Patent Publication Number: US-6712628-B2

Title: Connector/switch unit for a flat antenna

Description:
The present invention relates to devices which combine both a connector and a switch for disconnecting an “antenna circuit”, in particular of the “patch antenna” type hereinafter referred to as a flat antenna, and circuits for supplying this, whilst connecting these same circuits to a plug allowing external connection of these circuits. This plug is for example itself connected to a cable for supplying an antenna which is more effective than the initial flat antenna. Such devices are for example used for connecting a portable telephone to a fixed base. 
     Such a currently known device is depicted in its disconnected state in FIG.  1  and in its connected state in FIG.  2 . 
     The flat antenna  101  is fixed to a support  102 , as is the earth plane  103  which supplements the antenna in order to obtain the required radiation diagram. The antenna is supplied by a spring connector  104  and the earth plane by a spring connector  105 , from circuits for transmitting and/or receiving radio frequency signals which are themselves fixed to a printed circuit board  106 . 
     The radio frequency signal arrives at this printed circuit through a circuit  107  and the earth through a circuit  108 . The radio frequency signal is then routed from this circuit  107  as far as a spring connector  104  by means of a switch  109  formed by a spring blade  110  which can, according to its position, provide continuity between the circuit  107  and a circuit  111  on which the spring connector  104  bears. 
     The continuity between the blade  110  and the circuit  111  is provided by a conductive piece  112  fixed in the insulating body  113  of the switch. A metallic rod  114  perpendicular to the plane of the circuit  106  is fixed to the flexible blade  110 . 
     When a pressure is exerted on the end of this rod, it makes the blade  110  flex and cuts off communication between this blade and the piece  112 . The body  113  is itself surrounded by a conductive pot  115  which is connected to the earth circuit  118  in order to be able to obtain the earth recovery as described below. 
     In the disconnected state illustrated in FIG. 1, the radio frequency signal arrives through the conductor  107 , passes through the blade  110 , the piece  112 , the conductor  111  and the spring connector  104 , and is finally applied to the flat antenna  101 . 
     In order to be able to use an external antenna, or possibly a measuring circuit, a plug  116  is used, comprising an external casing  117  and a central conductor  119  forming a core and separated from the conductive external casing by an insulating layer  118 . 
     This plug is conical in shape, so as to be able to enter a hole  120  provided in the support  102  in line with the switch  109  and situated also at the separation level between the flat antenna  101  and the earth plate  103 . The end of the central conductor  119  of the plug  116  projects at the tip of this conical part at a hole provided in the external casing  117 . 
     When the plug is lowered in order to insert it in the hole  120 , the end of the core  119  presses on the rod  114 , which makes the blade  116  flex and interrupts the transmission of the radio frequency signal to the piece  112  and therefore to the flat antenna  101 . The radio frequency signal is on the other hand then applied to the core  119  of the plug, so as to be able to be transmitted to the circuits connected to this plug, which are not shown in the figure. 
     Simultaneously, the conical part of the casing  117  of the plug is placed in a hollow provided in the top part of the conductive pot  115  of the switch  119  and adapted to the conical shape of the end of the plug. In this way contact is established between the casing  117  of the plug and the pot  115  of the switch, which establishes the earth connection between the circuit  108  and the external casing of the plug. 
     Mechanical means, not shown but known to persons skilled in the art, provide the mechanical fixing of these pieces together. 
     This system functions well but has the drawback of being of large size and consequently reducing the surface area of the flat antenna, which therefore reduces the performance of the latter. 
     In order to be able to reduce the dimensions of this system and to be able to increase the surface area and therefore the efficacy of the flat antenna, the invention proposes a connector/switch unit for alternately connecting an earth circuit respectively to an earth plane or to the external casing of a plug, and a radio frequency circuit respectively to an antenna circuit or to the core of said plug, this earth plane and antenna circuit being carried by one and the same insulating support plane comprising a hole for allowing said plug to pass, principally characterized in that the earth circuit is connected to said earth plane by a first spring connector distinct from the switching means of the unit, in that the support plane comprises a hollow cylindrical protrusion comprising an internal cavity opening out in said hole, in that this hole comprises an oval hollow periphery adapted to the conical shape of said plug, in that the antenna circuit and the earth plane are extended towards the inside of the hole whilst matching said oval hollow periphery, and in that the unit also comprises a second spring connector placed in the said internal cavity and comprising a central rod provided with a collar and pushed in one direction by a spring in order to establish contact with the antenna circuit when said plug is removed, and to establish contact with said core by cutting off contact with the antenna circuit when said plug is pressed into the hole, pushing said rod in the other direction. 
     According to another characteristic, the unit comprises a printed circuit board coplanar with said flat support supporting said earth circuit and said radio frequency circuit; said cylindrical protrusion bearing on the printed circuit board and the second spring connector also bearing on the printed circuit plate at the radio frequency circuit through its end opposite to the one establishing contact with the plug. 
     According to another characteristic, the extension of the antenna circuit inside the hole is sufficiently long to serve as a stop for the said central rod by means of the collar carried by this central rod. 
    
    
     Other particularities and advantages of the invention will emerge clearly from the following description, given with regard to the accompanying figures, which depict: 
     FIGS. 1 and 2, views in section of a known device, in two states, respectively not connected and connected; and 
     FIGS. 3 and 4, views in section of a device according to the invention, in the same non-connected and connected states. 
    
    
     The device according to the invention, depicted schematically and in section in FIGS. 3 and 4, also comprises a flat antenna  201  and an earth plane  203  both fixed to a support  202 , and a printed circuit board  106  which comprises a radio frequency signal circuit  207  and an earth circuit  208 . 
     The plug  116  intended to be connected to this device is identical to the one in FIGS. 1 and 2. 
     The earth circuit  208  is connected to the earth plane  203  by means of a spring connector  105 , in the same way as in FIG.  1 . However, this circuit  208  is connected only to the spring connector  105 . 
     The support  202  comprises a protrusion  213  in the form of a cylinder perpendicular to the plane of this support, the printed circuit board  106 , the antenna and the earth plane. This protrusion is hollow and its axis is merged with that of the plug  116  in the position in which the latter is connected to the device. 
     The internal cavity of the cylinder  213  contains a second spring contactor  204  whose base is in direct contact with the circuit  207  receiving the radio frequency signal. 
     The top end of the internal cavity of the cylinder  213  opens out on the surface of the support  202 , forming a conical cavity  220 . 
     The conductive sheet forming the flat antenna  201  is dished to the shape of this conical cavity  220  in order to open out inside the internal cylindrical cavity of the cylinder  213 . 
     In the same way, the metallic sheet composing the earth plane  203  is dished in the form of the conical cavity  220  in order to open out in this internal cylindrical cavity of the cylinder  213 . 
     The lengths of the parts  227  of the flat antenna on the one hand and  228  of the earth plane on the other hand, which open out in this interior, are such that the end of the flat antenna is situated closer to the printed circuit  106  than is the end of the earth plane. 
     The spring contact  204  comprises, in a known manner, a movable rod  224  which is pushed upwards by a spring  225 . This rod comprises at its top end, a little lower than the latter, a collar  226  which is wider than the space existing between the ends  227  and  228  respectively of the flat antenna and of the earth plane which open out in the internal cavity of the protrusion  213 . 
     In this way, under the thrust of the spring  225 , the rod  224  makes contact with the flat antenna  201  without making contact with the earth plane  203 , because of the different dimensions, explained above, of the ends of these two members. 
     In the non-connected case depicted in FIG. 3, the flat antenna  201  is therefore supplied by the spring connector  204  from the circuit  207 , and the earth plane  203  is connected to the earth circuit  208  by means of the spring connector  105 . 
     By making the plug  116  descend in the oval hole  220 , as depicted in FIG. 4, the end of the core  119  of the plug  116  will bear on the end of the rod  224 , which pushes it downwards, compressing the spring  225 . This action causes on the one hand the disconnection of the flat antenna  201  from the rod  224  and therefore from the radio frequency supply circuit  207 , and the connection of this rod  224  to the core  119  of the plug  116 . This plug is therefore supplied with the radio frequency signal applied to the circuit  207 , by means of the spring connector  204 . 
     When the plug is fully inserted in the oval hole  220 , it is locked in position, connected by mechanical means such as those cited above, and earth contact is then established between the earth plane  203  and the external casing  117  of the plug by means of the part  228  of the earth plane. 
     In addition, the flat antenna  201  is itself connected to the external casing  117  by means of its part  227 . It can be seen that, in this connected position, the flat antenna forms with the earth plane a single earth plane, enlarged and substantially continuous, which improves the performance of the whole all the more. 
     In addition, in accordance with the principal aim of the invention, the oval hole  220  is much smaller than the oval hole  120  of the prior art, which increases the dimensions of the flat antenna and therefore its efficacy. 
     Finally, all the components participating in the connection and disconnection are much smaller in number, which increases the simplicity and therefore the reliability of the whole whilst reducing the production cost.