Patent Publication Number: US-2012044112-A1

Title: Local area network antenna for a mobile computing device

Description:
TECHNICAL FIELD 
     The invention relates generally to an integrated and isolated local area network (LAN) antenna for a mobile computing device. 
     BACKGROUND 
     Mobile computing devices generally include transceivers, such as local area network transceivers for communicating with a local area network (LAN). The transceiver is connected to a LAN antenna included inside the housing of the mobile device. Typical LAN antennas require a significant air gap between the electronic circuitry and the radiating element of the antenna. This air gap requirement limits design flexibility relating to the minimum dimensions with which the housing can be made. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments. 
       The above and further advantages of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. Skilled artisans will appreciate that reference designators shown herein in parenthesis indicate components shown in a figure other than the one in discussion. For example, talking about a device ( 10 ) while discussing Figure A would refer to an element,  10 , shown in figure other than Figure A. 
         FIG. 1  is a front view of a mobile computing device according to one embodiment of the invention. 
         FIG. 2  is a block diagram illustrating the electronic components of the mobile computing device of  FIG. 1 . 
         FIG. 3  illustrates a cross-sectional view of a LAN antenna according to one embodiment of the invention. 
         FIG. 4A  and  FIG. 4B  illustrate cross-sectional views of LAN antennas according to other embodiments of the invention 
         FIG. 5A  and  FIG. 5B  illustrate perspective views of mobile devices including LAN antennas according to the invention. 
         FIG. 6  is a graphical illustration of properties of an antenna of the present invention. 
     
    
    
     SUMMARY 
     In one aspect, the invention is embodied in an antenna for a mobile device. The antenna includes a housing formed from a metal material. The housing functions as a ground plane for the antenna and an RF shield for at least one electronic component of the mobile device. The antenna also includes an insulating material covering at least a portion of the housing and a radiating element disposed on the insulating material. 
     In one embodiment, the insulating material includes a dielectric material. The insulating material can also include a plastic material, a rubber material, an elastomer material, or a polymeric material. 
     One or more electrical components of the mobile device are grounded to the ground plane. The radiating element can be coupled to the radio of the mobile device. The antenna can also include a coaxial cable having a center conductor coupled to the radiating element and an outer shield coupled to the ground plane. 
     The radiating element can be oriented substantially parallel to the ground plane. In one embodiment, the antenna is an inverted-F antenna. In yet another embodiment, the antenna can be a patch antenna. 
     In another aspect, the invention is embodied in a method of forming an antenna for a mobile device. The method includes forming a housing of the mobile device from a metal material to function as a ground plane of the antenna and an RF shield for at least one electronic component of the mobile device. The insulating material can include a dielectric material. 
     The method can also include grounding one or more electrical components of the mobile device to the ground plane. In one embodiment, the radiating element is coupled to a radio of the mobile device. In one embodiment, a center conductor of a coaxial cable is coupled to the radiating element and an outer shield of a coaxial cable is coupled to the ground plane. The method can also include orienting the radiating element substantially parallel to the ground plane. 
     DETAILED DESCRIPTION 
     The following detailed description is merely illustrative in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any express or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. For the purposes of conciseness, many conventional techniques and principles related to conventional local area network (LAN) antennas, need not, and are not, described in detail herein. 
     Techniques and technologies may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or a component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. 
     The following description may refer to elements or nodes or features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element/node/feature is directly joined to (or directly communicates with) another element/node/feature, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. The term “exemplary” is used in the sense of “example, instance, or illustration” rather than “model,” or “deserving imitation.” 
     Technologies and concepts discussed herein relate to systems utilizing LAN antennas. In an exemplary embodiment, a LAN antenna is integrated into a housing of a mobile device. The housing functions as a ground plane for the antenna, as well as a radio-frequency (RF) shield for the electronic components of the mobile device. The invention is described with reference to a single band planar inverted-F antenna (PIFA). However, skilled artisans will appreciate that the techniques described herein can be extended to multi-band, including tri- and quad-band designs. 
     Because the housing functions as a ground plane for the antenna and an RF shield for at least one component of the mobile device, the properties of the antenna of the present invention are not affected by the internal electronic components of the mobile device. In contrast, in a typical antenna, a suitable air gap would be required between the internal electronics and the antenna to attempt to minimize the effects of these internal electronic components on the antenna performance. This air gap can affect the dimensions of the enclosure, thereby constraining the designer of the mobile device. No such air gap is required for the present invention. Additionally, the design of the antenna of the present invention can remain fixed even as internal components of the mobile device are modified or re-configured. For example, only a single antenna design is required to support a multitude of internal electronic configurations. 
       FIG. 1  is a front view of a mobile computing device  100  according to one embodiment of the invention. The mobile computing device  100  includes a housing  102 . The housing  102  contains electronic components, including internal communication components and circuitry as further described with relation to  FIG. 2  to enable the device  100  to communicate wirelessly with other devices. The housing  102  also contains I/O devices such as a keyboard  104  with alpha-numeric keys  106 , a display  108  (e.g., LED, OLED) that displays information about the device  100 , soft and/or hard keys, touch screen, jog wheel, a microphone  110 , and a speaker  112 . The mobile computing device  100  can also include a data capture device  114 , such as a laser scanner, imager, or radio-frequency identification (RFID) reader. In some embodiments, the device  100  includes less than all of the I/O devices shown in  FIG. 1 . 
       FIG. 2  is a block diagram  200  illustrating the electronic components of the mobile computing device  100  ( FIG. 1 ) according to the invention. The mobile computing device  100  contains, among other components, a processor  202 , a transceiver  204  including transmitter circuitry  206  and receiver circuitry  208 , an antenna  222 , the I/O devices  212  described in relation to  FIG. 1 , a program memory  214  for storing operating instructions that are executed by the processor  202 , a buffer memory  216 , one or more communication interfaces  218 , a data capture device  226 , such as a laser scanner, imager, or radio-frequency identification (RFID) reader, and an optional removable storage  220 . The mobile computing device  100  is preferably an integrated unit containing the elements depicted in  FIG. 2 , as well as any other element necessary for the mobile computing device  100  to function. In one embodiment, the electronic components are connected by a bus  224 . 
     The processor  202  can include one or more microprocessors, microcontrollers, DSPs, state machines, logic circuitry, or any other device or devices that process information based on operational or programming instructions. Such operational or programming instructions are preferably stored in the program memory  214 . The program memory  214  can be an IC memory chip containing any form of random access memory (RAM) or read only memory (ROM), a floppy disk, a compact disk (CD) ROM, a hard disk drive, a digital video disk (DVD), a flash memory card or any other medium for storing digital information. Skilled artisans will recognize that when the processor  202  has one or more of its functions performed by a state machine or logic circuitry, the program memory  214  containing the corresponding operational instructions may be embedded within the state machine or logic circuitry. Operations performed by the processor  202  as well as the mobile computing device  100  are described in detail below. 
     The transmitter circuitry  206  and the receiver circuitry  208  enable the mobile computing device  100  to respectively transmit and receive communication signals. In this regard, the transmitter circuitry  206  and the receiver circuitry  208  include circuitry to enable wireless transmissions. The implementations of the transmitter circuitry  206  and the receiver circuitry  208  depend on the implementation of the mobile computing device  100  and the devices with which it is to communicate. For example, the transmitter and receiver circuitry  206 ,  208  can be implemented as part of the communication device hardware and software architecture in accordance with known techniques. One of ordinary skill in the art will recognize that most, if not all, of the functions of the transmitter or receiver circuitry  206 ,  208  can be implemented in a processor, such as the processor  202 . However, the processor  202 , the transmitter circuitry  206 , and the receiver circuitry  208  have been partitioned herein to facilitate a better understanding of the functions of these elements. In one embodiment, the antenna  222  is a local area network (LAN) antenna coupled to the transceiver  204 . 
     The buffer memory  216  may be any form of volatile memory, such as RAM, and is used for temporarily storing received information. The removable memory  220  can be a secure digital (SD) memory card, for example. 
       FIG. 3  illustrates a PIFA antenna  300  for a mobile device according to one embodiment of the invention. The PIFA antenna  300  is generally arranged to include a single element radiator  302  formed adjacent to an insulating material  304 . By radiator, we mean the radiating element of the antenna  300 . The insulating material  304  can be a dielectric material. In one embodiment, the insulating material  304  is over-molded on a housing of the mobile device. 
     The single element radiator  302  can be substantially rectangular or any suitable shape. The radiator  302  can be solid or can include slots or other voids. 
     Voids can be formed in the radiator  302  to create resonances in the modal distribution at different frequencies of the antenna. An opening  306  in the insulating material  304  accommodates a shorting post  308 . In one embodiment, the shorting post  308  is integrated with the radiator  302 . 
     In one embodiment, the antenna  300  will generally resonate in a single band. For example, the antenna  300  can resonate in the frequency range of about 2.4 GHz to 2.5 GHz. However, skilled artisans will appreciate that various modifications to the radiator  302  can increase the number of resonance bands of the antenna  300 . 
     A ground plane  310  is generally formed from an electrically conductive material and is electrically opposed to the radiator  302 . For example, the ground plane  310  can be fabricated from a metal material. In one embodiment, the radiator  302  and the ground plane  310  are substantially parallel to each other. 
     The shorting post  308  shorts an end of the single element radiator  302  to the ground plane  310 . In one embodiment, the shorting post  308  is integrated with the ground plane  310 . Alternatively, the shorting post  308  is electrically connected to the radiator  302  and the ground plane  310 . 
     In one embodiment, the ground plane  310  functions as a radio-frequency RF shield for at least some of the electronic components of the mobile device (not shown). In this embodiment, the ground plane  310  substantially surrounds the electronic components. For example, the ground plane  310  can form the housing of the mobile device. 
     The resonant frequency of the antenna  300  is set by factors including the distance between the ground plane  310  and the radiator  302 , the material properties of the insulating material  304 , the length and width of the radiator  302 , and the relationship of these dimensions to a feed point  312 . For example, reducing the length of the radiator  302  tends to increase the frequency of the antenna&#39;s resonance, and increasing the length of the radiator  302  tends to decrease the frequency of the antenna&#39;s resonance. 
       FIGS. 4A and 4B  illustrate two possible implementations of an antenna  400 ,  400 ′ integrated with a housing  402  of a mobile device according to the invention. The housing  402  can include an enclosure  404  formed from a metal material. The enclosure  404  substantially surrounds at least some of the electronic components  406  of the mobile device that are susceptible to radio-frequency (RF) interference from the antenna  400 ,  400 ′or the external environment. Note that the size of the air gap between the electronic components  406  and the enclosure  404  is not critical. In fact, in one embodiment of the present invention, the distance between the electronic components  406  and the enclosure  404  can be substantially zero. 
     The enclosure  404  need not be completely sealed in order to provide adequate RF shielding. For example, the enclosure  404  may include one or more openings to accommodate a display, a keypad, other I/O components, a battery, or access to a removable memory. 
     An insulating material  408  can cover at least a portion of the enclosure  404 . For example, the insulating material  408  can be overmolded on the enclosure  404 . In one embodiment, the insulating material  408  is a dielectric material. Other suitable materials could also be used. The insulating material  408  forms the external “skin” over the housing  402 . For example, when a user holds the mobile device in a hand, the user&#39;s hand will contact the insulating material  408 . 
       FIG. 4A  illustrates a planar inverted-F (PIFA) antenna  400  according to one embodiment of the invention. A radiating element  410  can be formed from a single sheet of conductive material that is pressed into a suitable shape. The radiating element  410  is positioned on the insulating material  408 . Skilled artisans will appreciate that the antenna  400  can also be fabricated by a metal deposit, printing or plating over the insulating material  408 . In one embodiment, the radiating element  410  can include an integrated shorting post  412 . For example, the radiating element  410  and the shorting post  412  can be fabricated from a single piece of material. 
     The radiating element  410  is generally parallel to the ground plane  414 . The ground plane  414  is integrated with the enclosure  404 . For example, the ground plane  414  and the enclosure  404  can be embodied in the same physical component. In one embodiment, the shorting post  412  is generally perpendicular to the radiating element  410 . The shorting post  412  is connected to the ground plane  414 . 
     The antenna  400  also includes a feed  416 . The feed  416  emanates from a transceiver (not shown) of the mobile device. The feed  416  can be a coaxial feed  418  having a center conductor  420  and a shield  422  that surrounds the center conductor  420 . The center conductor  420  of the coaxial feed  418  extends through the insulating material  408  and is connected to the radiating element  410 . The shield  422  is connected to the ground plane  414 . 
       FIG. 4B  illustrates a patch-type antenna  400 ′ according to one embodiment of the invention. The patch-type antenna  400 ′ includes a radiating element  410 ′ as well as the ground plane  414 . The patch-type antenna  400 ′ does not require a shorting post. The center conductor  420  of the coaxial feed  418  extends through the insulating material  408  and is connected to the radiating element  410 ′. The shield  422  is connected to the ground plane  414 . 
       FIGS. 5A and 5B  illustrate perspective views of mobile devices  500 ,  500 ′ according to the invention. The mobile devices  500 ,  500 ′ each include a housing  502 ,  502 ′. Each of the mobile devices  500 ,  500 ′ includes a display  504 . An antenna  506  of  FIG. 5A  is positioned below the display  504  on the front surface  508  of the housing  502 . An antenna  506 ′ of  FIG. 5B  is positioned on a top surface  510  of the housing  502 ′. 
       FIG. 6  is a graphical illustration  600  of properties of the antenna of the present invention. Embodiments of antennas of the type shown in  FIGS. 5A and 5B  have been physically modeled and prototypes have been tested. Modeling indicates that the antenna exhibits a frequency resonance  602 . Dimensions for an exemplary prototype embodiment are approximately four inches tall by three inches wide by 1 inch deep. 
     The antennas  400 ,  400 ′ of  FIGS. 4A and 4B  are intended to be suitable for operation under the IEEE 802.11 wireless specification. According to the testing, the antenna  400  meets typical return loss bandwidth for the frequency band  604  in which it operates, namely between 2.4 GHz and 2.5 GHz. 
     The antenna is tuned, by the sizing methods described above or by adjusting the size of the radiating element, separation between the radiating element and ground plane(s), and/or feed/short locations. Skilled artisans will appreciate that an antenna according to the invention can include impedance matching circuitry (not shown). In one embodiment, the PIFA arrangement of the invention produces a high efficiency antenna that does not require a matching network because the impedance is large enough to render any impedance mismatch losses small across the entire operating band of the antenna. 
     In general, the processor  202  ( FIG. 2 ) of the mobile device  200  includes processing logic configured to carry out the functions, techniques, and processing tasks associated with the operation of the mobile device  200 . Furthermore, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by the processor  202 , or any combination thereof. Any such software may be implemented as low level instructions (assembly code, machine code, etc.) or as higher-level interpreted or compiled software code (e.g., C, C++, Objective-C, Java, Python, etc.). 
     In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued. 
     Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed. 
     It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors (or “processing devices”) such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and apparatus for the near-field wireless device pairing described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform the near-field wireless device pairing described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Both the state machine and ASIC are considered herein as a “processing device” for purposes of the foregoing discussion and claim language. 
     Moreover, an embodiment can be implemented as a computer-readable storage element or medium having computer readable code stored thereon for programming a computer (e.g., comprising a processing device) to perform a method as described and claimed herein. Examples of such computer-readable storage elements include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. 
     The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. 
     While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the example embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application. 
     In addition, the section headings included herein are intended to facilitate a review but are not intended to limit the scope of the present invention. Accordingly, the specification and drawings are to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims. 
     In interpreting the appended claims, it should be understood that: 
     a) the word “comprising” does not exclude the presence of other elements or acts than those listed in a given claim; 
     b) the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements; 
     c) any reference signs in the claims do not limit their scope; 
     d) several “means” may be represented by the same item or hardware or software implemented structure or function; 
     e) any of the disclosed elements may be comprised of hardware portions (e.g., including discrete and integrated electronic circuitry), software portions (e.g., computer programming), and any combination thereof; 
     f) hardware portions may be comprised of one or both of analog and digital portions; 
     g) any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise; and 
     h) no specific sequence of acts or steps is intended to be required unless specifically indicated.