Patent Publication Number: US-8992262-B2

Title: Cross talk reduction for a high speed electrical connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date under 35 U.S.C. §119(a)-(d) of Singapore Patent Application No. 201104274-4, filed Jun. 10, 2011. 
     FIELD OF THE INVENTION 
     This invention relates broadly to crosstalk reduction for a high speed electrical connector. In particular, the invention relates to crosstalk reduction for a connector such as 12G SAS (12 Gbps Serial Attached SCSI) connector. 
     BACKGROUND 
     Electrical connectors are generally used to provide signal connections between various electronic devices and have electrical contacts for connecting electrical signals as well as ground. 
     Due to usage of micro-electronic devices, the increase in complexity of design of electric circuits has resulted in the need to use electrical connectors with closely positioned electrical contacts. It is generally known that such close proximity may cause crosstalk between adjacent signal contacts. 
     Crosstalk is an electrical phenomenon in signal transmission due to electrical signal interference between adjacent signal lines. Crosstalk in signal transmission leads to loss in signal integrity. Crosstalk in high speed electrical connectors can cause insertion of unwanted spikes into signal lines resulting in loss of high frequency signals. Often, resonance occurs when there is a shift in frequency due to crosstalk, which leads to signal degradation. 
     Conventionally, as shown in  FIG. 1 , in order to reduce crosstalk, a connector  100  is has adjacent signal contacts  101  separated from ground contacts  103 . In other words, signal contacts  101  are located in between ground contacts  103  and separate ground coupling contacts  105  are provided to connect all the ground contacts  103 . The electrical connection of separate ground coupling contacts  105  to ground contacts  103  relies on mechanical force of the ground coupling contacts  105 , which deteriorates over time. 
     There is thus a need to provide an electrical connector that seeks to address one or more of the above disadvantages. 
     SUMMARY 
     Embodiments of the present invention provide a high speed electrical connector with reduced crosstalk. One example of the high speed electrical connector is a 12G SAS connector. 
     The invention is embodied in an electrical connector having a housing receiving one or more series of electrical contacts. Each series of electrical contacts has a plurality of ground contacts and a plurality of signal contacts. The signal contacts are positioned in between the ground contacts, and the plurality of ground contacts are integrally connected to each other by a bus bar within the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in more detail below with reference to the embodiments shown in the drawings. Similar or corresponding details in the Figures are provided with the same reference numerals. The invention will be described in detail with reference to the following figures of which: 
         FIG. 1  is a perspective view of a conventional electrical connector; 
         FIG. 2  is a perspective view of a bussed ground contact used in a plug of the electrical connector; 
         FIG. 3  is a perspective view of a bussed ground contact used in a receptacle of the electrical connector; 
         FIG. 4   a  is an exemplary perspective view showing electrical contacts of a 12G SAS connector plug; 
         FIG. 4   b  is a partial inverted perspective view of  FIG. 4   a;    
         FIG. 5   a  is an exemplary perspective view showing electrical contacts of a 12G SAS connector receptacle; 
         FIG. 5   b  is an inverted perspective view showing electrical contacts of a 12G SAS connector receptacle with another bussed ground contact connected integrally with bus bars; 
         FIG. 6   a  is a partial perspective view of a housing for a conventional 12G SAS connector plug; 
         FIG. 6   b  is a partial perspective view of a housing for a 12G SAS connector plug; 
         FIG. 7   a  is a partial perspective view of a housing for a conventional 12G SAS connector receptacle; 
         FIG. 7   b  is a partial perspective view of a housing for a 12G SAS connector receptacle; and 
         FIG. 8  is a flowchart illustrating a method of fabricating an electrical connector. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     Illustrative embodiments of the invention will be described in detail with reference to the attached drawings, wherein the like reference numerals refer to the like elements. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. 
     Referring to  FIG. 2 , an exemplary bussed ground contact  200  used in a plug of the electrical connector is illustrated. Three ground contacts  250  are integrally connected by a bus bar  205 . 
     Each ground contact  250  has a linear contact portion  201  and a terminal portion  207  that are connected by a substantially rectangular base  203 . The base  203  has a orthogonal wall  202  and a securing section  204 . The terminal portion  207  has an inclined portion  206  and an arcuate portion  209 . The orthogonal wall  202  connects the contact portion  201  and one end of the securing section  204 , while the inclined portion  206  connects the other end of the securing section  204  and the arcuate portion  209 . Substantially at the center, the securing sections  204  are integrally connected by a bus bar  205 . As a result, the three ground contacts  250  provide two channels  208  through which signal contacts as shown in  FIGS. 4   a  and  4   b  are provided. The bus bars  205  provide ground integrity between the ground contacts  250 . In other words, the bus bars  205  provide reduction of ground loop inductance. 
     Referring to  FIG. 3 , an exemplary bussed ground contact  300  used in a receptacle of the electrical connector is illustrated. Three ground contacts  350  are integrally connected by a bus bar  305 . 
     Each ground contact  350  has a contact portion  301  and a terminal portion  307  that are connected by a base  310 . The terminal portion  307  has a substantially orthogonal wall  302  and an extension  309 . The base  310  has of a securing section  304  and an inclined wall  306 . One end of the orthogonal walls  302  terminates outside of the receptacle, for mounting on a PCB, while the other end of the orthogonal wall  302  is connected to one end of the extension  309 . The other end of the extension  309  is connected to one end of the securing section  304 . The inclined wall  306  connects the other end of the securing section  304  and an arm  303 , which in turn is connected to an arcuate contact portion  311 . Substantially at the center, the securing sections  304  are integrally connected by a bus bar  305 . As a result, the three ground contacts  350  provide two channels  308  through which signal contacts as sown in  FIGS. 5   a  and  5   b  are received. The integrally connected bus bars  305  provide ground integrity between the ground contacts  350 . In other words, the bus bars  305  provide reduction of ground loop inductance. 
       FIG. 4   a  is an exemplary perspective view showing electrical contacts of a 12G SAS connector plug (without a connector housing) in accordance with an embodiment of the present invention. The illustration shows three sets of the bussed ground contacts  200 , with each connected integrally by bus bars  205 . A pair of signal contacts  401  is provided between two ground contacts  250 , in between the channels  208  as shown in  FIG. 2  and beneath the bus bars  205 . 
     The pair of signal contacts  401  is a pair of differential signal contacts suitable for differential signal transmission. 
     Each signal contact  401  has a contact arm  403  and a terminal portion  409  that are connected by a retaining section  405 . The retaining section  405  has barbs on both sides thereof for securing to the connector housing of the connector plug. 
     The bus bars  205  are located in the connector housing so as to overlap the retaining section  405 . The retaining section  405  has a width slightly wider than any other portion of the signal contact  401  which affects a stronger coupling of the signal contacts  401  with the bus bars  205 . 
     The securing section  204  and the bus bar  205  are offset from the retaining section  405  of the signal contact  401  due to the orthogonal wall  202 , while the contact portion  201  of the ground contact  250  and the contact arm  403  of the signal contact  401  are positioned in the same plane. 
       FIG. 4   b  is a partial inverted perspective view of  FIG. 4   a , showing a set of the bussed ground contacts  200  connected integrally with bus bars  205 . A pair of signal contacts  401  is shown between the two ground contacts  250 . Two pairs of signal contacts  401  are shown in  FIG. 4   b . One pair is a signal transmitting (Tx) pair and the other pair is signal receiving (Rx) pair. The Tx and Rx pairs are separated by the central ground contact  250  to reduce crosstalk between the pairs. 
       FIG. 5   a  is an exemplary perspective view showing electrical contacts of a 12G SAS connector receptacle (without connector housing) in accordance with an embodiment of the present invention. The illustration shows three sets of the bussed ground contacts  300  each connected integrally with bus bars  305 . A pair of signal contacts  501  is provided between two ground contacts  350 , in between the channel  308  and beneath the bus bar  305 . 
     The pair of signal contacts  501  is also a pair of differential signal contacts suitable for differential signal transmission. 
     Each signal contact  501  has a curved contact portion  503  and an L-shaped terminal portion  509 . The L-shaped terminal portions  509  are connected by a retaining section  505 . The retaining section  505  has barbs on both sides thereof for securing to the connector housing of the connector receptacle. 
     The bus bars  305  are located in the connector housing so as to overlap the retaining section  505 . The retaining section  505  has a width that is slightly wider than any other portion of the signal contact  501  affecting a stronger coupling of the signal contacts  501  with the bus bars  305 . 
       FIG. 5   b  is an inverted perspective view showing electrical contacts of a 12G SAS connector receptacle with another bussed ground contact  300  connected integrally with bus bars  305 . A pair of signal contacts  501  is shown between the two ground contacts  350 . 
     Two pairs of signal contacts  501  are shown in  FIG. 5   b . Like the signal contacts  401 , one pair is signal transmitting (Tx) pair and the other pair is signal receiving (Rx) pair. The Tx and Rx pairs are separated by the central ground contact  350  to reduce crosstalk between the pairs. 
     The securing section  304  and the bus bar  305  are positioned offset from the retaining section  505  of the signal contact  501  due to the inclined wall  306 , while the contact portion  301  of the ground contact  350  and the contact portion  503  of the signal contact  501  are positioned in the same plane. 
       FIG. 6   a  is a partial perspective view of a housing  600  for a conventional 12G SAS connector plug. Along an elongate or lateral direction of the housing  600 , the housing  600  has a plurality of series  605 ,  607  of channels  601 ,  603 . Each series  605 ,  607  has three channels  601  for receiving the ground contacts (not shown) and four channels  603  for receiving the signal contacts (not shown). The channels  601 ,  603  are positioned in the direction parallel to the lateral direction of the housing  600 . The channels  601  are positioned at ends and the center of each series  605 ,  607  while a pair of channels  603  are positioned in between the channels  601 . 
       FIG. 6   b  is a partial perspective view of a housing for a 12G SAS connector plug in accordance with an embodiment of the invention. Along an elongate or lateral direction of the housing  650 , the housing  650  comprises a plurality of series  606 ,  608  of channels  610 ,  620 . Each series  606 ,  608  has three channels  610  for receiving the ground contacts  250  as shown in  FIG. 2 ,  FIG. 4   a  and  FIG. 4   b  and four channels  620  for receiving the signal contacts  401  as shown in  FIG. 4   a  and  FIG. 4   b . The channels  610 ,  620  are positioned in the direction parallel to the lateral direction of the housing  650 . The channels  610  are positioned at ends and the center of each series  606 ,  608 , while a pair of channels  620  are positioned in between the channels  610 . 
     Unlike the conventional housing  600 , the channels  610  for receiving the ground contacts  250  are joined together by connection channels  630  extending between the two ends of each series  606 ,  608 . The dimensions of the connection channels  630  are appropriately chosen to accommodate the bus bar  205  as shown in  FIG. 2 . 
       FIG. 7   a  is a partial perspective view of a housing  700  for a conventional 12G SAS connector receptacle. Along a lateral direction of the housing  700 , the housing  700  has a plurality of series  705 ,  707  of channels  701 ,  703 . Each series  705 ,  707  has three channels  701  for receiving the ground contacts (not shown) and four channels  703  for receiving the signal contacts (not shown). The channels  701 ,  703  are positioned in the direction parallel to the lateral direction of the housing  700 . The channels  701  are positioned at ends and the center of each series  705 ,  707 , while a pair of channels  703  are positioned in between the channels  701 . 
       FIG. 7   b  is a partial perspective view of a housing for a 12G SAS connector receptacle in accordance with an embodiment of the present invention. Along an elongate or lateral direction of the housing  750 , the housing  750  has a plurality of series  706 ,  708  of channels  710 ,  720 . Each series  706 ,  708  has three channels  710  for receiving the ground contacts  350  as shown in  FIGS. 3 ,  5   a  and  5   b  and four channels  720  for receiving the signal contacts  501  as shown in  FIGS. 5   a  and  5   b . The channels  710 ,  720  are positioned laterally along the housing  750 . The channels  710  are positioned at ends and the center of each series  706 ,  708 , while a pair of channels  720  is positioned in between the channels  710 . 
     Unlike the conventional housing  700 , the channels  710  are joined together by connection channels  730  extending between the two ends of each series  706 ,  708 . The dimensions of the connection channels  730  are appropriately chosen to receive the bus bar  305  as shown in  FIG. 3 . 
       FIG. 8  is a flowchart illustrating a method of fabricating an electrical connector according to an exemplary embodiment. 
     At step  801 , a copper alloy strip is provided for fabricating the electrical contacts  250 ,  350 ,  401 ,  501 . At step  803 , the copper alloy strip stamped to obtain the basic configuration of the electrical contacts  250 ,  350 ,  401 ,  501 . At step  805 , a forming process is applied to obtain a desired shape required for each of the electrical contacts  250 ,  350 ,  401 ,  501 . These contacts  250 ,  350 ,  401 ,  501  are then subjected to a plating process at step  807  to obtain the final configuration of the electrical contacts  250 ,  350 ,  401 ,  501  at step  809 . 
     At step  811 , a high temperature thermoplastic resin is provided and in a molding process  813  to fabricate the housing  650 ,  750  of the electrical connector. At step  820 , the electrical contacts  250 ,  350 ,  401 ,  501  obtained at step  809 , are assembled into respective channels  610 ,  620 ,  710 ,  720 . The respective channels  610 ,  620 ,  710 ,  720  are provided in the housing  650 ,  750  of the electrical connector to obtain the electrical connector at step  830 . 
     It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the present invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. 
     For example, the securing sections may be integrally connected by the bus bar at any location other than the center thereof. 
     The plug and receptacle of the electrical connector may include a series of electrical contacts at various pitches, for example, a pitch of 0.8 mm or 1.27 mm. 
     The electrical contacts  250 ,  350 ,  401 ,  501  of the plug and receptacle of the electrical connector may be fabricated using copper alloy as an example. 
     The electrical contacts  250 ,  350 ,  401 ,  501  of the plug and receptacle of the electrical connector may be obtained by a stamping process as shown in  FIG. 8 . 
     The housing of the plug and receptacle of the electrical connector may be fabricated using a high temperature thermoplastic material by an injection molding process. 
     Solder feet or pads (not shown) used in the receptacle of the electrical connector may be obtained by using (e.g. a copper alloy) a stamping process.