Communications jacks having conductive paths with the same current direction that inductively and capacitively couple
Communications jacks include a housing having a plug aperture that is configured to receive a mating RJ-45 plug along a longitudinal axis and eight jackwire contacts that are arranged as four differential pairs of jackwire contacts, each of the jackwire contacts including a plug contact region that extends into the plug aperture. A first of the jackwire contacts is configured to engage a longitudinally extending surface of a first blade of a mating RJ-45 plug when the mating RJ-45 plug is fully received within the plug aperture.
1. A communications jack, comprising:
a first conductive path electrically connecting a first input of the jack and a first output of the jack;
a second conductive path electrically connecting a second input of the jack and a second output of the jack, wherein the first and second conductive paths comprise a first differential pair of conductive paths for transmitting a first information signal;
a third conductive path electrically connecting a third input of the jack and a third output of the jack;
a fourth conductive path electrically connecting a fourth input of the jack and a fourth output of the jack, wherein the third and fourth conductive paths comprise a second differential pair of conductive paths for transmitting a second information signal; and
a return loss improvement circuit that comprises a first section of the first conductive path and a second section of the second conductive path that has the same instantaneous current direction as the first section of the first conductive path, wherein the first section and the second section are positioned to both capacitively and inductively couple with each other.
2. The communications jack of claim 1 , wherein the amount of capacitive coupling exceeds the amount of inductive coupling.
3. The communications jack of claim 1 , wherein the amount of capacitive coupling is at least half the amount of the inductive coupling.
4. The communications jack of claim 1 , further comprising a flexible printed circuit board, wherein the first section of the first conductive path is on a first side of the flexible printed circuit board and the second section of the second conductive path is on a second side of the flexible printed circuit board that is opposite the first side.
5. The communications jack of claim 1 , wherein the ratio of the capacitive coupling to the inductive coupling in the return loss improvement circuit is selected to provide a local maximum in a return loss spectrum.
6. The communications jack of claim 1 , wherein the return loss improvement circuit comprises a first return loss improvement circuit, the jack further comprising a second return loss improvement circuit that comprises a third section of the third conductive path and a fourth section of the fourth conductive path that has the same instantaneous current direction as the third section of the third conductive path, wherein the third section and the fourth section are positioned to both capacitively and inductively couple with each other.
7. A method of controlling the return loss on a differential transmission line that includes a first conductive path and a second conductive path of an RJ-45 communications connector, the method comprising:
routing a first section of the first conductive path and a first section of the second conductive path so that the first and second sections have substantially the same instantaneous current direction and so that the first and second sections both capacitively and inductively couple with one another;
controlling the amount of capacitive coupling between the first section and the second section and the amount of inductive coupling between the first section and the second section to improve the return loss of the transmission line.
8. The method of claim 7 , wherein controlling the amount of capacitive coupling between the first section and the second section and the amount of inductive coupling between the first section and the second section to improve the return loss of the transmission line comprises selecting the amount of capacitive coupling between the first section and the second section and the amount of inductive coupling between the first section and the second section to create a resonance that creates a local maximum in the return loss spectrum within twice the operating frequency range of the communications jack.
9. The method of claim 7 , wherein the first section is on a first side of a flexible printed circuit board and the second section is on a second side of the flexible printed circuit board that is opposite the first side.
10. The method of claim 9 , wherein the first section and the second section at least partially overlap.
11. The method of claim 9 , wherein the first section comprises a widened conductive trace that both inductively and capacitively couples through the flexible printed circuit board with a conductive trace that forms the second section.
12. The method of claim 9 , wherein controlling the amount of capacitive coupling between the first section and the second section and the amount of inductive coupling between the first section and the second section to improve the return loss of the transmission line comprises selecting widths for first and second conductive traces that are used to form the first and second sections and/or selecting a degree to which the first and second conductive traces overlap and/or a length of the overlapping sections of the first and second conductive traces.
13. A communications jack, comprising:
a housing having a plug aperture;
a flexible printed circuit board that is at least partly mounted within the housing;
a first conductive path electrically connecting a first input of the jack and a first output of the jack;
a second conductive path electrically connecting a second input of the jack and a second output of the jack, wherein the first and second conductive paths comprise a first differential pair of conductive paths;
wherein the first conductive path includes first and second conductive trace sections on the flexible printed circuit board that are immediately adjacent to each other and that have generally the same instantaneous current direction such that the first and second conductive trace sections self-couple and cause a localized increase in inductance, and
wherein the first conductive trace section is on a first side of the flexible printed circuit board and the second conductive trace section is on a second side of the flexible printed circuit board that is opposite the first side, and
wherein the first and second conductive trace sections are configured to both inductively and capacitively couple into each other.
14. The communications jack of claim 13 , wherein at least one of the conductive trace sections comprises a spiral.
15. The communications jack of claim 13 , wherein the first conductive trace section at least partially overlaps the second conductive trace section.
16. The communications jack of claim 13 , wherein an amount of capacitive coupling between the first conductive trace section and the second conductive trace section is at least half an amount of inductive coupling between the first conductive trace section and the second conductive trace section.