Wave transmission lines and networks – Plural channel systems – With balanced circuits
Reexamination Certificate
1999-04-02
2002-03-12
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
With balanced circuits
C333S02400C, C333S260000
Reexamination Certificate
active
06356162
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention is in the field of cable and connector components for high speed data communication. More particularly, the invention is in the field of cable and connector components in which stray reactances and cross talk are compensated for.
2. Related Art
High speed electronic communication systems wend their way throughout the landscape of our workplaces, having become a ubiquitous feature of a technological society. Telephone, computer and process control networks, local area networks (LANs), wide area networks (WANs) and the Internet, and others form the backbone of modem communication. These networks and communication systems are generally referred to hereinafter as “interconnect systems.” As society seeks to send more and more data through the wires constituting these interconnect systems, data rates, the quantity of information a given wire carries in a given period of time, have been pushed higher and higher. Since the quantity of information carried as an electronic signal increases as the frequency of the electronic signal increases, all else being equal, cables for use in modern, high speed interconnect systems are designed to carry very high frequency signals, e.g. 500 MHZ, without significant cross-talk or insertion loss over useful distances, e.g. hundreds or thousands of feet.
Modern offices and factories are flexible frameworks. Spaces mutate and evolve into different uses over time, necessitating rewiring portions of the various interconnect systems used. Some cable may remain permanently installed in the walls of a building, while other cables are moved from one portion of an interconnect system to another when the system is reconfigured. Consider, for example, the cable which connects your telephone instrument to the wall jack. When you move the telephone from one room to another, you generally bring that cable with the phone. To make such flexibility possible, the cable and telephone network employ a connector system including the wall jack and a plug on the cable. For purposes of the remaining discussion, a “connector system” includes a plurality of “connectors” by which one cable or component of a system can be releasably connected for electrical communication with another. Connectors include jacks or receptacles and plugs. A connection is formed by the conductive elements of a connector system when the connectors are mated, for example when a plug is inserted into a jack.
Electrical signal connectors include, generally, a body and one or more conductive, signal carrying elements. The body may include an insulating portion which supports and protects the signal carrying elements apart from each other. The entire connector may be surrounded, optionally, by a conductive shield. The signal carrying elements include, generally, two or three portions: a contact portion, a terminal portion and optionally a connecting portion therebetween. When a connecting portion is not used, the terminal portion and the contact portion are directly connected or integral with each other.
There are a number of popular modular, multi-position connectors, including those commonly referred to as RJ-style connectors, used in both telecommunications applications and high speed data communications applications. Among the more popular configurations are 4-conductor, 6-conductor and 8-conductor types, commonly (and sometimes erroneously) referred to as RJ-22, RJ-11 and RJ-45 types, respectively. For ease of description, without loss of generality, all such multi-position connectors are referred to herein below as an 8-conductor high speed communications connector. However, more or fewer conductors, and other configurations can be used, as will be evident to those skilled in the art.
In the case of an 8-conductor high speed communications type connector, the body is generally a solid, one or two-piece plastic unit, surrounding and supporting the signal carrying elements. When constructed using lead frame technology, the signal carrying elements are stamped out of one or more sheets of thin metal. The contact portion has a blade shape in the case of an 8-conductor high speed communications plug and has a wire spring shape in the case of an 8-conductor high speed communications jack. The terminal portion may be shaped for any one of several suitable termination methods. For example, the terminal portion may be shaped as a spike, tube, wire, etc., for termination by insulation displacement (i.e., piercing), soldering or crimping, printed wiring board (PWB) attachment, etc., respectively. Conventionally, the connecting portion, if used, is simply a wire or similar conductor connecting the contact portion to the terminal portion.
Cables for transmitting high speed digital signals frequently make use of balanced differential twisted pair transmission line technology, as explained above, because balanced differential pair transmission lines avoid some types of crosstalk and other interference, i.e., noise. Balanced differential twisted pairs are referred to hereinafter as twisted pairs. Information is transmitted over a twisted pair as electrical signals. In a twisted pair, each wire of the pair carries an information signal which is equal in amplitude and 180° out of phase with the other. That is, the signals are equal and opposite, referred to hereinafter as differential signals. Ideally, the proximity of the wires of a twisted pair to each other causes crosstalk and noise to affect both wires of the pair equally. Thus, crosstalk and noise ideally appear in both wires of the twisted pair in equal amplitudes and 0° out of phase with each other, referred to hereinafter as a common mode signal. Receivers for use with such cables detect differential signals, while substantially rejecting common mode signals. However, there are sources of differential noise, even in a well-balanced twisted pair transmission line.
Connector elements include asymmetrical parasitic reactances which are a principle source of differential noise due to coupling. The following discussion focuses on the parasitic reactances included in RJ-style connectors, such as the 8-conductor high speed communications, 8-position connector commonly used in North America for data communication networks, although the principles of the present invention are not limited in applicability to either the 8-conductor high speed communications connector specifically or the RJ-style connectors generally. In RJ-style connectors, as shown in
FIG. 1
, the plug
101
includes a plurality of flat, blade-shaped terminals
103
which mate with a corresponding plurality of bent spring terminals
107
included in the jack
109
. The blade-shaped terminals exhibit significant capacitive coupling, while the spring terminals exhibit significant inductive coupling.
In the body of a multi-pair cable, each wire of each pair is affected substantially equally by adjacent wires because the pair is twisted. However, when a multi-pair cable is terminated at an RJ-style plug or jack, the twisted pairs are untwisted and flattened out into a linear arrangement. Thus, some wires are adjacent wires of unrelated pairs, over a significant length. This gives rise to coupling between adjacent wires from different pairs, with an interfering signal introduced into one wire of a pair, but not into the other—differential noise.
SUMMARY OF THE INVENTION
The present invention provides an improved interconnect system including a cable and connectors.
In an interconnect system according to aspects of the present invention, including a communications cable of balanced pairs of conductors, a plug and a jack, wherein one or more of the cable, the plug and the jack include a stray, reactance, the system further includes a compensating reactance built into another one or more of the cable, the plug and the jack. The compensating reactance may further comprise a &pgr;-network connected in one conductor of a first pair of conductors. In at least some embodiments, the compensating reactance corrects for both near end cross-talk and far end
Cyr Gary
DeFlandre Yves
Hoffman Marc
Glenn Kimberly E
Nordx/CDT, Inc.
Pascal Robert
Wolf Greenfield & Sacks P.C.
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