Abstract:
An antenna that is capable of accommodating both IEEE 802.11b/g traffic and IEEE 802.11n traffic is provided. The antenna includes a ground plane member, a plurality of inverted F slot antenna elements disposed at equidistant positions along a periphery of the ground plane member, and a plurality of slot elements disposed at equidistant positions along the periphery of the ground plane member is provided. First and second slot elements can be disposed on respective first and second sides of each inverted F slot antenna element, and each inverted F slot antenna element can operate in a first frequency band and in a second frequency band.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/419,113 filed Dec. 2, 2010 and titled “IFS Beamforming Antenna for IEEE 801.11n MIMO Application.” U.S. Application No. 61/419,113 is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present invention relates generally to antennas. More particularly, the present invention relates to an IFS beamforming antenna for IEEE 802.11n MIMO applications. 
       BACKGROUND 
       [0003]    IEEE 802.11n-2009 is an amendment to the IEEE 802.11-2007 wireless network standard. IEEE 802.11n improves network throughput over two previous standards, IEEE 802.11a and 802.11g, in at least two ways. First, IEEE 802.11n operates with a 2.4 GHz/5 GHz duel frequency band. Second, IEEE 802.11n significantly increases the maximum raw data rate from 54 Mbit/sec to 600 Mbit/sec. 
         [0004]    While many aspects of IEEE 802.11n are advantageous, IEEE 802.11n may be impractical for many users because there is a need to support legacy equipment that is compatible with only 802.11b/g. Therefore, until hardware that is compatible with 802.11n becomes more prevalent, it would be desirable to operate a mixed 802.11b/g/n network. In such a mixed-mode network, it would be desirable for a dual-radio access point to be employed such that 802.11b/g traffic is placed on a 2.4 GHz radio band and 802.11n traffic is placed on a 5 GHz radio band. 
         [0005]    To implement the above-described mixed-mode network and dual-radio access point, there is a need for a 2.4 GHz/5 GHz dual frequency band multiple input and multiple output (MIMO) antenna. One known solution is to use several omni-directional external whip antennas for the 802.11n access point in a diversity scheme. This solution has been used for 2×2 and 3×3 MIMO applications. However, for MIMO applications with an increased number of inputs and outputs, the interference between the whip antennas is serious and the cosmetic appearance of the access point is unattractive. 
         [0006]    Therefore, another known solution is to embed a single 2.4 GHz band antenna or a single 5 GHz band antenna inside of a radome. To operate in a dual frequency band, the two bands can be combined together with an RF switch. However, this solution doubles of the number of required antennas. 
         [0007]    For example, in a 10×10 MIMO application, this solution requires the need to integrate ten antennas operating at 2.4 GHz and ten antennas operating at 5 GHz. This integration must occur in a small package size, which causes a large amount of interference. To minimize the interference, a diode, capacitive loading element, or an open stub can be added. However, these additional elements add cost to the access point and increase the production complexity. 
         [0008]    In view of the above, an improved dual-radio access point that accommodates 802.11b/g traffic and 802.11n traffic is desired. Preferably, such an access point minimizes interference and the number of antennas employed while still being cosmetically attractive. 
       SUMMARY 
       [0009]    According to some embodiments, an antenna is provided. The antenna can include a ground plane member, a plurality of inverted F slot antenna elements disposed at equidistant positions along a periphery of the ground plane member, and a plurality of slot elements disposed at equidistant positions along the periphery of the ground plane member. First and second slot elements can be disposed on respective first and second sides of each inverted F slot antenna element, and each inverted F slot antenna element can operate in a first frequency band and in a second frequency band. 
         [0010]    In some embodiments, each inverted F slot antenna element can include an aperture, and each inverted F slot antenna element aperture can include a first arm, a second arm, a shorting elbow, and a notch. The first arm can be substantially parallel to the second arm, the shorting elbow can be substantially perpendicular to the first arm and the second arm, and the shorting elbow can connect the first arm to the second arm by being integrally contiguous with the first arm and the second arm. A length of the first arm can be longer than a length of the second arm, and the notch can be disposed along the length of the first arm. 
         [0011]    The antenna according to disclosed embodiments can be capable of accommodating IEEE 802.11b/g traffic as well as IEEE 802.11n traffic. In some embodiments, the antenna can operate in both a 2.4 GHz frequency band and in a 5 GHz frequency band. The plurality of slot elements can be capable of substantially reducing or eliminating interference between each of the inverted F slot antenna elements. Accordingly, high isolation can be achieved. 
         [0012]    A MIMO beamforming antenna is also provided. The MIMO beamforming antenna can include a plurality of inverted F slot antenna elements such that each element can radiate in a 2.4 GHz frequency band and in a 5 GHz frequency band. 
         [0013]    According to some embodiments, an IEEE 802.11n access point is also provided. The IEEE 802.11n access point can include a MIMO antenna, which can include a plurality of inverted F slot antenna elements such that each element can radiate in a 2.4 GHz frequency band and in a 5 GHz frequency band. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic view of a MIMO antenna; 
           [0015]      FIG. 1A  is an enlarged view of an exemplary IFS antenna element of the MIMO antenna of  FIG. 1 ; and 
           [0016]      FIG. 2  is a schematic view of the MIMO antenna of  FIG. 1  showing the dimensions of one IFS antenna element thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    While this invention is susceptible of an embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention. It is not intended to limit the invention to the specific illustrated embodiments. 
         [0018]    Various embodiments are described that include an improved dual-radio access point that accommodates 802.11b/g traffic and 802.11n traffic. In accordance with some embodiments, such an access point minimizes interference and the number of antennas employed while still being cosmetically attractive. 
         [0019]    For example, an access point in accordance with some embodiments can include a 2.4 GHz/5 GHz dual frequency band multiple input and multiple output (MIMO) antenna with a plurality of inverted F slot (IFS) beamforming antennas. Each IFS antenna element can radiate in the 2.4 GHz frequency band and in the 5.0 GHz frequency band. In some embodiments, each antenna element can radiate as a directional antenna in a horizontal direction. 
         [0020]    The MIMO antenna shown and described herein can be manufactured by a piece of stamping sheet metal or printed circuit board (PCB) material. Therefore, the MIMO antenna in accordance with disclosed embodiments can be manufactured in a more cost effective manner as compared to PCB antennas and other three-dimensional forming antennas. 
         [0021]      FIG. 1  and  FIG. 2  are schematic views of an exemplary MIMO antenna  10 .  FIG. 2  shows the dimensions of one IFS antenna element in the MIMO antenna  10 . However, it is to be understood that the dimensions shown in  FIG. 2  are only exemplary and could vary as would be known by those of skill in the art. 
         [0022]    The MIMO antenna  10  shown in  FIG. 1  and  FIG. 2  is a 9×9 application including nine IFS antenna elements and nine slot elements. However, it is to be understood that a MIMO antenna in accordance with embodiments disclosed herein is not so limited.  FIG. 1  and  FIG. 2  are merely exemplary, and the MIMO antenna can include any number of IFS beamforming antennas and slot elements. For example, a MIMO antenna in accordance with disclosed embodiments could be a 4×4 antenna, a 12×12 antenna, or any other size antenna as would be known and desired by those of skill in the art. 
         [0023]    As seen in  FIG. 1 , a MIMO antenna  10  in accordance with some embodiments can include a unitary ground plane member  100  that can be, for example, circular, ovular, oblong, rectangular, or any other shape as would be known and desired by those of skills in the art. The member  100  shown in  FIG. 1  is circular, but embodiments disclosed herein are not so limited. 
         [0024]    A plurality of IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  and a plurality of slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  can be disposed in and/or on the ground plane member  100  in a co-planar manner. For example, as seen in  FIG. 1 , the plurality of IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  can be disposed in an equidistant manner along a periphery  110  of the ground plane member  100 . The plurality of slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  can also be disposed in an equidistant manner along the periphery  100  of the member  100 . 
         [0025]    In some embodiments, the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  and the slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  can alternate. Thus, a first slot element, for example,  300 - 1 , can be disposed on a first side of an IFS antenna element, for example,  200 - 1 , and a second slot element, for example,  300 - 9 , can be disposed on a second side of the IFS antenna element  200 - 1 . Each IFS antenna element  200 - n  can a slot element  300 - n  on first and second sides thereof. 
         [0026]    The number of IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  can be equal to the number slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9 . For example, the MIMO antenna  10  shown in  FIG. 1  includes nine IFS antenna elements and nine slot elements. 
         [0027]    As seen in  FIG. 1A , Each IFS antenna element  200 - n  can include a cut-out or aperture disposed in the ground plane member  100 . The aperture can include a first arm  210 , a second arm  220 , and a shorting elbow  230 . The first arm  210 , the second arm  220 , and the shorting elbow  230  can be contiguous with one another to form one single, contiguous cut-out or aperture. 
         [0028]    For each IFS antenna element  200 - n , the first arm  210  can extend from the periphery  110  of the ground plane member  100  towards the center C of the member  100 . Thus, a first end  212  of the first arm  210  can be at the periphery  110  of the ground plane member  100 , and a second end  214  of the first arm  210  can be at a position on the ground plane member  100  away from the periphery  110 . 
         [0029]    The first arm  210  can have a length L 1  and include a notch  215  along the length L 1  thereof. For example, the notch  215  can include a portion of the ground plane member  100  protruding into the cut-out or aperture of the first arm  210 . In some embodiments, the notch  215  can be at an approximately half-way point along the length L 1  of the first arm  210 . 
         [0030]    In some embodiments, the length L 1  of the first arm  210  can be between approximately 1.5 and 1.6 inches, for example, as seen in  FIG. 2 , approximately 1.56 inches. In some embodiments, the length of the notch  215  can be between approximately 0.1 and 0.2 inches, for example, as seen in  FIG. 2 , approximately 0.157 inches. Thus, in some embodiments, the length of the notch  215  can be approximately 10% of the length of the length L 1  of the first arm  210 . 
         [0031]    In some embodiments, the width W 1  of the first arm  210  can be between approximately 0.1 and 0.2 inches, for example, as seen in  FIG. 2 , approximately 0.197 inches. 
         [0032]    The shorting elbow  230  can be substantially perpendicular to the first arm  210  and be integrally contiguous with a second end  214  of the first arm  210 . The shorting elbow  230  can also be substantially perpendicular with the second arm  220  and be integrally contiguous with a second end  224  of the second arm  220 . Thus, the shorting elbow  230  can connect the first arm  210  and the second arm  220 . 
         [0033]    The shorting elbow  230  can have a length L 2 . In some embodiments, the length L 2  of the shorting elbow  230  can be between approximately 0.5 and 0.6 inches, for example, as seen in  FIG. 2 , approximately 0.591 inches. 
         [0034]    In some embodiments, the notch  215  can have width. A first portion of the width of the notch  215  can extend into the aperture of the IFS antenna element  200 - n , and a second portion of the width of the notch  215  can extend into or onto the ground plane member  100 , outside of the aperture. In some embodiments, the length L 2  of the shorting elbow  230  plus the width of the second portion of the notch  215  can be between approximately 0.4 and 0.5 inches, for example, as seen in  FIG. 2 , approximately 0.472 inches. 
         [0035]    The second arm  220  can be substantially parallel to the first arm  210 . Additionally, the second arm  220  can have a length L 3 , and in some embodiments, the length L 3  of the second arm  220  can be smaller than the length L 1  of the first arm  210 . For example, in some embodiments, the length L 3  of the second arm  220  can be between approximately 0.3 and 0.4 inches, for example, as seen in  FIG. 2 , approximately 0.354 inches. Thus, in some embodiments, the length L 3  can be between approximately 20% and 25% of the length L 1 . In still further embodiments, the length L 3  can be approximately 22% of the length L 1 . 
         [0036]    A first end  222  of the second arm  224  can be at a position on the ground plane member  100  away from the periphery  110 , and a second end  224  of the second arm  220  can also be at a position on the ground plane member  100  away from the periphery  110 . The first end  222  of the second arm  220  can be closer to the periphery  110  than the second end  224  of the second arm  220 . That is, the second end  224  of the second arm can be closer to the center C of the ground plane member  100  than the first end  222  of the second arm  220 . 
         [0037]    Each slot element  300 - n  can include a cut-out or aperture disposed in the ground plane member  100 . The aperture can be linear and have a length L 4 . In some embodiments the length L 4  of a slot element  300 - n  can be longer than the length L 1  of the first arm  210  of an IFS antenna element  200 - n.    
         [0038]    In some embodiments, the slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  disposed between the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  can improve the radiation pattern of the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9 . In some embodiments, the slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  disposed between the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9  can also improve the isolation between the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9 . For example, in some embodiments, the slot elements  300 - 1 ,  300 - 2 ,  300 - 3 ,  300 - 4 ,  300 - 5 ,  300 - 6 ,  300 - 7 ,  300 - 8 ,  300 - 9  can substantially reduce, minimize, or eliminate interference between the IFS antenna elements  200 - 1 ,  200 - 2 ,  200 - 3 ,  200 - 4 ,  200 - 5 ,  200 - 6 ,  200 - 7 ,  200 - 8 ,  200 - 9 . 
         [0039]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific system or method illustrated herein is intended to should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the spirit and scope of the claims.