Patent Publication Number: US-8123536-B1

Title: Connector with isolated grounds

Description:
BACKGROUND OF THE INVENTION 
     High frequencies such as above 100 kHz are commonly carried through cables and contacts wherein the center conductor(s) carries the signal and the outer conductor is at a first ground potential to protect the center conductors from noise. Even higher frequencies such as above 100 MHz are sometimes carried through cables and contacts wherein even greater protection against noise is provided by plural ground contacts wherein a second grounded conductor lies within the first grounded conductor. Signals protected by a single ground and signals protected by two grounds, can be transmitted through contacts of a single connector that is preferably arranged for compactness. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the invention, a compact connector is provided that includes a first section that carries single ground-protected signals wherein each signal-carrying contact is protected by one ground, and one or more second sections that carry a double ground-protected signal wherein each signal-carrying contact is protected by two grounds including said first ground and a second ground. 
     The connector includes a conductive frame, insulative (dielectric) holders lying in the frame and having passages, and contacts mounted in the passages. The holders include a main holder that lies in the electrically grounded frame, and that holds first signal contacts at a predetermined spacing (0.080 inch) of their edges from each other and from the frame to achieve the first characteristic impedance (50 ohms). The holders include a pair of second holders, or end holders that lie in the frame, with each end holder holding three second contacts that include two second signal contacts and a second ground contact. The second ground contact is spaced from the second signal contacts and from the conductive frame by a predetermined spacing (0.060 inch) of their edges to achieve a second characteristic impedance (100 ohms). 
     The first signal contacts that lie in the main holder, are arranged in three rows, with the center row offset from the top and bottom rows, and with one fewer contact in the center row. This allows the main holder to have holder recesses at its ends. The grounded frame has corresponding frame recesses at its opposite ends. Each of the second holders is of elongated shape, such as an isosceles triangle with three sides and three rounded corners. One of the corners juts into a frame recess. 
     The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric exploded view of a connector of the present invention. 
         FIG. 2  is a sectional view of the connector of  FIG. 1 , shown mounted on a circuit board. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a connector  10  of the invention, which includes a conductive frame  12  that has a first, or main cavity  14  that extends in front F and rear R longitudinal directions M through the frame. The frame has a pair of second cavities  20 ,  22  that also extend longitudinally through the frame. A first or main dielectric (insulative) holder  24  can be inserted to lie closely (less than one millimeter clearance) in the first cavity. A pair of second dielectric holders  26 ,  28  can each be inserted to lie closely in the second cavities. The main holder has a plurality of passages ( 30 ) that each holds a first contact  32 . The second, or end holders  26 ,  28  each has three passages  36  that hold three second contacts  34 , including contacts  52 ,  54 ,  56 . Each of the contacts  32 ,  34  has a front end  46  that may be of a male (pin) type or female (socket) type, with a pin type being shown to connect to sockets  47  of a mating connector  48 . The rear ends  50 ,  51  of the contacts can be connected to conductors of a cable, to other contacts, or to traces on a circuit board. 
     The first contacts  32  are designed to be used as signal contacts to carry high frequency signals (e.g. frequencies of at least 100 KHz). The use of a conductive frame  12  around the first contacts, and uniform spacing A ( FIG. 2 ) between edges of adjacent pairs of contacts, and between the frame and each adjacent contact, results in a predetermined characteristic impedance. If two contacts have the same characteristic impedance, there are low losses of signals transmitted between them, while a significant difference (above 50%) in impedance results in losses. Applicant uses a spacing A of 0.080 inch (2 millimeters) between the edges of pairs of first contacts  32  and between the frame and adjacent first contacts, which produced a characteristic impedance of 50 ohms. Applicant uses a spacing B of 0.060 inch (1.5 millimeters) between adjacent edges of pairs of second contacts  34  to produce a characteristic impedance of 100 ohms for each second contact. 
     The second contacts  34  ( FIG. 1 ) which lie in each of the second holders  26 : 28  include two signal contacts  52 ,  54  and one secondary ground contact  56 . The secondary ground contact  56  is connected to a second electrical ground potential G 2  which is isolated from direct connection with the ground potential G 1  of the frame. This has the advantage that almost all of the low amplitude but appreciable amount of noise passing through the frame, is not present in the secondary ground. 
     There is often limited space to mount the multiple contacts, so it is advantageous to make the connector as compact as possible. The first contacts  32  are arranged in three rows  62 ,  64 ,  66  that each extends laterally L, with the middle row  64  offset from the top and bottom rows to obtain uniform spacing A ( FIG. 2 ) between adjacent edges of the first contacts. There is one fewer middle contact than the number in the top or bottom row. As a result, the opposite ends of the main holder have indentations  70 . Applicant constructs the frame walls  80  that extend around each indented end  82  wall of the main holder so the frame also has indentations  84 . 
     Each of the two end holders  26 ,  28  ( FIG. 2 ) is vertically elongated with a height about 50% greater than its width (25% to 75% greater). Each of the illustrated holder has an outside in the form of an isosceles triangle with three straight sides  91 - 93  and three rounded corners  95 - 97 . One of the sides  91  is longer than the other two sides, and the distance between the two signal contacts ( 52 ,  54 ) is about 50% greater than the distance between the ground contact ( 56 ) and each signal contact. The two secondary holders are mirror images of each other. One of the corners  95  projects into an indentation at  84  in the end of the frame walls, at each lateral end of the connector. Another possible shape of each end holder is an ellipse. 
     The frame  12  is preferably formed by machining a block of metal such as aluminum. It is possible to mold a plastic frame and attach a sheet metal covering to it, although such frame is not as durable. 
     Thus, the invention provides a compact electrical connector which connects first contacts that have a first characteristic impedance to other conductors of the same impedance, and that connects second contacts that have a second characteristic impedance to other conductors of the same second impedance. Noise is blocked from the contacts by the use of a conductive frame that is connected to a first ground potential that surrounds the contacts. A further reduction of noise in the second contacts is obtained by including a grounded second contact adjacent to the second contacts that carry signals, with the grounded second contacts connected to a second ground potential that is electrically isolated from the first ground potential. A main holder has three vertically-spaced rows of first contacts, including an offset middle row, and has a recess in each end. Two second holders are each vertically elongated, such as in a triangular shape with rounded corner, with one rounded corner of each second holder projecting into a recess in each end of the frame portion of the first holder. 
     Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.