Patent Application
20140159979
1. Field of the Invention
The present invention relates to radio communication antenna systems for wireless networks. More particularly, the invention is directed to active array antennas and related methods.
2. Description of the Prior Art and Related Background Information
Modern wireless antenna systems generally include a plurality of radiating elements that may be arranged over a ground plane defining a radiated (and received) signal beamwidth and azimuth angle. Antenna beamwidth has been conventionally defined by Half Power Beam Width (“HPBW”) of the azimuth or elevation beam relative to a bore sight of such antenna element.
Real world applications often call for an antenna radiating element with frequency bandwidth, pattern beamwidth and polarization requirements that may not be possible for conventional antenna radiating element designs to achieve due to overall mechanical constraints.
Currently, there is a demand for cellular base station antennas that produces 90 degree azimuth beamwidth at two separate frequency bands, i.e., 1.7 GHz-2.2 GHz and 700 MHz to 900 MHz. Conventional techniques to broaden the emission beamwidth include employing metallic and dielectric shrouds. These techniques are effective for broadening the beamwidth for high frequency bands (1.7 GHz-2.2 GHz); however, these techniques are either not effective or are difficult to implement at frequencies below 1 GHz. At lower frequencies (i.e., longer wavelength), the thickness of the dielectric shroud becomes impractically large to achieve the beam broadening effect. Moreover, simple thin-wall metallic shrouds becomes resonant, thus reducing the frequency bandwidth.
Accordingly, a need exists for an improved antenna element architecture which allows a dual-polarized dual-band broad beamwidth antenna.
In a first aspect the present invention provides an antenna radiating structure comprising a first patch radiating element, a second patch radiating element configured above and spaced apart from the first patch radiating element in a radiating direction, and a metallic perimeter structure, configured around the edges of the first and second patch radiating elements. The metallic perimeter structure comprises at least first, second and third wall sections extending generally in the radiating direction wherein at least two of the wall sections are angled relative to each other.
In a preferred embodiment of the antenna radiating structure the metallic perimeter structure is recessed from the top surface of the second patch radiating element. The third wall section preferably extends further in the radiating direction than the first and second wall sections. The first wall section is preferably configured with one end positioned in close proximity to the first patch radiating element and with the other end extending in the radiating direction and oriented away from the first patch radiating element. The second wall section is preferably configured with one end coupled to the first wall section and the other end oriented generally away from the radiating direction. The third wall section is preferably configured with one end coupled to the second wall and the other end oriented generally in the radiating direction. The metallic perimeter structure in cross section is preferably approximately in the shape of the letter “N” to form a continuous N-shaped wall. The first patch radiating element preferably has a planar surface with a surface normal perpendicular thereto and at least one of the wall sections has a planar surface oriented at an angle of a few degrees relative to the surface normal of the first patch radiating element. The first and third wall sections preferably each have a planar surface oriented at an angle of a few degrees relative to the surface normal of the first patch radiating element and oriented away from the first patch radiating element and the second wall section preferably has a planar surface oriented at an angle of a few degrees relative to the surface normal of the first patch radiating element and oriented toward the first patch radiating element. The planar surfaces of the first and second wall sections may be substantially parallel. The N-shaped wall comprising the metallic perimeter structure preferably has four sides around the perimeter of the first patch radiating element, wherein the length of each side of the N-shaped wall measured in the direction parallel to the surface of the patch radiating element is approximately one half of the radiation emission wavelength. The antenna radiating structure preferably further comprises a metallic partial enclosure having a cavity containing the first and second patch radiating elements and wherein the height of the N-shaped wall in the radiating direction is in the range of approximately 0.5 to approximately 0.75 of the distance of the first patch radiating element above the bottom of the cavity. In one embodiment the radiation emission is in the range of approximately 700 MHz to approximately 900 MHz.
In another aspect the present invention provides an antenna radiating structure comprising a low-frequency patch antenna structure, a high-frequency patch antenna structure, wherein the high-frequency patch antenna structure is positioned above the low frequency patch antenna structure in a radiating direction, and a metallic perimeter structure, configured around the edges of the low-frequency patch antenna structure, the metallic perimeter structure including one or more walls oriented at an angle to the radiating direction.
In a preferred embodiment of the antenna radiating structure the high-frequency patch antenna structure comprises a first high-frequency generally planar radiating element and a second high-frequency generally planar radiating element configured above and spaced apart from the first high-frequency generally planar radiating element in the radiating direction. The low-frequency patch antenna structure preferably comprises a first low-frequency generally planar radiating element and a second low-frequency generally planar radiating element configured above and spaced apart from the first low-frequency generally planar radiating element in the radiating direction. The metallic perimeter structure is preferably configured below the top surface of the second high-frequency generally planar radiating element. The metallic perimeter structure preferably comprises at least first, second and third wall sections extending generally in the radiating direction wherein at least two of the wall sections are angled relative to each other. The metallic perimeter is preferably approximately in the shape of the letter “N” to form an N-shaped wall. The antenna radiating structure preferably further comprises a metallic partial enclosure having a high-frequency cavity containing the first and second high-frequency generally planar radiating elements and a low-frequency cavity containing the first and second low-frequency generally planar radiating elements, wherein the high-frequency cavity extends partially into the low-frequency cavity. In one embodiment the radiation emission in the low-frequency band is in the range of approximately 700 MHz to approximately 900 MHz and the radiation emission in the high-frequency band is in the range of approximately 11 GHz to 2.2 GHz.
In another aspect the present invention provides an antenna array comprising a ground plane and first and second dual band antenna structures coupled to the ground plane. Each of the first and second dual band antenna structures comprises a low-frequency patch antenna structure, a high-frequency patch antenna structure positioned above the low frequency patch antenna structure in a radiating direction, and a metallic perimeter structure configured around the edges of the low-frequency patch antenna structure and including one or more walls oriented at an angle to the radiating direction. The antenna array further comprises a high band antenna structure configured on the ground plane between the first and second dual band antenna structures.
Further features and aspects of the invention are set out in the following detailed description.
It is an object of the present invention to provide dual-band antennas that emit radiation having a broad beamwidth while achieving a large frequency bandwidth of operation. The disclosed antenna structure produces broad radiation patterns with typical half power beamwidth of 90 degrees in the azimuth direction at two separate frequency bands with low cross-polarized field components.
In an embodiment of the present invention, a dual-band antenna structure comprises a high frequency patch antenna cavity stacked inline above a low frequency patch antenna cavity. Both the high frequency patch antenna and the low frequency patch antenna employ two patches in order to achieve a wide frequency bandwidth that is typically 25% of the emission frequency. In a preferred embodiment, a four-sided N-shaped metallic wall surrounds the low frequency patch antenna cavity and broadens the emission radiation beamwidth of the low frequency emission. As such, these dual band antenna structures can emit radiation with a beamwidth of approximately 90 degrees in the low frequency band of 700 MHz to 900 MHz as well as the high frequency band of 1.7 GHz to 2.2 GHz. The beamwidth of the low frequency emission is enhanced by tailoring the height of the N-shaped metallic wall and by tilting the N-shaped wall. The invention provides a low-frequency stacked patch structure which generates a broad radiation beamwidth over a large frequency bandwidth of operation
In an embodiment, the Low-Band radiator structure configured in Low-Band Cavity 130 comprises Low-Band Feeds 133, Low-Band Lower Patch 132, and Low-Band Top Patch 131. Low-Band Feeds 133 are positioned in the bottom section of Low-Band Cavity 130 and are configured to feed microwave energy into the Low-Band Cavity 130. Low-Band Feeds 133 may comprise one or more micro strip lines configured on a dielectric sheet in an embodiment. Low-Band Lower Patch 132 preferably comprises an electrically conductive plane having an aperture for radiative coupling with Low-Band RF energy fed via Low-Band Feeds 133. The aperture may be cross-shaped or otherwise configured to generate a dual polarized microwave beam. Low-Band Top Patch 131 is spaced above Low-Band Lower Patch 132 and serves as a secondary radiating patch. In an embodiment of the present invention, Low-Band Top Patch 131 is centrally disposed on a dielectric substrate; however, other configurations are also possible.
In an embodiment of the present invention, High-Band Cavity 110 is configured inline and above Low-Band Cavity 130 and comprises High-Band Feeds 114, High-Band Low Patch 112, and High-Band Top Patch 111. High-Band Feeds 113 are positioned in the bottom section of High-Band Cavity 110 and are coupled with High-Band Cable Shield 115 to feed microwave energy into the High-Band Cavity 110. High-Band Feeds 114 may comprise one or more micro strip lines configured on a dielectric sheet in an embodiment of the present invention. High-Band Lower Patch 112 comprises an electrically conductive plane for radiative coupling with High-Band RF energy fed via High-Band Feeds 114. The conductive plane may include an aperture which may be cross-shaped or otherwise configured to generate a dual polarized, microwave beam. High-Band Top Patch 111 is configured above High-Band Lower Patch 112 and serves as a secondary radiating patch. As depicted in
A metallic perimeter surrounds Low-Band Cavity 130. In an embodiment of the present invention, four N-Shaped Walls 140a-140d surround Low-Band Cavity 130. That is, viewed in the side section views of
Simulations suggest that the optimum tilt angle α is in the order of a few degrees. The optimum height of the N-Shaped Walls 140a-140d is typically between 0.5 and 0.75 of the distance from the bottom of the cavity 130 and Low-Band Top Patch 131.
In the illustrative non-limiting implementations shown, the metallic perimeter structure comprises four N-Shaped Walls 140a-140d. However, it shall be understood that many modifications including alternative number, shape, or placement of surfaces can be used as well. In the preferred illustrated embodiment, the metallic perimeter structure comprises a first section in which one end of the first section is positioned at the bottom of Low-Band Cavity 130 near Low-Band Feeds 133 with the other end of the first section positioned in a radiating direction. The surface of the first section may be flat or contoured to achieve broad beamwidth and wide bandwidth. In the illustrated embodiment, the metallic structure may comprise a first section (as described above), a second section, and a third section. One end of the second section is coupled to the end of the first section positioned in a radiating direction and the other end of the second section is positioned away from Low-Band Cavity 130. One end of the third section is coupled to the end of the second section positioned away from the Low-Band Cavity 130 and the other end of the third section is positioned in a radiating direction. The surfaces of the first, second, or third sections may be flat, contoured, or a combination of flat and contoured to achieve broad beamwidth and wide bandwidth.
The present invention has been described primarily for providing a dual-band patch antenna structure having a broadened low-frequency beamwidth. In this regard, the foregoing description of an antenna structure is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Accordingly, variants and modifications consistent with the following teachings, skill, and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain modes known for practicing the invention disclosed herewith and to enable others skilled in the art to utilize the invention in equivalent, or alternative embodiments and with various modifications considered necessary by the particular application(s) or use(s) of the present invention.
The present application claims priority under 35 USC Section 119(e) to U.S. provisional patent application Ser. No. 61/167,097 filed Apr. 6, 2009, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61167097 | Apr 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12754453 | Apr 2010 | US |
| Child | 13934953 | US |
