Abstract:
The present invention provides a configuration jumper that allows the main system board of an information handling system to be configured for a plurality of population options, including on-board PCI-E integrated circuits and PCI-E integrated circuits on expansion circuit boards that are connected to the main system board by an expansion slot connector. In one embodiment of the invention, the main system board comprises a first conductor and a second conductor that is selected from a plurality of second conductors that correspond to different circuit population options. The configuration jumper is operable to connect the first connector to the selected second conductor and to provide an appropriate capacitance to ensure that the signal path defined by the first conductor, the second conductor and the internal conductor of the jumper provide a combined AC coupling capacitance that complies with the AC coupling capacitor requirements of the PCI-E protocol. In alternative embodiments of the invention the four embodiments of the configuration jumpers discussed above are used to connect first pairs of differential signal conductors to second pairs of differential signal conductors. In these embodiments, the configuration jumpers comprise capacitance compensation and impedance matching to provide a capacitance-compensated, impedance-matched passthrough for high-speed differential signals used to transmit data between a PCI-E root complex and a PCI-E integrated circuit.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to circuit boards used in information handling systems. More specifically, the present invention provides an improved method and apparatus for manufacturing information system circuit boards to support multiple configurations.  
         [0003]     2. Description of the Related Art  
         [0004]     As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes, thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use, such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.  
         [0005]     In the manufacture of information handling systems, it is common to use a main system board (motherboard) that can be configured for multiple population options, including onboard integrated circuits and integrated circuits on expansion circuit boards that are connected to the main system board via an expansion slot connector.  
         [0006]     Many of the currently available configuration options for an information handling system comprise integrated circuits that are based on the PCI Express (sometimes referred to below as “PCI-E”) protocol. PCI-E is a high-speed serial signal protocol requiring point-to-point connections. A PCI-E link is composed of one or more transmit and receive differential signal pairs. PCI-E circuit boards are required to have AC coupling capacitors between 75 and 200 nF on the transmit side of any interface for signal conductors of circuit boards connected to the main system board via an expansion slot. PCI-E integrated circuits connected directly to the main system board are not required to have the AC coupling capacitors integrated and, therefore, the system board generally will include AC coupling capacitors for both the transmit and the receive side of the link.  
         [0007]     For a the configuration wherein the PCI-E integrated circuit is mounted on an expansion circuit board that comprises an AC coupling capacitor, only a connection jumper is needed to make the proper point-to-point connection for this configuration of the system board. In the case of the onboard PCI-E device, however, AC coupling capacitors are needed in addition to the jumper. This results in PCB real estate problems, because both jumpers and capacitors must be allocated to the layout even though they may not be used.  
         [0008]     In addition to the design issues related to the AC coupling capacitors discussed above, configuration issues with respect to the main system board have been affected by the need to provide higher data bit rates. For example, high-speed differential signaling is increasingly used across multiple interfaces to provide an efficient means for transferring data for high-speed protocols, such as PCI-E.  
         [0009]     Prior art techniques for routing these high speed signals through “quick switches” or zero-ohm resistors inevitably creates an impedance discontinuity, or “impedance bump” in the routing. The impedance bump creates reflections along the signal and also degrades the intrapair differential coupling ratio, thereby increasing the effects of local EMI sources on the conductor pair. As signal routing speeds for differential signals exceed three gigabits per second (Gbps), problems with impedance mismatches and associated reflections will be exacerbated.  
         [0010]     In view of the foregoing, it is apparent that there is a need to provide a flexible configuration device that allows a main system board to be configured for a plurality of population options including onboard PCI-E integrated circuits and PCI-E expansion circuit boards that are connected to the main system board via a PCI-E compliant connector. In addition, there is a need for the circuit board configuration system to provide a means to prevent signal degradation resulting from impedance mismatching related to HSDS conductors transmitting signals at high data rates.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention overcomes the shortcomings of the prior art by providing a configuration jumper that allows the main system board of an information handling system to be configured for a plurality of population options, including on-board PCI-E integrated circuits and PCI-E integrated circuits on expansion circuit boards that are connected to the main system board by a expansion slot connector.  
         [0012]     In one embodiment of the invention, the main system board comprises a first conductor and a second conductor that is selected from a plurality of second conductors, wherein the plurality of second conductors correspond to different circuit population options. The configuration jumper is operable to connect the first conductor to the selected second conductor and to provide an appropriate capacitance to ensure that the signal path defined by the first conductor, the second conductor and the internal conductor of the jumper provide a combined AC coupling capacitance that complies with the AC coupling capacitor requirements of the PCI-E protocol.  
         [0013]     There are four embodiments of the configuration jumper of the present invention. In a first embodiment, the internal conductor of the jumper is operable to connect a first conductor to a second conductor that is coupled to a PCI-E integrated circuit on an expansion circuit board wherein the either the first conductor or the second conductor comprises an AC coupling capacitor. In this embodiment, the internal conductor does not comprise an AC coupling capacitor. In a second embodiment, the internal conductor of the jumper is operable to connect a first conductor to a second conductor that is coupled to a PCI-E integrated circuit on an expansion circuit board wherein neither the first conductor nor the second conductor comprises an AC coupling capacitor. In this embodiment, the internal conductor of the configuration jumper comprises an AC coupling capacitor. In a third embodiment, the configuration jumper is operable to connect a first conductor to a second conductor that is coupled to an integrated circuit on the main system board wherein either the first conductor or the second conductor comprises an AC coupling capacitor. In this embodiment, the internal conductor of the configuration jumper does not comprise an AC coupling capacitor. In a fourth embodiment, the configuration jumper is operable to connect a first conductor to a second conductor that is coupled to an integrated circuit on the main system board, wherein neither the first conductor nor the second conductor comprises an AC coupling capacitor. In this embodiment, the internal conductor of the configuration jumper comprises an AC coupling capacitor.  
         [0014]     In alternative embodiments of the invention, the four embodiments of the configuration jumpers discussed above are used to connect first pairs of differential signal conductors to second pairs of differential signal conductors. In these embodiments, the configuration jumpers comprise capacitance compensation and impedance matching to provide a capacitance-compensated, impedance-matched passthrough for high-speed differential signals used to transmit data between a PCI-E root complex and a PCI-E integrated circuit.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element.  
         [0016]      FIG. 1  is a general illustration of components of an information handling system in accordance with the present invention.  
         [0017]      FIG. 2  is a general illustration of a main system board comprising a configuration jumper in accordance with the present invention for selectively connecting a first conductor to a second conductor in accordance with the present invention.  
         [0018]      FIG. 3  is a generalized illustration of a PCI-E topology.  
         [0019]      FIG. 4  is an illustration of a PCI-E topology for transmitting data on first and second data paths having AC coupling capacitors.  
         [0020]      FIGS. 5   a - d  are illustrations of embodiments of the capacitance-compensating configuration jumper in accordance with the present invention.  
         [0021]      FIGS. 6-9  are illustrations of a PCI-E root complex connected to an onboard PCI-E integrated circuit or a PCI-E integrated circuit on an expansion circuit board using the embodiments of the capacitance-compensating configuration jumpers illustrated in  FIGS. 5   a - d.    
         [0022]      FIG. 10  is an illustration of an implementation of an impedance-matched, capacitance-compensated configuration jumper of the present invention in a high speed differential signaling system for transmitting data from a transmitter to two possible receivers.  
         [0023]      FIG. 11  is an illustration of an impedance-matched, capacitance-compensated configuration jumper used to connect a first differential conductor pair on a circuit board to a second differential conductor pair associated with an expansion slot connector.  
         [0024]      FIG. 12  is an illustration of an impedance-matched, capacitance-compensated configuration jumper for connecting a first differential conductor pair on a circuit board to a second differential conductor pair associated with an onboard PCI-E circuit.  
         [0025]      FIG. 13  is an illustration of a configuration of conductor pads for a first differential signal input conductor pair and first and second differential signal output conductor pairs.  
         [0026]      FIG. 14   a  is an illustration of an impedance-matched, capacitance-compensated configuration jumper operable to connect a first differential signal input conductor pair to a first differential signal output conductor pair in accordance with the conductor configuration shown in  FIG. 13 .  
         [0027]      FIG. 14   b  is an illustration of an impedance-matched, capacitance-compensated configuration jumper operable to connect a first differential signal input conductor pair to a second differential signal output conductor pair in accordance with the conductor configuration shown in  FIG. 13 .  
         [0028]      FIG. 15  is an illustration of a configuration of conductor pads and associated ground pads for a first differential signal input conductor pair and first and second differential signal output conductor pairs.  
         [0029]      FIG. 16   a  is an illustration of an impedance-matched, capacitance-compensated configuration jumper operable to connect a first differential signal input conductor pair to a first differential signal output conductor pair using the conductor configuration illustrated in  FIG. 15 .  
         [0030]      FIG. 16   b  is an illustration of an impedance-matched, capacitance-compensated configuration jumper operable to connect a first differential signal input conductor pair to a second differential signal output conductor pair using the conductor configuration illustrated in  FIG. 15 .  
         [0031]      FIG. 17  is an illustration of layout geometries for conductor pads to create 100 ohms of differential impedance.  
         [0032]      FIG. 18  is an illustration of layout geometries of a plurality of conductors embedded in a substrate with a predetermined spacing from a groundplane. 
     
    
     DETAILED DESCRIPTION  
       [0033]     The method and apparatus of the present invention provides significant improvements in the manufacture and use of circuit boards such as those used in an information handling system  100  shown in  FIG. 1 . For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components.  
         [0034]     Referring to  FIG. 1 , the information handling system  100  includes a main system board  102  that comprises a processor  104  and various other subsystems  106  understood by those skilled in the art. Data is transferred between the various system components via various data buses illustrated generally by bus  103 . A hard drive  110  is controlled by a hard drive/disk interface  108  that is operably connected to the hard drive/disk  110 . Likewise, data transfer between the system components and other storage devices  114  is controlled by storage device interface  112  that is operably connected to the various other storage devices  114 , such as CD ROM drives, floppy drives, etc. An input/output (I/O) interface  116  controls the transfer of data between the various system components and a plurality of input/output (I/O) devices, such as a display  122 , a keyboard  124 , a mouse  126 .  
         [0035]      FIG. 2  is a generalized illustration of a printed circuit board such as the main system board (or motherboard)  102  discussed above in connection with  FIG. 1 . The circuit board  102  comprises a plurality of expansion card slots  128  that can connect expansion circuit boards, such as circuit board  130 , to enhance the functionality of the information handling system  100 . In an embodiment of the present invention, the expansion slots  128  communicate with the other system components over a bus that conforms to the PCI-Express protocol in accordance with the PCI-Express Base Specification Revision 1.0, published on Jul. 22, 2002 (the “PCI-Express Specification”).  
         [0036]     For manufacturing efficiency, it is desirable to fabricate a main system board  102  circuit board with a plurality of conductors that can be connected (or left unconnected) to configure the circuit board for a particular application. A jumper can be used during the manufacturing process to connect a first conductor pair carrying data signals to a second conductor pair to route signals to various system components in accordance with a predetermined configuration. For example, a jumper or combination of jumpers, illustrated generally by reference numeral  132 , can be used to connect the conductor pair  134  to conductor pair  136  to transmit signals to a specific destination, such as an on-board PCI-Express circuit  140 . Alternatively, the jumper  132  can be used to connect the conductor pair  134  to conductor pair  142  to transmit signals to a PCI-Express circuit  144  on the expansion circuit board  130 .  
         [0037]     As was discussed hereinabove, PCI-E circuit boards are required to have AC coupling capacitors on the transmit signal conductors of the circuit board. In particular, the AC coupling capacitor requirements are described in Chapter 4 of the PCI Express Card Electromechanical Specification Revision 1.1, Mar. 28, 2002, which by this reference is incorporated for all purposes.  
         [0038]     For PCI-E devices that transmit data high data rates over high speed differential signal (HSDS) conductor pairs, there is the additional need to provide a matched impedance solution for the configuration jumpers used to configure the main system circuit boards. The various embodiments of the configuration jumper of the present invention described below provide a solution to both of these design requirements. Specifically, some of the embodiments of the configuration jumpers described below can be used to provide the required capacitors for use with PCI-E devices—with differential signal conductors or with non-differential conductors. Other embodiments of the configuration jumper provide both the required PCI-E coupling capacitors and impedance matching for use with HSDS differential conductor pairs operating at high data transmission rates.  
         [0039]      FIG. 3  is an illustration of a PCI-E topology wherein first and second PCI-E devices  150  and  154  transmit data over a plurality of differential conductors that define transmission “lanes.” As illustrated in  FIG. 4 , one of the PCI-E devices  144  can be on the expansion board  130  that is connected to the main system board  102  via the PCI-E connector  128 . In the topology illustrated in  FIG. 4 , the respective signal transmission paths between the transmitters and receivers comprise a plurality of coupling capacitors. Typically, the coupling capacitors reside on the circuit board where the transmitter of the device is located. For example transmitter  154  transmits signals to receiver  156  over a transmission path that comprises coupling capacitors  162 . Likewise, transmitter  158  transmits signals to receiver  160  over a transmission path comprising coupling capacitors  162 . While the capacitors typically are located on the circuit board where the PCI-E devices located, it is possible to locate the coupling capacitors elsewhere, such as the configuration jumper of the present invention.  
         [0040]      FIGS. 5   a - d  illustrate a plurality of capacitance-compensated configuration jumpers  132   a - d  that can be used to configure a main system board to selectively couple a PCI-E root complex  172  to an onboard PCI-E circuit  144  or to an expansion slot  128 . For example, in the embodiment of the invention illustrated in  FIG. 5   a , the PCI-E root complex  170  is coupled by configuration jumper  132   a  to the expansion slot  128 . In the embodiment illustrated in  FIG. 5   b , the PCI-E root complex  170  is operably coupled to the onboard PCI-E circuit  144 . In the embodiments illustrated in  FIGS. 5   a  and  5   b , the configuration jumpers  132   a  and  132   b  do not comprise AC coupling capacitors.  FIGS. 5   c  and  5   d  illustrate configuration wherein the configuration jumpers  132   c  and  132   d  comprise coupling capacitors  162  that provide capacitance matching in accordance with the PCI-Express standard. As used herein, “capacitance-compensated” refers to a predetermined capacitance or a jumper that is selected to optimize signal transmissions for a particular application, such as for the AC coupling requirements for PCI-Express.  
         [0041]     Additional details relating to the various embodiments of the configuration jumpers  132   a - d  can be seen by referring to  FIGS. 6-9 . In the embodiment illustrated in  FIG. 6 , an expansion circuit board  130  comprises a PCI-E circuit  144  that is operably connected to the PCI-E expansion connector  128 . The transmit signal conductor  171  of the PCI-E circuit  144  comprises an AC coupling capacitor  162 . Since the transmit signal conductor  171  comprises an AC coupling capacitor, the configuration jumper  132   a  does not comprise a coupling capacitor. The transmit signal conductor  172  from the PCI-E root complex  170  also comprises a coupling capacitor (on the main system board  102 ) and, therefore, this conductor is connected to the PCI-E circuit  144  by a jumper  132   a  that does not comprises a coupling capacitor.  
         [0042]     In the embodiment of the invention illustrated in  FIG. 7 , the PCI-E root complex  170  is coupled to a PCI-E circuit  140  that is on the main system board  102 . In this embodiment, the transmit conductor  173  of the PCI-E circuit  140  does not comprise an AC coupling capacitor. Therefore, the jumper  132   c  used to connect the conductor  173  to the PCI-E root complex comprises an AC coupling capacitor  163 . The transmit conductor  172  from the PCI-E root complex  170  comprises a coupling capacitor  162  (on the main system board) and, therefore, a configuration jumper  132   d  without an AC configuration capacitor is used to connect the transmit conductor  172  to the onboard PCI-E circuit  140 .  
         [0043]     In the embodiment illustrated in  FIG. 8 , an expansion circuit board  130  comprises a PCI-E circuit  144  that is operably connected to the PCI-E expansion connector  128 . The transmit signal conductor  171  of the PCI-E circuit  144  comprises a coupling capacitor  162 . Since the transmit signal conductor  171  comprises an AC coupling capacitor, the configuration jumper  132   a  does not comprise a coupling capacitor. The transmit signal conductor  172  from the PCI-E root complex  170  does not comprise a coupling capacitor and, therefore, this conductor is connected to the PIC-E circuit  144  by a jumper  132   b  that comprises a coupling capacitor  162 .  
         [0044]     In the embodiment of the invention illustrated in  FIG. 9 , the PCI-E root complex  170  is coupled to a PCI-E circuit  140  that is on the circuit board  102 . In this embodiment, the transmit conductor  173  of the PCI-E circuit  140  does not comprise an AC coupling capacitor. Therefore, the jumper  132   c  used to connect the conductor  173  to the PCI-E root complex comprises an AC coupling capacitor  163 . The transmit conductor  172  from the PCI-E root complex also does not comprise an AC coupling capacitor. Therefore another configuration jumper  132   c  with an AC coupling capacitor  162  is used to couple the transmit conductor  172  to the onboard PCI-E circuit  140 .  
         [0045]     Although not explicitly shown in  FIGS. 5   a - 5   d , and  FIGS. 6-9 , the various conductors used to connect the PCI-E root complex  170  to the PCI-E circuit  144  on the expansions board  130  or to the on-board PCI-E circuit  140  are differential signal pairs. Furthermore, it should be understood that differential signal pairs comprising a capacitor  162  will have a capacitor on each of the individual conductors in the differential signal pair.  
         [0046]      FIG. 10  is an illustration of an embodiment configuration jumper  132   e - j  of the present invention wherein the configuration jumper comprises the AC coupling capacitors required for PCI-E devices and also provides matched-impedance to minimize problems associated with high data rate transmissions in a point-to-point high speed differential signaling (HSDS) configuration. In the embodiment illustrated in  FIG. 10 , an HSDS driver  180  transmits data to one of two possible receivers  182   a  or  182   b . The capacitance-compensated, impedance-controlled jumper  132   e - j  is operable to connect the differential conductor pair  184  with the differential conductor pair  186  or the differential conductor pair  188  depending on the configuration of the information handling system.  
         [0047]     As will be understood by those of skill in the art, the differential signaling protocol provides for a positive signal to be placed on one conductor and a negative signal to be placed on the other conductor of the differential conductor pair. In most configurations for point-to-point data transmission, the characteristic impedance Z 0  of the differential conductor pair is 100 ohms. The HSDS configuration shown in  FIG. 10  is an illustrative example of a data transmission system wherein embodiments of the capacitance-compensated, matched-impedance jumper of the present invention can be used to improved data transmission. While this specific example has been illustrated for discussion purposes, the present invention can be used to improve data transmission in any system employing differential signaling techniques.  
         [0048]     Specific embodiments for the matched-impedance jumper  132   e - j  of the present invention are illustrated in more detail below in  FIGS. 11-18 . As will be understood by those of skill in the art, matched-impedance refers to the condition in which the impedance of a component or circuit is equal to the internal impedance of the source, or the surge impedance of a transmission line, thereby giving maximum transfer of energy from source to load, minimum reflection, and minimum distortion. The signal loss associated with the reflection of signals resulting from an impedance mismatch is determined by the reflection coefficient, Γ, that can be calculated using following formula:  
         Γ   =         v   r       v   i       =         z   t     -     z   0           z   t     +     z   0             ;       
 
         [0049]     where:  
         [0050]     v r =reflected voltage  
         [0051]     V i =incident voltage  
         [0052]     z t =termination impedance  
         [0053]     z o =characteristic impedance  
         [0054]     Other factors relating to impedance matching include: 1) the size and shape of the signal conductors, 2) the material used to make the conductors, 3) the spacing between the conductors, 4) the size and type of ground associated with the conductors, 5) the distance between the conductors and the ground, and 6) the effective dielectric constants of the operating environment (e.g., air) and materials used to manufacture the circuit board and substrate materials used in the jumper. In accordance with the present invention, each of the aforementioned factors is optimized to provide an impedance-matched jumper to provide optimum signal transmission.  
         [0055]     Referring to  FIG. 11 , a PCI-E root complex  170  with differential signaling capability is connected to an impedance-matched jumper  132   e  that comprises capacitance compensation and internal impedance-matched conductors to transmit the signals to a differential conductor pair  186  connected to an expansion slot  128  as illustrated above in  FIG. 2 . In the embodiment illustrated in  FIG. 12 , the PCI-E root complex  170  is connected by a capacitance-compensated, impedance-matched jumper  132   f  to differential conductor pair  188  that is coupled to an onboard PCI-E circuit  140  as illustrated in  FIG. 2 . In the various embodiments of the present invention, the capacitance-compensated, impedance-matched jumper  132   e - j  is a passive connector having improved signal transmission characteristics to facilitate high data transmission rates. The internal capacitance-compensated, impedance-matched conductors of jumpers  132   e - j , therefore, do not comprise any active components, such as FETs, and are fixed in one of the two configurations illustrated in  FIGS. 11 and 12 . While the impedance-matched jumpers  132   e - j  shown in  FIGS. 11 and 12  are described as being adapted to connect the first differential pair  184  to one of two possible secondary differential pairs  186  or  188 , the present invention can be adapted to connect the first differential pair  184  to a secondary differential pair selected from a plurality (i.e., two or more) possible secondary differential pairs.  
         [0056]      FIG. 13  is an illustration of connection pads for the various conductor pairs illustrated in  FIGS. 11 and 12 . As can be seen in  FIG. 13 , differential conductor pair  184  is connected to a “signal +” and a “signal −” pad. The receiver differential conductor pair  186  is connected to a “signal A+” and a “signal A−” pair of conductor pads. Likewise, receiver conductor pair  188  is connected to “signal B+” and “signal B−” conductor pads.  
         [0057]     The embodiments of the impedance-matched jumpers  132   g  and  132   h  shown in  FIGS. 14   a  and  14   b , respectively, have connectors that are designed to attach to the corresponding pads shown in  FIG. 13  to provide a capacitance-compensated, matched-impedance connection. Each of the embodiments of the capacitance-compensated, impedance-matched jumper provides internal conductors to transmit signals between the respective connector pads with minimal signal degradation. In particular, as discussed in greater detail below, the pad spacing and the conductor placement within the impedance-matched jumper provides a matched-impedance pass-through connector. Referring to  FIG. 14   a , the capacitance-compensated, impedance-matched jumper  132   g  comprises first and second internal conductors  190   a  and  190   b  that connect transmit connection pads “Sig +” and Sig −” to receive connection pads “Sig A+” and “Sig A−.” The impedance-matched jumper  132   h  shown in  FIG. 14   b  comprises first and second internal conductors  190   c  and  190   d  that connect transmit connection pads “Sig +” and Sig −” to receive connection pads “Sig B+” and “Sig B−.” 
         [0058]      FIGS. 15 and 16   a,b  illustrate an embodiment of the invention that provides enhanced bandwidth by adding a plurality of ground connection pads at predetermined locations with respect to the differential signal conductor pairs. As can be seen in  FIG. 15 , each of the connection pads for the transmit and receive differential conductor pairs are adjacent to a ground pad. The capacitance-compensated, impedance-matched jumpers  132   i  and  132   j  shown in  FIGS. 16   a  and  16   b , respectively, have connectors that are designed to attach to the corresponding differential signal pads and ground pads shown in  FIG. 15  to provide an enhanced matched-impedance connection. Using the embodiment of the invention shown in  FIGS. 15 and 16   a,b  it is possible to control impedance more than +/−15% of the requirements for current 3 Gbps signal transmission standards and higher signal transmission speeds in the future.  
         [0059]      FIG. 17  shows example geometries for conductor pads  190   a  and  190   b  to create 100 ohms differential impedance in the various embodiments of the impedance controlled jumper of the present invention. The embodiment shown in  FIG. 17  comprises 10-mil pads  190   a  and  190   b  on a 20-mil pitch spaced 10 mils above a ground  192 . Above a 10-mil dielectric  194 , the pads illustrated in  FIG. 17  will create an impedance of 100 ohms.  FIG. 18  shows example geometries of 8 mil conductors  190   a  and  190   b  embedded in a plastic substrate  196  and spaced 6 mils above a 10 mil dielectric  198  and a total of 16 mils above a ground  192 . The examples of connector pads and internal conductors discussed above are representative examples of geometries that can provide improved differential signal performance in accordance with the present invention, but other geometries can be implemented in the scope of the present invention.  
         [0060]     While the various embodiments of the invention as discussed hereinabove have been described in connection with differential signaling conductors, the advantages of the present invention can also be applied to other configurations, including single-ended conductors. Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.