EP0708501B1

Movatterモバイル変換

Info

Publication number: EP0708501B1
Application number: EP94307606A
Authority: EP
Inventors: Constance Renee Pallas; Clifford Lawrence Winings
Original assignee: AT&T Corp
Current assignee: AT&T Corp
Priority date: 1993-08-31
Filing date: 1994-10-17
Publication date: 1999-12-22
Anticipated expiration: 2014-10-17
Also published as: GB9417114D0; GB2282712B; JPH07220778A; GB2282712A; EP0708501A1

Description

Background of the Invention

This invention relates to electrical connectors.
Connectors of the type known as miniature ribbon style or telcoconnectors are typically used to provide electrical contact between cables including aplurality of unshielded twisted wire pairs. Such connectors usually comprise aninsulative housing which includes two rows of contacts. One end of the contactsprovides either a male or female mating section for electrical connection withanother connector. The opposite ends of the contacts are formed into insulationdisplacement contacts which pierce the insulation of the twisted wire pairs to provideelectrical contact thereto. The wire pairs are attached so that each wire in a pair iscoupled to a different row of the array of contacts, and so that the wires rest in anessentially horizontal direction (i.e., parallel to the contacts). (See, e.g., U.S. Pat.No. 4,350,404.)
It has also been suggested in some connector structures to have cablewire attached to insulation displacement contacts in a vertical direction (i.e.,perpendicular to the contacts). (See, e.g., U.S. Patent No. 4,066,316.)
Standards for crosstalk in connectors are becoming increasinglystringent. For example, incategory 5 of the proposed EIA/TIA TSB40 Standard, itis required that a 25 pair ribbon cable connector exhibit near-end crosstalk which isless than 40 dB at 100 MHz using the standard power sum measurement. However,the mating section of the typical connector by itself does not meet this requirement.Thus, reducing crosstalk in other portions of the connector is not sufficient toprovide a connector which conforms to this new performance standard.
GB-A-2 269 941 discloses a connector in which crosstalk is cancelled by using a printed circuit with conductive paths that run adjacent each other.

Summary of the Invention

The invention is an electrical connector comprising an insulativehousing and a plurality of conductive members mounted therein. In one section, oneend of each member is adapted for mating with another connector and in a secondsection an opposite end is adapted for providing electrical contact. The secondsection of the connector includes conductors formed in side-by-side alignment toprovide crosstalk of a polarity which is opposite to that produced by the first section.

Brief Description of the Drawing

These and other features of the invention are delineated in detail in thefollowing description. In the drawing:
FIG. 1 is a top plan view, partly cut away, of a connector in accordancewith an embodiment of the invention;
FIG. 2 is a cross-sectional view of the connector along line 2-2 ofFIG. 1;
FIG. 3 is an end view of a portion of the connector of FIG. 1;
FIG. 4 is a view of a portion of the connector along lines 4-4 of FIG. 2;
FIG. 5 is a view of a portion of the connector along lines 5-5 of FIG. 2;
FIG. 6 is a top plan view, partly cut away, of a connector in accordancewith a further embodiment of the invention;
FIG. 7 is a cross-sectional view of the connector taken along line 7-7 ofFIG. 4;
FIG. 8 is an end view of a portion of the connector of FIG. 4;
FIG. 9 is a cross-sectional view of a connector in accordance with a stillfurther embodiment of the invention; and
FIG. 10 is a cross-sectional view along line 10-10 of FIG. 9.
It will be appreciated that, for purposes of illustration, these figures arenot necessarily drawn to scale.

Detailed Description

As illustrated in FIGS. 1-3, the connector, 10, in accordance with oneembodiment, includes an insulating housing, 11, typically made of plastic. Mountedwithin the housing is an array of conductive members, e.g., 12, 13, 70 and 71. Theconductive members are typically mounted within the housing in two rows. Eachconductive member, e.g., 12, includes two opposite end portions. One end portion,e.g., 14, of each conductive member is shaped so as to form a mating section whichis adapted for receiving and electrically contacting a similar plug-type connector(e.g., FIGS. 6-8). The opposite end portions, e.g., 15, are shaped to form insulationdisplacement contacts for electrically contacting wires, e.g., 16, from a cable, 17,which typically includes a plurality of twisted wire pairs. The conductive membersare arranged so that opposite members, e.g., 12 and 13, in different rows contact thewires (16 and 18) of the twisted pairs (see FIG. 3).
It will be noted in this embodiment that the conductive members (e.g.,12 and 13) are bent inward so that the vertical distance,d, between the two rows ofconductive elements at the contact portions (e.g., 15) is less than the verticaldistance, S, at the mating portions (e.g., 14). Typically,d will be less than one-halfof S. This configuration is advantageous for reasons to be discussed.
Also mounted within the housing, 11, adjacent to the contact portions(e.g, 15) of the conductive elements (e.g., 12 and 13) is a mandrel, 20, as shown inFIGS. 1 and 2. (The mandrel has been omitted from the view of FIG. 3 for purposesof illustrating the placement of the contact portions of the conductive elements.) Themandrel, 20, is made of an insulating material such as plastic, and is typicallyrectangular in cross section, but could be a variety of shapes. The mandrel extendsessentially the full length of the connector and, desirably, includes a pair ofslots 21and 22 to accommodate the contact portions (e.g., 15) of both rows of the conductiveelements (e.g., 12 and 13). The top, bottom and left-hand surfaces of the mandrel asviewed in FIG. 2 may also include grooves, e.g., 23, for positioning wires from eachcontact portion.
The width,w, and other dimensions of the mandrel, 20, play animportant part in reducing the crosstalk of the connector. It is known that the matingsections of the conductive elements will produce a certain amount of crosstalk in theform of an induced voltage with one polarity, hereinafter referred to as "positive"crosstalk. However, the wires, e.g., 16 and 18, coupled to the contact portions arealigned side-by-side on the surface of the mandrel, 20, for a certain predeterminedlength ( w+x+y+z). This alignment will produce a crosstalk in the form of inducedvoltage of the opposite polarity to that of the mating section crosstalk ("negative"crosstalk). This change in polarity of crosstalk is due to the fact that the wire pairswill all be aligned side-by-side in a single plane over the mandrel (e.g.,pair 16, 18 isin the same plane aspair 72, 73 in FIG. 4), while the pairs of conductive memberscoupled to each wire pair (e.g.,pair 12, 13 connected to 16, 18 andpair 70, 71connected to 72, 73) will be in essentially parallel planes having a differentorientation in the mating section of the connector (e.g., as shown in FIG. 5).
For each section of the connector, the inductive crosstalk, X_ℓ (in volts),between any two pairs of conductors can be calculated according to the expression:
where I is the current in one pair of conductors and M_ac, M_ad, M_bd, M_bc are themutual inductances from one conductor to another (i.e., assuming conductorsa andbin one pair have current, I, applied thereto and conductorsc andd in the other pairhave an induced voltage).
The mutual inductance terms, M_xy (in nH), can be approximatedaccording to the expression:
where L is the conductor length in the section (in inches) andr is the distance fromconductorx to conductory divided by the conductor length (L).
For each section of the connector, the capacitive crosstalk, X_c (in volts),between any two pairs of conductors may be calculated according to the expression:Xc =dV/dt2 (Z) (Ccm)where V is the voltage on one pair of conductors, C_m is the mutual capacitancebetween conductor pairs, and Z is the impedance terminating both the near-end andthe far-end of the idle pair.
The capacitance value (C_m) is a function of the conductor shapes,spacings and lengths as well as the dielectric constants of the materials surroundingthe conductors. Formulas are available for simple geometries (see, e.g., Charles S.Walker,Capacitance,InductanceandCrosstalkAnalysis, (Artech House, 1990),pp. 66-71.
The near end crosstalk induced in an idle pair of conductors in anysection by another pair of conductors is the sum of the inductive and capacitivecrosstalk. The total near-end crosstalk in an idle pair in a section is calculated by thestandard power sum method.
Therefore, each section of the connector will exhibit a different amountof crosstalk. The value of the crosstalk in the mandrel section will be negative whencalculated according to the above. By choosing appropriate values for thedimensions (w, x, y) of the mandrel and for the wire length section (z), the crosstalkin this section can be made to nearly cancel out the positive crosstalk of theconductive members.
The appropriate dimensions may also be determined empirically bymeasuring the crosstalk for various dimensions.
Typically, the crosstalk in the conductive members was 39.5 dBbetween adjacent pairs at 100 MHz, while the crosstalk of the mandrel section was40 dB of opposite polarity.
An appropriate choice of the dimensions, w, x, y and z, will thereforetend to cancel out the crosstalk produced by the conductive members. Bending theconductive members to place the members vertically closer together at the contactportions (makingd less than S in FIG. 2) is advantageous in reducing crosstalk of theconductive members and thereby minimizing the predetermined distance required forside-by-side alignment of the wires. This is especially important where thecontributions in crosstalk by conductor pairs beyond pairs adjacent to the idle paircontribute significantly to overall crosstalk. In a typical example, the distancewwould be approximately 1.75 cm in accordance with the equations above. Ingeneral, distances in the range 1.0-2.0 cm should be useful.
A hood element, 30, snaps onto the housing, 11, to secure the mandrel,20, in the housing and to provide a compartment for the twisted wire pairs 31. Thewire pairs exit the hood where they are formed into one ormore cables 17. The hoodelement is also, typically, made of plastic.
FIGS. 6-8 show an alternative embodiment of the invention. Again, aninsulative housing, 40, includes two rows of conductive elements, e.g., 41 and 42,mounted therein. As before, each conductive element includes a mating portion, 43,at one end and an insulation displacement contact portion, 44, at the opposite end.One distinction here is that the mating portions form a plug connector which can fit,for example, into the receptacle connector of FIGS. 1-5. However, this embodimentcan also be formed into a receptacle connector by appropriately shaping the matingportions as in FIGS. 1-2.
A further distinction lies in the fact that the spacing S' between matingportions of the different rows is essentially equal to the spacing d' between thecontact portions of the two rows.
In this embodiment, the mandrel, 50, includes two parts, 51 and 52, withundulating surfaces which are complementary so that the parts fit together whileallowing a meandering path for the wires, e.g., 60 and 61, from the twisted pair cable(not shown). One wire, e.g., 60, from each pair is connected to a conductivemember, e.g., 42, in the bottom row, and the other wire, e.g., 61, from the pair isconnected to a conductive member, e.g., 41, in the top row. (See also FIG. 8 wherethe mandrel has been removed for purposes of illustration.)
As in the previous embodiment, the wires will extend for apredetermined length in a side-by-side alignment determined by experiment orcalculated from the equations above in order to compensate for the crosstalkgenerated by the mating portion of the conductive members. In this embodiment,the predetermined length is established by the path length of the undulating surfacesof the twoparts 51 and 52. In a particular example, the path length is approximately3.3 cm, but in general would range from 2.5-4.0 cm. The contact portions, e.g., 44,of the conductive members, e.g., 41 and 42, have approximately the same verticalspacing as the mating portions, e.g., 43 (i.e., S'=d') to allow for the bending of thewires (60, 61) between contacts. This spacing is made possible by the increased pathlength of the wires over the mandrel surface.
As before, a hood (not shown) snaps onto the housing in order to holdthe mandrel and the twisted wire pairs.
While the invention has been described for cables including twisted wirepairs, it is also advantageous for any cable including balanced wire pairs. Also,while the wires are preferably perpendicular to the conductive members to produce ashort connection, the invention may also be used where the wires are oriented atother angles, including the case where the wires are parallel to the conductivemembers at the point of contact.
While the invention is optimized by keeping the wires in side-by-sidealignment over the mandrel surface, some misalignment or staggering of the wirescould still result in sufficient negative crosstalk to be advantageous. In general,however, no wire should have a vertical distance (as viewed in FIG. 4) from anyother wire which is greater than half the distance from the centerline of one pair tothe centerline of the adjacent pair.
Further, the wires need not be equally spaced from each other as shownin FIG. 4. Rather, varying the distance between wires can produce a greater negativecrosstalk. In general, it is advantageous to have a distance between wires in a pair(e.g., 16, 18) at least equal to one-half the distance from the centerline of one pair(16, 18) to the centerline of an adjacent pair (72, 73).
It will also be appreciated that the stub length of each wire (dimension Zof FIG. 2) can also be used to control the amount of negative crosstalk.
Finally, it should be understood that the invention in its broadest form isdirected to providing a section of a connector which has a crosstalk of a polarityopposite to that of the mating portion of the connector. The use of a mandrel in that"compensation" section to keep the wires in side-by-side alignment is an advantageous embodiment of that principle. However, a similar effect could beproduced as illustrated by the connector shown in FIGS. 9 and 10, where elementssimilar to FIGS. 1-5 are similarly numbered. Hence, while a mandrel, 20, is stillused to connect the wires, e.g., 16, to their appropriate conductive members, e.g., 12,the conductive members themselves, e.g., 12, 13, 70 and 71, are bent so that they arein side-by-side alignment for some predetermined distance (w). In this example, theconductive members (e.g., 12 and 13) coupled to each wire pair are insert moldedinto separate plastic members, 24 and 25, which plastic members are held together intheconnector housing 11. As illustrated in FIG. 10, the conductive members neednot be in perfect side-by-side alignment to produce a sufficient negative crosstalk asdiscussed regarding the previous embodiments. Alternatively, all the conductivemembers could be molded into a single plastic member. It will also be appreciatedthat all the conductive members (12, 13, 70 and 71) could be deposited on a surfaceof a printed circuit board in place of theplastic members 24 and 25. In fact, themandrel, 20, and wires, e.g., 16, could be eliminated entirely so that the inventionprovides a means of mounting a connector to a printed circuit board while theconductive members on the board have a specified length and spacing to essentiallycancel the crosstalk produced by the mating sections as previously discussed.
Nevertheless, it will be understood that the term "conductors" in theclaims is intended to include conductive members (such as 12, 13), wires (such as16, 18), and conductive members deposited on printed circuit boards within theirscope.
Various additional modifications will become apparent to those skilledin the art. All such variations which basically rely on the teachings through whichthe invention has advanced the art are properly considered within the scope of theinvention.

Claims

An electrical connector (10) comprising:
an insulative housing (11); and
a plurality of conductive members (12, 13, 70, 71) mounted within thehousing, one end (14) of each member in a first section being adapted for matingwith another connector and an opposite end (15) of each member in a second sectionbeing adapted for providing electrical contacts, the conductor members being arranged in at least two rows,
CHARACTERIZED IN THAT
the second section includes conductors (16, 18, 72, 73) positionedessentially in side-by-side alignment to provide crosstalk of a polarity which isopposite to that produced by the first section, the conductors being connected to respective conductive members.
The connector according to claim 1 wherein the conductors in thesecond section are integral extensions of the conductive members in the first section.
The connector according to claim 2 wherein the conductive membersare formed on a printed circuit board.
The connector according to claim 1 wherein the conductors are wires,and further comprising a mandrel (20) in close proximity to one end of each memberand having a surface of predetermined length on which each wire is laid so that eachwire is in side-by-side alignment for the predetermined length.
The connector according to claim 4 wherein the distance (d) betweenthe contact ends of the members of the two rows is less than the distance (s) betweenthe mating ends of the members of the two rows.
The connector according to claim 4 wherein the distance (d) betweenthe contact ends of the members of the two rows is essentially equal to the distance(s) between the mating ends of the members of the two rows.
The connector according to claim 4 wherein the mandrel comprisestwo parts (51 and 52), and the surface of predetermined length comprises an undulating surface of one of the parts which is adjacent to a complementaryundulating surface of the other part.
The connector according to claim 4 further comprising a hood element(30) mounted to the housing and enclosing the mandrel.
The connector according to claim 4 wherein the mandrel surfaceincludes a plurality of grooves (23) for aligning the wires with associated conductivemembers and maintaining spacing between the wires.
The connector according to claim 4 wherein the wires comprise aplurality of twisted wire pairs (31), and the spacing between wires in a pair is at leastequal to one-half the distance between centerlines of adjacent pairs.