Abstract:
A telecommunications connector includes a plug having plug contacts; an outlet having outlet contacts, the plug contacts making physical and electrical contact with the outlet contacts on a top surface of the outlet contacts; a compensation contact positioned beneath a bottom surface of the outlet contacts, the compensation contact being proximate to a location where the plug contacts make physical contact with the outlet contacts, the compensation contact providing crosstalk compensation for the telecommunications connector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional patent application 60/798,785, filed May 8, 2006, the entire contents of which are incorporated herein by reference. 

   BACKGROUND 
   This application is related to U.S. patent application Ser. No. 10/716,808, the entire contents of which are incorporated herein by reference. 
   Embodiments of the invention relate to improving NEXT, FEXT, balance (TCl, TCTL) and return loss in terms of magnitude and upper frequency limits of transmission components and products. Embodiments of the invention are techniques used to apply compensation at the point of the NEXT noise sources. Standard compensating techniques involving inductive and capacitive coupling to cancel crosstalk (NEXT or FEXT) can only achieve limited success due to the limits defined by the TIA and IEC in terms of the magnitude and phase for both NEXT and FEXT of qualification plugs. In addition, standard compensation techniques are usually applied away from the outlet/plug interface which is the major contributor to crosstalk. As performance requirements are pushed beyond 100 and 250 MHz up to and above 500 MHz, canceling the crosstalk at the source becomes more critical. ANSI/TIA/EIA-568-B.2-1 is represented in Table 1 below defines the magnitude and phase requirements for category  6  test plugs. As an example, the TIA specifies the case  1  plug to have a specified magnitude (36.4 at 100 MHz) and phase −90±1.5*f/100. The component/connector design (outlet/PCB and cable termination area) must cancel this. In essence it must have the same magnitude of NEXT, but opposite phase, +90 degrees as shown in  FIG. 1 . 
   In reality it is difficult to match this phase perfectly. To match perfectly, one can imagine folding the plot in  FIG. 1  in half, the +90 and −90 lines would fall on each other and cancel each other out. 
   In a perfect match, where magnitude and phase are equivalent and applied at the point of the NEXT source, the resulting NEXT is at the noise floor, virtually nonexistent.  FIG. 2  shows the plug/outlet interface  10  and the PCB/cable termination area  12 . A plug  14  is mated with an outlet  16  mounted to PCB  18 . A connecting block  20  is mounted to the PCB  18  as known in the art. Signals travel along a path including plug  14 , outlet  16 , PCB  18  and connecting block  20  at which cables are terminated. If we consider the outlet/plug area  10  as the primary offending crosstalk contributor, the PCB/cable termination area  18  typically compensates for this offending crosstalk. 
   In most existing design implementations, the compensating crosstalk cannot be added/applied at the point of origin, that is the plug/outlet interface  10 . Typically, compensating crosstalk is added on the PCB and cable termination area  12 . Unfortunately, it is difficult, if not impossible, to replicate the exact magnitude and phase of the offending crosstalk throughout the frequency range. There is a phase shift due to the distance from the plug/outlet interface  10  to where the compensating crosstalk is applied. It should be noted, the geometry and location of the outlet contacts that go from the outlet/plug interface  10  to the PCB (or outlet to connecting block in a lead frame design) may affect the magnitude and phase of the offending crosstalk. Therefore, the PCB  18 , cable termination area and connecting block  20  or other termination must compensate for what remains. It must also compensate when tested in both directions. In addition, the TIA and IEC specify a range of performance for the modular plugs which directly contribute to the offending crosstalk. 
   If we assume the magnitudes are equal for the crosstalk at the plug/outlet interface and the compensation on the PCB/cable termination area, but out of phase, we get a non-category  6  compliant response as shown in the 0 picosecond delay plot of  FIG. 3 . By shifting the phase via manipulating the delay as shown in  FIG. 4 , we can extend the upper frequency performance of the design without manipulating the magnitude. The key is to create the null at an area where it pulls the performance down, below the specified limit line.  FIGS. 3 and 4  show the affect of varying the delay in 20 ps intervals. The null occurs at a frequency where magnitude and phase are equal. 
   SUMMARY 
   Embodiments of the invention include a telecommunications connector including a plug having plug contacts; an outlet having outlet contacts, the plug contacts making physical and electrical contact with the outlet contacts on a top surface of the outlet contacts; a compensation contact positioned beneath a bottom surface of the outlet contacts, the compensation contact being proximate to a location where the plug contacts make physical contact with the outlet contacts, the compensation contact providing crosstalk compensation for the telecommunications connector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates plug phase and connector phase for ideal cancellation of crosstalk. 
       FIG. 2  illustrates a conventional plug/outlet interface. 
       FIG. 3  is plot of crosstalk versus frequency for different delay values. 
       FIG. 4  is a plot of phase versus frequency for different delay values. 
       FIG. 5  illustrates a plug/outlet interface in an embodiment of the invention. 
       FIG. 6  illustrates a plug/outlet interface in an alternate embodiment of the invention. 
       FIG. 7  illustrates a printed circuit board in an exemplary embodiment of the invention. 
       FIG. 8  illustrates outlet contacts in an exemplary embodiment of the invention. 
       FIG. 9  illustrates outlet contacts in an exemplary embodiment of the invention. 
       FIG. 10  illustrates outlet contacts in an exemplary embodiment of the invention. 
       FIG. 11  illustrates outlet contacts in an exemplary embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   Embodiments of the invention involve methods of compensating at the plug contact and outlet contact interface to remove the distance/delay involved in applying the compensation somewhere else on the printed circuit board (PCB) or lead frame portion of the connector. 
     FIG. 5  illustrates a first embodiment using one or more spring type compensation contacts  30  emanating from PCB  18  below the point where a plug contact  34  in plug  14  makes electrical contact with an outlet contact  32 . The spring type contact  30  rises from the PCB towards the back of the outlet and bends towards the front of the outlet  14 . The spring contacts  30  are positioned beneath the outlet contacts  32 , whereas the plug contacts  34  contact the top of outlet contacts  32 . Electrical components for providing compensating crosstalk are connected to spring contacts  30 . 
   The spring contacts  30  can be used on each contact  32  of the outlet  16  that needs compensation. The spring contacts  30  can be staggered to prevent coupling from one to the other. The spring contacts can rise from the pcb towards the back of the outlet. The spring contacts  30  are in electrical connection with PCB  18  and may be coupled to compensation traces or regions on the PCB. Placing spring contact  30  at the location where the plug contact  34  makes physical contact with the outlet contact  32  locates the compensation components close to the plug/outlet interface. This helps to control phase of the compensation as well. 
   In alternate embodiments, the spring contact  30  is insulated and interacts with the outlet contact  32  through reactance (inductance and/or capacitance). In these embodiments, the spring contact  30  provides compensation by virtue of its location proximate the plug/outlet interface and its electrical properties. In these embodiments, additional compensation may not be needed on the printed circuit board  18  as the compensation contact  30  provides the necessary compensation without the need for additional compensation elements such as traces or discrete components on the printed circuit board. 
     FIG. 6  shows an alternate embodiment where one or more spring loaded, pogo pin-type compensation contacts  40  are used to make electrical contact with outlet contacts  32 . The pogo pin-type contacts  40  are positioned beneath the outlet contacts  32 , whereas the plug contacts  34  contact the top of outlet contacts  32 . Electrical components for providing compensating crosstalk are connected to contacts  40 . For example, PCB  18  may include traces, discrete components, embedded components, etc., for compensating crosstalk. Placing contacts  40  at the location where the plug contact  34  makes physical contact with the outlet contact  32  locates the compensation components close to the plug/outlet interface. This helps to control phase of the compensation as well. 
   In alternate embodiments, the pogo pin-type contact  40  is insulated and interacts with the outlet contact  32  through reactance (inductance and/or capacitance). In these embodiments, the pogo pin-type contact  40  provides compensation by virtue of its location proximate the plug/outlet interface and its electrical properties. In these embodiments, additional compensation may not be needed on the printed circuit board  18  as the compensation contact  40  provides the necessary compensation without the need for additional compensation elements such as traces or discrete components on the printed circuit board. 
   With the compensation contact in place, compensation techniques known to the industry can be utilized by connecting to the compensation contact base. Both contacts  30  and  40  may use spring force to maintain electrical contact with outlet contacts  32 . Alternatively, contacts  30  and  40  can be insulated contacts that provide compensation from inductive and/or capacitive coupling to a specific pair. At the base of contacts  30  and  40  they would be connected to a contact directly and also with compensation techniques applied at the PCB or lead frame level as known in the industry. 
     FIG. 7  shows a printed circuit board having regions  50  of embedded capacitance, inductance and/or resistance to provide compensation. Exiting designs such as that disclosed in U.S. patent application Ser. No. 10/716,808 use traces on the PCB to provide compensation. Embodiments of this invention replace the area-intensive trace coupling technique by having an embedded capacitor, resistor and/or inductor  50  at or near the area of interest such as the base of an outlet contact. The embedded capacitor, resistor and/or inductor is formed using techniques known in the art and are used and designed to apply appropriate compensation locally avoiding issues caused by the delay associated with the added length of the compensation traces. 
     FIGS. 8 and 9  show outlet contacts in another embodiment of the invention. Four lead frame type contacts or stamped contacts are shown in  FIG. 8 . Only four contacts are shown for illustration and it is understood that additional contacts may be used. In  FIG. 8 , contacts  3  and  6  form a tip and ring pair and contacts  4  and  5  form a tip and ring pair. A distal end of contact  3  extends down towards the PCB and includes an extension  60  that passes under contacts  4  and  5  to contact  6  where an arm  62  extends for a predetermined length parallel to contact  6  to apply the appropriate crosstalk compensation. The spacing between arm  62  and contact  6  is controlled via an insulative plastic spacer or comb  64 . Alternatively, the underside of contact  6  has an insulated covering which allows arm  62  to run directly underneath (no space) contact  6 .  FIG. 9  is a side view illustrating the contacts from  FIG. 8 . Placing the arm  62  near the location where the plug contacts make contact with the outlet contacts helps to control phase of the compensation as well. 
     FIGS. 10 and 11  are perspective views of outlet contacts in an alternate embodiment. In this embodiment, the outlet includes a first set of contacts  70  positioned above a second set of contacts  72 , with an insulative sheet  74  positioned between the two sets of contacts. The upper contacts  70  make electrical contact with the plug contacts as known in the art. The second set of contacts  72  are used to provide compensation between contacts by introducing capacitance and/or inductance between contacts as desired. This configuration moves compensation to the plug-outlet interface area to reduce the effects of phase delay as discussed above. Alternatively, contacts  72  can be insulated and run directly underneath contacts  70 . They can be in direct contact or the distance can be controlled by an insulative sheet or plastic holder. The spacing as well as the material and thickness on the insulated contact are controlled to apply the appropriate amount of capacitive and/or inductive compensation. Placing the contacts  72  beneath contacts  70  near the location where the plug contacts make contact with the outlet contacts  70  helps to control phase of the compensation as well. 
   Embodiments provide key tools and concepts necessary for maximizing electrical transmission performance of various types of connecting hardware and printed circuit technologies. Connecting hardware can include modular outlets and plugs, printed circuit boards (PCBs), connecting blocks, various wire connecting devices to printed circuit boards and any combination of such items. These printed circuit technologies must comply with minimum transmission performance requirements specified by various industry standards. Standards such as International Electrotechnical Commission (IEC) IEC 60603-7-2 or -6, ANSI/TIA/EIA-568-B-2, ISO/IEC 11801, IEEE, etc. Parameters include but are not limited to, near end crosstalk (NEXT), return loss, insertion loss, and far end crosstalk (FEXT). The validation of category  5 ,  5   e ,  6  and  7  are strictly controlled and described in the appropriate ANSI/TIA/EIA and IEC standards. In the case of category  5   e ,  6  and  7  the validation is required to be performed with a strict set of validation test plugs. The performance is defined by the magnitude and phase of both the NEXT and FEXT for each pair combination 
   Table 1 shows the required ANSI/TIA/EIA category 6-plug range. The described design tools/features are used to create products that satisfy the performance requirements of these various specifications under the requirements detailed in the respective documents. The techniques described are used to accomplish these requirements and to ensure repeatable performance in limit spaces. 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
                 
               Pair 
                 
               NEXT loss magnitude 
               NEXT loss phase 
             
             
               Case # 
               combination 
               Limit 
               limit 1),4),5)   
               limit 2),3)   
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               Case 1 
               3,6-4,5 
               Low 
               ≦36.4-20log(f/100) 
               (−90 + 1.5 · f/100) ± f/100  
             
             
               Case 2 
               3,6-4,5 
               Central 
               (37.0 ± 0.2)-20log(f/100) 
               (−90 + 1.5 · f/100) ± f/100  
             
             
               Case 3 
               3,6-4,5 
               High 
               ≧37.6-20log(f/100) 
               (−90 + 1.5 · f/100) ± f/100  
             
             
               Case 4 
               1,2-3,6 
               Low 
               ≦46.5-20log(f/100) 
               (−90 + 1.5 · f/100) ± 3f/100 
             
             
               Case 5 
               1,2-3,6 
               High 
               ≧49.5-20log(f/100) 
               (−90 + 1.5 · f/100) ± 3f/100 
             
             
               Case 6 
               3,6-7,8 
               Low 
               ≦46.5-20log(f/100) 
               (−90 + 1.5 · f/100) ± 3f/100 
             
             
               Case 7 
               3,6-7,8 
               High 
               ≧49.5-20log(f/100) 
               (−90 + 1.5 · f/100) ± 3f/100 
             
             
               Case 8 
               1,2-4,5 
               Low 
                 ≦57-20log(f/100) 
               90 ± (30 · f/100) 
             
             
               Case 9 
               1,2-4,5 
               High 
                 ≧70-20log(f/100) 
               any phase 
             
             
               Case 10 
               4,5-7,8 
               Low 
                 ≦57-20log(f/100) 
               90 ± (30 · f/100) 
             
             
               Case 11 
               4,5-7,8 
               High 
                 ≧70-20log(f/100) 
               any phase 
             
             
               Case 12 
               1,2-7,8 
               Low 
                 ≦60-20log(f/100) 
               any phase 
             
             
                 
             
             
                 1) Magnitude limits apply over the frequency range from 10 MHz to 250 MHz. 
             
             
                 2) Phase limits apply over the frequency range from 50 MHz to 250 MHz. 
             
             
                 3) When the measured plug NEXT loss is greater than 70 dB, the phase limit does not apply. 
             
             
                 4) When a low limit NEXT loss calculation results in values greater than 70 dB, there shall be no low limit for NEXT loss. 
             
             
                 5) When a high limit NEXT loss calculation results in values greater than 70 dB, the high limit NEXT shall revert to a limit of 70 dB. 
             
           
        
       
     
   
   While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention.