Patent Publication Number: US-2015072561-A1

Title: Cage with emi absorber

Description:
BACKGROUND OF THE INVENTION 
     The subject matter described and/or illustrated herein relates generally to receptacle assemblies, and more particularly to the metal cages of receptacle assemblies. 
     Various types of fiber optic and copper based electrical connector assemblies that permit communication between host equipment and external devices are known. These electrical connector assemblies typically include a pluggable module that is received within a receptacle assembly, which includes a receptacle connector that pluggably connects to the pluggable module. Receptacle assemblies typically include a metal cage having an internal compartment that receives the pluggable module therein. The receptacle connector is held in the cage for connection with the pluggable module as the module is inserted into the cage. The pluggable modules are constructed according to various standards for size and compatibility, for example the Quad Small Form-factor Pluggable (QSFP) module standard and the XFP standard. 
     One particular concern regarding receptacle assemblies is reducing electromagnetic interference (EMI) emissions. Due to government regulations, there is a need not only to minimize the EMI emissions of the electrical connector assembly, but also to contain the EMI emissions of the host system in which the electrical connector assembly is mounted, regardless of whether a pluggable module is plugged in to the receptacle. In at least some known receptacle assemblies, EMI shielding is achieved using the metal cage. However, due to increasing signal speeds being transmitted through the electrical connector assemblies, the EMI shielding provided by conventional cages is proving to be inadequate. 
     Accordingly, there is a need for an electrical connector assembly that reduces EMI emissions. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In an embodiment, a cage is provided for a receptacle assembly that includes a receptacle connector. The cage includes a body having an upper wall, a lower wall, and side walls that extend from the upper wall to the lower wall. The body has a lower side along which the lower wall extends, a front end, and an internal compartment. The internal compartment is configured to hold the receptacle connector therein. The internal compartment is configured to receive a pluggable module therein through the front end. The cage is configured to be mounted to a printed circuit along the lower side. The lower side includes a connector opening. An electromagnetic interference (EMI) absorber extends over at least a portion of the lower wall. The EMI absorber is configured to absorb EMI. 
     In an embodiment, a receptacle assembly is provided for mating with a pluggable module. The receptacle assembly includes a receptacle connector, and a cage that includes a body having an upper wall, a lower wall, and side walls that extend from the upper wall to the lower wall. The body has a lower side along which the lower wall extends, a front end, and an internal compartment. The receptacle connector is held within the internal compartment. The internal compartment is configured to receive the pluggable module therein through the front end. The cage is configured to be mounted to a printed circuit along the lower side. The lower side includes a connector opening. The cage includes an electromagnetic interference (EMI) absorber that extends over at least a portion of the lower wall. The EMI absorber is configured to absorb EMI. 
     In an embodiment, a cage is provided for a receptacle assembly that includes a receptacle connector. The cage includes a body having an upper wall, a lower wall, and side walls that extend from the upper wall to the lower wall. The body has a lower side along which the lower wall extends, a front end, and an internal compartment. The internal compartment is configured to hold the receptacle connector therein. The internal compartment is configured to receive a pluggable module therein through the front end. The cage is configured to be mounted to a printed circuit along the lower side. The lower side includes a connector opening. The cage includes an electromagnetic interference (EMI) absorber that is configured to absorb EMI. The EMI absorber extends along a perimeter of the lower wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an embodiment of an electrical connector assembly. 
         FIG. 2  is a cross-sectional view of the electrical connector assembly shown in  FIG. 1  illustrating an embodiment of a pluggable module mated with an embodiment of a receptacle assembly. 
         FIG. 3  is a perspective view of an embodiment of a cage of the electrical connector assembly shown in  FIGS. 1 and 2 . 
         FIG. 4  is another perspective view of the cage illustrating an embodiment of an electromagnetic interference (EMI) absorber of the cage. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of a portion of an embodiment of an electrical connector assembly  10 . The electrical connector assembly  10  may be commonly referred to as a “transceiver assembly”. In an embodiment, the electrical connector assembly  10  is adapted to address, among other things, conveying data signals at high rates, such as, but not limited to, data transmission rates of at least 10 gigabits per second (Gbps), which is required by the SFP+ standard. For example, in some embodiments the electrical connector assembly  10  is adapted to convey data signals at a data transmission rate of at least 28 Gbps. Moreover, and for example, in some embodiments the electrical connector assembly  10  is adapted to convey data signals at a data transmission rate of between approximately 20 Gbps and approximately 30 Gbps. It is appreciated, however, that the benefits and advantages of the subject matter described and/or illustrated herein may accrue equally to other data transmission rates and across a variety of systems and standards. In other words, the subject matter described and/or illustrated herein is not limited to data transmission rates of 10 Gbps or greater, any standard, or the exemplary type of electrical connector and/or transceiver assembly shown and described herein. 
     The electrical connector assembly  10  includes one or more pluggable modules  12  configured for pluggable insertion into a receptacle assembly  14  that is mounted on a host circuit board  15  ( FIG. 2 ). The host circuit board  15  may be mounted in a host system (not shown) such as, but not limited to, a router, a server, a computer, and/or the like. The host system typically includes a conductive chassis (not shown) having a panel (not shown) including one or more openings (not shown) extending therethrough in substantial alignment with the receptacle assembly  14 . The receptacle assembly  14  is optionally electrically connected to the panel. Only one pluggable module  12  is shown in  FIG. 1  for clarity. The host circuit board  15  may be referred to herein as a “printed circuit”. 
     The pluggable module  12  is configured to be inserted into the receptacle assembly  14 . Specifically, the pluggable module  12  is inserted into the receptacle assembly  14  through the panel opening such that a front end  22  of the pluggable module  12  extends outwardly from the receptacle assembly  14 . The pluggable module  12  includes a housing  24  that forms a protective shell for a circuit board  26  that is disposed within the housing  24 . The circuit board  26  will be referred to herein as a “module circuit board” and carries circuitry, traces, paths, devices, and/or the like that perform transceiver functions in a known manner. An edge  28  of the module circuit board  26  is exposed at a rear end  30  of the housing  24 . In the illustrated embodiment, the module circuit board  26  of the pluggable module  12  directly mates with a receptacle connector  34  ( FIG. 2 ) of the receptacle assembly  14 . In other words, the edge  28  of the module circuit board  26  of the pluggable module  12  is received within a receptacle  54  ( FIG. 2 ) of the receptacle connector  34  to electrically connect the pluggable module  12  to the receptacle connector  34 . Alternatively, a straddle mount connector (not shown) is mounted to the module circuit board  26  and exposed at the rear end  30  of the housing  24  for plugging into the receptacle  54  of the receptacle connector  34 . 
     In general, the pluggable module  12  and the receptacle assembly  14  may be used in any application requiring an interface between a host system and electrical and/or optical signals. Each pluggable module  12  interfaces to the host system through the receptacle assembly  14  via the corresponding receptacle connector  34  of the receptacle assembly  14 , which is located within an electrically conductive cage  36  (which is sometimes referred to as a “receptacle guide frame” or a “guide frame”) of the receptacle assembly  14 . As illustrated in  FIG. 1 , the cage  36  includes a front end  38  having one or more front openings, or ports,  40  that are open to corresponding internal compartments  42  of the cage  36 . The front end  38  of the cage  36  is configured to be mounted, or received, within the opening in the panel. A receptacle connector  34  ( FIG. 2 ) is positioned within each internal compartment  42  at a rear end  44  of the cage  36 . The cage  36  is configured to be mounted to the host circuit board  15  along a lower side  46  of the cage  36 . The lower side  46  of the cage  36  includes one or more openings  48  ( FIGS. 3 and 4 ) for enabling each receptacle connector  34  to electrically connect to the host circuit board  15  from within the corresponding internal compartment  42 . Each internal compartment  42  of the cage  36  is configured to receive the corresponding pluggable module  12  therein in electrical connection with the corresponding receptacle connector  34 . Each of the openings  48  may be referred to herein as a “connector opening”. 
     Each pluggable module  12  interfaces to one or more optical cables (not shown) and/or one or more electrical cables (not shown) through a connector interface  50  at the front end  22  of the module  12 . Optionally, the connector interface  50  comprises a mechanism that cooperates with a fiber or cable assembly (not shown) to secure the fiber or cable assembly to the pluggable module  12 . Suitable connector interfaces  50  are known and include adapters for the LC style fiber connectors and the MTP/MPO style fiber connectors offered by TE Connectivity (Harrisburg, Pa.). 
     Although the cage  36  is shown as including a plurality of internal compartments  42  and a plurality of ports  40  for electrically connecting a plurality of pluggable modules  12  to the host circuit board  15 , the cage  36  may include any number of internal compartments  42  and ports  40 , arranged in any pattern, configuration, arrangement, and/or the like (such as, but not limited to, any number of rows and/or columns), for electrically connecting any number of pluggable modules  12  to the host circuit board  15 . Optionally, an electromagnetic interference (EMI) gasket  52  extends circumferentially about one or more of the ports  40 . The EMI gasket  52  is configured to block EMI from leaking through an interface between the front end  38  of the cage  36  and the panel (not shown) to which the cage  36  is mounted. 
     As will be described in more detail below, the cage  36  includes an electromagnetic interference (EMI) absorber  100  that extends along the lower side  46  of the cage  36  and over at least a portion of a lower wall  76  of the cage  36 . The EMI absorber  100  is configured to absorb EMI. 
       FIG. 2  is a cross-sectional view of the electrical connector assembly  10  illustrating a pluggable module  12  received within the receptacle assembly  14  and mated with the corresponding receptacle connector  34 . The receptacle connector  34  is mounted on the host circuit board  15 . The receptacle connector  34  includes a dielectric connector body  56  having the receptacle  54 . 
     The receptacle  54  of the receptacle connector  34  receives the edge  28  of the module circuit board  26  of the pluggable module  12  therein. The receptacle connector  34  includes electrical contacts (not shown) that extend within the receptacle  54  and engage corresponding electrical contacts (not shown) on opposite sides  60  and  62  of the module circuit board  26  to establish an electrical connection between the module circuit board  26  of the pluggable module  12  and the host circuit board  15  through the receptacle connector  34 . 
       FIG. 3  is a perspective view of the cage  36 . The cage  36  includes an electrically conductive body  82 . The body  82  of the cage  36  extends a length from the front end  38  to the rear end  44 , and includes the lower side  46  and an upper side  72  that is opposite the lower side  46 . The cage body  82  includes an upper wall  74  (also labeled in  FIG. 1 ), the lower wall  76 , and side walls  78  and  80  that extend from the upper wall  74  to the lower wall  76 . The body  82  of the cage  36  also includes a rear wall  84  that extends from the upper wall  74  at the rear end  44 . Optionally, the cage body  82  includes one or more divider walls  86  that divide the body  82  into the plurality of internal compartments  42 . The cage body  82  may include any number of the divider walls  86  for dividing the body  82  into any number of internal compartments  42 . In some alternative embodiments, the body  82  of the cage  36  does not include any divider walls  86  such that the body  82  includes only a single internal compartment  42 . 
     The upper wall  74  extends along, and defines at least a portion of, the upper side  72  of the body  82 . The lower wall  76  extends along, and defines at least a portion of, the lower side  46  of the body  82 . In the illustrated embodiment, the cage  36  includes a generally rectangular cross-sectional shape, defined by the walls  74 ,  76 ,  78 , and  80 , such that the cage  36  generally has the shape of a parallelepiped. But, the cage  36  may include any other shape. 
     In the illustrated embodiment, the side walls  78  and  80  and the rear wall  84  of the cage body  82  are each integrally formed as a single, unitary piece with the upper wall  74 , while the lower wall  76  is a discrete component (of the cage body  82 ) relative to the upper wall  74 , the rear wall  84 , and the side walls  78  and  80 . The lower wall  76  is mechanically connected to each of the side walls  78  and  80  using any suitable connection structure, means, type, and/or the like that enables a mechanical connection between the lower wall  76  and the side walls  78  and  80 . In the illustrated embodiment, the lower wall  76  includes one or more mounting clips  92  that engage one or more corresponding mounting tabs  94  on the side walls  78  and  80  with a snap-fit connection to mechanically connect the lower wall  76  to the side walls  78  and  80 . In addition or alternatively to being integrally formed with the upper wall  74  and/or the rear wall  84 , the side walls  78  and/or  80  may be integrally formed with the lower wall  76 . Moreover, the rear wall  84  may be a discrete component of the cage body  82  relative to the upper wall  74  and/or the side walls  78  and/or  80 , and each of the side walls  78  and/or  80  may be a discrete component of the cage body  82  relative to the upper wall  74 , the rear wall  84 , and/or the lower wall  76 . 
     The divider walls  86  of the cage body  82  are discrete components of the cage body  82  relative to the upper wall  74  and the lower wall  76  in the illustrated embodiment. Each divider wall  86  is mechanically connected to the upper wall  74  and the lower wall  76  using any suitable connection structure, means, type, and/or the like that enables a mechanical connection therebetween. In the illustrated embodiment, the divider walls  86  are mechanically connected to the upper wall  74  via one or more mounting tabs  94  that are received within one or more corresponding slots  96  that extend within the upper wall  74 , as can be seen in  FIG. 1 . Referring again to  FIG. 3 , the divider walls  86  are mechanically connected to the lower wall  76  through one or more mounting tabs  98  that extend through one or more corresponding slots  102  within the lower wall  76 . In some alternative embodiments, one or more of the divider walls  86  is integrally formed with the upper wall  74  and/or the lower wall  76 . 
     The lower wall  76  includes a perimeter  104 , which is defined by a front edge  106 , a rear edge  108 , and opposite side edges  110  and  112  of the lower wall  76 . A surface area A of the lower wall  76  is defined between the edges  106 ,  108 ,  110 , and  112 . The lower wall  76  includes a plurality of interior segments  114  that are spaced apart from the edges  106 ,  108 ,  110 , and  112 . Optionally, a plurality of spring fingers  116  extend outward from the rear edge  108  to facilitate grounding the lower side  46  of the cage body  82  to the host circuit board  15  ( FIG. 2 ). The front edge  106  of the lower wall  76  optionally includes latch elements  118  for latching the pluggable modules  12  ( FIGS. 1 and 2 ) within the corresponding internal compartments  42 . 
     The rear wall  84  includes an edge  120 . The side walls  78  and  80  include respective edges  122  and  124 . The edges  106 ,  110 ,  112 ,  120 ,  122 , and  124  define a portion of the lower side  46  of the cage body  82 . Specifically, the edges  106 ,  110 ,  112 ,  120 ,  122 , and  124  define a perimeter  126  of the lower side  46  of the cage body  82 . As can be seen in  FIG. 3 , the openings  48  include perimeters  128  that are defined by the edges  108 ,  120 ,  122 , and  124 . 
       FIG. 4  is another perspective view of the cage  36  illustrating an embodiment of the EMI absorber  100 . As can be seen in  FIG. 4 , the EMI absorber  100  extends along the lower side  46  of the cage  36  and over the lower wall  76  of the cage  36 . In the illustrated embodiment, the EMI absorber  100  is an approximately planar sheet of material  130  that extends a width W from front edge  132  to a rear edge  134 . The sheet of material  130  extends a length L from a side edge  136  to an opposite side edge  138 . Although shown as having a generally rectangular shape, the sheet of material  130  of the EMI absorber  100  may include any other shape. 
     The sheet of material  130  of the EMI absorber  100  may extend over any amount of, and location(s) along, the lower side  46  of the cage  36 . In the illustrated embodiment, the sheet of material  130  extends along the perimeter  126  of the lower side  46 , over the lower wall  76 , and between adjacent connector openings  48  for absorbing EMI along the perimeter  126 , along the lower wall  76 , and between adjacent connector openings  48 . For example, segments  140 ,  142 , and  144  of the sheet of material  130  extend along the perimeter  126 . In some embodiments, the sheet of material  130  may extend along an approximate entirety of the perimeter  126 . For example, the sheet of material  130  may include a segment (not shown) that extends along the front edge  106  of the perimeter  126 . 
     The sheet of material  130  of the EMI absorber  100  extends over the lower wall  76 . Specifically, in the illustrated embodiment, the sheet of material  130  extends over the interior segments  114  of the lower wall  76  and along the perimeter  104  of the lower wall  76 . The segments  140  and  144  and a segment  150  of the sheet of material  130  extend along the perimeter  104  for absorbing EMI along the perimeter  104 . The sheet of material  130  extends over a majority of the surface area A of the lower wall  76  in the illustrated embodiment. But, the sheet of material  130  of the EMI absorber  100  may extend over any amount of, and location(s) along, the lower wall  76  of the cage  36 . For example, the sheet of material  130  may extend over less than a majority of the surface area A of the lower wall  76 . Moreover, and for example, the sheet of material  130  may extend along an approximate entirety of the perimeter  104 . For example, the sheet of material  130  may include a segment (not shown) that extends along the front edge  106  of the perimeter  104 . As shown in  FIG. 4 , the sheet of material  130  of the EMI absorber  100  includes openings  152  for tines  154  of the cage  36  that engage the host circuit board  15  ( FIG. 2 ). 
     The sheet of material  130  includes one or more openings  156 . Each opening  156  is at least partially aligned with a corresponding opening  48  of the lower side  46  of the cage  36 . The at least partial alignment between the corresponding openings  156  and  48  enables the corresponding receptacle connector  34  ( FIG. 2 ) to communicate with the host circuit board  15  through the corresponding openings  156  and  48 . Although shown as having the same approximate size as the openings  48 , each opening  156  may have any size relative to the corresponding opening  48 . Each of the openings  156  may be referred to herein as a “cage opening”. 
     In the illustrated embodiment, the sheet of material  130  of the EMI absorber  100  extends along the perimeter  128  of each of the openings  48  of the lower side  46  for absorbing EMI along the perimeters  128 . Although shown as extending along an approximate entirety of the perimeters  128 , the sheet of material  130  may extend along only a portion of one or more of the perimeters  128 . The sheet of material  130  may not extend along any of the perimeters  128  or may extend along only one or some of the perimeters  128  in other embodiments. Optionally, the sheet of material  130  includes segments  158  that extend between adjacent openings  48 . 
     The EMI absorber  100  is optionally secured to the lower side  46  of the cage  36 . The EMI absorber  100  may be secured to the lower side  46  of the cage  36  using any suitable method, structure, means, and/or the like, such as, but not limited to, using an interference fit (e.g., between the openings  152  and the tines  154 ), using an adhesive, using a tab, using a clip, and/or the like. 
     As briefly described above, the EMI absorber  100  is configured to absorb EMI. Specifically, the EMI absorber  100  has a relatively high permeability to absorb EMI. The EMI absorber  100  may be fabricated from any materials that provide the EMI absorber  100  with the relatively high permeability to absorb EMI, such as, but not limited to, a magnetic elastomer, rubber, nitrile, silicone, carbonal iron, a ferrite-based material, a ferrite material in a binder (e.g., a polymer binder), Viton® fluoroelastomer, neoprene, Hypolan® elastomer, urethane, an elastomeric material, and/or the like. The EMI absorber  100  may have magnetic fillers included within an elastomeric material, such as, but not limited to, a carbonyl iron powder, an iron silicide, other magnetic fillers, and/or the like. The type of material(s) within the EMI absorber  100  may be selected to target EMI at different frequencies. In some embodiments, the EMI absorber  100  includes a Q-Zorb™ material, commercially available from Laird Technologies. 
     Referring again to  FIG. 2 , when the receptacle assembly  14  is mounted on the host circuit board  15 , the EMI absorber  100  is sandwiched between the lower side  46  of the cage  36  and the host circuit board  15 . Specifically, the EMI absorber  100  is engaged in physical contact with both the lower side  46  of the cage  36  and the host circuit board  15  such that the EMI absorber  100  is engaged between the lower side  46  of the cage  36  and the host circuit board  15 . Optionally, the EMI absorber  100  is compressed between the host circuit board  15  and the lower side  46  of the cage  36 . 
     As described above, the EMI absorber  100  has a relatively high permeability to absorb EMI. The EMI absorber  100  is thus configured to absorb EMI emitted along the lower side  46  of the cage  36 . By absorbing EMI emitted along the lower side  46  of the cage  36 , the EMI absorber  100  may reduce or eliminate EMI leakage from an interface  160  between the lower side  46  of the cage  36  and the host circuit board  15 . For example, the EMI absorber  100  may reduce or eliminate EMI leakage from the interface  160  along the perimeter  126  ( FIG. 3 ) of the lower side  46  of the cage  36 . Moreover, and for example, the EMI absorber  100  may reduce or eliminate EMI leakage from the interface  160  through the openings  48  ( FIGS. 2 and 3 ). In some embodiments, the EMI absorber  100  eliminates substantially all EMI leakage from the interface  160 . Optionally, the EMI absorber  100  abuts an optional bracket  162  of the cage  36  that may hold the optional EMI gasket  52  ( FIG. 3 ). The efficiency of the EMI absorber  100  may depend on the formulation and application (e.g., thickness of the sheet of material  130 , relative permeability, size, location, and/or the like) of the EMI absorber  100 . 
     The embodiments described and/or illustrated herein may provide an electrical connector assembly that reduces EMI emissions. 
     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 invention 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 scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 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, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.