Abstract:
An architecture for providing a low cost, high performance antenna for small devices In particular, a rotatable antenna that having three antenna elements; a primary element consisting of a radiating element and swiveling cylindrical head, a secondary element that consists of a feeding cylindrical pin attached vertically to an electronic device main board, and a third element that consists of a plastic part over-molding the secondary element to permit electromagnetic coupling accuracy between the primary and secondary elements.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to an antenna, and more particularly, to an architecture for a rotatable antenna for small devices with a radiating element and a swiveling coupler. The coupler is electromagnetically coupled to a pin rigidly connected to a PCB. 
       BACKGROUND INFORMATION 
       [0002]    Recently small media streaming devices has become common on the marketplace. These devices stream media wirelessly from the internet and user wireless remote controls to control the device. Turning now to  FIG. 1 , two examples  100  of media streaming devices  110 ,  120  are shown. These very low-cost pocket-size set-top-boxes or media sticks integrate a wireless communications system in order to communicate with other devices, such as gateways, PCs, routers, remote controls, smartphones, tablets, etc. The antennas are mostly embedded in the housing, as is shown with the first media device  110  but some devices are equipped with an external antenna as is shown with the second media device  120 . External antennas afford better wireless transmission performance than the embedded because of a better radiation efficiency and a better radiation pattern of the antenna. 
         [0003]    Generally, wireless antennas embedded in small electronic devices, such as USB dongle devices, exhibit very poor performance, in terms of gain, radiation efficiency and radiation pattern. The size of the small electronic device does not enable optimal antenna design as the smaller the size of an antenna with respect to the radiating wavelength, the lower its radiation efficiency. Antenna electromagnetic behavior is very sensitive to conductive objects in its close environment, such as interface connectors, circuit shielding covers, cables, and shielded equipment housings to which the small device is connected. In addition, embedded antennas are often printed on the main circuit board. When a device with an embedded antenna is placed in the back side of a display, the wireless connection could be drastically impaired because of a lack of “visibility”. 
         [0004]    Therefore, it is desirable to provide a compact, low cost, external antennas which can be configured by a user, in a way to avoid these undesirable wireless performance issues and to offer a more flexible way to improve the coverage performance according the conditions of visibility of the device. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with an aspect of the present invention, an antenna is disclosed comprising a feed element, a first element having a cylindrical portion, a second element fixed to said feed element, and a third element fixed to said second element and rotationally fixed to an outside surface of said cylindrical portion of such that a space is maintained between said cylindrical portion and said second element. 
         [0006]    In accordance with another aspect of the present invention, an apparatus is disclosed comprising a printed circuit board, a cylindrical antenna element affixed at one base to the printed circuit board such that an axis of said cylindrical antenna element is orthogonal to a plane of said printed circuit board, a radiating antenna element having a hollow cylindrical portion, wherein said hollow cylindrical portion is positioned over a portion of said cylindrical antenna element, and a nonconductive element affixed to a portion of said cylindrical antenna element and positioned over said hollow cylindrical portion such that a gap is maintained between said cylindrical antenna element and said hollow cylindrical portion. 
         [0007]    In accordance with another aspect of the present invention, a rotatable antenna is disclosed comprising a first element electrically coupled to a printed circuit board, where the first element comprises a first cylindrical portion, a second element having a second cylindrical portion, said second cylindrical portion having a cavity for receiving said first cylindrical portion such that said second element rotates around an axis of said first element, and a third element immovably fixed to a portion of said first element and movably fixed to a portion of said second cylindrical portion such that said second cylindrical portion is prevented from touching said first cylindrical portion. 
         [0008]    In accordance with another aspect of the present invention, an apparatus is disclosed comprising a printed circuit board, an enclosure for enclosing at least a portion of said printed circuit board, said enclosure having a circular aperture over a portion of said printed circuit board, a cylindrical antenna element affixed at to the printed circuit board such that an axis of said cylindrical antenna element is orthogonal to a plane of said printed circuit board, said axis also being in alignment with said aperture, and a radiating antenna element having a cylindrical portion, wherein said cylindrical portion is positioned over a portion of said cylindrical antenna element, and wherein said cylindrical portion is positioned within said aperture of said enclosure such that cylindrical portion is movably retained by said enclosure such that a gap is maintained between said cylindrical antenna element and said cylindrical portion 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a diagram showing prior art example of small wireless media devices; 
           [0011]      FIG. 2  is a diagram of device showing an exemplary embodiment the present invention; 
           [0012]      FIG. 3  is a diagram and cross section and perspective view of an exemplary rotational portion of the rotational antenna is shown; 
           [0013]      FIG. 4  is a diagram showing a second cross section of exemplary rotational portion of the antenna  400  according to the present invention; 
           [0014]      FIG. 5  is a diagram is shown of a perspective view of an exemplary rotating portion of the antenna; 
           [0015]      FIG. 6  is an exemplary printed circuit board configuration according to the present invention; and 
           [0016]      FIG. 7  is an exemplary of the mechanical dimensions of an antenna for a particular application in the Wi-Fi 2.4GHz band according to the present invention. 
       
    
    
       [0017]    The exemplifications set out herein illustrate preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    As described herein, the present invention provides an architecture for a rotatable compact antenna for use in electronic products. While this invention has been described as having a preferred design, the present invention can be further modified within the scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. 
         [0019]    Referring now to the drawings, and more particularly to  FIG. 2 , an exemplary embodiment of a device  200  embodying aspects of the present invention is shown. The exemplary device  200  consists of a printed circuit board  210 , a device housing  220 , and a rotational antenna  230 . The device  200  may be a small “set back” box which receives streaming media wirelessly from a gateway server or a router to the device  200  and wirelessly transmits control information back to the server. The housing  210  may be constructed of metal or plastic. A plastic housing  210  may include some conductive shielding elements to reduce the transmission of unwanted electromagnetic interference. These conductive shielding elements may be coupled to the housing or to the printed circuit board  220 . 
         [0020]    The printed circuit board  220  is mounted within the housing  210  and includes a wireless transmitter, a wireless receiver, and a processor among other functional circuitry. The printed circuit board  220  has components affixed to one or more surfaces of the circuit board  220  including a portion of the rotational antenna  230 . The portion of the rotational antenna is electrically coupled to the transmitter and receiver portions of the device  200 . 
         [0021]    Turning now to  FIG. 3 , a diagram and cross section and perspective view  300  of an exemplary rotational portion of the rotational antenna is shown. The rotatable antenna  230  comprises three antenna elements, the primary element  310 , the secondary element  320  and the third element  330 . The primary element  310  comprises a radiating metal element connected to a cylindrical swiveling head that may be coupled to the antenna assembly through an aperture made in the device housing. This primary element  310  includes also a cylindrical cavity which is coaxially aligned with the secondary element  320 . This secondary element comprises a conductive cylindrical pin which is attached perpendicularly by soldering or conductively coupling to the printed circuit board  340  of the device. As shown in 
         [0022]      FIG. 3 , the lower portion of the secondary element  320  may have a narrower diameter than the upper portion of the secondary element  320 . The diameter of each portion of the secondary element  320  can be changed in response to design requirements and are not required to be differing diameters. The upper portion of the secondary element  320  is inserted in the air cavity of the primary element  310 . Both elements are not physically connected but air-spaced. Alternatively, a dielectric spacer may be used to aid in isolating the primary element  310  from the secondary element  320 . The primary element  310  rotates around the coaxial axis. Thus, the primary element  310  is first fed a signal by the secondary element  320  using the electromagnetic coupling between the secondary element  320  and the primary element  310  across the air gap. 
         [0023]    Ideally, a relative consistent tolerance is desired on the electromagnetic coupling for the distance between the primary element  310  and the secondary element  320 . The third element  330  is introduced to maintain the spacing. This third element  330  consists of a dielectric part, over-molding a portion of the second element  320 , with a base lying onto the printed circuit board  340 , and comprising a cavity hosting the swiveling head of the first element  310 . 
         [0024]    The design of the third element  330  aims at accommodating several requirements. To ensure the perpendicularity of the secondary element with respect to the PCB plane, the base of the third element  330  is mounted on top of the printed circuit board  340  and over-molded on the secondary element  320 . To ensure that the primary element  310  and the secondary element  320  are correctly aligned coaxially the cylindrical portion of the primary element  310  is hosted in the cavity of the secondary element  320  with tight tolerances. By this way, the desired air spacing in the XY plane, between the primary and secondary elements, is also maintained. Finally, to maintain the required air spacing in the Z axis, the cylindrical portion of the primary element  310  is abutted against the hosting internal base of the third element  330 . In addition, a clip (not shown) on top of the third element  330  restricts the withdrawal of the primary element  310  from the hosting third element  330 . 
         [0025]    In the perspective view, the primary element  310 A is shown with a cylindrical portion inserted in the third element  330 A, such that the radiating portion of the primary element can rotate in the plane of the printed circuit board  340 A. The third portion keeps the primary portion  310 A consistently coupled to the radiating portion of the secondary element (not shown). There plane of rotation is not limited to the angle formed by the radiating portion of the printed circuit board  340 A. The radiating portion may be bent, or the elements may be modified in such a way that rotation occurs in a plane other than that of the printed circuit board  340 A. 
         [0026]    The third element  330  may be molded with a key or flange operative to engage a groove on the primary element  310 . Thus, the primary element  310  can be rotated without becoming disengaged from the third element  330 . As show in  FIG. 3 , the third element has a small upper portion with a smaller inner diameter than the rest of the third element. This small upper portion is designed to mate with a small portion of the outer surface of the cylindrical cavity of the primary element. The small portion of the outer surface of the cylindrical cavity has a smaller outer diameter than the rest of the cylindrical cavity. Thus, when the cylindrical cavity is inserted into the third element  330  the small upper portion of the third element engages with the small portion of the outer surface of the cylindrical cavity in such a way that a resistance is created. This resistance prevents the primary element from being extracted from the third element during normal operation. Once enough force is applied to overcome the resistance, the primary element can be extracted. 
         [0027]    Turning now to  FIG. 4 , a second cross section of exemplary rotational portion of the antenna  400  according to the present invention is shown. A printed circuit  470  is shown mounted within a portion of a product enclosure  440 . A feed element  410  of the secondary element is shown conductively coupled to the printed circuit board  470  such that said feed element  410  is positioned perpendicular to the plane of the printed circuit board  470 . The feed element is coupled to an upper portion  480  of the secondary element. The upper portion  480  of the secondary element is shown spaced from the primary element  420  by a dielectic gap  430 . The dielectric gap may include plastic, air, or another non conductive material. In this exemplary embodiment, the product enclosure  440  is used to hold the rotating cylindrical portion of the primary element  420 . The printed circuit board  470  is also affixed to the product enclosure  440  thereby maintaining the geometry between the upper portion of the secondary element  480 . A conductive printed circuit board trace  450  is used to conduct the signal to be transmitted or received by the antenna to further processing circuitry. 
         [0028]    Turning now to  FIG. 5 , a perspective view of an exemplary rotating portion  500  of the antenna is shown. In this embodiment, the rotational antenna structure  530  is shown affixed to the printed circuit board  510 . The third element  550  is used to maintain spacing between the primary element and the secondary element. In this exemplary embodiment, the third element  550  is rigidly affixed to the printed circuit board  510  and is independent of the product enclosure  520 . An impedance matching circuit  540  is shown on the printed circuit board  540 . The printed circuit board  510  is shown mounted inside a product enclosure  520 . The product enclosure  520  may have a cover with an aperture to permit the extension of the rotatable antenna. Alternatively, a cover may be omitted. 
         [0029]    Turning now to  FIG. 6 , an exemplary printed circuit board configuration  600  according to an aspect of the present invention is shown. The printed circuit board  620  has affixed to a surface a metalized via-hole  610  in which is inserted the feeding pin of the secondary element (not shown). The secondary element and the associated third element can be mounted on the printed circuit board  620  following a common surface mount technology (SMT) process, with wave-soldering process or the line performed on the bottom side. A signal is then fed to the pin through an impedance matching circuit  630 , for example an L-shape type, and a microstrip line  640 . 
         [0030]      FIG. 7  is an exemplary of the mechanical dimensions of an antenna for a particular application in the Wi-Fi 2.4 GHz band according to an example of the present invention. 
         [0031]    The following table shows the values of the parameters of the antenna of the example shown in  FIG. 7 . 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Parameter 
                 Definition 
                 Value (mm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 H0 
                 PCB thickness (ground 
                 1.0 
               
               
                   
                   
                 plane at 0.125 mm below 
               
               
                   
                   
                 the top surface) 
               
               
                   
                 H1 
                 Antenna rectangular arm 
                 1.0 
               
               
                   
                   
                 thickness 
               
               
                   
                 H2 
                 Top cover thickness 
                 1.5 
               
               
                   
                 H3 
                 Height of the small 
                 2.0 
               
               
                   
                   
                 diameter of the feeding pin 
               
               
                   
                   
                 (from the PCB) 
               
               
                   
                 H4 
                 Height of the large 
                 2.3 
               
               
                   
                   
                 diameter of the feeding pin 
               
               
                   
                 H5 
                 Total height of the 
                 4.3 
               
               
                   
                   
                 rotatable antenna head 
               
               
                   
                 D1 
                 The small diameter of the 
                 1.0 
               
               
                   
                   
                 feeding pin1.0 
               
               
                   
                 D2 
                 The large diameter of the 
                 2.2 
               
               
                   
                   
                 feeding pin 
               
               
                   
                 D3 
                 Outer diameter of the 
                 5.2 
               
               
                   
                   
                 rotatable head (inside the 
               
               
                   
                   
                 housing) 
               
               
                   
                 S 
                 Air gap (isolation) between 
                 0.5 
               
               
                   
                   
                 the feeding pin and the 
               
               
                   
                   
                 rotatable head 
               
               
                   
                 Other 
                 Housing size 
                 90*55*11 
               
               
                   
                   
                 Length of the antenna arm 
                 40 
               
               
                   
                   
               
             
          
         
       
     
         [0032]    Besides devices with small dimensions, the antenna of the embodiment of the invention can be used in devices where the housing is in metal, for reasons of aesthetic, and thus inside which it is impossible to embed the antennas. Other applications may include multi-band LTE gateways, for which the external stick antennas can achieve better radiation patterns and performances in comparison with fully embedded antennas. 
         [0033]    While the present invention has been described in terms of a number of specific embodiments, it will be appreciated that modifications may be made which will fall within the scope of the invention. For example, various antenna lengths, mounting configurations and/or antenna driving circuits may be implemented separately or combined, and may be implemented in general purpose discrete components or dedicated data processing hardware.