Abstract:
A hybrid shield and antenna unit for a printed circuit board is disclosed. A shielding enclosure for providing RF and electromagnetic shielding of the electronic components of a circuit board is integrated with an antenna as a single unit. The hybrid shield and antenna combination may be fabricated as a single unit to provide for reduced steps in the manufacturing process thereby leading to improved economy. The hybrid shield and antenna includes a shielding enclosure for providing RF and electromagnetic shielding of an electronic component, and an antenna disposed at an end of said central enclosure, wherein the antenna and the central enclosure comprise a single continuous unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application hereby claims the benefit under 35 U.S.C. § 119(e) to provisional patent application Serial No. 60/043,488 filed Apr. 10, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of shielding printed circuit boards, and more particularly to a single shield and antenna apparatus for a printed circuit board. 
     BACKGROUND OF THE INVENTION 
     There are many applications in which it is desirable to be able to reduce the cost of construction and assembly of components and structures in electronic devices by combining the functions of multiple devices into a single structure. For example, in a hand-held portable computer, the display is often directly integrated directly into the computer housing. Thus, the hand-held computer may be made smaller, more portable and more rugged by having a single unit serving as the housing for the computer circuit boards and for the display. 
     In addition, it is often desirable to be able to reduce manufacturing costs by producing a single structure which simultaneously serves multiple functional purposes. For example, since an electromagnetic shielding device and an antenna must both be made of a material having a high conductivity (e.g., metal), economies of production may be realized by fabricating both the shield and the antenna from a single piece of material, thereby reducing the number of steps in required to be performed in the fabrication and assembly processes. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a goal of this invention to provide a hybrid shield and antenna for providing combination RF and electromagnetic shield and antenna apparatus. 
     The present invention is directed to a hybrid shielding and antenna apparatus. In one embodiment, the hybrid shield and antenna includes a shielding enclosure for providing RF and electromagnetic shielding of an electronic component, and an antenna disposed at an end of the central enclosure, wherein the antenna and the central enclosure comprise a single continuous unit. 
     The present invention is further directed to a shielding and radio-frequency radiator and receiver system. In one embodiment, the system includes a circuit board being generally planar and having an upper and a lower surface, the circuit board comprising a dielectric material for providing a mounting surface for an electronic component, a ground plane formed on the lower surface of the circuit board for approximating a conducting radio-frequency ground, and an enclosure disposed upon the upper surface of the circuit board and encompassing the electronic component for providing radio-frequency electromagnetic shielding of the electronic component, the enclosure having a portion thereof formed into an antenna for receiving and transmitting electromagnetic energy. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous objects and advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
     FIG. 1 is an illustration of an exemplary embodiment of a hybrid shield and antenna apparatus of the present invention; 
     FIG. 2 is an illustration of a pre-formed flattened shape of the hybrid shield and antenna of FIG. 1 in accordance with the present invention; 
     FIG. 3 is an illustration of a top plan view of the hybrid shield and antenna shown in FIG. 1; 
     FIG. 4 is an illustration of an end elevation view of the hybrid shield and antenna shown in FIG. 1; 
     FIG. 5 is an illustration of a top plan view of a pre-formed alternative hybrid shield and antenna of the present invention; 
     FIG. 6 is an illustration of an alternative hybrid shield and antenna of the present invention based upon the pre-form pattern shown in FIG. 5; 
     FIG. 7 is an illustration of a top plan view of a pre-formed further alternative hybrid shield and antenna of the present invention; and 
     FIG. 8 is an illustration of a further alternative hybrid shield and antenna of the present invention based upon the pre-form pattern shown in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the presently preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. 
     Referring now to FIG. 1, an exemplary embodiment of the present invention is shown. The essence of the invention lies in a combination, or hybrid, shield and antenna  10 . The hybrid shield and antenna  10  comprises a central enclosure  12  which functions as a shielding structure for providing RF and electromagnetic shielding of electronic circuitry disposed internally therein. The electronic circuitry may be components disposed on a circuit board  14  on which the hybrid shield and antenna  10  is utilized. The hybrid shield and antenna  10  includes one or more antenna structures  16  and  18  which may be disposed at corners  20  and  22  of the central enclosure  12 . Each antenna  16  and  18  may comprise radiating elements  24 ,  26 ,  28  and  30  which may vary in structure and form according to the particular type and design of the antennas  16  and  18 . For example, the antennas may be designed as bow-tie antennas, quarter-wavelength or half-wavelength, etc. 
     The term antenna as referred to herein may include any device which confines accelerating electrical charges to produce or receive far field traveling wave energy with the desired directional and polarization properties. The antennas  16  and  18  may be constructed according to design criteria to provide a structure that is reasonably sized, light weight, robust, inexpensive, and reliable and has the desired electromagnetic properties for the given application. The preferred applications of the hybrid shield and antenna  10  of the present invention include portable, hand-held electronic computer-based data collection and processing terminals. 
     Ideally, the antennas  16  and  18  of the present invention are isotropic antennas in that the antennas radiate equally in all directions. The antennas  16  and  18  of the present invention may comprise, but are not limited to, any of the following types of antennas: Adcock, Alexanderson, anisotripoc, bent, biconical, bobtail curtain, bow tie, center feed, circular, coaxial, conical, corner reflector, cross-antenna, current feed, current loop, current node, delta matched, diplex, dipole, doublet, directional, discone, dish, double-V, double-zepp, drooping radial, end feed, end fire, extended double-zepp, ferrite rod, fishbone, flagpole, flat top, folded dipole, Fuchs, ground plane, half-wave, halo, herp, helical, Hertz, horn, inverted-L, isotropic, J-antenna, J-pole, Kooman, L-antenna, lead-in, loaded, loading disk, log-periodic, long wire, loop, Marconi, monopole, multi-band, multi-element, multiplex, noise-reducing, off-center feed, omnidirectional, phased array, polyphase, quad, rhombic, side stacking, sleeve, spherical, spider web, stacking, Sterba, T-antenna, tapered feed line, top-loaded, trap, turnstile, umbrella, unidirectional, V-beam, vertical, vertical dipole, whip, window, wire, Yagi, or Zeppelin. 
     Referring now to FIG. 2, a hybrid shield an antenna of the present invention in a pre-formed flattened shape is shown. The hybrid shield and antenna  10  is preferably fabricated from a single sheet of material. The shield and antenna  10  may be fabricated with an etching process to produce the necessary structural elements comprising the shield and antenna unit. For example, in the etching process in which the hybrid shield and antenna  10  is formed, an unformed metal plate may be coated with an acid-resistant ground covering an entire surface thereof. The desired shape or image of the hybrid shield and antenna structure is then drawn or traced into the ground, thereby exposing the metal areas in the plate to be removed in forming the desired structures. The plate may then be immersed in an acid bath such that the acid dissolves away only areas from which the acid-resist has been removed, the rest of the areas being protected from reacting with the acid by the ground. After the acid has completely dissolved the exposed areas of the plate, the acid-resist is then removed from the remaining metal in the pre-formed desired shape. 
     The pre-formed desired shape of the hybrid shield and antenna  10  is depicted in FIG.  2 . Flaps  32  and  34  may be folded along fold lines  36  and  38 , respectively, to form vertical end surfaces of the central enclosure  12 . Similarly, flaps  40  and  42  may be folded along fold lines  44  and  46 , respectively, to form vertical side surfaces of the central enclosure  12 . The remaining central surface  48  of the pre-formed shape is thereby becomes the top surface of the central enclosure  12  such that the central enclosure is elongate and generally rectangularly shaped, although other similar shapes may be formed as well. Extensions  50 ,  52 ,  54  and  56  may be folded along fold lines  58  and  60 ,  62  and  64 ,  66  and  68 , and  70  and  72 , respectively, to arrive at the necessary shape and structure of the radiating elements  24 ,  26 ,  28  and  30 . For example, the structure of the radiating elements  24 ,  26 ,  28  and  30  may be generally triangular to implement bow tie type antennas. A bow tie antenna is a broadband antenna typically utilized for transmitting and receiving vhf and uhf frequencies down to approximately 20 MHz. A bow tie antenna typically comprises two triangular pieces of stiff wire or flat metal plates wherein the transmission line feeds at the apexes of the triangles. A reflecting screen may be disposed on a side of the bow tie radiators to provide a unidirectional operation if so desired. In the present invention, vertical sides  34  and  40  of the central structure  14  may function as such a reflecting screen, for example. 
     Alternatively, radiating elements  50 ,  52 ,  54  and  56  may be formed to implement a bent antenna. A bent antenna may be generally considered as any antenna with a radiating element that is not straight. A bent antenna configuration is typically utilized in installations that cannot accommodate a full-sized antenna for the desired operational frequency. The utilization of a bent antenna may be desirable in a handheld portable electronic device such as a portable computer terminal of compact design wherein usable space is only available at a design premium. 
     Referring now to FIGS. 3 and 4, a top plan and an end elevation view, respectively, of the hybrid shield and antenna  10  of the present invention are shown. The central enclosure  12  is shown as providing an RF or electromagnetic shield enclosure for internal electronic components  74  for which shielding is required. For example, the internal electronic components  74  may be the components of an RF transceiver operating at radio-frequencies disposed on circuit board  14 . At such frequencies, the internal electronic components  74  may produce undesirable radio-frequency electromagnetic radiation which would otherwise adversely interfere via reactive coupling with the operation of nearby exterior electronic components also disposed on circuit board  14  without the shielding effects of the hybrid shield and antenna  10 . 
     Alternatively, external electronic components  76  may comprise an RF transceiver to be protected from electromagnetic interference from internal electronic components which may be data circuits operating at high switching speeds, for example. In this situation, the shielding structure  12  protects the external electronic components  76  from electromagnetic radiation emanating from internal data circuits  74  which would otherwise interfere with the operation of the external RF transceiver  76 . Without the shielding action provided for data circuits  74  by the shielding structure  12 , the RF transceiver would undesirably broadcast the high speed switching signals thereby interfering with RF communications. Conversely, enclosure  12  protects electronic components  74  from RF interference generated by electronic components  76 . 
     As shown in FIG. 3, antenna  18  is connected to electronic circuit components  74  via traces  19  and  21 . Traces  19  and  21  serve as a transmission line for coupling antenna  18  to electronic components  74  such that signals generated by electronic components  74  may be transmitted via antenna  18 , or such that signals in the form of electromagnetic waves may be received by antenna  18  and transmitted to electronic components  74 . 
     Referring more specifically to FIG. 4, the circuit board  14  of the present invention is shown having an electrical connection plane  78  having electrical traces  80  thereon for forming connections between the electronic components  74  and antenna  18  of the circuit board  14 . Electrical traces  80  may correspond to the transmission line traces  19  and  21  of FIG.  3 . Electrical traces  80  of electrical connection plane  78  may comprise standard solder traces, for example. Alternatively, electrical traces  80  of electrical connection plane  78  may comprise microstrip traces, planar transmission lines comprising thin conducting strips of finite width typically utilized to form an unbalanced transmission line for implementing an image conductor in conjunction with a ground plane  82 . The microstrip traces may be utilized as transmission lines to feed the signal from the circuits  74  and  76  to the antennas  16  and  18  to minimize external radiation since the effective current in the image conductor is equal in magnitude but opposite in direction to the current in the actual conductor. Connection vias  84  provide passageways and connections through the circuit board  14  to allow for the electronic components  74  and  76  to connect to electrical traces  80  and ground plane  82  of the electrical connection plane  78 . 
     Connection via  83  connects enclosure  12  to shield plane  82 , thereby improving the shielding effectiveness and continuity of hybrid shield and antenna  10 . Connection vias  85  and  87  connect circuit components  74  and antenna  18  to electrical trace  80  such that signals may enter or leave enclosure  12 . 
     Referring now to FIG. 5, a top plan view of a pre-formed hybrid shield and antenna of the present invention is shown. Through variations in the etching process by which the hybrid shield and antenna  10  of the present invention is formed, various types of antennas may be formed. For example, the bow tie antenna configuration as shown in FIG. 2 in which the wire strip form of bow tie antennas  16  and  18  is utilized may be an alternative form of bow tie antennas  86  and  88  as shown in FIG.  5 . The radiating elements  90  and  92  and  94  and  96  of bow tie antennas  86  and  88 , respectively, may comprise flat metallic sheets rather than the wire strip form of FIG.  2 . Thus, radiating elements  90 ,  92 ,  94  and  96  may be folded about fold lines  98 ,  100 ,  102  and  104 , respectively, to form complete bow tie antennas  86  and  88  of the hybrid shield and antenna  10  of FIG.  6 . Feed points  99  of radiating elements  90 - 94  provide a point at which electrical traces such as traces  19  and  21  may connect to electronic components  74 . 
     Referring now to FIG. 6, a hybrid shield and antenna of the present invention is shown illustrating an alternative form of antennas. The hybrid shield and antenna  10  depicted in FIG. 6 is the resulting product when the pre-formed shield and antenna piece  10  of FIG. 5 is formed into a completed unit. The vertical surfaces  34  and  40  of the central enclosure  12  may function as reflecting screens in a manner substantially similar to the manner described with respect to the hybrid shield and antenna embodiment of FIG.  1 . Feed points  99  of radiating elements  90 - 96  provide a point at which electrical traces such as traces  19  and  21  may connect to electronic components  74 . 
     Referring now to FIGS. 7 and 8, a hybrid shield and antenna of the present invention is shown further illustrating an alternative form of antenna. As the antennas  16  and  18  of FIGS. 1 and 2 may be modified to implement antennas  86  and  88  of FIGS. 5 and 6, many various modifications in the antenna form factor may be achieved as further illustrated in FIGS. 7 and 8. For example, the hybrid shield and antenna  10  may include only a single antenna  106  disposed at a corner  20  of the hybrid shield and antenna  10 . The antenna  106  may include radiating elements  108  and  110  which are similar to radiating elements  90  and  92  of antenna  86  of FIG. 5, for example, with the exception of having triangularly shaped hollow central regions  112  and  114 . It may be desirable for radiating elements  108  and  110  to include hollow central regions  112  and  114  to improve or modify the effective reflective surface area of the surfaces  34  and  40  in acting as reflectors for antenna  106  in order to thereby achieve an appropriate gain or main lobe and side lobe patterns of the antenna  106 , for example. Feed points  109  of radiating elements  108  and  110  provide a point at which electrical traces such as traces  19  and  21  may connect to electronic components  74 . 
     Thus, the antenna form factor of the present invention may be designed according to design criteria necessary to implement the desired antenna operational characteristics. Such design criteria may include, for example, power gain, main beam lobe and side lobe patterns and sizes, polarization, axial ratio, directivity, bandwidth, operational frequency and wavelength, voltage standing wave ration (VSWR) and effective area. 
     It is believed that the hybrid printed circuit board shield and antenna of the present invention and many of its attendant advantages will be understood by the forgoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages, the form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.