Patent Document

BACKGROUND  
         [0001]    1. Field Of The Invention  
           [0002]    The invention relates to board-to-board coaxial connections. More specifically, the invention relates to board-to-board coaxial connections in a computing environment.  
           [0003]    2. Background  
           [0004]    The combination of mobile computing and wireless communications is a powerful driver in the personal electronics field. Mobile computers, for example laptops, have improved connectivity with peripheral devices and the Internet through a wireless communication module. A wireless initiative to greatly improve the conductivity of mobile personal computers to the Internet and other devices is currently underway. Such an initiative requires a combination interface with both radio frequency (RF) and digital signal segments to provide conductivity, between mobile personal computers and peripheral devices. The RF segment typically contains several coaxial (“coax”) connections, each of which is capable of handling RF signals up to 6 gigahertz (GHz).  
           [0005]    Motherboards for mobile personal computers may contain within them radio frequency (RF) antennae. These antennae may be connected through the motherboard to an off board connection through microstrip lines. These microstrip lines need to be suitably engineered to provide appropriate impedance and isolation for the RF signal. Features that need to be considered in engineering RF capable microstrip transmission lines include width of line and distance between signal line and ground line and the dielectric layer separating them.  
           [0006]    An add-on radio module is typically used to process information contained in a RF signal. The module board will have processing capability necessary to make the RF signal usable by the mobile personal computer motherboard. The module is thus able to extract the digital signal from the analog carrier.  
           [0007]    A board-to-board RF connector is a two-piece connector. One piece of the board-to-board connector is permanently attached to the mobile personal computer motherboard, while the other piece of the connector is permanently attached to the RF module board. If desired, a radio frequency module may be connected onto the mobile personal computer motherboard by such a connector. However, the absence of the module will not interfere with the operation of the mobile personal computer motherboard. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.  
         [0009]    [0009]FIG. 1 is a schematic top view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector;  
         [0010]    [0010]FIG. 1A is a schematic side view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector;  
         [0011]    [0011]FIG. 1B is a schematic isometric view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector;  
         [0012]    [0012]FIG. 2 is an exploded view of one embodiment of both male and female coax connectors;  
         [0013]    [0013]FIG. 3 is a schematic illustration juxtaposing the assembled connectors one over the other;  
         [0014]    [0014]FIG. 4 is a schematic illustration showing one embodiment of connecting the RF coaxial connection through a co-planar waveguide transition on the surface of the board to the microstrip transmission line on the board; and  
         [0015]    [0015]FIG. 5 is a schematic illustration giving a better indication of the ground connection to the co-planar waveguide ground plane. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Reference will now be made to drawings wherein like structures will be provided with like reference designations. In order to show the structures of the claims most clearly, the drawings included herein are diagrammatic representations of board connection structures. Thus, the actual appearance of the fabricated structures, for example in a photograph, may appear different while still incorporating the essential structures of the claims. Moreover, the drawings show only the structures necessary to understand the claims. Additional structures known in the art have not been included to maintain the clarity of the drawings.  
         [0017]    [0017]FIG. 1 illustrates a schematic top view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector. One half of the connector, for example the “male” half, is mounted to a mobile personal computer motherboard, while the other half, in this example the “female” half, is attached to an add-in card module. The male half and the female half mate to form a coaxial connection connecting the mobile computer motherboard with the add-in module board. In one embodiment, the add-in module may be an RF module. RF coax connections  5  are capable of handling RF signals with frequencies, in one embodiment according to current standards, of up to 6 GHz. The digital signal connector  6  is capable of handling a data rate, in one embodiment, of 480 megabits per second (Mbits/s). RF coax connections  5  and digital connection  6  are packaged together within housing  7 .  
         [0018]    [0018]FIG. 1A is a schematic side view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector. RF module board  95 , in one embodiment, is connected to digital signal connector  16 , and three coaxial connectors  18 . Digital signal connector  16  and coaxial connectors  18  connect RF module board  95  to motherboard  100 . In one embodiment, a single RF coaxial connector  18  and digital signal connector  16  connect RF module board  95  to motherboard  100 .  
         [0019]    [0019]FIG. 1B is a schematic isometric view of one embodiment of a combination digital segment and radio frequency segment board-to-board connector. RF module board  95  is connected to motherboard  100  by mated coaxial connectors  18  and mated digital signal connector  16 . Additional supports, which may in one embodiment support RF module board  95  over motherboard  100  are not shown. RF module board  95  is shown in dashed lines, though, in one embodiment, it is superimposed over motherboard  100  to more clearly show the relationship between connectors  16  and  18  and boards  95  and  100 . It is important to note motherboard  100  is not limited to use in a mobile computer. Motherboard  100  may in one embodiment be part of a desk top, or larger, computer.  
         [0020]    [0020]FIG. 2 shows an exploded schematic view of male coax connector  15  and female coax connector  25 . Male coax connector  15  comprises RF signal pin  10 , outer or ground shield spring cage  30 , and housing  50 . RF signal pin  10  comprises signal plane contact  12 , which in one embodiment can be soldered to module board  95 . RF signal pin  10  also comprises signal pin insertion  14  for contacting signal receptacle spring  24 . In one embodiment, RF signal pin  10  may be made from a copper alloy that is plated with a noble metal to prevent oxidation. Noble metals include, but are not limited to gold, platinum and palladium.  
         [0021]    Male connector  15  of FIG. 2 also contains outer or ground shield spring cage  30 . Ground shield spring cage  30  comprises module board ground plane contacts  32  and finger springs  34 . In one embodiment, the module board ground plane contacts  32  may be through-hole soldered to a printed circuit board to make permanent contact to the ground plane in the printed circuit board. In another embodiment, module board ground plane contacts  32  may make connection with a surface ground, or a co-planar waveguide ground plane  80  (shown in FIG. 4) which then is connected to the ground plane in the printed circuit board through via holes  70  (shown in FIG. 4).  
         [0022]    Ground shield spring cage  30 , as shown in FIG. 2, typically is fabricated from a single sheet of metal. The sheet of metal may be stamped to cut away the extraneous parts of the sheet, and then what remains of the sheet is rolled, or formed into the configuration shown. Finger springs  34  are shaped such that their flexural compliance or rigidity enables them to maintain close contact with the interior cylindrical surface of outer ground shield barrel  40  of female coax connector  25 . Representative materials for ground shield spring cage  30  are phosphor bronze, beryllium copper, or brass.  
         [0023]    Housing  50  is designed to hold RF signal pin  10  and ground shield spring cage  30  in alignment relative to each other, while enabling easy assembly to the board. In one embodiment, RF signal pin  10  and outer shield spring cage  30  may be interference fitted into housing  50  to form male connector  15 . It is to be understood, that housing  50  shows only that portion of housing  7  from FIGS. 1, 1A and  1 B immediately surrounding the coax connector. The remainder of housing  7  is not shown to maintain the clarity of the drawing.  
         [0024]    The number of finger springs  34  in ground shield spring cage  30  is a trade off between manufacturability and the desire to have a complete grounding shield around RF signal pin  10 . The fewer finger springs  34  in the ground shield spring cage  30 , the easier it is to manufacture. In contrast, having more finger springs  34  in shield spring cage  30 , and the greater fraction of the cylindrical shell area the finger springs  34  comprise, increases the frequency at which the ground shield  30  for RF signal pin  10  may operate. In one embodiment, outer ground shield spring cage  30  will have between six and eight finger springs  34 .  
         [0025]    RF signal pin  10  fits tightly within signal receptacle  20 . Signal receptacle  20  has an upper end with signal receptacle springs  24  whose opening, in one embodiment may form a shape reminiscent of a tulip. The deflection of the signal receptacle springs by the RF signal pin  10  ensures a reliable electrical contact. Signal receptacle  20  also has lower end signal plane contacts  22 . In one embodiment, these signal plane contacts  22  may make connection with the signal line of the board that the female connector in the coaxial connection is attached to.  
         [0026]    Signal receptacle  20 , of female coax connector  25 , shown in FIG. 2, in one embodiment, may be stamped out of a single sheet of metal. The sheet metal after stamping is then rolled, or formed to form the cylindrical base and the tulip-shaped top portion  24 . The spring characteristic of signal receptacle springs  24  allows signal receptacle  20  to maintain a firm grasp on RF signal pin  10 . In one embodiment, Representative materials for signal receptacle  20  are phosphor bronze, beryllium copper, or brass.  
         [0027]    Outer or ground shield barrel  40 , of female coax connector  25 , shown in FIG. 2, surrounds signal receptacle  20  and forms a ground connection with male ground shield spring cage  30 . Ground shield barrel  40  has ground plane contacts  42  that may, in one embodiment, contact a coplanar waveguide ground plane ( 80  in FIG. 4) on the board to which it is attached by via through holes to the microstrip ground plane in the printed circuit board. In another embodiment, ground plane contacts  42  of ground shield barrel  40  punch through the printed circuit board and make direct solder contact to the ground plane therein. Signal receptacle  20  and ground shield barrel  40 , in one embodiment, may be press interference fit into housing  60 .  
         [0028]    Housing  60  maintains the position of signal receptacle  20  and ground shield barrel  40  relative to each other, and holds the female coaxial connector to the board. It is to be understood that housing  60  shows only that portion of housing  7  from FIGS. 1, 1A and  1 B immediately surrounding the coax connector. The remainder of housing  7  is not shown to maintain the clarity of the drawing. In one embodiment, outer ground shield barrel  40  is stamped from a single sheet of metal. This metal may be a copper alloy. Once the copper alloy stamp is rolled to form the cylindrical shell, ground shield barrel  40  may be plated with a noble metal to prevent corrosion.  
         [0029]    [0029]FIG. 3 illustrates one embodiment of how the male coaxial connector  15  and female coaxial connector  25  may be mated together to form coax connection  18 . In FIG. 3, male coax connector  15  is shown positioned over female coax connector  25 . Neither connector is shown attached to a board. Signal pin insertion  14  (not shown) of signal pin  10  connects with signal receptacle springs  24  of signal receptacle  20  of female coaxial connector  25 . Finger springs  34  of ground shield spring cage  30  of male coaxial connector  15  contact the inside surface of ground shield barrel  40  upon mating. The deflection of finger springs  34  allow outer ground shield spring cage  30  to form a secure physical contact with outer ground shield barrel  40 .  
         [0030]    [0030]FIG. 4 illustrates one embodiment of female connector  25  attached to a board. It is to be understood that the male connector may be attached to its board in a similar manner. In this embodiment, the board to which female coaxial connector  25  is attached is motherboard  100 . Motherboard  100  contains a microstrip signal line  90  that connects to signal plane contacts  22  of signal receptacle  20 . Surface ground, or co-planar waveguide ground plane  80  on the surface of motherboard  100  connects to ground plane contacts  42  of ground shield barrel  40 . Typically, the surface of motherboard  100  is dedicated to signal lines, such as for example signal line  90 . However, in this co-planar waveguide embodiment, a portion of the surface of motherboard  100  is dedicated to transitioning the microstrip ground plane embedded in the printed circuit board to surface ground  80  by use of the co-planar structure. Surface ground  80  is connected to the lower ground plane within printed circuit board  100  through multiple vias  70 .  
         [0031]    [0031]FIG. 5 shows the co-planar waveguide of FIG. 4 with housing  60  removed for better illustration of the ground plane contact using co-planar waveguide ground plane  80 . Outer ground shield barrel ground contacts  42  may form an electrical connection to co-planar waveguide ground plane  80 . The ground signal may travel through co-planar waveguide ground plane  80  to the ground plane of printed circuit board  100  through vias  70 .  
         [0032]    The addition of the co-planar waveguide allows a more smooth transition from the microstrip transmission line to the coaxial connector of the claims. This transition allows a more continuous ground path for supporting the GHz transmission line.  
         [0033]    In the preceding detailed description, the invention is described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Technology Category: h