Printed circuit boards for communications connectors having openings that improve return loss and/or insertion loss performance and related connectors and methods
Printed circuit boards for communications connectors are provided that include a dielectric substrate formed of a first insulative material having a first dielectric constant. First and second pairs of input terminals and first and second pairs of output terminals are provided on the dielectric substrate. A first differential transmission line electrically connect the first pair of input terminals to the first pair of output terminals, and a second differential transmission line electrically connect the second pair of input terminals to the second pair of output terminals. The dielectric substrate includes an opening that is positioned between the conductive paths of the first differential transmission line, the opening containing a second insulative material having a second dielectric constant.
1. A printed circuit board for a communications connector, comprising:
a dielectric substrate formed of a first insulative material having a first dielectric constant;
a first pair of input terminals on the dielectric substrate;
a first pair of output terminals on the dielectric substrate;
a first pair of conductive paths on the dielectric substrate that are arranged as a first differential transmission line that electrically connect the first pair of input terminals to the first pair of output terminals;
a second pair of input terminals on the dielectric substrate;
a second pair of output terminals on the dielectric substrate; and
a second pair of conductive paths on the dielectric substrate that are arranged as a second differential transmission line that electrically connect the second pair of input terminals to the second pair of output terminals,
wherein the dielectric substrate includes an opening that is positioned between the conductive paths of the first pair of conductive paths, the opening containing a second insulative material having a second dielectric constant that is different than the first dielectric constant.
2. The printed circuit board of claim 1 , wherein the opening is at least partially filled with a material having a second dielectric constant that is higher than the first dielectric constant, wherein the printed circuit board further includes a crosstalk circuit that injects crosstalk onto a first section of a first conductive path of the first differential transmission line, and wherein the opening is positioned immediately adjacent the first section of the first conductive path, and wherein the crosstalk circuit increases the impedance of the first section of the first differential transmission line to less than a pre-selected value, and wherein the opening with the material having the second dielectric constant decreases the impedance of the first section of the first differential transmission line to be closer to the pre-selected value without materially changing the amount of crosstalk injected by the crosstalk circuit.
3. The printed circuit board of claim 1 , wherein the second dielectric constant is lower than the first dielectric constant.
4. The printed circuit board of claim 3 , wherein the opening comprises an air-filled opening that extends from a top surface of the dielectric substrate to a bottom surface of the dielectric substrate.
5. The printed circuit board of claim 3 , wherein the dielectric substrate comprises a multi-layer dielectric substrate having at least a first dielectric layer and a second dielectric layer, the printed circuit board further comprising a conductive image plane between the first dielectric layer and the second dielectric layer.
6. The printed circuit board of claim 3 , wherein the opening is positioned between the conductive paths of the second pair of conductive paths.
7. The printed circuit board of claim 3 , further comprising:
a third pair of input terminals on the dielectric substrate;
a third pair of output terminals on the dielectric substrate;
a third pair of conductive paths on the dielectric substrate that are arranged as a third differential transmission line that electrically connect the third pair of input terminals to the third pair of output terminals;
a fourth pair of input terminals on the dielectric substrate;
a fourth pair of output terminals on the dielectric substrate; and
a fourth pair of conductive paths on the dielectric substrate that are arranged as a fourth differential transmission line that electrically connect the fourth pair of input terminals to the fourth pair of output terminals,
the printed circuit board in combination with four pairs of input contacts that are electrically connected to the first through fourth pair of input terminals, respectively, four pairs of output contacts that are electrically connected to the first through fourth pair of output terminals, respectively, and a housing that at least partially encloses the printed circuit board to provide an RJ-45 communications connector.
8. The printed circuit board of claim 7 , wherein contact portions of the four pairs of input contacts are arranged in a row, and wherein the contact portions of the first pair of input contacts are between contact portions of the second pair of input contacts.
9. The printed circuit board of claim 4 , wherein the printed circuit board further includes a crosstalk circuit that injects crosstalk onto a first section of a first conductive path of the first differential transmission line, and wherein the air-filled opening is positioned immediately adjacent the first section of the first conductive path.
10. The printed circuit board of claim 9 , wherein the crosstalk circuit comprises an inductive crosstalk circuit.
11. The printed circuit board of claim 9 , wherein the crosstalk circuit reduces the impedance of the first section of the first differential transmission line to less than a pre-selected value, and wherein the air-filled opening increases the impedance of the first section of the first differential transmission line to be closer to the pre-selected value without materially changing the amount of crosstalk injected by the crosstalk circuit.
12. A communications connector, comprising:
a housing;
a printed circuit board that is mounted at least partly within the housing, the printed circuit board including a planar dielectric substrate, a plurality of pairs of input terminals, a plurality of pairs of output terminals, and a plurality of differential transmission lines that each connect a respective one of the pairs of input terminals to a respective one of the pairs of output terminals;
a plurality of pairs of input contacts that are electrically connected to respective ones of the pairs of input terminals;
a plurality of pairs of output contacts that are electrically connected to respective ones of the pairs of output terminals;
wherein the planar dielectric substrate includes an air-filled opening that is positioned to increase the impedance of at least one of the plurality of differential transmission lines.
13. The communications connector of claim 12 , wherein the air-filled opening comprises an opening that extends from a top face of the printed circuit board to a bottom face of the printed circuit board.
14. The communications connector of claim 12 , wherein the communications connector comprises an RJ-45 plug and wherein the RJ-45 plug is connected to a communications cable to provide a patch cord.
15. The communications connector of claim 12 , wherein the size, shape and/or depth of the opening is configured to increase the impedance of the first differential transmission line to be above a pre-selected value.
16. The communications connector of claim 12 , wherein the air-filled opening is positioned between a first conductive path and a second conductive path of a first of the differential transmission lines.
17. The communications connector of claim 16 , wherein the air-filled opening is positioned between a first conductive path and a second conductive path of a second of the differential transmission lines.
18. The communications connector of claim 16 , wherein the printed circuit board further includes a crosstalk circuit that injects crosstalk onto a first section of a first conductive path of the first differential transmission line, and wherein the air-filled opening is positioned immediately adjacent the first section of the first conductive path.
19. The communications connector of claim 18 , wherein the crosstalk circuit comprises an inductive crosstalk circuit.
20. A method of manufacturing a printed circuit board for a communications connector, the method comprising:
forming a plurality of input terminals, a plurality of output terminals and a plurality of conductive paths on a planar dielectric substrate that is formed of a first material having a first dielectric constant, where each of the conductive paths electrically connects a respective one of the input terminals to a respective one of the output terminals, the conductive paths arranged in pairs to form a plurality of differential transmission lines, wherein the planar dielectric substrate is formed to have an opening that is at least partly filled with a second dielectric material that has a second dielectric constant that is less than the first dielectric constant, wherein the opening in the planar dielectric substrate is positioned between the conductive paths of a first of the differential transmission lines, wherein the size of the opening and/or the second dielectric constant is selected to increase an impedance of the first of the differential transmission lines in the vicinity of the opening.
21. The method of claim 20 , wherein the impedance of the first of the differential transmission lines in the vicinity of the opening is closer to a pre-selected value than it would be if the opening were filled with the first material.