PATENT DOCUMENT

Publication Number: US-8416137-B2
Application Number: US-201113229870-A
Country: US
Kind Code: B2

Title: Low-profile wide-bandwidth radio frequency antenna

Abstract:
The present invention relates to an RF antenna structure that includes a planar structure and a loading plate, such that the planar structure is mounted between a ground plane and the loading plate to form an RF antenna. The loading plate may be about parallel to the ground plane and the planar structure may be about perpendicular to the loading plate and the ground plane. The loading plate may allow the height of the RF antenna structure above the ground plane to be relatively small. For example, the height may be significantly less than one-quarter of a wavelength of RF signals of interest. The planar structure may include two conductive matching elements to help increase the bandwidth of the RF antenna structure.

Claims:
What is claimed is: 
     
       1. An antenna structure, comprising:
 a ground plane; 
 a loading plate spaced from the ground plane in a direction substantially perpendicular to the ground plane and extending substantially parallel to the ground plane; 
 a first conductive matching element extending from the loading plate toward the ground plane; 
 a first conductive element extending from the loading plate toward the ground plane; 
 a second conductive matching element extending from the first conductive element spaced from and between the ground plane and the loading plate; and 
 a second conductive element extending from the first conductive element to the first conductive matching element. 
 
     
     
       2. The antenna structure of  claim 1 , wherein the first conductive matching element is electrically connected to the loading plate and is electrically isolated from the ground plane, wherein the first conductive matching element is planar and extends substantially perpendicular to the ground plane. 
     
     
       3. The antenna structure of  claim 1 , wherein the first conductive element is electrically connected to the loading plate and the second conductive matching element is electrically connected to the first conductive element. 
     
     
       4. The antenna structure of  claim 3 , wherein the second conductive matching element extends from the first conductive element toward the first conductive matching element. 
     
     
       5. The antenna structure of  claim 4 , wherein the second conductive matching element extends substantially parallel to the ground plane and the loading plate. 
     
     
       6. The antenna structure of  claim 1 , further comprising a first dual band conductive element extending from the second conductive matching element toward the ground plane. 
     
     
       7. The antenna structure of  claim 6 , further comprising a second dual band conductive element extending from the first conductive element away from the second conductive matching element. 
     
     
       8. The antenna structure of  claim 1 , further comprising a third conductive element electrically connected to the second conductive matching element and extending from the second conductive matching element towards the ground plane. 
     
     
       9. The antenna structure of  claim 1 , wherein the first conductive matching element, the first conductive element and the second conductive matching element are in a common plane, the common plane extending substantially perpendicular to the loading plate and the ground plane. 
     
     
       10. The antenna structure of  claim 9 , wherein the common plane extends along a mid-line of the loading plate. 
     
     
       11. The antenna structure of  claim 9 , further comprising a second conductive element extending along the common plane from the first conductive element to the first conductive matching element. 
     
     
       12. The antenna structure of  claim 9 , further comprising a first dual band conductive element extending along the common plane from the second conductive matching element toward the ground plane. 
     
     
       13. The antenna structure of  claim 12 , further comprising a second dual band conductive element extending along the common plane from the first conductive element away from the second conductive matching element. 
     
     
       14. The antenna structure of  claim 9 , further comprising a third conductive element electrically connected to the second conductive matching element and extending from the second conductive matching element along the common plane towards the ground plane. 
     
     
       15. The antenna structure of  claim 9 , wherein the first conductive matching element, the first conductive element and the second conductive matching element comprise an integral conductive structure. 
     
     
       16. The antenna structure of  claim 15 , wherein the integral conductive structure further comprises a second conductive element extending along the common plane from the first conductive element to the second conductive matching element. 
     
     
       17. The antenna structure of  claim 15 , wherein the integral conductive structure further comprises a first dual band conductive element extending along the common plane from the second conductive matching element toward the ground plane. 
     
     
       18. The antenna structure of  claim 15 , wherein the integral conductive structure further comprises a second dual band conductive element extending along the common plane from the first conductive element away from the second conductive matching element. 
     
     
       19. The antenna structure of  claim 15 , wherein the integral conductive structure further comprises a third conductive element electrically connected to the second conductive matching element and extending from the second conductive matching element along the common plane towards the ground plane. 
     
     
       20. The antenna structure of  claim 15 , wherein the integral conductive structure is at least one conductive layer on an insulating substrate. 
     
     
       21. The antenna structure of  claim 20 , wherein the loading plate is at least one conductive layer on an insulating substrate. 
     
     
       22. The antenna of  claim 1 , wherein the first conductive matching element is electrically connected to the loading plate and is electrically isolated from the ground plane. 
     
     
       23. An antenna structure, comprising:
 a ground plane; 
 a loading plate spaced from the ground plane in a direction substantially perpendicular to the ground plane and extending substantially parallel to the ground plane; 
 a first conductive matching element extending from the loading plate toward the ground plane; 
 a first conductive element extending from the loading plate toward the ground plane; 
 a second conductive matching element extending from the first conductive element spaced from and between the ground plane and the loading plate; 
 a second conductive element extending from the first conductive element to the second conductive matching element. 
 
     
     
       24. An antenna structure, comprising:
 a ground plane; 
 a loading plate spaced from the ground plane in a direction substantially perpendicular to the ground plane and extending substantially parallel to the ground plane; 
 a first conductive matching element extending from the loading plate toward the ground plane; 
 a first conductive element extending from the loading plate toward the ground plane; 
 a second conductive matching element extending from the first conductive element spaced from and between the ground plane and the loading plate; and 
 a first dual band conductive element extending from the second conductive matching element toward the ground plane. 
 
     
     
       25. An antenna structure, comprising:
 a ground plane; 
 a loading plate spaced from the ground plane in a direction substantially perpendicular to the ground plane and extending substantially parallel to the ground plane; 
 a first conductive matching element extending from the loading plate toward the ground plane; 
 a first conductive element extending from the loading plate toward the ground plane; 
 a second conductive matching element extending from the first conductive element spaced from and between the ground plane and the loading plate; and 
 a third conductive element electrically connected to the second conductive matching element and extending from the second conductive matching element towards the ground plane. 
 
     
     
       26. An antenna structure, comprising:
 a ground plane; 
 a loading plate spaced from the ground plane in a direction substantially perpendicular to the ground plane and extending substantially parallel to the ground plane; 
 a first conductive matching element extending from the loading plate toward the ground plane; 
 a first conductive element extending from the loading plate toward the ground plane; 
 a second conductive matching element extending from the first conductive element spaced from and between the ground plane and the loading plate; and 
 a first dual band conductive element extending from the second conductive matching element toward the ground plane; and 
 a second dual band conductive element extending from the first conductive element away from the second conductive matching element.

Description:
This application is a Continuation of U.S. patent application Ser. No. 12/415,604, entitled LOW-PROFILE WIDE-BANDWIDTH RADIO FREQUENCY ANTENNA, filed Mar. 31, 2009, currently pending, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/050,028, entitled ANTENNAS FOR WLAN ACCESS POINTS, filed May 2, 2008, the disclosures of which are both hereby incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of the present invention relate to radio frequency (RF) antennas, which may be used in RF communications systems. 
     BACKGROUND OF THE INVENTION 
     As technology progresses, wireless devices tend toward smaller sizes and wireless communications protocols become increasingly sophisticated. Support for multiple communications bands with wider bandwidths in a single device is becoming available. For example, the Institute for Electrical and Electronics Engineers (IEEE) 802.11n wireless communications standard specifies support for wireless communications using a first communications band between about 2.4 gigahertz (GHz) and about 2.4835 GHz, and a second communications band between about 4.9 GHz and 5.825 GHz. Therefore, the second communications band has a bandwidth of about 17.25%. 
     A wireless local area network (WLAN) access point may be installed in a hot spot to provide wireless access to end users. The WLAN access point may need to be compact for ease and flexibility of installation. Therefore, any radio frequency (RF) antennas installed in the WLAN access point may have significant size and dimension restrictions. For example, any RF antenna in a WLAN access point may be restricted in height to about 12 millimeters (mm). Additionally, the WLAN access point may be a multiple-input multiple-output (MIMO) WLAN access point, which utilizes multiple antennas. Therefore, the RF antennas in a MIMO WLAN access point may have additional size and dimension restrictions, and may need to be of reasonable cost. If a WLAN access point supports communications using the IEEE 802.11n communications protocol, an RF antenna in the WLAN access point may need to support the 2.4 GHz to 2.4835 GHz communications band, the 4.9 GHz and 5.825 GHz communications band, or both. Further, if a MIMO WLAN access point supports communications using the IEEE 802.11n communications protocol, one or more RF antennas in the access point may be a single band antenna for isolation from other bands, or one or more RF antenna in the access point may support two or more communication bands to minimize the number of RF antennas. Thus, there is a need for an RF antenna that is small, cost effective, wide bandwidth, dual band, or any combination thereof. 
     SUMMARY OF THE EMBODIMENTS 
     The present invention relates to an RF antenna structure that includes a planar structure and a loading plate, such that the planar structure is mounted between a ground plane and the loading plate to form an RF antenna. The loading plate may be about parallel to the ground plane and the planar structure may be about perpendicular to the loading plate and the ground plane. The loading plate may allow the height of the RF antenna structure above the ground plane to be relatively small. For example, the height may be significantly less than one-quarter of a wavelength of RF signals of interest. The planar structure may include two conductive matching elements to help increase the bandwidth of the RF antenna structure. In one embodiment of the present invention, the bandwidth of the RF antenna may be greater than about 15 percent of the center frequency of a communications band of interest. 
     All or part of the RF antenna structure may include metal rods, stamped metal, printed circuits, or any combination thereof. In one embodiment of the present invention, the RF antenna is a single band RF antenna. In an alternate embodiment of the present invention, the RF antenna is a dual band RF antenna. The RF antenna may be used in a wireless local area network (WLAN) access point. The WLAN access point may be a multiple-input multiple-output (MIMO) WLAN access point, in which case the MIMO WLAN access point will include two or more RF antenna elements. The WLAN access point may operate using the IEEE 802.11n wireless communications standard and may utilize the 2.4 GHz to 2.4835 GHz communications band, the 4.9 GHz and 5.825 GHz communications band, or both. 
     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 
       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. 
         FIG. 1  shows a three-dimensional view from one side and underneath an RF antenna structure according to one embodiment of the present invention. 
         FIG. 2  shows a three-dimensional view from one side and above the RF antenna structure illustrated in  FIG. 1 . 
         FIG. 3  shows a three-dimensional view from one side and underneath a dual band RF antenna structure according to an alternate embodiment of the present invention. 
         FIG. 4  shows a three-dimensional view from one side and above the dual band RF antenna structure illustrated in  FIG. 3 . 
         FIG. 5  shows a three-dimensional view from one side and underneath the RF antenna structure according to an alternate embodiment of the RF antenna structure. 
         FIG. 6  shows a three-dimensional view from one side and above the RF antenna structure illustrated in  FIG. 5 . 
         FIG. 7  shows a three-dimensional view from one side and underneath the dual band RF antenna structure according to an alternate embodiment of the dual band RF antenna structure. 
         FIG. 8  shows a three-dimensional view from one side and above the dual band RF antenna structure illustrated in  FIG. 7 . 
         FIG. 9  shows a three-dimensional view from one side and underneath the RF antenna structure according to an additional embodiment of the RF antenna structure. 
         FIG. 10  shows a three-dimensional view from one side and underneath the RF antenna structure according to another embodiment of the RF antenna structure. 
         FIG. 11  shows a three-dimensional view from one side and above the RF antenna structure illustrated in  FIG. 10 . 
         FIG. 12  shows a three-dimensional view from one side and underneath the dual band RF antenna structure according to an additional embodiment of the dual band RF antenna structure. 
         FIG. 13  shows a three-dimensional view from one side and underneath the dual band RF antenna structure according to another embodiment of the dual band RE antenna structure. 
         FIG. 14  shows a three-dimensional view from one side and underneath the dual band RF antenna structure according to a supplemental embodiment of the dual band RF antenna structure. 
         FIG. 15  shows details of the dual band RF antenna structure illustrated in  FIG. 14 . 
         FIG. 16  shows details of the RF antenna structure illustrated in  FIG. 1 . 
         FIG. 17  shows details of the RF antenna structure illustrated in  FIG. 10 . 
         FIG. 18  shows additional details of the dual band RF antenna structure illustrated in  FIG. 14 . 
         FIG. 19  shows a loading, plate according to a first embodiment of the loading plate. 
         FIG. 20  shows the loading plate according to a second embodiment of the loading plate. 
         FIG. 21  shows the loading plate according to a third embodiment of the loading plate. 
         FIG. 22  shows the loading plate according to a fourth embodiment of the loading plate. 
         FIG. 23  shows a planar structure, which may be used in the RF antenna structure illustrated in  FIG. 10  according to a first embodiment of the planar structure. 
         FIG. 24  shows the planar structure, which may be used in the RF antenna structure illustrated in  FIG. 10  according to a second embodiment of the planar structure. 
         FIG. 25  shows the planar structure, which may be used in the RF antenna structure illustrated in  FIG. 10  according to a third embodiment of the planar structure. 
         FIG. 26  shows the planar structure, which may be used in the dual band RF antenna structure illustrated in  FIG. 14  according to a fourth embodiment of the planar structure. 
         FIG. 27  shows the planar structure, which may be used in the dual band RF antenna structure illustrated in  FIG. 14  according to a fifth embodiment of the planar structure. 
         FIG. 28  shows the planar structure, which may be used in the dual band RF antenna structure illustrated in  FIG. 14  according to a sixth embodiment of the planar structure. 
         FIG. 29  shows an application example of the present invention used in a wireless local area network (WLAN) access point. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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. 
     The present invention relates to an RF antenna structure that includes a planar structure and a loading plate, such that the planar structure is mounted between a ground plane and the loading plate to form an RF antenna. The loading plate may be about parallel to the ground plane and the planar structure may be about perpendicular to the loading plate and the ground plane. The loading plate may allow the height of the RF antenna structure above the ground plane to be relatively small. For example, the height may be significantly less than one-quarter of a wavelength of RF signals of interest. The planar structure may include two conductive matching elements to help increase the bandwidth of the RF antenna structure. In one embodiment of the present invention, the bandwidth of the RF antenna may be greater than about 15 percent of the center frequency of a communications band of interest. 
     All or part of the RF antenna structure may include metal rods, stamped metal, printed circuits, or any combination thereof. In one embodiment of the present invention, the RF antenna is a single band RF antenna. In an alternate embodiment of the present invention, the RF antenna is a dual band RF antenna. The RF antenna may be used in a wireless local area network (WLAN) access point. The WLAN access point may be a multiple-input multiple-output (MIMO) WLAN access point, in which case the MIMO WLAN access point will include two or more RF antenna elements. The WLAN access point may operate using the IEEE 802.11n wireless communications standard and may utilize the 2.4 gigahertz (GHz) to 2.4835 GHz communications band, the 4.9 GHz and 5.825 GHz communications band, or both. 
       FIG. 1  shows a three-dimensional view from one side and underneath an RF antenna structure  10  according to one embodiment of the present invention. The RF antenna structure  10  includes a loading plate  12 , which has a first end  14 , a second end  16 , a first planar surface  18 , and a lengthwise centerline  20  that longitudinally divides the first planar surface  18  into about equal halves. The loading plate  12  may be flat having sides and ends of any shape. In one embodiment, the loading plate  12  is flat and about rectangular. Additionally, the RF antenna structure  10  includes a first conductive matching element  22 , which has a third end  24 , a fourth end  26 , and a first edge  28 , a first conductive element  30 , which has a fifth end  32  and a sixth end  34 , and a second conductive matching element  36 , which has a seventh end  38  and an eighth end  40 . In one embodiment of the loading plate  12 , the first planar surface  18  provides a first planar conductive surface. In one embodiment of the loading plate  12 , the first planar conductive surface is about rectangular. 
     The first conductive matching element  22 , the first conductive element  30 , and the second conductive matching element  36  may form a planar structure, which is about perpendicular to the first planar conductive surface. The third end  24  may be adjacent to the first planar surface  18  and may be electrically connected to the first planar conductive surface. Additionally, the third end  24  may be biased toward the first end  14 . In one embodiment of the first conductive matching element  22 , the first edge  28  may be about flush with the first end  14 , at least a portion of the third end  24  may contact a portion of the first planar surface  18 , at least a portion of the third end  24  may contact the first planar conductive surface along the lengthwise centerline  20  of the first planar surface  18 , or any combination thereof. The first edge  28  may be about perpendicular to the first planar conductive surface. 
     The first conductive matching element  22  may be flat having sides and ends of any shape. In one embodiment, the first conductive matching element  22  is flat and about rectangular, as shown. The first conductive element  30  may be of any shape. In one embodiment, the first conductive element  30  is about cylindrically shaped, as shown. The first conductive element  30  may be formed from a metallic rod. In an alternate embodiment, the first conductive element  30  is flat and about rectangular. The second conductive matching element  36  may be of any shape. In one embodiment, the second conductive matching element  36  is about cylindrically shaped, as shown. The second conductive matching element  36  may be formed from a metallic rod. In an alternate embodiment, the second conductive matching element  36  is flat and about rectangular. 
     The fifth end  32  may be adjacent to the first planar surface  18  and may be electrically connected to the first planar conductive surface. The seventh end  38  may be biased toward the sixth end  34  and may be electrically connected to the first conductive element  30 . The eighth end  40  may be between the seventh end  38  and the first conductive matching element  22  and the fourth end  26  may be used to transfer RF signals between the RF antenna structure  10  and RF communications circuitry (not shown). 
       FIG. 2  shows a three-dimensional view from one side and above the RF antenna structure  10  illustrated in  FIG. 1 . The RF antenna structure  10  is mounted above a ground plane  42 , such that the first planar conductive surface and the first planar surface  18  are about parallel to the ground plane  42 . The RF antenna structure  10  has a second planar surface  44 . In one embodiment of the first conductive matching element  22 , an RF antenna feedline  46  is electrically connected between the fourth end  26  and the RF communications circuitry (not shown). A ground plane clearance hole  48  allows the RF antenna feedline  46  to pass through the ground plane  42  without making an electrical connection to the ground plane  42 . 
     In one embodiment of the loading plate  12 , the second planar surface  44  provides the first planar conductive surface. In one embodiment of the present invention, the loading plate  12 , the planar structure, and the ground plane  42  form a modified inverted-L single band RF antenna, which may be used to transmit RF signals, receive RF signals, or both. The first conductive matching element  22  provides the short section of the L and the loading plate  12  provides the long section of the L. The loading plate  12 , the first conductive matching element  22 , the first conductive element  30 , and the second conductive matching element  36  provide the modifications to the modified inverted-L antenna, thereby providing an increased bandwidth compared to a traditional inverted-L antenna. The fourth end  26  may be between the third end  24  and the ground plane  42 , and the sixth end  34  may be between the fifth end  32  and the ground plane  42 . 
     The modified inverted-L single band RF antenna may be low profile. In an exemplary embodiment of the present invention, a distance between the first planar conductive surface and the ground plane  42  is less than about 12 millimeters. In one embodiment of the RF antenna structure  10 , at least a portion of the fifth end  32  may contact a portion of the first planar surface  18 , at least a portion of the fifth end  32  may contact a portion of the first planar conductive surface at the lengthwise centerline  20  of the first planar surface  18 , the fifth end  32  may be biased towards the second end  16 , the seventh end  38  may be adjacent to the sixth end  34 , or any combination thereof. 
     The modified inverted-L single band RF antenna may provide a reasonably uniform omni-directional radiation pattern in the hemisphere above the ground plane  42 . If the modified inverted-L single band RF antenna is used in a ceiling mounted WLAN access point with the RF antenna structure  10  closer to the floor and the ground plane  42  closer to the ceiling, the radiation pattern may be directed relatively uniformly downward throughout a room to provide good coverage to a number of end users. In one embodiment of the present invention, the modified inverted-L single band RF antenna is associated with an operating band having a center frequency, an upper frequency, and a lower frequency. 
     Return loss is one way to characterize an antenna&#39;s bandwidth. The return loss in an antenna is the difference between RF power delivered to an antenna and reflected RF power received back from the antenna, and is dependent on the load impedance. In one embodiment of the present invention, the load impedance is about 50 ohms; therefore the design target for the antenna input impedance is about 50 ohms in the desired operating bands. Low return loss indicates that most of the delivered RF power is being reflected back and that little of the delivered RF power is being radiated by the antenna. Conversely, high return loss indicates that little of the delivered RF power is being reflected back and that most of the delivered RF power is being radiated by the antenna. Therefore, the antenna will have high return loss (e.g. greater than 10 decibels) when transmitting RF signals with frequencies inside an operating band and will have low return loss when transmitting RF signals with frequencies outside the operating band. In one embodiment of the present invention, the bandwidth of an RF antenna may be characterized as the contiguous range of frequencies over which the return loss is greater than 10 decibels, such that a return loss with a 50 ohm load impedance is greater than about 10 decibels over a contiguous range of frequencies between the lower frequency and the upper frequency. The bandwidth may be expressed as a percentage of the center frequency, such that if f_upper and f_lower are the upper and lower frequencies bounding the range where the return loss is greater than 10 decibels, then the percentage bandwidth is given by (percentage bandwidth=((f_upper−f_lower)/f_center))×100), where f_center=(f_upper+f_lower)/2. 
     In one exemplary embodiment of the modified inverted-L single band RF antenna, the bandwidth of the modified inverted-L single band RF antenna is at least 15 percent of the center frequency. In another exemplary embodiment of the modified inverted-L single band RF antenna, the center frequency is about 5.3625 gigahertz, the lower frequency is less than about 4.9 gigahertz, the upper frequency is greater than about 5.825 gigahertz, or any combination thereof. 
       FIG. 3  shows a three-dimensional view from one side and underneath a dual band RF antenna structure  50  according to an alternate embodiment of the present invention. The dual band RF antenna structure  50  illustrated in  FIG. 3  is similar to the RF antenna structure  10  illustrated in  FIG. 1 , except the dual band RF antenna structure  50  illustrated in  FIG. 3  includes a first dual band conductive element  52  and the fifth end  32  is biased closer to the first end  14  than the fifth end  32  illustrated in  FIG. 1 . The first dual band conductive element  52  includes a first dual band end  54  and a second dual band end  56 . The first dual band end  54  may be adjacent to the eighth end  40  and the eighth end  40  may be electrically connected to the first dual band conductive element  52 . 
       FIG. 4  shows a three-dimensional view from one side and above the dual band RF antenna structure  50  illustrated in  FIG. 3 . The second dual band end  56  may be electrically connected to the ground plane  42  at a ground plane attachment point  58 . The first dual band conductive element  52  may be of any shape. In one embodiment, the first dual band conductive element  52  is about cylindrically shaped, as shown. The first dual band conductive element  52  may be formed from a metallic rod. In an alternate embodiment, the first dual band conductive element  52  is flat and about rectangular. In one embodiment of the present invention, the loading plate  12 , the first conductive matching element  22 , and the ground plane  42  may form a modified inverted-L RF antenna, and a portion of the loading plate  12  between the first end  14  and the fifth end  32 , the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the first dual band conductive element  52 , and the ground plane  42  may form a bent folded-monopole RF antenna. Therefore, the loading plate  12 , the planar structure, and the ground plane  42  may form a dual band RF antenna by superposition of the bent folded-monopole RF antenna and the modified inverted-L RE antenna. The dual band RF antenna may be used to transmit RF signals, receive RF signals, or both. 
     The dual band RF antenna may provide a reasonably uniform omni-directional radiation pattern in the hemisphere above the ground plane  42 . If the dual band RF antenna is used in a ceiling mounted WLAN access point with the dual band RF antenna structure  50  closer to the floor and the ground plane  42  closer to the ceiling, the radiation pattern may be directed relatively uniformly downward throughout a room to provide good coverage to a number of end users. In one embodiment of the present invention, the dual band RF antenna is associated with a first operating band having a first center frequency, a first upper frequency, and a first lower frequency, and a second operating band having a second center frequency, a second upper frequency, and a second lower frequency. 
     In one exemplary embodiment of the dual band RF antenna, a first operating band bandwidth of the dual band RF antenna is at least 15 percent of the first center frequency, such that a magnitude of the first upper frequency minus a magnitude of the first lower frequency is at least 15 percent of a magnitude of the first center frequency, and a return loss with a 50 ohm load impedance is greater than about 10 decibels across a contiguous range of frequencies between the first lower frequency and the first upper frequency. In another exemplary embodiment of the dual band RF antenna, the first center frequency is about 5.3625 gigahertz, the first lower frequency is less than about 4.9 gigahertz, the first upper frequency is greater than about 5.825 gigahertz, the second center frequency is about 2.44175 gigahertz, or any combination thereof. 
       FIG. 5  shows a three-dimensional view from one side and underneath the RF antenna structure  10  according to an alternate embodiment of the RF antenna structure  10 . The RF antenna structure  10  illustrated in  FIG. 5  is similar to the RF antenna structure  10  illustrated in  FIG. 1 , except the first conductive element  30  and the second conductive matching element  36  illustrated in  FIG. 1  are both cylindrically shaped, whereas the first conductive element  30  and the second conductive matching element  36  illustrated in  FIG. 5  are both rectangularly shaped. The first conductive matching element  22  has a second edge  60 , which may be about perpendicular to the first planar conductive surface and may be about parallel to and opposite from the first edge  28 . 
     The second edge  60  may be between the first edge  28  and the first conductive element  30 . The first conductive element  30  has a third edge  62  and a fourth edge  64 , in which both may be about perpendicular to the first planar conductive surface. The fourth edge  64  may be about parallel to and opposite from the third edge  62 , and the third edge  62  may be between the fourth edge  64  and the first conductive matching element  22 . In one embodiment of the first conductive element  30 , the fourth edge  64  is about flush with the second end  16 , at least a portion of the seventh end  38  contacts a portion of the third edge  62 , or both.  FIG. 6  shows a three-dimensional view from one side and above the RF antenna structure  10  illustrated in  FIG. 5 . 
       FIG. 7  shows a three-dimensional view from one side and underneath the dual band RF antenna structure  50  according to an alternate embodiment of the dual band RF antenna structure  50 . The dual band RF antenna structure  50  illustrated in  FIG. 7  is similar to the dual band RF antenna structure  50  illustrated in  FIG. 3 , except the first conductive element  30 , the second conductive matching element  36 , and the first dual band conductive element  52  illustrated in  FIG. 3  are all three cylindrically shaped, whereas the first conductive element  30 , the second conductive matching element  36 , and the first dual band conductive element  52  illustrated in  FIG. 7  are all three rectangularly shaped. The first conductive matching element  22  has the second edge  60 , which may be about perpendicular to the first planar conductive surface and may be about parallel to and opposite from the first edge  28 . 
     The second edge  60  may be between the first edge  28  and the first conductive element  30 . The first conductive element  30  has the third edge  62  and the fourth edge  64 , in which both may be about perpendicular to the first planar conductive surface. The fourth edge  64  may be about parallel to and opposite from the third edge  62 , and the third edge  62  may be between the fourth edge  64  and the first conductive matching element  22 . The first dual band conductive element  52  has a first dual band edge  66 , such that at least a portion of the eighth end  40  may contact a portion of the first dual band edge  66 .  FIG. 8  shows a three-dimensional view from one side and above the dual band RF antenna structure  50  illustrated in  FIG. 7 . 
       FIG. 9  shows a three-dimensional view from one side and underneath the RF antenna structure  10  according to an additional embodiment of the RF antenna structure  10 . The RF antenna structure  10  illustrated in  FIG. 9  is similar to the RF antenna structure  10  illustrated in  FIG. 5 , except the RF antenna structure  10  illustrated in  FIG. 9  includes a second conductive element  68 . The second conductive element  68  has a ninth end  70 , a tenth end  72 , and a fifth edge  74 . The second conductive element  68  may be flat having edges and ends of any shape. In one embodiment, the second conductive element  68  is flat and about rectangular, as shown. The ninth end  70  may be electrically connected to the first conductive matching element  22  and at least a portion of the ninth end  70  may contact a portion of the second edge  60 . The tenth end  72  may be electrically connected to the first conductive element  30  and at least a portion of the tenth end  72  may contact a portion of the third edge  62 . The fifth edge  74  may be electrically connected to the first planar conductive surface. In one embodiment of the second conductive element  68 , the fifth edge  74  may be about flush with the third end  24 , the fifth edge  74  may be about flush with the fifth end  32 , at least a portion of the fifth edge  74  may contact a portion of the first planar surface  18 , or any combination thereof. 
       FIG. 10  shows a three-dimensional view from one side and underneath the RF antenna structure  10  according to another embodiment of the RF antenna structure  10 . The RF antenna structure  10  illustrated in  FIG. 10  is similar to the RF antenna structure  10  illustrated in  FIG. 9 , except the RF antenna structure  10  illustrated in  FIG. 10  includes a third conductive element  76 . The third conductive element  76  has an eleventh end  78 , a twelfth end  80 , and a sixth edge  82 . The third conductive element  76  may be flat having edges and ends of any shape. In one embodiment, the third conductive element  76  is flat and about square, as shown. In one embodiment of the third conductive element  76 , the eleventh end  78  may be electrically connected to the first conductive matching element  22 , at least a portion of the eleventh end  78  may contact a portion of the fourth end  26 , the second edge  60  may be about flush with the sixth edge  82 , the twelfth end  80  may be used to transfer RF signals between the RE antenna structure  10  and RF communications circuitry (not shown), or any combination thereof.  FIG. 11  shows a three-dimensional view from one side and above the RF antenna structure  10  illustrated in  FIG. 10 . 
       FIG. 12  shows a three-dimensional view from one side and underneath the dual band RF antenna structure  50  according to an additional embodiment of the dual band RF antenna structure  50 . The dual band RF antenna structure  50  illustrated in  FIG. 12  is similar to the dual band RF antenna structure  50  illustrated in  FIG. 7 , except the dual band RF antenna structure  50  illustrated in  FIG. 12  includes the second conductive element  68 . The second conductive element  68  has the ninth end  70 , the tenth end  72 , and the fifth edge  74 . The second conductive element  68  may be flat having edges and ends of any shape. In one embodiment, the second conductive element  68  is flat and about rectangular, as shown. The ninth end  70  may be electrically connected to the first conductive matching element  22  and at least a portion of the ninth end  70  may contact a portion of the second edge  60 . The tenth end  72  may be electrically connected to the first conductive element  30  and at least a portion of the tenth end  72  may contact a portion of the third edge  62 . The fifth edge  74  may be electrically connected to the first planar conductive surface. In one embodiment of the second conductive element  68 , the fifth edge  74  may be about flush with the third end  24 , the fifth edge  74  may be about flush with the fifth end  32 , at least a portion of the fifth edge  74  may contact a portion of the first planar surface  18 , or any combination thereof. 
       FIG. 13  shows a three-dimensional view from one side and underneath the dual band RF antenna structure  50  according to another embodiment of the dual band RF antenna structure  50 . The dual band RF antenna structure  50  illustrated in  FIG. 13  is similar to the dual band RF antenna structure  50  illustrated in  FIG. 12 , except the dual band RF antenna structure  50  illustrated in  FIG. 13  includes a second dual band conductive element  84 . The second dual band conductive element  84  has a third dual band end  86 , a fourth dual band end  88 , and a second dual band edge  90 . The second dual band conductive element  84  may be flat having edges and ends of any shape. In one embodiment, the second dual band conductive element  84  is flat and about rectangular, as shown. In one embodiment of the second dual band conductive element  84 , at least a portion of the third dual band end  86  may contact a portion of the fourth edge  64 , the third dual band end  86  may be electrically connected to the first conductive element  30 , at least a portion of the second dual band edge  90  may contact a portion of the first planar surface  18 , the second dual band edge  90  may be electrically connected to the first planar conductive surface, the fourth dual band end  88  may be about flush with the second end  16 , or any combination thereof. 
       FIG. 14  shows a three-dimensional view from one side and underneath the dual band RF antenna structure  50  according to a supplemental embodiment of the dual band RF antenna structure  50 . The dual band RF antenna structure  50  illustrated in  FIG. 14  is similar to the dual band RF antenna structure  50  illustrated in  FIG. 13 , except the dual band RF antenna structure  50  illustrated in  FIG. 14  includes the third conductive element  76 . The third conductive element  76  has the eleventh end  78 , the twelfth end  80 , and the sixth edge  82 . The third conductive element  76  may be flat having edges and ends of any shape. In one embodiment, the third conductive element  76  is flat and about square, as shown. In one embodiment of the third conductive element  76 , the eleventh end  78  may be electrically connected to the first conductive matching element  22 , at least a portion of the eleventh end  78  may contact a portion of the fourth end  26 , the second edge  60  may be about flush with the sixth edge  82 , the twelfth end  80  may be used to transfer RF signals between the dual band RF antenna structure  50  and RF communications circuitry (not shown), or any combination thereof. 
       FIG. 15  shows details of the dual band RF antenna structure  50  illustrated in  FIG. 14 . A first effective length  92  is the distance from the first end  14  to fifth end  32  of the first conductive element  30  and may be on the order of about one quarter wavelength of a center frequency of one of the two frequency bands associated with the dual band RF antenna structure  50 . A first length  94  is the distance from the first end  14  to the second end  16  and may be on the order of about one quarter wavelength of a center frequency of the other of the two frequency bands associated with the dual band RF antenna structure  50 . 
     A way to relate the first length  94  and the first effective length  92  to frequency is presented below. A fundamental equation relating the wavelength (λ) of a radiated RF signal to the frequency (F) of the radiated RF signal traveling at the speed of light (C) is shown in EQ. 1 below.
 
λ= C/F.   EQ. 1
 
     Since C is about equal to 3×10 8  meters/second (M/S), substituting the value of C into EQ. 1 provides EQ. 2 below.
 
λ=(3×10 8  M/S)/ F.   EQ. 2
 
     Converting the speed of light into the units of millimeters (mm) per nanosecond (mm/nS), and frequency into GHz (i.e. 1/nS) provides EQ. 3 below.
 
λ=(300 mm/nS)/ F (GHz).  EQ. 3
 
     Useful values may occur at λ/2, λ/4, and λ/8 as shown in EQ. 4, EQ. 5, and EQ. 6, respectively below.
 
λ/2=(150 mm/nS)/ F (GHz).  EQ. 4
 
λ/4=(75 mm/nS)/ F (GHz).  EQ. 5
 
λ/8=(37.5 mm/nS)/ F (GHz).  EQ. 6
 
     In one embodiment of the present invention, the RF antenna structure  10  and the ground plane  42  form the modified inverted-L single band RF antenna, which is associated with an operating band having a center frequency. If the first length  94  is on the order of about one quarter wavelength (λ/4) of the center frequency, then EQ. 5 relates the first length  94  to the center frequency. If a factor of two tolerance is established, then EQ. 4 and EQ. 6 provide tolerance limits for the first length  94 . In an exemplary embodiment of the modified inverted-L single band RF antenna, a first value is equal to about 150 mm/nS divided by a magnitude of the center frequency (in GHz), a second value is equal to about 37.5 mm/nS divided by the magnitude of the center frequency (in GHz), and a magnitude of the first length  94  is between the first value and the second value. 
     In an alternate embodiment of the present invention, the dual band RF antenna structure  50  and the ground plane  42  form the dual band RF antenna, which is associated with a first operating band having a first center frequency and a second operating band having a second center frequency. If the first length  94  is on the order of about one quarter wavelength (λ/4) of the second center frequency, then EQ. 5 relates the first length  94  to the second center frequency. If a factor of two tolerance is established, then EQ. 4 and EQ. 6 provide tolerance limits for the first length  94 . Similarly, if the first effective length  92  is on the order of about one quarter wavelength (λ/4) of the first center frequency, then EQ. 5 relates the first effective length  92  to the first center frequency. If a factor of two tolerance is established, then EQ. 4 and EQ. 6 provide tolerance limits for the first effective length  92 . In an exemplary embodiment of the dual band RF antenna, a first value is equal to about 150 mm/nS divided by a magnitude of the first center frequency (in GHz), a second value is equal to about 37.5 mm/nS divided by the magnitude of the first center frequency (in GHz), a third value is equal to about 150 mm/nS divided by a magnitude of the second center frequency (in GHz), a fourth value is equal to about 37.5 mm/nS divided by the magnitude of the second center frequency (in GHz), a magnitude of the first length  94  is between the third value and the fourth value, and a magnitude of the first effective length  92  is between the first value and the second value. 
       FIG. 16  shows details of the RE antenna structure  10  illustrated in  FIG. 1 . The loading plate  12  has the first length  94  and a first width  96 , in which both may be about parallel to the ground plane  42  ( FIG. 2 ). The first conductive matching element  22  has a second length  98  and a second width  100 , such that the second length  98  may be about perpendicular to the first planar conductive surface, the second width  100  may be about parallel to the first length  94 , or both. The first conductive element  30  has a third length  102  and a third width  104 , such that the third length  102  may be about perpendicular to the first planar conductive surface. The second conductive matching element  36  has a fourth length  106  and a fourth width  108 , such that the fourth length  106  is about parallel to the first length  94 . 
       FIG. 17  shows details of the RF antenna structure  10  illustrated in  FIG. 10 . The loading plate  12  has the first length  94  and the first width  96 , in which both may be about parallel to the ground plane  42  ( FIG. 11 ). The first conductive matching element  22  has the second length  98  and the second width  100 , such that the second length  98  may be about perpendicular to the first planar conductive surface, the second width  100  may be about parallel to the first length  94 , or both. The first conductive element  30  has the third length  102  and the third width  104 , such that the third length  102  may be about perpendicular to the first planar conductive surface, the third width  104  may be about parallel to the first length  94 , or both. The second conductive matching element  36  has the fourth length  106  and the fourth width  108 , such that the fourth length  106  is about parallel to the first length  94 , the fourth width  108  may be about perpendicular to the first planar conductive surface, or both. The second conductive element  68  has a fifth length  110  and a fifth width  112 . The fifth length  110  may be about parallel to the first length  94 , the fifth width  112  may be about perpendicular to the first planar conductive surface, or both. The third conductive element  76  has a sixth length  114  and a sixth width  116 . The sixth length  114  may be about perpendicular to the first planar conductive surface, sixth width  116  may be about parallel to the first length  94 , or both. 
       FIG. 18  shows additional details of the dual band RF antenna structure  50  illustrated in  FIG. 14 . The loading plate  12  has the first length  94  and the first width  96 , in which both may be about parallel to the ground plane  42  ( FIG. 15 ). The first conductive matching element  22  has the second length  98  and the second width  100 , such that the second length  98  may be about perpendicular to the first planar conductive surface, the second width  100  may be about parallel to the first length  94 , or both. The first conductive element  30  has the third length  102  and the third width  104 , such that the third length  102  may be about perpendicular to the first planar conductive surface, the third width  104  may be about parallel to the first length  94 , or both. The second conductive matching element  36  has the fourth length  106  and the fourth width  108 , such that the fourth length  106  may be about parallel to the first length  94 , the fourth width  108  may be about perpendicular to the first planar conductive surface, or both. The second conductive element  68  has the fifth length  110  and the fifth width  112 . The fifth length  110  may be about parallel to the first length  94 , the fifth width  112  may be about perpendicular to the first planar conductive surface, or both. The third conductive element  76  has the sixth length  114  and the sixth width  116 . The sixth length  114  may be about perpendicular to the first planar conductive surface, the sixth width  116  may be about parallel to the first length  94 , or both. The first dual band conductive element  52  has a first dual band length  118  and a first dual band width  120 . The first dual band length  118  may be about perpendicular to the first planar conductive surface, the first dual band width  120  may about parallel to the first length  94 , or both. The second dual band conductive element  84  has a second dual band length  122  and a second dual band width  124 . The second dual band length  122  may be about parallel to the first length  94 , the second dual band width  124  may be about perpendicular to the first planar conductive surface, or both. 
       FIG. 19  shows the loading plate  12  according to a first embodiment of the loading plate  12 . The loading plate  12  may be formed using a first metallic sheet  126 , such as a stamped metal sheet. The first metallic sheet  126  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The loading plate  12  has the first planar surface  18  and the second planar surface  44 , either of which may provide the first planar conductive surface and the other may provide a second planar conductive surface. The first planar conductive surface may be continuously conductive without any insulating areas. 
       FIG. 20  shows the loading plate  12  according to a second embodiment of the loading plate  12 . The loading plate  12  may be formed using a first loading plate conductive layer  128  and a loading plate dielectric layer  130 . The first loading plate conductive layer  128  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The loading plate dielectric layer  130  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first loading plate conductive layer  128  is about parallel to the loading plate dielectric layer  130 . The first loading plate conductive layer  128  may be bonded directly to the loading plate dielectric layer  130 , or there may be one or more intervening layers between the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . Printed circuit board (PCB) material may provide the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . The first loading plate conductive layer  128  provides the first planar surface  18 , which provides the first planar conductive surface. The loading plate dielectric layer  130  provides the second planar surface  44 . The first planar conductive surface may be continuously conductive without any insulating areas. PCB material may typically be inexpensive, and antennas fabricated using PCB material may be very cost effective. Additionally, other elements of a WLAN access point may be provided using PCB material; therefore, providing the RF antenna structure  10  or the dual band RF antenna structure  50  using PCB material may provide commonality of construction materials, methods, or both. Further, PCB materials typically have a dielectric constant greater than one; therefore, sizes of the RF antenna structure  10  or the dual band RF antenna structure  50  using PCB material may be different from the sizes of the RF antenna structure  10  or the dual band RF antenna structure  50 , respectively, when using a metallic sheet or other materials, which may be advantageous in certain applications. 
       FIG. 21  shows the loading plate  12  according to a third embodiment of the loading plate  12 . The loading plate  12  may be formed using the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . The first loading plate conductive layer  128  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The loading plate dielectric layer  130  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first loading plate conductive layer  128  is about parallel to the loading plate dielectric layer  130 . The first loading plate conductive layer  128  may be bonded directly to the loading plate dielectric layer  130 , or there may be one or more intervening layers between the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . PCB material may provide the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . 
     The loading plate dielectric layer  130  provides the first planar surface  18  and the first loading plate conductive layer  128  provides the second planar surface  44 , which provides the first planar conductive surface. However, since the planar structure (not shown) is mounted adjacent to the first planar surface  18  and since the planar structure (not shown) is electrically connected to the first planar conductive surface, which resides on the second planar surface  44 , the loading plate dielectric layer  130  includes multiple via holes  132  to provide electrically conductive pathways between the planar structure (not shown) and the first loading plate conductive layer  128 , which may or may not have the multiple via holes  132 . Therefore, the first planar conductive surface may be continuously conductive without any insulating areas, or the first planar conductive surface may be continuously conductive without any insulating areas except for the multiple via holes  132 . Each of the multiple via holes  132  may be conductively plated or may include a conductive element traversing through the hole. 
       FIG. 22  shows the loading plate  12  according to a fourth embodiment of the loading plate  12 . The loading plate  12  may be formed using the first loading plate conductive layer  128 , a second loading plate conductive layer  134 , and the loading plate dielectric layer  130 , which is between the first loading plate conductive layer  128  and the second loading plate conductive layer  134 . The first loading plate conductive layer  128  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The second loading plate conductive layer  134  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The loading plate dielectric layer  130  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first loading plate conductive layer  128  may be bonded directly to the loading plate dielectric layer  130 , or there may be one or more intervening layers between the first loading plate conductive layer  128  and the loading plate dielectric layer  130 . Similarly, the second loading plate conductive layer  134  may be bonded directly to the loading plate dielectric layer  130 , or there may be one or more intervening layers between the second loading plate conductive layer  134  and the loading plate dielectric layer  130 . PCB material may provide the first loading plate conductive layer  128 , the second loading plate conductive layer  134 , and the loading plate dielectric layer  130 . 
     The first loading plate conductive layer  128  provides the first planar surface  18  and the second loading plate conductive layer  134  provides the second planar surface  44 . The first planar surface  18  may provide the first planar conductive surface and the second planar surface  44  may provide a second planar conductive surface. The loading plate dielectric layer  130  may include multiple via holes  132  to provide electrically conductive pathways between the first loading plate conductive layer  128  and the second loading plate conductive layer  134 , thereby electrically connecting the first loading plate conductive layer  128  to the second loading plate conductive layer  134 . The first loading plate conductive layer  128  may or may not have the multiple via holes  132 . Therefore, the first planar conductive surface may be continuously conductive without any insulating areas, or the first planar conductive surface may be continuously conductive without any insulating areas except for the multiple via holes  132 . Each of the multiple via holes  132  may be conductively plated or may include a conductive element traversing through the hole. 
     The first end  14  of the loading plate dielectric layer  130  may extend beyond the first end  14  of the first loading plate conductive layer  128 , beyond the first end  14  of the second loading plate conductive layer  134 , or both. The second end  16  of the loading plate dielectric layer  130  may extend beyond the second end  16  of the first loading plate conductive layer  128 , beyond the second end  16  of the second loading plate conductive layer  134 , or both. One edge of the loading plate dielectric layer  130  may extend beyond the corresponding edge of the first loading plate conductive layer  128 , beyond the corresponding edge of the second loading plate conductive layer  134 , or both. An opposite edge of the loading plate dielectric layer  130  may extend beyond the corresponding opposite edge of the first loading plate conductive layer  128 , beyond the corresponding opposite edge of the second loading plate conductive layer  134 , or both. 
     In addition to the multiple via holes  132  electrically connecting the first loading plate conductive layer  128  to the second loading plate conductive layer  134 , conductive layers on the first end  14  of the loading plate dielectric layer  130 , on the second end  16  of the loading plate dielectric layer  130 , on one edge of the loading plate dielectric layer  130 , on the opposite edge of the loading plate dielectric layer  130 , or any combination thereof, may electrically connect the first loading plate conductive layer  128  to the second loading plate conductive layer  134 . 
       FIG. 23  shows a planar structure  136 , which may be used in the RF antenna structure  10  illustrated in  FIG. 10  according to a first embodiment of the planar structure  136 . The planar structure  136  may be formed using a second metallic sheet  137 , such as a stamped metal sheet. The second metallic sheet  137  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof, and the second metallic sheet  137  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof. 
       FIG. 24  shows the planar structure  136 , which may be used in the RF antenna structure  10  illustrated in  FIG. 10  according to a second embodiment of the planar structure  136 . The planar structure  136  may be formed using a first planar structure conductive layer  138  and a planar structure dielectric layer  140 . The first planar structure conductive layer  138  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure dielectric layer  140  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first planar structure conductive layer  138  is about parallel to the planar structure dielectric layer  140 . The first planar structure conductive layer  138  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . PCB material may provide the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . 
     The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof, and the first planar structure conductive layer  138  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof. 
       FIG. 25  shows the planar structure  136 , which may be used in the RF antenna structure  10  illustrated in  FIG. 10  according to a third embodiment of the planar structure  136 . The planar structure  136  may be formed using the first planar structure conductive layer  138 , a second planar structure conductive layer  142 , and the planar structure dielectric layer  140  between the first planar structure conductive layer  138  and the second planar structure conductive layer  142 . The first planar structure conductive layer  138  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The second planar structure conductive layer  142  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure dielectric layer  140  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first planar structure conductive layer  138  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . Similarly, the second planar structure conductive layer  142  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the second planar structure conductive layer  142  and the planar structure dielectric layer  140 . PCB material may provide the first planar structure conductive layer  138 , the second planar structure conductive layer  142 , and the planar structure dielectric layer  140 . 
     The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof, and the first planar structure conductive layer  138  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , or any combination thereof. 
       FIG. 26  shows the planar structure  136 , which may be used in the dual band RF antenna structure  50  illustrated in  FIG. 14  according to a fourth embodiment of the planar structure  136 . The planar structure  136  may be formed using the second metallic sheet  137 , such as a stamped metal sheet. The second metallic sheet  137  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof, and the second metallic sheet  137  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof. 
       FIG. 27  shows the planar structure  136 , which may be used in the dual band RF antenna structure  50  illustrated in  FIG. 14  according to a fifth embodiment of the planar structure  136 . The planar structure  136  may be formed using the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . The first planar structure conductive layer  138  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure dielectric layer  140  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first planar structure conductive layer  138  is about parallel to the planar structure dielectric layer  140 . The first planar structure conductive layer  138  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . PCB material may provide the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . 
     The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof, and the first planar structure conductive layer  138  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof. 
       FIG. 28  shows the planar structure  136 , which may be used in the dual band RF antenna structure  50  illustrated in  FIG. 14  according to a sixth embodiment of the planar structure  136 . The planar structure  136  may be formed using the first planar structure conductive layer  138 , the second planar structure conductive layer  142 , and the planar structure dielectric layer  140  between the first planar structure conductive layer  138  and the second planar structure conductive layer  142 . The first planar structure conductive layer  138  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The second planar structure conductive layer  142  may include copper, brass, silver, gold, one or more other metals, or any combination thereof. The planar structure dielectric layer  140  may include glass epoxy, one or more other dielectric materials, or any combination thereof. The first planar structure conductive layer  138  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the first planar structure conductive layer  138  and the planar structure dielectric layer  140 . Similarly, the second planar structure conductive layer  142  may be bonded directly to the planar structure dielectric layer  140 , or there may be one or more intervening layers between the second planar structure conductive layer  142  and the planar structure dielectric layer  140 . PCB material may provide the first planar structure conductive layer  138 , the second planar structure conductive layer  142 , and the planar structure dielectric layer  140 . 
     The planar structure  136  may include the first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof, and the first planar structure conductive layer  138  provides the corresponding first conductive matching element  22 , the first conductive element  30 , the second conductive matching element  36 , the second conductive element  68 , the third conductive element  76 , the first dual band conductive element  52 , the second dual band conductive element  84 , or any combination thereof. 
     A first exemplary embodiment of the RF antenna structure  10  is illustrated in  FIG. 17 , such that a magnitude of the first length  94  is equal to about 23 millimeters; a magnitude of the second length  98  is equal to about 8 millimeters, a magnitude of the third length  102  is equal to about 7 millimeters, a magnitude of the fourth length  106  is equal to about 8 millimeters, a magnitude of the fifth length  110  is equal to about 16 millimeters, a magnitude of the sixth length  114  is equal to about 2 millimeters, a magnitude of the first width  96  is equal to about 8 millimeters, a magnitude of the second width  100  is equal to about 5 millimeters, a magnitude of the third width  104  is equal to about 2 millimeters, a magnitude of the fourth width  108  is equal to about 2 millimeters, a magnitude of the fifth width  112  is equal to about 2 millimeters, and a magnitude of the sixth width  116  is equal to about 2 millimeters. 
     A second exemplary embodiment of the RF antenna structure  10  is illustrated in  FIG. 17 , such that a magnitude of the first length  94  is equal to about 17 millimeters; a magnitude of the second length  98  is equal to about 5 millimeters, a magnitude of the third length  102  is equal to about 5.5 millimeters, a magnitude of the fourth length  106  is equal to about 2 millimeters, a magnitude of the fifth length  110  is equal to about 11 millimeters, a magnitude of the sixth length  114  is equal to about 2 millimeters, a magnitude of the first width  96  is equal to about 7 millimeters, a magnitude of the second width  100  is equal to about 4 millimeters, a magnitude of the third width  104  is equal to about 2 millimeters, a magnitude of the fourth width  108  is equal to about 2 millimeters, a magnitude of the fifth width  112  is equal to about 2 millimeters, and a magnitude of the sixth width  116  is equal to about 2 millimeters. The loading plate  12  is illustrated in  FIG. 22 , such that the loading plate dielectric layer  130  is about 1.6 millimeters thick and is formed using Flame Retardant 4 (FR4) PCB material. The first and the second ends  14 ,  16  of the loading plate dielectric layer  130  may extend beyond the first and the second ends  14 ,  16  of the first loading plate conductive layer  128  and the second loading plate conductive layer  134 . In addition to the multiple via holes  132  electrically connecting the first loading plate conductive layer  128  to the second loading plate conductive layer  134 , conductive layers on the edges of the loading plate dielectric layer  130  may electrically connect the first loading plate conductive layer  128  to the second loading plate conductive layer  134 . The planar structure  136  is illustrated in  FIG. 24 , such that the planar structure dielectric layer  140  is about 1.6 millimeters thick and is formed using the FR4 PCB material. 
     A first exemplary embodiment of the dual band RF antenna structure  50  is illustrated in  FIG. 18 , such that a magnitude of the first length  94  is equal to about 29.5 millimeters, a magnitude of the second length  98  is equal to about 6.5 millimeters, a magnitude of the third length  102  is equal to about 6.5 millimeters, a magnitude of the fourth length  106  is equal to about 10.5 millimeters, a magnitude of the fifth length  110  is equal to about 16 millimeters, a magnitude of the sixth length  114  is equal to about 2.5 millimeters, a magnitude of the first dual band length  118  is equal to about 4.5 millimeters, a magnitude of the second dual band length  122  is equal to about 7.5 millimeters, a magnitude of the first width  96  is equal to about 7 millimeters, a magnitude of the second width  100  is equal to about 4 millimeters, a magnitude of the third width  104  is equal to about 2 millimeters, a magnitude of the fourth width  108  is equal to about 2 millimeters, a magnitude of the fifth width  112  is equal to about 2 millimeters, a magnitude of the sixth width  116  is equal to about 2 millimeters, a magnitude of the first dual band width  120  is equal to about 2 millimeters, and a magnitude of the second dual band width  124  is equal to about 2 millimeters. 
     A second exemplary embodiment of the dual band RE antenna structure  50  is illustrated in  FIG. 18 , such that a magnitude of the first length  94  is equal to about 23 millimeters, a magnitude of the second length  98  is equal to about 5.5 millimeters, a magnitude of the third length  102  is equal to about 5.5 millimeters, a magnitude of the fourth length  106  is equal to about 4.5 millimeters, a magnitude of the fifth length  110  is equal to about 10 millimeters, a magnitude of the sixth length  114  is equal to about 2.5 millimeters, a magnitude of the first dual band length  118  is equal to about 4.5 millimeters, a magnitude of the second dual band length  122  is equal to about 7 millimeters, a magnitude of the first width  96  is equal to about 7 millimeters, a magnitude of the second width  100  is equal to about 4 millimeters, a magnitude of the third width  104  is equal to about 2 millimeters, a magnitude of the fourth width  108  is equal to about 2 millimeters, a magnitude of the fifth width  112  is equal to about 2 millimeters, a magnitude of the sixth width  116  is equal to about 2 millimeters, a magnitude of the first dual band width  120  is equal to about 2 millimeters, a magnitude of the second dual band width  124  is equal to about 2 millimeters. The loading plate  12  is illustrated in  FIG. 22 , such that the loading plate dielectric layer  130  is about 1.6 millimeters thick and is formed using the FR4 PCB material. The first and the second ends  14 ,  16  of the loading plate dielectric layer  130  may extend beyond the first and the second ends  14 ,  16  of the first loading plate conductive layer  128  and the second loading plate conductive layer  134 . In addition to the multiple via holes  132  electrically connecting the first loading plate conductive layer  128  to the second loading plate conductive layer  134 , conductive layers on the edges of the loading plate dielectric layer  130  may electrically connect the first loading plate conductive layer  128  to the second loading plate conductive layer  134 . The planar structure  136  is illustrated in  FIG. 27 , such that the planar structure dielectric layer  140  is about 1.6 millimeters thick and is formed using the FR4 PCB material. 
     An application example of the RF antenna structure  10  or the dual band RF antenna structure  50  is their use to form an RF antenna  144 , which is included in a wireless local area network (WLAN) access point  146 , the basic architecture of which is represented in  FIG. 29 . The WLAN access point  146  may include a receiver front end  148 , a radio frequency transmitter section  150 , the RF antenna  144 , a duplexer or switch  152 , a baseband processor  154 , a control system  156 , and a frequency synthesizer  158 . The receiver front end  148  receives information bearing RF signals from one or more end users (not shown). A low noise amplifier (LNA)  160  amplifies the signal. A filter circuit  162  minimizes broadband interference in the received signal, while down conversion and digitization circuitry  164  down converts 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  148  typically uses one or more mixing frequencies generated by the frequency synthesizer  158 . The baseband processor  154  processes the digitized received signal to extract information or data bits conveyed in the received signal. This processing typically comprises demodulation, decoding, and error correction operations. As such, the baseband processor  154  is generally implemented in one or more digital signal processors (DSPs). 
     On the transmit side, the baseband processor  154  receives digitized data, which may represent voice, data, or control information, from the control system  156 , which the baseband processor  154  encodes for transmission to the end users. The encoded data is output to the transmitter  150 , where it is used by a modulator  166  to modulate a carrier signal that is at a desired transmit frequency. Power amplifier circuitry  168  amplifies the modulated carrier signal to a level appropriate for transmission, and delivers the amplified and modulated carrier signal to the antenna  144  through the duplexer or switch  152 . 
     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.

Metadata:
Filing Date: 20110912
Publication Date: 20130409
Grant Date: 20130409
Priority Date: 20080502
Inventors: KITCHENER DEAN
URQUHART ANDREW
Assignee: APPLE INC
CPC Classifications: [{"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q9/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/36", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/0442", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q1/48", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 41254807