1. Field of the Invention
The present invention is directed towards connection systems for communicating electrical signals, and more particularly, to a high-reliability, matched impedance, shielded-pair interconnection system adapted for high speed data transmission up to and exceeding one gigabit per second for protocols such as Ethernet, 1394, USB, 1553, Fibre Channel, VME, Can-Buss, J1708, and the like.
2. Description of Related Art
With the increasing demand and complexity of modern electronic systems in high reliability applications such as military and aerospace, there is a continuing need to incorporate more electronic equipment into a confined space, while at the same time ensuring reliability in harsh environments. In such applications, connection systems provide a critical communication link between physically separated electronic devices. These connection systems have to satisfy many competing requirements. They should be capable of withstanding a rugged environment that includes vibration, wide temperature swings, moisture, and exposure to hazardous materials and chemical contaminants. They should also be compact to permit many interconnections to be made within a small area. And, they should have the highest quality electrical characteristics, with matched impedance, very low signal loss, and minimal crosstalk.
High reliability connection systems are often used to facilitate 100Base T and 1000Base T Ethernet applications such as those found in commercial avionics systems. Additional applications, for example, include aircraft data networks, in-flight entertainment systems (IFE) and other mil-aero networking applications where Gigabit Ethernet IEEE 802.3, Fibre Channel XT11.2, 1394, USB, 1553, Fibre Channel, VME, Can-Buss, J1708 or other multi-gigabit connectivity architecture is required. In such communication networks in which it is desirable to transfer data at high speeds over distances up to one-hundred meters, it is known to use balanced matched impedance copper cabling. The copper cables are connected to the various interfaces in a communications network using plug-in modular connectors. A conventional cable used to transfer data includes an insulating cable sheath that contains pairs of copper wires. The wires are twisted together in order to reduce crosstalk, which is a form of signal degradation that results when the signal on one wire is inductively coupled onto another adjacent wire. The Ethernet protocol uses four pairs per channel, and each pair needs to be shielded from the other pairs to preclude cross-talk between the pairs. Furthermore, when the channel is used in a full duplex manner, i.e., to support simultaneous bidirectional communications, it is also necessary to prevent disturbance by near end crosstalk and far end crosstalk from the other pairs. Thus, in a given Ethernet channel, there are six disturbing sources per pair. Consequently, both the position of the wires and the components of the modular connector all play a crucial role in preventing signal degradation.
Two commercially known modular connectors for Ethernet applications are the RJ-45 and the Quadrax contact. The RJ-45 is an eight-wire connector used commonly to connect computers onto local-area networks (LAN), especially in building applications. The connector or jack includes a generally plastic body having eight metal contacts that connect to four pairs of wires that terminate inside the jack. To attach the RJ-45 connector to a cable, about two inches of the cable sheath is stripped off exposing the four pairs of twisted wires. Each pair is untwisted and the wires are flattened out and trimmed down to approximately one-half an inch in length. These wires are inserted into the jack and connected to the metal contacts. A device such as a crimping tool is used to press down the contacts onto the wires, thereby terminating the wires in the RJ-45 connector.
Despite the prevalence and low cost of the RJ-45 connector, it also has many limitations. One drawback is that the wires have to be untwisted in order to be inserted into the jack. By untwisting the wires, even if over a small length of cable, the wires become susceptible to signal degradation due to crosstalk. Another drawback of the RJ-45 connection is that the connector is not environmentally sealed. The wires that terminate at the end of the jack are exposed to the environment and can become damaged by fluctuating temperature conditions and contaminants resulting in a poor electrical connection. Yet another drawback is that the contacts and other components of the connector are not repairable. If there is any damage to a contact, the entire connector must be removed and replaced. For these and other reasons, the RJ-45 does not meet military and aerospace specifications (Mil-DTL-38999, which has a Mil-STD-1560 insert performance requirement). Moreover, the contacts are not designed to meet vibration and shock requirements set out by these specifications. Furthermore, some wire designs require maintaining a matched impedance parallel geometry.
In lieu of the RJ-45, the Quadrax contact is used for many military or other high-reliability applications. Quadrax contacts are a multi-signal contact system employing two pairs for use with quad-axial cables. The contacts feature a one-piece dielectric design that helps simplify the termination process. The Quadrax contact has a cylindrical metal shell that is swaged to the braid of wires over a crimp support sleeve. The shell encloses four inner contacts that are intended to connect to two pairs of wires. Thus, two Quadrax contacts are required in order to connect four pairs of wires or one gigabit Ethernet cable. The two Quadrax contacts are contained in a size 17 shell, having an outside diameter of 1.415 inches, which is very bulky. The Quadrax contacts provide a significant improvement over the RJ-45 in terms of ruggedness and cross-talk reduction, but are not without other disadvantages. Even though the four pins are shielded overall, each pair is not shielded from the other. Additionally, the pins are prone to bending. Like the RJ-45, the inner contacts of the Quadrax contact are not repairable. Replacing the contacts requires cutting through the outer contact, which makes the assembly on the inner contacts non-repairable. Thus, the entire Quadrax contact needs to be replaced if there is any damage to the inner contacts.
For each of the foregoing reasons, a need exists for an improved matched impedance, shielded-pair interconnection system for high speed data transmission up to and exceeding one gigabit per second for harsh operating environments
The present invention satisfies the need for an improved interconnection system by providing a connector that carries plural matching pairs of conductors in a compact package in which each pair is isolated from each other to reduce cross-talk.
In an embodiment of the invention, a connector provides for attachment to a cable having a plurality of wires arranged in matched pairs. The connector comprises a housing and a connector insert located within the housing and having a plurality of contact cavities extending in an axial direction entirely therethrough. The connector insert further includes a substantially centrally located elongated opening extending in the axial direction from a proximal end thereof at least partially through the connector insert. The plurality of contact cavities are arranged substantially symmetrically with respect to the elongated opening. A conductive post is inserted into the elongated opening of the connector insert. The conductive post has elongated edges that provide shielding between respective pairs of the plurality of contact cavities. A follower is coupled to the conductive post. The follower has a plurality of passageways adapted to communicate respective ones of the matched pairs of wires to respective ones of the pairs of contact cavities. The follower thereby provides physical separation between the respective pairs of wires. The connector further comprises a plurality of electrical contacts inserted into the respective ones of the plurality of contact cavities. The plurality of electrical contacts are adapted to be coupled to respective ones of the plurality of wires.
The connector may be adapted to provide a socket (female) connection or a pin (male) connection. For a pin connection, the connector insert may further include a plurality of pins coupled to respective ones of the plurality of contact cavities at a distal end of the connector insert. The plurality of contact cavities may be arranged in a generally circular pattern or in a generally rectangular pattern. In a preferred embodiment, the plurality of contact cavities further comprises four pairs of contact cavities. The housing further comprises a boot portion adapted to enclose the follower, the boot portion having an opening permitting passage of the cable therethrough while maintaining an environmental seal around the cable. A separator may be coupled to the follower, the separator providing plural channels for guiding respective ones of the matched pairs of wires. The follower may be adapted to be symmetrically coupled to a braided shield material of the cable.
In another embodiment of the invention, a connector provides for attachment to plural cables with each having a plurality of wires arranged in matched pairs. The connector comprises a housing and a plurality of modules arranged within the housing. Each module includes a connector insert disposed within the housing and having a plurality of contact cavities extending in an axial direction entirely therethrough. The connector insert further has a substantially centrally located elongated opening extending in the axial direction from a proximal end thereof at least partially through the connector insert. The plurality of contact cavities are arranged substantially symmetrically with respect to the elongated opening. The module further comprises a conductive post inserted into the elongated opening of the connector insert. The conductive post has elongated edges that provide shielding between respective pairs of the plurality of contact cavities. The module further comprises a follower coupled to the conductive post, the follower having a plurality of passageways adapted to communicate respective ones of the matched pairs of wires to respective ones of the pairs of contact cavities. The follower provides shielding between the respective pairs of wires.
For each module, the plurality of contact cavities may be arranged in a generally circular pattern or in a generally rectangular pattern. In a preferred embodiment, the plurality of contact cavities of each module further comprises four pairs of contact cavities. Each module may be adapted to provide a socket (female) connection or a pin (male) connection. For a pin connection, the connector insert may further include a plurality of pins coupled to respective ones of the plurality of contact cavities at a distal end of the connector insert.
A more complete understanding of the matched impedance, shielded pair interconnection system will be afforded to those skilled in the art of data signal communications, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings that will first be described briefly.
The invention satisfies the need for a matched impedance shielded pair interconnection system for high speed data transmission. In the detailed description that follows, like element numerals are used to describe like elements shown in one or more of the figures.
In a first embodiment of the present invention, a connection system includes a plug 10 (shown in
The plug 10 has a cylindrical insert 18 that is concentrically located within the collar 16 and carried within the body structure of the plug. The insert 18 includes a plurality of sockets 11 housed inside contact cavities that extend axially within the plug body. The sockets 11 are arranged in a generally circular pattern and are visible at the distal end of the insert 18 (as shown in
Referring now to
The follower 42 is shown in greater detail in
As shown in
In an embodiment of the invention, the cable 70 may include a non-conductive spline 62 that provides physical separation between the twisted-pairs of wires. The spline 62 may be made of Teflon™ or like materials. If it becomes necessary to replace one of the contacts 64, such as if the contact becomes bent or if an intermittent electrical connection is formed between the contact and associated wire, it is a relatively simple process to disassemble the connector and replace the contact. In an alternative embodiment of the invention, crosstalk within the connector may be further reduced by the use of a wire management separator 66, as illustrated in
Thus, the follower 42 prevents interference by electrically isolating the pairs of wires throughout the wire management region and also by isolating each shielded pair from the others. The individual wires are further electrically isolated from one another by the conductive grounding post 32 as each wire is crimped or soldered to a contact and placed into the contact cavity in the insert 18. The conductive grounding post 32 isolates each pair by controlling the electrical fields to prevent crosstalk between pairs. Thus, any interference from any given wire in the connection system is minimized, as the four shielded pairs are placed in a unique and optimum arrangement for minimal reflection and maximum transmission. Moreover, the symmetrical arrangement of the conductors within the sockets 11 of the insert 18, with each conductor being disposed equidistant from adjacent conductors and other field effects, provides balanced electrical characteristics of the communicated signals.
Referring now to
Referring now to
The follower 42 is arranged to be carried within the coupling nut 14 with the tip of the axial post 44 inserting into the opening of the conductive grounding post 32, so that the post engages and connects to the socket 38. This interconnection between the follower 42 and the conductive grounding post 32 extends the electrical isolation between the pairs (twisted and parallel) of cables. More particularly, the twisted pairs of cables are inserted respectively through corresponding ones of the axial passageways before passing into the pins 22 of the insert 28. Hence, the pairs become untwisted in the region of the follower 42, and the follower provides electrical isolation between the pairs to minimize cross-talk.
An alternative embodiment of the invention is shown in
More particularly, the plug 100 has a generally cylindrical outer shell comprising boot 112 and coupling nut 114, with one or more knurled bands circumscribing the outer perimeter of the coupling nut 114 to facilitate gripping. The plug 100 further includes a rotatable collar 116 at a distal end thereof. The collar 116 has internal threads 117 adapted to engage a corresponding threaded sleeve 126 of the receptacle 120 to environmentally protect the interconnected conductors (described below). The collar 116 may further include knurled regions on the exterior surface that facilitate gripping of the collar as it is threaded onto the sleeve 126. The receptacle 120 further includes a flange 124 having a plurality of mounting holes 125 that enable the receptacle 120 to be affixed to a flat surface, such as an item of electrical equipment, a utility rack, junction box, bulkhead, wall or other surface.
Each of the four socket modules of the plug 100 has a cylindrical insert 118 that is symmetrically located within the collar 116 and carried within the body structure of the plug. The insert 118 includes a plurality of sockets 110 that extend axially within the plug body. The sockets 110 are arranged in a generally circular pattern and are visible at the distal end of the insert 118 in the same manner as the preceding plug embodiment shown in
An individual socket module 150 is shown in further detail in
Likewise, an individual pin module 130 is shown in further detail in
After each module is populated with wired contacts, the follower 158 is mated with the grounding post 152. The wire will pass through the follower 158 in the same manner described above. The braided shield material of each of the four cables would be folded back over the outer surface of each follower 158 and held in place by a fastener 162, such as a conventional Bandit-type fastener. As shown in
In another embodiment of the present invention, the above described pin and socket modules may be utilized within a rectangular connector, as shown in
In yet another embodiment of the present invention, the arrangement of pins or sockets within a module can be rectangular rather than circular.
It is anticipated that the connection system of the present invention be adapted to use standard military specification contacts and insertion/removal tools. Accordingly, the present connection system would be sufficiently robust for vibration and shock, and meet the harsh environmental requirements of Mil-C-38999. The use of the conductive grounding post and the follower for the electrical isolation of shielded pairs may be used in other Military and Aerospace Specifications, such as Mil-C-81511, Mil-C-26482, Mil-C-83723, Mil-C-29600, EN, BS, ARINC, etc. These specifications generally rely on the Mil-STD 1560 for the insert performance criteria.
In addition to the advantage of meeting Military and Aerospace specifications, the present invention has significant advantages over the prior art. For example, four shielded pairs may be placed in a unique and optimized arrangement for minimal reflection and maximum transmission, allowing for little to no crosstalk. The contacts are crimpable and insert/removable for easy assembly and repairability. Also, the insert or module is environmental and fluid resistant. An exemplary Size 25 shielded pair signaling connector has the added advantage of terminating four shielded pair signaling cables in one connector. Each insert or module may have various shielded pairs placed in the same unique and optimized arrangement as the exemplary Size 11 connector module, providing the same advantages. Furthermore, each module is electrically isolated from the other, further reducing crosstalk between modules and is in optimized positions within the plated insert for minimal reflection.
Having thus described the various embodiments of a matched impedance, shielded pair, high-reliability interconnection system, it should be apparent to those skilled in the art that certain advantages have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. The invention is solely defined by the following claims.
This patent application claims priority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional Pat. App. Ser. No. 60/717,003, filed Sep. 13, 2005.
Number | Name | Date | Kind |
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6077122 | Elkhatib et al. | Jun 2000 | A |
7195518 | Bert et al. | Mar 2007 | B2 |
Number | Date | Country | |
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20070259568 A1 | Nov 2007 | US |
Number | Date | Country | |
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60717003 | Sep 2005 | US |