High frequency electrical connector

A high frequency electrical connector including a plurality of parallel contacts, a plurality of terminals, and conductors interconnecting the contacts to the terminals in a manner such that signals flowing through proximate contacts are transmitted in opposite directions to reduce near-end crosstalk.

This invention relates generally to electrical connectors and, more 
particularly, to an electrical connector for use in the transmission of 
high frequency signals. 
Data communication networks are being developed which enable the flow of 
information to ever greater numbers of users at ever higher transmission 
rates. A problem is created, however, when data is transmitted at high 
rates over a plurality of circuits of the type that comprise multi-pair 
data communication cable. In particular, at high transmission rates, each 
wiring circuit itself both transmits and receives electromagnetic 
radiation so that the signals flowing through one circuit or wire pair 
(the "source circuit") may couple with the signals flowing through another 
wire pair (the "victim circuit"). The unintended electromagnetic coupling 
of signals between different pairs of conductors of different electrical 
circuits is called crosstalk and is a source of interference that often 
adversely affects the processing of these signals. The problem of 
crosstalk in information networks increases as the frequency of the 
transmitted signals increases. 
In the case of local area network (LAN) systems employing electrically 
distinct twisted wire pairs, crosstalk occurs when signal energy 
inadvertently "crosses" from one signal pair to another. The point at 
which the signal crosses or couples from one set of wires to another may 
be 1) within the connector or internal circuitry of the transmitting 
station, referred to as "near-end" crosstalk, 2) within the connector or 
internal circuitry of the receiving station, referred to as "far-end 
crosstalk", or 3) within the interconnecting cable. 
Near-end crosstalk ("NEXT") is especially troublesome in the case of 
telecommunication connectors of the type specified in sub-part F of FCC 
part 68.500, commonly referred to as modular connectors. The EIA/TIA of 
ANSI has promulgated electrical specifications for near-end crosstalk 
isolation in network connectors to ensure that the connectors themselves 
do not compromise the overall performance of the unshielded twisted pair 
interconnect hardware typically used in LAN systems. The EIA/TIA Category 
5 electrical specifications specify the minimum near-end crosstalk 
isolation for connectors used in 100 ohm unshielded twisted pair Ethernet 
type interconnects at speeds of up to 100 MHz. 
While it is desirable to use modular connectors for data transmission for 
reasons of economy, convenience and standardization, such connectors 
generally comprise a plurality of electrical contacts and conductors that 
extend parallel and closely spaced to each other thereby creating the 
possibility of excessive near-end crosstalk at high frequencies. 
High speed data transmission cable typically comprise four circuits defined 
by eight wires arranged in four twisted pairs. The cable is typically 
terminated by modular plugs having eight contacts, and specified ones of 
the four pairs of the plug contacts are assigned to terminate respective 
specified ones of the four cable wire pairs according to ANSI/EIA/TIA 
standard 568. In particular, the standard 568 contact assignment for the 
wire pair designated "1" is the pair of plug contacts located at the 4-5 
contact positions. The cable wires of the pair designated "3" are, 
according to standard 568, terminated by the plug contacts located at the 
3-6 positions which straddle the "4-5" plug contacts that terminate wire 
pair "1". Near-end crosstalk between wire pairs "1" and "3" during high 
speed data transmission has been found to be particularly troublesome in 
connectors that terminate cable according to standard 568. 
When crosstalk occurs between electrically distinct circuits that are 
separated by a distance of much less than one wavelength, signal energy is 
transferred from one circuit to another either through inductive coupling, 
capacitive coupling, or a combination of the two. For Category 5 
interconnects, the shortest wavelength of interest is 3 meters, 
corresponding to the highest frequency of operation, 100 MHz. Since 
connector contact spacing in Category 5 connectors is much less than 3 
meters, capacitive (electric field) and/or inductive (magnetic field) 
coupling will be responsible for measurable crosstalk within the 
connector. 
Capacitive coupling will dominate when: 
1) source circuits switch large voltages very quickly (large dv/dt) and/or 
operate at relatively high impedance levels (&gt;&gt;1k.OMEGA.); 
2) source and/or victim circuits have large surface areas (wide, long 
conductors); and 
3) source and victim circuits are closely spaced and separated by 
dielectrics (non-conductors) that increase mutual capacitance between the 
source and victim circuits. 
Inductive coupling will dominate when: 
1) source circuits switch large currents very quickly (large di/dt) and/or 
operate at relatively high impedance levels (&lt;&lt;100.OMEGA.); 
2) source and/or victim circuits enclose large loop areas; and 
3) source and victim circuits are closely spaced and have their current 
loops oriented along parallel axes. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide new and 
improved connectors for use in data transmission at high frequencies. 
Another object of the present invention is to provide new and improved high 
frequency connectors which reduce near-end crosstalk. 
Still another object of the present invention is to provide new and 
improved modular connectors which reduce near-end crosstalk. 
A still further object of the present invention is to provide new and 
improved high frequency electrical connectors which reduce near-end 
crosstalk and which are simple and inexpensive in construction. 
Yet another object of the present invention is to provide new and improved 
modular jacks which reduce near-end crosstalk when connected to modular 
plugs that terminate high speed data transmission cable according to 
ANSI/EIA/TIA standard 568. 
Briefly, these and other objects are attained by providing an electrical 
connector comprising a plurality of substantially parallel contacts, a 
plurality of terminals, such as pin-type terminals, and means for 
interconnecting the contacts to respective terminals such that signals 
transmitted through at least one pair of adjacent contacts flow in 
opposite directions. Signal flow in opposite directions through proximate 
contacts creates self-cancelling magnetic and inductive fields which 
reduce near-end crosstalk. The means for interconnecting the contacts to 
the terminals comprise one or more first conductors which interconnect 
first end regions of respective one or more first contacts to respective 
one or more terminals, and one or more second conductors which 
interconnect second end regions opposite from the first end regions of the 
first contacts of respective one or more second contacts which are 
proximate to the first contacts to a respective one or more terminals. 
In a preferred embodiment, the connector comprises a modular jack having a 
plurality of contact/terminal wires, each of which defines a contact, a 
pin-like terminal, and a conductor portion interconnecting the contact and 
terminal. A first set of the contact/terminal wires are configured to 
define a first set of jack contacts that "face rearwardly", i.e., the free 
ends of the jack contacts face toward the closed end of the jack with the 
respective jack terminals being interconnected to these contacts at the 
region of the open end of the jack so that signals transmitted through the 
contacts of the first set flow toward the open end of the jack. On the 
other hand, a second set of the contact/terminal wires are configured to 
define a second set of jack contacts that "face forwardly", i.e., the free 
ends of the jack contacts face toward the open end of the jack with the 
respective jack terminals being interconnected to these contacts at the 
region of the closed end of the jack so that signals transmitted through 
the contacts of the second set flow toward the closed end of the jack, 
i.e., in a direction substantially opposite to the direction in which the 
signals flow through the contacts of the first set. 
In the case of an eight contact, eight position modular jack adapted for 
connection to a modular plug terminating an eight wire cable in accordance 
with the wire-contact assignments specified by ANSI/EIA/TIA standard 568, 
near-end crosstalk is reduced to a maximum extent when the jack contacts 
in positions 3 and 5 are forward facing contacts while the jack contacts 
in positions 1, 2, 4 and 6-8 are rearward facing contacts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein like reference characters designate 
identical or corresponding parts throughout the several views, FIG. 1a 
illustrates a jack 10 in accordance with the invention for coupling high 
speed communication hardware 12 to a printed circuit board 14 via a high 
speed communication cable 16 terminated by a modular plug 18. The jack 10 
has a receptacle 20 adapted to receive the modular plug 18. Coupling of 
the hardware 12 to the printed circuit board 14 is made more convenient by 
the use of connectors 10 and 18 having standard modular features of the 
type specified in sub-part F of F.C.C. part 68.500. The connector 10 is 
mechanically mounted to the printed circuit board 14 by means of posts 22 
which are received in corresponding openings 23 in the printed circuit 
board. 
As noted above, problems arise in the use of conventional modular jacks for 
high speed data transmission because of the necessary close spacing 
between the jack contacts and other electrical conductors of the 
connector. More particularly, modular jacks generally include a plurality 
of closely spaced, substantially parallel wire contacts adapted to be 
engaged by blade-like contacts of the modular plugs. The wire contacts are 
coupled to pin-like terminals of the jack, generally by length portions of 
common contact/terminal wires, which in turn are connected to the printed 
circuit. When a modular plug is inserted into the receptacle of a modular 
jack, the contact blades of the plug engage respective wire contacts of 
the jack. The signals flowing between the wire contacts and the pin-like 
terminals of each transmission circuit create electromagnetic and 
inductive fields which undesirably couple to other circuits through 
adjacent jack contacts resulting in near-end crosstalk. 
In accordance with the present invention, the wire contacts of the 
connector are interconnected to respective pin-like connector terminals in 
a manner such that the signals that flow through the contacts of at least 
one pair of adjacent contacts flow in opposite directions, rather than in 
the same direction as is conventional. In this manner, electromagnetic and 
inductive fields created by the opposite signal flows in adjacent and/or 
proximate contacts tend to substantially cancel each other thereby 
substantially reducing signal coupling in the connector, i.e. 
substantially decreasing near-end crosstalk. 
Referring to FIGS. 1b and 2-5, a jack 10 in accordance with a preferred 
embodiment of the invention comprises a dielectric housing 24 and a 
plurality of conductive contact/terminal wires 110a and 110b. 
Contact/terminal wires 110a, of which there are six, are configured to 
form a first set of rearward facing contacts 26a and associated pin-like 
terminals 25a while contact/terminal wires 110b, of which there are two, 
are configured to form a second set of forward facing contacts 26b and 
associated pin-like terminals 25b. In other words, the free ends 27a of 
contacts 26a are situated near and face toward the closed end of jack 
receptacle 20 while the free ends 27b of contacts 26b are situated near 
and face toward the entrance opening 21 of receptacle 20. The contacts 26a 
and 26b are substantially parallel and extend obliquely through jack 
receptacle 20 between upper positions proximate to the forward entrance 
opening 21 and lower positions at the rear of the receptacle. Jack 10 
includes eight contacts 26 (six contacts 26a and two contacts 26b) and is 
constructed specifically for use with an eight contact modular plug 
terminating a four wire pair transmission cable with wire-contact 
assignments as specified by ANSI/EIA/TIA standard 568. However, it is 
understood that a connector in accordance with the principles of the 
invention may include more or less than eight contacts. 
The contact/terminal wires 110a and 110b are shaped and associated with 
jack housing 24 as described below so that when the contacts 26a and 26b 
are engaged by the contact blades 19 (FIG. 2) of the modular plug 18, the 
signals flow through the first rearward facing contacts 26a to their 
associated terminals 25a in a direction (designated by arrow 29a in FIG. 
2) opposite to the direction in which the signals flow through the second 
forward facing contacts 26b toward their associated terminals 25b 
(designated by arrow 29b in FIG. 2). 
The rearward facing contacts 26a alternate in position with the forward 
facing contacts 26b in accordance with an arrangement which has been found 
to maximize isolation of near-end crosstalk when jack 10 is coupled to a 
modular plug whose contacts are assigned to terminate the cable wires 
according to ANSI/EIA/TIA standard 568. Twisted wire pair "3" assigned to 
plug/jack contacts at positions "P3" and "P6" is typically used to 
transmit and receive information in such cable. The jack contacts that are 
situated at positions "P4" and "P5" and which are engaged by corresponding 
plug contacts that terminate the twisted wire pair designated "1" are 
rearward and forward facing contacts 26a and 26b respectively. The jack 
contacts situated at positions "P3" and "P6" (that straddle the contacts 
in positions "P4" and "P5") and which are engaged by corresponding plug 
contacts that terminate the twisted wire pair "3" are forward and rearward 
facing contacts 26b and 26a respectively. The jack contacts situated at 
positions "P1" and "P2" and which are engaged by corresponding plug 
contacts that terminate twisted wire pair "2" are both rearward facing 
contacts 26a as are the jack contacts situated at positions "P7" and "P8" 
that are engaged by corresponding plug contacts that terminate twisted 
wire pair "4". It has been found that with this particular positional 
arrangement of the eight forward facing (F) and rearward facing (R) jack 
contacts, i.e., RRFRFRRR, optimum isolation for source/victim twisted wire 
pairs "1" and "3" (which generally generate the greatest NEXT) is achieved 
when coupled to an eight position modular plug whose contacts are assigned 
to terminate 4 twisted wire pair cable according to ANSI EIA/TIA standard 
568. This is accomplished without introducing additional NEXT failures 
associated with the jack contacts at positions "P4"-"P5" (wire pair "1") 
and the jack contacts at positions "P1"-"p2" (wire pair "2") or "P7"-"P8" 
(wire pair "4"). 
Jack housing 24 comprises a contact housing part 28 and an outer housing 
part 30 formed of suitable plastic material which together define the 
receptacle 20 for receiving a modular plug of the type designated 18 in 
FIG. 1a. Contact housing part 28 has a generally L-shaped configuration 
including a back portion 34 and a frame-shaped top portion 36 extending 
from the top of the back portion 34 in a cantilever fashion. A first set 
of four tapered parallel bores 40 extend through the rear part of the back 
portion 34, and a second set of four tapered parallel bores 40 extend 
through the front part of back portion 34. As seen in FIGS. 2 and 3, the 
central upper region of the front part of back portion 34 is notched out 
at 41 so that the two of the four bores 40, designated 40', that extend 
through the front part of back portion 34 at locations corresponding to 
contact positions 3 and 5, open onto an upwardly facing surface 42 
situated at about the mid-height of back portion 34. Thus, six full height 
bores 40 open onto the top surface of back portion 34 while two bores 40' 
open onto the surface 42 situated at the mid-height of the back portion. 
As best seen in FIG. 3, the frame-shaped top portion 36 includes a pair of 
elongate side portions 44 projecting forwardly from the upper end of back 
portion 34 and a transversely extending front portion 46 extending 
transversely between side portions 44. Guide channels 48 are formed on the 
upper surface of front portion 46 at locations corresponding to contact 
positions P1, P2, P4 and P6-P8, i.e., at locations corresponding to the 
positions of rearward facing contacts 26a and curve around to the lower 
surface of the front portion 46 with the curved portion recessed behind 
the front surface 46' of front portion 46. As seen in FIGS. 2 and 3, the 
transverse front portion 46 has upwardly facing stop surfaces 50 formed at 
locations corresponding to contact positions P3 and P5, i.e., at locations 
corresponding to the positions of forward facing contacts 26b. 
Each of the six "rearward" contact/terminal wires 110a is formed of an 
appropriate resilient conductive material, such as phosphor bronze, and is 
shaped to include a length portion defining a rearwardly facing contact 
26a, a length portion defining an associated pin-like terminal 25a and a 
length portion defining a conductor 112a interconnecting the contact 26a 
from its front end 26a' to terminal 25a. The rearward contact/terminal 
wires 110a are assembled to contact housing part 28 as follows. Each 
pin-like terminal 25a is positioned in a respective one of the six full 
height bores 40 and has a length such that a bottom length portion 25a' 
projects out from the bottom of bore 40 for connection to the printed 
circuit. Each conductor 112a extends longitudinally from the upper end of 
a respective terminal 25a across the open space defined by frame-shaped 
top portion 36 and is received in a respective one of the guide channels 
48 formed in front portion 46. Each contact 26a extends rearwardly in a 
downward direction from the curved front end of a respective conductor 
112a situated in a guide channel 48 and terminates at the free end 27a. 
Each of the two "forward" contacts/terminal wires 110b is also formed of 
resilient conductive material and is shaped to include a length portion 
defining forwardly facing contact 26b, a length portion defining an 
associated pin-like terminal 25b and a length portion defining a conductor 
112b interconnecting the contact 26b from its rear end 26b' to terminal 
25b. The forward contact/terminal wires 110b are assembled to contact 
housing part 28 as follows. Each pin-like terminal 25b is positioned in a 
respective one of the two shorter bores 40' and has a length such that a 
bottom length portion 25b' projects out from the bottom of bore 40' for 
connection to the printed circuit. Each conductor 112b extends 
longitudinally from the upper end of a respective terminal 25b for a 
relatively short distance. Each contact 26b extends forwardly in an upward 
direction from the front end of a respective conductor 112b and terminates 
at the free end 27b which is shaped to overlie a respective one of the 
stop surfaces 50 (FIG. 2) formed in front portion 46. 
The outer housing part 30 comprises a unitary member formed by opposed top 
and bottom walls 68 and 70 and opposed side walls 72 defining an interior 
space between them. Posts 22 project downwardly from the bottom wall 70 
for connecting the jack to the printed circuit board. A pair of flanges 74 
project laterally from side walls 72 for facilitating mounting of the jack 
to a chassis, if desired. 
A wall 76 extends upwardly from bottom wall 70 and divides the interior of 
the outer housing part 30 into a forward space comprising receptacle 20 in 
which the modular plug is received and a rearward space for receiving the 
back portion 34 of contact housing part 28. A plurality of spaced 
partitions 78 are formed at the upper end of wall 76 that define eight 
guide slots 80 between them and which terminate at their upper ends at a 
distance spaced from the top wall 68 of outer housing part 30. 
In assembly, the contact housing part 28 and associated contact/terminal 
wires 110a and 110b are inserted into the outer housing part 30 from its 
rear end. Rails 82 on the contact housing part are received in 
corresponding channels (not shown) formed in the outer housing part. 
During insertion, the six rearward facing contacts 26a are aligned with 
and received in the guide slots 80 corresponding to jack contact positions 
1, 2, 4 and 6-8, while the two forward facing contacts 26b are aligned 
with and received in the guide slots 80 corresponding to jack contact 
positions 3 and 5. The partitions 78 serve to precisely position the 
rearward and forward facing contacts 26a and 26b and prevent them from 
contacting each other during operation. A locking shoulder 86 formed on 
each side of the back portion 34 of contact housing part 28 snaps into 
engagement with a corresponding shoulder (not shown) in the outer housing 
part 30 to lock the contact housing part and associated contacts to the 
outer housing part. 
Referring to FIGS. 1 and 2, when the two plug contact blades 19b at 
positions P3 and P5 of modular plug 18 engage the respective two forward 
facing contacts 26b at those positions, signals are transmitted from the 
contact blades through the forward facing contacts 26b to the associated 
terminals 25b in the direction of arrow 29b, i.e., downwardly towards the 
back portion 34 of contact housing part 28. On the other hand, still 
referring to FIGS. 1 and 2, when the six contact blades 19a at positions 
P1, P2, P4 and P6-P8 of modular plug 18 engage the respective six rearward 
facing contacts 26a at those positions, signals are transmitted from the 
contact blades through the rearward facing contacts 26a to the associated 
terminals 25a in the direction of arrow 29a, i.e. upwardly and away from 
the back portion 34 of contact housing part 28. It is seen that the 
signals transmitted through rearward facing jack contacts 26a flow in the 
opposite direction to that in which the signals transmitted through 
adjacent forward facing contacts 26b flow. In this manner, adjacent first 
and second contacts 26a and 26b create electromagnetic fields which tend 
to cancel each other thereby reducing near-end crosstalk. Crosstalk is 
further reduced by the fact that the first and second conductor planes 
containing the first and second conductor portions 116a and 116b of wires 
110a and 110b are spaced from each other. 
The arrangement of forward and rearward facing contacts described above, 
namely RRFRFRRR will essentially compensate for a split twisted pair where 
the normal pairing is split up and the individual wires are paired with 
wires from another pair. However, the invention is not limited to such an 
arrangement, and alternate wiring configurations will dictate notating 
forward and rearward facing contacts for optimum cancellation or 
compensation effects. For example, other arrangements of forward and 
rearward facing contacts in a connector in accordance with the invention 
include RFRFRRRR and FRFRRRRR. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. The invention may be applied 
in connectors other than of a type adapted for use with cables whose wires 
are assigned to contacts in a manner other than as specified by EIA/TIA 
standard 568 of ANSI. Thus, the principles of the invention will be 
utilized in any connector in which signals flow through a set of at least 
one contact in one direction and in the opposite direction through a set 
of at least one other contact proximate thereto. For example, the 
arrangement of forward and rearward facing contacts may vary from that 
shown and described, e.g., and/or signals may flow from a forward facing 
contact in one direction to and through a rearward facing contact in 
another direction. Connectors in accordance with the invention may be 
other than of a type adapted for connection to printed circuit boards, and 
other configurations of conductors, terminals and contacts are possible in 
accordance with the invention. Accordingly, it is understood that other 
embodiments of the invention are possible in the light of the above 
teachings.