Capacitive crosstalk compensation arrangement for communication connectors

[0002] 1. Field of the Invention

[0003] This invention relates to arrangements for providing capacitive crosstalk compensation coupling among signal paths in high frequency communication connectors.

[0004] 2. Discussion of the Known Art

[0005] There is a need for a durable, high frequency communication connector that compensates for (i.e., cancels or reduces) crosstalk among and between different signal paths through the connector. As broadly defined herein, crosstalk occurs when signals conducted over a first signal path, e.g., a pair of terminal contact wires associated with a communication connector, are partly transferred by inductive and/or capacitive coupling into a second signal path, e.g., another pair of terminal contact wires in the same connector. The transferred signals define “crosstalk” in the second signal path, and such crosstalk degrades any signals that are being routed through the second path.

[0006] For example, an industry type RJ-45 communication connector has four pairs of terminal wires defining four different signal paths within the connector. In typical RJ-45 plug and jack connectors, all four pairs of terminal wires extend closely parallel to one another over the lengths of the associated connector bodies. Thus, signal crosstalk may be induced between and among different pairs of terminal wires within the typical RJ-45 plug and jack connectors, particularly when the connectors are mated to one another. The amplitude of the crosstalk becomes stronger as the coupled signal frequencies or data rates increase.

[0007] Applicable industry standards for rating the degree to which communication connectors exhibit crosstalk, do so in terms of so-called near end crosstalk or “NEXT”. Moreover, NEXT ratings are typically specified for mated connector configurations, for example, a type RJ-45 plug and jack combination, wherein input terminals of the plug connector are used as a reference plane.

[0008] Communication links using unshielded twisted pairs (UTP) of copper wire are now expected to support data rates up to not only 100 MHz, or industry standard “Category 5” performance; but to meet “Category 6” performance levels which call for at least 46 dB near end crosstalk loss at 250 MHz.

[0009] Crosstalk compensating circuitry may also be provided on or within layers of a printed wire board, to which spring terminal contact wires of a communication jack are connected within the jack, housing. See U.S. patent application Ser. No. 08/923,741 filed Sep. 29, 1997, and assigned to the assignee of the present application and invention. All relative portions of the '741 application are incorporated by reference herein. See also U.S. Pat. No. 5,299,956 (Apr. 5, 1994).

[0010] U.S. Pat. No. 5,547,405 (Aug. 20, 1996) discloses an electrical connector having signal carrying contacts that are formed on different lead frames. Contacts from one lead frame have integral lateral extensions that overlie enlarged adjacent portions of contacts from another lead frame, to provide capacitive coupling. A dielectric spacer is assembled between an extension of one contact, and an enlarged adjacent portion of another contact. Thus, the signal carrying contacts in the connector of the '405 patent require tooling for two different lead frames, and the contacts must be properly aligned with the dielectric spacer between them during assembly of the connector.

[0011] There remains a need for a communications jack connector which, when mated with a typical RJ-45 plug connector, provides such crosstalk compensation that the mated connectors meet or surpass Category 6 performance. It would be especially desirable if such a connector could be manufactured using existing components as much as possible, and without expensive tooling or assembly requirements.

[0012] According to the invention, a capacitor compensation assembly for crosstalk compensation in a communication connector, includes a housing and a crosstalk compensation capacitor supported in the housing. The capacitor has a first metallic electrode with a first terminal, a second metallic electrode with a second terminal, and a dielectric spacer disposed between the electrodes. The housing is dimensioned and arranged to be associated with a communication connector having elongated terminal contact wires. The terminals of the electrodes are exposed at positions outside the housing such that selected terminal contact wires of the connector make electrical contact with corresponding terminals of the electrodes to provide capacitive coupling between the selected terminal contact wires when the contact wires are engaged by a mating connector.

[0013] According to another aspect of the invention, a communications jack connector includes a jack frame having a front surface, and a plug opening in the front surface for receiving a mating plug connector. A number of elongated terminal contact wires extend through the jack frame, and the contact wires are configured to make electrical contact with corresponding terminals of the mating connector. One or more crosstalk compensation capacitors are mounted in operative relation to the terminal contact wires. Each capacitor includes a first electrode with a first terminal, a second electrode with a second terminal, and a dielectric spacer disposed between the first and the second electrodes. The terminals of the electrodes are located and configured so that free end portions of selected terminal contact wires make electrical contact with corresponding terminals of the electrodes to provide capacitive coupling between the selected terminal contact wires when the contact wires are engaged by the mating connector.

[0014] For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawing and the appended claims.

[0015] In the drawing:

[0016] FIG. 1 is an exploded view of a high frequency communication jack connector;

[0017] FIG. 2 is an enlarged, exploded view of a capacitor compensation assembly for providing capacitive crosstalk compensation coupling in the jack connector of FIG. 1;

[0018] FIG. 3 is an enlarged perspective view of the capacitor compensation assembly in FIG. 2, in an assembled state;

[0019] FIG. 4 is an enlarged, side view of the jack connector in FIG. 1 in a partly assembled state, and showing a mating plug connector;

[0020] FIG. 5 is a perspective view of the jack connector in FIG. 4 as seen from the front, showing free end portions of selected terminal contact wires in electrical contact with corresponding terminals of the capacitor compensation assembly;

[0021] FIG. 6 is an electrical schematic diagram of the jack connector in FIGS. 4 & 5 including the capacitor compensation assembly.

[0022] FIG. 1 is an exploded view of a high frequency communication jack connector 10. The jack connector 10 includes a jack frame 40, and a printed wire board 12 having one or more dielectric layers. The board layers may have conductive traces or paths printed on them in certain configurations to provide one or more stages of crosstalk compensation, as disclosed in the earlier-mentioned '741 application. Alternatively or in addition to conductive traces, the wire board 12 may have associated discrete components such as resistors, capacitors and inductors to compensate for or to reduce crosstalk that would otherwise develop among signal paths through the connector 10.

[0023] A number, for example, eight elongated spring terminal contact wires 16ato 16hextend parallel to one another from beneath the board 12, and are directed with a certain bend radius around a jackwire block 18 near a front edge 20 of the board. Parallel free end portions of the contact wires 16a-16hform an acute angle relative to the top surface of the wire board 12, so as to confront and to make electrical contact with corresponding terminals of a mating plug connector when the latter is received in a plug opening 42 in the jack frame 40 (see FIG. 4). A typical center-to-center spacing between adjacent terminal contact wires is about 0.040 inches.

[0024] Base portions of the terminal contact wires 16a-16hbeneath the wire board 12, are inserted into plated terminal openings 22 in the board. The terminal openings 22 extend through the board layers to connect with the conductive traces or other devices on or within the board. The contact wires 16a-16hare seated in corresponding parallel grooves formed in the leading portion of the jackwire block 18, wherein the bases of the grooves define the bend radius for the contact wires. See co-pending U.S. application Ser. No. 08/904,391 filed Aug. 1, 1997, (now U.S. Pat. No. 5,924,896 issue Jul. 20, 1999), and assigned to the assignee of the present application and invention. All relevant portions of the '391 application are incorporated herein by reference.

[0025] Insulation displacement connector (IDC) terminals 30ato 30hare mounted at either side of a rear portion of the wire board 12, as shown in FIG. 1. The IDC terminals 30a-30hhave mounting parts or “tails” that are press fit or otherwise retained in corresponding terminal openings in the board 12. The IDC terminals 30a-30hare thus electrically connected to the conductive traces on the board layers, and the terminals 30a-30hare associated with corresponding ones of the terminal contact wires 16a-16h. The IDC terminals 30a-30hare further described in the above-mentioned '391 application.

[0026] The jack frame 40 may be similar to the jack frame disclosed in the '391 application. The plug opening 42 in the frame 40 receives a mating plug connector along the direction of a plug axis P through the opening 42. The frame 40 also has a rear opening (see FIG. 4) that is dimensioned to receive a front portion of the wire board 12, including the jackwire block 18 and the parallel free end portions of the terminal contact wires 16a-16h. When the front portion of the wire board 12 is inserted and mounted within the jack frame 40, the free end portions of the terminal contact wires pass through corresponding vertical slots in a “comb”-like rear wall of the jack frame. The rear vertical slots in the jack frame 40 serve to guide the free end portions of the contact wires when they are deflected toward the board 12 by the action of a plug connector. A desired pre-load bias force is also applied to the free end portions of the contact wires at upper ends of the vertical slots. See FIG. 4.

[0027] An electrically insulative or dielectric terminal housing 50 protects the rear top surface portion of the wire board 12, and permits wire lead access to and connection with the IDC terminals 30a-30hon top of the wire board. The terminal housing 50 may be formed of a plastics material that meets all applicable standards with respect to electrical insulation and flammability. Such materials include, but are not limited to, polycarbonate, ABS, and blends thereof.

[0028] The terminal housing 50 has a pair of fastening or mounting posts 52 that project from a bottom surface of the housing, as shown in the drawing. When the housing 50 is aligned with the IDC terminals 30a-30hand is lowered to surround the terminals, the fastening posts 52 align with corresponding openings 54 in the board 12 and pass through the openings 54 to engage a cover 60 on the bottom surface of the board. The wire board 12 is thus sandwiched or captured between the terminal housing 50 and the cover 60, so that substantially the entire rear portion of the board 12 is protected from above and below.

[0029] The jack frame 40 has a latch 64 that projects rearward from a bottom surface of the frame, as viewed in FIG. 1. The wire board cover 60 has a lower shoulder 68 next to a front end of the cover. After the wire board 12, the terminal housing 50 and the cover 60 are assembled, the front portion of the wire board 12 is inserted in the rear opening in the jack frame 40 until the frame latch 64 snaps over and onto the shoulder 68 on the bottom of the cover.

[0030] FIG. 2 is an exploded view of a capacitor compensation assembly 80 for providing crosstalk compensation in the jack connector 10. FIG. 3 is an enlarged perspective view of the compensation assembly 80 in FIG. 2, in an assembled state.

[0031] The capacitor compensation assembly 80 comprises a housing 82 having a first opening or cavity 84, and a second opening or cavity 86. The cavities 84, 86, have relatively narrow, generally rectangular cross-sections of substantially the same dimensions. The cavities are formed in the housing 82 one above the other, but with their side walls offset horizontally by a determined distance d of, for example, 0.040 inches. This offset corresponds to the mentioned center-to-center spacing of adjacent free end portions of the terminal contact wires 16a-16habove the wire board 12.

[0032] In the disclosed embodiment, the capacitor compensation assembly 80 has two crosstalk compensation capacitors 88, 90. Each of the capacitors 88, 90, is comprised of a first metallic electrode 92 and a second metallic electrode 94. Each of the electrodes 92, 94, may be in the form of a metal plate as shown, or other equivalent form or configuration. The first electrode 92 has an associated conductive finger terminal 96, and the second electrode 94 has an associated conductive finger terminal 98. Further, each of the capacitors 88, 90, has an associated dielectric spacer 100 which is disposed between the first and the second metallic electrodes 92, 94.

[0033] In the illustrated embodiment, the first and the second electrodes 92, 94, are generally rectangular metal plates. The first electrode 92 may be longer on each side by, e.g., 0.01 inches than the second electrode 94, however. In such a case, since the second electrode 94 has a smaller area than the first electrode 92, precise alignment of the electrodes with one another is not essential to obtain a desired capacitance value between the electrode terminals, and production variations are minimized. That is, as long as the entire area of the smaller, second electrode 94 is disposed opposite an area of the first electrode 92 through the dielectric spacer 100, the capacitance value remains constant. See U.S. patent application Ser. No. 09/327,882 entitled Enhanced Communication Connector Assembly with Crosstalk Compensation, filed Jun. 8, 1999, and assigned to the assignee of the present application. All relevant portions of the '882 application are incorporated by reference.

[0034] The dielectric spacer 100 provides isolation between the metallic electrodes 92, 94. The spacer should be capable of withstanding an industry-specified breakdown voltage, for example, 1000 volts.

[0035] With the dielectric spacer 100 sandwiched between the first and the second electrodes 92, 94, of the compensation capacitors 88, 90, the two capacitors are inserted in the cavities 84, 86, in the assembly housing 82. As seen in FIG. 2, the side, top and bottom walls of the cavities 84, 86, conform closely to the outer peripheries of the capacitors 88, 90, so that the electrodes 92, 94, and the dielectric spacer of each capacitor are supported steadily with respect to the housing 82. The depth of the cavities 84, 86, in the housing 82 is such that the finger terminals 96, 98, of the capacitors are exposed and extend with a desired configuration outside of the housing 82. Because of the horizontal offset distance d in the relative alignment of capacitors 88, 90, the finger terminals 96, 98, of one capacitor are offset horizontally by the distance d with respect to the corresponding finger terminals of the other capacitor, as seen in FIG. 3.

[0036] FIG. 3 also shows an arrangement wherein the metallic electrodes 92, 94, of the capacitors can be insert molded in the housing 82. Specifically, a tab 110 is formed integrally with and projects from the right side of each electrode 92, as viewed in FIG. 3. A corresponding tab (not shown in FIG. 3) projects from the left side of each electrode 92. Likewise, a tab 112 is formed integrally with and projects from the right side of each capacitor electrode 94, and a corresponding tab projects from the left side of each electrode 94. The tabs 110, 112, thus serve to align and hold the electrodes 92, 94, in position within a molding die during an injection molding process for the assembly housing 82. lifter molding, the tabs may be trimmed flush with the sides of the assembly housing 82 as seen in FIG. 3.

[0037] FIG. 1 shows the assembled capacitor compensation assembly 80 captured in a recess 120 that is formed in a front wall 122 of the IDC terminal housing 50. The assembly 80 may thus be clamped on or otherwise fixed with respect to the top of the printed wire board 12 and the free end portions of the terminal contact wires 16a-16h. FIGS. 4 and 5 show the capacitor compensation assembly 80 in the jack connector 10, in operative relation to the free end portions of the terminal contact wires. Parts of the connector 10 are omitted in FIGS. 4 and 5 for purposes of clarity. As shown in FIG. 5, the crosstalk compensation capacitors 88, 90, are supported in the assembly housing 82 so that the terminals 96, 98, of each capacitor are each aligned with a corresponding one of the terminal contact wires of the connector 10, in a direction that is generally transverse to the free end portions of the terminal contact wires 16a-16h, outside of the assembly housing 82.

[0038] When a typical plug connector 130 is inserted in the front plug opening 42 in the jack frame 40, terminals blades of the plug connector confront the terminal contact wires 16a-16h, and apply a force sufficient to overcome the pre-loading of the free end portions of the contact wires at the rear of the jack frame 40. The finger terminals 96, 98, of the capacitor compensation assembly 80 are located and configured outside of the assembly housing 82, so that free end portions of selected terminal contact wires make electrical contact with corresponding finger terminals 96, 98, of the compensation capacitors 88, 90, when the free end portions are deflected or urged toward the finger terminals by the action of the plug connector.

[0039] Once the end portions of the selected terminal contact wires touch the finger terminals 96, 98, the associated contact wires may be further deflected at their points of contact with the blades of the plug connector 130 to cause a slight wiping movement of the wire end portions on the capacitor finger terminals 96, 98. Such wiping action assures a reliable electrical contact between the selected terminal contact wires and the corresponding capacitor terminals.

[0040] FIG. 6 is a schematic representation of the jack connector 10 with the capacitor compensation assembly 80 arranged as shown in FIG. 5. In the illustrated embodiment, the finger terminals 96, 98, of capacitor 88 are positioned to contact the free ends of terminal contact wires 16c& 16e. The finger terminals 96, 98, of capacitor 90 are arranged to contact the free ends of contact wires 16d& 16f. Thus, the spacing between the finger terminals 96, 98, of each compensation capacitor 88, 90, corresponds to twice the center-to-center distance between adjacent end portions of the terminal contact wires 16a-16h.

[0041] For example, in type RJ-45 connectors, contact wire pair 16dand lie is used as signal wire pair “1”, and contact wire pair 16cand 16fis used as signal wire pair “3”. The arrangement or FIGS. 5 and 6 thus provides capacitive coupling between the pair 1 and the pair 3 signal wires for the purpose of crosstalk compensation. The capacitive coupling is injected at free ends of the contact wires with respect to their points of contact with the plug connector 130, rather than at current-carrying parts of the wires. This minimizes the effect of delay in the injection of capacitive compensation coupling into the selected signal paths.

[0042] It is believed that Category 6 near end crosstalk loss may be achieved when the connector 10 is mated with a typical existing type RJ-45 plug connector, if the value of each compensation capacitor is between about 0.5 picofarads (pf) and 3.0 pf, and up to two additional stages of crosstalk compensation are provided within the wire board 12. The final value of each capacitor should reflect an optimum balance of compensation provided by both the wire board 12 and the compensation capacitors 88, 90.

[0043] The communication jack connector disclosed herein features a capacitor compensation assembly that is disposed relatively close to the points of contact of the connector 10 with a mating connector. This arrangement provides an early stage of capacitive compensation and allows additional free space on the wire board 12 for “fine tuning” of the electrical performance of the connector 10 by way of further crosstalk compensation stages. The capacitor compensation assembly 80 may be mounted in the region of a back end of an existing jack frame such as those currently used in jack connectors available from Lucent Technologies Inc. under the style designation “MGS200”. Because of its compatibility with existing jack connectors, the capacitor compensation assembly 80 can be integrated with such connectors with a minimal amount of up-front tooling time or expense.

[0044] While the foregoing description represents a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made, without departing from the true spirit and scope of the invention pointed out in the following claims.