A coaxial connector has a board mount end (14) for mounting on a circuit board, with a standoff (70) thereat to lie above circuit board traces and allow the passage of wash fluid that washes away soldering flux etc., which minimizes a change in impedance along the standoff to reduce signal losses. The standoff, which is connected to the outer contact (24) of the connector, has a circular inner surface (90) that faces the pin part (34) of the center contact, and which has segments (81-84) which, together, extend at least about 180.degree. about the pin. The outer contact which surrounds a mount-end insulator (62) and the inner contact, has a slot (120) at the mount end to enable the installation of the center contact.

BACKGROUND OF THE INVENTION 
One type of coaxial connector has a board mount end which is mounted on a 
circuit board, with both the inner and outer coaxial contacts soldered 
thereat to conductive traces on an upper surface of the board. The inner 
conductor commonly includes a pin part that extends into a plated hole in 
the circuit board, while the outer conductor includes a plurality of 
posts, such as four of them, that extend into plated holes in the circuit 
board. The outer conductor includes a standoff with a passage leading to 
the pin part, to keep the outer conductor from touching a trace on the 
circuit board that extends to the pin-receiving hole, and to pass cleaning 
fluid that washes away solder flux and the like, especially at the solder 
joint where the pin part is soldered to a trace. There is a sudden change 
in impedance along the short height of the standoff, as from a desired 
characteristic impedance of perhaps 50 ohms to perhaps 130 ohms. This 
large change in impedance results in reflections at very high frequencies, 
resulting in losses and distortion. It would be desirable if the 
characteristic impedance increased a minimum amount along the standoff. 
The coaxial connector commonly has a mating end, opposite the board-mount 
end, which extends perpendicular to the board-mount end. Two separate 
insulators are installed in the two perpendicular ends. However, a single 
inner conductor must be installed, which is difficult to do because of the 
90.degree. bend. Many prior coaxial connectors of this type form the outer 
conductor with a window that aids in installing the bent inner conductor, 
with a bendable door to close the window. However, such a door is commonly 
formed in a die cast part of the outer conductor, and it is not uncommon 
for the door to break off after having been bent back into place. A 
construction of the outer conductor or enclosure of a coaxial connector 
which facilitated installation of a 90.degree. bend center conductor, 
would be of value. 
SUMMARY OF THE INVENTION 
In accordance with one embodiment of the present invention, a coaxial 
connector is provided which reduces the characteristic impedance at a 
standoff lying at the board-mount end of the connector, and which 
facilitates installation of the central contact of the connector within 
the outer contact. The standoff, which is part of the outer contact of the 
connector, has a bottom for lying on the circuit board, with the standoff 
having a primarily cylindrical inner surface that surrounds the pin part 
of the center contact and that is coaxial with it. 
The outer contact has a mating end that extends perpendicular to the mount 
end, and the inner contact also requires a substantially 90.degree. bend. 
To facilitate insertion of the inner contact, the mount end of the outer 
contact is provided with a vertical slot on a side thereof opposite the 
mating end. 
The novel features of the invention are set forth with particularity in the 
appended claims. The invention will be best understood from the following 
description when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a coaxial connector 10 with a mating end or end portion 
12 for mating to another connector such as one that has been terminated to 
an end of a coaxial cable, and an opposite board mount end or end portion 
14 for mounting on a circuit board 16. The coaxial connector has its 
mating and board mount ends extending along perpendicular axes 20, 22. The 
connector includes an outer contact or enclosure 24 formed by a die cast 
part 26 and a bent sheet metal part 28. The inner conductor 30 is formed 
of a single piece of metal with a mating end 32 and with a board mount end 
or pin part 34. The circuit board 16 has a plurality of conductive traces 
including a signal trace 40 and a ground trace 42, each trace leading to 
at least one plated circuit board hole. The pin part is designed to fit 
into a first plated through hole 44 and to be soldered to the signal trace 
40. The outer contact or conductor 24 includes four mount posts 51-54 that 
can project into corresponding plated-through holes 56 in the circuit 
board that extend to the ground trace 42, with each pin or post being 
soldered to the area of the trace immediately around each hole. 
FIG. 2 shows additional details of the construction of the coaxial 
connector 10. The connector includes a mate end insulator 60 and a mount 
end insulator 62. The diameters of the insulators 60, 62, and the smaller 
inside diameter at 64 in the outer contact at the 90.degree. bend, are 
chosen to maintain a characteristic impedance of close to 50 ohms along 
the entire connector. Where there are large changes in characteristic 
impedance, high frequency signals are reflected and the VSWR (voltage 
standing wave ratio) is increased, resulting in loss of signal power and 
signal distortions. 
The board-mount end 14 of the metal enclosure or outer conductor 24 
includes a short column or standoff 70 that spaces a flat lower end 72 of 
the enclosure from the circuit board 16. The standoff provides one or more 
horizontal (parallel to the planes of the circuit board) passages through 
itself leading to the pin part 34 of the inner contact 30. The passages 
prevent direct contact between the outer conductor 24 and the signal trace 
or traces 40 (FIG. 1) on the circuit board. The passages also permit the 
ready flow of washing fluid that is used to wash away solder flux used in 
soldering the pin part 34 to the signal circuit board trace, since solder 
flux can be corrosive. 
The insulators 60, 62 are of sold material which has a dielectric constant 
much higher than that of air. For example, Teflon can be used which has a 
dielectric constant of about 2.5. To maintain a 50 ohm characteristic 
impedance along the length of the connector, the inner surface 74 of the 
outer contact is made larger to account for the higher dielectric constant 
of the insulator 62, except at the bend 64. Since air has a dielectric 
constant of 1.0, maintenance of a characteristic impedance not too much 
greater than 50 ohms along the short length of the standoff 70 would 
require that the standoff lie closely around the pin part 34. This cannot 
be easily accomplished because a large space is required for installing 
the mount-end insulator 62. However, it is desirable to maintain a 
relatively low characteristic impedance thereat. 
As shown in FIG. 5, applicant constructs the column or standoff 70 to 
minimize the characteristic impedance along the vertical height of the 
standoff, while providing horizontal passages for circuit board traces and 
for the rapid and effective flow through of wash out fluid. The standoff 
is formed in a plurality of segments 81-84. Each segment has an inner 
surface 90 which is circular as viewed along the second axis 22. The 
circular inner surfaces 90 provide a uniform impedance around the pin part 
34 of the inner conductor, with the characteristic impedance being as low 
as possible, considering the need to install the mount end insulator 62. 
Gaps or passages 92 between the segments 81-84 enable the signal circuit 
board trace 40 (FIG. 1) to lie under the connector without touching the 
outer conductor 24. 
The provision of four gaps between the four segments, enables the connector 
with four mounting posts 51-54 to be mounted at any of four possible 
orientations on the circuit board without altering the positions of the 
signal circuit board trace. The four gaps 92 also enable the rapid pass 
through of wash out fluid that is used to wash away soldering flux and 
other debris that could corrode or damage the solder joints. Often, such 
fluid is directed to flow in one direction across the circuit board, and 
the four gaps permit the rapid flow through of wash out fluid regardless 
of the direction in which fluid flows past the standoff 70. Applicant 
prefers to provide cutaways 94 on the radially outer side of each segment 
81-84 leave gaps 92 of relatively short length. Each of the segments 81-84 
with a circular inner surface 90 is connected to a corresponding mounting 
post 51-54 through a coupling portion 100 of the standoff. The coupling 
portions and the segments 81-84 preferably have flush flat lower faces 
102, to enable the direct flow of current between the coupling segments 
81-84 and the mounting posts 51-54 without requiring currents to zig or 
zag, which could result in reflections that deteriorate the signal. In 
soldering the outer contact to the grounded traces, the solder fillets 
preferably solder to the couplings 102 as well as to the posts 51-54. The 
four segments and the four gaps are preferably identical and uniformly 
spaced about the second axis 22. 
FIG. 3 is a bottom view of the standoff 70, showing that the segment 81-84 
occupy about 180.degree. of the circle about the axis 22. Applicant 
prefers that the segments occupy a total of at least one-third of a 
circle, or at least 120.degree., about the second axis 22, where the 
segments have inner surfaces that all lie coaxial with the pin part 34 and 
its axis 22. 
FIG. 6 shows another embodiment of the invention, where a standoff 110 is 
provided on a separate member 112 that is mounted on the posts 114 of the 
outer conductor. The separate member, which becomes part of the outer 
contact, allows installation of the insulator 62 and the subsequent 
mounting of the member 112 on the post. This allows inner surfaces 116 of 
segments to lie closer to the pin part 34 to achieve a lower 
characteristic impedance along the standoff. However, it should be 
understood that these types of coaxial connectors are sold at a low cost 
on the order of magnitude of one-dollar each, and the need for an 
additional member 112 that must be manufactured and mounted can add to the 
cost. The use of a separate member 112 would be useful for especially high 
frequencies such as those on the order of magnitude of 4 GHz and higher, 
where reflections from a change in impedance are more deleterious. 
The assembly of the connector 10 of FIG. 2 involves first installing the 
inner contact 30 within the outer one 24. Because of the 90.degree. bend 
at 124, this can be difficult to do. Applicant accomplishes this by 
providing a slot 120 in the mount end of the die cast part 26, the slot 
extending vertically (when the bottom 72 of the mount end is horizontal) 
and lying at a side of the second axis 22 opposite the mating end 12 of 
the connector. When the inner conductor 30 is to be installed, it is held 
to assume the orientation shown at 30A, wherein its approximately 
90.degree. bend at 124A lies against the inside of the die cast part 126 
that extends along the first axis 20, while the pin part at 34A extends 
into the slot 120. After the inner conductor 30 is installed, the 
insulators 60, 62 and sheet metal part 28 are installed. 
FIGS. 7 and 8 show a plug coaxial connector 130 which is substantially 
identical to the connector of FIGS. 1-6, except that the inner contact 132 
has a socket mating end 134 instead of a pin mating end. 
In a connector that applicant has designed, the connector had an overall 
horizontal length as shown in FIG. 2, of 0.88 inch (22 mm), the pin part 
34 had a diameter of 0.03 inch (0.76 mm), and the standoff 70 had a height 
of about 0.02 inch (0.5 mm). Because of the very small size of the 
connector, and the corresponding very small height of the standoff, the 
provision of four passages for the traces and for the flow through of wash 
out fluid, are important. Applicant has measured that the characteristic 
impedance at the standoff was reduced from about 130 ohms in a prior art 
construction wherein the standoff included two parts with surfaces 91 as 
shown in FIG. 3, to 90 ohms, resulting in a significant reduction in VSWR. 
The coaxial connectors can be part of a larger connector device that may 
include noncoaxial contacts. 
Thus, the invention provides a coaxial connector of the type that mounts on 
a circuit board, where a standoff that provides one or more passages 
between the board and the outer coaxial conductor is constructed to 
minimize a change in impedance thereat, and the connector is constructed 
to facilitate assembly. The standoff, which has a bottom for lying on the 
circuit board, extends at least partially around the center conductor pin 
part that projects into the circuit board, with the standoff having a 
surface of circular shape coaxial with the pin part as viewed along the 
second axis of the coaxial connector. The standoff preferably includes a 
plurality of segments that together surround more than 120% of the second 
axis along which the pin part extends, with each segment having a cutaway 
radially outside, and having a coupling extending between the segment and 
a corresponding mounting post, with the coupling and the segment having 
flat flush bottom surfaces. The outer conductor includes a die cast part 
at the mount, with a largely cylindrical inner surface for receiving an 
insulator, but with the inner surface having a groove or slot that aids in 
installing the inner contact. 
Although particular embodiments of the invention have been described and 
illustrated herein, it is recognized that modifications and variations may 
readily occur to those skilled in the art, and consequently, it is 
intended that the claims be interpreted to cover such modifications and 
equivalents.