Patent Application
20170104295
The present invention relates generally to communications connectors and, more particularly, to communications plugs such as RJ-45 plugs that may exhibit improved crosstalk performance when mated with a communications jack to form a mated plug jack connection.
Many hardwired communications systems use plug and jack connectors to connect a communications cable to another communications cable or to computer equipment. By way of example, high speed communications systems routinely use such plug and jack connectors to connect computers, printers and other devices to local area networks and/or to external networks such as the Internet.
As shown in
When a signal is transmitted over a conductor (e.g., an insulated copper wire) in a communications cable, electrical noise from external sources may be picked up by the conductor, degrading the quality of the signal. In order to counteract such noise sources, the information signals in the above-described communications systems are typically transmitted between devices over a pair of conductors (hereinafter a “differential pair” or simply a “pair”) rather than over a single conductor. The two conductors of each differential pair are twisted tightly together in the communications cables and patch cords so that the eight conductors are arranged as four twisted differential pairs of conductors. The signals transmitted on each conductor of a differential pair have equal magnitudes, but opposite phases, and the information signal is embedded as the voltage difference between the signals carried on the two conductors of the pair. When the signal is transmitted over a twisted differential pair of conductors, each conductor in the differential pair often picks up approximately the same amount of noise from these external sources. Because the information signal is extracted by taking the difference of the signals carried on the two conductors of the differential pair, the subtraction process may mostly cancel out the noise signal, and hence the information signal is typically not disturbed.
Referring again to
In particular, “crosstalk” refers to unwanted signal energy that is capacitively and/or inductively coupled onto the conductors of a first “victim” differential pair from a signal that is transmitted over a second “disturbing” differential pair. The induced crosstalk may include both near-end crosstalk (NEXT), which is the crosstalk measured at an input location corresponding to a source at the same location (i.e., crosstalk whose induced voltage signal travels in an opposite direction to that of an originating, disturbing signal in a different path), and far-end crosstalk (FEXT), which is the crosstalk measured at the output location corresponding to a source at the input location (i.e., crosstalk whose signal travels in the same direction as the disturbing signal in the different path). Both types of crosstalk comprise an undesirable noise signal that interferes with the information signal that is transmitted over the victim differential pair.
While methods are available that can significantly reduce the effects of crosstalk within communications cable segments, the communications connector configurations that were adopted years ago—and which still are in effect in order to maintain backwards compatibility—generally did not arrange the contact structures so as to minimize crosstalk between the differential pairs in the connector hardware. For example, pursuant to the ANSI/TIA-568-C.2 standard approved Aug. 11, 2009 by the Telecommunications Industry Association, in the connection region where the contacts of a modular plug mate with the contacts of the modular jack (referred to herein as the “plug-jack mating region”), the eight contacts 1-8 of the jack must be aligned in a row, with the eight contacts 1-8 arranged as four differential pairs specified as depicted in
As hardwired communications systems have moved to higher frequencies in order to support increased data rate communications, crosstalk in the plug and jack connectors has became a more significant problem. To address this problem, communications jacks now routinely include crosstalk compensation circuits that introduce “compensating” crosstalk that is used to cancel much of the “offending” crosstalk that is introduced in the plug jack mating region as a result of the industry-standardized connector configurations. In order to ensure that plugs and jacks manufactured by different vendors will work well together, the industry standards specify amounts of offending crosstalk that must be generated between the various differential pair combinations in an RJ-45 plug for that plug to be industry-standards compliant. Thus, while it is now possible to manufacture RJ-45 plugs that exhibit much lower levels of offending crosstalk, it is still necessary to ensure that RJ-45 plugs inject the industry-standardized amounts of offending crosstalk between the differential pairs so that backwards compatibility will be maintained with the installed base of RJ-45 plugs and jacks. Typically, so-called “multi-stage” crosstalk compensation circuits are used. Such crosstalk circuits are described in U.S. Pat. No. 5,997,358 to Adriaenssens et al., the entire content of which is hereby incorporated herein by reference as if set forth fully herein.
Crosstalk can be classified as either differential crosstalk or as common mode crosstalk. Differential crosstalk refers to a crosstalk signal that appears as a difference in voltage between two conductors of a victim differential pair. This type of crosstalk degrades any information signal carried on the victim differential pair as the difference in voltage does not subtract out when the information signal carried on the victim differential pair is extracted by taking the difference of the voltages carried by the conductors on the victim differential pair. Common mode crosstalk refers to a crosstalk signal that appears on both conductors of a differential pair. Common mode crosstalk typically does not disturb the information signal on the victim differential pair, as the disturbing common mode signal is cancelled by the subtraction process used to recover the information signal on the victim differential pair.
Common mode crosstalk, however, can generate another type of crosstalk called “alien” crosstalk. Alien crosstalk refers to crosstalk that occurs between two communication channels. Alien crosstalk can arise, for example, in closely spaced connectors (e.g., patch panels) or in communications cables that are bundled together. For example, a differential pair in a first communications cable can crosstalk with a differential pair in a second, immediately adjacent communications cable. Common mode signals that may be carried on a differential pair are particularly likely to generate alien crosstalk, as common mode signals are generally not self-cancelling in the way that differential signals are. Obviously, physical separation between connectors and cables may be used to reduce alien crosstalk. However, this is typically impractical because bundling of cables and patch cords and locating communications connectors in close proximity on patch panels is common practice due to “real estate” constraints and/or ease of wire management.
Pursuant to embodiments of the present invention, patch cords are provided that include a communications cable that has first through eighth conductors. The fourth and fifth conductors are twisted together to form a first twisted pair, the first and second conductors are twisted together to form a second twisted pair, the third and sixth conductors are twisted together to form a third twisted pair, and the seventh and eighth conductors are twisted together to form a fourth twisted pair. A plug is attached to the communications cable. This plug includes a housing that receives the communications cable and first through eighth plug contacts that include plug contact regions that are substantially aligned in a row in numerical order. The plug further includes a printed circuit board that has first through eighth conductive paths that connect the first through eighth conductors to the respective first through eighth plug contacts. A first portion of the first conductive path and a first portion of the second conductive path are routed as a transmission line, and a first portion of the sixth conductive path is routed therebetween.
In some embodiments, the first portion of the first conductive path, the first portion of the second conductive path and the first portion of the sixth conductive path are all on the same side of the printed circuit board. In other embodiments, the first portion of the first conductive path and the first portion of the second conductive path are on a first layer of the printed circuit board, and the first portion of the sixth conductive path is on a second layer of the printed circuit board that is different than the first layer. A first portion of the seventh conductive path and a first portion of the eighth conductive path may also be routed in side-by-side fashion as a transmission line, and a first portion of the third conductive path may be routed therebetween. The third and sixth conductive paths may cross over each other at least twice and/or may form an expanded loop on the printed circuit board.
In some embodiments, the first portion of the sixth conductive path may be configured to couple substantially equal amounts of energy onto the first portions of the first and second conductive paths when a signal is incident on the sixth conductive path. The first portion of the sixth conductive path that is routed between the first portions of the first and second conductive paths may comprise a differential-to-common mode crosstalk cancellation circuit that at least partially cancels the common mode crosstalk that is injected from the third plug contact onto the first and second plug contacts. At least a portion of the differential-to-common mode crosstalk cancellation circuit may be located on a front half of the printed circuit board that receives the first through eighth plug blades.
Pursuant to further embodiments of the present invention, patch cords are provided that include a communications cable that has first through eighth conductors. The fourth and fifth conductors are twisted together to form a first twisted pair, the first and second conductors are twisted together to form a second twisted pair, the third and sixth conductors are twisted together to form a third twisted pair, and the seventh and eighth conductors are twisted together to form a fourth twisted pair. A plug is attached to the communications cable. This plug includes a housing that receives the communications cable and first through eighth plug contacts that include plug contact regions that are substantially aligned in a row in numerical order. The plug further includes a printed circuit board that has first through eighth conductive paths that connect the first through eighth conductors to the respective first through eighth plug contacts. On the printed circuit board, a first portion of the second conductive path is closer to the seventh and eight conductive paths than is a first portion of the sixth conductive path, and a first portion of the seventh conductive path is closer to the first and second conductive paths than is a first portion of the third conductive path.
In some embodiments, the first portion of the sixth conductive path is routed between substantially parallel first portions of the first and second conductive paths. The first portion of the sixth conductive path may be substantially equidistant from the first portions of the first and second conductive paths. The first portion of the sixth conductive path may be configured to couple substantially equal amounts of energy onto the first portions of the first and second conductive paths. The first portions of the first and second conductive paths may be routed generally side-by-side as a differential transmission line, and the first portion of the sixth conductive path may be routed between the first portions of the first and second conductive paths.
Pursuant to still further embodiments of the present invention, patch cords are provided that include a communications cable that has first through fourth conductors. The first and second conductors form a first differential pair, and the third and fourth conductors form a second differential pair. A plug is attached to the communications cable. This plug includes a housing that receives the communications cable and first through fourth plug contacts. The plug further includes a printed circuit board that has first through fourth conductive paths that connect the first through fourth conductors to the respective first through fourth plug contacts. The third plug contact injects common mode crosstalk onto the first and second plug contacts, and the fourth conductive path includes a section that couples with the first and second conductive paths to at least partially cancel this common mode crosstalk.
In some embodiments, the first through fourth plug contacts include plug contact regions that are substantially aligned in a row in numerical order, and/or the third and fourth conductive paths form an expanded loop on the printed circuit board. First portions of the first and second conductive paths may be routed in side-by-side fashion as a transmission line, and a first portion of the fourth conductive path may be routed therebetween. The first portions of the first, second and fourth conductive paths may all be on the same side of the printed circuit board. The third and fourth conductive paths may cross over each other at least twice. The first portion of the fourth conductive path may be configured to couple substantially equal amounts of energy onto the first portions of the first and second conductive paths.
Pursuant to still further embodiments of the present invention, patch cords are provided that include a communications cable that has first through eighth conductors, where the fourth and fifth conductors are twisted together to form a first twisted pair, the first and second conductors are twisted together to form a second twisted pair, the third and sixth conductors are twisted together to form a third twisted pair, and the seventh and eighth conductors are twisted together to form a fourth twisted pair. A plug is attached to the communications cable. The plug has a housing that receives the communications cable, first through eighth plug contacts that include plug contact regions that are substantially aligned in a row in numerical order, and a printed circuit board that is at least partly within the housing. The printed circuit board includes first through eighth conductive paths that connect the first through eighth conductors to the respective first through eighth plug contacts. A first portion of the sixth conductive path is routed so that, when excited by a signal, it will couple substantially equal amounts of signal energy onto a first portion of the first conductive path and a first portion of the second conductive path.
In some embodiments, the first portion of the sixth conductive path includes a first current carrying path that is positioned adjacent the first portion of the first conductive path and a second current carrying path that is positioned adjacent the first portion of the second conductive path. In such embodiments, the first portion of the first conductive path, the first portion of the second conductive path and the first portion of the sixth conductive path may all be on the same layer of the printed circuit board. In some embodiments, the first portion of the first conductive path and the first portion of the second conductive path may be between the first current carrying path of the first portion of the sixth conductive path and the second current carrying path of the first portion of the sixth conductive path. In other embodiments, the first current carrying path of the first portion of the sixth conductive path may be vertically stacked with the first portion of the first conductive path and the second current carrying path of the first portion of the sixth conductive path may be vertically stacked with the first portion of the second conductive path
In some embodiments, the first portion of the first conductive path and the first portion of the second conductive path may be on a first layer of the printed circuit board, and the first portion of the sixth conductive path may be a widened trace that is on a second layer of the printed circuit board that is different than the first layer. In some embodiments, the first portion of the sixth conductive path may overlap the first portion of the first conductive path and the first portion of the second conductive path. The printed circuit board may be a flexible printed circuit board. The first portion of the sixth conductive path may be routed between the first portion of the first conductive path and the first portion of the second conductive path.
Pursuant to additional embodiments of the present invention, patch cords are provided that include a communications cable that has first through eighth conductors. The fourth and fifth conductors are twisted together to form a first twisted pair, the first and second conductors are twisted together to form a second twisted pair, the third and sixth conductors are twisted together to form a third twisted pair, and the seventh and eighth conductors are twisted together to form a fourth twisted pair. A plug is attached to the communications cable. This plug includes a housing that receives the communications cable and first through eighth plug contacts. The plug further includes a printed circuit board that has first through eighth conductive paths that connect the first through eighth conductors to the respective first through eighth plug contacts. A first crosstalk injection circuit is provided between the second conductive path and the sixth conductive path, and a second crosstalk injection circuit is provided between the first conductive path and the sixth conductive path.
In some embodiments, the first and second crosstalk injection circuits substantially cancel the common mode crosstalk injected from the third twisted pair onto the second twisted pair when the third twisted pair is excited differentially. The plug may also include a third crosstalk injection circuit between the second conductive path and the third conductive path. In such embodiments, the first, second and third crosstalk injection circuits may substantially cancel the common mode crosstalk injected from the third twisted pair onto the second twisted pair when the third twisted pair is excited differentially. In other embodiments, the plug includes a third crosstalk injection circuit that is provided between the first conductive path and the third conductive path.
In some embodiments, the first crosstalk injection circuit comprises a first capacitor on the printed circuit board between the second conductive path and the sixth conductive path. Likewise, the second crosstalk injection circuit may be a second capacitor on the printed circuit board between the first conductive path and the sixth conductive path. The first capacitor may connect to the second conductive path directly adjacent the second plug contact and may connect to the sixth conductive path directly adjacent the sixth plug contact.
Pursuant to yet additional embodiments of the present invention, RJ-45 communications plugs are provided that have 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 plugs further have first through eighth plug blades that are electrically connected to the respective first through eighth conductive paths, where the first through eighth plug blades aligned in a row in numerical order. A differential-to-common mode crosstalk cancellation circuit is provided 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. Additionally, 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.
In some embodiments, the amount of 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 may be an industry standards specified amount of offending crosstalk. The differential-to-common mode crosstalk cancellation, circuit may comprise 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. The first reactive circuit may be a first capacitor on a printed circuit board and the second reactive circuit may be a second capacitor on the printed circuit board. In other embodiments, the first reactive circuit may be 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 may be a second inductive coupling section on the printed circuit board between the first conductive path and the sixth conductive path.
In some embodiments, the differential-to-common mode crosstalk cancellation circuit includes a third reactive circuit between the second conductive path and the third conductive path. The 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. In other embodiments, the differential-to-common mode crosstalk cancellation circuit includes a third reactive circuit between the first conductive path and the third conductive path. In these embodiments, the differential crosstalk injected onto the second transmission line by the third differential transmission line when the third differential transmission line is excited differentially may be 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. The differential-to-common mode crosstalk cancellation circuit may substantially cancel the 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.
Pursuant to even further embodiments of the present invention, RJ-45 communications plugs are provided that have 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 first, third, fifth and seventh conductive paths are tip conductive paths and the second, fourth, sixth and eighth conductive paths are ring conductive paths. These plugs further have first through eighth plug blades 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. An offending crosstalk circuit that is separate from the plug blades is provided that injects crosstalk between the second and third differential transmission lines, where the offending crosstalk circuit is between a ring conductive path and a tip conductive path. Additionally, a differential-to-common mode crosstalk cancellation circuit is provided that is electrically connected between the second differential transmission line and the third differential transmission line.
In some embodiments, the differential-to-common mode crosstalk cancellation circuit substantially cancels common mode crosstalk that is injected within the plug from the third differential transmission line to the second differential transmission line when the third differential transmission line is excited differentially. The differential-to-common mode crosstalk cancellation circuit may include a first reactive circuit between the second conductive path and the sixth conductive path, a second reactive circuit between the first conductive path and the sixth conductive path and a third reactive circuit between the second conductive path and the third conductive path. The first through third reactive circuits may comprise first through third capacitors on a printed circuit board.
Pursuant to further embodiments of the present invention, RJ-45 communications plugs provided that include first through eighth conductive paths that are arranged as first through fourth differential transmission lines. A capacitor and a resistor are electrically coupled in series between two of the first through eighth conductive paths.
The present invention is directed to communications plugs such as RJ-45 plugs. As used herein, the terms “forward” and “front” and derivatives thereof refer to the direction defined by a vector extending from the center of the plug toward the portion of the plug that is first received within a plug aperture of a jack when the plug is mated with a jack. Conversely, the terms “rearward” and “back” and derivatives thereof refer to the direction directly opposite the forward direction. The forward and rearward directions define the longitudinal dimension of the plug. The vectors extending from the center of the plug toward the respective sidewalls of the plug housing defines the transverse (or lateral) dimension of the plug. The transverse dimension is normal to the longitudinal dimension. The vectors extending from the center of the plug toward the respective top and bottom walls of the plug housing (where the top wall of the plug housing is the wall that includes slots that expose the plug blades) defines the vertical dimension of the plug. The vertical dimension of the plug is normal to both the longitudinal and transverse dimensions.
Pursuant to embodiments of the present invention, communications plugs, as well as patch cords that include such communications plugs, are provided that may exhibit reduced levels of differential-to-common mode crosstalk (which is also referred to as “mode conversion”). By reducing the amount of mode conversion that occurs in a communications plug, the need to compensate for such mode conversion in a mating communications jack may be reduced. Moreover, all other factors equal, it may be more efficient to reduce such common mode crosstalk in the plug rather than having to cancel it in the mating jack, since typically most offending crosstalk is generated in the plug and attempting to cancel it in mating jack is subject to the limitations imposed by the transmission delay between the offending and compensating crosstalk. The plugs according to some embodiments of the present invention may substantially cancel the differential-to-common mode crosstalk that arises between selected of the differential transmission lines in the communications plug, while still providing any industry standardized amounts of differential-to-differential crosstalk between these differential transmission lines.
In some embodiments, the communications plug may comprise an RJ-45 plug. The RJ-45 plug may have a printed circuit board that includes first through eighth conductive paths and first through eighth plug blades that are mounted on the printed circuit board and connected to the respective first through eighth conductive paths. The eight conductive paths and plug blades may be arranged as the four differential transmission lines with the conductive paths numbered pursuant to the TIA/EIA 568 type B configuration. The third and sixth conductive paths (i.e., the third differential transmission line) may form an expanded loop on the printed circuit board in order to cancel differential-to-common mode crosstalk that arises between (1) the plug blades of the second and third differential transmission lines and/or (2) the plug blades of the third and fourth differential transmission lines. This expanded loop may substantially cancel the common mode crosstalk injected by the third plug blade onto the first and second plug blades and by the fourth plug blade onto the seventh and eighth plug blades.
In some embodiments, a first portion of the first conductive path and a first portion of the second conductive path may be routed as a transmission line, and a first portion of the sixth conductive path may be routed between the first portion of the first conductive path and the first portion of the second conductive path. The first portion of the sixth conductive path may be configured to couple substantially equal amounts of energy onto the first portion of the first conductive path and the first portion of the second conductive path when a signal is incident on the sixth conductive path. A first portion of the seventh conductive path and a first portion of the eighth conductive path may similarly be routed as a transmission line, and a first portion of the third conductive path may be routed between the first portion of the seventh conductive path and the first portion of the eighth conductive path.
Pursuant to further embodiments of the present invention, communications plugs are provided that include eight plug blades and a printed circuit board that has eight conductive paths that are electrically connected to respective ones of the eight plug blades. The plug blades and the conductive paths may be arranged and numbered pursuant to the TIA/EIA 568 type B configuration. The plug may further include 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. In some embodiments, the plug may further include a third crosstalk injection circuit between the third conductive path and either the first conductive path or the second conductive path.
The first and second crosstalk injection circuits (and the third crosstalk injection circuit, if provided) may substantially cancel the differential-to-common mode crosstalk injected from the third differential pair onto the second differential pair. The crosstalk injection circuits may comprise, for example, capacitors that are implemented on the printed circuit board.
Pursuant to still further embodiments of the present invention, communications plugs are provided that include first through fourth differential transmission lines. These plugs further include a differential-to-common mode crosstalk cancellation circuit that substantially cancels differential-to-common mode crosstalk that is injected within the plug from the third differential transmission line onto the second differential transmission line. Moreover, the third differential transmission line in these plugs is configured to inject differential-to-differential crosstalk onto the second transmission line.
Patch cords are also provided that include the above-described communications plugs.
Embodiments of the present invention will now be discussed in greater detail with reference to the drawings.
As discussed above, differential-to-common mode crosstalk may be injected from a first differential transmission line to a second differential transmission line in a communications connector such as a modular plug or jack (e.g., from pair 3 to pair 2 and/or to pair 4 in an RJ-45 jack). This differential-to-common mode crosstalk may give rise to alien crosstalk that may degrade the performance of other channels in the communications system in which the connectors are used. The prior art has suggested at least two solutions to the above-described problem of differential-to-common mode crosstalk. In the first solution, the differential-to-common mode crosstalk that is generated in the plug of a mated plug jack connection and in the plug jack mating area of the jack is compensated for in the jack. This approach is illustrated in U.S. Pat. No. 5,967,853, which is discussed in greater detail herein, and in U.S. Pat. No. 7,204,722 (“the '722 patent”), which discloses including a crossover in the contact wires of pair 3 in order to cancel such differential-to-common mode crosstalk. In the second solution, an expanded loop on the conductors of pair 3 is provided in an otherwise conventional RJ-45 plug. This approach is illustrated in U.S. Pat. No. 7,220,149 (“the '149 patent”). As explained in the '149 patent, both the plug blades and conductors of pair 3 in most conventional plugs are spatially unbalanced relative to the outside pairs 2 and 4, particularly in the plug blades and the region approaching the blades. The '149 patent discloses providing an expanded loop in the conductors of pair 3 that corrects for the spatial imbalance between (a) pairs 2 and 3 and (b) pairs 3 and 4 caused by the positions of the blades and conductors in a conventional plug.
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The conductors 101-108 may be maintained in pairs within the plug 116. A cruciform separator 130 may be included in the rear portion of the housing 120 that separates each pair 111-114 from the other pairs 111-114 in the cable 109 to reduce crosstalk in the plug 116. The conductors 101-108 of each pair 111-114 may be maintained as a twisted pair all of the way from the rear opening 128 of plug 116 up to the back edge of the printed circuit board 150.
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The plug blades 141-148 are configured to make mechanical and electrical contact with respective contacts, such as, for example, spring jackwire contacts, of a mating communications jack. Each of the eight plug blades 141-148 is mounted at the front portion of the printed circuit board 150. The plug blades 141-148 may be substantially aligned in a side-by-side relationship along the transverse dimension. Each of the plug blades 141-148 includes a first section that extends forwardly (longitudinally) along a top surface of the printed circuit board 150, a transition section that curves through an angle of approximately ninety degrees and a second section that extends downwardly from the first section along a portion of the front edge of the printed circuit board 150. The portion of each plug blade 141-148 that is in physical contact with a contact structure (e.g., a jackwire contact) of a mating jack during normal operation is referred to herein as the “plug jack mating point” of the plug contact 141-148. The plug contacts 141-148 are also referred to herein as “plug blades.”
In some embodiments, each of the plug blades 141-148 may comprise, for example, an elongated metal strip having a length of approximately 140 mils, a width of approximately 20 mils and a height (i.e., a thickness) of approximately 20 mils. Each plug blade 141-148 may include a projection that extends downwardly from the bottom surface of the first section of the plug blade. The printed circuit board 150 includes eight metal-plated vias 131-138 that are arranged in two rows along the front edge thereof. The downwardly-extending projections of each plug blade 141-148 is received within a respective one of the metal-plated vias 131-138 where it may be press-fit, welded or soldered into place to mount the plug blades 141-148 on the printed circuit board 150. In some embodiments, the projections may be omitted and the plug blades 141-148 may be soldered or welded directly onto conductive structures (e.g., pads) that are deposited on top of the respective vias 131-138.
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A total of four differential transmission lines 171-174 are provided through the plug 116. The first differential transmission line 171 includes the end portions of conductors 104 and 105, the plated pads 154 and 155, the conductive paths 164 and 165, and the plug blades 144 and 145. The second differential transmission line 172 includes the end portions of conductors 101 and 102, the plated pads 151 and 152, the conductive paths 161 and 162, and the plug blades 141 and 142. The third differential transmission line 173 includes the end portions of conductors 103 and 106, the plated pads 153 and 156, the conductive paths 163 and 166, and the plug blades 143 and 146. The fourth differential transmission line 174 includes the end portions of conductors 107 and 108, the plated pads 157 and 158, the conductive paths 167 and 168, and the plug blades 147 and 148. As shown in
In contrast, the conductive paths 163 and 166 that form the third differential transmission line 173 do not run in a side-by-side fashion across the printed circuit board 150. Instead, adjacent the conductive pad 156, conductive path 166 transitions from the bottom surface of printed circuit board 150 to the top surface at a first conductive via 191. The top of a first conductive via 191 is positioned between conductive paths 161 and 162, and conductive path 166 runs between conductive paths 161 and 162 from the top of the first conductive via 191 to the top of a second conductive via 192. Conductive path 166 then transitions at the second conductive via 192 to the bottom surface of printed circuit board 150, where it is routed to connect to the conductive via 136 that is used to mount plug blade 146 onto the printed circuit board 150.
In a similar fashion, conductive path 163 is routed from conductive pad 153 to the other side of printed circuit board 150, where it transitions from the bottom surface of the printed circuit board 150 to the top surface at a third conductive via 193. Conductive path 163 then travels a short distance on the top surface of printed circuit board 150 to a fourth conductive via 194 that transitions conductive path 163 back to the bottom surface of the printed circuit board 150. The bottom of the fourth conductive via 194 is positioned between conductive paths 167 and 168, and conductive path 163 runs between conductive paths 167 and 168 from the bottom of the fourth conductive via 194 to the bottom of a fifth conductive via 195. Conductive path 163 then transitions at the fifth conductive via 195 to the top surface of printed circuit board 150, where is routed to connect to a sixth conductive via 196. Conductive path 163 then transition at the sixth conductive via 196 back to the bottom surface of the printed circuit board 150 where it is routed to the conductive via 133 that is used to mount plug blade 143 onto the printed circuit board 150. Conductive vias 193-196 are merely used to transition conductive path 163 between the top and bottom surfaces of the printed circuit board 150 so that conductive path 163 may cross other of the conductive paths 161-168 without short-circuiting.
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The expanded loop 190 is provided in differential transmission line 173 to reduce or cancel the differential-to-common mode crosstalk that is injected from differential transmission line 173 onto differential transmission lines 172 and 174. In particular, by routing a segment 166′ of conductive path 166 so that it runs between segments 161′, 162′ of differential transmission line 172, while corresponding segment 163′ of conductive path 163 is maintained far away from segments 161′, 162′ of differential transmission line 172, a third unbalanced coupling region 203 is formed in plug 116. This third unbalanced coupling region 203 injects differential-to-common mode crosstalk from differential transmission line 173 onto differential transmission line 172 that has the opposite polarity of the differential-to-common mode crosstalk that is injected in region 202, and which hence acts to cancel the differential-to-common mode crosstalk that is injected in region 202. Similarly, by routing a segment 163′ of conductive path 163 so that it runs between segments 167′, 168′ of differential transmission line 174, while corresponding segment 166′ of conductive path 166 is maintained far away from segments 167′, 168′ of differential transmission line 174, a fourth unbalanced coupling region 204 is formed in plug 116. This fourth unbalanced coupling region 204 injects differential-to-common mode crosstalk from differential transmission line 173 onto differential transmission line 174 that has the opposite polarity of the differential-to-common mode crosstalk that is injected in region 201, and which hence acts to cancel the differential-to-common mode crosstalk that is injected in region 201.
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As noted above, in some embodiments, segments 163′ and/or 166′ may be routed on an intermediate layer of the printed circuit board 150′. In order to ensure that intermediate printed circuit board layers can manage the current flow without excessive heating, the segments 163′ and/or 166′ may be widened to reduce the current density per unit volume in these conductive traces. Notably, the widened trace segments 166′ and 163′ may exhibit increased capacitive coupling with the segments 161′, 162′ of differential transmission line 172 and the 167′, 168′ of differential transmission line 174, respectively. Such increased capacitive coupling may be disadvantageous in some cases, as it may be more effective to locate as much of the capacitive coupling as possible very near the plug jack mating point. Routing segments 166′ and 163′ between the segments 161′, 162′ of differential transmission line 172 and the 167′, 168′ of differential transmission line 174, respectively, may also negatively impact the return loss on differential transmission lines 172 and 174.
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The embodiments of
The third and fourth unbalanced coupling regions 203 and 204 may be designed to inject differential-to-common mode crosstalk between differential transmission line 173 and differential transmission lines 172 and 174, respectively, that is sufficient to substantially cancel the differential-to-common mode crosstalk that is injected by differential transmission line 173 onto differential transmission lines 172 and 174 in the plug blade region of plug 116. If it is anticipated that additional differential-to-common mode crosstalk may be injected by differential transmission line 173 onto differential transmission lines 172 and 174 in the leadframe of a mating jack, the amount of differential-to-common mode crosstalk injected by differential transmission line 173 onto differential transmission lines 172 and 174 may be increased so that this additional differential-to-common mode crosstalk is also substantially cancelled by the differential-to-common mode crosstalk that is injected in the third and fourth unbalanced coupling regions 203 and 204. The amount of differential-to-common mode crosstalk that is introduced in the third and fourth unbalanced coupling regions 203 and 204 may be adjusted in a variety of ways including, for example, adjusting the lengths of the coupling segments 161′/162′/166′ and 166′/167′/168′, adjusting the thickness of these segments, adjusting the separation of these segments, etc.
As noted above, the plug blades 141-148 may comprise “low profile” plug blades that have much smaller facing surface areas. This may significantly reduce the amount of offending crosstalk that is generated between the various differential pair combinations in the plug 116. The terminations of the conductors 101-108 onto the printed circuit board 150 and the routings of the conductive paths 161-168 may also be designed to reduce or minimize the amount of offending crosstalk that is generated between the differential pairs 171-174. As a result, the amount of offending crosstalk that is generated in the plug 116 may be significantly less than the offending crosstalk levels specified in the relevant industry-standards documents. A plurality of offending crosstalk circuits thus may be provided in plug 116, if necessary, that inject additional offending crosstalk between the pairs in order to bring the plug 116 into compliance with these industry standards documents.
The use of low profile plug blades and offending crosstalk circuits may be beneficial, for example, because if everything else is held equal, more effective crosstalk cancellation may generally be achieved if the offending crosstalk and the compensating crosstalk are injected very close to each other in time (as this minimizes the phase shift that occurs between the point(s) where the offending crosstalk is injected and the point(s) where the compensating crosstalk is injected). The plug 116 may be designed to generate low levels of offending crosstalk in the back portion of the plug (i.e., in portions of the plug 116 that are at longer electrical delays from the plug-jack mating regions of the plug blades 141-148), and the offending crosstalk circuits are provided to inject the bulk of the offending crosstalk at very short delays from the plug jack mating regions of the plug blades 141-148. This may allow for more effective cancellation of the offending crosstalk in a mating jack.
As shown in the circuit diagram of
Pursuant to further embodiments of the present invention, communications plugs (and related patch cords) are provided that may substantially cancel the differential-to-common mode crosstalk that is injected between various of the differential transmission lines though the plug while maintaining predetermined amounts of differential-to-differential crosstalk between these differential transmission lines. These plugs may be industry standards compliant plugs that exhibit the required amounts of differential-to-differential crosstalk while generating significantly lower levels of differential-to-common mode crosstalk, thereby reducing any need to cancel substantial amounts of differential-to-common mode crosstalk in a mating jack. Before describing these communications plugs, it is helpful to briefly discuss various known schemes for cancelling differential-to-differential and differential-to-common mode crosstalk.
In particular,
As noted above, it may be advantageous to reduce the amount of differential-to-common mode crosstalk that arises in a communications plug in order to reduce or eliminate any need to compensate for this crosstalk in a mating jack. However, unlike a mated plug-jack combination, many communications plugs such as plugs that comply with the ANSI/TIA-568-C.2 standard are required to exhibit specified levels of offending differential-to-differential crosstalk between the various transmission lines through the plug. Pursuant to embodiments of the present invention, communications plugs are provided that may exhibit little or no differential-to-common mode crosstalk between various pair combinations while providing the requisite levels of differential-to-differential crosstalk between each pair combination. The plugs according to embodiments of the present invention include a plurality of crosstalk injection circuits that inject crosstalk between various of the conductive paths through the plug where the magnitudes of the crosstalk injected by these circuits are selected to cancel the differential-to-common-mode crosstalk while providing the requisite levels of offending differential-to-differential crosstalk.
The crosstalk injection circuits that are provided and methods for selecting the values for these crosstalk injection circuits will now be discussed with reference to
As is apparent from
As shown in
The following analysis shows how to calculate the amount of crosstalk to inject between pairs 2 and 3 using the crosstalk injection circuits Cc1, Cc2 and Cc3 in order to substantially cancel the differential-to-common-mode crosstalk while achieving the requisite amount of differential-to-differential crosstalk between pairs 2 and 3. The differential-to-differential and differential-to-common-mode crosstalk coupling effects in the crosstalking region can be represented by Equations (1)-(3) as follows:
Csu=Cs3+Cs4−Cs1−Cs2 (1)
Csb23=Cs2+Cs4−Cs1−Cs3 (2)
Csb32=Cs1+Cs4−Cs2−Cs3 (3)
where:
Csu is the unbalanced coupling (both capacitive and inductive) in the crosstalking region, responsible for differential-to-differential crosstalk between pairs 2 and 3;
Csb23 is the balanced coupling (both capacitive and inductive) in the crosstalking region, responsible for differential-to-common-mode crosstalk when pair 2 is driven and pair 3 is idle; and
Csb32 is the balanced coupling (both capacitive and inductive) in the crosstalking region, responsible for differential-to-common-mode crosstalk when pair 3 is driven and pair 2 is idle.
The term “unbalanced coupling” describes the total coupling between two pairs that contributes to differential-to-differential crosstalk, and the term “balanced coupling” describes the total coupling between two pairs contributing to differential-to-common-mode crosstalk. For total differential-to-common mode crosstalk cancellation while providing the industry-standardized amount of differential-to-differential crosstalk between pairs 2 and 3, the three crosstalk injection circuits Cc1, Cc2, and Cc3 should be chosen to produce balanced couplings that are equal to and opposite in polarity to those in the crosstalking region while producing unbalanced couplings that are equal to and opposite in polarity to in the crosstalking region minus the industry-standardized amount of offending crosstalk. Thus, the three crosstalk injection circuits Cc1, Cc2, and Cc3 should inject crosstalk having the magnitudes expressed in Equations (4)-(6) as follows:
−Csu=Cc3−Cc1−Cc2−K (4)
−Csb23=Cc2−Cc1−Cc3 (5)
−Csb32=Cc1−Cc2−Cc3 (6)
where:
K is the magnitude of the offending differential-to-differential crosstalk that should be injected between pairs 2 and 3 according to the industry standards.
Solving Equations (4)-(6) for Cc1, Cc2, and Cc3 yields Equations (7)-(9) as follows:
Cc1=(Csu+Csb23−K)/2 (7)
Cc2=(Csu+Csb32−K)/2 (8)
Cc3=(Csb23+Csb32)/2 (9)
Substituting for Csu, Csb23, and Csb32 from Equations (1)-(3) into Equations (7)-(9) yields Equations (10)-(12) as follows:
Cc1=Cs4−Cs1−K/2 (10)
Cc2=Cs4−Cs2−K/2 (11)
Cc3=Cs4−Cs3 (12)
As indicated by Equations (10)-(12), knowing Cs1, Cs2, Cs3, and Cs4, the values of Cc1, Cc2, and Cc3 can be calculated. The same can be achieved by inferring Csu, Csb23, and Csb32 from differential-to-differential and differential-to-common-mode crosstalk measurements performed for the crosstalking region.
While the above analysis uses three crosstalk injection circuits Cc1, Cc2 and Cc3 to inject crosstalk that will substantially cancel the differential-to-common mode crosstalk while leaving the industry standardized amount of differential-to-differential offending crosstalk between pairs 2 and 3, it will be appreciated that a fourth crosstalk injection circuit Cc4 could be added between R2 and T3. The addition of this fourth crosstalk injection circuit Cc4 provides an additional degree of freedom.
Subtracting above equation (11) from above equation (10) yields,
Cc1−Cc2=Cs2−Cs1 (13)
Typically Cs1 is greater that Cs2, since plug blade 241 is physically closer to plug blade 243 than is plug blade 242 to plug 246 for the pairs 2 and 3. As a consequence of this and above equation (10), Cc2 has to be greater than Cc1 for positive values of Cc1 and Cc2. This implies that the compensation scheme of
K=2(Cs4−Cs1) (14)
Thus the crosstalk compensation scheme of
Next, reference is made to
As shown in
Cc2′=Cs4−Cs2−K/2 (15)
Cc3′=Cs4−Cs3 (16)
Finally, reference is made to
As shown in
−Csu=Cc3″+Cc4″−Cc2″−K (17)
−Csb23=Cc2″+Cc4″−Cc3″ (18)
−Csb32=Cc4″−Cc2″−Cc3″ (19)
Solving Equations (17) through (19) for Cc2″, Cc3″, and Cc4″ yields Equations (20) through (22) as follows:
Cc2″=(Csb32−Csb23)/2 (20)
Cc3″=(Csb32−Csu+K)/2 (21)
Cc4″=(−Csb23−Csu+K)/2 (22)
Substituting for Csu, Csb23, and Csb32 from Equations (1) through (3) into Equations (20) through (22) yields Equations (23) through (25) as follows:
Cc2″=Cs1−Cs2 (23)
Cc3″=Cs1−Cs3+K/2 (24)
Cc4″=Cs1−Cs4+K/2 (25)
As shown in the analysis above, the solution presented with respect to
It will also be appreciated that the above calculations derive values for the four crosstalk injection circuits that provide solutions for pairs 2 and 3 of a four pair connector. Those skilled in the art will understand that the above analysis is equally applicable to pairs 3 and 4 and that the same principles can be extended to derive values for crosstalk injection circuits that will compensate for crosstalk between other pair combinations in a four pair connector or for pair combinations in other types of mated plug jack connectors.
It will be appreciated that the printed circuit board 150 that is illustrated in
As noted above, in some embodiments, the first, second, third and/or fourth crosstalk injection circuits may be implemented as capacitors that inject the crosstalk close in time to the offending crosstalk Cs1, Cs2, Cs3 and Cs4. This may reduce and/or minimize the delay, which may more effectively cancel the differential-to-common mode crosstalk. However, differential-to-common mode crosstalk may appear as both NEXT and FEXT, and hence it may be desirable in some embodiments to include inductive components in at least some of the first, second, third and/or fourth crosstalk injection circuits in order to better cancel both differential-to-common mode NEXT and FEXT. However, at least some of the inductive components may have greater associated delays which may degrade the cancellation, and hence there may be inherent tradeoffs with respect to whether or not to include inductive components in the first, second, third and/or fourth crosstalk injection circuits, at least in some embodiments.
Thus, pursuant to some embodiments of the present invention, RJ-45 communications plugs (and related patch cords) are provided that include at least a first crosstalk injection circuit that is connected between a first conductive path of a first differential pair and a first conductive path of a second differential pair, and a second crosstalk injection circuit that is connected between the second conductive path of the first differential pair and the first conductive path of the second differential pair. The first and second crosstalk injection circuits may be designed to substantially cancel the differential-to-common mode crosstalk injected between the first and second differential pairs. In some embodiments, the plug may further include a third crosstalk injection circuit that is connected either (1) between the first conductive path of the first differential pair and the second conductive path of the second differential pair or (2) between the second conductive path of the first differential pair and the second conductive path of the second differential pair. This third crosstalk injection circuit may act in conjunction with the first and second crosstalk injection circuits to substantially cancel the differential-to-common mode crosstalk injected between the first and second differential pairs.
In some embodiments, the first, second and/or third crosstalk injections circuits may be implemented as capacitors on a printed circuit board of the plug. These capacitors may, for example, inject crosstalk onto the signal carrying paths directly adjacent to the connection of each path to its respective plug blade.
As is also made clear above, the plugs (specifically including RJ-45 plugs) according to embodiments of the present invention may include a differential-to-common mode crosstalk cancellation circuit that substantially cancels differential-to-common mode crosstalk that is injected within the plug from a first differential transmission line onto a second differential transmission line while still ensuring that differential-to-differential crosstalk is injected from the first differential transmission line onto the second differential transmission line when the first differential transmission line is excited differentially. The amount of differential-to-differential crosstalk that is injected may, for example, be the amount specified in a relevant industry standards document.
The plugs according to embodiments of the present invention thus may include an offending crosstalk circuit that is separate from the plug blades that injects crosstalk between first and second differential transmission lines, where the offending crosstalk circuit is between a ring conductive path and a tip conductive path, as well as a differential-to-common mode crosstalk cancellation circuit that is electrically connected between the first and second differential transmission lines. The differential-to-common mode crosstalk cancellation circuit may substantially cancel the differential-to-common mode crosstalk that is injected within the plug between the first and second differential transmission lines.
Thus, using the above-described techniques, mode conversion between for example, pairs 2 and 3 may be managed (i.e., cancelled) in the communications plug. This may reduce any need to compensate for mode conversion in a mating communications jack. As known to those of skill in the art, one technique for compensating for mode conversion in a four-pair T-568B type communications jack is to include a crossover on pair 3 as is described, for example, in the above-referenced U.S. Pat. No. 7,204,722. However, as communications plugs and jacks are designed to operate at higher data rates, it may be difficult to physically implement such crossovers in a reliable fashion so that they will inject the compensating crosstalk at sufficiently short delays. Thus, by compensating for the differential-to-common mode crosstalk in the communications plug it may be possible to omit such crossovers in some jack designs.
It will be appreciated that in shielded communications systems, the impact of differential-to-common mode crosstalk may be reduced as the shielding may reduce the amount of alien crosstalk in the communications system. However, the plugs according to embodiments of the present invention may still be useful in shielded communications systems for various reasons including further reducing the amount of alien crosstalk and improving insertion loss performance.
Pursuant to further embodiments of the present invention, resistors may be placed in series with one or more of the first, second, third and/or fourth crosstalk injection circuits. These series resistors may further reduce mode conversion and/or facilitate managing the return loss along one or more of the differential transmission lines.
As shown in
As is further shown in
As is further shown in
While in the description above with reference to
The present invention is not limited to the illustrated embodiments discussed above; rather, these embodiments are intended to fully and completely disclose the invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.
Spatially relative terms, such as “top,” “bottom,” “side,” “upper,” “lower” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Herein, the term “signal current carrying path” is used to refer to a current carrying path on which an information signal will travel on its way from the input to the output of a communications plug. Signal current carrying paths may be formed by cascading one or more conductive traces on a wiring board, metal-filled apertures that physically and electrically connect conductive traces on different layers of a printed circuit board, portions of plug blades, conductive pads, and/or various other electrically conductive components over which an information signal may be transmitted. Branches that extend from a signal current carrying path and then dead end such as, for example, a branch from the signal current carrying path that forms one of the electrodes of an inter-digitated finger or plate capacitor, are not considered part of the signal current carrying path, even though these branches are electrically connected to the signal current carrying path. While a small amount of current will flow into such dead end branches, the current that flows into these dead end branches generally does not flow to the output of the plug that corresponds to the input of the plug that receives the input information signal.
Well-known functions or constructions may not be described in detail for brevity and/or clarity. As used herein the expression “and/or” includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
All of the above-described embodiments may be combined in any way to provide a plurality of additional embodiments.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.
The present application claims priority under 35 U.S.C. §120 as a continuation of U.S. patent application Ser. No. 14/662,261, filed Mar. 19, 2015, which is a continuation of U.S. patent application Ser. No. 14/481,935, filed Sep. 10, 2014, which issued as U.S. Pat. No. 9,011,182, which is a divisional application of U.S. patent application Ser. No. 13/803,160, filed Mar. 14, 2013, which issued as U.S. Pat. No. 8,858,267. The entire content of each of these application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14481935 | Sep 2014 | US |
| Child | 14662261 | US | |
| Parent | 13803160 | Mar 2013 | US |
| Child | 14481935 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14662261 | Mar 2015 | US |
| Child | 15386218 | US |
