Abstract:
An RF emissions shield for grounding a chassis to an associated connector mounted on a backplane includes a shield body, mounting means for securing the shield body to the backplane, and grounding means for electrically connecting the shield body to the connector. At least one spring member is integral with the shield body and is adapted to engage the chassis such that the spring member is biased against the chassis. Preferably, the at least one spring member includes a plurality of curved, resilient fingers extending from an edge of the shield body. The mounting means may include an aperture defined in the shield body, the aperture sized and configured to receive the connector such that at least an engagement portion of the shield body along the aperture engages the connector.

Description:
FIELD OF THE INVENTION 
     The present invention relates to electrical connectors, and, more particularly, to devices and methods for shielding and grounding. 
     BACKGROUND OF THE INVENTION 
     Radio frequency (RF) components, assembled boards and modules radiate both desirable and undesirable emissions. The desirable emissions are those that the components, assembled boards and modules are designed to emit. The undesirable emissions should be suppressed to avoid interference with other equipment. In cellular base station equipment, this is especially true because of the close proximity of other components, assembled boards and modules in the base station. Such components may also be subjected to undesirable RF emissions from external sources. 
     Attempts have been made to provide shielding and grounding to suppress unwanted emissions between RF modules that are mounted closely together and plugged into a common backplane. One attempt to solve this problem utilizes a conductive adhesive gasket and a conductive adhesive tape. The conductive adhesive gasket is applied to the RF module chassis and the conductive adhesive tape is applied to the backplane. When the RF module is mounted, the gasket on the RF module chassis touches the tape on the backplane. 
     Unfortunately, the adhesive backed gasket is fragile and tends to become damaged with repeated removal and handling of the RF module. The adhesive backed gasket may also peel off rather easily if the backplane surface has not been cleaned and prepared properly prior to application of the gasket. The damaged gasket may fail to seal properly, or worse, may physically interfere with the mounting of the module. Another shortcoming of this technique is that the gasket and the tape are typically aligned and applied by hand. The conductive tape should be properly located to allow proper electrical contact with other portions of the backplane and the mounting frame to which it is fastened. The mounting surfaces should be prepared properly by cleaning, which is also typically a hand operation. The results are often inconsistent, leading to poor quality and poor shield performance. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a shield and grounding method for reducing unwanted emissions between modules that are mounted closely together and plugged into a common backplane. According to one aspect of the present invention, an RF emissions shield for grounding a chassis to an associated connector mounted on a backplane includes a shield body, mounting means for securing the shield body to the backplane, and grounding means for electrically connecting the shield body to the connector. At least one spring member is integral with the shield body and is adapted to engage the chassis such that the spring member is biased against the chassis. Preferably, the at least one spring member includes a plurality of curved, resilient fingers extending from an edge of the shield body. 
     According to another aspect of the present invention, an RF emissions shield for grounding a chassis to an associated connector mounted on a backplane includes a shield body having an edge. An aperture is defined in the shield body. The aperture is sized and configured to receive the connector such that at least an engagement portion of the shield body along the aperture engages the connector to secure the shield body to the backplane and to electrically connect the shield body to the connector. A plurality of curved, resilient spring fingers extend from the edge. Preferably, the shield body is substantially planar. More preferably, the spring fingers extend above the plane of the shield body. The shield may include a tab integral with the shield body and extending into the aperture, the tab adapted to be deflected by and engage the connector when the connector is inserted into the aperture. 
     According to a further aspect of the present invention, an RF emissions shielded connector assembly for use with a chassis includes a backplane assembly and a shield for grounding the chassis. The backplane assembly includes a backplane, and a connector extending from the backplane. The shield is secured to the backplane assembly and includes an electrically grounded shield body and at least one spring member integral with the shield body. The at least one spring member is adapted to engage the chassis such that the spring member is biased against the chassis. Preferably, the at least one spring member includes a plurality of curved, resilient fingers extending from an edge of the shield body. Preferably, the connector is electrically grounded, the shield includes an aperture defined in the shield body, and the connector extends through the aperture and engages at least an engagement portion of the shield disposed along the aperture. 
     According to a further aspect of the present invention, an RF emissions shielded connector system includes a connector module and a connector assembly. The connector module includes an electrically conductive chassis and a first connector mounted on the chassis. The connector assembly includes a backplane assembly and a shield for grounding the chassis. The backplane assembly includes a backplane and a second connector extending from the backplane and adapted to engage the first connector. The shield is secured to the backplane assembly and includes an electrically grounded shield body and at least one spring member integral with the shield body. The at least one spring member is adapted to engage the chassis when the first and second connectors are engaged such that the spring member is biased against the chassis. Preferably, the at least one spring member includes a plurality of curved, resilient fingers extending from an edge of the shield body. Preferably, the second connector is electrically grounded, the shield includes an aperture defined in the shield body, and the second connector extends through the aperture and engages at least an engagement portion of the shield disposed along the aperture. 
     According to another aspect of the present invention, a method for connecting a connector module having a chassis to a backplane assembly including a backplane and a connector extending from the backplane includes mounting a grounding shield on the backplane assembly such that the shield is electrically grounded to the backplane assembly. The shield includes a shield body and at least one spring member integral with the shield body. Thereafter, the connector module is connected to the backplane assembly such that the at least one spring member engages and is biased against the chassis. 
     Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the Figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a shield according to the present invention; 
     FIG. 2 is a perspective view of a connector assembly according to the present invention and incorporating the shield of FIG. 1; 
     FIG. 3 is an exploded, perspective view of the connector assembly of FIG. 2; 
     FIG. 4 is a perspective view of a backplane, connectors and the shield of the connector assembly of FIG. 2; 
     FIG. 5 is an enlarged, perspective view of detail A of FIG. 4; 
     FIG. 6 is an exploded, perspective view of a connector system including the connector assembly of FIG. 2 and a connector module; 
     FIG. 7 is a perspective view of the connector system of FIG. 6 wherein the connector assembly and the connector module are connected; 
     FIG. 8 is a perspective view of the connector module of FIG. 6; 
     FIG. 9 is an enlarged, fragmentary, side elevational view of the connector assembly of FIG. 2; and 
     FIG. 10 is an enlarged, fragmentary, side elevational view of the connector system of FIG. 6, wherein the connector module is connected to the connector assembly. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout and the thickness of elements may be exaggerated for clarity. 
     With reference to FIGS. 6 and 7, a connector system  10  according to the present invention is shown therein. The connector system  10  includes generally an electronic module  20  and a connector assembly  100 . The connector assembly  100  may be, for example, an RF distribution backplane of a cellular base station, and the module  20  may be an RF module or any other type of module which emits radio frequencies. The module  20  and the connector assembly  100  may be of conventional construction as appropriate for the intended application, except for the provision of a shield  150  of the present invention. The shield  150  as well as the connector assembly  100  and the connector system  10  incorporating the shield  150  are described in greater detail hereinbelow. 
     With reference to FIG. 1, the shield  150  is formed of an electrically conductive material and includes a body  152  having an outer face  156 A and an opposed inner face  156 B. The body  152  also has opposed side edges  154 A and  154 B, as well as opposed end edges  154 C and  154 D. Apertures  170  are formed through the body  152  adjacent the end edges  154 C,  154 D. An inner edge portion  172  of the body  152  surrounds each of the apertures  170 . The inner edge portion  172  includes opposed arcuate portions  174  and opposed tabs  176 . The tabs  176  extend inwardly into the respective apertures  170 . A plurality of spring members or fingers  160  extend outwardly from the edge  154 A and define slots  160 A between adjacent fingers  160 . The fingers  160  also extend outwardly beyond the outer face  156 A. As best seen in FIGS. 1 and 9, each finger  160  has an end  162  integral with the body  152 , an opposite, free end  164 , a concave first portion  166  and a convex second portion  168 . Preferably, each finger  160  is integrally formed with the body  152 . Preferably, the fingers  160  extend between about 0.050 and 0.25 inch outwardly beyond the outer face  156 A. Preferably, the shield  150  has a uniform material thickness throughout. More preferably, the thickness of the shield  150  is between about 0.003 and 0.005 inch throughout. Preferably, the shield  150  is formed of the same material throughout. Suitable materials include beryllium copper and stainless steel. Suitable materials may include commercially available finger stock stamped to provide the desired outer shape and to form the apertures  170 . Portions of the shield  150  may be formed of or coated with nonconductive material. Additional fingers (not shown) may extend from one or more of the outer edges  154 B,  154 C,  154 D as well. 
     With reference to FIGS. 2 and 3, and as noted above, the shield  150  is incorporated into the connector assembly  100 . The connector assembly  100  includes a backplane  110 , the shield  150 , connectors  120  and a shroud  130 . The several components of the connector assembly  100  will be described with reference to the steps for assembling the connector assembly  100 . 
     The backplane  110  has an outer face  112  and an opposed, inner face  114 . Rivet holes  118  are formed through the backplane  110 . The backplane  110  may be formed of conventional construction. The outer face  112  of the backplane  110  is electrically non-conductive and conductive elements such as printed circuits are disposed on the inner face  114  or on internal layers of the backplane  110 . 
     The connectors  120  extend through the backplane  110  through holes  116  from the inner face  114  to the outer face  112  and project above the outer face  112  as shown. The connectors  120  may be any suitable connectors, including DIN type connectors as shown. The connectors  120  are each grounded on the inner face  114  side or the internal layers of the backplane  110  (not shown). The connectors  120  are secured in position by any suitable means to resist displacement into or out of the backplane  110  or rotation with respect to the backplane  110 . With reference to FIG. 5, each connector  120  has an upper portion  122  and abase portion  124 . At least the base portion  124  is grounded by connection to the inner side or internal layers of the backplane  110 . Each connector  120  also has connection contacts  126  for engagement with the associated contacts of the module  20 . The connection contacts  126  are connected to pins  127  which extend from the inner side of the backplane  110  (see FIGS.  9  and  10 ). Means and methods for mounting connectors on backplanes as just described are well known to those of skill in the art and suitable constructions will be readily apparent to those of skill in the art upon a reading of the description herein. 
     After the connectors  120  have been mounted on the backplane  110 , the shield  150  is placed over the backplane  110  and the connectors  120  such that the connectors  120  are inserted through the apertures  170 . The shield  150  is seated on the connectors  120  by pushing the shield  150  down over the connector bases  124  until the inner face  156 B of the shield  150  abuts the outer face  112  of the backplane  110  to assume the position as shown in FIG.  4 . As best seen in FIG. 5, the apertures  170  are sized and shaped to provide close fit between the inner edges  172  and the bases  124 . In particular, the curved edges  174  are substantially complementary to the curved portions  124 B. Additionally, the tabs  176  are deflected about respective folds  178  and engage the adjacent flat walls  124 A of the base portions  124 . As a result, the tabs  176  serve as resilient, biased clips to resist removal of the shield  150  from the connectors  120 . The tabs  176  thereby can provide both metal to metal, electrical contact for grounding and mechanical securement to hold the shield  150  in place on the backplane  110 . The complementary shapes of the bases  124  and the apertures  170  facilitate location or registry of the shield  150  relative to the connectors  120  so that the shield is self-aligning. Notably, no tape, adhesive or fasteners (e.g. rivets, screws, or separate clips) are needed. 
     After the shield  150  is seated on the backplane  110  and the connectors  120  as shown in FIG. 4, the shroud  130  is mounted on the backplane  110 . The shroud  130  has an upper portion  134 , a base portion  136  and slots  138  extending fully through the shroud  130 . Recesses  134 A maybe formed in the upper portion  134  in conventional manner to key the connector assembly  100  to the module  20  as desired. The shroud  130  is placed over the shield  150  and the connectors  120  such that the connectors  120  are inserted into the slots  138 . The shroud  130  is pushed onto the connectors  120  until the bottom of the base portion  136  abuts the upper face  156 A of the shield  150 , thereby sandwiching the shield  150  between the backplane  110  and the shroud  130 . Reliefs may be formed in the lower edges of the shroud  130  to accommodate the thickness of the shield body  152 . Rivets  102  are installed through holes  132  and the holes  118 . The shroud  130  is preferably molded from glass reinforced thermoplastic. Notably, upon completion of the assembly of the connector assembly  100 , the fingers  160  extend outwardly from the side edge of the shroud  130  and above the outer face  112  of the backplane  110  (see FIGS.  2  and  9 ). 
     With reference to FIG. 8, the module  20  has a chassis  22  formed of conductive material such as aluminum. The chassis  22  defines a front slot  26  within which connectors  28  are disposed. The chassis  22  includes a sidewall  24  having a front end edge  24 A. The construction of the module  20  is conventional and may be modified as appropriate. 
     When one desires to connect the module  20  to the connector assembly  100 , the module  20  is inserted onto the connector assembly  100  such that the shroud  130  is received in the slot  26  and the connectors  28  engage the complementary connectors  120  in conventional manner. The shroud  130  serves as the connector body and as a guide for mating the connectors  28  on the module  20  with the connectors  120  during insertion. The shroud  130  also serves as a retainer housing for the connectors  28 ,  120 . 
     FIGS. 7 and 10 show the module  20  and the connector assembly  100  once connected to one another. With reference to FIG. 10, as the chassis  22  is inserted over the shroud  130 , the electrically conductive side wall  24  abuts the fingers  160  and deflects the fingers  160  downwardly toward the backplane  110 . Preferably, the chassis  22  displaces the fingers  160  downwardly a distance D of between about 0.050 and 0.150 inch. Because the fingers  160  are resilient, the fingers remain spring biased against the abutting end edge  24 A of the wall  24 . In this manner, electrical contact is maintained between the shield  150  and the chassis  22 . Because the shield  150  is electrically connected to the grounded connectors  120 , the chassis  22  is thereby grounded. 
     The foregoing shield  150 , connector assembly  100 , and connector system  10  can provide several significant advantages and benefits. The shield  150  may be installed without requiring any additional operation such as clearing or preparation, by machine or by hand. No modifications or alterations to the connectors  120 , the connector shroud  130 , or the backplane board  110  are needed to use the shield  150 . Thus, the shield  150  may be used with a variety of different types and configurations of connectors with no or little modification. Moreover, the presence of the shield  150  need not adversely impact the handling, usability or effectiveness of the connector system or require modification of other components. The spring fingers  160  can deflect and maintain contact with the module chassis  22  after insertion, regardless of slight tolerance differences in depth of insertion, or thermal expansion and contraction. The plurality of fingers  160  arranged in series can ensure that good contact is provided even if the module  20  is not well-aligned with the connector assembly  100 . In this manner, good electrical ground contact can be made and maintained between the module  20  and the shield  150 , and thereby between the module  20  and the connectors  120 . Because adhesives are not required, the connector assembly  100  is well suited for outdoor use. 
     The module chassis  22  itself provides an RF shield on all sides except its rear face. The shield  150  forms the missing shield side when the module  20  is mounted on the connector assembly  100 . 
     Those of skill in the art will recognize that the shield and the assemblies and systems described above may be used with or incorporate types of connectors, chassis, shrouds and backplanes than those described herein. Moreover, the shield may be shaped and sized differently than as shown and described herein. 
     It is also contemplated that shields such as or similar to the shield  150  may be secured to the backplane by means other than or in addition to the apertures  170  and the tabs  176 . Such means may include adhesives, screws, rivets or separately formed clips. However, such means are generally not preferred because they may be unsuitable for outdoor use (e.g., because of the use of adhesives), may present additional assembly steps or parts and complexity (e.g., screws, rivets and clips), and/or may adversely affect the performance or require modification of the connector system. 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.