Patent Grant
10069258
The present invention relates generally to communications connectors and, more particularly, to communications plugs such as RJ-45 plugs that may support high data rate communications.
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 backward 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. 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.
Another important parameter in communications connectors is the return loss that is experienced along each differential pair (i.e., differential transmission line) through the connector. The return loss of a transmission line is a measure of how well the transmission line is impedance matched with a terminating device or with loads that are inserted along the transmission line. In particular, the return loss is a measure of the signal power that is lost due to signal reflections that may occur at discontinuities (impedance mismatches) in the transmission line. Return loss is typically expressed as a ratio in decibels (dB) as follows:
where RL(dB) is the return loss in dB, Pi is the incident power and Pr is the reflected power. High return loss values indicate a good impedance match (i.e., little signal loss due to reflection), which results in lower insertion loss values, which is desirable.
Pursuant to embodiments of the present invention, patch cords are provided that include a communications cable that has a first conductor and a second conductor that form a first differential pair, and a third conductor and a fourth conductor that form a second differential pair and a plug that is attached to the communications cable. The plug includes a housing that receives the communications cable, first through fourth plug contacts that are within the housing, and a printed circuit board. The printed circuit board includes first through fourth conductive paths that connect the respective first through fourth conductors to respective ones of the first through fourth plug contacts. The plug further includes a first conductive shield that extends above a top surface of the printed circuit board that is disposed between the first differential pair and the second differential pair.
In some embodiments, the communications cable further includes a fifth conductor and a sixth conductor that form a third differential pair, and a seventh conductor and an eighth conductor that form a fourth differential pair. In such embodiments, the plug may further include a second conductive shield that extends below a bottom surface of the printed circuit board and that is disposed between the third differential pair and the fourth differential pair. In such embodiments, the first through fourth conductors may terminate into the top side of the printed circuit board and the fifth through eighth conductors may terminate into the bottom side of the printed circuit board.
In some embodiments, the plug may also include a conductive crosstail that is mounted in a back end of the housing, where the conductive crosstail includes a first fin that forms the first shield, a second fin that forms the second shield, along with a third fin and a fourth fin. A notch may be provided in a back edge of the printed circuit board, and the conductive crosstail may be received within the notch so that the first fin of the crosstail forms the first shield that extends above the top surface of the printed circuit board and the second fin of the crosstail forms the second shield that extends below the bottom surface of the printed circuit board. The first fin and the second fin may extend farther forwardly in the housing than do the third fin and the fourth fin. The third fin and the fourth fin may each include a widened section adjacent to the printed circuit board.
In some embodiments, a thickness of the printed circuit board may be approximately equal to the thickness of the third fin plus twice the thickness of an insulation layer on the first conductor. In other embodiments, the thickness of the printed circuit board may be approximately equal to the thickness of the third fin plus twice the thickness of an insulation layer on the first conductor plus twice the thickness of a shield that surrounds the first and second conductors.
Pursuant to embodiments of the present invention, communications plugs are provided that include first through fourth conductive paths that electrically connect respective first through fourth inputs of the plug to respective first through fourth outputs of the plug. The first and second conductive paths comprise a first differential pair of conductive paths for transmitting a first information signal, and the third and fourth conductive paths comprise a second differential pair of conductive paths for transmitting a second information signal. A first section of the first conductive path and a second section of the second conductive path are configured to have generally the same instantaneous current direction and are positioned to both capacitively and inductively couple with each other.
In some embodiments, the amount of capacitive coupling may be at least half the amount of the inductive coupling. Moreover, the plug may further include a flexible printed circuit board, and the first section of the first conductive path may be on a first side of the flexible printed circuit board and the second section of the second conductive path may be on a second side of the flexible printed circuit board that is opposite the first side.
In some embodiments, the ratio of the capacitive coupling between first section of the first conductive path and the second section of the second conductive path to the inductive coupling between first section of the first conductive path and the second section of the second conductive path may be selected to provide a local maximum in a return loss spectrum for the first differential pair of conductive paths. Additionally, a third section of the third conductive path and a fourth section of the fourth conductive path may be configured to have generally the same instantaneous current direction and may be positioned to both capacitively and inductively couple with each other.
Pursuant to embodiments of the present invention, communications plugs are provided that include a housing having a plug aperture, a flexible printed circuit board that is at least partly mounted within the housing, and first and second conductive paths that electrically connect first and second inputs of the plug to respective first and second outputs of the plug. 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. 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 the first and second conductive trace sections are configured to both inductively and capacitively couple with each other.
In some embodiments, the first conductive trace section comprises a spiral. This spiral may at least partially overlap the second conductive trace section. An amount of capacitive coupling between the first conductive trace section and the second conductive trace section may be at least half an amount of inductive coupling between the first conductive trace section and the second conductive trace section.
Pursuant to embodiments of the present invention, RJ-45 communications plugs are provided that include a housing, a printed circuit board within the housing and a lossy dielectric material between at least one side of the printed circuit board and the housing. In some embodiments, the lossy dielectric material may be a carbon loaded foam. The lossy dielectric material may be injected within the housing, and may comprise a curable material. The lossy dielectric material may substantially fill the open area within the housing.
Pursuant to embodiments of the present invention, patch cords are provided that include a communications cable that includes eight conductors that are arranged as four differential pairs of conductors and a plug that is attached to the communications cable. The plug includes a housing that receives the communications cable, the housing having a front surface, a top surface and a bottom surface and a plurality of slots that each have a front portion that extends along the front surface and a top portion that extends along the top surface. A printed circuit board is at least partially mounted within the housing and includes eight conductive paths that are electrically connected to the respective eight conductors of the communications cable. Eight plug blades that are electrically connected to the respective eight conductive paths on the printed circuit board, each of the plug blades having a front surface that is exposed by the front portion of a respective one of the slots and a top portion that is exposed by the top portion of the respective slot. A top surface of the printed circuit board defines an oblique angle with a plane defined by the top surfaces of the eight plug blades.
In some embodiments, at least some of the plug blades comprise skeletal plug blades. All eight conductors of the communications cable may be terminated into the same side of the printed circuit board. In some embodiments, a front portion of the printed circuit board may be angled towards the bottom surface of the housing, and the eight conductors of the communications cable may be terminated into a bottom side of the printed circuit board. In other embodiments, the front portion of the printed circuit board may be angled towards the top surface of the housing, and the eight conductors of the communications cable may be terminated into a top side of the printed circuit board. At least two of the conductors may terminate into a front half of the printed circuit board and at least four of the conductors may terminate into a back half of the printed circuit board.
Pursuant to embodiments of the present invention, communications plugs are provided that include a housing, a flexible printed circuit board mounted in the housing, the flexible printed circuit board having a first conductive path and a second conductive path that form a first differential pair of conductive paths and a third conductive path and a fourth conductive path that form a second differential pair of conductive paths. First through fourth plug contacts are electrically connected to the respective first through fourth conductive paths. A section of the first conductive path is on a first side of the flexible printed circuit board and a section of the third conductive path is on a second, opposite side of the flexible printed circuit board and are configured to both inductively and capacitively couple.
In some embodiments, the section of the first conductive path and the section of the third conductive path may partially overlap but may not completely overlap. The amount of capacitive coupling between the section of the first conductive path and the section of the third conductive path may be at least half an amount of inductive coupling between the section of the first conductive path and the section of the third conductive path.
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 support high data rate communications. Some embodiments of these patch cords/plugs may operate at frequencies supporting 40 gigabit communications.
In some embodiments, the communications plug may include a printed circuit board that is used to electrically connect each conductor of a communications cable to a corresponding plug blade of the plug. Conductive shields may be provided that extend above and/or below the printed circuit board that reduce coupling between at least a first pair of the conductors of the cable and a second pair of the conductors of the cable in the region where the conductors are terminated into the printed circuit board. In some embodiments, the conductive shields may comprise a pair of vertical fins on a metal-plated conductor-organizing crosstail that extend above and below the back portion of the printed circuit board. The thickness of the printed circuit board may be matched to the pitch of the bare conductors that extend from the crosstail onto the printed circuit board.
In some embodiments, the communications plugs include a flexible printed circuit board. These flexible printed circuit boards may include one or more circuits that may be used to improve the return loss of one or more of the differential transmission lines through the plug. For example, in some embodiments, the differential transmission lines may be configured so that the two conductive paths thereof both inductively and capacitively couple. These couplings may create resonances, end the resonances may be selected so that the return loss of the transmission line may be improved in a selected frequency range. In other embodiments, one or both conductive paths of the differential transmission line may be arranged so as to self-couple both inductively and capacitively to generate such resonances. High amounts of inductive and capacitive coupling may be generated by running the two conductive paths of the differential pair (or a single conductive path that is routed to self-couple) on opposite sides of the flexible printed circuit board.
In embodiments that include flexible printed circuit boards, high levels of offending inductive crosstalk may be generated by routing the traces associated with two different differential transmission lines on opposite sides of the flexible printed circuit board in an overlapping arrangement. As the dielectric layer of flexible printed circuit boards may be very thin (e.g., 1 mil), very high amounts of offending inductive crosstalk may be generated in a very short distance. This may facilitate injecting the offending inductive crosstalk closer to the plug-jack mating point, which may make the offending crosstalk easier to cancel in a mating jack.
In still further embodiments, RJ-45 plugs are provided that include a printed circuit board that is mounted at an angle within the plug housing. By angling the printed circuit board, increased space may be provided so that more than four of the conductors of the cable may be terminated into one side of the printed circuit board. In some embodiments, the plug blades are mounted on a top side of the printed circuit board, and the printed circuit board is angled within the housing so that all eight conductors of the cable can be terminated into the bottom side of the printed circuit board.
In yet further embodiments, communications plugs are provided which have a lossy dielectric injected into a housing thereof. The lossy dielectric may be a liquid or a foam, and may be cured by exposure to air, heat, ultraviolet light or the like so that it hardens into a solid material. The lossy dielectric may convert electric fields that emanate from the differential transmission lines within the plug into heat, thereby potentially reducing differential-to-differential crosstalk, differential-to-common mode crosstalk and alien crosstalk.
Embodiments of the present invention will now be discussed in greater detail with reference to the drawings.
As shown in
As is also shown in
The printed circuit board 150 may comprise, for example, a conventional printed circuit board, a specialized printed circuit board (e.g., a flexible printed circuit board) or any other appropriate type of wiring board. In the embodiment of the present invention depicted in
As shown in
The conductors 101-108 may be maintained in pairs within the plug 116. A cruciform separator or “crosstail” 190 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.
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.
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 optionally include a projection 149 that extends downwardly from the bottom surface of the first section of the plug blade (see
Turning again to
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, the plug blades 144 and 145, and the metal-plated vias 134, 135. 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, the plug blades 141 and 142, and the metal-plated vias 131, 132. 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, the plug blades 143 and 146, and the metal-plated vias 133, 136. 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, the plug blades 147 and 148, and the metal-plated vias 137, 138. As shown in
A plurality of offending crosstalk circuits are also included on the printed circuit board 150. “Offending” crosstalk arises in industry standardized RJ-45 plug jack interface because of the unequal coupling that occurs between the four differential transmission lines through RJ-45 plugs and jacks in the plug jack mating region of the plug contacts. In order to reduce the impact of this offending crosstalk, communications jacks were developed in the early 1990s that included circuits that introduced “compensating” crosstalk that was used to cancel much of the “offending” crosstalk that was being introduced in the plug jack mating region. 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.
The plug 116 includes printed circuit board mounted plug blades that are “low profile” plug blades in that the adjacent plug blades 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 (as traditionally much of the offending crosstalk was generated due to capacitive coupling between adjacent plug blades). 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 are provided in plug 116 that inject additional offending crosstalk between the pairs in order to bring the plug 116 into compliance with these industry standards documents.
The above-described approach 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 is 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
Moreover, four conductive vias 133-1, 134-1, 135-1 and 135-2 are provided that are used to generated additional offending inductive crosstalk. In particular, conductive via 133-1 is used instead of conductive via 133 to transfer signals passing along conductive path 163 from the trace on the bottom side of printed circuit board 150 to the top side of the printed circuit board 150. Conductive via 133-1 is transversely aligned with conductive via 134. By moving the vertical signal-current carrying path for conductive path 163 rearwardly by using conductive via 133-1 instead of conductive via 133 for the current-carrying path, the vertical current-carrying path for conductive path 163 is moved closer to conductive via 134 and farther away from conductive via 135. The net effect of this change is to significantly increase the offending inductive crosstalk that is generated between differential transmission lines 171 and 173, as the currents flowing through conductive vias 133-1 and 134 will couple heavily (due to their close proximity). Thus, the conductive vias 133-1 and 134 together form a first offending crosstalk inductive coupling section 186 which generates offending inductive crosstalk between differential transmission lines 171 and 173.
In a similar fashion, conductive via 135-1 is used instead of conductive via 135 to transfer signals from the trace on the bottom side of printed circuit board 150 that is part of conductive path 165 to the top side of the printed circuit board 150. The additional conductive via 135-1 is transversely aligned with conductive via 136. The net effect of this change is to significantly increase the offending inductive crosstalk that is generated between differential transmission lines 171 and 173, as the currents flowing through conductive vias 135-1 and 136 will couple heavily (due to their close proximity). Thus, the conductive vias 135-1 and 136 together form a second offending crosstalk inductive coupling section 187 which generates offending inductive crosstalk between differential transmission lines 171 and 173.
The offending inductive crosstalk circuits 186, 187 inject the offending crosstalk relatively close to the plug jack mating points on the plug blades 143-146 of differential transmission lines 171, 173. The offending inductive crosstalk is generated in the vertical conductive vias 133-1, 134, 135-1, 136 because higher levels of inductive coupling can generally be generated in the conductive via structures than can be generated, for example, through the use of inductively coupling side-by-side conductive traces on the printed circuit board 150. Two additional conductive vias 134-1 and 135-2 are provided through the printed circuit board 150. The conductive vias 134-1 and 135-2 are provided to transfer the conductive paths 164 and 165, respectively, from the top surface to the bottom surface of printed circuit board 150 so that current will flow through conductive vias 134 and 135-1, as is necessary for proper operation of the offending inductive crosstalk circuits 186, 187, and to also arrange the direction of current flow through conductive vias 134 and 135-1 relative to conductive vias 133-1 and 136 so that inductive coupling will occur between vias 133-1 and 134 and between vias 135-1 and 136. Additional offending inductive crosstalk is generated between differential transmission lines using conductive trace segments that are routed side-by-side on the printed circuit board 150.
As noted above, the plug 116 may be designed to mostly inject the industry standardized levels of offending crosstalk between the differential transmission lines at locations close to the plug jack mating points of plug blades 141-148. Various features of plug 116 that may facilitate reducing the amount of offending crosstalk that is injected farther back in the plug 116 will now be described.
First, the conductors 101-108 terminate onto both the top and bottom sides of the printed circuit board 150. This allows the conductors 101-108 of different differential pairs to be spaced apart a greater distance along the transverse dimension, which reduces crosstalk between the pairs. Likewise, the conductive paths 161-168 are arranged in pairs that are generally spaced far apart from each other in order to reduce or minimize coupling between the differential transmission lines 171-174 until those transmission lines reach the front section of the printed circuit board 150 underneath the plug blades 141-148.
Additionally, a pair of reflection or “image” planes 130, 130′ are included in the printed circuit board 150. The first image plane 130 is located just below a top surface of the printed circuit board 150, and the second image plane 130′ is located just above a bottom surface of the printed circuit board 150. Each image plane 130, 130′ may be implemented as a conductive layer on the printed circuit board 150. In some embodiments, the image planes 130, 130′ may be grounded or may be electrically floating. The image planes 130, 130′ may act as shielding structures that reduce coupling between the conductive structures on the printed circuit board 150.
Additionally, the back end of plug 116 includes a “crosstail” 190 that spaces the conductor pairs 101, 102; 103, 106; 104, 105; 107, 108 apart from each other in order to reduce coupling between them. Herein, the term “crosstail” refers to a structure that separates each of the four conductor pairs of a cable from the other pairs. Typically, a crosstail separator has four fins that are radially spaced apart by about 90 degrees and that protrude from a center section of the separator. As a result, “crosstail” often has a generally cruciform cross-section. The crosstail 190 (or portions thereof) may be plated with a conductive material or formed of a conductive material in order to enhance its shielding properties.
As shown best in
While in the depicted embodiment the printed circuit board includes the notch 159 to allow the vertically-oriented wall 196 to extend forwardly past the rear edge of printed circuit board 150, it will be appreciated that other designs may be used. For example, in an alternative embodiment, the forward portion of the central core 195 may be omitted (as well as part of the base of the forward portions of fins 191, 192, as necessary, depending upon the thickness of the printed circuit board 150). In this embodiment, the forward portion of fin 191 will be positioned above the top surface of the printed circuit board 150, and the forward portion of fin 192 will be positioned below the bottom surface of printed circuit board 150. This embodiment eliminates any need for the notch 159 in printed circuit board 150 while still providing a first conductive shield that is interposed between the conductors of twisted pairs 111 and 112 at the rear of printed circuit board 150, and a second conductive shield that is interposed between the conductors of twisted pairs 113 and 114 at the rear of printed circuit board 150. In still other embodiments; the first and/or the second conductive shields may be implemented using structures separate from the crosstail. For example, the notch 159 in printed circuit board may be omitted and replaced with metal pads on the top and bottom surfaces of the printed circuit board 150. First and second vertically oriented conductive walls may be soldered onto these metal pads which would act as conductive shields in place of the fins 191 and 192 shown in
The third fin 193 and the fourth fin 194 may each have a widened section 193′, 194′ that is located adjacent the printed circuit board 150 when the plug 116 is fully assembled. In the back part of the crosstail 190, each twisted pair will be tightly twisted. As shown in
The above described conductive shields (e.g., the forward portions of fins 191, 192 or other similar shielding structures) may also facilitate controlling the impedance of the differential transmission lines through the plug 116. As the conductors 101-108 transition from their twisted state within the cable 110 to their untwisted state at their interface with the rear of the printed circuit board 150, the impedance of each twisted pair 111-114 will typically increase. Any shielding that is provided in the cable (e.g., individual shields around each twisted pair 111-114 or a single shield that surrounds all four pairs on the inside of cable jacket 109) will also typically be cut away, and the absence of these shielding structures will also typically act to increase the impedance of each twisted pair 111-114. The same is true with respect to the insulative cores 101b-108b that are stripped from the very end portions of each conductive core 101a-108a of the conductors 101-108. The metalized crosstail 190 or other conductive shields that extend above and/or below the printed circuit board 150 may counteract these effects, and help to reduce or prevent these increases in the impedance of the twisted pairs 111-114.
In some embodiments, the thickness of the printed circuit board 150 may be generally matched to the “pitch” of the conductors 101-108 at the end of the cable 100. The “pitch” of the conductors refers to the vertical distance between (a) the top of the conductive pore of a first of the conductors 101-108 that is terminated into the bottom side of the printed circuit board 150 and (b) the bottom of the conductive core of a second of the conductors 101-108 that is terminated into the top side of the printed circuit board 150 directly above the first conductor. This is illustrated graphically in
As is shown in
Additionally, referring now to
The lossy dielectric material 197 may be, for example, a liquid or foam (e.g., a carbon-loaded foam) that is injected into the plug housing 120 after the plug is assembled. This liquid or foam 197 may fill in much of the empty space within the plug housing 120. The liquid or foam lossy dielectric material 197 may be designed to harden either simply by exposure to air or through a curing process such as, for example, exposure to heat, ultraviolet light, etc. As such, the liquid or foam lossy dielectric material 197 may be injected through any one or more appropriate openings into the interior of the housing (e.g., the back opening 128 and/or other openings (not shown in the figures) that are provided in the housing 120. It may not be necessary to seal these one or more openings after injection of the lossy dielectric material 197 due to the fact that the material 197 hardens into a solid after injection.
In addition to reducing electric field emissions from conductive structures within the plug housing 120, the lossy dielectric material 197 may also help to mechanically secure the various structures into their proper positions within plug 116, thereby providing a more robust plug design. This may be important as any movement of the conductive and/or various of the dielectric structures within plug 116 may significantly impact the electrical performance of the plug 116, as the plug may be designed to generate highly controlled amounts of crosstalk in order to allow for precise cancellation of such offending crosstalk in a mating jack. In some embodiments, the lossy dielectric material 197 may be in the form of a lossy epoxy or other material that has adhesive properties that may not only fill the empty space in the housing 120 but also secure everything within the housing 120 together and to the inside surfaces of the housing 120.
Pursuant to still further embodiments of the present invention, communications plugs such as RJ-45 plugs are provided which include a printed circuit board that is mounted at an oblique angle within the plug housing.
For example,
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In the embodiment of
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In the embodiment of
The communications plugs according to embodiments of the present invention may also include features that may improve the return loss on the differential transmission lines through the plugs. This improved return loss may be achieved, for example, by generating inductive and/or capacitive self-coupling along the differential transmission lines. This self-coupling may help counteract the loads placed on the differential transmission lines by the high levels of crosstalk compensation that may be necessary to counteract the offending crosstalk (particularly for high frequency signals), and hence may provide improved return loss on the transmission lines.
For example, in U.S. Pat. No. 7,264,516, issued Sep. 4, 2007, the entire contents of which are incorporated herein by reference, teaches arranging printed circuit board coupling sections of the two conductive paths of a differential transmission line of a communications connector such that they are immediately adjacent each other and such that they follow substantially parallel paths having the same instantaneous current directions. By judicious selection of the portions of the two conductive paths that are immediately adjacent each other with substantially identical instantaneous current directions it may be possible to control the input impedance of a differential transmission line through a mated plug jack combination, and, consequently, it may be possible to control the return loss of the differential transmission line. As a result, the jack of the mated plug-jack combination can withstand the increased crosstalk compensation that may be necessary to achieve, in a mated plug jack combination, elevated frequency signal transmission while still experiencing acceptable levels of return loss.
Pursuant to embodiments of the present invention, communications plugs are provided that implement the teachings of the above-referenced U.S. Pat. No. 7,264,516. For example, as shown in
Moreover, since the coupling portions of conductive paths 361, 362 are implemented on opposite sides of the flexible printed circuit board 350, these portions of conductive paths 361, 362 will not only inductively couple, but may also experience significant capacitive coupling, given the thin nature of the dielectric layer of the flexible printed circuit board 350. This is particularly true if the coupling portions of conductive paths 361, 362 are widened as shown in
By generating both inductive coupling and capacitive coupling along the differential transmission line 372 it may be possible to provide a significant improvement in the return loss of the differential transmission line. It may be difficult, in some instances, to provide return loss improvement across an extended frequency range by generating only or mostly inductive coupling. In some embodiments, the amount of capacitive coupling generated between conductive paths 361, 362 may be at least half the amount of the inductive coupling.
Moreover, pursuant to some embodiments of the present invention, the ratio of the amount of capacitive coupling between the two conductive paths of a differential transmission line to the amount of inductive coupling between the two conductive paths of the differential transmission line may be tuned to improve the return loss of the differential transmission line. In particular, it has been discovered that by generating both inductive coupling and capacitive coupling along a differential transmission line that resonances may be created. By adjusting the relative amount of capacitive coupling to the amount of inductive coupling these resonances may be tuned so as to create a local maximum in the return loss spectrum for the differential transmission line. For example,
While
As shown in
In addition, the arrangement of the trace sections 461a, 461b that are depicted in
It will be appreciated that the techniques for adjusting the relative amounts of capacitive and inductive coupling that are discussed above with respect to
Pursuant to still further embodiments of the present invention, crosstalk compensation circuits are provided that are implemented on flexible printed circuit boards in order to achieve high amounts of crosstalk compensation with very short coupling sections. As discussed above, the dielectric layers on flexible printed circuit boards may be very thin (e.g., 1 mil). This allows for significant amounts of coupling between overlapping traces that are implemented on either side if the flexible printed circuit board. As inductive crosstalk compensation requires current flow, it necessarily is spread out in time. When crosstalk compensation is spread over time, it necessarily involves an associated delay. With all things being equal, improved crosstalk compensation may generally be provided with a shorter delay, as the ability to introduce large amounts of inductive crosstalk compensation within very short trace segments may be desirable. Communications plugs that implement this technique are provided pursuant to further embodiments of the present invention.
In particular,
In particular, as shown in
As is further shown in
As shown in
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. 15/009,853, filed Jan. 29, 2016, which in turn is a continuation of U.S. patent application Ser. No. 14/522,663, filed Oct. 24, 2014, which in turn is a divisional application of U.S. patent application Ser. No. 13/802,856, filed Mar. 14, 2013. The entire content of all of these applications is incorporated herein by reference as if set forth fully herein.
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| Number | Date | Country | |
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| Child | 15009853 | US |
