
FIG. 44 is a top cross-sectional view of the cable termination
assembly of FIG. 43 taken along the line M-M;
FIG. 45 is a side view of the cable termination assembly of FIG.
42;
FIG. 46 is a front cross-sectional view of the cable termination
assembly of FIG. 45 taken along the line N-N;
FIG. 47 is bottom view of the cable termination assembly of FIG. 42
with an insulating plate;
FIG. 48 is a detail view of the bottom of the cable termination
assembly of FIG. 47 taken at R with an insulating plate;
FIG. 49 is a detailed view of FIG. 46 taken at P showing the
twin-axial cable termination using skewed coil contacts with an
insulating plate;
FIG. 50 is bottom view of the cable termination assembly of FIG. 42
with twin-axial cables, a conductive plate, and insulating plugs
for the signal contacts;
FIG. 51 is a detail view of the bottom of the twin-axial cable
termination assembly of FIG. 50 taken at S;
FIG. 52 is a detailed view of FIG. 46 taken at P showing the
twin-axial cable termination using skewed coil contacts, a
conductive plate, and insulating plugs for the signal contacts;
FIG. 53 is a bottom view of an alternative cable termination
assembly of FIG. 42 with twin-axial cables, a conductive plate, and
insulating plugs for the signal contacts;
FIG. 54 is a detail view of the bottom of the alternative
twin-axial cable termination assembly of FIG. 53 taken at T;
FIG. 55 is a detailed view of FIG. 46 taken at P showing the
alternative twin-axial cable termination of FIG. 53;
FIG. 56 is an isometric view of a soldering fixture of the present
invention with cables and anchor block;
FIG. 57 is a front view of the fixture of FIG. 56;
FIG. 58 is a side view of the fixture of FIG. 56;
FIG. 59 is a detail view of the connector jig of FIG. 57;
FIG. 60 is a detail view of the block jig and tensioning plate of
FIG. 57 with the anchor block attached;
FIG. 61 is a detail view of a cable threaded through the block and
tensioning plate;
FIG. 62 is a detail view of the screw and collar installed on a
cable; and
FIG. 63 is a detail view of the tensioning plate in tension.
DETAILED DESCRIPTION OF THE INVENTION
The present application hereby incorporates by reference in its
entirety U.S. patent application Ser. No. 14/238,215, on which this
application is based.
The present invention is an apparatus and method for terminating a
controlled-impedance cable that minimizes detrimental electrical
effects of the termination by using a compliant or compressible
contact element at the point of termination. With the present
invention, impedance mismatches are minimized, allowing the cable
to be more useful in high-frequency signal ranges. The present
invention can be used with any cable structure where the impedance
between the inner conductor(s) and the ground shield is
controlled.
In addition, the present invention increases the density at which
the controlled-impedance cables can be used. That is, with the
present invention, more cables can be terminated in a given amount
of space than with terminations of the prior art. Further, the
interface between the components of the present invention may not
require through-hole mounting, which may further enhance density
capability.
The present invention calls for proper dressing of the cable end so
that small, compliant contacts can be used for separably
interconnecting the controlled-impedance cables to whatever
electrical device the user desires. A prime example is connecting
two printed circuit boards which must communicate with each other
at high frequency, such as connecting a computer central processing
PCB with its random access memory PCB or another central processing
PCB.
As shown in FIGS. 1-11, the present invention includes a cable
terminator 10 that employs compliant electrical contacts 12, 14 to
provide an interface between the controlled-impedance cable
(hereinafter, simply "cable") 30 and another device 2, typically an
integrated circuit (IC) or a printed circuit board (PCB). The
terminator 10 is installed on the cable 30 as described below. The
combination of terminator 10 and cable(s) is referred to as the
cable termination assembly 8. As shown in FIGS. 2 and 3, the
assembly 8 is removably attached to the electrical device 2 by a
compression force 22 in a direction of compression 24. Typically,
jack screws 26 provide the compression force 22. Jack screws 26 may
not compress the assembly 8 and the electrical device 2 together
linearly. Compliant contacts 12, 14 facilitate an adequate
connection between the cables 30 and the electrical device 2,
compensating for noncoplanarities in the conduction points 4 of the
electrical device 2.
The present invention is for use with controlled-impedance cables
having one or more center conductors. A coaxial cable 30 has a
center conductor 32 surrounded by a dielectric 34 with a ground
reference shield 36 outside the dielectric 34. Optionally, a sheath
38 covers the shield 36. A twin-axial cable 30 has two center
conductors 32 surrounded by a dielectric 34 with a ground reference
shield 36 outside the dielectric 34 and a sheath 38 covering the
shield 36. Cables with more than two center conductors are
available. Although not specifically described, the present
invention can be adapted to accommodate cables having more than two
center conductors.
The terminator 10 of the present invention has several embodiments.
Each embodiment includes an anchor block 16 for securing the cable
30, one or more compliant signal contacts 12 for making the
electrical connection between the cable center conductor(s) 32 and
the electrical device 2, optional compliant ground contacts 14 for
making the electrical connection between the cable shield 36 and
the ground plane of the device 2, and a plate 18 mounted to the
anchor block 16 that holds the contacts 12, 14.
In one embodiment, the anchor block 16 is conductive and provides a
common ground for the cables 30, as in FIG. 5. The ground shields
36 of all of the cables 30 are electrically connected to the anchor
block 16. The present invention contemplates several different
methods to accomplish this. The ground shield 36 may be soldered
into a hole 40 in anchor block 16. The cable sheath 38 is stripped
back at least the length of the anchor block hole 40. The cable 30
is inserted into the hole 40 up to the end of the sheath 38 and the
shield 36 is soldered to the anchor block 16.
Alternatively, the cable 30 may be crimped into the anchor block
hole 40. After the sheath 38 is stripped back, the cable 30 is
inserted into the hole 40. The hole 40 may have the path through
which the cable 30 runs geometrically altered after insertion of
the cable 30 to a point where the size of the path is smaller than
the size of the cable 30, thereby anchoring the cable 30 to the
anchor block 16 and electrically connecting the shield 36 to the
anchor block 16.
Other methods of anchoring the cable 30 to the anchor block 16
include potting the ground shield 36 with a conductive adhesive
once it is placed in the hole 40, insert molding the anchor block
16 with the cable 30 in place at the time of molding, and press
fitting a rigidized, for example, pretinned, ground shield into the
hole 40.
Once the cables 30 are anchored in the anchor block 16, the face 20
of the anchor block 16 and cable ends 136 are properly dressed to
make a reliable electrical contact with small compliant contacts.
The cable ends 136 and the anchor block face 20 may need to be
polished and planarized by some mechanical means, such as by
milling, grinding, or sanding, in order to make sure that the cable
center conductor 32 is positioned at a known depth with respect to
the anchor block face 20, in this case flush with the anchor block
face 20. The cable ends 136 and face 20 may also require noble
metal plating to prevent the polished surface from oxidizing or
otherwise degrading so as to inhibit acceptable electrical
connection to the center conductor 32 and the anchor block 16.
Methods of removably attaching the cable 30 to the anchor block 16
are shown in FIGS. 8 and 9. These methods permit replacement of
individual cables 30 so the entire assembly does not have to be
replaced. The first method calls for attaching a ferrule at or near
the end of the cable 30 for dressing the cable end. The sheath 38
is stripped back and a threaded ferrule 134 is slipped over the
shield 36. The ferrule 134 is attached to the cable by soldering,
crimping, or other mechanical means that electrically couples the
ferrule 134 to the shield 36. The cable end 136 is then dressed by
polishing so as to achieve a flat surface on the cable end 136. The
ferrule 134 is then threaded into a threaded hole 138 in the anchor
block 16 until the center conductor 32 is pressed to the signal
contact 12 in order to produce an electrical connection between the
center conductor 32 and the signal contact 12.
In the configuration of FIG. 8, the anchor block 16 has two parts
140, 142. The top part 140 has the threaded hole 138 into which the
ferrule 13 is threaded. The bottom part 142 is for precisely
aligning the cable end 136 so that the center conductor 32 is
directly over the signal contact 12. This method can be use for
precisely terminating individual cable on very tight pitch as in 1
mm or less spacing between cable center conductors 32.
The second method of removably attaching the cable 30 to the anchor
block 16 calls for the use of a twist-lock attachment 300, as shown
in FIG. 9. A twist-lock component 302 is slipped over the cable 30
such that the component 302 can slide freely over the cable 30. A
coil spring 304 is slipped over the cable 30. After the sheath 38
is stripped back, a ferrule 306 is attached to the shield 36 by
soldering, crimping, or other mechanical means that electrically
couples the ferrule 306 to the shield 36. The cable end 308 is then
dressed by polishing so as to achieve a flat surface on the cable
end 308.
The cable end 308 is inserted into a hole 310 in the anchor block
16. Protrusions 312 from the twist-lock component 302 slide down
opposed notches, not shown, in the sides of the hole 310 until they
align with an annular depression 316 in the hole 310. With this
alignment, the spring 304 is compressed so that it presses the
center conductor 32 to the signal contact 12 in order to produce an
electrical connection between the center conductor 32 and the
signal contact 12. The twist-lock component 302 is turned so that
the protrusions 312 are captured by the annular depression 316,
thereby retaining the cable 30 in the hole 310.
In another embodiment, the anchor block 16 is nonconductive and
merely provides an anchor for the cables 30, as in FIGS. 10 and 11.
The anchor block 16 is composed of a nonconductive material. The
cable sheath 38 is stripped back and an electrically-conductive
ferrule 330 is slipped over the shield 36. The ferrule 330 is
attached to the cable by soldering, crimping, or other mechanical
means that electrically couples the ferrule 330 to the shield
36.
The cable end 332 is then dressed by polishing so as to achieve a
flat surface on the cable end 332. The ferrule 330 is then inserted
into a hole 334 in the anchor block 16 until the center conductor
32 is pressed to the signal contact 12 and the ferrule 330 is
pressed against the ground contacts 14.
The present invention contemplates a number of different ways for
the ferrule/cable assembly to be retained in the anchor block 16.
Two such methods are described above with reference to removable
cables and FIGS. 8 and 9. The first uses a threaded attachment and
the second uses a twist-lock attachment.
Another method is via a press fit. Optionally, the side 340 of the
ferrule 330 is knurled or otherwise roughened. The ferrule/cable
assembly is forced into the hole 334, which is slightly smaller,
until the cable end 332 is flush with the block face 338.
Another method is shown in FIG. 11. The ferrule 330 has an annular
ridge 342 either at the end 344 of the ferrule 330 or away from the
end 344, as in FIG. 11. The anchor block 16 has two sections, a
bottom section 346 and a top section 348. The upper end of the hole
334 in the bottom section 346 has an annular groove 352. When the
ferrule/cable assembly is inserted into the hole 334, the ridge 342
fits into the groove 352 with the cable end 332 flush with the
block face 338. The block top section 348 is installed on the
bottom section 346 and attached via screws, clips, or any other
acceptable method. The top section 348 captures the ferrule/cable
assembly in the anchor block 16. Optionally, the ridge 342 and
groove 352 can be keyed to prevent the ferrule/cable assembly from
rotating in the hole 334.
In some designs, particularly with removable attachments, the cable
end may not be exactly flush with the anchor block face 20, that
is, it may be slightly recessed into or protruding from the anchor
block face 20. That recession or protrusion can be as much as 0.05
inch. The present specification and claims use the term, "flush",
to indicate that the cable end is actually flush with, slightly
recessed into, or slightly protruding from the anchor block face 20
by as much as 0.05 inch.
In most of the present figures, the anchor block 16 is generally a
rectangular solid where the cables 30 are perpendicular to the
anchor block face 20. However, the anchor block 16 can have other
shapes. FIG. 13 shows an angled anchor block 16 where the cables 30
are at an angle to the anchor block face 20. FIG. 14 shows a
parallel anchor block 16 that can be used with a device edge
attachment.
FIG. 15 shows a generic right angle anchor block 16 where the
cables 30 bends through 90.degree.. FIG. 16 shows a right angle
anchor block 16 with a strain relief. The anchor block 16 has a
base 280 that is composed of a conductive or non-conductive,
generally rigid material. The cable 30 rests in a channel 284 in
the base 280. A cover 282 that is composed of a conductive or
non-conductive, relatively rigid material is attached to the base
280. The manner of attachment depends on the base and cover
materials. For example, if the base 280 and cover 282 are both
metallic, the attachment can be by screws. If the base 280 and
cover 282 are both plastic, the attachment can be the cover 282
snapping onto the base 280 with tabs and slots. The channel 284 has
a bend 286 that provides strain relief when the base 280 and cover
282 are assembled.
These are only examples of other anchor block shapes. The present
invention contemplates that the anchor block 16 can have any shape
that works for a particular application.
Example compliant contacts for use with the present invention
include spring probes, electrically-conductive rubber contacts,
fuzz button contacts, stamped metal contacts, chemically etched
contacts, and skewed coil contacts.
A typical spring probe consists of a hollow barrel with a spring
and one or two plungers. The spring is housed in the barrel with
the end of the plungers crimped in opposed open ends of the barrel
at the ends of the spring. The spring biases the plungers
outwardly, thereby providing a spring force to the tip of the
plungers.
Conductive elastomer bumps are made of rubber and/or silicones of
varying types with embedded conductive metal elements. The
elastomer bump can work when the device conduction point is
elevated off the device, thus sometimes requiring a protruding
feature from the device or the addition of a third conductive
element to the system to act as a protruding member.
Alternatively, the contact can be made of a single sheet of
anisotropic conductive elastomer which is an elastomeric sheet that
only conducts electricity through its thickness.
A fuzz button is a wire that is crumpled into a cylindrical shape.
The resulting shape looks very much like tiny cylinder made of
steel wool. When the cylinder is placed within a hole in a sheet of
nonconductive material, it acts like a spring that is continuously
electrically shorted. Like elastomer bumps, the fuzz button can be
used with a third element needed to reach inside the hole of the
nonconductive sheet to make contact with the fuzz button.
Skewed coil contacts of various types and configurations are
described in U.S. Pat. Nos. 7,126,062 and Re41,663, both of which
are incorporated herein by reference. Briefly, the skewed coil
contact includes a coil of conductive, inherently elastic wire with
a pair of oppositely extending leads. The leads extend in a
direction angled from the coil axis. During compression, the coil
loops are electrically shorted together while they slide along each
other.
The figures illustrate the use of skewed coil contacts, fuzz button
contacts, conductive rubber contacts, and stamped metal or a
chemically etched contacts. As indicated above, the plate 18 holds
the contacts 12, 14. The structure of the plate 18 depends on the
type of contact. Regardless of the type of contact, the plate 18
has several common features. These features are shown in FIG. 12
with reference to the skewed coil contact as a signal contact 12,
but apply to all types of contacts as well as the ground contacts
14. The plate 18 has a face surface 170 that abuts the anchor block
face 20 when the terminator 10 is assembled. The plate 18 has a
device surface 172 that generally abuts the device 2 when the
terminator 10 is connected to the device 2. The plate 18 has at
least one through aperture 174 for the contacts 12, 14. The
apertures are either signal apertures or ground apertures,
depending on the type of signal that is carried in the contact in
that aperture. Each aperture 174 has an anchor block face opening
176 and a device face opening 178. The signal apertures for the
signal contacts 12 are aligned with the corresponding cable hole 40
in the anchor block 16. Prior to assembling the plate 18 to the
anchor block 16, the anchor block contact point 180 of the contact
12 extends from the anchor block face opening 176. Prior to
connecting the terminator 10 to the device 2, the device contact
point 182 of the contact 12 extends from the device face opening
178.
FIGS. 17-41 show configurations of the present invention for a
coaxial cable. The center conductor 32 of the cable 30 is connected
to the signal conduction point 4 of the electrical device 2 by the
compliant signal contact 12. As shown in FIGS. 17-19, the signal
contacts 12 are surrounded by a number of ground contacts 14 that
connect either the conducting anchor block 16 or the cable ferrule
330 to the device in a pattern that closely mimics the impedance
environment of the cable 30, e.g. 50 ohms, 75 ohms, 85 ohms, or 100
ohms. The impedance of the system can be changed by changing the
position of the ground contacts 14 with respect to the signal
contact 12 or by changing the insulating material, thereby changing
the dielectric constant of the material or both. Changing the
locations of the ground contacts with respect to the signal contact
is like changing the diameter of the ground shield on a coaxial
cable from 2.5 mm for 50-ohm cable to 6 mm for 75-ohm cable.
Alternatively, the dielectric may be changed so that the lower the
dielectric constant of the material, the closer the ground shield
can be to the cable signal conductor while the cable maintains the
same impedance environment.
When there are two or more cables 30 and a conductive anchor block
16, there may be ground contacts 14 that are "shared" between
cables 30. For example, in the coaxial structure of FIG. 19, the
ground contact 14' between the two signal contacts 12 is common to
both cables. The common ground contact can also been seen in FIG.
20, where the right side ground contact 14 is between the ground
shields 36 of adjacent cables 30. Another example is shown in the
twin-axial structure of FIG. 48, where the ground contacts 14'
between the two signal contacts of adjacent cables 30 are common to
both cables.
As shown in FIGS. 20-22, the skewed coil contact 42 is captured in
a through aperture 44 in the plate 18. The aperture 44 has a larger
center section 48 that narrows to a smaller block opening 46b at
the side adjacent to the anchor block 16 and to a smaller device
opening 46a at the other end. In one configuration, shown in FIGS.
20 and 21, the plate 18 has two mirror image sheets 50 where each
sheet 50 has one opening 46a, 46b and a half of the center section
48. The contact 42 is placed in the center section 48 of one sheet
50 and the sheets 50 are sandwiched together to capture the contact
42. In another configuration, shown in FIG. 22, the plate 18 has a
base sheet 52 with one of the openings 46a and the center section
48 and a top sheet 54 with the other opening 46b. The contact 42 is
placed in the center section 48 and the sheets 52, 54 are
sandwiched together, capturing the contact 42 within the aperture
44. The length of the contact leads 56 is such that the leads 56
extend from the openings 46a, 46b.
An alternative configuration is shown in FIG. 23. Rather than a
wider center section with smaller openings at both ends, the center
section 48 extends its full width from the block opening 46b to a
smaller device opening 46a on the opposite side of the plate 18
from the anchor block 16. When the plate 18 is mounted to the
anchor block 16, as described below, the contact 12, 14 is secured
in the plate 18. If all of the apertures 44 are of this design, the
plate 18 does not have to have two sheets 50. Since the contacts
12, 14 can be installed from the block opening 46b, the plate 18
can be a single sheet.
Because of the very small size of the wire used to make the skewed
coil contact 42, the contact area between the skewed coil signal
contact 12 and the cable center conductor 32 is small. This can
cause a capacitive reactance at the interface of the contact leg 56
and the cable center conductor 32 which can cause reflections at
high frequencies. To help alleviate this problem, the through
aperture 44 is wide for its entire length, as in FIG. 24. Each end
has an annular shoulder 60. A pair of conductive bosses 62 with a
shoulder 64 fit into the aperture 44, with the shoulders 60, 64
retaining the bosses 62 in the aperture 44. The boss 62 has a
through hole 66 that narrows from the center of the aperture 44 to
a smaller device opening 46a and a smaller block opening 46a at the
ends through which the contact leads 56 extend. The bosses 62
increase the effective area of the contact lead 56.
In FIG. 24, the conductive bosses 62 are shown spaced from each
other, that is, they do not touch each other. In an alternative
configuration, the conductive bosses 62 are made long enough to
touch each other, either around the entire circumference of the
aperture 44 or only portions of the circumference, such as with
extending fingers. This can alleviate the potential problem of the
conductive bosses 62 acting as a capacitive device if the contact
12 does not short them together.
Optionally, in any skewed coil contact configuration, after the
contact 42 is installed, the remaining space of the aperture 44 is
filled with a compliant, electrically conductive elastomer that
adds resiliency and aids in electrically shorting the coil
loops.
As shown in FIG. 25, the fuzz button contact 70 is cylindrical. The
plate 18 has a through aperture 72 that is narrower at the center
than the ends, as at 74. The contact 70 is forced into the aperture
72. The length of the contact 70 is such that the ends 76 extend
from the plate 18.
As shown in FIGS. 26-28, the conductive rubber contact 100 for the
signal contact 12 can be cylindrical with a centrally-located
annular depression 102. The plate 18 has a through aperture 104
with a centrally-located annular protrusion 106. The rubber contact
100 is radially compressed and placed in the aperture 104 such that
the protrusion 106 fits into the depression 102 to retain the
contact 100 in the aperture. The length of the contact 100 is such
that the ends 108 extend from the plate 18.
The conductive rubber contact for the ground contact 14 can be of
the same structure as the signal contact 12. Alternatively, the
conductive rubber contact 112 for the ground contact 14 is
circular, surrounding the signal contact 12, as in FIG. 27. The
conductive rubber contact 112 has a circular top sheet 114 adjacent
to the anchor block 16 and a circular bottom sheet 116 for
interfacing to the device 2. The two sheets 114, 116 are
electrically connected by a plurality of plugs 118 in through
apertures 120 in the plate 18. The number of plugs 118 can vary by
application and is typically four or eight spaced evenly around the
signal contact 100. As with the signal contact 100, each plug 118
has an annular depression 122 that fits into an annular protrusion
124 for retention. Optionally, knobs 126 extending from the sheets
114, 116 into depressions 128 in the plate 18, as in FIG. 28, help
retain the sheets 114, 116 in position.
In FIGS. 29-32, the contact 150 is a strip of conductive material
in a C shape. The contact 150 can be formed by chemical etching, by
stamping and forming, or by any other means practical. The contact
150 is captured in a through aperture 160 in the plate 18. In their
quiescent state, the contact leads 152 extend outwardly of the
plate 18, as in FIG. 31. When the anchor block 16 is attached to
the plate 18, the upper lead 152 deforms toward the plate 18 and
into a depression 156, as in FIG. 32, thereby providing electrical
contact by the signal contact 12 to the center conductor 32 and by
the ground contacts 14 to the anchor block 16. When the assembly is
connected to the device 2, the lower lead 154 deforms toward the
plate 18 and into a depression 158.
An alternate terminator assembly 10 using the anchor block of FIG.
14 is shown in FIGS. 33 and 34. The compliant contacts 12, 14 fit
into apertures 44 in the plate 18. The signal contact 12 presses
against the center conductor 32 that has been bisected
longitudinally and dressed.
The electrical connection 80 between the center conductor 32 and
the signal contact 12 and the electrical connection 82 between the
anchor block 16 and the ground contacts 14 are compression
connections. With the contacts 12, 14 installed in the plate 18,
the plate 18 is mounted to the anchor block 16 with mechanical
attachments 28, such as screws, rivets, and the like. Installing
the plate 18 forces the end of the signal contact 12 against the
end of the center conductor 32 and forces the ends of the ground
contacts 14 against the anchor block 16.
Alternatively, the electrical connection 80 between the center
conductor 32 and the signal contact 12 is a solder connection while
the electrical connection 82 between the anchor block 16 and the
ground contacts 14 is a compression connection.
Alternatively, as shown in FIG. 35, the end of the center conductor
32 is formed into a compliant spring like the skewed coil contact,
as at 84. The plate 18 is configured like that of FIG. 23, where
the block opening 46b is the same size as the center section 48.
The plate 18 is assembled without a signal contact 12 and, when the
plate 18 is installed, the end of the center conductor 32 extends
through the device opening 46a. The electrical connection 82
between the anchor block 16 and the ground contacts 14 is a
compression connection.
The plate 18 can be either insulating or conductive. FIGS. 20-35
show an insulating plate 86. The insulating plate 86 is made of a
non-electrically-conductive material, preferably a plastic, so as
to not electrically couple the signal contacts 12 and ground
contacts 14.
A conductive plate 88, shown in FIGS. 36-41, is preferably composed
of an electrically-conductive metal. Alternatively, the conductive
plate is composed of a non-conductive material plated with a
conductive coating. The conductive plate 88 electrically couples
the ground contacts 14, thus providing more precise impedance
matching to the signal contact 12. The signal contact 12 is
insulated from the conductive plate 88 by an insulating centering
plug 90 which prevents the signal contact 12 from electrically
shorting to the conductive plate 88. The plug 90 includes the
through aperture 44, the device opening 46a, the anchor block
opening 46b, and the center section 48. The plug 90 is typically
made from an insulating plastic.
The plug 90 may be press fit into a through hole 92 in the
conductive plate 88 or it may be bonded into the hole 92 with an
adhesive. Alternatively, as shown in FIG. 38, the plug 90 is has
two parts 94, each of which fit into one plate sheet 50. Mating
shoulders 96, 98 retain the plug parts 94 in the plate sheets
50.
FIGS. 39-41 show a configuration where the signal contact aperture
44 is within a conductive boss 190, like that of FIG. 24. The boss
190 is surrounded by an insulating annulus 192 that insulates the
conductive boss 190 from the conductive plate 88. The annulus 192
can be composed of any dielectric material, but a better match can
be had if the annulus 192 is composed of the same material as the
cable dielectric 34.
Alternatively, the signal contact 12 can be insulated from the
conductive plate 88 by a non-conductive coating such as powder
coating. In this case the signal contact aperture may be made
larger such that the coating reduces the aperture size to the
appropriate size for use. As with the plug 90, the impedance of the
system can be changed by either changing the thickness of the
coating or by changing the coating material, thereby changing the
dielectric constant of the material.
FIGS. 42-55 show configurations of the present invention for a
twin-axial cable. The twin-axial configurations are illustrated
using the skewed coil contacts. The present invention contemplates
that any of the various available compliant contacts, including
those described with reference to the coaxial cable assembly, can
be used with twin-axial cables, as well as cables with more than
two center conductors.
The center conductors 32 of the cable 30 are connected to the
signal conduction points 4 of the electrical device 2 by the
compliant signal contacts 12. As shown in FIGS. 47-52, the signal
contacts 12 are surrounded by a number of ground contacts 14 in a
pattern that closely mimics the impedance environment of the cable
30, e.g. 50 ohms, 75 ohms, 85 ohms, or 100 ohms. As described above
with reference to the coaxial cable assembly, the impedance of the
system can be changed by changing the position of the ground
contacts 14 with respect to the signal contact 12 or by changing
the insulating material, thereby changing the dielectric constant
of the material or both.
As with the coaxial cable configurations, the plate 18 can be
either insulating or conductive. FIGS. 47-49 show an insulating
plate 86 and FIGS. 50-55 show a conductive plate 88. With the
conductive plate 88, the signal contacts 12 are insulated from the
conductive plate 88 by an insulating plug 90 which prevents the
signal contacts 12 from electrically shorting to the conductive
plate 88. The plug 90 has two apertures 44, one for each signal
contact 12. As described above with reference to FIGS. 36-38, the
twin-axial cable plug 90 can be anchored by any conceivable means,
such as by press fit, as shown in FIG. 52, adhesive, or
capture.
FIGS. 53-55 show an alternative to the configuration of FIGS.
50-52. This configuration does not use ground contacts, only signal
contacts 12. The ground signal conducts directly through the
conductive plate 88 to the device 2.
The present specification describes a number of different compliant
contacts that can be used in the present invention. These are
merely examples. The present invention contemplates that any form
of compliant contact that has the appropriate characteristics for
the particular application can be used. In addition, the present
specification contemplates that different types of contacts can be
use in the same assembly. For example, a skewed coil contact can be
used as the signal contact and a circular conductive rubber contact
can be used as the ground contact.
The present invention produces a controlled-impedance, compliant
cable to device interface which can be less than 1 mm thick (the
length of the compliant contacts 12, 14) and mimics the
controlled-impedance environment of the cable 30, thereby ensuring
the highest possible signal rates through the termination.
The present invention can also produce a controlled-impedance
device to device interface because the cables 30 can have
terminators 10 at both ends.
When working with very high frequencies, for example, frequencies
in the Gigahertz range and above, electrical cable lengths are very
critical. In order to maintain phase synchronization between
signals on different cables, the cables must have as close to the
exact same length, mechanically and electrically, as is practical.
The present specification describes a method and apparatus for
assembling cables 202 to the anchor block 200 so that the cables
202 are the same length to within a very small tolerance, on the
order of 0.001 inch for cables 202 that are 6 inches long from the
cable connector 204 to the block face 206. The present method can
be used for cables of any length. Longer cables result in larger
tolerances. At a given temperature, a cable length can be
controlled to within 0.03% to 0.05% of the cable's overall
length.
To facilitate the method, a soldering fixture 210 is used. The
fixture includes a frame 212, a connector jig 214, a block jig 216,
and legs 218. FIGS. 56-58 illustrate a fixture 210 for use with 16
cables 202 and a rectangular solid anchor block 200 for two rows of
cables 202. The fixture 210 can be modified for a different number
of cables, different shape anchor block 200, different cable
connector 204, different cable length, etc.
The frame 212 is generally rectangular and stands vertically. The
connector jig 214 is mounted to the lower cross piece 222 of the
frame 212 inside the frame 212. The block jig 216 is mounted to the
upper cross piece 224 of the frame 212 outside of the frame 212.
Four legs 218 extend from the bottom corners of the frame 212 in
generally opposite directions. The legs 218 are angled from the
frame 212 by at least 10.degree. from horizontal so that they
prevent the frame 212 from falling over but allow the user to tilt
the frame 212. The preferred angle is about 20.degree. so that the
frame can be tilted between 70.degree., 90.degree., and 110.degree.
from vertical to facilitate use, as described below. The present
invention contemplates that the angle of the legs 218 can vary from
application to application.
The fixture 210 locks the connector 204 of each cable 202 at a
fixed distance away from where the other end of the cable 202 will
be soldered to the anchor block 200. The connector jig 214 locks
the connectors 204 and can be designed appropriately for any
particular type of connector 204. FIG. 59 shows a portion of a
connector jig 214 for locking coaxial connectors. There is a
connector securement 226 for each cable 202. The securement 226
includes a channel 228 with an upper narrow section 230 for the
cable 202 and a lower wide section 232 for the connector 204. The
narrow section 230 is defined by outwardly extending upper fingers
234. The wide section 232 is defined by outwardly extending lower
fingers 236. When there is upward tension on the cable 202, the
connector 204 catches on the bottom surface 238 of the upper
fingers 234.
Because the distance (pitch) between cables 202 at the anchor block
200 is smaller than the diameter of the connectors 204, the cables
202 cannot be secured parallel to each other to achieve equal
length. To solve this problem, the connector jig 214 locks the
connectors 204 in an upwardly open arc 240 so that the cables 202
are the same length to the anchor block 200.
As shown in FIG. 60, the block jig 216, a C-shaped component, is
secured by screws 250 to the top surface 244 of the upper cross
piece 224 of the frame 212, straddling a C-shaped cutout 246. The
anchor block 200 is secured by screws 242 to the block jig 216 such
that the anchor block face 206 is up and straddles the cutout 246,
which provides access to the cable holes 248 in the anchor block
200.
A tensioning plate 252 is mounted to the upper cross piece 224.
There are threaded holes 254 at each end of the tensioning plate
252 into which the jack screws 256 are threaded. The tensioning
plate 252 is placed over the anchor block face 206 and the jack
screws 256 are turned into the holes 254 so that the tensioning
plate 252 rests on the anchor block face 206. The tensioning plate
252 has a cable hole 258 for each cable 202 that is aligned with
the anchor block cable hole 248 for the same cable 202. Optionally,
the tensioning plate 252 is machined out above the anchor block
200, as at 270, to facilitate access to the face 206.
Each cable 202 is trimmed so that it is at least 1.4 inches longer
that the assembled length of the cable 202. The cable 202 is
stripped at the end so that the length from the connector 204 to
the stripped portion remains constant. The non-stripped portion of
the cable 202 extends into the anchor block hole 248 approximately
0.06 inches.
As shown in FIG. 61, after trimming, each cable 202 is fed through
the hole 248 in the anchor block 200 corresponding to the connector
securement 228 into which the cable connector 204 will be placed
and through the corresponding cable hole 258 in the tensioning
plate 252.
As shown in FIG. 62, a coil spring 260 is placed on each cable 202
and a collar 262 is placed over each cable 202 so it touches the
spring 260. Alternatively, the spring 260 and collar 202 can be a
unified component. A set screw 264 is turned into the collar 262 to
tightly secure the collar 262 to the cable 202.
The connectors 204 are placed into the corresponding securement 228
and the two jack screws 256 are tightened until the cables 202 have
enough tension to be pulled against their securements 226, making
sure that the cables 202 are straight between the connector 204 and
the anchor block 200 with no kinks or bends. Optional stops 266
prevent the jack screws 256 from being tightened too much. In the
illustrated configuration, the stops 266 are spacers 292 on the
jack screws 256 between the tensioning plate 252 and the jack screw
heads 294, as shown in FIG. 63.
The springs 260 independently keep each cable 202 tight so that the
distance from the connector 204 anchor block face 206 remains
consistent for all of the cables 202.
Each cable shield 208 is soldered to the anchor block 200 such that
the solder flows into the hole 248. The angled legs 218 allowing
the user to tilt the fixture 210 permit easier access to each side
of the anchor block 200 for soldering.
After the solder and anchor block 200 have cooled sufficiently, the
jack screws 256 are loosened until tension on the springs 260 is
released. The collars 262, springs 260, and tensioning plate 252
are removed. The anchor block 200 is removed from the frame 212 and
the connectors 204 are removed from the connector jig 214. The
excess cable is cut off.
Next, the anchor block face 206 is finished smooth and evenly flat.
There are a number of ways known in the art to accomplish this,
including sanding, milling, planing, skiving, and broaching. Once
the cables 202 are secured in the anchor block 200, any conceivable
method can be used to dress the face 206 of the anchor block 200
which achieves the desired surface finish and/or planarity.
Thus it has been shown and described a controlled-impedance cable
termination and a method and apparatus for attaching
controlled-impedance cables to the termination. Since certain
changes may be made in the present disclosure without departing
from the scope of the present invention, it is intended that all
matter described in the foregoing specification and shown in the
accompanying drawings be interpreted as illustrative and not in a
limiting sense.
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