Abstract:
A connector comprises a plurality of contact arrays parallel to one another. Each of the contact arrays includes two signal contacts (S) adjacent to each other and a ground contact (G) aligned with the signal contacts. In each contact array, the ground contact is located at a position corresponding to an intermediate position between two signal contacts in a next contact array.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to a connector comprising a plurality of contact arrays and, in particular, to a connector suitable for high-speed differential signal transmission. 
   At first, high-speed differential signal transmission will be described. The high-speed differential signal transmission has two types of transmission modes, i.e., an unbalanced (single-end) type and a balanced (differential) type. The single-end type is a mode in which a high level and a low level of a digital signal are distinguished by the potential difference between a ground line and a signal line, and is generally used so far. On the other hand, the differential type is a mode in which two signal lines (+, −) are used and the high level and the low level are distinguished by the potential difference between the two signal lines. In the differential type, two signals on the two signal lines are equal in voltage level to each other and different in phase by 180° from each other. As compared with the single-end type, the differential type assures reliable transmission because noise produced in the two signal lines is canceled at the receiver input. 
   Besides, there is another transmission mode according to TMDS (Transition Minimized Differential Signaling). The TMDS is a standard for exchange of image data between a PC main body and a display monitor, and is a mode in which data transmission is performed by the use of two signal lines (+, −) and a single ground line. 
   In an existing connector comprising signal contacts and ground contacts, use is made of a structure in which the signal contacts and the ground contacts are faced to each other in a grid-like pattern or a structure in which the ground contacts are partially skipped. In the former structure, the number of contacts is increased so that miniaturization of the connector is difficult. In the latter structure, the high-frequency characteristics of the connector are considerably degraded. 
   At present, transmission of high-speed differential signals is required in a growing number of software applications. Under the circumstances, there is a demand for a connector having a compact size, a low price, and excellent high-frequency characteristics. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of this invention to provide a connector which is compact in size, low in price, and excellent in high-frequency characteristics. 
   Other objects of the present invention will become clear as the description proceeds. 
   According to one aspect of this invention, there is provided a connector comprising a plurality of contact arrays parallel to one another, each of the contact arrays including two signal contacts adjacent to each other and a ground contact aligned with the signal contacts, the ground contact in each contact array being disposed at a position corresponding to an intermediate position between two signal contacts adjacent to each other in a next contact array. 
   According to another aspect of this invention, there is provided a connector comprising first and second contact arrays parallel to each other and a third contact array between the first and the second contact arrays, each of the first and the second contact arrays including a plurality of signal contacts, the third contact array including a plurality of ground contacts, each of the ground contacts being disposed at a position corresponding to an intermediate position between every adjacent ones of the signal contacts in each of the first and the second contact arrays. 
   According to still another aspect of this invention, there is provided a connector for high-speed differential signal transmission, the connector comprising a plurality of + signal contacts, a plurality of − signal contacts, and a plurality of ground contacts, the contacts being arranged in a manner such that a set of each single one of the + signal contacts, each single one of the − signal contacts, and each single one of the ground contacts are located at three apexes of an isosceles triangle, respectively. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1A  is a schematic plan view of a receptacle connector according to a first embodiment of this invention, 
       FIG. 1B  is a schematic front view of the receptacle connector of  FIG. 1A ; 
       FIG. 2A  is a plan view of the receptacle connector illustrated in  FIGS. 1A and 1B ; 
       FIG. 2B  is a partially-sectional side view of the receptacle connector of  FIG. 2A ; 
       FIG. 2C  is a front view of the receptacle connector of  FIG. 2A ; 
       FIG. 2D  is a side view of the receptacle connector of  2 A; 
       FIG. 3A  is a plan view of a plug connector adapted to be connected to the receptacle connector illustrated in  FIGS. 2A  to  2 D; 
       FIG. 3B  is a front view of the plug connector of  FIG. 3A ; 
       FIG. 3C  is a side view of the plug connector of  FIG. 3A ; 
       FIG. 4  is a schematic plan view of a receptacle connector according to a second embodiment of this invention; 
       FIG. 5A  is a plan view of the receptacle connector illustrated in  FIG. 4 ; 
       FIG. 5B  is a partially-sectional side view of the receptacle connector of  FIG. 5A ; 
       FIG. 5C  is a front view of the receptacle connector of  FIG. 5A ; 
       FIG. 5D  is a side view of the receptacle connector of  FIG. 5A ; 
       FIG. 6A  is a plan view of a plug connector adapted to be connected to the receptacle connector illustrated in  FIGS. 5A  to  5 D; 
       FIG. 6B  is a front view of the plug connector of  FIG. 6A ; 
       FIG. 6C  is a side view of the plug connector of  FIG. 6A ; 
       FIG. 7A  is a schematic plan view of a receptacle connector according to a third embodiment of this invention; 
       FIG. 7B  is a schematic front view of the receptacle connector of  FIG. 7A ; 
       FIG. 8A  is a plan view of the receptacle connector illustrated in  FIGS. 7A and 7B ; 
       FIG. 8B  is a partially-sectional side view of the receptacle connector of  FIG. 8A ; 
       FIG. 8C  is a front view of the receptacle connector of  FIG. 8A ; 
       FIG. 8D  is a side view of the receptacle connector of  FIG. 8A ; 
       FIG. 9  is a plan view for describing a connection pattern of transmission cables; 
       FIG. 10A  is a plan view of a connection structure between the transmission cables and each of the receptacle connectors; 
       FIG. 10B  is a bottom view of the connection structure of  FIG. 10A ; 
       FIG. 10C  is a left side view of the connection structure of  FIG. 10A ; 
       FIG. 11A  is a plan view of a modification of the connection structure illustrated in  FIGS. 10A  to  10 C; 
       FIG. 11B  is a sectional view taken along a line A—A in  FIG. 11A ; 
       FIGS. 12A  to  12 J are various views each showing a ground plate used in each of the receptacle connectors; 
       FIGS. 13A  to  13 J are various views each showing a shield plate used in each of the receptacle connectors; 
       FIGS. 14A  to  14 J are various views each showing a combination of the ground plate and the shield plate engaged with each other; and 
       FIG. 15  is a view for describing pitch conversion between contacts and through holes which are formed in a circuit board for receiving the contacts, respectively. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   At first referring to  FIGS. 1A and 1B  through  FIGS. 3A  to  3 C, description will be made of a connector according to a first embodiment of this invention. 
   The connector illustrated in the figures is a receptacle connector  1 . As illustrated in  FIGS. 1B and 2A  to  2 D, the receptacle connector  1  comprises a plurality of signal contacts S, a plurality of ground contacts G, a plurality of ordinary (low-speed) contacts D, and an insulator  2  holding the signal contacts S, the ground contacts G, and the ordinary contacts D, and a receptacle shell  3  surrounding all of the above-mentioned components. Each pair of the signal contacts S adjacent to each other includes a + signal contact and a − signal contact. 
   As illustrated in  FIG. 1B , the contacts of the above-mentioned three types (S, G, and D) are disposed in a specific arrangement. In an upper array, the contacts are arranged in the order of S, S, G, S, S, G, D, D, D from the right side. In a lower array, the contacts are arranged in the order of G, S, S, G, S, S, D, D from the right side. The signal contacts S, S adjacent to each other in the upper array and the ground contact G in the lower array are located at three apexes of an isosceles triangle. Likewise, the ground contact G in the upper array and the signal contacts S, S adjacent to each other in the lower array are located at three apexes of an isosceles triangle. 
   The receptacle shell  3  has an upper surface provided with a pair of springs  3 A. The springs  3 A are adapted to be engaged with a plug connector  6  illustrated in  FIGS. 3A  to  3 C. 
   Referring to  FIGS. 3A  to  3 C, the plug connector  6  comprises a plurality of signal contacts S, a plurality of ground contacts G, a plurality of ordinary contacts D, an insulator  7  holding the signal contacts S, the ground contacts G, and the ordinary contacts D, and a plug shell  8  surrounding all of the above-mentioned components. 
   The plug shell  8  has an upper surface provided with a pair of holes  8 A. The holes  8 A are adapted to be engaged with the springs  3 A of the receptacle connector  1 , respectively. 
   Next referring to  FIGS. 4 through 6A  to  6 C, description will be made of a connector according to a second embodiment of this invention. 
   The connector illustrated in the figures is a receptacle connector  11 . As illustrated in  FIGS. 4 and 5A  to  5 D, the receptacle connector  11  comprises a plurality of signal contacts S, a plurality of ground contacts G, a plurality of ordinary contacts D, an insulator  12  holding the signal contacts S, the ground contacts G, and the ordinary contacts D, and a receptacle shell  13  surrounding all of the above-mentioned components. 
   Referring to  FIG. 4 , the contacts of the above-mentioned three types (S, G, and D) are disposed in a specific arrangement. In an upper array, the contacts are arranged in the order of S, S, S, S, D, D from the right side. In a middle array, the contacts are arranged in the order of G, G, G, G, D, D from the right side. In a lower array, the contacts are arranged in the order of S, S, S, S, D from the right side. The signal contacts S, S adjacent to each other in the upper array and the ground contact G in the middle array are located at three apexes of an isosceles triangle. Likewise, the ground contact G in the middle array and the signal contacts S, S adjacent to each other in the lower array are located at three apexes of an isosceles triangle. 
   As illustrated in  FIGS. 4 ,  5 A, and  5 B, the receptacle shell  13  has an upper surface provided with a pair of holes  13 A. The holes  13 A are adapted to be engaged with a plug connector  16  illustrated in  FIGS. 6A  to  6 C. 
   Referring to  FIGS. 6A  to  6 C, the plug connector  16  comprises a plurality of signal contacts S, a plurality of ground contacts G, a plurality or ordinary contacts D, an insulator  17  holding the signal contacts S, the ground contacts G, and the ordinary contacts D, and a plug shell  18  surrounding all of the above-mentioned components. 
   The plug shell  18  has an upper surface provided with a pair of springs  18 A. The springs  18 A are adapted to be engaged with the holes  13 A of the receptacle connector  11 , respectively. 
   Next referring to  FIGS. 7A ,  7 B, and  8 A to  8 D, description will be made of a connector according to a third embodiment of this invention. 
   The connector illustrated in the figures is a receptacle connector  21  of a SMT (Surface Mount) type. As illustrated in  FIGS. 7B and 8A  to  8 D, the receptacle connector  21  comprises a plurality of signal contacts S, a plurality of ground contacts G, a plurality of ordinary contacts D, an insulator  22  holding the signal contacts S, the ground contacts G, and the ordinary contact D, and a receptacle shell  23  surrounding all of the above-mentioned components. 
   As illustrated in  FIG. 7B , the contacts of the above-mentioned three types (S, G, and D) are disposed in a specific arrangement. In an upper array, the contacts are arranged in the order of S, S, G, S, S, G, D, D, D from the right side. In a lower array, the contacts are arranged in the order of G, S, S, G, S, S, D, D from the right side. The signal contacts S, S adjacent to each other in the upper array and the ground contact G in the lower array are located at three apexes of an isosceles triangle. Likewise, the ground contact G in the upper array and the signal contacts S, S adjacent to each other in the lower array are located at three apexes of an isosceles triangle. 
   As illustrated in  FIG. 7A , the contacts are arranged in a single line in the order of S, G, S, S, G, S, S, G, S, S, G, S, D, D, D, D, D form the right side and exposed from the receptacle shell  23 . 
   As illustrated in  FIGS. 7A ,  8 A, and  8 B, the receptacle shell  23  has an upper surface provided with a pair of springs  23 A. The springs  23 A are adapted to be engaged with a plug connector (not shown). 
   Referring to  FIGS. 9 through 11A  and  11 B, description will be made of a connection structure of the connector in each embodiment and transmission cables. 
   As illustrated in  FIG. 9 , each transmission cable  31  has a center conductor  31 A connected to each signal contact S. Each of the signal contacts S and the ground contacts G has a terminal portion to be connected to a printed board. The terminal portions are arranged in a single line in a manner such that two signal contacts S are arranged adjacent to each other and one ground contact G is arranged next. The signal contacts S and the ground contacts G are arranged at a predetermined pitch A. In this structure, a space is left in an area faced to each ground contact G. By utilizing the space, it is possible to arrange the transmission cables  31 , each of which has a diameter greater than A and smaller than 1.5A, with the center conductors  31 A of the transmission cable  31  connected to the signal contacts S. 
   In each of the above-mentioned connectors, the plug connector with the transmission cables connected thereto is fitted to the receptacle connector mounted to the printed board. Each of the signal contacts S, the ground contacts G, and the ordinary contact D may be of a surface-mount type or a through-hole type. 
   Referring to  FIGS. 10A  to  10 C, the transmission cables  31  have shield portions  31 B divided into upper and lower arrays. Upper-array and lower-array ground plates  32  and  33  are superposed to each other and inserted between the upper and the lower arrays of the shield portions  31 B. The upper-array ground plate  32  has connecting portions  32 A connected to the shield portions  31 B of the upper array. The lower-array ground plate  33  has connecting portions  33 A connected to the shield portions  31 B of the lower array. 
   The upper-array and the lower-array ground plates  32  and  33  are provided with lead portions  32 B and  33 B to be contacted with or soldered to the ground contacts G, respectively. The upper-array and the lower-array ground plates  32  and  33  are faced to each other with the lead portions  32 B and  33 B alternately arranged. In this manner, the lead portions  32 B and  33 B can be connected to the ground contacts G arranged in a staggered fashion and located at the apexes of the isosceles triangles. 
   As illustrated in  FIG. 10B , the lead portions  33 B of the lower-array ground plate  33  are connected to the ground contacts G of the upper array while the lead portions  32 B of the upper-array ground plate  32  are connected to the ground contacts G of the lower array. Alternatively, as illustrated in  FIG. 10C , the lead portions  32 B of the upper-array ground plate  32  are connected to the ground contacts G of the upper array while the lead portions  33 B of the lower-array ground plate  33  are connected to the ground contacts G of the lower array. 
   As illustrated in  FIGS. 11A and 11B , the shield portion  31 B of each of the transmission cables  31  on both upper and lower sides may be surrounded by a ground plate  34  on the left, right, and lower sides and by a shield plate  35  on an upper side. In this event, the shield portion  31 B of the transmission cable  31  is connected to the ground plate  34  and the shield plate  35 . 
   Referring to  FIGS. 12A  to  12 J, the ground plate  34  of the connector is illustrated as seen in different directions. The ground plate  34  has one side provided with a pair of lead portions  34 A which can be connected to an electric circuit formed on the circuit board. 
   Referring to  FIGS. 13A  to  13 J, the shield plate  35  of the connector is illustrated as seen in different directions. The shield plate  35  is engaged with the ground plate  34  to form a combination of the ground plate and the shield plate, as illustrated in  FIGS. 14A  to  14 J. 
   Referring to  FIG. 15 , the description will be made as regard a pitch of contacts  36  provided on the receptacle connector  1 . 
   The contacts  36  are arranged in two rows on the receptacle connector  1 . In this condition, the pitch is relatively small or narrow on the receptacle connector  1 . The contacts  36  may be connected to an electric circuit of the circuit board by inserting the contacts  36  in through holes  37  formed in the circuit board. In this event, the through holes  37  can be arranged in three or more rows. In case where the through holes  37  are arranged in three or more rows, it becomes possible to make the pitch of the through holes  37  be relatively large or widen the pitch on the circuit board. This results in pitch conversion between the contacts  36  and the through holes  37 .