Patent Application
20170018881
The subject matter herein relates generally to pluggable electrical connectors that have signal pathways configured to convey data signals and ground pathways that reduce crosstalk between the signal pathways.
Communication systems exist today that utilize pluggable cable assemblies to transmit data. For example, network systems, servers, data centers, and the like may use numerous cable assemblies to interconnect the various devices of the communication system. Cable assemblies may include a pluggable electrical connector (referred to herein as pluggable connector) that is configured to be inserted into a receptacle assembly of a communication system. The pluggable connector includes signal pathways and ground pathways in which the signal pathways convey data signals and the ground pathways control impedance and reduce crosstalk between the signal conductors. In differential signaling applications, the signal pathways are arranged in signal pairs for carrying the data signals. Each signal pair may be separated from an adjacent signal pair by one or more ground pathways.
The pluggable connectors may be configured to transfer electrical signals in accordance with industry standards. By way of example, known industry standards for pluggable connectors include small-form factor pluggable (SFP), enhanced SFP (SFP+), quad SFP (QSFP), C form-factor pluggable (CFP), and 10 Gigabit SFP, which is often referred to as XFP. Among other things, these standards may require that the pluggable connectors have certain physical configurations or structures.
There has been a general demand to increase the speeds at which data is transmitted through the communication systems. As data rates increase, however, it becomes more challenging to maintain a baseline level of signal quality. For example, electrical energy that flows along the surface of each ground pathway may form a field that propagates between the ground pathways. The ground pathways may couple with each other to support an unwanted electrical propagation mode that is repeatedly reflected and forms a resonating condition (or standing wave). Electrical noise caused by the resonating condition may increase return loss and/or crosstalk and reduce throughput of the interconnection system.
To control resonance between ground pathways and limit the effects of the resulting electrical noise, it has been proposed to electrically common the ground pathways using a metal conductor or a lossy plastic material. The effectiveness and/or cost of implementing these techniques is based on a number of variables, such as the geometries of the signal and ground pathways within the interconnection system. Moreover, these techniques are usually applied to the receptacle assembly that receives the pluggable connector. It may be difficult to implement these and other techniques in pluggable connectors due to the structural requirements for pluggable connectors that are set by the industry standards.
Accordingly, there is a need for pluggable connectors that reduce the electrical noise caused by resonating conditions in ground pathways.
In an embodiment, a pluggable connector is provided that includes a plug housing configured to couple to a communication cable. The plug housing has a plug cavity. The pluggable connector also includes a module board that is disposed within the plug cavity and configured to be communicatively coupled to the communication cable. The module board has a mating edge configured to interface with a mating connector. The module board includes a plurality of signal pathways and a plurality of ground pathways in which the signal pathways are interleaved between corresponding ground pathways. The signal and ground pathways include respective contact pads that are disposed proximate to the mating edge for engaging corresponding contacts of the mating connector. Each of the ground pathways has separate first and second trace segments and a damping component that electrically joins the first and second trace segments. In an exemplary embodiment, the damping component includes one or more resistors. In some embodiments, the damping component may be a capacitor or inductor or, in other embodiments, may be a plurality of interconnected resistors, capacitors, and/or inductors.
In an embodiment, an interconnection system is provided that includes a receptacle connector configured to be mounted to a circuit board. The receptacle connector having a front side and a receiving cavity that opens to the front side. The receptacle connector includes an array of electrical contacts disposed within the receiving cavity that are configured to be terminated to the circuit board. The interconnection system also includes a pluggable connector that is configured to be inserted into the receiving cavity of the receptacle connector during a mating operation. The pluggable connector includes a module board having a plurality of signal pathways and a plurality of ground pathways in which the signal pathways are interleaved between corresponding ground pathways. The signal and ground pathways include respective contact pads that are disposed proximate to a mating edge of the module board for engaging corresponding electrical contacts of the receptacle connector. Each of the ground pathways has separate first and second trace segments and a damping component that electrically joins the first and second trace segments.
Embodiments set forth herein may include various pluggable electrical connectors (referred to herein as pluggable connectors) that are configured for communicating data signals. Embodiments may also include cable assemblies or interconnection systems that include the pluggable connectors. The pluggable connectors are configured to mate with a corresponding mating connector, such as a receptacle connector. Various embodiments are particularly suitable for high-speed communication systems, such as network systems, servers, data centers, and the like, in which the data rates may be greater than four (4) gigabits/second (Gbps). Particular embodiments may be capable of transmitting data at a rate of at least about 10 Gbps, at least about 20 Gbps, at least about 28 Gbps, at least about 56 Gbps, or more. However, it is also contemplated that embodiments may transmit at slower transmission speeds or data rates.
Embodiments include conductive pathways that may include one or more interconnected conductive elements, such as traces and vias. The conductive pathways include signal and ground pathways that are positioned relative to each other to form a designated pattern that is suitable for communicating data signals at the desired data rate. In particular embodiments, the signal pathways form signal pairs in which each signal pair is flanked on both sides by ground pathways. The ground pathways electrically separate the signal pairs to reduce electromagnetic interference or crosstalk and to provide a reliable ground return path. Other embodiments, however, may not include signal pairs. For example, each signal pathway may be flanked on both sides by ground pathways.
For embodiments that include signal pairs, the signal and ground pathways may form multiple sub-arrays. Each sub-array includes, in order, a ground pathway, a signal pathway, a signal pathway, and a ground pathway. This arrangement is referred to as ground-signal-signal-ground (or GSSG) sub-array. The sub-array may be repeated such that an exemplary row of conductors may form G-S-S-G-G-S-S-G-G-S-S-G, wherein two ground pathways are positioned between two adjacent signal pairs. In the illustrated embodiment, however, adjacent signal pairs share a ground conductor such that the pattern forms G-S-S-G-S-S-G-S-S-G. In both examples above, the sub-array may be referred to as a GSSG sub-array. More specifically, the term “GSSG sub-array” includes sub-arrays that share one or more intervening ground conductors.
The cable assembly 100 and pluggable connector 102 may be configured for various applications. Non-limiting examples of such applications include host bus adapters (HBAs), redundant arrays of inexpensive disks (RAIDs), workstations, servers, storage racks, high performance computers, or switches. The cable assembly 100 may be configured to be compliant with industry standards, such as, but not limited to, the small-form factor pluggable (SFP) standard, enhanced SFP (SFP+) standard, quad SFP (QSFP) standard, C form-factor pluggable (CFP) standard, and 10 Gigabit SFP standard, which is often referred to as the XFP standard.
The communication cable 112 is configured to transfer data signals to and/or from a contact array 114 of the pluggable connector 102 that is disposed proximate to the mating end 106. The communication cable 112 may be permanently attached to the pluggable connector 102 or separably attached to the pluggable connector 102.
The pluggable connector 102 includes a plug housing 104 that is configured to be directly or indirectly coupled to the communication cable 112. In the illustrated embodiment, the pluggable connector 102 also includes an optional electromagnetic interference (EMI) skirt 120 that is coupled to the plug housing 104. The EMI skirt 120 may be removed in other embodiments. The plug housing 104 includes a connector base 115 and a plug extension 105 that extends from the connector base 115 along the central axis 110.
The connector base 115 represents a portion of the plug housing 104 that is not inserted into the receptacle assembly 200 (
The EMI skirt 120 includes spring beams 195 that are positioned adjacent to the plug extension 105 and proximate to the connector base 115. In other embodiments, the spring beams 195 may be positioned away from the connector base 115. The spring beams 195 are configured to directly engage the plug extension 105 and the receptacle assembly 200 (
The module board 116 has the contact array 114 proximate to a mating edge 118 of the module board 116. The plug housing 104 is configured to surround at least a portion of the module board 116 and other circuitry of the pluggable connector 102 to contain the EMI emissions generated. The plug housing 104 may be conductive and may surround the module board 116 and other internal circuitry about the central axis 110. The EMI skirt 120 surrounds the plug extension 105 and is also configured to contain the EMI emissions generated by the pluggable connector 102.
The module board 116 includes a trailing edge 126 that also includes a contact array 128. The trailing edge 126 and the mating edge 118 are located on opposite ends of the module board 116. The contact arrays 114, 128 are communicatively coupled to each other by conductive pathways (not shown) extending through the module board 116. The contact arrays 114, 128 include electrical contacts 130, 131, respectively, which are contact pads in an exemplary embodiment. The electrical contacts 130 may be referred to as mating pads, and the electrical contacts 131 may be referred to as terminating pads. The module board 116 also includes a pair of side edges 132, 134 that face in opposite directions. Each of the side edges 132, 134 forms a corresponding recess 136.
In an exemplary embodiment, the communication cable 112 (
When the pluggable connector 102 is assembled, the module board 116 is positioned between the housing shells 122, 124 and the housing shells 122, 124 are joined to each other. The housing shell 122 includes side portions 140, 142 and a plug side 171 that extends between and joins the side portions 140, 142. The housing shell 122 includes a base portion 146. The plug side 171 and the side portions 140, 142 project from the base portion 146 along the central axis 110. Similarly, the housing shell 124 includes side portions 150, 152 and a plug side 173 that extends between and joins the side portions 150, 152. The housing shell 124 includes a base portion 156. The plug side 173 and the side portions 150, 152 project from the base portion 156 along the central axis 110.
The housing shells 122, 124 form the plug housing 104 when joined together with the module board 116 at least partially therebetween. In the illustrated embodiment, the plug sides 171, 173 and the side portions 140, 142, 150, 152 collectively form the plug extension 105 (
The EMI skirt 120 defines a connector-receiving opening 186 and a plug-receiving opening 188. The plug passage 190 extends between the connector-receiving and plug-receiving openings 186, 188. The EMI skirt 120 defines a front edge 192 that is configured to be inserted into the receptacle assembly 200 (
Also shown in
The receptacle cage 210 has a cage edge 220 that defines a port or opening 218 that provides access to the receiving cavity 212. The cage edge 220 may engage the spring beams 195 (
The module board 300 includes a board body 302 having board edges 304, 305 (shown in
The module board 300 may be manufactured through a variety of fabrication technologies. For example, the module board 300 may be manufactured through printed circuit board (PCB) technologies. The module board 300 may be a laminate or sandwich structure that includes a plurality of stacked substrate layers having conductive elements that extend between the substrate layers (e.g., traces, ground planes, and the like) or extend through the substrate layers (e.g., vias, plated thru-holes, and the like). By way of example, the substrate layers may include a dielectric material (e.g., flame-retardant epoxy-woven glass board (FR4), FR408, polyimide, polyimide glass, polyester, epoxy-aramid, metals, and the like). The substrate layers may also include a bonding material (e.g., acrylic adhesive, modified epoxy, phenolic butyral, pressure-sensitive adhesive (PSA), preimpregnated material, and the like). The conductive elements may be disposed, deposited, or etched in a predetermined manner within or along the substrate layers. By way of example, the conductive elements may comprise copper (or a copper-alloy), cupro-nickel, silver epoxy, and the like. In alternative embodiments, the module board 300 may constitute a lead frame having conductive elements deposited within a dielectric body formed through, for example, injection molding.
The following is with specific reference to features along the board surface 310. It should be understood that the description may also be applied to the board surface 312. The module board 300 includes a plurality of signal pathways 320 and a plurality of ground pathways 322. Each signal pathway 320 includes a signal trace 326, and each ground pathway 322 includes first and second trace segments 328, 330. The signal and ground pathways 320, 322 extend generally parallel to one another and parallel to the Z-axis. At least portions of the signal and ground pathways 320, 322 are coplanar and are exposed along the board surface 310.
The signal pathways 320 are interleaved between corresponding ground pathways 322. In the illustrated embodiment, the signal pathways 320 are configured for differential signaling such that the signal pathways 320 are arranged to form signal pairs 324. Each signal pair 324 includes two signal pathways 320, which are specifically designated as 320A, 320B, that extend immediately adjacent to each other without conductive elements therebetween. Each signal pair 324 is flanked by two of the ground pathways 322. In other embodiments, however, each signal pathway 320 may be flanked by two of the ground pathways 322 such that the signal pathways 320 do not extend immediately adjacent to each other. In other embodiments, more than one ground pathway 322 may exist between two of the signal pairs 324.
Each of the signal pathways 320 includes a contact pad (or mating pad) 331 that is located proximate to the mating edge 304 for engaging a corresponding electrical contact 413 (shown in
Each of the first and second trace segments 328, 330 forms a corresponding portion of a ground pathway 322. The first and second trace segments 328, 330 include trace ends 338, 340, respectively, that are spaced from each other by a gap 342. As described herein, the ground pathways 322 also include damping (or resonance-control) components 344 that extend across the gap 342 and electrically couple the first and second trace segments 328, 330. As described herein, the damping components 344 may impede the formation of standing waves (or resonating conditions) at certain frequencies. In an exemplary embodiment, the damping component 344 includes a single resistor. However, in other embodiments, the damping component 344 may include one or more interconnected resistors, capacitors, or inductors. The second trace segment 330 extends between the trace end 340 and a ground via 370 that extends into the board body 302.
In the illustrated embodiment, the module board 300 is shaped along the mating edge 304 for engaging and deflecting electrical contacts 413, 415 (shown in
Each insulated wire 354 includes an insulation layer 356 and a wire conductor 358 that is surrounded by the corresponding insulation layer 356. The insulation layers 356 may be stripped to expose the corresponding wire conductors 358 for terminating to the module board 300. Although the wire conductors 358 appear to be terminated to the ground pathways 322 in
The first and second trace segments 328, 330 are spaced apart by the gap 342. In some embodiments, the damping component 344 is a discrete resistor that may be positioned across or within the gap 342. For example, after the board surface 310 is fabricated (e.g., etched, polished), the damping resistor 344 may be positioned onto the board surface 310. The damping resistor 344 may be an off-the-shelf resistor having a designated resistance, such as 50 Ohm. It is contemplated, however, that the damping resistor 344 may be fabricated during the manufacture of the module board 300. For example, in other embodiments, the damping resistor 344 may comprise a lossy plastic material that is deposited along the board surface 310. Furthermore, although the ground pathway 322 has only a single damping resistor 344, other embodiments may include a series of damping resistors 344. In other embodiments, the damping component 344 may include a capacitor or inductor that is discrete and/or provided through the manufacturing of the module board 300.
In
In
The ground via 370 extends a depth 372 into the board body 302 to electrically couple to one of the ground planes 374. Each of the ground pathways 322 along the board surface 310 may be electrically coupled to a common ground plane 374 such that the ground pathways 322 along the board surface 310 are electrically common. Each of the ground pathways 322 has an electrical path length 376 that extends approximately between the ground via 370 and the corresponding contact pad 332. In some embodiments, a majority of the ground pathway 322 is linear along the electrical path length 376 such that the electrical path length 376 may be measured along the Z-axis. The electrical path length 376 includes the depth 372, but the depth 372 is nominal in the illustrated embodiment.
The damping component 344 may have a designated location along the electrical path length 376 that is configured to impede formation of a standing wave or resonating condition. In
Accordingly, the predetermined distance 378 may be configured to satisfy an industry standard and also to achieve a designated electrical performance. In some embodiments, the predetermined distance 378 causes the damping component 344 to be closer to the ground plane 374 than the contact pad 332. In particular embodiments, the predetermined distance 378 causes the damping component 344 to be within one-third of the electrical path length 376 from the ground plane 374. In more particular embodiments, the predetermined distance 378 causes the damping component 344 to be within one-fifth of the electrical path length 376 from the ground plane 374.
As such, the damping component 394 electrically joins the first and second trace segments 384, 386. In the illustrated embodiment, the damping component 394 is only partially disposed within the component recess 392 such that the damping component 394 clears the board surface 390. In other embodiments, a top of the damping component 394 may be flush or level with the board surface 390 or located a depth within the component recess 392.
The receptacle connector 402 includes an inner housing 406 and an outer housing 408 (shown in phantom) that surrounds the inner housing 406. The receptacle connector 402 has a front side 420 that is defined by the outer housing 408. The outer housing 408 includes a receiving cavity 422 that opens to the front side 420. The receiving cavity 422 has a first array 412 of electrical contacts 413 and a second array 414 of electrical contacts 415 disposed therein. As shown, the electrical contacts 413, 415 extend through the inner housing 406 and through a back side 432 of the inner housing 406. The electrical contacts 413, 415 are terminated to the circuit board 404.
The electrical contacts 413 of the first array 412 are configured to engage the board surface 310 of the module board 300, and the electrical contacts 415 of the second array 414 are configured to engage the board surface 312. Each of the electrical contacts 413, 415 has a contact interface 416 that is configured to engage the module board 300 within the receiving cavity 422. Each of the electrical contacts 413, 415 has an end portion 418 that is terminated to the circuit board 404.
A pluggable connector, such as the pluggable connector 102 (
During operation of the interconnection system 400, data signals are transmitted through the signal pathways 320 and electrical energy flows along the surface of each ground pathway 322. The electrical energy flowing along the ground pathways 322 may form a field that propagates between the ground pathways 322. Without the damping components 344, the field may reflect and form a standing wave (or resonating condition) at certain frequencies. The field may reflect, for example, between the ground planes 374 of the module board 300 and ground planes 430 of the circuit board 404. The damping components 344 are configured to impede the development of these standing waves (or resonating conditions) at certain frequencies and, consequently, reduce the unwanted effects of the electrical noise. For example, in some embodiments, the damping components 344 may absorb some of the electrical energy and drain the electrical energy. In some embodiments, the damping components 344 effectively change or dampen the reflections such that the standing wave (or the resonating condition) is not formed during operation of the interconnection system 400.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Moreover, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The patentable scope should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
As used in the description, the phrase “in an exemplary embodiment” and the like means that the described embodiment is just one example. The phrase is not intended to limit the inventive subject matter to that embodiment. Other embodiments of the inventive subject matter may not include the recited feature or structure. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” An element recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements, unless such exclusion is explicitly stated. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
