Abstract:
A patch antenna may be integrated into a mobile terminal by associating the patch antenna with a ground plane adapted to remove eddy currents and isolate the antenna from spurious electromagnetic signals. The patch antenna may comprise a kink. Together the patch antenna and ground plane form a surface on which other electrical components may be mounted, such as the transceiver circuitry of the mobile terminal.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an antenna for use in a mobile terminal and specifically to a patch antenna structure that serves a dual purpose within the mobile terminal.  
         BACKGROUND OF THE INVENTION  
         [0002]    First there were pagers, then wireless phones, and more recently, personal digital assistants. Recent events have led to a convergence of these devices under the general appellation of a mobile terminal. Common to these devices in the latest generation is the ability to communicate wirelessly with a remote location.  
           [0003]    These mobile terminals are becoming ubiquitous throughout the world. While telecommunication standards may vary from country to country, the wireless revolution is in full swing. Mobile terminals can now be seen almost everywhere, and are becoming the pervasive computing devices envisioned.  
           [0004]    Since the initial car and bag phones were introduced, there has been constant pressure on the part of mobile terminal manufacturers to make the mobile terminals smaller. Keypads, batteries, and electrical components have all been reduced in size to make mobile terminals with smaller profiles.  
           [0005]    One area that historically has been resistant to changes in size is the antenna of the mobile terminal. This has been due to the need to isolate the antenna from other sensitive electronic components within the mobile terminal from cross talk and other electromagnetic compatibility issues. For example, positioning an antenna close to the electronic components may cause spurious emissions exceeding allowable FCC standards.  
           [0006]    A concurrent trend in the mobile terminal industry is to modularize components such that only a few modules contain all of the electrical components for the mobile terminal. Coupled with this modularization effort are efforts to integrate the electrical components into a single chip such that manufacturing costs are decreased.  
           [0007]    Heretofore, efforts to remove the traditional stub antenna and integrate an antenna into the body of the mobile terminal have failed.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention enables an antenna to be integrated within the body of a mobile terminal. Specifically, the present invention takes advantage of a ground plane structure that dissipates eddy currents and isolates a patch antenna from spurious electromagnetic signals. This structure then forms a substrate for other electrical components, such as those that comprise a transceiver front end for the mobile terminal.  
           [0009]    In one embodiment, the antennas include a kink to increase the electrical length thereof and to perform impedance matching.  
           [0010]    Those skilled in the art will appreciate the scope of the present invention and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0011]    The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the invention, and together with the description serve to explain the principles of the invention.  
         [0012]    [0012]FIG. 1 illustrates a schematic drawing of a mobile terminal such as may be used with the present invention;  
         [0013]    [0013]FIG. 2 illustrates a top plan view of an exemplary embodiment of the antenna of the present invention;  
         [0014]    [0014]FIG. 3 illustrates a cross-sectional side view of the embodiment of FIG. 2; and  
         [0015]    [0015]FIG. 4 illustrates a top plan view of a second embodiment of the antenna of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.  
         [0017]    The present invention is preferably incorporated in a mobile terminal  20 , such as a cellular telephone, personal digital assistant, or the like. The basic architecture of a mobile terminal  20  is represented in FIG. 1 and may include a receiver front end  22 , a radio frequency transmitter section  24 , an antenna  26 , a duplexer or switch  28 , a baseband processor  30 , a control system  32 , a frequency synthesizer  34 , and an interface  36 . The receiver front end  22  receives information bearing radio frequency signals from one or more remote transmitters provided by a base station. A low noise amplifier  38  amplifies the signal. A filter circuit  40  minimizes broadband interference in the received signal, while downconversion and digitization circuitry  42  downconverts the filtered, received signal to an intermediate or baseband frequency signal, which is then digitized into one or more digital streams. The receiver front end  22  typically uses one or more mixing frequencies generated by the frequency synthesizer  34 .  
         [0018]    The baseband processor  30  processes the digitized received signal to extract the information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding, and error correction operations. As such, the baseband processor  30  is generally implemented in one or more digital signal processors (DSPs).  
         [0019]    On the transmit side, the baseband processor  30  receives digitized data, which may represent voice, data, or control information, from the control system  32 , which it encodes for transmission. The encoded data is output to the radio frequency transmitter section  24 , where it is used by a modulator  44  to modulate a carrier signal that is at a desired transmit frequency. Power amplifier circuitry  46  amplifies the modulated carrier signal to a level appropriate for transmission from the antenna  26 .  
         [0020]    The amplified signal is sent to the switch  28  and antenna  26  through an impedance matching circuit  48 , which is configured to set the overall load impedance for the amplifier circuitry  46  to optimize values based on the type or speed of information being transmitted. Typically, the switch  28  and antenna  26  provide a relatively constant load impedance, which is combined with the impedance of the impedance matching circuit  48  to establish an overall load impedance for the amplifier circuitry  46 .  
         [0021]    Receiver front end  22 , the radio frequency transmitter section  24 , the frequency synthesizer  34 , the baseband processor  30 , and the control system  32  are sometimes referred to herein as the transceiver circuitry. Since the operation of this circuitry is well understood for those of ordinary skill in the art, any further discussion is omitted.  
         [0022]    A user may interact with the mobile terminal  20  via the interface  36 , which may include interface circuitry  52  associated with a microphone  54 , a speaker  56 , a keypad  58 , and a display  60 . The interface circuitry  52  typically includes analog-to-digital converters, digital-to-analog converters, amplifiers, and the like. Additionally, it may include a voice encoder/decoder, in which case it may communicate directly with the baseband processor  30 .  
         [0023]    The microphone  54  will typically convert audio input, such as the user&#39;s voice, into an electrical signal, which is then digitized and passed directly or indirectly to the baseband processor  30 . Audio information encoded in the received signal is recovered by the baseband processor  30 , and converted into an analog signal suitable for driving speaker  56  by the I/O and interface circuitry  52 . The keypad  58  and display  60  enable the user to interact with the mobile terminal  20 , such as inputting numbers to be dialed, address book information, or the like, as well as monitor call progress information.  
         [0024]    Other conventional circuitry may be integrated into the mobile terminal  20  as is well understood. For example, a global positioning satellite (GPS) receiver may be integrated into the mobile terminal  20 . A Bluetooth module may be integrated into the mobile terminal  20  along with other short-range communication circuits, such as an IR circuit. The mobile terminal  20  operates according to conventional telecommunications standards such as GSM, AMPS, D-AMPS, and other similar international telecommunications standards as needed or desired.  
         [0025]    [0025]FIG. 2 illustrates one embodiment of the present invention wherein the antenna  26  is seen positioned over a substrate structure  70 . In the embodiment shown, antenna  26  comprises a first radiating element  72  and a second radiating element  74 . First and second radiating elements  72 ,  74  may be used together for diversity reception and transmission, or the first radiating element  72  may be used for transmission and the second radiating element  74  may be used for reception. Greater or lesser numbers of radiating elements may be used as needed or desired.  
         [0026]    In the embodiment shown, the radiating elements  72 ,  74  each comprise a unshaped kink  76  and are positioned over a first ground plane  78 . The first ground plane  78  is comprised of two distinct levels of overlapping conductive plates  80 ,  82  (better seen in FIG. 3). For a full explanation of the first ground plane  78 , reference is made to U.S. Pat. No. 6,262,495, which is hereby incorporated by reference in its entirety. The overlapping conductive plates  80 ,  82  are arranged in two distinct levels reduce eddy currents within the first ground plane  78  and help provide directionality for the radiating elements  72 ,  74  as explained in the incorporated &#39;495 patent.  
         [0027]    The u-shaped kink  76  may be used to extend the electrical length of the radiating elements  72 ,  74 , thereby effectively tuning the antenna  26 . The kink  76  may also be used for impedance matching, or to provide dual band functionality for the antenna  26 . The kink  76  adds inductive loading to the radiating elements  72 ,  74  while also increasing the capacitive coupling between the radiating elements  72 ,  74  and the first ground plane  78 . Likewise, the kink  76  may be an electric short (i.e., the electromagnetic current on the radiating elements  72 ,  74  couples across the kink  76  rather than passing around the kink  76 ) at certain frequencies, thus creating a short antenna  26  at one frequency where the kink is shorted and a longer antenna  26  at other frequencies where the kink  76  is not bypassed. Geometries other than the kink  76  may be used as needed or desired.  
         [0028]    The substrate structure  70  is also illustrated in FIG. 3, wherein the layered relationship of the various components is better illustrated. Specifically, the substrate structure  70  comprises the antenna  26 , the first ground plane  78 , a second ground plane  84 , and an RF circuit element  86 . Distinct plies  88  of dielectric material  88 A,  88 B,  88 C, and  88 D separate the various electric components. In an exemplary component, the plies  88  are formed from FR4. Other dielectric materials may also be used, and material type may vary between plies  88  if needed or desired.  
         [0029]    The RF circuit element  86  may comprise as much of the transceiver circuitry as needed or desired. In an exemplary embodiment, the RF circuit element  86  comprises at least the duplexer  28 , and may also comprise the radio frequency transmitter section  24  and the receiver front end  22 . Still further, the frequency synthesizer  34  and baseband processor  30  may be considered an RF circuit element  86  for the purposes of the present invention. Preferably the RF circuit element  86  is printed or mounted on the ply  88 D using conventional integrated circuit printing technology, or is mounted thereon using conventional fabrication techniques.  
         [0030]    The antenna  26  may be electrically connected to the RF circuit element  86  using any appropriate electrical connections. In an exemplary embodiment, a through-hole via  90  is used to connect the antenna  26  to the RF circuit element  86 . Other via connectors may also be used so long as the electrical connection therebetween is not shorted by inadvertent contact with either the first ground plane  78  or the second ground plane  84 . The first ground plane  78  is electrically connected to the second ground plane  84  using via connectors  92  as is explained in the incorporated &#39;495 patent.  
         [0031]    The second ground plane  84  acts as a ground plane for any of the electronic components of the RF circuit element  86  as would be well understood. Thus, electrical connections may exist between RF circuit element  86  and the second ground plane  84  as needed or desired.  
         [0032]    The two distinct levels of overlapping conductive plates  80 ,  82  are illustrated in FIG. 2 as octagons. Please note that other polygonal and irregular shapes are contemplated. Specifically, triangles, hexagons, squares and circles are also acceptable plate shapes. The octagonal shapes illustrated do allow for spaces therebetween such that the through-hole via  90  may pass therethrough without intersecting either set of plates  80 ,  82 . If the through-hole via  90  does pass through a plate  80 ,  82 , clearances must be made so as to avoid a short circuit therebetween.  
         [0033]    Collectively, the substrate structure  70  is well-suited for incorporation into a mobile terminal  20  in that a single modular substrate structure  70  may have a footprint not much larger than one and one half inches squared (3.81 cm×3.81 cm). The size of the radiating elements  72 ,  74  may be varied according to the desired operating frequencies. This modular structure has the antenna  26 , a ground plane, and as much of the transceiver circuitry as desired for easy incorporation into a mobile terminal  20 .  
         [0034]    While substantially similar to the radiating elements  72 ,  74 , a second embodiment relies on inverted F radiating elements  72 A,  74 A as illustrated in FIG. 4. It should be appreciated that the placement of the radiating elements  72 A,  74 A relative to one another may be varied to provide for optimal matching and minimal cross-talk as needed or desired. For example, the radiating elements  72 A,  74 A might be rotated in the plane in which they lie so that the bars of the F both faced in, if desired. Other configurations are likewise within the scope of the present invention.  
         [0035]    Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present invention. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.