Abstract:
An antenna including a main span extending in a first direction, a first arm extending from the main span in a second direction substantially perpendicular to the first direction, a second arm extending from the main span in a third direction substantially opposite the second direction, a disc portion with a center substantially disposed at an intersection of the main span and the second arm, and a slot having a plurality of portions.

Description:
BACKGROUND  
       [0001]    The capabilities of mobile communications devices are consistently increasing. Typical modern devices of this type may include multiple transceivers and corresponding antennas for each of the transceivers. These antennas should be designed and oriented so as to optimize performance while minimizing interference among different antennas. 
       SUMMARY OF THE INVENTION  
       [0002]    The present invention is directed to an antenna including a main span extending in a first direction, a first arm extending from the main span in a second direction substantially perpendicular to the first direction, a second arm extending from the main span in a third direction substantially opposite the second direction, a disc portion with a center substantially disposed at an intersection of the main span and the second arm, and a slot having a plurality of portions. 
         [0003]    The present invention is further directed to a device including a first wireless transceiver and a first antenna coupled to the first wireless transceiver. The first antenna includes a main span extending in a first direction, a first arm extending from the main span in a second direction substantially perpendicular to the first direction, a second arm extending from the main span in a third direction substantially opposite the second direction, a disc portion with a center substantially disposed at an intersection of the main span and the second arm, and a slot having a plurality of portions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0004]      FIG. 1  shows a partial view of an exemplary mobile communication device according to the present invention. 
           [0005]      FIG. 2  shows an exemplary antenna with a slot meander according to the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0006]    The exemplary embodiments of the present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments describe antenna arrangements that reduce interference and improve isolation of antennas located in close physical proximity to one another while operating in different frequency bands. 
         [0007]    Modern mobile communication devices may typically include multiple transceivers. Each such transceiver may be used in conjunction with a different communications protocol (e.g., cellular, WiFi, Bluetooth, etc.), and may be used for varying tasks or types of communication. For example, one transceiver may be used for voice communications while another may be used for data communications; alternately, one transceiver may be used for short-range data communications while another may be used for long-range data communications; those of skill in the art will understand that these divisions of labor are only exemplary and that various others are possible. 
         [0008]    Such transceivers may share some system resources with one another. For example, they may be located on the same printed circuit board, may draw power from the same source (e.g., a battery, line power, etc.), may receive instructions from the same processor, etc. However, because of the varying needs of transceivers engaged in different types of communications, each transceiver may typically require its own antenna designed to specifications appropriate to the transceiver. When designing devices with multiple transceivers and multiple corresponding antennas, one important design concern is to maximize the isolation between the antennas, and thus minimize signal interference and improve the performance of the corresponding transceivers. 
         [0009]    One common class of mobile devices includes a first transceiver for cellular communications and a second transceiver for WiFi (e.g., 802.11 a/b/g/n) communications. In the design of such devices, it is desirable for the two transceivers to be able to operate simultaneously without interference. This presents a significant challenge, especially in light of the fact that such devices must place antennas, as well as all other required components, in a limited amount of space. While many antenna designs are known in the art (e.g., inverted L-antenna, inverted F-antenna, monopole disc antenna, J-antenna, etc.) and may provide good signal radiation, use of existing antenna designs in conjunction in a single device with multiple transceivers typically results in unsatisfactory levels of isolation. 
         [0010]    Various techniques exist to improve the isolation performance of antennas located in close physical proximity to one another. In one example, a weight-tapered inverted-L (“IL”) antenna with a disc-shaped portion, typically used for cellular communications, may be used in conjunction with a dual band inverted F-antenna, typically used for WiFi communications. The antennas may be placed perpendicular to one another in order to minimize interference. In key frequency ranges, this antenna selection and arrangement may yield an isolation of −20 dB. However, in order to suppress noise floor jamming that may be generated by WiFi signals, an isolation of at least −30 dB is desirable. 
         [0011]    The exemplary embodiment addresses this deficiency by providing a suitable level of isolation.  FIG. 1  illustrates an exemplary device  100  according to the present invention. The device  100  is shown with part of the casing  110  removed in order to illustrate internal components. The device  100  includes a first antenna  120  and a second antenna  130 . The first antenna  120  may be a dual-band inverted F-antenna as described above, and may be used to send and receive signals by a first transceiver (e.g., a WiFi transceiver, etc.), not shown. 
         [0012]    The second antenna  130  may be oriented perpendicular to the first antenna  120  (e.g., as illustrated in  FIG. 1 , the main portion of the first antenna  120  is oriented horizontally, while the main portion of the second antenna  130  is oriented vertically) in order to take advantage of the benefits of such an orientation as described above. The first antenna  120  and the second antenna  130  may share the same ground plane.  FIG. 2  shows the second antenna  130  in more detail. As can be seen, the basic profile of the second antenna  130  is similar to a weight-tapered IL antenna with a disc-shaped portion. The second antenna  130  includes a main span  131 , a first arm  132 , a second arm  133 , a disc  134  and a first slot  135 . In this exemplary embodiment, the second antenna  130  may be 91 mm in width and 143 mm in length, and that the first slot  135  may be 2.5 mm in width and 19 mm in length, though those of skill in the art will understand that the precise dimensions may vary in other embodiments. 
         [0013]    The second antenna  130  further includes a second slot  140 , also referred to as a “slot meander,” which may be 2 mm in width. The second slot  140  includes a first portion  141  that extends along the main span  131  and may be 30.5 mm in length; a second portion  142  that extends toward the first arm  132  and may be 6 mm in length; a third portion  143  that extends in the same direction as the first portion  141  and may be 8 mm in length; a fourth portion  144  that extends toward the second arm  133  and may be 10 mm in length; a fifth portion  145  that extends in the same direction as the first portion  141  and the third portion  143  and may be 6 mm in length; and a sixth portion  146  that extends in the same direction as the second portion  142  and may be 7.9 mm in length. The corners of the second slot  140  where the portions intersect may be plain intersections, diagonally chamfered (e.g., at a 45 degree angle), curved, etc. As stated above, those of skill in the art will understand that the dimensions of the second slot  140  and its portions  141 - 146  provided above are intended to be both approximate and exemplary and that other embodiments may be of varying size and orientation. 
         [0014]    The performance achieved by the second antenna  130  may be comparable to that of a standard weight-tapered IL antenna with a disc-shaped portion. The second antenna  130  may have an omni-directional radiation pattern and may have an efficiency of at least 70% in cellular bands (e.g., AMPS, GSM, DCS, PCS, UMTS, etc.). The first antenna  120  may have an efficiency of at least 85% in WiFi bands. The second antenna  130  may also achieve a bandwidth of 23% in high frequency bands, an improvement over standard monopole/dipole antennas, which typically achieve a bandwidth of 5% to 12%. This improvement may be achieved due to the tapered shape of arms  132  and  133 , which may be sized to match the frequency of the signals that they receive. 
         [0015]    Additionally, for signals in the frequency band from 2.11 GHz to 2.17 GHz (e.g., the UMTS band), the second antenna  130  with the slot meander may achieve an isolation of −30 dB, an improvement of 10 dB over prior implementations described above. Further optimizations, such as using the housing  110  of the device  100  for capacitance, may achieve further gains in isolation, on the order of −34 to −40 dB in the same frequency band as described above. 
         [0016]    It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. For example, the principles described may be applied to antennas adapted to send and receive signals in various frequency bands and for various purposes. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.