The present invention relates generally to communication connectors and more particularly to near-end crosstalk (NEXT) compensation in communication connectors.
In an electrical communication system, it is sometimes advantageous to transmit information signals (video, audio, data) over a pair of wires (hereinafter “wire-pair” or “differential pair”) rather than a single wire, wherein the transmitted signal comprises the voltage difference between the wires without regard to the absolute voltages present. Each wire in a wire-pair is susceptible to picking up electrical noise from sources such as lightning, automobile spark plugs and radio stations to name but a few. Because this type of noise is common to both wires within a pair, the differential signal is typically not disturbed. This is a fundamental reason for having closely spaced differential pairs.
Of greater concern, however, is the electrical noise that is picked up from nearby wires or pairs of wires that may extend in the same general direction for long distances and not cancel differentially on the victim pair. This is referred to as differential crosstalk. Particularly, in a communication system where a modular plug often used with a computer is to mate with a modular jack, the electrical wires (conductors) within the jack and/or plug also can produce near-end crosstalk (NEXT) (i.e., the crosstalk measured at an input location corresponding to a source at the same location). This crosstalk occurs from closely-positioned wires over a short distance. In all of the above situations, undesirable signals are present on the electrical conductors that can interfere with the information signal. As long as the same noise signal is added to each wire in the wire-pair, the voltage difference between the wires will remain about the same and differential cross-talk does not exist.
Crosstalk can be classified as either differential crosstalk, as described above, in which the crosstalk signal appears as a difference in voltage between two conductors of a differential pair, or common mode crosstalk, in which the crosstalk signal appears common to both conductors of a differential pair. Differential crosstalk or common mode crosstalk appearing in a communication channel can result from sources that are either differential mode or common mode in nature.
U.S. Pat. No. 5,997,358 to Adriaenssens et al. (hereinafter “the '358 patent”) describes a two-stage scheme for compensating differential to differential NEXT for a plug-jack combination (the entire contents of the '358 patent are hereby incorporated herein by reference, as are U.S. Pat. Nos. 5,915,989; 6,042,427; 6,050,843; and 6,270,381). Connectors described in the '358 patent can reduce the internal NEXT (original crosstalk) between the electrical wire pairs of a modular plug by adding a fabricated or artificial crosstalk, usually in the jack, at one or more stages, thereby canceling or reducing the overall crosstalk for the plug-jack combination. The fabricated crosstalk is referred to herein as a compensation crosstalk. This idea can often be implemented by crossing the path of one of the differential pairs within the connector relative to the path of another differential pair within the connector twice, thereby providing two stages of NEXT compensation for that pair-to-pair relationship. This scheme can be more efficient at reducing the NEXT than a scheme in which the compensation is added at a single stage, especially when the second and subsequent stages of compensation include a time delay that is selected to account for differences in phase between the offending and compensating crosstalk. This type of arrangement can include capacitive and/or inductive elements that introduce multi-stage crosstalk compensation, and is typically employed in jack lead frames and PWB structures within jacks. These configurations can allow connectors to meet “Category 6” performance standards set forth in ANSI/EIA/TIA 568, which are primary component standards for mated plugs and jacks for transmission frequencies up to 250 MHz.
Alien NEXT is the differential crosstalk that occurs between communication channels. Obviously, physical separation between jacks will help and/or typical crosstalk approaches may be employed. However, a problem case may be “pair 3” of one channel crosstalking to “pair 3” of another channel, even if the pair 3 plug and jack wires in each channel are remote from each other and the only coupling occurs between the routed cabling. To reduce this form of alien NEXT, shielded systems containing shielded twisted pairs or foiled twisted pair configurations may be used. However, the inclusion of shields can increase cost of the system. Another approach to reduce or minimize alien NEXT utilizes spatial separation of cables within a channel and/or spatial separation between the jacks in a channel. However, this is typically impractical because bundling of cables and patch cords is common practice due to “real estate” constraints and ease of wire management.
In spite of recent strides made in improving mated connector (i.e., plug-jack) performance, and in particular reducing crosstalk at elevated frequencies (e.g., 500 MHz—see U.S. patent application Ser. No. 10/845,104, entitled NEXT High Frequency Improvement by Using Frequency Dependent Effective Capacitance, filed May 4, 2004, the disclosure of which is hereby incorporated herein by reference), many connectors that rely on either these teachings or those of the '358 patent can still exhibit unacceptably high alien NEXT at very high frequencies (e.g., 500 MHz). As such, it would be desirable to provide connectors with reduced alien NEXT at very high frequencies.
The present invention provides communications connectors, in particular communications plugs, that may have improved crosstalk performance. As a first aspect, embodiments of the present invention are directed to a communications plug, comprising: a mounting substrate; a plurality of pairs of output terminals; and first, second, third and fourth pairs of conductors. The first, second and fourth pairs of the output terminals are arranged in immediately adjacent relationship, and a third pair of output terminals includes output terminals that are separated from each other such that a first output terminal of the third pair is positioned between the first and second pairs of output terminals, and such that a second output terminal of the third pair is positioned between the first and fourth pairs of output terminals. Each of the first, second, third and fourth pairs of conductors engages the mounting substrate and is attached for electrical communication with a respective one of the output terminals. The third pair of conductors has at least two locations in which the conductors of the pair cross each other, and is arranged such that, between the crossover locations, the third pair of conductors forms an expanded loop that brings segments of the third conductor into closer proximity to the second and fourth pairs of conductors than to the first pair of conductors. In this configuration, the plug (which in some embodiments is a communications plug) may exhibit a reduced tendency for differential to common mode crosstalk conversion, particularly between the third pair of conductors and the second and fourth pairs of conductors, which can improve alien NEXT performance between channels, particularly at elevated frequencies.
As a second aspect, embodiments of the present invention are directed to a communications plug, comprising: a mounting substrate; a plurality of pairs of output terminals; and first, second, third and fourth pairs of conductors. The first, second and fourth pairs of the output terminals are arranged in immediately adjacent relationship, and a third pair of output terminals includes output terminals that are separated from each other such that a first output terminal of the third pair is positioned between the first and second pairs of output terminals, and such that a second output terminal of the third pair is positioned between the first and fourth pairs of output terminals. Each of the first, second, third and fourth pairs of conductors engages the mounting substrate and is attached for electrical communication with a respective one of the output terminals. The third pair of conductors has at least two locations in which the conductors of the pair cross each other. The third pair of conductors is arranged such that, between the crossover locations, the third pair of conductors forms an expanded loop that brings segments of the third conductor into relative proximity to the first, second and fourth pairs of conductors. The positioning of the second, third and fourth pairs of conductors substantially prevents the conversion of differential mode crosstalk to common mode crosstalk between (a) the second and third pairs of conductors and (b) the third and fourth pairs of conductors. This configuration can reduce the alien NEXT experienced between a plug-jack combination, especially at elevated frequencies.
As a third aspect, the present invention is directed to a mounting substrate for a communications plug. The mounting substrate includes: a body formed of a dielectric material; a spreading member mounted to an upper surface of the body, the spreading member being configured to receive respective conductors on opposite sides thereof, and capture members mounted to opposing edge portions of the upper surface of the body. Each of the capture members is configured to receive a pair of conductors and maintain the pairs of conductors at a given distance from conductors received in the spreading member channels. This configuration can position the respective conductors such that alien NEXT performance is improved.
The present invention will be described more particularly hereinafter with reference to the accompanying drawings. The invention is not intended to be limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
This invention is directed to communications connectors, with a primary example of such being a communications plug. As used herein, the terms “forward”, “forwardly”, and “front” and derivatives thereof refer to the direction defined by a vector extending from the center of the plug toward the free end of the plug, ie., away from a cable attached to the plug. Conversely, the terms “rearward”, “rearwardly”, and derivatives thereof refer to the direction directly opposite the forward direction; the rearward direction is defined by a vector that extends from the center of the plug toward the cable. The terms “lateral,” “laterally”, and derivatives thereof refer to the direction generally parallel with the plane defined by the conductors as they align at the forward end of the plug and extending away from a plane bisecting the plug in the center. The terms “medial,” “inward,” “inboard,” and derivatives thereof refer to the direction that is the converse of the lateral direction, i.e., the direction parallel with the plane defined by the conductors and extending from the periphery of the plug toward the aforementioned bisecting plane. Where used, the terms “attached”, “connected”, “interconnected”, “contacting”, “coupled”, “mounted” and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise.
Turning now to the figures,
This imbalance typically effectively occurs from the point of contact with a connecting jack through the plug blades and the connecting wires back into the plug 10. The magnitude of the imbalance depends on the distance into the plug 10 that the wires 24a, 24b of pair 3 remain separated before returning to the twisted configuration that is characteristic of a twisted pair. The imbalance between (a) pair 3 and pair 2 and (b) pair 3 and pair 4 can convert a differential mode signal on pair 3 to common mode crosstalk on pairs 2 and 4 in the plug 10. Although this conversion from differential to common mode crosstalk can occur across the frequency band below 250 MHz, the resulting channel alien NEXT generated is typically minimal. However, it has been discovered in connection with the present invention that at elevated transmission frequencies (e.g., up to 500 MHz), the conversion of differential to common mode crosstalk can have a substantial detrimental impact on channel alien NEXT levels and, likely, the ability of the channel to meet FCC emission level limits, particularly at elevated transmission frequencies.
The imbalance typically experienced in conventional plugs 10 can be addressed by plugs of the present invention, embodiments of which are illustrated in
Referring now to
This configuration may be suitable for use in a variety of communication connectors, including plugs, patch panels, and the like. The configuration may be particularly suitable for use in a communications plug, such as that illustrated in
It can be seen in
As can be seen in
As noted above, the sled 64 of the plug 60 is fashioned such that the conductors 40a, 40b of pair 1 pass through the slot 74 that is positioned beneath the spreading member 68. This configuration may facilitate placement of the conductors in the sled 64 when the conductors 44a, 44b of pair 3 are positioned in the top quadrant of the cable 61 from which they emerge, and the conductors 40a, 40b of pair 1 are positioned in the bottom quadrant of the cable 61 (see
Another embodiment of a mounting sled according to the present invention is illustrated in
Those skilled in this art will recognize that other configurations of capture members for the laterally positioned pairs, including troughs, channels, tunnels, vanes, and the like, that maintain the laterally positioned pairs in their desired locations may also be employed with the present invention. Further, those skilled in this art will recognize that other configurations of spreading members, including channels, troughs, vanes, tunnels and the like, that maintain the expanded loop configuration of pair 3 may also be employed.
Any of the plugs and sleds illustrated and described above may be housed within a housing 100 (see
Those skilled in this art will recognize that the “expanded loop” configuration of the conductors of pair 3 may be applicable to other types of plugs. For example, an expanded loop configuration may be suitable for rigid wire lead frame type plugs (see U.S. Pat. No. 5,989,071 to Larsen et al. and U.S. Pat. No. 5,951,330 to Reichard et al, the disclosures of each of which are hereby incorporated herein in their entireties). Also, the ordinarily skilled artisan should also appreciate that this configuration is not limited to use with plugs with eight conductors; it may also, for example, be suitable for use with sixteen conductors.
As noted, plug-jack combinations employing plugs of the present invention may be especially suitable for use with elevated frequencies transmission, and may have acceptable channel alien NEXT performance at somewhat higher frequencies. For example, plug-jack combinations may result in channel alien NEXT of less than —60 dB power sum at 100 MHz, and less than —49.5 dB power sum at 500 MHz.
The invention is described further below in the following non-limiting example.
Plugs having the configuration illustrated in
The results of the testing are shown in
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.
The present application claims priority from U.S. Provisional Patent Application Ser. Nos. 60/633,783, filed Dec. 7, 2004, entitled Communication Plug with Balanced Wiring to Minimize Differential to Common Mode Crosstalk and from U.S. Provisional Patent Application Ser. No. 60/648,002, filed Jan. 28, 2005, entitled CONTROLLED MODE CONVERSION PLUG FOR REDUCED ALIEN CROSSTALK, the disclosures of which are hereby incorporated herein in their entireties.
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