Recessed aperture-coupled patch antenna with multiple dielectrics for wireless applications

[0002] The field of the invention relates to antennas, and particularly to patch antennas recessed within housings of electronic devices such as computers.

[0003] Patch antennas, also called microstrip patch antennas, are common in the art. A exemplary patch antenna may include a transmission line feed, multiple dielectrics, and a metallized patch on one of the dielectrics. Conventional patch antennas are directly coupled to their feeds by coaxial cables.

[0004] When conventional patch antennas are used in electronic devices two disadvantages result. First, the coaxial cable connection requires manual disassembly if the antenna or the element to which the antenna is affixed or incorporated is extracted from the electronic device. Second, the patch antenna assembly often noticeably protrudes from the housing of the electronic device and detracts from the device's cosmetic appearance.

[0005] A solution is needed that provides a patch antenna assembly that is easily extracted from its feed with minimal or no disassembly by the user. Additionally, the patch antenna assembly should be capable of being virtually hidden within an external housing of an electronic device.

[0006] The present invention provides an aperture-fed patch antenna assembly that is recessed into a conductive surface of an external shell of an electronic device. In one embodiment, an antenna feed attached to a removable core of the electronic device may be removed from the external shell without requiring a manual disconnecting of the antenna feed from a wireless radio modem in the electronic device. The patch antenna assembly includes a shim having an aperture therein and positioned between a primary dielectric and a printed circuit board to create a secondary dielectric between the primary dielectric and the printed circuit board. In one embodiment, the primary dielectric is ceramic and the shim is plastic.

[0007] The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which

[0008] FIG. 1ais an exploded perspective view of a recessed patch antenna assembly according to one embodiment of the invention;

[0009] FIG. 1bis a side view of a recessed patch antenna assembly according to one embodiment of the invention; and

[0010] FIG. 2 is a side view a patch antenna assembly coupled with a removable antenna feed according to another aspect of the invention.

[0011] A recessed aperture-coupled patch antenna assembly is disclosed. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details need not be used to practice the present invention. In some circumstances, well-known structures and materials have not been shown or described in detail in order not to unnecessarily obscure the present invention.

[0012] Referring now to FIG. 1a, an exploded perspective view of a patch antenna assembly is shown. Two opposing panels 102 and 104 of four-sided chassis (not shown) are illustrated. The remaining two panels have been omitted from FIG. 1ato show the various components of the patch antenna assembly. Panels 102 and 104 contain openings 103 for the ceramic antenna dielectrics 105, which support antennas 113 (metallized layers on ceramic antenna dielectrics 105). In one embodiment, the metallization forming the antennas 113 is aluminum, but other similar metals maybe used. Shims 107 contain openings 106 to form an air gap and have front sides and back sides. The front sides of shims 107 are coupled to the antenna dielectrics 105, and the back sides of shims 107 are coupled to printed circuit boards 115 to create secondary dielectrics between the printed circuit boards 115 and antenna dielectrics 105. Shields 111 are coupled with printed circuit boards 115 to shield the printed circuit boards from internal electromagnetic interference (EMI). Additionally, the printed circuit boards 115 containing transmission antennas (not shown) are coupled together using coaxial cable 117. Another coaxial cable 119, coupled with one of the printed circuit boards 115 couples the circuit boards to a radio modem (not shown) installed in a removable core (not shown) of the electronic device.

[0013] FIG. 1bis a side view of panel 104 illustrating a recessed patch antenna according to one aspect of the invention. In FIG. 1b, antenna dielectric 105 is positioned within an opening in chassis 104 such that antenna 113 is substantially coplanar with the exterior surface of panel 104. A printed circuit board assembly (not shown) may be coupled with shim 107, which is positioned adjacent to the backside of antenna dielectric 105.

[0014] When shim 107 is placed between the printed circuit board assembly (not shown) and antenna dielectric 105, the aperture 106 in shim 107 creates an air gap, which serves as a secondary dielectric. Shim 107 ensures that the distance between printed circuit board 115 and antenna dielectric 105 is optimal for effective antenna operation. If shim 107 is not provided, it is difficult to maintain the optimal distance within economically manufacturable tolerances. Additionally, in one embodiment, shim 107 prevents antenna dielectric 105 from touching printed circuit board 115. In another embodiment, where the antenna feed is not a printed circuit board, the shim 107 prevents antenna dielectric 105 from touching the antenna feed.

[0015] Referring again to the embodiment illustratively shown in FIG. 1a, an air gap is formed between antenna dielectric 105 and printed circuit board 115 by aperture 106 in shim 107. Because the air gap serves as a secondary dielectric, the depth of the air gap is critical to the tuning of the antenna. In one embodiment, the depth of the air gap corresponds to the thickness of shim 107, which may be used to maintain the air gap at an optimal distance and to prevent direct (and potentially damaging) contact between the ceramic disk 105 and the printed circuit board 115. The optimal distance between printed circuit board 115 and antenna dielectric 105 varies according to the type of material used in the primary dielectric and according to the particular frequency used. For example, the optional distance may range from approximately 0.5 mm to approximately 4.0 mm in the 2.5 GHz frequency range. However, this range will vary depending upon the actual frequency, the configuration, and operating conditions used. Once determined the optimal distance should be maintained within a narrow +/− tolerance, illustratively, and not by way of limitation, approximately +/−0.25 mm in the 2.5 GHz frequency range. The exact amount of tolerance is driven by the ratio of the thickness of antenna dielectric 105 to the thickness of the air gap and the dielectric constant of the dielectric. For example, using polycarbonate instead of ceramic to form the antenna dielectric may change the optimal distance and the +/− tolerances, because polycarbonate has a constant different from the dielectric constant of ceramic. In other embodiments, the antenna dielectric may be made of other materials such as plastic and fiberglass, but use of these other materials will also change the optimal distance and the +/− tolerances.

[0016] In the embodiment shown in FIG. 1a, positioning antenna dielectrics 105 on opposite sides of the chassis (not shown) introduces directionality in the antennas 113. However, the antennas 113 are carefully chosen to be well suited for this directionality; and the diversity in the antenna set enables the antennas 113 to cover the entire space around the chassis. Although two antennas 113 are illustratively shown in FIG. 1a, another embodiment of the invention may include only a single recessed patch antenna assembly or may include more than two recessed patch antenna assemblies.

[0017] FIG. 2 illustrates a side view of a patch antenna assembly according to another embodiment of the invention, in which an antenna 201 is positioned on the exterior of a ground plane. In this embodiment, antenna 201 coupled with an outer surface of antenna dielectric 203. The inner surface of dielectric 203 spans an opening in a ground plane 209, which may be a conductive surface on an external shell of an electronic device. Shim 205 positioned on the interior side of the ground plane maintains an antenna feed 207, such as a printed circuit board containing a transmission line antenna, at an optimal distance from dielectric 203 by forming an air gap 215 between antenna dielectric 203 and antenna feed 207. In this embodiment, antenna 201 and/or at least a portion of dielectric 203 protrude past the exterior surface of ground plane 209. This embodiment, like that of FIG. 1, permits a core of the electronic device (not shown) to be removed from the external shell (ground plane) without disconnecting the antenna feed from a radio modem installed in the electronic device. In one embodiment, antenna dielectric may be mounted within a recessed area formed in the outer surface of ground plane 209. This recessed area may, in another embodiment , have a depth approximately equal to the combined thickness of antenna dielectric 203 and antenna 201, such that the exterior surface of antenna 201 is substantially co-planar with the exterior surface of ground plane 209.

[0018] In one embodiment, the present invention provides a patch antenna that uses an aperture feed. The antenna assembly includes a printed circuit board having a transmission line as a feed, and a diversity switch; a ceramic disk as a primary dielectric; an air gap between the printed circuit board and the ceramic disk as a secondary dielectric; a shim with an opening to control the depth of the air gap; and a metallized patch on one side of the ceramic disk. In this embodiment, the metallized patch serves as an antenna, the printed circuit board serves as the antenna feed, and connection between the two is made by proximity alone. Although illustratively shown as a printed circuit board, the antenna feed does not have to be fabricated as a printed circuit board.

[0019] In one embodiment, the assembly is recessed into the conductive surface (Faraday/EMI cage) of the housing (external shell) of an electronic device, such as a computer, which includes an internal core. This core, to which is attached the printed circuit board with transmission line antenna, is removable from the external shell. The ceramic disk with metallized patch is attached to this external shell. Further cosmetic treatment is used to camouflage the metallized patch and underlying antenna dielectric to provide a virtually hidden antenna for wireless communications. This embodiment allows the external shell to be removed from the computer core without disconnecting the antenna from the wireless radio modem in the product.

[0020] In one embodiment, the antenna may transmit and receive radio waves in about the 2.5 GHz range to enable wireless communications.

[0021] Although the present invention is described herein with reference to a specific preferred embodiment, many modifications and variations therein will readily occur to those with ordinary skill in the art. Accordingly, all such variations and modifications are included within the intended scope of the present invention as defined by the following claims.