Abstract:
Methods and systems to implement planar antennas and bandwidth extension apertures, including planar antennas etched in metal clad printed circuit board materials, relatively small-scale planar antennas having dimensions in a range of centimeters and/or millimeters, planar antennas to operate in GHz frequency ranges, and bandwidth extension apertures to alter an antenna impedance, reduce an antenna return loss, reduce an antenna Q factor, and/or increase an antenna frequency bandwidth.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    Methods and systems disclosed herein are directed to planar antennas and bandwidth extension apertures. 
         [0003]    2. Background 
         [0004]    In radio technology, bandwidth refers to frequency range, typically measured in Hertz (Hz). A devices may be characterized by a bandwidth within which the device meets one or more criteria. In some applications, such as ultra wideband (UWB) applications, broader antenna bandwidth operation is desired. 
         [0005]    UWB systems typically transmit relatively low energy levels over a relatively broad frequency range or spectrum. UWB systems may be used for relatively short-range high-bandwidth communications without interfering with more traditional narrow bandwidth continuous carrier wave systems that operate within a bandwidth of a UWB system. 
         [0006]    Conventional UWB antennas include relatively large printed monopole antennas, stand alone monopole antennas that are mechanically complex, and relatively expensive ceramic chip monopole antennas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0007]      FIG. 1  is a perspective view of an exemplary antenna system  100 . 
           [0008]      FIG. 2  is a plot  200  illustrating a simulated scattering parameter magnitude, or S-parameter of antenna system  100 . 
           [0009]      FIG. 3  is a perspective view of an exemplary antenna system  300 , including an exemplary bandwidth extension aperture  302 . 
           [0010]      FIG. 4  is a plot  400  illustrating an S-parameter magnitude of antenna system  300 . 
           [0011]      FIG. 5  is a process flowchart illustrating an exemplary method of identifying an area of a planar antenna for a bandwidth extension aperture. 
       
    
    
       [0012]    In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears. 
       DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a perspective view of an exemplary antenna system  100 , including a substrate  102  having a surface  104 . 
         [0014]    Substrate  102  may be a substantially planar dielectric substrate, such as a printed circuit board substrate, which may be a fire retardant dielectric material commonly known to as Flame Retardant  4 , or FR 4 , available from a variety of manufactures. FR 4  materials may be defined as materials that satisfy an Underwriters Laboratories standard UL 94 -V 0 , and variations thereof. Substrate  102  may have a thickness of approximately 1 millimeter. Substrate  102  may be a substantially rigid dielectric substrate or a relatively flexible dielectric substrate to conform to a space. 
         [0015]    A metal layer is disposed over one or portions of surface  104 . The metal layer may include copper. For illustrative purposes, substrate  102  is illustrated as including a radiate portion  106  and a ground plane portion  108 . Radiate portion  106  includes a metal layer  110  to radiate within a bandwidth. Ground plane portion  108  includes a metal layer  112 . Alternatively, or additionally, ground plane portion  108  may include a metal layer disposed over an opposing surface  114  of substrate  102 . 
         [0016]    Portions of surface  104  that do not include a metal layer disposed thereon are referred to herein as non-metallized portions. 
         [0017]    Metal layer  110  and/or metal layer  112  may be implemented in one or more of a variety of patterns and dimensions to provide one or more characteristics, such as a center frequency, a frequency bandwidth, and/or a radiation beam pattern. For example, and without limitation, antenna system  100  may be configured to radiate within a bandwidth centered about a center frequency, which may be approximately 7 GHz. 
         [0018]    Patterns may be etched from an initial metal layer disposed over all or substantially all of surface  104 , to expose non-metallized portions of surface  104 , and to retain metal layers 110 and 112. Patterns may be etched according to one or more of a variety of conventional printed circuit board etching techniques. 
         [0019]    Antenna system  100  may be implemented with a relatively small physical profile, and may be implemented as part of a mobile wireless communication device. For example, and without limitation, a width w of radiate portion  106  may be approximately equal to or less than 2 centimeters. A height h of radiate portion  106  may be approximately equal to or less than 1 centimeter, and may be approximately equal to or less than 8 millimeters. 
         [0020]    Antenna system  100  may be coupled to another device  118  at or near ground plane portion  108 . Radiate portion  106  may extend beyond device  118  by height h. Device  118  may be a ground plane of a portable communications device, such as a ground plane of a display. a height h g  of ground plane portion  108  may be approximately equal to or less than 1 centimeter. 
         [0021]    Metal layer  110  may be electrically coupled to a receiver, transmitter, or transceiver through a coupling system  116 , which may include one or more of a variety of conventional electrical-to-planar antenna coupling systems, scaled to dimensions of antenna system  100 . Coupling system  116  may include a connector, such as a coaxial connector. 
         [0022]      FIG. 2  is a plot  200  illustrating a computer simulated scattering parameter magnitude, or S-parameter  202  of antenna  100  system, wherein antenna system  100  is configured to radiate within a bandwidth centered approximately at 7 GHz. 
         [0023]    S-parameters are indicative of impedance mismatch between antenna system and a coupling system, and indicative of a corresponding return loss and quality, or Q factor of an antenna system. Higher S-parameter values and impedance mismatches lead to higher return loses and higher Q factors, which correspond to narrower bandwidths. Lower S-parameter values and impedance mismatches correspond to greater energy passed to antenna system  100 . S-parameters, impedances, return losses, and Q factors are well known to those skilled in the art. 
         [0024]    In matrix notation, as is common in S-parameter evaluation, plot  200  corresponds to an S 1 , 1  input of antenna system  100 , at coupling system  116 . Plot  200  illustrates an approximately 90% efficiency, or −10 dB return loss, for a 1.7 GHz bandwidth between 4.2 GHz and 5.9 GHz, and for a relatively narrow bandwidth between 8.1 GHz and 8.5 GHz. 
         [0025]    Dielectric properties of a dielectric substrate-based antenna system affect the impedance of the antenna system. Accordingly, a planar, dielectric substrate-based antenna may include one or more apertures through the substrate to improve impedance matching, reduce return loss, and/or reduce Q factor, and thus increase bandwidth. The one or more apertures may be sized to substantially preclude the aperture from radiating within a frequency bandwidth of the antenna. 
         [0026]    Aperture position, shape, and/or dimensions may be selected and/or determined based on knowledge, experience, experimentation, simulation, and/or measurement of one or more features and/or responses to stimulation. For example, an electric field generated by a dielectric substrate-based antenna is affected by dielectric properties of the substrate. To optimize effects of an aperture, the aperture position may be selected to correspond to an area of relatively high electric field intensity. An exemplary method of identifying an area for a bandwidth extension aperture is disclosed below with respect to  FIG. 5 . 
         [0027]    In a monopole antenna system, such as antenna system  100  in  FIG. 1 , electric fields tend to be relatively more intense between radiate portion  106  and ground plane portion  108 . Accordingly,  FIG. 3  is a perspective view of an exemplary antenna system  300 , including features described above with respect to antenna system  100 , and including an exemplary bandwidth extension aperture  302  through surface  104 , between radiate portion  106  and ground plane portion  108 . Aperture  302  is configured to reduce an impedance mismatch between antenna system  300  and coupling system  116 . Aperture  302  may be configured to substantially preclude aperture  302  from radiating within a bandwidth of antenna system  300 . Antenna system  300  may be dimensioned as described above with respect to antenna system  100 . 
         [0028]    In the example of  FIG. 3 , aperture  302  has an elongated, substantially rectangular shape, referred to herein as a slot. A width w A  of aperture  302  is less than width w of radiate portion  106 . Aperture width WA may be less than approximately 2 centimeters, and may be approximately 1 centimeter. A height h A  of aperture  302  may be less than approximately 2 millimeters, and may be approximately 1 millimeter, and may be less than 1 millimeter. 
         [0029]      FIG. 4  is a plot  400  illustrating a computer simulated S-parameter magnitude  402  for antenna system  300 , wherein antenna system  300  is configured to radiate within a bandwidth centered approximately at 7 GHz. Plot  400  corresponds to an S 1 , 1  input of antenna system  300 , at coupling system  116 . 
         [0030]    Plot  400  illustrates an approximately 90% efficiency, or −10 dB return loss, for a 5.9 GHz bandwidth between 3.9 GHz and 9.8 GHz. Aperture  302  thus increases the 1.7 GHz bandwidth of antenna system  100  to 5.9 GHz. 
         [0031]    Mathematical analyses of antenna system  300 , configured to radiate within a bandwidth centered approximately at 7 GHz, indicate that aperture  302  does not substantially radiate below a frequency in a range of approximately 13 GHz to 15 GHz. Computer simulation indicates that aperture  302  does not substantially radiate below approximately 20 GHz. Aperture  302  may thus improve bandwidth without substantially altering a radiation pattern of a planar antenna system. 
         [0032]      FIG. 5  is a process flowchart illustrating an exemplary method  500  of identifying an area of a planar antenna for a bandwidth extension aperture. 
         [0033]    At  502 , a relatively high intensity portion of an antenna electric field is identified. The relatively high intensity portion of the electric field may be identified based on knowledge, experience, experimentation, simulation, and/or measurement of one or more features and/or responses to stimulation. 
         [0034]    At  504 , an area of the planar antenna corresponding to the relatively high intensity portion of the electric field is identified. The area may be identified from a non-metallized portion of a substrate of the antenna to avoid altering radiation parameters of the antenna. Alternatively, the area may include a metallized portion of the substrate, in which case the metallized substrate may be reconfigured to retain or achieve desired radiation parameters. 
         [0035]    At  506 , an aperture is cut, drilled, or otherwise formed through the identified area. As noted above, aperture position, shape, and/or other dimensions may be selected and/or determined based on knowledge, experience, experimentation, simulation, and/or measurement of one or more features and/or responses to stimulation. 
         [0036]    While various embodiments are disclosed herein, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure. Thus, the breadth and scope of the claims should not be limited by any of the exemplary embodiments disclosed herein.