Abstract:
An interchangeable impedance tuner for use in an electrical connector has been provided. The tuner is formed of a dielectric material different than air. The interchangeable impedance tuner may include a plurality of dielectric isolation ribs, wherein a dielectric rib is positioned between two adjacent signal and/or ground contacts. The tuner may also include at least one impedance adjusting metal insert and at least one insert receptacle for slidably receiving the impedance adjusting metal insert. Each impedance adjusting metal insert is oriented parallel to a portion of the contacts. Further, each impedance adjusting metal insert overlaps a portion of one of the differential pairs. A shell covering the housing and the tuner. The shell opens to allow removal of the tuner is also provided. Upon removal of one tuner, a different tuner, having different impedance controlling characteristics may be positioned within the cavity of the electrical connector.

Description:
BACKGROUND OF THE INVENTION 
     Certain embodiments of the present invention generally relate to a connector for electronic equipment, and more particularly to a connector including an interchangeable tuner for controlling the impedance within the connector. 
     Connectors are known for interconnecting various electrical media, components, and structures such as printed circuit boards (PCB), coaxial cables, discrete circuit components, flex circuits and the like. The connectors may interconnect signal and/or power lines between two similar or different media, components and structures, such as between a flex circuit and a PCB, between two PCBs and the like. An example of an interconnection between two PCBs is a board-to-board connector. Connectors are offered in a variety of shapes and sizes, depending upon several competing criteria. Within connectors, the shape, size and spacing between contacts also greatly varies. As the shape, size and spacing of the contact changes, so does the impedance exhibited by the contacts. 
     Today, connectors are being proposed with more and more signal lines within smaller and smaller connector envelopes. Such size reductions and capacity increases have resulted in very close spacing between adjacent contacts within a connector. As contacts became more closely spaced, when carrying high speed signals, adjacent contacts begin to electrically couple with one another. Electrical coupling occurs when one contact becomes influenced by the electromagnetic field produced by an adjacent contact. Electrical coupling causes, among other things, the contacts to exhibit different impedance characteristics than they might otherwise exhibit absent any coupling. Until recently, impedance exhibited by a connector did not degrade performance by an appreciable amount, in part because signal/data transmission rates were relatively low (e.g., less than 500 MHz or 1 Gbits per second). However, newer electronic and electrical systems have been proposed that are able to transmit data signals at speeds approaching and exceeding 1 GHz or 2 Gbits per second. Because the speed of data transmission systems continues to increase, while the physical size of components continues to decrease, even small increases in impedance may pose significant problems, such as signal loss, within a connector and the system. 
     Many board-to-board systems have been proposed that include connectors that apply differential pairs of signals. Differential signal pairs include complimentary signals such that if one signal in a differential pair switches from 0 V to 1 V, the other signal in the differential pair switches from 1 V to 0 V. Differential pair connectors have been proposed that control impedance by using a predetermined contact-to-contact spacing (e.g., a distance between signal contacts of a differential pair). Impedance is affected by contact-to-contact spacing because impedance increases as capacitance decreases. Capacitance increases as the distance decreases between a signal contact, or tail, and ground or other signal contacts, or contacts. Hence, impedance decreases with decreased contact-to-contact spacing. Conversely, impedance increases with increased contact-to-contact spacing. Therefore, signal contacts of conventional systems are positioned a predetermined distance from adjacent signal contacts in order to yield a desired impedance. 
     As the distance increases between two contacts in a differential pair or otherwise, the contacts are considered to be “loosely coupled” to one another. Similarly, as the distance is decreased between contacts in a differential pair or otherwise, the contacts are considered to be more “tightly coupled” to one another. Loosening the coupling of signal contacts of a differential pair increases the impedance exhibited at the contacts, while tightening the coupling between signal contacts in a differential pair decreases the impedance. 
     Increasing the distance between signal contacts of a differential pair also increases the interference, noise and jitter experienced by the signals carried through circuit boards, the connector and contacts. For example, as a signal contact of a differential pair is displaced further from its complimentary signal contact, the signal contacts of one differential pair may become coupled to signal contacts of a different differential pair. As signal contacts of separate differential pairs become coupled to one another, the signal contacts begin to exhibit cross-talk with each other. That is, loosening the coupling between complimentary signal contacts may tighten the coupling between non-complimentary signal contacts. Tightening the coupling between non-complimentary signal contacts increases cross-talk between the contacts. Consequently, interference, noise, and jitter within the multi-layer circuit board, connector and system increases. Therefore, increasing the distance between signal contacts to increase the impedance within a particular differential pair causes a higher degree of interference, noise and jitter. Conversely, decreasing the distance between signal contacts of a differential pair to decrease the amount of interference, noise and jitter may produce a non-uniform or otherwise non-suitable impedance. 
     A need remains for an improved electrical connector capable of controlling impedance within desired levels. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with an embodiment of the present invention, a connector assembly has been developed that includes a connector housing having a contact retaining chamber at one end of the connector housing, at least two signal contacts arranged as a differential pair and held in the contact retaining chamber of the connector housing. The signal contacts are separated by a gap. The assembly also includes an impedance tuner block formed of a dielectric material insertable into the contact retaining chamber. The impedance tuner block has at least two channels notched therein. The impedance tuner block includes isolation layers separating the channels. Each channel receives a corresponding one of the signal contacts and each isolation layer is inserted between adjacent signal contacts when the impedance tuner block is inserted into the contact retaining chamber. 
     The impedance tuner block may also include a plurality of isolation ribs as the isolation layers. One isolation rib is positioned between two adjacent contacts. Optionally, the connector assembly may further include ground contacts separating the differential pairs from one another. The differential pairs may be separates from the ground contacts by the isolation ribs. 
     The connector assembly further includes at least one impedance adjusting insert securable to the impedance tuner block in a position that is oriented parallel to at least central elongate arms of the signal contacts. The impedance adjusting inserts may be formed of a non-ferrous metal. 
     Further, embodiments of the present invention include a shell covering the housing and the impedance tuner. The shell opens to allow removal of the impedance tuner. Upon removal of one impedance tuner, a different impedance tuner, having different impedance controlling characteristics may be positioned within the cavity of the electrical connector. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is an isometric view of a receptacle connector formed in accordance with an embodiment of the present invention. 
     FIG. 2 is an isometric view of an impedance tuner formed in accordance with an embodiment of the present invention. 
     FIG. 3 is an isometric view of an impedance tuner formed in accordance with an embodiment of the present invention. 
     FIG. 4 is an isometric view of an impedance tuner with metallic inserts formed in accordance with an embodiment of the present invention. 
     FIG. 5 is an isometric view of an impedance controlled connector assembly  500  formed in accordance with an embodiment of the present invention. 
     FIG. 6 is an isometric view of an impedance controlled connector assembly  500  formed in accordance with an embodiment of the present invention. 
    
    
     The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an isometric view of a receptacle connector  100  formed in accordance with an embodiment of the present invention. The receptacle connector  100  includes a housing  110  having a main body  110 , and sidewalls  111 , a back wall  117  and a base  115  that define a cavity  120  at an open face of the housing  110 . Contact passages  128  are formed in the open end of the base  115 . Ground contacts  122  extend from the back wall  117 . Each ground contact  122  has a ground contact tail  133  at a terminal end. Similarly signal contacts  126  extend from the back wall  117 , and each signal contact  126  has a signal contact tail  137  at a terminal end. The signal and ground contacts  126  and  122  carry differential pair data signals at high speeds, such as 2 Gbits per second, 5 Gbits per second, 10 Gbits per second and the like. 
     Signal and ground contacts  126  and  122  are interspersed with two (2) signal contacts  126  being adjacent one another, thereby forming a differential pair  124 . Adjacent differential pairs  124  are separated from one another by a ground contact  122 . As shown in FIG. 1, each signal and ground contact  126  and  122  includes an elongated central arm  136  and  132 , respectively, with an arc shaped contact tail  137  and  133 , respectively, on a lower end thereof. Each signal contact  126  and ground contact  122  also includes signal and ground lead contact sections  146  and  142 , respectively, at the upper end opposite that of the arc shaped contact tails  137  and  133 . Each signal and ground contact tail  137  and  133  curves below and outward from a contact passage  128 . The contact passages  128  are separated by a series of sections  149  having beveled outer tips. The signal contacts  126  in each differential pair  124  are spaced apart by a width W D  that includes the width of each signal contact  126  plus the space between the signal contacts  126 . 
     The connector  100  also includes a shell (not shown) that covers the housing  110  and cavity  120 . The end  103  of the receptacle connector  100  opposite the cavity  120  is received by a plug connector (not shown) having signal and ground contacts (not shown) that connect to the signal contacts  126  and ground contacts  122 , respectively, through intermediate signal and ground portions (not shown), respectively. The plug connector, in turn, connects to an electrical cable (not shown) that allows signals to pass from the plug connector to the cable and ultimately to an electrical component (not shown), and vice versa. 
     FIGS. 2 and 3 are isometric views of an impedance tuner  200  formed in accordance with an embodiment of the present invention. The impedance tuner  200  includes a rectangular molded housing  201  having top, bottom, side, front and back walls  208 ,  220 ,  214 ,  216  and  222  and an insert dividing wall  224 . The impedance tuner  200  also includes plank shaped insert receptacles  202  formed and angled within the front wall  216 . The insert receptacles  202  include retaining bases  218  at lower ends of the receptacles  202  and insertion slots  318  having notches  206  formed in the top wall  208  and extending downward therefrom. The insert receptacles  202  receive and retain impedance adjusting inserts (discussed below with respect to FIG.  4 ). Thus, the insert receptacles  202  conform to the shape of the impedance adjusting inserts (reference numeral  402  in FIG.  4 ). As shown in FIGS. 2 and 3, the notches  206  extend less than half the distance from the top wall  208  to the retaining bases  218 . The insert receptacles  202  are separated by the insert dividing wall  224  having a reduced portion  320  between the two notches  206 . 
     As shown in FIG. 3, The impedance tuner  200  also includes dielectric isolation walls, or ribs  302  formed within the back wall  222 . Upon insertion of the impedance tuner  200  into the connector  100 , the ribs  302  separate signal and ground contacts  126  and  122  from one another. The ribs  302  define contact channels  301  that extend into the housing  201  from the back wall  222 . Each contact channel  301  is formed to receive a signal or ground contact  126  or  122 . The impedance tuner  200  is made of a dielectric material, such as a liquid crystal polymer material, or zenite, that has a dielectric constant greater than air. For example, zenite has a dielectric constant of 3.40 while air has a dielectric constant of 1.00. 
     FIG. 4 is an isometric view of an impedance tuner  200  with impedance adjusting inserts  402  formed in accordance with an embodiment of the present invention. The impedance adjusting inserts  402  may be a non-ferrous metal, such as brass and the like. The impedance adjusting inserts  402  have tabs  404  located on their sides, extending laterally therefrom. The impedance adjusting inserts  402 , each having a width W M , are positioned within the insert receptacles  202  such that the tabs  404  are received and frictionally retained by the notches  204 . The retaining bases  218  support the impedance adjusting inserts  402 . When the impedance tuner  200  is positioned with the connector  100 , the impedance adjusting inserts  402  are positioned over differential pairs  124 , as further discussed below. 
     FIG. 5 is an isometric view of an impedance controlled connector assembly  500  formed in accordance with an embodiment of the present invention. The assembly  500  includes the receptacle connector  100  and the impedance tuner  200 . The impedance tuner  200  is positioned within the cavity  120  such that each signal contact  126  and ground contact  122  is positioned within a contact channel  301  (shown in FIG.  3 ). Each signal contact  126  of a differential pair  124  is separated from its counterpart signal contact  126  by a dielectric isolation wall  302  (shown in FIG.  3 ). Each signal elongated central arm  136  is separated from a ground elongated central arm  132  by a dielectric isolation wall, or rib  302  (view hidden by insertion of impedance tuner  200  into receptacle connector  100 ). Each signal contact tail  137  and ground contact tail  133  protrudes from the base  115  of the receptacle  100  through a contact passage  128  and is exposed in order to contact traces (not shown) on a circuit board (not shown). 
     The impedance tuner  200  is held into position by the metallic shell (not shown) that encompasses the connector  100  and the impedance tuner  200 . Preferably, the shell is positioned and clamped around the housing  110 . The shell may open and close in order to allow one tuner  200  to be removed, and another impedance tuner  200  to be inserted into the cavity  120 . Thus, the assembly  500  may accommodate a variety of impedance tuners  200 , depending on the desired amount of impedance control. For example, an impedance tuner  200  having a first dielectric constant may be used in some applications. During a different application, the impedance tuner  200  may be removed and replaced with a second impedance tuner  200  having a different dielectric constant, or different impedance adjusting inserts  402  formed of a different metal. In other words, the impedance tuner  200  is interchangeable. 
     The insert receptacles  202  are formed within the impedance tuner  200  such that each impedance adjusting insert  402  may be positioned in a parallel plane over a corresponding differential pair  124 . The width of each impedance adjusting insert  402  is equal, or approximately equal, to the width of a differential pair  124  (W M =W D ). In any event, each impedance adjusting insert  402  completely overlaps the width of a differential pair  124 . That is, each impedance adjusting insert  402  completely overlaps a portion of a differential pair  124  (e.g., elongated central arms  136  of two signal contacts  126  of a differential pair), but does not touch the signal contacts  126  of the differential pair  124 . Rather, the impedance adjusting inserts  402  are separated from the signal contacts  126  by the molded housing  201  and/or air. That is, the impedance adjusting inserts  402  are separated from the signal contacts  126  by dielectric material. 
     The impedance adjusting inserts  402  are very closely spaced to the signal contacts  126  and ground contacts  122 , but the impedance adjusting inserts  402  do not touch the contacts  126  and  122 . The impedance adjusting inserts  402  are oriented in a plane that is parallel to the elongated central arms  136  and  132  of the signal contacts  126  and ground contacts  122  in order that the impedance adjusting inserts  402  will conform to a portion of the contacts  126  and  122 . The impedance adjusting inserts  402  may be flat metal sheets  520  that run parallel with and overlap the elongated central arms  136  and  132  of the signal and ground contacts  136  and  132 , respectively. Alternatively, each insert  402  may be a curved metal sheet  540  that conforms to a greater portion of the contacts  126  and  122  than the flat metal sheet  520 . For example, the curved metal sheet  540  may conform to the elongate central arms  136  and  132  and the signal and ground lead contact sections  146  and  142 . 
     The impedance adjusting inserts  402  are spaced apart from one another so that there is little or no coupling between them. For example, the width of the insert dividing wall  224  may be the width of a ground tail  133 , so long as each impedance adjusting insert  204  overlaps signal contacts  136  of a differential air  124 . 
     Impedance within the assembly  500  is tuned through the dielectric material of the impedance tuner  200  and the impedance adjusting inserts  402 . Impedance is represented by the following equation:        Z   =       L   C                              
     where Z is impedance, L is inductance and C is capacitance. Therefore, increasing the capacitance decreases the impedance. Decreasing capacitance increases the impedance. Capacitance, is further defined by the following equations:        C   =         Q   V                   C     =         eA   d                   e     =       e   o          e   r                                  
     where Q is the charge on a plate, V is voltage, A is the area of the plates, e o  is the permittivity of free space and e r  is the dielectric constant of the material between the plates. 
     The capacitance of a system including two plates, such as two signal contacts  126  of a differential pair  124 , or a signal tail  126  and a metal plate  402 , may be increased by the following: 
     1) Increasing the dielectric constant (e r ) of the material between the plates; 
     2) Increasing the areas (A) of the plate; or 
     3) Decreasing the separation between the plates (d). 
     In order to increase the capacitance, the dielectric material between the plates may be changed. For example, instead of the signal contacts  126  of a differential pair  124  being separated by air, the dielectric isolation walls, or ribs  302  may be placed between the signal contacts  126 , such as in the embodiments discussed above. Alternatively, however, ribs  302  may not be placed between the signal contacts  126  of a differential pair  124 . Rather, the ribs  302  may be placed only between the differential pairs  124  and the ground contacts  122 . Also, alternatively, ribs  302  may not be used. Instead, the impedance tuner  200  may have a molded housing  201  without any ribs  302 . Also, alternatively, the metal inserts  402  may not be used. Instead, the dielectric housing  201  may provide the desired amount of impedance control within the assembly  500 . However, to increase capacitance even further, a neutral piece(s), such as an impedance adjusting insert  402 , may be added to the dielectric material, such as the molded housing  201 . Also, alternatively, instead of dielectric ribs  302 , the impedance tuner  200  may include metal isolation walls, or ribs protruding from the housing  201  and positioned between all or some of the contacts  126  and  122 . 
     Thus, different impedance tuners  200  may be used within the receptacle connector  100 . Variables that affect the impedance within the system include the following: using impedance tuners  200  of different dielectric materials, varying the depths of contact channels  301 , utilizing impedance adjusting inserts  402 , varying the impedance adjusting inserts  402  among different metals having different dielectric constants, varying the distance between the impedance adjusting inserts  402  and the differential pairs  124 , and/or varying the length of the impedance adjusting inserts  402  that conforms to the signal contacts  126  and ground contacts  122 . Various impedance tuners  200  having different combinations of these variables may be used with the assembly  500 , depending on the desired amount of impedance control within the assembly  500 . Thus, impedance tuning and control through interchangeable impedance tuners  200  is provided. 
     FIG. 6 is an isometric view of an impedance controlled connector assembly  600  formed in accordance with an embodiment of the present invention. The assembly  600  includes dielectric insert  602  having contact channels  604 . The assembly  600  differs from the assembly  500  in that the dielectric insert  602  is inserted from underneath the contacts  122  and  126  through an opening  601  in the connector base, as opposed to being positioned over the contacts  122  and  126 . The contacts  122  and  126  rest on the contact channels  604 , which conform to the contours of the contacts  122  and  126 . As shown with respect to FIG. 6, the dielectric insert  602  does not include metallic inserts. 
     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. 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. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.