Impedance compensation for a cable and connector

• US 6,356,162 B1
• Filed: 04/02/1999
• Issued: 03/12/2002
• Est. Priority Date: 04/02/1999
• Status: Expired due to Term

• Current Assignee: Nordx/CDT Inc. (Belden Inc.)
• Original Assignee: Nordx/CDT Inc. (Belden Inc.)
• Inventors: Hoffman, Marc, Cyr, Gary, DeFlandre, Yves
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Glenn, Kimberly E
• Application Number:
  US09/286,113
• Time in Patent Office: 1,075 Days
• Field of Search: 333/4, 333/24.R, 333/260, 333/12, 333/1, 439/68-70
• US Class Current: 333/4
• CPC Class Codes: H03H 7/383 comprising distributed impedance elements together with lumped impedance elements

Abstract

In an interconnection system including a cable and connectors, compensation is provided for stray reactances found in the connector elements. The connector elements may be RJ-style connector plug and jack pairs, which exhibit characteristic capacitive and inductive properties. The compensation is capacitive and/or inductive elements formed in the cable, components of the connectors, or an external printed wiring board. A double π-network is the preferred circuit topology for the compensated system.

Claims

1. In an interconnect system including a communications cable of balanced pairs of conductors, a plug and a jack, wherein one or more of the cable, the plug and the jack include a stray reactance, apparatus comprising:

a compensating reactance configured as π

-network connected in one conductor of a first pair of conductors built into another one or more of the cable, the plug and the jack;

wherein the compensating reactance corrects for both near end cross-talk and far end cross-talk.

2. The apparatus of claim 1, wherein the π

-network includes components having values which when combined with the stray reactances form a symmetrically arranged network comprising;

a central capacitor having a value 2C and having one side connected to a first conductor of a second pair of conductors;

a pair of inductors, one of the pair of inductors being a stray inductor inherent in the interconnect system, each having a value L and connected in series with each other at a central node and each also having an end node, the central capacitor having another side connected to the central node; and

a pair of end capacitors, one of the pair of end capacitors being a stray capacitor inherent in the interconnect system, each having a value C and connected from the end node of each of the pair of inductors a second conductor of the second pair of conductors.

3. The apparatus of claim 2, further comprising a second symmetrical network arranged to form a balanced circuit.

4. The apparatus of claim 3, wherein the jack is mounted on a printed wiring board, the printed wiring board further comprising:

a first inductive printed wiring trace in one layer of the printed wiring board.

5. The apparatus of claim 4, further comprising:

a second inductive printed wiring trace in another layer of the printed wiring board, the second printed wiring trace forming a mutual inductance with the first inductive printed wiring trace.

6. The apparatus of claim 5, wherein the cable includes balanced pairs of wires a-b and c-d, wherein a stray mutual inductance exists between wires a and c, and the mutual inductance formed by the first and second inductive printed wiring traces is between wires a and d.

7. The apparatus of claim 6, wherein the second inductive trace forms a π

-network which includes components having values which when combined with the stray reactances form a symmetrically arranged network comprising;

a central capacitor having a value 2C and having one side connected to the second conductor of the second pair of conductors;

a pair of inductors, one of the pair of inductors being a stray inductor inherent in the interconnect system, each having a value L and connected in series with each other at a central node and each also having an end node, the central capacitor having another side connected to the central node; and

a pair of end capacitors, one of the pair of end capacitors being a stray capacitor inherent in the interconnect system, each having a value C and connected from the end node of each of the pair of inductors to the first conductor of the second pair of conductors.

8. The apparatus of claim 2, including a lead frame structure built into the jack, the lead frame comprising:

a first pair of signal conductors defining the central capacitor;

a signal conductor defining one of the pair of inductors; and

a second pair of signal conductors defining one of the pair of end capacitors.

9. The apparatus of claim 8, further comprising a second symmetrical network arranged to form a balanced circuit.

10. The apparatus of claim 1 wherein the cable includes balanced pairs of wires a-b and c-d, wherein a stray capacitance exists between wires a and c, and the compensating reactance is formed by a twist formed in a portion of the cable within the plug.

11. The apparatus of claim 10, wherein the twist introduces a compensating capacitance.

12. The apparatus of claim 11, wherein the twist introduces a compensating inductance.

13. The apparatus of claim 12, wherein the twist is between wires a and d.

14. The apparatus of claim 10, wherein a stray capacitance exists between wires b and d, and the compensating reactance is formed by a twist in a portion of the cable within the plug.

15. The apparatus of claim 14, wherein the twist introduces a compensating capacitance.

16. The apparatus of claim 15, wherein the twist introduces a compensating inductance.

17. The apparatus of claim 16, wherein the twist is between wires b and c.

18. In an interconnect system including a communications cable of balanced pairs of conductors, a plug and a jack, wherein one or more of the cable, the plug and the jack include a stray reactance, apparatus comprising:

a compensating reactance built into another one or more of the cable, the plug and the jack; and

a printed wiring board on which the jack is mounted, the printed wiring board including a first inductive printed wiring trace in one layer of the printed wiring board;

wherein the compensating reactance further comprises π

-network connected in one conductor of a first pair of conductors; and

wherein the compensating reactance corrects for both near end cross-talk and far end cross-talk.

19. The apparatus of claim 18, wherein the π

-network includes components having values which when combined with the stray reactances form a symmetrically arranged network comprising;

a central capacitor having a value 2C and having one side connected to a first conductor of a second pair of conductors;

a pair of inductors, one of the pair of inductors being a stray inductor inherent in the interconnect system, each having a value L and connected in series with each other at a central node and each also having an end node, the central capacitor having another side connected to the central node; and

a pair of end capacitors, one of the pair of end capacitors being a stray capacitor inherent in the interconnect system, each having a value C and connected from the end node of each of the pair of inductors to a second conductor of the second pair of conductors.

20. The apparatus of claim 19, further comprising:

a second inductive printed wiring trace in another layer of the printed wiring board, the second printed wiring trace forming a mutual inductance with the first inductive printed wiring trace.

21. The apparatus of claim 20, wherein the cable includes balanced pairs of wires a-b and c-d, wherein a stray mutual inductance exists between wires a and c, and the mutual inductance formed by the first and second inductive printed wiring traces is between wires a and d.

22. The apparatus of claim 21, wherein the second inductive trace forms a π

-network which includes components having values which when combined with the stray reactances form a symmetrically arranged network comprising;

a central capacitor having a value 2C and having one side connected to the second conductor of the second pair of conductors;

a pair of inductors, one of the pair of inductors being a stray inductor inherent in the interconnect system, each having a value L and connected in series with each other at a central node and each also having an end node, the central capacitor having another side connected to the central node; and

a pair of end capacitors, one of the pair of end capacitors being a stray capacitor inherent in the interconnect system, each having a value C and connected from the end node of each of the pair of inductors to the first conductor of the second pair of conductors.

23. The apparatus of claim 18, wherein the cable comprises balanced pairs of conductors a-b and c-d, wherein a stray capacitance exists between conductors a and c, and the compensating reactance comprises a twist formed in a portion of the cable within the plug.

24. In an interconnect system including a communications cable of balanced pairs of conductors, a plug and a jack, wherein one or more of the cable, the plug and the jack include a stray reactance, apparatus comprising:

a compensating reactance built into another one or more of the cable, the plug and the jack;

wherein the apparatus includes balanced pairs of conductors a-b and c-d and the plug introduces a stray capacitance between conductors a and c having a value C and the jack introduces a stray mutual inductance between conductors a and c having a value L and the compensation reactance comprises;

a capacitor having a value 2C connected from conductor b to conductor c;

a mutual inductor having a value L linking conductors a and c with a polarity opposite that of the stray mutual inductance; and

a capacitor having a value C connected from conductor a to conductor c.

25. The apparatus of claim 24, including a lead frame structure built into the jack, the lead frame comprising:

a first pair of signal conductors defining the capacitor of value 2C;

a second pair of signal conductors defining the mutual inductor of value L; and

a third pair of signal conductors defining the capacitor of value C.

26. The apparatus of claim 24, wherein

the capacitor connected from conductor b to conductor c is formed by a twist in conductors b and c;

and

the inductor linking conductors a and c and the capacitor connected between conductor a and conductor c are formed by a twist in conductors a and c.

27. In an interconnect system including a communications cable of balanced pairs of conductors, a plug and a jack, wherein one or more of the cable, the plug and the jack include a stray reactance, apparatus comprising:

a compensating reactance built into another one or more of the cable, the plug and the jack;

further comprising a multi layer lead frame structure whose signal conductors comprise compensating capacitive and inductive structures.

28. The apparatus of claim 27, wherein the capacitive structures comprise:

a first signal conductor; and

a second signal conductor;

the first and second signal conductors juxtaposed in space to exhibit a substantially capacitive reactance.

29. The apparatus of claim 28, wherein the inductive structures comprise a first signal conductor exhibiting a substantially inductive reactance.

30. The apparatus of claim 29, wherein the inductive structures further comprise a second signal conductor juxtaposed in space with the first signal conductor so the first and second signal conductors exhibit a mutual inductance therebetween.

31. The apparatus of claim 30, further comprising a second symmetrical network arranged to form a balanced circuit.