Communications plugs and patch cords with mode conversion control circuitry
Patch cords include a communications cable that has first through eighth conductors that are arranged as four twisted pairs and a plug attached thereto. The plug includes a housing that receives the cable, first through eighth plug contacts, and a printed circuit board that includes first through eighth conductive paths that connect the first through eighth conductors to the respective first through eighth plug contacts. The plug further includes a first crosstalk injection circuit between the second conductive path and the sixth conductive path and a second crosstalk injection circuit between the first conductive path and the sixth conductive path.
1. An RJ-45 communications plug that has first through eighth conductive paths where the fourth and fifth conductive paths are part of a first differential transmission line, the first and second conductive paths are part of a second differential transmission line, the third and sixth conductive paths are part of a third differential transmission line, and the seventh and eighth conductive paths are part of a fourth differential transmission line, the plug comprising:
a housing;
first through eighth plug blades that are at least partially within the housing and that are electrically connected to the respective first through eighth conductive paths, the first through eighth plug blades aligned in a row in numerical order;
a differential-to-common mode crosstalk cancellation circuit that substantially cancels common mode crosstalk that is injected within the plug from the third differential transmission line onto the second differential transmission line when the third differential transmission line is excited differentially,
wherein the third differential transmission line is configured to inject differential crosstalk onto the second differential transmission line when the third differential transmission line is excited differentially.
2. The RJ-45 communications plug of claim 1 , wherein the plug is configured so that a magnitude of the differential-to-differential crosstalk injected from the third transmission line onto the second differential transmission line when the third differential transmission line is excited by a differential signal having a first frequency is set to fall within a pre-selected range below a magnitude of the differential signal.
3. The RJ-45 communications plug of claim 2 , wherein the pre-selected range is between 46.5 dB and 49.5 dB for a first frequency of 100 MHz.
4. The RJ-45 communications plug of claim 1 , wherein the differential-to-common mode crosstalk cancellation circuit includes a first reactive circuit between the second conductive path and the sixth conductive path, and a second reactive circuit between the first conductive path and the sixth conductive path.
5. The RJ-45 communications plug of claim 4 , wherein the first reactive circuit comprises a first capacitor on a printed circuit board and the second reactive circuit comprises a second capacitor on the printed circuit board.
6. The RJ-45 communications plug of claim 5 , wherein the first capacitor connects to the second conductive path directly adjacent to a signal injection location on the second plug blade, and connects to the sixth conductive path directly adjacent to a signal injection location the sixth plug blade.
7. The RJ-45 communications plug of claim 4 , wherein the first reactive circuit comprises a first inductive coupling section on a printed circuit board between the second conductive path and the sixth conductive path, and the second reactive circuit comprises a second inductive coupling section on the printed circuit board between the first conductive path and the sixth conductive path.
8. The RJ-45 communications plug of claim 4 , wherein the differential-to-common mode crosstalk cancellation circuit includes a third reactive circuit between the second conductive path and the third conductive path.
9. The RJ-45 communications plug of claim 8 , wherein differential-to-differential crosstalk injected onto the second transmission line by the third differential transmission line when the third differential transmission line is excited differentially is greater than twice amount of coupling between the second plug blade and the third plug blade minus twice the amount of coupling between the first plug blade and the third plug blade.
10. The RJ-45 communications plug of claim 4 , wherein the differential-to-common mode crosstalk cancellation circuit includes a third reactive circuit between the first conductive path and the third conductive path.
11. The RJ-45 communications plug of claim 10 , wherein differential-to-differential crosstalk injected onto the second transmission line by the third differential transmission line when the third differential transmission line is excited differentially is less than twice amount of coupling between the second plug blade and the third plug blade minus twice the amount of coupling between the first plug blade and the third plug blade.
12. The RJ-45 communications plug of claim 1 , wherein the differential-to-common mode crosstalk cancellation circuit also substantially cancels common mode crosstalk that is injected within the plug from the second differential transmission line onto the third differential transmission line when the second differential transmission line is excited differentially.
13. The RJ-45 communications plug of claim 1 , further comprising a communications cable that has first through eighth conductors that are electrically connected to the respective first through eighth conductive paths to provide a patch cord.