Abstract:
A PIFA (Planar Inverted-F Antenna) array antenna has multiple PIFAs. The PIFA array is used to provide different radiation patterns for communication. A signal being emitted by the PIFA array is manipulated. According to the manipulation, the PIFA array may emit the signal with an omni-directional radiation pattern or a directional radiation pattern; the same PIFA array (antenna) is used for both directional communication and omni-directional communication. The PIFA array may be used in mobile computing devices, smart phones, or the like, allowing such devices to transmit directionally and omni-directionally. The signal manipulation may involve splitting the signal into components that feed PIFAs, and before the components reach the PIFAs, changing properties of the components (e.g., phase) relative to each other.

Description:
BACKGROUND 
       [0001]    In mobile devices, it is desirable to have antennas that are inexpensive yet efficient. While there have been many such antennas, previously, antennas with variable radiation patterns have not been widely used in mobile devices. Such antennas have not been used because it has not been considered feasible in terms of cost, scale, and gain. And, reasons to use such antennas have not previously been appreciated. 
         [0002]    Regarding technical feasibility, consider that for commercial devices it is preferred to use inexpensive antennas for communication. However, these antennas provide only one type of radiation pattern. For WiFi and Bluetooth protocols, the radiation pattern is omni-directional. Other protocols such as the NFC (Near Field Communication) protocol use inductive coupling to communicate, and point-to-point communications require directional antennas. To date, there have been no antennas with cost and size suitable for mobile devices that can function as both directional and omni-directional antennas. Patch antennas are often used in mobile devices. However, these antennas can be affected by the substrate on which they reside, and inexpensive substrates tend to lower antenna gain. 
         [0003]    Regarding desirability, there has not previously been appreciation of the possible uses of variant radiation pattern antennas in mobile devices. Because mobile devices are typically used in unpredictable or random orientations, directional radiation tends to be impractical; omni-directional radiation patterns allow for any device orientation. However, the present inventors have understood that mobile devices may be used in settings that are suitable for directional radiation patterns. For general-purpose mobile devices such as smart phones, cell phones, tablet-type computers, etc., directional communication may be desirable for security reasons; a directional link is difficult to intercept. Also, some uses may involve known orientations, allowing for a pre-determined radiation direction to be used. For instance, if a mobile device is near a terminal, for example a point-of-sale terminal or a proximity reader, a specific device orientation (and corresponding emission direction) can be easily accomplished by a person holding a device. For example, if a smart phone has directional capacity in a direction away from a back side of the smart phone, a person can point the back side of a smart phone toward a terminal when using the phone with the terminal. Even where security is not an issue, directional radiation, where possible, may help reduce power consumption. For example, sustained communication over a directional link might require less power than an omni-directional link. 
         [0004]    Techniques related to antennas with selectable radiation patterns are discussed below. 
       SUMMARY 
       [0005]    The following summary is included only to introduce some concepts discussed in the Detailed Description below. This summary is not comprehensive and is not intended to delineate the scope of the claimed subject matter, which is set forth by the claims presented at the end. 
         [0006]    A PIFA (Planar Inverted-F Antenna) array antenna has multiple PIFAs. The PIFA array is used to provide different radiation patterns for communication. A signal being emitted by the PIFA array is manipulated. According to the manipulation, the PIFA array may emit the signal with an omni-directional radiation pattern or a directional radiation pattern; the same PIFA array (antenna) is used for both directional communication and omni-directional communication. The PIFA array may be used in mobile computing devices, smart phones, or the like, allowing such devices to transmit directionally and omni-directionally. The signal manipulation may involve splitting the signal into components that feed PIFAs, and before the components reach the PIFAs, changing properties of the components (e.g., phase) relative to each other. 
         [0007]    Many of the attendant features will be explained below with reference to the following detailed description considered in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein like reference numerals are used to designate like parts in the accompanying description. 
           [0009]      FIG. 1  shows an example of a PIFA array. 
           [0010]      FIG. 2  shows feeder circuit on a substrate. 
           [0011]      FIG. 3  shows an overhead view of conductive a layer and separation areas. 
           [0012]      FIG. 4  shows a substrate with metallized openings. 
           [0013]      FIG. 5  shows an overhead view of PIFAs of the PIFA array. 
           [0014]      FIG. 6  shows a side view of the PIFA array. 
           [0015]      FIG. 7  shows another overhead view of the PIFA array. 
           [0016]      FIG. 8  shows phase adjusters feeding a source signal to contact pads. 
           [0017]      FIG. 9  shows a second antenna with an alternative arrangement of PIFAs. 
           [0018]      FIG. 10  shows a third antenna array. 
           [0019]      FIG. 11  shows a process performed by a device with a PIFA array. 
           [0020]      FIG. 12  shows an example omni-directional radiation pattern. 
           [0021]      FIG. 13  shows an example directional radiation pattern  280 . 
           [0022]      FIG. 14  shows an example of device. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    A variable radiation-pattern antenna, to be suitable for mobile devices or other small-scale applications, should preferably be inexpensive yet provide sufficient gain whether in a directional mode or an omni-directional mode. While patch antennas are often used in mobile devices they have limitations such as high dependency on the dielectric constant of their substrate. Inexpensive substrates with low dielectric constants tend to require large patches. In addition, patch antennas do not have the ability to vary between a directional radiation pattern and an omni-directional radiation pattern. Dipoles are omni-directional, and Yagi-Uda arrays or other antennas requiring reflectors are impractical for small-scale applications. 
         [0024]    Planar Inverted-F Antennas (PIFAs) have been used in many circumstances. While individual PIFA antennas can be compact, have efficient gain, may have a low profile, and are not overly dependent on a substrate, they nonetheless have not been used for providing both broadside (directional) communication and omni-directional communication. Nor have they been used in an array configuration. 
         [0025]      FIG. 1  shows an example of a PIFA array  100  that can provide directional and omni-directional radiation patterns for communication. The PIFA array  100  in  FIG. 1  will be used as an example to illustrate broad features of PIFA arrays described herein. Other examples of PIFA arrays will be discussed later. The PIFA array  100  has multiple PIFAs  102  in a radial arrangement. Each PIFA  102 , which resembles an inverted “F”, may have a shorting pin or shorting element  104 , a feed element  106  fed by a probe feed or the like (not shown), and a radiator or main element  108 . In other embodiments, parasitic elements may be included. The PIFA array  100  also has a substrate  110 , composed, for instance, of the FR-4 material (note that a variety of substrate materials can be used). A conductive layer  112  is aligned (co-planar) with the substrate  110 , and may be layered directly on the substrate  110  or on one or more intermediate layers of various composition. A feeder circuit  130  (shown in  FIG. 2  but not  FIG. 1 ) is layered directly or indirectly on the substrate  110 , opposite the PIFAs  102 . The feeder circuit  130  feeds a signal (or split components thereof) to the PIFA array  100 . 
         [0026]    The shorting elements  104  are each directly electrically connected with the conductive layer  112 . The feed elements  106  are isolated from the conductive layer  112  by separation areas  114 , which are simply areas surrounding the feed elements  106  where there is no conductive material. In other words, the feed elements  106  do not electrically contact the conductive layer  112 . The feed elements  106  pass through the substrate  110  to connect with the feeder circuit  130 . It is possible to have a layer between the PIFAs  102  and the conductive layer  112 , but it is not required for operation. An increase in mechanical stability might also result in reduced gain. 
         [0027]      FIG. 2  shows feeder circuit  130  on the substrate  110 . Contact pads  132  contact the feed elements  106 . Conductive paths  134 A,  134 B,  134 C,  134 D connect a signal input  136  with the feed elements  106 . The conductive paths  134 A,  134 B,  134 C,  134 D have varying path lengths to provide phase differences at the PIFAs  102 . The feeder circuit  130  in  FIG. 2  is for illustration only. In embodiments discussed later, a control circuit or other means adjusts phase differences according to whether directional or omni-directional communication is needed. 
         [0028]      FIG. 3  shows an overhead view of conductive layer  112  and separation areas  114 . The separation areas  114  may vary in number and location, according to the configuration and number of PIFAs in the PIFA array  100 . The separation areas  114  may be rectangular, irregular, or have any shape that provides sufficient separation between the conductive material of the conductive layer  112  and the feeder elements  106 . 
         [0029]      FIG. 4  shows the substrate  110  with metallized openings  150 . The feeder elements  106  pass through the openings  150  to connect with the feeder circuit  130 . The shape of the openings  150  is not significant and can vary. The openings  150  may be conductive vias that connect the ground plane or conductive layer  112  to the feeder circuit  130 . 
         [0030]      FIG. 5  shows an overhead view of the PIFAs  102 . In  FIG. 5 , for illustration, rectangles represent the shorting elements  104  and the feeder elements  106 . In actual implementations, the shorting elements  104  and feeder elements  106  may or may not have the overhead appearance as shown in  FIG. 5 .  FIG. 6  shows a side view of the PIFA array  100 . The layers in  FIG. 6  are intended to show relative arrangement, not scale. 
         [0031]      FIG. 7  shows another overhead view of the PIFA array  100 . Again, the shorting elements  104  contact the conductive layer  112 , and the feeder elements  106  contact the contact pads  132  of the feeder circuit  130 . Signal  136  flows from a source, through the feeder circuit  130  and contact pads  132  to the feeder elements  106 . Relative phases of the signal  136  (and perhaps lack of the signal  136 ) at the feeder elements  106  will vary according to whether the source is in a directional or omni-directional communication mode. 
         [0032]      FIG. 8  shows phase adjusters  180  feeding source signal  136  to contact pads  132 . The signal  136  may be split into component signals  178 . The signals shown in  FIG. 8  are only for illustration. In one embodiment, the phase adjusters or shifters  180  comprise circuitry between a source of the input signal  136  and the pads  132 . The phase adjusters  180  may be simple switches that that switch paths (of different length) between the source and the contact pads  132 . For example, a single contact pad  132  may have two electrical paths to the signal source. Each path is a different length. If a mobile device containing the PIFA array  100  is in an omni-directional mode, a switch (e.g., a logic element) may open a first path (e.g., short) and close a second path (e.g., long), and the switch may reverse the paths when in a directional mode. In another embodiment, the phase adjusters  180  may be phase shifter circuits between the signal source and the contact pads  132 , respectively. Any known technique for adjusting phase and/or other signal properties such as frequency, amplitude, etc., maybe used to create signal differences suitable for different communication modes. In other embodiments, a single phase adjuster  180  may supply two contact pads  132 . In the example of  FIG. 1  using four PIFAs  102 , each phase adjuster  180  would drive a pair of PIFAs  102 . Note that in  FIG. 8 , MODE 1  and MODE 2  are arbitrary; either MODE 1  or MODE 2  might be a directional mode, depending on particulars of the implementation. 
         [0033]      FIG. 9  shows a second antenna  200  with an alternative arrangement of PIFAs  102 . In this embodiment, three PIFAs  102  are used.  FIG. 10  shows a third antenna array  220 . In this example, the PIFAs  102  are arranged flat on a substrate or circuit board, again, with feeder circuit on an opposite side connecting to feeder parts of the PIFAs  102 . A ground plane may be sandwiched between substrate layers or surrounding the PIFAs  102  but only contacting at the ground elements of the PIFAs  102 . 
         [0034]      FIG. 11  shows a process performed by a device  238  with PIFA array  100 . The process involves the device  238  switching between communication modes with respective radiation patterns. The device  238  may be a cell phone, a smart card, an RF based digital credit card, a laptop, etc. At step  240 , the device  238  selects between a radiant (omni-directional) communication mode and a directional operation mode. For example, if the device  238  (perhaps an application running thereon) determines that the NFC protocol is to be used, the device  238  may switch to directional mode. If the device  238  determines at step  240  that WiFi or Bluetooth is currently needed, perhaps for another application, then it would switch to the omni-directional mode. At step  242 , the device adjusts the phases or other signal properties of the signals fed to each PIFA in accordance with the selected operational mode. In the directional mode, the PIFA array  100  may have a directional radiation pattern  144  with energy substantially in a directional range relative to the device  238 . In an omni-directional mode the PIFA array  100  may have an omni-directional radiation pattern  246  with energy substantially in all directions from the device  238 , although not usually with precise uniformity (see  FIGS. 12 and 13  for example radiation patterns). 
         [0035]    In one embodiment, the device  238  sustains one mode or the other to form corresponding types of communication links. In another embodiment, the device multiplexes the PIFA array  100  by rapidly switching between directional and omni-directional mode. In this way, the device can simultaneously communicate in both modes, albeit with reduced throughput rates. 
         [0036]      FIG. 12  shows an example omni-directional radiation pattern  270 . The nature of the radiation pattern for a PIFA array in omni-directional model will vary according to implementation. A uniform pattern is unlikely, but in general, the energy is distributed such that sufficient energy is available in most directions.  FIG. 13  shows an example directional radiation pattern  280  (the scale of  FIG. 13  is not necessarily the same as the scale in  FIG. 12 ). In this example, energy radiates primarily upward in the figure. The patterns in  FIGS. 12 and 13  are oriented relative to  FIG. 6 ; the plan of the array in  FIG. 6  would have the same orientation if shown in  FIGS. 12 and 13 . 
         [0037]      FIG. 14  shows an example of device  238 . The device has a display/input device  258 , a central processing unit (CPU)  260  and memory or storage  262 , operating together to execute an operating system  264 . Application and communication software  266  run within and/or as part of the operating system  264 . Various protocol implementations  266 ,  268  are running on the device  238 . When communication software or operating system  264  determine that directional (or omni-directional) communication is needed, a mode selector is signaled accordingly, thus shifting a variant antenna  272  (e.g., PIFA array  100 ) to a directional or omni-directional radiation pattern. The mode selector  270  may control phase adjusters  180 , for example, or may be considered the phase adjusters  180  as a group. 
         [0038]    In one embodiment, when an application is using a directional protocol implementation  266  (e.g., NFC or another directional protocol), the device, through mode selector  270 , selects the directional mode of the variant antenna  272 . When an application is using an omni-directional protocol implementation  268  (e.g., Bluetooth), the mode selector  270  puts the variant antenna  272  into the omni-directional mode. 
         [0039]    Regarding directional and omni-directional patterns, ring-type patterns are considered to be a type of omni-directional pattern. Other patterns that are considered to be omni-directional are bowl shaped patterns where, instead of having a traditional omni-directional radiation pattern that is parallel to a horizontal plane, the pattern is rotated 45 degrees upwards (between a horizontal and vertical plane) but is nonetheless circular within a horizontal plane. In addition, in some embodiments, turning one PIFA on can give a directional pattern that is shifted by some implementation-specific number of degrees. 
         [0040]    In conclusion, it should be noted that the PIFA arrays described above, and methods of using same, can be used in any type of device. Different PIFA configurations may be used. Phases of a signal at each PIFA (or other signal differences) may determine a radiation pattern of the PIFA array. A device or software thereon may communicate directionally or omni-directionally through the same PIFA array.