Modular jack for low crosstalk electrical connector

[0001] The present invention relates to an electrical connector; and, more particularly, to a modular jack of an electrical connector implementing a low crosstalk.

[0002] A communications terminal used in an office or home is electrically connected to an outdoor transmission cable via an electrical connector, which usually includes a modular jack and a plug. Though a four-pin connector has been widely used for the communications terminal, an eight-pin connector is now being developed to satisfy the need for a high transmission speed. Telecommunication Industry Association (TIA) and Electronic Industry Association (EIA) of U.S. are specifying Category 6, a new industrial specification, to keep up with a rapid development of communication parts including the eight-pin connector.

[0003] In a transmission cable, each pair of lines forms a signal pair to transmit a specific electrical signal. If a signal pair transmitting a first signal is adjacent to another pair transmitting a second signal, a capacitive coupling and an inductive coupling are induced between the first and the second signal, thereby causing an error in the signals. Such an electromagnetic interference between two adjacent signals is referred to as a crosstalk.

[0004] As shown in FIG. 1, an insert 2 of a conventional eight pin modular jack (not shown) includes an insert housing 4 and eight insert conductors R1 to R4 and T1 to T4. The insert conductors R1 to R4 and T1 to T4 are arranged to run parallel to each other on one plane while maintaining a constant pitch therebetween. Portions of the insert conductors are embedded in the insert housing 4 serving to maintain relative positions thereof.

[0005] Such a single level arrangement of the insert conductors causes significant crosstalks both inside and outside the insert housing 4. Therefore, an electrical connector adopting the conventional modular jack can hardly satisfy specifications of Category 6.

[0006] In FIG. 2, there is illustrated a schematic arrangement of the conventional insert conductors R1 to R4 and T1 to T4 in order to explain the crosstalks therebetween, herein only a few capacitive coupling components are depicted for the sake of simplicity.

[0007] In the drawing, a first conductor R1 and a second conductor T1 form a first signal pair to transmit a first signal; a fourth conductor T2 and a fifth conductor R2 form a second signal pair for a second signal; a third conductor R3 and a sixth conductor T3 form a third signal pair for a third signal; and a seventh conductor R4 and an eighth conductor T4 form a fourth signal pair for a fourth signal. The second conductor T1 and the third conductor R3 are adjacent to each other and transmit different signals, i.e., the first signal and the third signal, respectively. Therefore, a strong electromagnetic coupling is induced between the first signal of the second conductor T1 and the third signal of the third conductor In other words, a first capacitance C13 is induced between the first conductor R1 and the third conductor R3 while a second capacitance C23 is induced between the second conductor T1 and the third conductor R3. The second capacitance C23 is larger than the first capacitance C13 (C23>C13), because the capacitance is inversely proportional to a distance between two conductors and the third conductor R3 is closer to the second conductor T1 than the first conductor R1 is. The above-explained capacitance difference causes an electrical potential difference between the second conductor T1 and the third conductor R3, thereby increasing the capacitive coupling of the first signal of the second conductor T1 and the third signal of the third conductor R3.

[0008] Further, a third capacitance C16 is induced between the first and sixth conductor R1 and T3. However, because the sixth conductor T3 is located relatively very far away from the first conductor R1, the third capacitance C16 is very small and an effect thereof can be disregarded.

[0009] Like the second and the third conductor T1 and R3, if two conductors are respectively involved with different signal pairs but electromagnetically coupled, they are referred to as a crosstalk pair. The crosstalk mainly occurs between the conductors of the crosstalk pairs, such as T1-R3, R3-T2, R2-T3, and T3-R4.

[0010] Though the previous explanation is focused on the first to the third capacitances C13, C23 and C16, other capacitances including a fourth to a sixth capacitances C12, C36 and C26 are also induced among the insert conductors. A detailed explanation about the fourth to the sixth capacitances, however, is omitted for the sake of simplicity.

[0011] The U.S. Pat. No. 5,299,956 teaches a method for preventing the crosstalk. In the method in accordance with the above-mentioned U.S. patent, an opposite electromagnetic coupling is induced to cancel the inductive or capacitive coupling. With reference to FIG. 3, the purport of the U.S. Pat. No. 5,299,956 will be explained.

[0012] As shown, a first signal pair S1 includes a first tip conductor T1 and a first ring conductor R1 while a second signal pair S2 includes a second tip conductor T2 and a second ring conductor R2. In a first portion Z1, the second tip conductor T2 and the second ring conductor R2 are disposed adjacent to the first ring conductor R1 and the first tip conductor T1, respectively. In a second portion Z2, however, positions of the second tip and the second ring conductor T2 and R2 are interchanged with each other, such that the second ring conductor R2 and the second tip conductor T2 are disposed adjacent to the first ring conductor R1 and the first tip conductor T1, respectively.

[0013] In the above-described configuration, a first crosstalk occurs between the first and the second signal pair S1 and S2 in the first portion Z1 while a second crosstalk occurs therebetween in the second portion Z2. Because of the above-mentioned interchange of positions in the second portion Z2, the first crosstalk and the second crosstalk have opposite phases, thereby canceling each other.

[0014] That is to say, first inductive and the first capacitive coupling induced in the first portion Z1, and second inductive and second capacitive couplings induced in the second portion Z2 have phases opposite to each other. Accordingly, the first inductive and the first capacitive coupling are canceled by the second inductive and the second capacitive coupling, such that a total crosstalk is reduced.

[0015] The method in accordance with the prior art can provide a simple configuration for a low crosstalk electrical connector by way of simultaneously canceling each of the capacitive coupling and the inductive coupling in the same portion. For the same reason, however, at least one of the capacitive coupling and the inductive coupling cannot be wholly canceled and a considerable amount of the crosstalk still remains.

[0016] The crosstalk cannot be actually reduced below a level of 46 dB even if the above-explained method is employed, if the transmission frequency of signal is around 250 MHz. That is to say, though a higher transmission frequency is required as the data transmission speed increases, the method in accordance with the prior art can rarely satisfy newly required specifications.

[0017] It is, therefore, an object of the present invention to provide a modular jack for an electrical connector that implements a low crosstalk for transmitting high frequency signals.

[0018] In accordance with one aspect of the invention, a preferred embodiment of the present invention provides a modular jack for a low crosstalk electrical connector, the jack including: a housing; a first signal pair passing through the housing and including a first conductor and a second conductor, a first imaginary plane containing the first and the second conductor; and a second signal pair passing through the housing and including a third conductor and a fourth conductor, a second imaginary plane containing the third and the fourth conductor, which are bent at least once to cross each other inside the housing, wherein the first and the second imaginary plane form a first angle of 80 to 90 degrees inside the housing before the crossing of the third and the fourth conductor while the first and the second imaginary plane form a second angle of 0 to 10 degrees inside the housing after the crossing thereof.

[0019] Another preferred embodiment of the present invention provides an insert of a crosstalk reducing modular jack, the insert including: an upper housing; a lower housing joined with the upper housing, the upper and the lower housing being symmetrical to each other with respect to a contact surface therebetween; an upper set including a first to a fourth tip conductor passing through the upper housing and being arranged on a plurality of levels, the third tip conductor having a first and a second protrusion protruded toward the second and the fourth tip conductor, respectively; and a lower set positioned under the upper set, the lower set including a first to a fourth ring conductor passing through the lower housing and being arranged on a plurality of another levels, the second ring conductor having another first and another second protrusion protruded toward the first and third ring conductor, respectively; a first air space interposed between the upper and the lower set; a second air space surrounding a portion of the first tip conductor inside the upper housing; and a third air space surrounding a portion of the fourth ring conductor inside the lower housing.

[0020] In accordance with another aspect of the invention, another preferred embodiment of the present invention provides a low crosstalk connector including: a first portion where an inductive coupling and a capacitive coupling are induced between adjacent lines, each independently transmitting a signal; a second portion where capacitances induced between the adjacent lines are selectively compensated to reduce the capacitive coupling; and a third portion where an opposite inductive coupling is induced between the adjacent lines to cancel the inductive coupling, wherein the inductive coupling of the second portion is minimized while the opposite inductive coupling of the third portion is maximized.

[0021] The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

[0022] FIG. 1 is a perspective view showing an insert of a modular jack of an electrical connector in accordance with a prior art;

[0023] FIG. 2 is a cross-sectional view illustrating a single level arrangement of conductors of the insert shown in FIG. 1;

[0024] FIG. 3 is a conceptual circuit diagram illustrating a conventional method for reducing a crosstalk;

[0025] FIG. 4 is a disassembled perspective view illustrating an electrical connector in accordance with the present invention;

[0026] FIG. 5 is a partial sectional perspective view showing a modular jack of the electrical connector shown in FIG. 4;

[0027] FIG. 6 is a perspective view showing a plug of the electrical connector shown in FIG. 4;

[0028] FIG. 7 is an expanded perspective view showing an arrangement of plug conductors of the plug shown in FIG. 6;

[0029] FIG. 8 is a perspective view showing the insert in accordance with a first preferred embodiment of the present invention;

[0030] FIG. 9 is a perspective view showing only an upper and a lower insert housing of FIG. 8;

[0031] FIGS. 10A and 10B are sectional views taken along a line A-A of FIG. 9, respectively;

[0032] FIGS. 11A and 11B are plan views showing insert conductors in accordance with the first preferred embodiment of the present invention;

[0033] FIGS. 12A and 12B are plan views showing an upper insert housing assembled with tip conductors of FIG. 11A and a lower insert housing assembled with ring conductors of FIG. 11B, respectively;

[0034] FIG. 13 is a plan view showing an assembly of the upper and the lower insert housing of FIGS. 12A and 12B;

[0035] FIG. 14 is a cross-sectional view illustrating a double level arrangement of the insert conductors shown in FIGS. 11A and 11B;

[0036] FIGS. 15A and 15B are perspective views illustrating an insert in accordance with a second preferred embodiment of the present invention;

[0037] FIG. 16 is a cross-sectional view illustrating a multi-level arrangement of insert conductors of FIGS. 15A and 15B;

[0038] FIG. 17 is a disassembled perspective view illustrating the insert conductors of FIGS. 15A and 15B;

[0039] FIG. 18 is a perspective view illustrating a magnetic field produced from the plug conductors of FIG. 7;

[0040] FIG. 19 is a circuit diagram illustrating an inductive coupling induced between adjacent signal pairs of the plug conductors shown in FIG. 18;

[0041] FIG. 20 is a circuit diagram illustrating a crosstalk-canceling system in accordance with the second preferred embodiment of the present invention;

[0042] FIGS. 21A and 21B are expanded perspective views illustrating the multi-level arrangement of the insert conductors shown in FIG. 17; and

[0043] FIG. 22 illustrates an equivalent circuit that corresponds to the insert of FIGS. 15A and 15B.

[0044] Referring now to FIGS. 4 to 22, preferred embodiments of the present invention will be explained in detail. Like reference numerals represent like parts in FIGS. 4 to 22.

[0045] In FIG. 4, an electrical connector 8 in accordance with preferred embodiments of the present invention includes a modular jack 10 and a plug 200. The modular jack 10 and the plug 200 are electrically connected with an outdoor cable (not shown) and a terminal cable 220, respectively. The plug 200 has a plurality of guide grooves 210. The modular jack 10 includes a case 230, a printed circuit board (PCB) 240, an insert 12, and a connecting portion 250. Further, the insert 12 has an insert housing 20 and a plurality of insert conductors 22 fixed by the insert housing 20.

[0046] The insert 12 and the connection portion 250 are mounted on a surface of the PCB 240 and contained in the case 230. The PCB 240 contains a plurality of electrical lines (not shown), which electrically connect the plurality of the insert conductors 22 with the connecting portion 250. The case 230, the insert 12, the PCB 240, and the connecting portion 250 are assembled together so as to form the modular jack 10.

[0047] FIG. 5 shows a modification of the modular jack 10 shown in FIG. 4. As shown, the insert 12 and the connecting portion 250 are mounted on a front surface and a rear surface of the PCB 240, respectively, and the case 230 contains the insert 12 and the PCB 240. The insert housing 20 is made of a synthetic resin and the insert conductors 22 pass through the insert housing 20. Inside the insert housing 20, the plurality of the insert conductors 22 have a multi-level arrangement where at least one insert conductor 22 is arranged on a different level. A double level arrangement of FIG. 5 is an example of the multi-level arrangement.

[0048] Outside the insert housing 20, a first end and a second end of each insert conductor 22 are protruded from a front surface and a rear surface of the insert housing 20, respectively. The first end of each insert conductor 22 is bent upward with respect to the insert housing 20. When the plug 200 (FIG. 4) and the modular lack 10 are connected together, the first end of each insert conductor 22 makes an electrical contact with a corresponding plug conductor 212 (FIG. 6) of the plug 200 (FIG. 6). On the other hand, the second end of each insert conductor 22 is electrically connected with the PCB 240.

[0049] In FIG. 6, the plug 200 includes a plurality of plug conductors 212. Each of the plug conductors 212 makes an electric contact with a corresponding insert conductor 22 (FIG. 5) when each insert conductor is introduced into a corresponding guide groove 210 of the plug 200. That is to say, returning to FIG. 4, if the plug 200 is inserted into the case 230 of the modular jack 10, each plug conductor 212 makes an electric contact with a corresponding insert conductor 22, such that the plug 200 and the modular jack 10 are electrically connected.

[0050] FIG. 7 shows the plug conductors 212 of the plug 200 (FIG. 6) in an expanded view. A first plug conductor PR1 and a second plug conductor PT1 form a first signal pair for transmitting a first signal; a fourth plug conductor PT2 and a fifth plug conductor PR2 form a second signal pair for a second signal; a third plug conductor PR3 and a sixth plug conductor PT3 form a third signal pair for a third signal; and a seventh plug conductor PR4 and an eighth plug conductor PT4 form a fourth signal pair for a fourth signal.

[0051] The second plug conductor PT1 and the third plug conductor PR3 are adjacent to each other and transmit different signals after contacting corresponding insert conductors. Therefore, the second plug conductor PT1 and the third plug conductor PR3 form a crosstalk pair PT1-PR3 where a crosstalk occurs. For the same reason, each of pairs PR3-PT2, PR2-PT3, and PT3-PR4 forms a crosstalk pair.

[0052] Hereinafter, there will be described an insert 12 in accordance with a first preferred embodiment of the present invention. The insert 12 is capable of removing or significantly reducing the crosstalk, by way of adopting capacitance compensation and the double level arrangement.

[0053] In FIG. 8, the insert 12 in accordance with the first preferred embodiment of the present invention includes the insert housing 20 and the plurality of the insert conductors 22. The plurality of the insert conductors 22 have a first to a fourth tip conductors T1 to T4 positioned on an upper level and a first to a fourth ring conductors R1 to R4 positioned on a lower level. The insert housing 20 has an upper insert housing 20a and a lower insert housing 20b, as shown in FIG. 9. The insert conductors 22 are not illustrated in FIG. 9 for the sake of convenience.

[0054] FIG. 10A is a cross-sectional view taken along a line A-A of FIG. 9, wherein it is assumed that the tip conductors T1 to T4 and the ring conductors R1 to R4 are present and are assembled with the insert housing 20.

[0055] The upper and the lower insert housing 20a and 20b include an upper and a lower opening portion 34 and 36, respectively, and are joined together so as to form the insert housing 20. The upper and the lower opening portion 34 and 36 expose portions of the first tip conductor T1 and the fourth ring conductor R4, respectively, such that the portions of the first tip conductor T and the fourth ring conductor R4 are surrounded by air. Because the air has a much lower dielectric constant than the upper insert housing 22a or lower insert housing 22b has, capacitances induced in relation with the first tip conductor T1 or the fourth ring conductor R4 are relatively much smaller.

[0056] Further, the insert housing 20 formed by joining the upper and the lower insert housing 20a and 20b includes an air space 42, which is formed between the upper and the lower insert housing 20a and 20b. The air space 42 serves as a low dielectric layer, thereby reducing each capacitance induced between one of the tip conductors T1 to T4 and one of the ring conductors R1 to R4. For forming the air space 42, the upper and the lower insert housing 20a and 20b respectively have opposing concavities. After the upper and the lower insert housing 20a and 20b are joined together, the opposing concavities form the air space 42.

[0057] As shown in FIG. 10B, a first inner groove 35 and a second inner groove 37 may substitute for the upper and the lower opening portion 34 and 36 of FIG. 10A, respectively. Portions of the first tip conductor T1 and the fourth ring conductor R4 are also surrounded by air inside the upper and the lower insert housing 20a and 20b, but in this case, they are isolated from an outer circumstance.

[0058] If the upper insert housing 20a or the lower insert housing 20b is turned over, the upper and the lower insert housing 20a and 20b have same shapes. That is to say, the upper and the lower insert housing 20a and 20b are fabricated to have the same shapes but used as different parts, such that a fabrication cost thereof can be reduced.

[0059] The inner grooves 35 and 37, or the opening portions 34 and 36, and the air space 42 correlate with compensating portions 26 (FIGS. 11A and 11B), such that capacitances induced between adjacent conductors are selectively compensated so as to reduce the crosstalk. The compensating portions 26 and the above-mentioned selective compensation of the capacitances will be later explained in more detail.

[0060] Referring to FIGS. 11 to 13, a configuration of the insert 12 in accordance with the first preferred embodiment of the present invention will be described in connection with a fabrication process thereof.

[0061] In FIGS. 11A and 11B, the first to the fourth tip conductors T1 to T4 are included in an upper set 22a while the first to the fourth ring conductors R1 to R4 are included in a lower set 22b. Each of the upper and the lower set 22a and 22b includes a spring portion 24, the compensating portion 26 and a PCB-connecting portion 28. After the plug 200 (FIG. 4) is inserted into the modular jack 10 (FIG. 4), each insert conductor electrically contacts a corresponding plug conductor 212 (FIG. 6) in the spring portion 24. In the PCB-connecting portion 28, each insert conductor is electrically connected with the PCB 240 (FIG. 4) by way of applying a soldering or the like.

[0062] Two holding portions 30, each having a carriage hole 32 passing therethrough, hold, respectively, a first and a second end of the upper and the lower set 22a and 22b. After the upper and the lower set 22a and 22b are assembled with the upper and the lower insert housing 20a and 20b (FIG. 9), respectively, the holding portions 30 are separated therefrom.

[0063] The first to the fourth tip conductors T1 to T4 correspond to the first to the fourth ring conductors R1 to R4, respectively, thereby forming independent signal pairs T1-R1, T2-R2, T3-R3 and T4-R4. The third tip conductor T3 has a first protrusion T3a and a second protrusion T3b positioned at the compensating portion 26. The third ring conductor R3 has another first protrusion R3a and another second protrusion R3b positioned at the compensating portion 26. Each of the protrusions T3a, R3a, T3b and R3b serves to increase capacitances induced between adjacent conductors. Each compensating portion 26 is positioned inside the upper insert housing 20a of FIG. 14 or the lower insert housing 20b of FIG. 14.

[0064] If the upper set 22a or the lower set 22b is turned over, the upper and the lower set 22a and 22b have same shapes. That is to say, the upper and the lower set 22a and 22b are fabricated to have the same shapes but used as different parts, such that a fabrication cost thereof can be reduced.

[0065] In FIGS. 12A and 12B, the upper insert housing 20a and the lower insert housing 20b are formed by way of molding, wherein the compensating portions 26 of the upper and the lower set 22a and 22b are positioned inside the upper housing 20a and the lower housing 20b, respectively. The upper and the lower insert housing 20a and 20b are preferably made of PBTGF 030% (polyethylene terephthalateglass fiber). At this point, a dielectric constant of the upper and the lower insert housing 20a and 20b is preferably about 3.6 to 4.0.

[0066] Each of the upper and the lower insert housing 20a and 20b has males and females 38 and 40, which are formed on each opposing surface of the upper and the lower insert housing 20a and 20b. The males 38 are forced into the females 40, such that the upper and the lower insert housing 20a and 20b can be joined together. As shown in FIG. 13, after the upper and the lower housing 20a and 20b are joined together, the ring conductors R1 to R4 and the tip conductors T1 to T4 are alternately arranged at outside of the insert housing 20.

[0067] As previously mentioned, the opening portions 34 and 36, or the inner grooves 35 and 37 (FIG. 10B), and the air space 42 (FIGS. 10A and 10B) correlate with compensating portions 26, such that capacitances induced between adjacent conductors are selectively compensated so as to reduce the crosstalk.

[0068] Referring to FIG. 14, the selective compensation for the capacitances induced inside the insert housing 20 will be explained in more detail.

[0069] The tip conductors T1 to T4 are arranged on the upper level while the ring conductors R1 to R4 are arranged on the lower level, thereby forming the double level arrangement. For the sake of convenience, the protrusions T3a, R3a, T3b and R3b (FIGS. 11A and 11B) are not illustrated, and an interval interposed between adjacent conductors is assumed constant.

[0070] When signals are respectively applied to the conductors, capacitances are induced between adjacent conductors. For example, a first capacitance C1 is induced between the second tip conductor T2 and the first protrusion T3a (FIG. 11A) of the third tip conductor T3. A second capacitance C2 is induced between the first ring conductor R1 and the first protrusion R3a (FIG. 11B) of the third ring conductor R3. A third capacitance C3 is induced between the fourth tip conductor T4 and the second protrusion T3b (FIG. 11A) of the third tip conductor T3. In addition, a fourth capacitance C4 is induced between the second ring conductor R2 and the second protrusion R3b (FIG. 11B) of the third ring conductor R3.

[0071] Because of the first and the second protrusions R3a, R3b, T3a and T3b (FIGS. 11A and 11B), each of the first to the fourth capacitances C1 to C4 has a relatively larger value. On the contrary, because of the first and the second inner groove 35 and 37 or the opening portions 34 and 36 of FIG. 13A, a relatively smaller capacitance is induced between the first tip conductor T1 or the fourth ring conductor R1 and an adjacent conductor thereof. Further, because of the air space 42 and the double level arrangement, each capacitance induced between one of the tip conductors and one of the ring conductors is much smaller than each of the first to the fourth capacitances C1 to C4.

[0072] The above-described first preferred embodiment of the present invention adopts the double level arrangement so as to focus on reducing the capacitive coupling. However, because the inductive coupling is also present in an electrical connector, a second preferred embodiment of the present invention adopts a multi-level arrangement, thereby reducing both of the capacitive coupling and the inductive coupling.

[0073] Referring now to FIGS. 15 to 22, an insert 112 in accordance with the second preferred embodiment of the present invention will be described in detail.

[0074] In FIGS. 15A and 15B, the insert 112 in accordance with the second preferred embodiment includes an insert housing 120 and a plurality of insert conductors 122, including first to fourth tip conductors T1 to T4 and first to fourth ring conductors R1 to R4. The insert housing 120 has an upper insert housing 120a and a lower insert housing 120b. The upper insert housing 120a is assembled with the first to the fourth tip conductors T1 to T4 and maintains relative positions thereof. Whereas, the lower insert housing 120b is assembled with the first to the fourth ring conductors R1 to R4 and maintains relative positions thereof. In the drawings, a first direction Y directs a front surface of the insert housing 120 while a second direction X directs a rear surface thereof. In other words, the front surface is indicated by a reference letter Y while the rear surface is indicated by a reference letter X.

[0075] FIG. 16 illustrates a cross-section of FIG. 15B. As shown, the insert housing 120 further includes an air space 142 inside. The air space 142 is formed between the upper and the lower insert housing 120a and 120b and has the same shape and effect as those of the air space 42 (FIGS. 10A and 10B) of the first preferred embodiment. The upper and the lower insert housing 120a and 120b, respectively, have a first and a second inner groove 135 and 137, which have the same shape and effect as those of the first and the second inner groove 35 and 37 (FIG. 10B) of the first preferred embodiment, respectively. Alternatively, the first and second inner groove 135 and 137 may be substituted with an upper and a lower opening portion (not shown), respectively. The upper and the lower opening portion (not shown) of the second preferred embodiment have the same shapes and effects as those of the upper and the lower opening portion 34 and 36 (FIG. 10A) of the first preferred embodiment.

[0076] Returning to FIGS. 15A and 15B, each of the insert conductors 122 passes through the insert housing 120 and bends at the front and the rear surface Y and X of the insert housing 120. Inside the insert housing 120, at least two insert conductors are arranged on different levels.

[0077] Referring to FIG. 17 as well as FIG. 16, a configuration of the insert 112 will be explained.

[0078] The third tip conductor T3 is on a first level, which is a top level. The other tip conductors T1, T2 and T4 are on a second level, which is below the first level. The first, second and fourth ring conductors R1, R2 and R4 are on a third level, which is below the second level. Further, the third ring conductor R3 is on a fourth level, which is a bottom level.

[0079] The third tip conductor T3 has a first protrusion T3a and a second protrusion T3b while the third ring conductor R3 has another first protrusion R3a and another second protrusion R3b. The second and the fourth tip conductor T2 and T4 have a third and a fourth protrusion T2a and T4a, respectively. In addition, the first and the second ring conductor R1 and R2 have another third and another fourth protrusion R1a and R2a, respectively. The third protrusions T2a and R1a preferably correspond to centers of the first protrusions T3a and R3a, respectively. The fourth protrusions T4a and R2a preferably correspond to centers of the second protrusions T3b and R3b, respectively.

[0080] In addition, each of the second tip conductor T2 and the second ring conductor R2 is bent at least one time, such that the second tip and the second ring conductor T2 and R2 cross each other and exchange their positions. Consequently, if the second ring conductor R2 and the second tip conductor T2 are sequentially arranged in that order at the front surface Y of the insert housing 120, the second tip conductor T2 and the second ring conductor R2 are sequentially arranged in that order at the rear surface X thereof.

[0081] Before a more detailed explanation is given about the multi-level arrangement of the insert conductors 122 in accordance with the second preferred embodiment, the inductive coupling will be explained in detail.

[0082] FIG. 18 illustrates a magnetic field induced in the plug conductors 212 that are previously explained with reference to FIG. 7. If the third signal is applied to the third signal pair PT3-PR3, the magnetic field is induced along the sixth and the third plug conductor PT3 and PR3. The magnetic field affects the second signal pair PT2-PR2, thereby forming the inductive coupling between the second signal pair PT2-PR2 and the third signal pair PT3-PR3.

[0083] A more detailed explanation about the inductive coupling will be provided with reference to FIG. 19.

[0084] The sixth plug conductor PT3 and the third plug conductor PR3 form a first closed circuit with a termination resistance R and a signal source P. The fourth plug conductor PT2 and the fifth plug conductor PR2 form a second closed circuit with another termination resistance R and another signal source P. If a first current I1 is applied to the first closed circuit, a magnetic field is induced along the sixth plug conductor PT3 and the third plug conductor PR3. The magnetic field exerts an electromagnetic effect on a second current I2 applied to the fourth and the fifth plug conductor PT2 and PR2 of the second closed circuit, thereby jamming the second current I2. That is to say, the inductive coupling is induced between the first and the second current I1 and I2 that are respectively transmitted along the adjacent plug conductors.

[0085] Referring to FIG. 20, a system for sequentially reducing the capacitive coupling and the inductive coupling will be explained.

[0086] As shown, the third tip conductor T3 and the third ring conductor R3 form another first closed circuit with another termination resistance R and signal source P. The second tip conductor T2 and the second ring conductor R2 form another second closed circuit with a termination resistance R and a signal source P. Each closed circuit, or each insert conductor has first to fourth portions Z1 to Z4, and the second and the third portions Z2 and Z3 are positioned inside the insert housing 120. The insert conductors 122 (FIG. 15A) are electrically connected with the plug conductors 212 (FIG. 18) at the first portion Z1. On the other hand, the insert conductors 122 (FIG. 15A) are electrically connected with the PCB 250 (FIG. 5) at the fourth portion Z4.

[0087] A first current I1 is applied to the first closed circuit at the first portion Z1 while a second current I2 is applied to the second tip conductor T2 of the second closed circuit. Capacitances are induced between adjacent insert conductors because of the first and the second current IT and T2. The capacitances between the adjacent insert conductors are selectively compensated at the second portion Z2. A first capacitance C1 and a second capacitance C2 are results of the selective compensation, which is explained in detail in the first preferred embodiment.

[0088] The second tip conductor T2 and the second ring conductor R2 cross each other at the third portion Z3, such that positions thereof are exchanged at the fourth portions Z4. The first current I1 of the third ring conductor R3 causes a first magnetic field M1 while the first current I1 of the third tip conductor T3 causes a second magnetic field M2. The first and the second magnetic field M1 and M2 have opposite directions. The first magnetic field M1 electromagnetically affects the second current I2 at the first portion Z1, thereby forming a first inductive coupling between the first and the second current I1 and I2. Then, because of the position exchange at the third portion Z3, the second magnetic field M2 electromagnetically affects the second current I2 at the fourth portion Z4, thereby forming a second inductive coupling between the first and the second current I1 and I2. At this point, because the first and the second magnetic field M1 and M2 have opposite directions, the first and the second inductive coupling also have opposite phases, thereby canceling each other.

[0089] Because the first portion Z1 usually has a greater length than the second portion Z1 has, a sum of the first inductive coupling is also larger than that of the second inductive coupling. Therefore, it is preferred that the second inductive coupling induced at the fourth portion Z4 is maximized.

[0090] A third inductive coupling is further induced at the second portion Z2. Because the third inductive coupling has a same phase as the first inductive coupling has, it has an effect of increasing the first inductive coupling. Therefore, unless the third inductive coupling induced at the second portion Z2 is minimized, the fourth portion Z4 should have a greater length than the first portion Z1 has. To prevent the problem, it is preferred that the third inductive coupling induced at the second portion Z2 is minimized.

[0091] With reference to FIGS. 21A and 21B, the above-mentioned minimization and maximization of the inductive coupling is explained in more detail. FIGS. 21A and 21B show a first and a second multi-level arrangement of the insert conductors, respectively.

[0092] The second tip and the second ring conductor T2 and R2 form the first closed circuit on a first imaginary plane 302 while the third tip and the third ring conductor T3 and R3 form the second closed circuit on a second imaginary plane 304. The front surface Y of the insert housing 120 serves as a boundary that divides the first and the second portion Z1 and Z2 of FIG. 20. The rear surface X thereof serves as another boundary that divides the third and the fourth portion Z3 and Z4 of FIG. 20.

[0093] Inside the front surface Y, the first and the second imaginary plane 302 and 304 are perpendicular to each other so as to minimize the third inductive coupling. On the contrary, inside the rear surface X, the first and the second imaginary plane 302 and 304 correspond to each other so as to maximize the second inductive coupling. Preferably, the first and the second imaginary plane 302 and 304 make a first angle of about 80 to 90 degrees at the second portion Z2 of FIG. 20 and a second angle of about 0 to 10 degrees at the fourth portion Z4 of FIG. 20.

[0094] An equivalent circuit for the insert 112 (FIG. 15A) in accordance with the second preferred embodiment is illustrated in FIG. 22. The first ring and the first tip conductor R1 and T1 form a first independent signal pair; the second ring and the second tip conductor R2 and T2 form a second independent signal pair; the third ring and the third tip conductor R3 and T3 form a third independent signal pair; and the fourth ring and the fourth tip conductor R4 and T4 form a fourth independent signal pair.

[0095] The first to the fourth capacitances C1 to C4 formed at the second portion Z2 have a relatively larger value, such that the capacitances induced between the adjacent insert conductors can be selectively compensated. Many other capacitances except for the first to the fourth capacitances C1 to C4 are also induced at the second portion Z2. The other capacitances, however, are much smaller than the first to the fourth capacitances C1 to C4 and are not illustrated for the sake of convenience.

[0096] The second tip conductor T2 and the second ring conductor R2 cross each other at the third portion Z3. Therefore, the second tip conductor T2 and the second ring conductor R3 exchange their positions at the fourth portion Z4.

[0097] If first to fourth signals are respectively applied to the first to the fourth independent signal pairs, a capacitive coupling and an inductive coupling are induced between adjacent signal pairs. For example, the first capacitive and the first inductive coupling are induced at the first portion Z1, and the second capacitive and the second inductive coupling are induced at the fourth portion Z4. The first and the second capacitive coupling are reduced by the selective compensation at the second portion Z2. Further, the first and the second inductive coupling cancel each other because of the position exchanges at the fourth portion Z4.

[0098] The third inductive coupling is further induced at the second portion Z2, and a first multi-level arrangement shown in FIG. 21A minimizes the third inductive coupling. On the contrary, the second inductive coupling is maximized because of a second multi-level arrangement shown in FIG. 21B. That is to say, the first and the second multi-level arrangement provide an optimum condition for the mutual canceling of the first and the second inductive coupling.

[0099] While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.