Abstract:
A modular telephone-style plug features a substantially three sided intermediate section which integrally connects the cable receiving end with the contact mating end of the plug. The intermediate section has an opening which spans virtually all of the fourth side of this section. The resultant three sided intermediate section provides for a reduced dielectric constant in the interior space in which the critical conductor transition from jacketed cable to contact termination occurs. This produces lower crosstalk and higher data propagation to allow this modular plug to be capable of a higher frequency for data transmission. The intermediate section features an expanded interior to lower crosstalk between twisted pairs of conductors over a wide range of data transmission rates. The intermediate section&#39;s expanded interior space permits greater freedom in the placement and relative positioning of any conductor pair to any other conductor pair. This interior space allows conductor pairs to be located a greater distance apart which reduces crosstalk substantially at higher frequencies. By utilizing the larger interior space, conductor pairs may also be placed angularly to each other so that conductor pairs are not co-planar, which further reduces crosstalk.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical connectors and, more particularly, is directed toward a telephone-style modular plug that can operate at higher frequencies with lower crosstalk. 
     2. Description of Related Art 
     Data communication systems being developed are constantly requiring higher and higher transmission rates. As the rates have increased to the 100 Megahertz (MHz) range, the problem of near end crosstalk (NEXT) has become particularly vexing. Crosstalk refers to the signals induced in an adjacent conductor due to magnetic (inductive) and electric field (capacitive) coupling between the conductors. The crosstalk of interest to this invention occurs in telephone-style modular plugs (near end crosstalk or “NEXT”). The crosstalk in cables and modular jacks are related fields but are not specifically addressed by this invention. 
     Advances in cable design and improved control of manufacturing processes have improved the electrical performance of network data cables from −32 dB NEXT to better than −42 dB NEXT at a transmission frequency of 100 MHz. This is a dramatic improvement in isolating the coupling of a signal being transmitted through cables, especially those carrying eight conductors twisted together in pairs as used in the telecommunications industry. As a result of these advances in cable electrical performance, the performance of prior art modular plugs has fallen farther behind, so that the amount of crosstalk within a modular plug has become the most significant limiting factor in a system of networking cables, female modular jacks or Alto outlets, and male modular plugs. A large part of the problem arises when the conductors leave the protective confines of the cable jacket, even though crosstalk is minimized by the conductors remaining twisted together in pairs. In order to terminate the conductors in a telephone-style modular plug, however, they must be untwisted and mounted in the plug&#39;s dielectric housing in a substantially parallel arrangement, a condition wherein the conductors are most susceptible to NEXT. 
     NEXT is the electrical field generated by a signal which is transmitted into a first connection, and this electrical field has lines of force which pass around and into a second connection, causing an electrical signal to flow in the second connection. This induced electrical signal flow alters and acts upon any original transmitted signal sent through the second connection, with the outcome that any receiver of the second connection signal sees an altered, distorted signal. This is the source of signals that cannot be correctly understood and therefore requires that the original second transmitted signal be transmitted again, using up valuable data bandwidth and degrading the performance of a connection system. As crosstalk becomes increasingly larger, it can have the same signal strength as the original transmitted signal, rendering the entire connection useless because it is impossible to separate the induced signal (crosstalk) from the original signal. This is commonly referred to as S/N, or signal to noise ratio. If the noise (crosstalk) is as strong as the signal, then it is impossible to separate the original signal from the induced signal (noise). The reduction of crosstalk is extremely important to enable connection systems to transmit signals as error free as possible, and to increase the data frequency that a connection system can deliver with more signal than noise. 
     A number of years ago, a standards committee comprised of representatives of various companies and organizations in the electronics, computer, and telecommunications industries began the development of a voluntary standard called EIA/TIA 568. The objective of this standard was to provide for interchangeability between various manufacturers&#39; components and to set forth a minimum set of electrical requirements needed to deliver a usable signal at frequencies up to 100 MHz independently of which manufacturer&#39;s products might be used in a networking connection system. This standard was completed only in the last few years and sets out mechanical and dimensional requirements for modular female jacks/outlets, and for modular male plugs to assure mating compatibility. This so-called 568 standard also defines a set of minimum electrical requirements for cables, for modular male plugs, and for modular female jacks/outlets at various frequencies from 0.772 MHz to 100 MHz for products classified into categories. For example, the electrical requirements for category 3 components is less stringent than the electrical requirements for category 5 Ad components. This standard also specifies the conductor wiring arrangements within the male plugs, distance limitations for cable and for cable assemblies terminated with modular plugs. 
     Referring now to the electrical requirements of EIA/TIA 568, it sets out the minimum NEXT for any one conductor pair to any other conductor pair within the cable, as well as within the male plug as terminated onto a section of cable. Inasmuch as modular plugs are relatively small in size, it is inevitable that the close proximity of the contacts and terminated ends of the conductors induce crosstalk between different signal pairs. The most crosstalk allowed for a category 5 modular plug between worst case pairs is −40 dB at 100 MHz. As category 5 cables generally have four conductor pairs, the worst case is those two conductor pairs that have the most crosstalk to each other and more crosstalk than any other two conductor pairs. Because of the wiring arrangement specified by EIA/TIA 568, the worst case pairs are always from pair  1 , corresponding to contact positions in the plug of  4  and  5 , measured to pair  2 , corresponding to contact positions in the plug of  3  and  6  (see the wiring arrangements of FIGS.  1  and  2 ). This interleaved wiring arrangement creates a high level of crosstalk within the conductor wiring exposed in the plug. 
     Various approaches have been used to try and overcome these NEXT deficiencies in the design of the plug. As stated before, NEXT is a function of inductive and capacitive interactions between conductors. The general thrust of the industry is to address only the capacitive problems. Rohrbaugh et al., in U.S. Pat. No. 5,628,647, seek to reduce both the magnetic and capacitive coupling by utilizing the feature of staggering or offsetting conductor receiving channels, but the remainder of the most pertinent related art concentrate solely on the capacitive effects. For example, Kristiansen in his U.S. Pat. No. 5,284,447 forms an elongated aperture in the body of the contact terminals, thus reducing the capacitance between adjacent contact terminals by reducing the amount of their confronting surface areas. U.S. Pat. No. 5,593,314 to Lincoln teaches a structure which staggers the longitudinal location of the confronting bodies of the contact terminals to reduce their capacitance. U.S. Pat. No. 5,727,962, to Caveney et al. teaches the offset terminal end arrangement disclosed in Rohrbaugh et al., supra, and forces the cable into the modular plug as far as possible, so that the length of untwisted conductors will be as short as possible. 
     All of these prior art patents, specifically incorporated herein by reference, are successful in what they do, but they limit their concerns solely to the electrically conducting components, namely, to the arrangement of the conductors and the structure of the terminal contacts. The instant invention, in contrast, extends this inventive field to include the body of the modular plug. 
     Undesirable near end crosstalk between conductors is primarily a function of capacitance: the more the capacitance, the more the crosstalk. Thus, in order to reduce the NEXT, the capacitance between the conductors must be reduced. Capacitance is dependent on two factors: (1) it is inversely proportional to the center-to-center distance between the conductors; and (2) it is directly proportional to the dielectric constant of all of the matter surrounding the conductors. Consequently, increasing the distance between the primary conductors lowers the capacitance, and lowering the average dielectric constant in the vicinity of the conductors also lowers the capacitance. 
     The primary area of interest of the present invention is the reduction of the effective dielectric constant of the material surrounding the conductors, i.e., the average dielectric constant of all of the materials which are present. 
     While the recent prior art makes some improvement toward addressing the problem of NEXT within the plug as assembled onto the cable, it remains deficient in significantly improving NEXT in the critical transition area of the plug where the conductors leave the controlled structure of the jacketed cable and are exposed to each other in a confined environment prior to their point of termination by the contact blades. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide a modular plug with a reduced dielectric constant in the transition area of the conductors extending from the jacketed cable to the point of termination in the plug to overcome the crosstalk deficiencies of the prior art. 
     Another object of the present invention is to provide a larger interior volume within the modular plug for the transition of the conductors from the jacketed cable to the point of termination as a means of reducing crosstalk between the conductor pairs. 
     Yet another object of the present invention is to provide a means for bringing non-planar conductor pairs to their respective conductor channels with a minimum of planar alignment as yet a further means of reducing crosstalk between the conductor pairs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, aspects, uses, and advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of the present invention when viewed in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a top view which illustrates a telephone-style modular plug in a first preferred embodiment of the present invention; 
     FIG. 2 is another top view of the modular plug of FIG. 1; 
     FIG. 3 is a side view of the modular plug of FIG. 1; 
     FIG. 4 is a longitudinal sectional view of the modular plug of FIG. 1 taken along line A—A of FIG. 5; 
     FIG. 5 is a top view of the modular plug of FIG. 1; 
     FIG. 6 is a front view of the modular plug of FIG. 1; 
     FIG. 7 is a cross-sectional view of the modular plug of FIG. 1 taken along line B—B of FIG. 3; 
     FIG. 8 is a rear view of the modular plug of FIG. 1; 
     FIG. 9 is a cross-sectional view of the modular plug of FIG. 1 taken along line C—C of FIG. 5; 
     FIG. 10 is a sectional view of the modular plug of FIG. 1 taken along line D—D of FIG. 8; 
     FIG. 11 is a longitudinal sectional view of a modified embodiment of the modular plug of FIG. 1; 
     FIG. 12 is a longitudinal sectional view which illustrates a second preferred embodiment of a telephone-style modular plug of the present invention; and 
     FIG. 13 is a longitudinal sectional view which illustrates a third preferred embodiment of a telephone-style modular plug of the present. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-4, a telephone-style modular plug  10  comprises a housing  12  having a top  14 , a pair of side walls  16  and  18 , a bottom  20 , a front  22 , and a rear  24 . Housing  12  can be visualized, for descriptive purposes, as being composed of three integral sections, a cable receiving section  26 , an intermediate section  28 , and a contact terminating section  30 . 
     Cable receiving section  26  includes a cable receiving cavity  32  (FIG. 4) which receives the terminal end  34  of a cable  36 . 
     Cable  36  typically comprises a jacket  38  enclosing, for example, four twisted pairs of insulated conductors  40  (FIGS.  1 - 2 ), each conductor comprising either a multiplicity of twisted strands or a solid wire. Cables can also be provided with a different number of conductors; for example, a two line telephone cable contains four conductors terminated in contact positions  3  through  6  of a standard modular plug. A cable housing ten conductors is also available, a construction which may be accommodated by modifications to the preferred embodiments, to be disclosed in greater detail below. 
     Cable receiving cavity  32  (numbered in FIG.  4  and shown in outline in FIG. 3) extends from a cable receiving aperture  42  in rear  24  through cable receiving section  26  and through intermediate section  28  to a pair of opposed, flanking, vertical guide walls  44  which slope inwardly from sidewalls  16  and  18 ; see FIGS. 4,  5 ,  8 , and  10 . Within cable receiving section  26 , the height of cable receiving cavity  32  steps down at shoulders  46  and  48  (FIG. 4) from its maximum height at cable receiving aperture  42  to its minimum height throughout intermediate section  28 . The width of cable receiving cavity  32  is essentially the width of housing  12  and is bounded by side walls  16  and  18  (FIG.  10 ). A strain relief tab  50  pivots on a living hinge  52  within a transversely elongated aperture  54  in top  14  to pinch cable  36  to provide strain relief therefor, as is conventional in the art; see FIG. 13 of Caveney et al., supra, for example. Strain relief tab  50  includes a shoulder  56  which latches with corner  58  bordering aperture  54 , when tab  50  is depressed downwardly into operative position. Rounded corners  60  (FIGS. 4-5 and  10 ) facilitate the insertion of cable  36  into cable receiving aperture  42 . 
     Prior to exiting the terminal end  34  of cable  36 , conductors  40  are protected by jacket  38  from outside electromagnetic influences. Near end crosstalk (NEXT) effects inside cable  36  are minimized by the conductors  40  being twisted together in pairs. But once conductors  40  leave terminal end  34  of cable  36  in intermediate section  28  (e.g., FIGS.  1 - 2 ), they must be untwisted to properly enter contact terminating section  30 , as will be described in greater detail hereinafter. Within intermediate section  28 , therefore, conductors  40  are particularly susceptible to NEXT. 
     The present invention acts to reduce NEXT in intermediate section  28  in various ways, which will now be discussed in turn. 
     First, and in accordance with the present invention, an opening  62  is formed in top  14  throughout intermediate section  28 . Opening  62  has significant electrical effects on the signals traveling through the conductors  40  in intermediate section  28 , because of its influence on the composite dielectric constant surrounding conductors  40 . Modular plugs are typically made of polycarbonate. Polycarbonate is the preferred material, because of its unique combination of strength, resiliency, chemical inertness, and transparency. Polycarbonate, however, has one serious shortcoming in its properties, that of the dielectric constant. For high speed data transmission, the dielectric constant plays a critical role in the propagation rate of signals. The lower the dielectric constant, the better the electrical properties. Air has a good dielectric constant, while polycarbonate has a relatively poor dielectric constant. Since the present invention provides an opening  62  in intermediate section  28 , the volume of the material of which modular plug  10  is made, namely, polycarbonate, is reduced, thus lowering the dielectric constant in the critical conductor transition area  28  between terminal end  34  of cable  36  and contact terminating section  30 . This is significant because conductors  40  in this transition area are exposed outside of jacket  38  and therefore are more affected by the electrical properties of the material around those conductors. Because of opening  62 , the average dielectric constant of the combination of the surrounding air and polycarbonate is noticeably lower than prior modular plug dielectric constants. Transmission rates are correspondingly improved, therefore. 
     Second, and in accordance with the present invention, opening  62  expands the volume of cable receiving cavity  32  in intermediate section  28 . As a consequence, individual conductors  40  have more room to separate from each other, and each twisted pair has more room to separate from other twisted pairs. Since capacitance is inversely proportional to separation distance, separating conductors  40  reduces capacitance and thereby reduces NEXT. 
     Third, and in accordance with the present invention, each pair of conductors is left twisted for as long as possible before entering contact terminating section  30 . Thus, the interactions between conductors is further minimized. See, for example, the conductors in FIGS. 1 and 2, to be discussed in greater detail below. In addition, a fourth way to reduce NEXT in intermediate section  28  will be discussed below. 
     In addition to opening  62  and previously mentioned sloping guide walls  44 , intermediate section  28  also includes other important features. As most clearly seen in FIGS. 8-9, but also visible in FIGS. 1-5, a pair of opposed longitudinal projections or lips  64  extend horizontally inwardly from the top  66  of sidewalls  16  and  18 . The under-surface  68  of projections  64  is shown as coplanar with the interior ceiling surface  70 , i.e., the interior top surface of the portion of cable receiving cavity  32  in intermediate section  28  (FIGS. 4,  8 , and  9 ). As a modification to the foregoing, under-surface  68  may protrudes further interiorly of cable receiving cavity  32 . The intersections of under-surfaces  68  with sidewalls  16  and  18  produce interior corners  72  (FIG. 9) which can extend a distance less than the length of the intermediate portion, or alternately, may extend a distance equal to the length of the intermediate portion. These interior corners  72  provide a means of limiting any pair of conductors  40  which is routed near a sidewall from lifting above top  14  of modular plug  10  during the assembly process of inserting a cable and conductors into the plug. The lift-limiting corners  72  will help prevent a conductor pair from rising above the exterior of the plug, where it might be subject to damage due to not being protected by the body  12  of plug  10 . Projection  64  may be from one sidewall only, or may consist of multiple projections from the same sidewall (not shown). Projections  64  preferably extend inwardly from both sidewalls  16  and  18 , provided that they do not close opening  62 . Under-surfaces  68  are located substantially away from the conductor pairs and do not serve as guide surfaces or alignment guides for the insertion of the conductors into contact terminating section  30 . 
     In a second preferred embodiment shown in FIG. 12, projections  64  are eliminated (cf. FIGS.  4  and  12 ), which expands opening  62  even further compared to the first embodiment of FIGS. 1-11. Both embodiments are within the present invention, since each has its own distinct advantages. The projections of the first embodiment protect the conductor pairs, as explained above. The expanded opening  62  of the second embodiment further reduces the composite dielectric constant which concomitantly reduces NEXT. Nonetheless, in either case, the dielectric effect produced by opening  62  contributes to a lower composite dielectric constant than prior art plugs for the intermediate portion  28  of plug  10 , which produces significantly improved signal performance and lower crosstalk in the transition area of the conductors. 
     Another feature in intermediate section  28  is exterior notches  74  and  76  (FIGS. 3,  5 , and  10 ) in sidewalls  16  and  18 , respectively, which assist a handler in gripping modular plug  10 . 
     Contact terminating section  30  is the free end which mates with a female, telephone-style modular jack (not shown). Conductors  40  are therefore arranged such that they will make electrical contact with the spring contacts of a standard modular jack in conformance with the architecture required by FCC regulations. Referring to the cross-sectional view in FIG. 4, contact terminating section  30  joins intermediate section  28  at wall  78 . Opening into wall  78  is an elongated, conductor-positioning slot  80  bordered by an upper surface  82  and a lower surface  84 . Upper slot surface  82  includes a horizontal portion  86  and an upwardly angled portion  88 , whereas lower slot surface  84  is strictly horizontal. Also see FIGS.  3  and  7 - 9 . 
     Angled portion  88  is steeper than corresponding angled surfaces of prior art plugs. The steeper slope of angled portion  88  allows conductors  40  to be untwisted for a shorter distance prior to insertion into slot  80 , so that the twisted arrangement of each conductor pair is preserved for the maximum distance. This preservation of conductors  40  as twisted pairs to within a close proximity of the contact terminating section  30  provides more control of the electrical field surrounding each conductor up to the point of separation from the conductor pair. The benefit of this steeply angled surface is a further reduced crosstalk between the conductor pairs and the conductors belonging thereto. 
     A plurality of channels  90  are defined within slot  80  by opposed ridges  92  and  94 . FIG. 4 shows a sectional side view of one of the channels  90 , while FIGS. 8 and 9 show an end and cross-sectional view of wall  78  and slot  80  as seen through cable receiving cavity  32  from the direction of the rear  24 . FIG. 10 shows a sectional view taken along lines D—D of FIG. 8 looking down on lower slot surface  84 . Each channel  90  receives one conductor  40  and constrains it against movement toward or away from the other conductors  40 . 
     As most clearly seen in FIGS. 4 and 10, channels  90  are closed at their front ends  96 . Prior to cable  36  being inserted into modular plug  10 , the terminal end  34  thereof is stripped of jacket  38  to expose the twisted pairs of conductors  40 . Cable  36  is inserted into modular plug  10 , the terminal end of each pair of conductors  40  is untwisted enough to fit within channel  90  with the tip of the conductor abutting end  96 , and the terminal ends of the individual conductors are fully inserted into channels  90 . This position is shown in FIG.  1 . Cable  36  is then forced further into plug  10  to the position shown in FIG.  2 . This last step gently crimps the twisted pairs which are exposed within intermediate section  28 , making them bulge in different directions. The exposed twisted pairs are then non-parallel, i.e., they extend at different angles relative to the other pairs, and they are separated by larger distances than they were prior to their crimping. These conditions reduce NEXT in intermediate section  28 . Being at different angles reduces the magnetic interactions, and being further apart reduces the capacitive effects. Since the bulging is largely uncontrollable, dependent on the relative resistances felt by the conductors, some arrangements of twisted pairs may not be as effective in reducing NEXT as others might be. Opening  62  in intermediate section  28  permits visual inspection of the twisted pairs and manual repositioning of them, if desired. This is the fourth way of reducing NEXT in intermediate section  28 , mentioned initially hereinabove. 
     Referring now to FIGS. 6 and 7, a front view and a cross-sectional front view along the lines B—B of FIG. 3 are shown. A plurality of parallel, longitudinally extending partitions  98  are uniformly spaced across the width of modular plug  10 . Terminal contact receiving slots  100  are formed between adjacent partitions  98  (only a few partitions and slots are referenced with numerals in the drawings to avoid overcrowding). 
     FIG. 4 shows a sectional view of a slot  100  taken along line A—A of FIG.  5 . Each slot  100  extends from front  22  of plug  10  to a raised transverse partition  102  (FIGS.  4 - 5 ), is open through top  14 , and has a bottom ledge  104  opposite top  14 . Bottom ledge  104  includes a narrow rectangular opening  106  which communicates with both slot  100  and the underlying channel  90 . A terminal contact  108  (FIGS. 1-2 and  11 - 13 ) is forced into each slot  100  until shoulders  110  of contact  100  rest on ledge  104 . Tangs  112  of contact  108  pass through opening  106  into channel  90 , where they pierce the insulation surrounding the conductor  40  residing in channel  90  (not shown). Terminal contact  108  includes a rounded cap  113  designed to make electrical contact with the spring contacts of the mating modular jack, and, as disclosed and claimed by Kristiansen, supra, terminal contact  108  further includes an elongated aperture  114  through contact  108  which reduces the capacitance between adjacent contacts. 
     Centered on front  22  and protruding therefrom is a conventional guide nose  116  for keying the fit with the mating modular jack. A conventional locking tab  118  is pivotally mounted to bottom  20  at  120  and extends obliquely rearwardly therefrom. Locking tab  118  includes spaced shoulders  122  for locking with complementary latching members (not shown) on the mating modular jack. 
     Referring now to FIGS.  7  and  11 - 13 , there are times when modular plug  10  is required to carry additional lines of information. In a modification of the first preferred embodiment, plug  10  is adapted to carry ten conductors, be they in the form of a ten conductor cable or the addition of two single conductors. Flanking the eight channels  90  (FIG. 7) are two additional slots  124  and  126  which add plug positions  0  and  9  to the regularly provided eight positions  1 - 8 . Slots  124  and  126  communicate via additional rectangular openings  106  (not shown) with two additional conductor holding channels  128  recessed in sidewalls  16  and  18  (only one being shown in FIGS.  11 - 13 ). The FIG. 11 embodiment is identical to the first preferred embodiment shown in FIGS. 1-10 except for the addition of channels  128 , which expand the utility of modular plug  10 . 
     FIG. 12 adds to the first preferred embodiment both the additional channels  128  and the elimination of projections  64 , as aforedescribed. 
     FIG. 13 is also identical to the first preferred embodiment except that to this embodiment has been added a protective grating bar  130  hinged at  132  to top  14 . As few as one grating bar  130  can be employed, or as many as needed, to prevent conductors  40  from extending above top  14 . Plural grating bars  130  can be provided with a common pivot  132  for all grating bars or with each having its own pivoting area such that each grating bar can be pivoted independently of the others. The length of each grating bar  130  is approximately that of the length of opening  62  such that the free end  134  will engage wall  78  after being pivoted to a horizontal orientation from its original vertical orientation. Hinge  132  consists of a thin wall of material such that grating bar  130  may be rotated ninety degrees from its original orientation and hinge  132  will flex and stretch to a new shape without losing strength or fracturing in the pivoting area. Grating bars  130  can include one or more extension tips  136  which are of a size that they will engage corresponding slots  138  in wall  78 . 
     It can be seen from the above that an invention has been disclosed which fulfills all the objects of the invention. It is to be understood, however, that the disclosure is by way of illustration only and that the scope of the invention is to be limited solely by the following claims.