Patent Publication Number: US-9425556-B1

Title: Interconnection system and an electrical connector having resonance control

Description:
BACKGROUND 
     The subject matter herein relates generally to electrical connectors that have signal conductors configured to convey data signals and ground conductors that control impedance and reduce crosstalk between the signal conductors. 
     Communication systems exist today that utilize electrical connectors to transmit data. For example, network systems, servers, data centers, and the like may use numerous electrical connectors to interconnect the various devices of the communication system. Many electrical connectors include signal conductors that convey data signals and ground conductors that provide a return path for current. The ground conductors may also be used to reduce crosstalk between the signal conductors and control impedance. In differential signaling applications, the signal conductors 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 conductors. 
     There has been a general demand to increase the density of signal conductors within the electrical connectors and/or increase the speeds at which data is transmitted through the electrical connectors. As data rates increase and/or distances between the signal conductors decrease, however, it becomes more challenging to maintain a baseline level of signal integrity. For example, in some cases, electrical energy that flows on the surface of each ground conductor of the electrical connector may be reflected and resonate within cavities formed between ground conductors. Unwanted electrical energy may be supported between one ground conductor and nearby ground conductors. Depending on the frequency of the data transmission, electrical noise may develop that increases return loss and/or crosstalk and reduces throughput of the electrical connector. 
     To control resonance between conductors and limit the effects of the resulting electrical noise, it has been proposed to electrically common separate ground conductors 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 geometry of the electrical connector and geometries of the signal and ground conductors within the electrical connector. For some applications and/or electrical connector configurations, alternative methods for controlling resonance between the ground conductors may be desired. 
     Accordingly, there is a need for electrical connectors that reduce the electrical noise caused by resonating conditions between ground conductors. 
     BRIEF DESCRIPTION 
     In an embodiment, an interconnection system is provided that includes a mating connector having a plurality of terminal sub-assemblies. Each of the terminal sub-assemblies includes a signal terminal and a ground shield that is proximate to the signal terminal to shield the signal terminal from other terminal sub-assemblies. The interconnection system also includes an electrical connector having a plurality of contact sub-assemblies that each include a signal contact and a resonance-control shield that is proximate to the signal contact of the corresponding contact sub-assembly. The terminal sub-assemblies of the mating connector engage corresponding contact sub-assemblies of the electrical connector when the mating and electrical connectors are mated. The signal terminals of the terminal sub-assemblies engage the signal contacts of the corresponding contact sub-assemblies. Each of the ground shields of the terminal sub-assemblies is inserted between the resonance-control shield and the signal contact of the corresponding contact sub-assembly. The ground shield and the resonance-control shield have respective broad surfaces that face each other with a capacitive gap therebetween. 
     In some aspects, each of the resonance-control shields includes a spring member that engages the corresponding ground shield at a contact zone such that current is permitted to flow through the contact zone. 
     In some aspects, each of the ground shields includes a stub portion that is exposed to an exterior of the mating connector when the electrical connector and mating connector are unmated. The stub portion has the broad surface of the ground shield. Optionally, a majority of the broad surface of the ground shield overlaps with the broad surface of the corresponding resonance-control shield. Optionally, a majority of the broad surface of the resonance-control shield overlaps with the broad surface of the ground shield. Optionally, the broad surface of the ground shield and the broad surface of the resonance-control shield overlap each other by least 5 mm 2 . Optionally, the capacitive gap is at most 0.40 mm. 
     In an embodiment, an electrical connector is provided that includes a connector housing having a front side configured to engage a mating connector. The connector housing includes a plurality of contact cavities having cavity openings along the front side. The electrical connector also includes a plurality of contact sub-assemblies that are positioned within corresponding contact cavities. Each of the contact sub-assemblies includes a signal contact and a resonance-control shield that is proximate to the signal contact of the corresponding contact sub-assembly. The signal contacts are configured to engage respective signal terminals of a mating connector during a mating operation between the electrical connector and the mating connector. Each of the contact cavities and the contact sub-assembly within the corresponding contact cavity are configured to permit an associated ground shield of the mating connector to be inserted between the signal contact and the resonance-control shield of the contact sub-assembly during the mating operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an interconnection system formed in accordance with an embodiment that includes a mating connector and an electrical connector that are mated with each other. 
         FIG. 2  is a partially exploded view of an electrical connector formed in accordance with an embodiment. 
         FIG. 3  is a front perspective view of the mating connector of  FIG. 1 . 
         FIG. 4  is a perspective view of a resonance-control shield in accordance with an embodiment that may be used with the electrical connector of  FIG. 1 . 
         FIG. 5  is a side view of the resonance-control shield of  FIG. 4 . 
         FIG. 6  is a plan view of a portion of a front side of the electrical connector of  FIG. 1 . 
         FIG. 7  is a cross-section of the electrical connector of  FIG. 1  showing resonance-control shields disposed within respective contact cavities. 
         FIG. 8  is a cross-section of a portion of the interconnection system after the mating connector and the electrical connector have been mated. 
         FIG. 9  is an end view of a plurality of ground shields of the mating connector mated with corresponding resonance-control shields of the electrical connector. For illustrative purposes, other components of the mating and electrical connectors have been removed. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments set forth herein may include interconnection systems and electrical connectors that are configured for communicating data signals. An interconnection system may include at least two electrical connectors in which one electrical connector may mate with another electrical connector, which is hereinafter referred to as a mating connector. In some embodiments, the electrical connector is a receptacle connector of a backplane or midplane interconnection system. In other embodiments, the electrical connector may be a header connector that is configured to mate with a receptacle connector of a backplane or midplane interconnection system. However, the inventive subject matter set forth herein is not limited to backplane or midplane interconnection systems and may be applicable to other types of electrical connectors and systems. 
     The electrical connectors typically include a plurality of signal conductors and a plurality of ground conductors. In order to distinguish similar elements in the detailed description and claims, various labels may be used. For example, a signal conductor may be referred to as a signal contact, a signal terminal, etc. A signal conductor is configured to convey data signals. A ground conductor may be referred to as a ground shield, a resonance-control shield, etc., and may provide a ground or return path for the electrical connector. It should be understood that two similar elements having different labels do not necessarily have different structures. It should also be understood that two elements having the same label may have different structures. For example, one or more ground shields may be C-shape or L-shaped and one or more other ground shields may be blade-shaped. 
     Embodiments include resonance-control shields that engage and/or capacitively couple to ground shields of a mating connector. The resonance-control shields of an electrical connector are configured to directly interface with the corresponding ground shield of a mating connector. As used herein, a resonance-control shield “directly interfaces with” a corresponding ground shield if the resonance-control shield and the ground shield have respective broad surfaces that face each other with a capacitive gap therebetween. As used herein, a “broad surface” provides a non-negligible amount of surface area. For example, resonance-control shields and the ground shields may be formed (e.g., stamped-and-formed, 3D printed, and the like) to include edges and broad surfaces that extend between edges. The broad surface of the resonance-control shield and the broad surface of the ground shield may face each other with a small gap therebetween such that the broad surfaces capacitively couple to each other. In some embodiments, the capacitively coupled shields may facilitate controlling or impeding resonating conditions that may develop between ground shields. The surface areas along edges, however, may be small such that any capacitive coupling between only two edges may be insubstantial or negligible. It should be understood that the resonance-control shield and the ground shield may, optionally, engage each other through one or more contact points. 
     The signal conductors and ground shields are positioned relative to each other to form a predetermined array or pattern. In some embodiments, the pattern or array includes multiple rows and/or columns. The signal conductors of a single row or column may be substantially co-planar. The ground shields of a single row or column may be substantially co-planar. In an exemplary embodiment, the signal conductors form signal pairs in which each signal pair is separated from an adjacent signal pair by one or more ground shields. As used herein, the phrase “adjacent signal conductors” means first and second signal conductors that do not have any other signal conductors positioned between the first and second signal conductors. Likewise, as used herein, the phrase “adjacent signal pairs” means first and second signal pairs that do not have any other signal pairs positioned between the first and second signal pairs. It should be understood, however, that a single signal pair may be adjacent to more than one signal pair. For instance, the single signal pair may be positioned between two other signal pairs. In this example, the signal pair is adjacent to the signal pair on one side and adjacent to the signal pair on the opposite side. 
     The ground shields and resonance-control shields may be positioned between adjacent signal conductors (or signal pairs) to electrically separate the signal conductors (or signal pairs) and reduce electromagnetic interference or crosstalk. As used herein, a shield, such as a ground shield or a resonance-control shield, is “positioned between” adjacent signal conductors or pairs if at least a portion of the shield is positioned between the adjacent signal conductors or pairs. The shield is positioned between the adjacent signal conductors or signal pairs if a line extending between the adjacent signal conductors or pairs intersects the shield. 
     In some embodiments, a single ground shield (or single resonance-control shield) may be shaped to at least partially surround a corresponding signal conductor or corresponding signal pair. For example, the ground shield may include multiple shield walls that are positioned to provide the ground shield with a U-shape, C-shape, L-shape, or rectangular shape structure. The ground shield may also have a V-shape, I-shape, or X-shape. In other embodiments, multiple ground shields may be positioned to at least partially surround a corresponding signal conductor or corresponding signal pair. For example, multiple ground blades may be positioned to at least partially surround a corresponding signal conductor or corresponding signal pair. The resonance-control shields may also have shapes similar to the ground shields described herein. As described herein, the resonance-control shield may also extend along or around a corresponding ground shield. In some embodiments, a ground shield may be nested within a corresponding resonance-control shield. 
     As used herein, the phrases “a plurality of [elements],” “an array of [elements],” and the like, when used in the detailed description and claims, do not necessarily include each and every element that a component, such as an electrical connector or interconnection system, may have. For instance, the phrase “a plurality of ground shields having [a recited feature]” does not necessarily mean that each and every ground shield of the corresponding mating connector (or interconnection system) has the recited feature. Other ground shields of the mating connector may not include the recited feature. As another example, the claims may recite that an electrical connector includes “a plurality of resonance-control shields, each of which including a spring member.” This phrase does not exclude the possibility that other resonance-control shields of the electrical connector may not have a spring member. Accordingly, unless explicitly stated otherwise (e.g., “each and every resonance-control shield of the electrical connector”), embodiments may include similar elements that do not have the recited features. 
       FIG. 1  is a perspective view of an interconnection system  100  formed in accordance with an embodiment. The interconnection system  100  includes a first circuit board assembly  102  and a second circuit board assembly  104  that are communicatively coupled to one another. The first circuit board assembly  102  includes a circuit board  106  and an electrical connector  108  mounted thereto. The second circuit board assembly  104  includes a circuit board  110  and an electrical connector  112  mounted thereto. In particular embodiments, the interconnection system  100  may be a backplane or midplane interconnection system such that the first circuit board assembly  102  forms a backplane or midplane assembly, and the second circuit board assembly  104  forms a daughter card assembly. The daughter card assembly may be referred to as a line card or a switch card. The electrical connectors  108 ,  112  may be referred to as header and receptacle connectors, respectively, in some embodiments. 
     The electrical connector  108 ,  112  are configured to mate with each other during a mating operation. As such, either of the electrical connectors  108 ,  112  may be referred to as a mating connector. In the illustrated embodiment, only a single electrical connector  108  is shown mounted to the circuit board  106  and only a single electrical connector  112  is shown mounted to the circuit board  110 . In other embodiments, however, the first circuit board assembly  102  may include multiple electrical connectors  108 , and the second circuit board assembly  104  may include multiple electrical connectors  112 . 
     The interconnection system  100  may be used in various applications that utilize ground conductors for controlling impedance and reducing crosstalk between signal conductors. By way of example only, the interconnection system  100  may be used in telecom and computer applications, routers, servers, and supercomputers. One or more of the electrical connectors described herein may be similar to electrical connectors of the STRADA Whisper or Z-PACK TinMan product lines developed by TE Connectivity. The electrical connectors may be capable of transmitting data signals at high speeds, such as 5 gigabits per second (Gb/s), 10 Gb/s, 20 Gb/s, 30 Gb/s, or more. In more particular embodiments, the electrical connectors may be capable of transmitting data signals at 40 Gb/s, 50 Gb/s, or more. 
     The interconnection system, electrical connector, and mating connector may include high-density arrays of signal pathways or contacts. For example, the electrical connector may include a high-density array of signal contacts, and the mating connector may include a high-density array of signal contacts (referred to as signal terminals). The signal terminals of the mating connector may engage the signal contacts of the electrical connector to form a high-density array of signal pathways of the interconnection system. A high-density array of signal contacts may have, for example, at least 12 signal contacts per 100 mm 2  along a front side of the electrical connector. In more particular embodiments, the high-density array may have at least 20 signal contacts per 100 mm 2  along the front side of the electrical connector. 
     As shown in  FIG. 1 , the interconnection system  100  is oriented with respect to mutually perpendicular axes  191 ,  192 ,  193 , including a mating axis  191 , a first lateral axis  192 , and a second lateral axis  193 . It should be understood that the interconnection system  100  may have any orientation with respect to gravity. For example, the first lateral axis  192  may extend parallel to a gravitational force direction in some embodiments, or the mating axis  191  may extend parallel to the gravitational force direction in other embodiments. 
     The electrical connector  112  includes a connector body  114  having a front side  116  that is configured to engage the electrical connector  108  and a mounting side  118  that is configured to engage an electrical component, which is the circuit board  110  in  FIG. 1 . In other embodiments, however, the mounting side  118  may engage another electrical component, such as another electrical connector or a communication device that is capable of electrically coupling to the electrical connector  112 . 
     The connector body  114  may be a single physical structure or a plurality of discrete structures that are assembled together to form a unitary structure. For example, in the illustrated embodiment, the connector body  114  includes a connector housing or shroud  120  and a plurality of connector sub-modules  122 . The electrical connector  112  includes eight (8) connector sub-modules  122  in the illustrated embodiment, but may include fewer or more connector sub-modules in other embodiments. As shown, the connector sub-modules  122  are stacked side-by-side along the second lateral axis  193 . The connector housing  120  is secured to the stacked connector sub-modules  122  to hold the connector sub-modules  122  as a group. In the illustrated embodiment, the connector housing  120  comprises a single continuous piece of dielectric material that is, for example, molded to include the features shown and described herein. 
     In the illustrated embodiment, the mounting side  118  faces along the first lateral axis  192 , and the front side  116  faces along the mating axis  191 . As such, the electrical connector  112  may be referred to as a right-angle connector. In other embodiments, the mounting side  118  and the front side  116  may face in opposite directions along the mating axis  191 . In such embodiments, the electrical connector  112  may be referred to as a vertical connector. Collectively, the connector sub-modules  122  form the mounting side  118 . In alternative embodiments, the electrical connector  112  does not include multiple connector sub-modules. Instead, the electrical connector  112  may include only a single module body that is coupled to the connector housing  120 . Yet in other embodiments, the electrical connector  112  does not include the connector housing  120 . 
     The electrical connector  108  includes a connector body or housing  124  having a front side  126  configured to engage the electrical connector  112  and a mounting side  128  configured to engage an electrical component, which is the circuit board  106  in  FIG. 1 . In other embodiments, however, the mounting side  128  may engage another electrical component, such as another electrical connector or a communication device that is capable of electrically coupling to the electrical connector  108 . In the illustrated embodiment, the connector body  124  comprises a single continuous piece of dielectric material that is, for example, molded to include the features illustrated and described herein. In other embodiments, the connector body  124  may be similar to the connector body  114  and include multiple discrete structures that are coupled to one another. 
       FIG. 2  is a partially exploded view of a circuit board assembly  130 . The second circuit board assembly  104  ( FIG. 1 ) may be similar to the circuit board assembly  130  and include the same or similar components. The circuit board assembly  130  includes an electrical connector  132  having a plurality of connector sub-modules  134 , which may be similar or identical to the connector sub-modules  122  ( FIG. 1 ). The connector sub-modules  134  are received within a connector housing  136 . The connector housing  136  may be manufactured from a dielectric material, such as a plastic material. The connector housing  136  has a front side  142  and a plurality of cavity openings  138 ,  140  along the front side  142 . The cavity openings  138 ,  140  may provide access to separate contact cavities (not shown) or a single contact cavity (not shown), such as the contact cavity  301  (shown in  FIG. 6 ). The front side  142  defines a mating interface of the electrical connector  132  that engages another electrical connector, such as the electrical connector  108  ( FIG. 1 ). Also shown, the electrical connector  132  includes a mounting side  144  that is mounted onto a circuit board  146 . 
       FIG. 2  illustrates one of the connector sub-modules  134  in an exploded state. The connector sub-module  134  includes a plurality of signal conductors  150 . Each signal conductor  150  extends between a mounting contact  166  and a signal contact  152 , which is represented by two opposing contact beams. The signal contact  152  may be positioned adjacent to another single signal contact  152  that is also formed from two opposing contact beams. The two adjacent signal contacts  152  are hereinafter referred to as a signal pair  151 . 
     Each connector sub-module  134  includes a column of signal pairs  151 . The connector sub-module  134  also includes a connector shield  153  and a plurality of resonance-control shields  155 . Optionally, the resonance-control shields  155  may mechanically and electrically couple to the connector shield  153 . In  FIG. 2 , only one resonance-control shield  155  is shown, but it should be understood that the connector sub-module  134  includes a plurality of resonance-control shields  155 . The connector shield  153  is positioned along a side of the connector sub-module  134 . The resonance-control shields  155  are configured to form a column in which each resonance-control shield  155  at least partially surrounds a corresponding signal pair  151 . 
     In some embodiments, the connector sub-module  134  includes a conductive holder  154 . The conductive holder  154  may include a first holder member  156  and a second holder member  158  that are coupled together. The first and second holder members  156 ,  158  may be fabricated from a conductive material. For example, the first and second holder members  156 ,  158  may be metalized or be formed from a dielectric material having conductive fillers or particles. In such embodiments, the first and second holder members  156 ,  158  may provide electrical shielding for the electrical connector  132 . When the first and second holder members  156 ,  158  are coupled together, the first and second holder members  156 ,  158  define at least a portion of a shielding structure. 
     The conductive holder  154  is configured to support a conductor assembly  160  that includes a pair of dielectric frames  162 ,  164 . The dielectric frames  162 ,  164  are configured to surround the signal conductors  150 . As shown, the signal contacts  152  and the mounting contacts  166  clear the dielectric frames  162 ,  164 . The mounting contacts  166  are configured to mechanically engage and electrically couple to conductive vias  168  of the circuit board  146 . Each of the signal contacts  152  is electrically coupled to a corresponding mounting contact  166  through the corresponding signal conductor  150 . 
     As shown in  FIG. 2 , the first and second holder members  156 ,  158  include respective member slots  157 ,  159 . When the first and second holder members  156 ,  158  are coupled to each other with the conductor assembly  160  therebetween, the member slots  157 ,  159  combine to form a plurality of holder slots (not shown). Each of the holder slots is configured to receive one of the resonance-control shields  155  such that the conductive holder  154  engages and electrically couples to the resonance-control shields  155 . Optionally, the resonance-control shields  155  may engage the connector shield  153 . The resonance-control shields  155  are positioned such that each of the resonance-control shields  155  at least partially surrounds a corresponding signal pair  151 . In alternative embodiments, each of the resonance-control shields  155  may surround only a single signal contact. 
     The connector sub-modules  134  are coupled to the connector housing  136  such that the signal contacts  152  and the resonance-control shields  155  are aligned with the contact cavities (not shown) of the connector housing  136 . The cavity openings  138 ,  140  provide access to corresponding contact cavities. The cavity opening  138  is sized and shaped to receive a ground shield (not shown), such as the ground shields  206  (shown in  FIG. 3 ). The ground shields may engage the corresponding resonance-control shields  155  within the contact cavities. The cavity openings  140  are configured to receive corresponding signal terminals of a mating electrical connector (not shown) during a mating operation. Such signal terminals may be similar or identical to the signal terminals  204  (shown in  FIG. 3 ). The signal terminals may engage the signal contacts  152  within the corresponding contact cavities. 
       FIG. 3  is an isolated perspective view of the electrical connector  108  in accordance with an embodiment. As shown, the connector body  124  includes a pair of body walls  170 ,  172  that extend away from the front side  126  along the mating axis  191 . The body walls  170 ,  172  define a receiving space  174  therebetween that is sized and shaped to receive the connector housing  120  ( FIG. 1 ) of the electrical connector  112  ( FIG. 1 ). In the illustrated embodiment, the receiving space  174  is open-sided such that only the opposing body walls  170 ,  172  define the receiving space  174 . In other embodiments, the connector body  124  may include one additional body wall (not shown) that extends between the body walls  170 ,  172  along the first lateral axis  192  or two additional body walls (not shown) that oppose each other and extend between the body walls  170 ,  172  along the first lateral axis  192 . Accordingly, the receiving space  174  may be partially surrounded or entirely surrounded by the connector body  124 . 
     The electrical connector  108  includes a conductor array  202  that is coupled to the connector body  124  and positioned within the receiving space  174 . The conductor array  202  includes a plurality of signal terminals  204  and a plurality of ground shields  206 ,  208 . The ground shields  206  are configured to engage corresponding resonance-control shields  250  (shown in  FIG. 4 ) of the electrical connector  112  ( FIG. 1 ). The signal terminals  204  and the ground shields  206 ,  208  are secured to the conductor body  124  in fixed positions. The signal terminals  204  and the ground shields  206 ,  208  extend through the connector body  124  between the front and mounting sides  126 ,  128 . The signal terminals  204  and the ground shields  206 ,  208  may clear each of the front and mounting sides  126 ,  128  for engaging the electrical connector  112  ( FIG. 1 ) and the circuit board  106  ( FIG. 1 ), respectively, proximate to the front side  126  and the mounting side  128 , respectively. As shown, the signal terminals  204  and the ground shields  206 ,  208  project from the front side  126  into an exterior of the connector body  124  within the receiving space  174 . 
     The signal terminals  204  and the ground shields  206 ,  208  are configured to have a designated shape and are arranged in a predetermined pattern for engaging the electrical connector  112  ( FIG. 1 ) and the circuit board  106  ( FIG. 1 ). To this end, each of the signal terminals  204  and each of the ground shields  206 ,  208  includes a portion that engages the electrical connector  112  and a portion that engages the circuit board  106 . 
     In the illustrated embodiment, the conductor array  202  is a two-dimensional array having multiple columns and rows that extend along the first and second lateral axes  192 ,  193 , respectively. In other embodiments, the conductor array  202  may be a one-dimensional array that includes a single row or column of signal terminals  204  and ground shields  206 . In particular embodiments, the conductor array  202  is a high-density array. For example, the conductor array  202  may include at least 12 signal terminals  204  per 100 mm 2  along the front side  126  of the electrical connector  108 . In more particular embodiments, the conductor array  202  may include at least 20 signal terminals  204  per 100 mm 2  along the front side  126  of the electrical connector  108 . 
     The signal terminals  204  and the ground shields  206  are arranged to form a plurality of terminal sub-assemblies  215 . The conductor array  202  may include multiple rows  230  of the terminal sub-assemblies  215  in which each row  230  includes a plurality of the terminal sub-assemblies  215  arranged along the second lateral axis  193 . In the illustrated embodiment, each of the terminal sub-assemblies  215  includes two signal terminals  204 , which form a signal pair  222 , and a corresponding ground shield  206  that is proximate to the signal pair  222 . Each ground shield  206  may be shaped to surround the corresponding signal pair  222 . For example, the ground shields  206  are C-shaped or U-shaped in the illustrated embodiment. 
     In other embodiments, however, one or more of the ground shields  206  may be L-shaped or rectangular-shaped such that the ground conductor forms a box that completely surrounds the signal pair  222 . Alternatively, each ground shield  206  may be assembled from multiple discrete ground blades that are positioned to surround the corresponding signal pair  222 . Although the terminal sub-assemblies  215  are shown and described as including a signal pair  222  and a corresponding ground shield  206 , embodiments are not required to include signal pairs. For example, embodiments may include terminal sub-assemblies having only one signal terminal that is surrounded by one or more ground shields. 
     Each of the signal terminals  204  and the ground shields  206  project from the front side  126  in a forward direction along the mating axis  191  such that the signal terminals  204  and the ground shields  206  clear the dielectric material of the connector body  124  and are exposed for engaging corresponding contacts of the electrical connector  112  ( FIG. 1 ). As shown, the ground shield  206  includes a stub portion  338 . The stub portion  338  represents the portion of the ground shield  206  that is exposed to an exterior of the electrical connector  108 . 
       FIG. 4  is a perspective view of a resonance-control shield  250  in accordance with an embodiment that may be used with the receptacle connector of  FIG. 1 . For reference, the resonance-control shield  250  is oriented with respect to the axes  191 - 193 . The resonance-control shield  250  is configured to directly interface with one of the ground shields  206  ( FIG. 3 ) such that the resonance-control shield  250  and the corresponding ground shield  206  capacitively couple to each other. As described herein, the capacitive coupling may disrupt or impede the development of resonating conditions between the electrical connector  108  ( FIG. 1 ) and the electrical connector  112  ( FIG. 1 ). 
     The resonance-control shield  250  includes a shield base  252  and a damper body  254  that is coupled to the shield base  252 . The damper body  254  is configured to directly interface with the stub portion  338  ( FIG. 3 ) of the ground shield  206 . The damper body  254  includes a plurality of damping walls  255 ,  256 ,  257  that define a receiving space or cavity  258 . The damping wall  256  extends between and joins the damping walls  255 ,  257 . The damping walls  255 ,  257  may oppose each other with the receiving space  258  therebetween. 
     In some embodiments, the resonance-control shield  250  may be stamped-and-formed from sheet metal, although it is contemplated that the resonance-control shield  250  may be made by other processes. For example, the resonance-control shield  250  may be 3D printed, molded with a dielectric material having conductive particles, or may be molded from dielectric material and then plated with metal. The damping walls  255 - 257  may be portions of one unitary structure. In other embodiments, the damping walls  255 - 257  may be discrete elements that are positioned relative to each other to form the designated shape of the resonance-control shield  250 . As shown, the damping walls  255 - 257  are arranged such that the resonance-control shield  250  or, more specifically, the damper body  254  has a non-planar or three-dimensional (3D) structure that defines the receiving space  258 . In the illustrated embodiment, the damper body  254  is U-shaped or C-shaped. In other embodiments, the resonance-control shield  250  may be L-shaped, V-shaped, I-shaped, or X-shaped. In other embodiments, the resonance-control shield  250  may be blade-shaped, such that the resonance-control shield  250  includes only one of the damping walls  255 - 257 . 
     The damper body  254  includes an inner body surface  262  and an outer body surface  264 . The inner body surface  262  may define the receiving space  258 . The damper body  254  also has a leading edge  270 . Each of the damping walls  255 - 257  includes a portion or segment of the leading edge  270 . In an exemplary embodiment, the leading edge  270  represents the portion of the damper body  254  that is furthest from the shield base  252 . 
     In some embodiments, each of the damping walls  255 - 257  includes a wall body  272  and one or more spring members  274 . The spring member(s)  274  extend away from the respective wall body  272  and are configured to engage the ground shield  206  ( FIG. 3 ) at one or more contact zones  360  (shown in  FIG. 9 ). The contact zones  360  represent interfaces that direct current (DC) may propagate through. In the illustrated embodiment, the spring members  274  constitute resilient beams  276  that extend across and couple to opposite inner edges  278 ,  280  of the corresponding damping wall. The resilient beams  276  are defined between two slots  282 . The spring members  274  (or resilient beams  276 ) are configured to engage the ground shield  206  and be deflected away from the receiving space  258 . The resilient beams  276  may be shaped to extend into the receiving space  258 . As shown, the damping wall  256  includes two spring members  274 , and the damping walls  256 ,  257  each include one spring member  274 . The spring members  274  may be positioned such that the contact zones  360  are located at designated positions along the ground shield  206 . 
     The shield base  252  is configured to be secured to a conductive holder  326  (shown in  FIG. 7 ), which may be similar to the conductive holder  154  ( FIG. 2 ). To this end, the shield base  252  may be shaped to form an interference fit or frictional engagement with the conductive holder  326 . For example, the shield base  252  may include coupling features  288  that engage features of the conductive holder  326 . In the illustrated embodiment, the coupling features  288  are projections or tabs, but may take other shapes in other embodiments. The shield base  252  may be sized and shaped to be inserted into a holder slot (not shown) that is defined by the conductive holder  326 . 
     The damping walls  255 - 257  have respective broad surfaces  285 - 287 . The broad surfaces  285 - 287  are portions of the inner body surface  262 . The damping walls  255 - 257  have wall widths  265 ,  266 ,  267 , respectively. The wall widths  265 ,  267  are measured along the first lateral axis  192 , and the wall width  266  is measured along the second lateral axis  193 . In the illustrated embodiment, the wall widths  265 ,  267  have the same dimension, and the wall width  266  has a greater dimension than each of the wall widths  265 ,  267 . However, in other embodiments, the wall widths  265 - 267  may have different relative dimensions than those shown in  FIG. 4 . In some embodiments, the damping walls  255 ,  257  may be referred to as side walls, and the damping wall  256  may be referred to as a broadside wall. 
       FIG. 5  is a side view of the resonance-control shield  250 . In the illustrated embodiment, each of the damping walls  255 ,  256 , and the damping wall  257  ( FIG. 4 ) has a common wall length  260  that is measured along the longitudinal axis  191 . In other embodiments, however, the damping walls  255 - 257  may have different lengths. As described herein, the receiving space  258  is sized and shaped to receive the ground shield  206  ( FIG. 3 ), and the damping walls  255 - 257  are sized and shaped to directly interface with and capacitively couple to the ground shield  206 . 
     Accordingly, the length  260  of the damping walls  255 - 257 , the wall widths  265 ,  267 , and the wall width  266  ( FIG. 4 ) may be configured to achieve a designated electrical performance for the interconnection system  100  ( FIG. 1 ). For example, the broad surface  285  ( FIG. 4 ) may have a surface area that is determined by the wall length  260  and the wall width  265 , the broad surface  286  ( FIG. 4 ) may have a surface area that is determined by the wall length  260  and the wall width  266 , and the broad surface  287  ( FIG. 4 ) may have a surface area that is determined by the wall length  260  and the wall width  267 . The surfaces areas of the broad surfaces  285 - 287  may be selectively configured to increase or decrease an amount of capacitance between the ground shield  206  ( FIG. 3 ) and the resonance-control shield  250  to control unwanted resonance within the interconnection system  100  ( FIG. 1 ). 
       FIG. 6  is a plan view of a portion of the front side  116  of the electrical connector  112 . In particular,  FIG. 6  shows a single access sub-array  300  that includes two cavity openings  302  and a cavity opening  304 . The cavity openings  302 ,  304  provide access to a common contact cavity  301  of the connector body  114 . Each contact cavity  301  has a single contact sub-assembly  306  disposed therein, but it is understood that the electrical connector  112  may include an array of contact sub-assemblies  306 . In the illustrated embodiment, each of the contact sub-assemblies  306  includes a signal pair  308  of signal contacts  310  and one of the resonance-control shields  250 . In  FIG. 6 , a portion of the leading edge  270  of the resonance-control shield  250  is shown within the contact cavity  301 . Also shown, the spring members  274  have coupling areas  320  that are positioned within the contact cavity  301 . The coupling areas  320  represent the portions of the spring members  274  that engage the ground shield  206  ( FIG. 3 ). 
     Each signal contact  310  includes a pair of contact beams  312  having respective mating areas  314  that face each other. The two mating areas  314  of a single signal contact  310  are configured to engage one of the signal terminals  204  ( FIG. 3 ). In other embodiments, the contact sub-assembly  306  may include only one signal contact. Each of the cavity openings  302  is configured to receive a single signal terminal  204 , and the cavity opening  304  is configured to receive a single ground shield  206  ( FIG. 3 ). The cavity openings  302  are defined by a center housing portion  316  of the connector body  114 . The cavity opening  304  is partially defined by the center housing portion  316  and partially defined by an outer housing portion  318  of the connector body  114 . The center housing portion  316  separates the cavity openings  302  from the cavity opening  304 . The center housing portion  316  has a beveled or chamfered surface  319  that facilitates directing the ground shield  206  into the cavity opening  304 . The cavity opening  304  and the ground shield  206  may be similarly shaped such that the ground shield  206  may be inserted therein. In the illustrated embodiment, the cavity opening  304  is U-shaped or C-shaped. In other embodiments, the cavity opening  304  may be L-shaped, rectangular, or slot-shaped. 
     In some embodiments, the inner body surface  262  of the resonance-control shield  250  defines an inner profile of the resonance-control shield  250 . The cavity opening  304  may be defined by an outer opening edge  305  of the connector body  114 . As shown in  FIG. 6 , the outer opening edge  305  and the inner body surface  262  may be sized and shaped to permit the ground shield  206  ( FIG. 3 ) to be inserted into the contact cavity  301  and engage the resonance-control shield  250  or, more specifically, the spring members  274 . 
       FIG. 7  is a cross-section of the electrical connector  112  prior to the electrical connector  112  engaging the electrical connector  108  ( FIG. 1 ) during the mating operation. The connector body  114  defines a plurality of the contact cavities  301 . As shown, each of the contact cavities  301  may form a portion of a larger housing cavity  322 . More specifically, each contact cavity  301  may represent a localized region of the housing cavity  322  that has a contact sub-assembly  306  disposed therein. In  FIG. 7 , adjacent contact cavities  301  are at least partially separated by the outer housing portion  318  and an inner housing wall  324  of the connector body  114 . Also shown in  FIG. 7 , the shield bases  252  are secured to the conductive holder  326 . Although not shown, the shield bases  252  may be inserted into holder slots of the conductive holder  326  and engage the conductive holder  326 . 
     As described herein, each contact sub-assembly  306  may include a resonance-control shield  250  and one or more signal contacts  310 . The resonance-control shield  250  is positioned relative to the cavity opening  304  such that the ground shield  206  ( FIG. 3 ) is received within the receiving space  258  of the resonance-control shield  250  when the ground shield  206  advances through the cavity opening  304  along the mating axis  191 . The signal contacts  310  are each positioned relative to the corresponding cavity opening  302  such that the signal terminal  204  ( FIG. 3 ) engages the corresponding signal contact  310  when the signal terminal  204  advances through the cavity opening  302  along the mating axis  191 . 
     In some embodiments, the connector body  114  may be shaped to engage the resonance-control shields  250  and align the resonance-control shields  250  relative to the corresponding cavity opening  304 . In some embodiments, the resonance-control element  250  may be sized and shaped such that the resonance-control element  250  is incapable of moving through the cavity opening  304 . For example, the leading edge  270  may be shaped to have an outer profile that is larger than the cavity opening  304 . In some embodiments, the leading edge  270  of the resonance-control element  250  may engage an interior surface  330  of the connector body  114 . In the illustrated embodiment, the leading edge  270  along the damping wall  256  engages the interior surface  330  of the connector body  114 . The damping wall  255  and/or the damping wall  257  ( FIG. 4 ) may also engage the interior surface  330 . As such, the interior surface  330  may effectively block the resonance-control element  250  from moving into the cavity opening  304 . 
       FIG. 8  is a cross-section of the interconnection system  100  ( FIG. 1 ) after the electrical connector  112  and the electrical connector  108  have been mated to each other. In  FIG. 8 , each of the resonance-control shields  250  has received a corresponding ground shield  206  within the receiving space  258  ( FIG. 4 ). The ground shields  206  within the corresponding receiving spaces  258  are represented by dashed lines. The stub portions  338  of the ground shields  206  project from the front side  126  of the connector body  124  of the electrical connector  108 . The stub portions  338  have respective stub lengths  340  that are measured between the front side  126  and a leading edge  342  of the ground shield  206 . The leading edges  342  may directly interface with a portion of the resonance-control shield  250 . For example, the leading edge  342  may engage the resonance-control shield  250 , or a nominal gap may exist between the leading edge  342  and the resonance-control shield  250 . 
     As shown, a majority of the stub portion  338  for each of the ground shields  206  is located within the receiving space  258  of the corresponding resonance-control shield  250 . In some embodiments, at least 50% of the stub length  340  is positioned within the receiving space  258 . In certain embodiments, at least 65% of the stub length  340  is positioned within the receiving space  258 . In more particular embodiments, at least 75% of the stub length  340  is positioned within the receiving space  258 . 
       FIG. 9  shows an end view of four contact sub-assemblies  306 A,  306 B,  306 C,  306 D in the housing cavity  322  when the contact sub-assemblies  306 A- 306 D are engaged with terminal sub-assemblies  215 A,  215 B,  215 C,  215 D, respectively, after the mating operation. For illustrative purposes, the connector body  114  ( FIG. 1 ) of the electrical connector  112  ( FIG. 1 ) and the connector body  124  ( FIG. 1 ) of the electrical connector  108  ( FIG. 1 ) are not shown. It should be understood that each of the contact sub-assemblies  306 A- 306 D and each of the terminal sub-assemblies  215 A- 215 D include identical elements and features in the illustrated embodiment. For clarity, however, each of these elements or features may not be referenced in  FIG. 9 . 
     In the illustrated embodiment, the stub portion  338  of each of the ground shields  206  includes shield walls  345 ,  346 , and  347 . As shown with respect to the terminal sub-assembly  215 C, the shield walls  345 - 347  have respective broad surfaces  355 ,  356 ,  357 . The broad surfaces  285 - 287  of the resonance-control shield  250  face and capacitively couple to the broad surfaces  355 - 357 , respectively, of the ground shield  206 . As such, the ground shields  206  directly interface with the corresponding resonance-control shields  250 . In an exemplary embodiment, as shown with respect to the terminal sub-assembly  215 D and the contact sub-assembly  306 D, the spring members  274  of the resonance-control shields  250  engage the ground shield  206  at the contact zones  360 . Current may propagate through the contact zones  360  during operation of the interconnection system  100  ( FIG. 1 ). In other embodiments, the resonance-control shield  250  may include more or fewer spring members  274 . In alternative embodiments, the resonance-control shield  250  may not have the spring members  274 . 
     In an exemplary embodiment, the ground shields  206  may be nested within corresponding resonance-control shields  250 . More specifically, each of the resonance-control shields may include multiple damping walls that are coupled to each other and are substantially perpendicular to each other. These damping walls may be positioned adjacent to corresponding shield walls of the ground shield. For example, the damping walls  255 ,  256  are coupled to each other and are perpendicular to each other. The damping walls  256 ,  257  are coupled to each other and are perpendicular to each other. Accordingly, each of the contact cavities  301  ( FIG. 7 ) is configured to permit (a) the shield wall  345  of the ground shield  206  to be positioned between one of the signal contacts  310  and the damping wall  255 ; (b) the shield wall  346  of the ground shield  206  to be positioned between one of the signal contacts  310  and the damping wall  256 ; and (c) the shield wall  347  of the ground shield  206  to be positioned between one of the signal contacts  310  and the damping wall  257 . 
     In the illustrated embodiment, the interconnection system  100  ( FIG. 1 ) is devoid of separate ground contacts within the receiving spaces  258  of the resonance-control shields  250 . For example, the interconnection system  100  is devoid of a ground contact that is positioned between the ground shield  206  and the signal contacts  310 . In other embodiments, however, the interconnection system  100  may include a ground contact positioned between the ground shield  206  and the signal contacts  310 . 
     During operation of the interconnection system  100  ( FIG. 1 ), electrical energy may exist between the shield walls  345 - 347  of the ground shields  206 . As one example, a physical gap  362  exists between the shield wall  347  of the terminal sub-assembly  215 C and the shield wall  345  of the terminal sub-assembly  215 D. As electrical energy propagates through the signal terminals  204  and the signal contacts  310 , the shield walls  345 - 347  of the ground shields  206  may support electrical energy that radiates from the signal terminals  204  and the signal contacts  310 . The ground shields  206  may form one or more resonant cavities within the housing cavity  322 . As electrical energy propagates within each resonant cavity along the mating axis  191 , reflections between the circuit board  106  ( FIG. 1 ) and the electrical connector  112  ( FIG. 1 ) can occur and be supported by the shield walls  345 - 347 . 
     Without the resonance-control shields  250 , such reflections may form a standing wave (or resonating condition) at certain frequencies. The standing wave (or resonating condition) may cause electrical noise that, in turn, may increase return loss and/or crosstalk and reduce throughput of the interconnection system  100  ( FIG. 1 ). The resonance-control shields  250  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 resonance-control shields  250  may absorb some of the electrical energy that propagates through the corresponding ground cavity and drain the electrical energy. In some embodiments, the resonance-control shields  250  effectively change or dampen the reflections such that the standing wave (or the resonating condition) is not formed during operation of the interconnection system  100 . 
     As shown with respect to the terminal sub-assembly  215 B and the contact sub-assembly  306 B, the resonance-control shield  250  and the ground shield  206  are separated from each other by capacitive gaps  375 - 377 . The capacitive gap  375  exists between the broad surface  285  of the resonance-control shield  250  and the broad surface  355  of the ground shield  206 . The capacitive gap  376  exists between the broad surface  286  of the resonance-control shield  250  and the broad surface  356  of the ground shield  206 . The capacitive gap  377  exists between the broad surface  287  of the resonance-control shield  250  and the broad surface  357  of the ground shield  206 . 
     Effectiveness of the resonance-control shields  250  may depend on the number and location of the contact zones  360  and an amount of capacitance generated by the broad surfaces  285 - 287  of the resonance-control shields  250  and the corresponding broad surfaces  355 - 357  of the ground shields  206 . The capacitance may depend on the amount of surface area that the resonance-control shield  250  and the ground shield  206  overlap and the sizes of the capacitive gaps. For example, the capacitance may increase if the overlapping area is increased and/or the capacitive gap is decreased. The capacitance may decrease if the overlapping area is decreased and/or the capacitive gap is increased. 
     The capacitive gaps  375 - 377  may be common between each pair of opposing broad surfaces. For example, the capacitive gap  375  between the broad surface  285  and the broad surface  355  may be the same as the capacitive gap  376  between the broad surface  286  and the broad surface  356 . In other embodiments, however, one or more of the capacitive gaps  375 - 377  may be different. By way of example, one or more of the capacitive gaps  375 - 377  may be at most 0.40 mm. In some embodiments, one or more of the capacitive gaps  375 - 377  may be at most 0.30 mm. In particular embodiments, one or more of the capacitive gaps  375 - 377  may be at most 0.25 mm or, more particularly, at most 0.20 mm. In certain embodiments, one or more of the capacitive gaps  375 - 377  may be at most 0.15 mm. 
     By way of example, the overlapping area between broad surfaces that face each other may be at least 2.5 mm 2 . In some embodiments, the overlapping area between broad surfaces that face each other may be at least 4.0 mm 2 . In some embodiments, the overlapping area between broad surfaces that face each other may be at least 5.0 mm 2 . The total overlapping area between the ground shield and the corresponding resonance-control shield may be at least 3.0 mm 2  or at least 5.0 mm 2 . In some embodiments, the total overlapping area between the ground shield and the corresponding resonance-control shield may be at least 7.5 mm 2 . In particular embodiments, the total overlapping area between the ground shield and the corresponding resonance-control shield may be at least 10.0 mm 2  or, more particularly, at least 12.0 mm 2 . In more particular embodiments, the total overlapping area between the ground shield and the corresponding resonance-control shield may be at least 15.0 mm 2 . 
     In some embodiments, a majority of one or more of the broad surfaces  355 - 357  of the ground shield  206  overlap with the respective broad surfaces  285 - 287  of the corresponding resonance-control shield  250 . In some embodiments, a majority of one or more of the broad surfaces  285 - 287  of the resonance-control shield  250  overlap with the respective broad surfaces  355 - 357  of the corresponding ground shield  206 . 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, 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.” 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.