U.S. patent number 3,828,303 [Application Number 05/292,856] was granted by the patent office on 1974-08-06 for coaxial connector.
This patent grant is currently assigned to Bunker Ramo Corporation. Invention is credited to Pasquale Ralph Petti, Norbert J. Sladek, William Max Erich Zerlin.
United States Patent |
3,828,303 |
Sladek , et al. |
August 6, 1974 |
COAXIAL CONNECTOR
Abstract
This invention relates to a simple, field installable, low cost,
miniature, push-pull, quick connect/disconnect electrical connector
system having a VSWR (voltage standing wave ratio) of less than
1.35 for all signal frequencies from 0.1 to 6 GHz useful for
interconnecting coaxial cables having a characteristic impedance in
the range of 50 ohms. The connector system is made up of a plug
member and a jack member each comprising but three basic parts. The
first part of each member is comprised of an integral tubular
member of relatively soft electrically conductive material. The
second part of each member is in turn comprised of a dielectric
insert which is held in its respective tubular member by staking or
rolling a reduced section of its tubular member's wall. The front
portion of the jack member fits into the front portion of the plug
member and through the action of an internal shoulder within the
plug member a predetermined spacing between the dielectric inserts
held by the plug and jack members is established when the members
are fully mated. Each dielectric insert is in turn bored to receive
one of two matable pin-like electrical contacts each of which
comprises the third part of its respective connector member. Each
contact has a hollow rear portion which may be crimped to the
center conductor of a respective coaxial cable and thereafter
inserted into the bore of its respective insert and retained
therein. The outer conductor of each coaxial cable may be crimped
around a reduced section of the rear portion of each connector by
means of a crimping ferrule. The aforesaid fixed spacing between
the dielectric inserts acts to produce a high impedance relative to
the impedance afforded by the dielectric inserts to effect the
afore-referenced VSWR of less than 1.35 for signal frequencies
between 0.1 and 6 GHz.
Inventors: |
Sladek; Norbert J. (Fairfield,
CT), Petti; Pasquale Ralph (Waterbury, CT), Zerlin;
William Max Erich (Newtown, CT) |
Assignee: |
Bunker Ramo Corporation (Oak
Brook, IL)
|
Family
ID: |
23126506 |
Appl.
No.: |
05/292,856 |
Filed: |
September 28, 1972 |
Current U.S.
Class: |
439/585;
333/33 |
Current CPC
Class: |
H01R
9/0518 (20130101) |
Current International
Class: |
H01R
9/05 (20060101); H01r 017/12 () |
Field of
Search: |
;333/33 ;339/177 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Electro-Technology, "Burndy Connectors" December, 1962, page 183,
copy in 339-177 R..
|
Primary Examiner: Zugel; Francis K.
Assistant Examiner: Staab; Lawrence J.
Attorney, Agent or Firm: Bair; D. R. Kransdorf; R. J.
Arbuckle; F. M.
Claims
What is claimed is:
1. An improved low cost quick connect/disconnect electrical
connector having a VSWR of less than 1.35 for all signal
frequencies from 0.1 to 6 GHz, including a plug member and a jack
member which, when in axial alignment with one another, may be
pushed together or pulled apart to interconnect or disconnect two
coaxial cables each of substantially the same characteristic
impedance, the coaxial cables having an inner conductor and an
outer conductor separated by a body of dielectric material, said
plug member comprising a first, a second and a third plug
parts;
said first plug part having a front, central and rear axially
extending portions contiguous with one another and being formed of
an integral tubular body of relatively soft resilient electrically
conductive material, said tubular body having an axial bore
extending through the rear portion thereof, said bore having an
internal diameter substantially equal to the outer diameter of the
dielectric body of one coaxial cable to permit said dielectric body
to be snugly received within the rear portion of said tubular body,
a section of said rear portion of said body contiguous with the
rear extremity thereof being reduced sufficiently to accept a
crimping ferrule for holding the outer conductor of said coaxial
cable against the outer periphery of said reduced rear seciton and
to form an external laterally extending shoulder against which a
crimping ferrule may be longitudinally seated and restrained from
axial movement toward the front portion of said tubular body;
said tubular body having a first counterbore extending through the
central portion thereof, said first counterbore having an internal
diameter greater than said bore in said rear portion to form a
first internal laterally extending shoulder located at the rear
extremity of said first counterbore and the front extremity of said
bore, at least a portion of said central portion being reduced on
its outer periphery near said rear portion to form a first wall of
said relatively soft material which is defined between the inner
surface of said first counterbore and the outer surface of said
reduced central portion and which is inwardly deformable by
externally staking or rolling said wall;
said tubular body having a second counterbore extending through the
front portion thereof, said second counterbore having a diameter
larger than said first counterbore to form a second internal
laterally extending shoulder located at the rear extremity of said
second counterbore and the front extremity of said first
counterbore against which the front extremity of a jack member may
abut when said plug and said jack member are pushed together and
mated, the internal diameter of said second counterbore and the
external diameter of said front portion forming a resilient second
wall of said conductive material longitudinally slit and formed to
grip said jack member when inserted therein by spring action;
said second plug part comprising a cylindrical insert of resilient
dielectric material having a diameter substantially equal to that
of the first counterbore of said first plug part and positioned
within the central portion of said first plug part against said
first internal laterally extending shoulder, said insert having a
length less than the axial length of said first plug part central
portion and retained therein by deformation of said first wall into
gripping relation with the outer periphery of said insert, said
insert having a central bore for receiving said third plug
part;
said third plug part comprising an electrically conductive contact
having a hollow rear portion for accepting and retaining the inner
conductor of one of said coaxial cables and a front end portion
formed to pass through from the rear of said first plug part and be
axially restrained from rearward movement within the bore of said
second plug part after the inner conductor of said coaxial cable
has been retained in said hollow rear portion thereof;
the jack member of said connector system comprising a first, second
and third jack parts;
said first jack having a front and a rear axially extending
portions contiguous with one another and being formed of an
integral tubular body of relatively soft resilient electrically
conductive material, said tubular body having an axial bore
extending through the rear portion thereof, said bore having an
internal diameter substantially equal to the outer diameter of the
dielectric body of another coaxial cable to permit said dielectric
body to be snugly received within the rear portion of said tubular
body, a section of said rear portion of said body contiguous with
the rear extremity thereof being reduced sufficiently to accept a
crimping ferrule for holding the outer conductor of said coaxial
cable against the outer periphery of said reduced rear section and
to form an external laterally extending shoulder against which a
crimping ferrule may be longitudinally seated and restrained from
axial movement toward the front portion of said body;
said tubular body having a counterbore extending through the front
portion thereof, said counterbore having an internal diameter
greater than said rear portion bore to form a first internal
laterally extending shoulder located at the rear extremity of said
counterbore and the front extremity of said bore, at least a
portion of said front portion being reduced on its outer periphery
near said rear end portion to form a first wall of said relatively
soft material which is defined between the inner surface of said
counterbore and the outer surface of said reduced front portion and
which is inwardly deformable by externally staking or rolling said
wall;
said second jack part comprising a cylindrical insert of resilient
dielectric material having a diameter substantially equal to that
of said first jack part counterbore and positioned within said
counterbore against the laterally extending shoulder therein, said
insert having a length less than the axial length of said first
jack part front portion and retained therein by deformation of said
wall into gripping relation with the outer periphery of said
insert, said insert having a central bore for receiving said third
jack part;
said third jack part comprising an electrically conductive contact
member matable with the contact member carried by said plug member
and having a hollow rear portion for accepting and retaining the
inner conductor of the other of said coaxial cables and a front end
portion formed to pass through from the rear of said first jack
part and be axially restrained from rearward movement therein
within the bore of said second jack part after the inner conductor
of said coaxial cable has been retained in said hollow rear portion
thereof, the spacing between the front surfaces of the dielectric
inserts in said plug member and said jack member when said members
are mated forming an impedance which is greater than the
characteristic impedance of said coaxial cables with the dielectric
constant of said inserts and the lengths thereof forming impedances
which are less than the characteristic impedance of said coaxial
cables whereby said plug member and said jack member when mated
provide a connector system having a VSWR of less than 1.35 for all
signal frequencies from 0.1 to 6 GHz.
2. A connector system according to claim 1 wherein said second plug
part and said second jack part have substantially the same
dimensions.
3. A connector system according to claim 1 wherein said first wall
of said first jack part is substantially the same thickness as the
depth of said second internal laterally extending shoulder of said
first plug part with the outer diameter of a section of the front
portion of said first jack part being substantially equal to the
inner diameter of the second counterbore of said first plug
part.
4. A connector system according to claim 1 wherein said front end
portion of said electrically conductive contact retained by said
plug member extends beyond said second internal laterally extending
shoulder within said first plug part but is contained substantially
wholly within said front portion of said first plug part and
wherein the extremity of said front end portion of said contact
member carried by said second jerk part extends beyond the front
extremity of the dielectric insert forming said second jack part
but is contained substantially wholly within said front end portion
of said first jack part.
5. A connector system according to claim 1 wherein the outer
periphery of said first jack part is provided with a tapered
surface extending rearwardly from the front extremity of the front
portion thereof to a position forward of the forward extremity of
said second jack part to aid in the insertion thereof into the
front portion of said first plug member.
6. A connector system according to claim 1 wherein the
characteristic impedance of the coaxial cables to which said
connector members are to interconnect is substantially 50 ohms
while the impedance formed by the spacing of said dielectric
inserts are in the range of 62 ohms and the impedance formed by
each of said dielectric inserts is in the range of 44 ohms.
7. A connector system according to claim 1 wherein the volume
embraced between said dielectric inserts is substantially 40 per
cent and the volume occupied by said dielectric inserts is
substantially 60 per cent respectively of the total volume embraced
within said connector system between said first internal shoulder
of said first plug part and said first internal shoulder of said
first jack part when said plug and jack member are fully mated.
Description
This invention relates to an electrical connector adapted for
mating a pair of coaxial cables and more particularly to an
inexpensive quick connect/disconnect coaxial connector with minimum
reflections (and thus low voltage standing wave ratio, VSWR) at
frequencies up to six GHz.
BACKGROUND OF THE INVENTION
The characteristic impedance of a coaxial transmission line is
normally about 50 ohms. In order to avoid impedance mismatches, the
impedance through all sections of a connector joining two coaxial
lines should thus also be substantially 50 ohms. Where impedance
mismatches do occur through sections of a coaxial connector,
reflections may occur, adversely effecting the voltage standing
wave ratio (VSWR) of the connector and resulting in attenuation of
any signal passing through the connector. The attenuation caused by
an impedance mismatch increases significantly as the frequency of
the line signal increases. Thus, an impedance mismatch which may be
acceptable in a connector intended for low frequency applications,
becomes unacceptable when an attempt is made to utilize the
connector with higher frequency lines.
Heretofore, the requirement of obtaining a substantially uniform 50
ohm impedance through a coaxial connector has required fairly
careful design and manufacture. The resulting connector has
therefore been relatively expensive. Lower cost connectors, such as
standard phono-connectors, have heretofore been limited to
applications with line frequencies no greater than 0.5 GHz.
However, even these phono-connectors are relatively expensive, and
in applications such as in mobile radio where frequencies above 0.5
GHz are utilized, these connectors are clearly inadequate.
A need therefore exists for a simple, inexpensive radio frequency
coaxial connector which provides minimum reflections and thus
acceptable VSWR and performance at frequencies up to six GHz.
Normally, a connector will be considered to have acceptable VSWR
and performance if VSWR is less than 1.35 over the entire frequency
range that the connector is intended to operate in (for example,
0.1 to 6 GHz). Such a connector should also provide for quick
connect and disconnect, while still providing reliable mating.
SUMMARY OF THE INVENTION
This invention therefore provides an electrical connector adapted
for mating a pair of coaxial lines which connector includes a plug
and a jack. The plug has a male center contact, a cylindrical outer
contact projecting beyond the center contact and having at least
one tine biased toward the center of the contact, and an insert of
an insulating material mounted in the outer contact and having an
axial opening in which the center contact is supported. The jack
has a female center contact dimensioned to have the male contact
fit snugly therein, a cylindrical outer contact dimensioned to fit
into the plug outer contact with the tine in pressure engagement
with the outer wall thereof, and an insert of insulating material
mounted in the outer contact and have an axial opening in which the
center contact is supported. The plug and jack are dimensioned to
provide a small air gap between their inserts of insulating
material when the plug and jack are fully mated. The impedance of
the air gap is slightly greater than the characteristic impedance
of the lines while the impedance of the inserts are slightly less
than the characteristic impedance of the lines. This results in the
vector sum of the reflections due to the insert and gap inpedances
in a mated connector pair being very small (i.e., a VSWR of less
than 1.35). The balancing of impedance mismatches in conjunction
with the minimizing of the length of the impedance mismatch area
permits an inexpensive connector to be provided which connector
achieves the required performance perameters.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of preferred embodiments of the invention as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional side view of the plug portion of a connector
of a preferred embodiment of the invention.
FIG. 2 is a front view of the plug shown in FIG. 1.
FIG. 3 is a sectional side view of the jack portion of a connector
of a preferred embodiment of the invention.
FIG. 4 is a front view of the jack shown in FIG. 3
FIG. 5 is a sectional side view of the connector of the preferred
embodiment of the invention showing the plug and jack in a mated
condition.
FIG. 6A is a sectional side view of the center contact portion of
the jack for an alternative embodiment of the invention.
FIG. 6B is a portional sectional side view of the center contact
portion of the plug for the embodiment of the invention shown in
FIG. 6A.
DETAILED DESCRIPTION
Referring now to FIGs. 1 and 2, it is seen that the plug 10 for the
connector of a preferred embodiment of the invention consists of a
one-piece tubular body member 12 of a conducting material, an
insert 14 of an insulating material staked at four places 16 (only
two of which are shown in FIG. 1) near the center of body 12, and a
center contact 18 of a conducting material supported in an axial
bore 20 formed through insert 14. The forward or contact portion 22
of body 12 is slotted to provide a pair of upper and lower sections
each of which extends for approximately 120.degree., and a pair of
tines 26 which are each biased toward the center of body. The
leading surface of each section 24 and tine 26 is slightly flared
to assist in the insertion of a mating jack. The rear portion 28 of
body 12 is tapered and, as may be seen in FIG. 5, is adapted to fit
between the outer conductor 32 and insulator 30 of a coaxial cable
or line 34. Portion 28 has a bore 36 sized to accept the cable
insulation 30. Bore 36 terminates in a counterbore 38 in which is
positioned insert 14. Counterbore 38 terminates in a second
counterbore 40 in the outer contact region 22 of the body. A
shoulder 42, the function of which will be described later, is
formed at the juction between counterbores 38 and 40. A crimp
ferrule 44 is provided to secure outer conductor 32 of the cable to
portion 28 of body 12.
Center contact 18 has a rear opening 46 in which center conductor
48 of cable 34 is either soldered or crimped. The center contact is
then passed through the rear of the connector and forced through
opening 20 to position the contact as shown. A barb 49 is formed
near the center of contact 18 to prevent the contact from being
withdrawn once it has been so positioned (i.e., to captivate the
contact in the connector). The forward contact portion 50 of the
contact 18 has a tapered bullet-shaped leading edge for easy
insertion into a mating female contact and is, as best seen in FIG.
2, cross-slotted. This permits the contact to compress slightly
when being inserted into a mating female contact to provide good
pressure contact therewith.
Jack 52 (FIGS. 3 and 4) also has a one-piece body 54, an insulating
insert 56, a center contact 58 and a crimp ferrule 60. Body 54 has
a cylindrical forward contact portion 62 with a tapered leading
surface for insertion into contact portion 22 of plug 10 and an
extending rear or ferrule portion 64 with a tapered trailing edge
which, as is seen in FIG. 5, is adapted to be fitted between the
insulation and outer conductor of a coaxial cable 34. Body 54 also
has a bore 66 with an enlarged counterbore 68 in its forward
portion. Insert 56 is positioned in the rear of counterbore 68 and
is held therein by being staked at four points 70 (only two of
which are shown in FIG. 3). Insert 56 has an axial bore 72 in which
is supported center contact 58. Center contact 58 is in the form of
a hollow tube having a pair of pierced tabs 74 which serve to
captivate the contact in the jack once the contact has been passed
through the rear of insert 56. As with the plug, center conductor
48 of the cable is secured in contact 58 by either soldering or
crimping and outer conductor 32 is secured to portion 64 of body 54
by crimping ferrule 60 over the outer conductor in standard
fashion.
All parts of plug 10 and jack 52 are of a conductive material such
as brass except inserts 14 and 56 which are of an insulating
material such as polytetrafluoroethylene (also known by the
trademark Teflon). The brass parts may be coated with nickel to
reduce corrosion.
Referring now to FIG. 5, it is seen that when the parts are fully
assembled, the leading edge of jack outer contact 62 bottoms on
shoulder 42 of plug 10. This leaves an air gap 76 in the mated
connectors between insert 56 and insert 14 which is equal to the
width of counterbores 68 and 38 not filled by the respective
inserts. For preferred embodiments of the invention, the insert
fills about 60 percent of the counterbore and the air gap the
remaining 40 percent. However, since the total length of each
counterbore, for the preferred embodiment of the invention, is less
than a quarter of an inch, the total length of the impedance
mismatch is relatively short. The impedance of the air section is
roughly 62 ohms and the impedance of the insert section (assuming
Teflon as the insert material) is roughly 44 ohms. As a result, the
vector summation of the reflections through the mismatch area is
small, the reflections introduced in one mismatched section tending
cancel those introduced in the other mismatched section with little
substantial net adverse effect resulting on the applied signal.
Connectors built utilizing the design described above have been
found to have a VSWR of less than 1.20 (in most instances less than
1.15) over a frequency range from 0.1 to 6 GHz. Thus, these
connectors are, in accordance with standards previously mentioned,
adapted for providing acceptable performance at frequencies up to
six GHz.
FIGS. 6A and 6B illustrate the center contact portions of a jack
and plug respectively of an alternative embodiment of the
invention. Female center contact 80 of the jack 54' for the
alternative embodiment of the invention, is machined from rod stock
rather than being a hollow tube. This contact has a rear opening 82
formed in it which is adapted to have the center conductor 48 of a
coaxial cable 34 secured therein in the same manner that a
conductor is secured in opening 46 of contact 18. Contact 80 also
has a forward opening 84 which is slotted so as to be adapted for
expansion, and a barb or ring 86 formed around its circumference
which barb is identical to and performs the same functions as barb
49. In the alternative, barb 86 may be of reduced size and
positioned further back on contact 80 so that it remains within
insert 56 when the contact is properly positioned. With either
configuration, the barb tends to hold the contact against movement
in jack 54'.
The center contact 88 of plug 12' is identical to center contact 18
of plug 12 (FIG. 1) except that forward contact portion 90 is in
the shape of a solid tapered bullet rather than a slotted tapered
bullet. Contact portion 90 is sized so as to cause a slight
expansion of opening 84 when contact portion 90 is fitted therein
assuring a good pressure fit between contacts 80 and 88.
The connectors described above are adapted to be quickly connected
by merely pushing the plug and jack together and to be quickly
disconnected by pulling these two elements apart. No predetermined
orientation of parts, screwing, clamping, or other operations are
required. Tines 26 being in pressure contact with the outer wall of
contact area 62 of jack 52 assure a good physical and electrical
connection of the outer conductors while the compression of slotted
bullet contact 50 on entering tubular contact 58 or the expansion
of slotted contact when contact enters it assures good physical and
electrical contact under pressure of the inner contacts. There is a
wiping action on both the inner and outer conductors during connect
and disconnect which removes contaminents and further assures good
electrical contact. Barb 49 and tabs 74 or barb 86 restrict
movement of their center contacts in the connectors to within about
16 mils minimizing the adverse VSWR effects of such movement.
Since the plug and the jack of the connector of this invention have
only three parts each, plus a crimp ferrule, which parts are
assembled using simple and straightforward techniques, both the
material and assembly costs for the connector of this invention are
minimized. An extremely low cost, simple, quick connect/disconnect,
high performance RF coaxial connector has thus been provided.
While the description above has been with reference to preferred
embodiments of the invention, it is apparent that some
modifications in the details of the design may be made. For
example, the number of tines 26 may be varied from as little as one
to as many as four or five. Similarly, a single cut rather than a
crosscut may be utilized for the tip 50 of contact 18. Thus, while
the invention has been shown and described above with reference to
preferred embodiments, the foregoing and other modifications may be
made in the connector of this invention by those skilled in the art
while still remaining within the spirit and scope of the
invention.
* * * * *