E-plane omni-directional antenna

[0001] This invention relates to antenna technology and, in particular, to an E-plane omni-directional antenna.

[0002] Computing devices and other similar devices implemented to send and/or receive data can be interconnected in a wired network or a wireless network to allow the data to be communicated between the devices. Wired networks, such as wide area networks (WANs) and local area networks (LANs) for example, tend to have a high bandwidth and can therefore be configured to communicate digital data at high data rates. One obvious drawback to wired networks is that the range of movement of a device is constrained since the device needs to be physically connected to the network for data exchange. For example, a user of a portable computing device will need to remain near to a wired network junction to stay connected to the wired network.

[0003] An alternative to wired networks is a wireless network that is configured to support similar data communications in a more accommodating manner. For example, the user of the portable computing device can move around within a region that is supported by the wireless network without having to be physically connected to the network. A limitation of wireless networks, however, is their relatively low bandwidth which results in a much slower exchange of data than a wired network. Wireless networks will become more popular as data exchange rates arc improved and as a coverage area supported by a wireless network is expanded.

[0004] Monopole and dipole antennas can be implemented in broadcast and communication applications. For a vertically polarized antenna, an E-plane contains an electric field vector and coincides with a vertical plane relative to the antenna. An H-plane contains a magnetic field vector and coincides with a horizontal plane relative to the antenna. The antenna radiates an omni-directional transmission pattern in the H-plane. That is, an electromagnetic field is radiated in an omni-direction pattern from the antenna in a plane that is normal (e.g., S perpendicular) to an axis of the antenna.

[0005] An antenna described as “omni-directional” implies an antenna that radiates equally in all directions. However, although some antennas are identified by their manufacturers as “omni-directional”, an actual omni-directional antenna has not been devised. For a horizontally polarized antenna, the transmission pattern in the E-plane is not truly omni-directional. That is, the electric field radiated in a plane that is perpendicular to the axis of the antenna is not a complete omni-directional transmission pattern.

[0006] A conventional horizontally polarized antenna design includes dipoles arrayed in a quadrature configuration in the same plane and excited in a phase relationship that generates an overall far-field transmission pattern that is a sum of the four dipole transmission patterns. However, the E-plane transmission pattern for a single half-wavelength dipole has a half-power beamwidth of approximately seventy-eight degrees (78°). As a result, the far-field transmission pattern has an approximate three (3) dB loss (e.g., a dip, or a null which is a region of low intensity) every forty-five degrees plus the product of ninety and n-degrees (e.g., 45°+90n°), where n=0, 1, 2, 3 in the omni plane.

[0007] Accordingly, there is a need for a high gain antenna that provides an E-plane omni-directional transmission pattern without nulls or losses that preclude complete coverage over a desired transmission region.

[0008] An E-plane omni-directional antenna is described herein.

[0009] In an implementation, an E-plane omni-directional antenna element includes five coplanar waveguide dipoles that are each configured to generate an e-field transmission. A center section of the antenna element couples the five coplanar waveguide dipoles to a radio frequency transmission signal such that the e-field transmission from each of the five coplanar waveguide dipoles are combined to form an E-plane omni-directional transmission pattern.

[0010] In another implementation, an E-plane omni-directional antenna can be implemented with one or more of the E-plane omni-directional antenna elements.

[0022] A wireless communication system may include at least one wireless routing device that is configured to communicate over a wireless communication link via an antenna assembly with at least one device implemented for communication within the wireless system. The wireless communication system can be implemented to communicate with multiple devices, such as portable computers, computing devices, and any other type of electronic and communication device that can be configured for wireless communication. Further, the multiple devices can be configured to communicate with one another within the wireless communication system. The wireless communication system can be implemented as a wireless local area network (WLAN), a wireless wide area network (WAN), a wireless metropolitan area network (MAN), or other similar wireless network configurations.

[0023] The following discussion is directed to an antenna assembly that may be Implemented within a wireless communication system. While the antenna assembly may be applicable or adaptable for use in other communication systems, the antenna assembly is described in the context of the following exemplary environment. An E-plane omni-directional antenna is described herein that provides an E-plane omni-directional transmission pattern (e.g., a far-field pattern) without nulls or losses that would preclude complete coverage over a desired transmission region.

[0024] FIG. 1 illustrates an exemplary E-plane omni-directional antenna element 100 that provides an E-plane omni-directional transmission pattern. The antenna element 100 has five integrated balun coplanar wave guide dipoles, such as section 102 of the antenna assembly 100. The coplanar waveguide dipole 102 is formed with adjacent slotted coplanar sectors 104 of the antenna assembly 100. For example, coplanar waveguide dipole 102 is formed by slotted coplanar sector 104(1) (also shown as an individual section of antenna element 100) positioned adjacent slotted coplanar sector 104(2).

[0025] Each slotted coplanar sector 104 is a half of two coplanar waveguide dipoles of antenna element 100 (e.g., each slotted coplanar sector 104 is positioned adjacent two other slotted coplanar sectors). For example, slotted coplanar sector 104(1) is a first half of the coplanar waveguide dipole 102 and slotted coplanar sector 104(2) is a second half of the coplanar waveguide dipole 102. Similarly, slotted coplanar sector 104(1) forms another coplanar waveguide dipole with slotted coplanar sector 104(5).

[0026] Each slotted coplanar sector 104 includes, or is otherwise formed with, a slot 106 that is a shorted coplanar waveguide channel, such as shorted coplanar waveguide channel 108 formed in the slotted coplanar sector 104(1). The slot 106 in the individual slotted coplanar sector 104(1) is the shorted coplanar waveguide channel 108 when the slotted coplanar sectors 104 are positioned to form the antenna element 100. Additionally, each slotted coplanar sector 104 forms a coplanar waveguide channel with an adjacent slotted coplanar sector 104. For example, slotted coplanar sector 104(1) forms a coplanar waveguide channel 110 between the adjacent slotted coplanar sector 104(5) when the slotted coplanar sectors 104(1) and 104(5) are positioned, or otherwise formed, adjacent each other in the antenna element 100.

[0027] The coplanar waveguide dipole 102 includes a coplanar waveguide 112 (also separately illustrated). A conductor 114 of the coplanar waveguide 112 is separated from a first ground plane 116 by a shorted coplanar waveguide channel 118. The conductor 114 is also separated from a second ground plane 120 by a coplanar waveguide channel 122. The conductor 114, ground plane 116, and shorted coplanar waveguide channel 118 are formed as part of slotted coplanar sector 104(2). The ground plane 120 is formed as part of slotted coplanar sector 104(1), and the coplanar waveguide channel 122 is formed between the adjacent slotted coplanar sectors 104(1) and 104(2).

[0028] The coplanar waveguide dipole 102 includes a balun that is formed by the shorted coplanar waveguide channel 118 of the slotted coplanar sector 104(2) and the coplanar waveguide channel 122 formed between the adjacent slotted coplanar sectors 104(1) and 104(2). A balun balances radio frequency (RF) currents between adjacent slotted coplanar sectors to provide an optimum distribution of the RF currents between the two dipole halves. For example, a balun is formed by a shorted coplanar waveguide channel 124 and a coplanar waveguide channel 126 to balance opposing currents 128 and 130 that are generated on either side of the coplanar waveguide channel 126.

[0029] The outer edge 132 of each slotted coplanar sector 104 (e.g., also the outer edge of each coplanar waveguide dipole 102) is a curve that forms an arc section of a circle and, when combined with each of the five slotted coplanar sector outer edges and/or coplanar waveguide dipole outer edges, forms the outer edge 132 of the antenna element 100. The currents (e.g., currents 128 and 130) flow along the outer edge 132 of the antenna element 100 forming a uniform current ring 134 that is interrupted by the coplanar waveguide channels (e.g., coplanar waveguide channels 110, 122, and 126, for example) which creates uniform e-fields that radiate outward from antenna element 100 to form an omni-directional transmission pattern in the far-field.

[0030] The antenna element 100 includes, or is otherwise formed with, a center conductor connection 136. Additionally, each slotted coplanar sector 104 includes, or is otherwise formed with, an outer conductor connection 138. The center conductor connection 136 can be coupled to a center conductor of a coaxial signal feed line and each outer conductor connection 138 can be coupled to an outer conductor of the coaxial signal feed line.

[0031] An impedance of antenna element 100 can be matched to the impedance of the coaxial signal feed line with the coplanar waveguide channels (e.g., coplanar waveguide channels 110, 122, and 126, for example) that are formed between each of the dipole halves (e.g., two of the slotted coplanar sectors 104). An antenna assembly formed with multiple antenna elements 100 that are configured to match the impedance of a signal feed line can be implemented with a matching network between the antenna assembly and the signal feed line.

[0032] The antenna element 100 can be etched on a copper clad laminate, stamped out of sheet metal, or manufactured with similar methods from any number of different types of materials and/or composites conducive to electromagnetic transmissions. Although antenna element 100 is shown circular, the antenna element may also be implemented as an oval, elliptical, or as a pentagonal antenna element.

[0033] FIG. 2 further illustrates a perspective view 200 of the E-plane omni-directional antenna element 100 shown in FIG. 1. The same identifiers that arc shown in FIG. 1 are used to identify the features and components of the antenna element 100 as shown in FIG. 2.

[0034] FIG. 3 illustrates a transmission pattern 300 generated with the exemplary E-plane omni-directional antenna element 100 shown in FIG. 1. As described above with reference to FIG. 1, currents (e.g., currents 128 and 130) flow along the outer edge of the antenna element 100 forming a uniform current ring that is interrupted by the coplanar waveguide channels (e.g., coplanar waveguide channels 110, 122, and 126). This creates uniform e-fields 302 that radiate outward from antenna element 100 to form the E-plane omni-directional transmission pattern 300 in the far-field.

[0035] FIG. 4 illustrates a polar logarithmic plot 400 that charts the transmission pattern 300 shown in FIG. 3. The plot illustrates that throughout three-hundred and sixty degrees (360°), the transmission pattern is omni-directional in the E-plane without any nulls or losses.

[0036] FIG. 5 illustrates an exemplary antenna assembly 500 with an exemplary transmission signal connection system 502 that couples together multiple E-plane omni-directional antenna elements 504(1) and 504(2) which can each be implemented as an exemplary E-plane omni-directional antenna element 100 as shown in FIGS. 1 and 2. Each of the antenna elements 504 have a center conductor connection 506 and multiple outer conductor connections 508.

[0037] The transmission signal connection system 502 includes a center conductive rod 510 that is coupled to an antenna element 504 at the center conductor connection 506. The transmission signal connection system also includes multiple outer conductive rods 512 that are coupled to an antenna element 504 at the outer conductor connections 508. In this example, five outer conductive rods 512 are implemented to couple the antenna elements 504 to form the antenna assembly 500. The center conductive rod 510 can be coupled to a center conductor of a coaxial signal feed line and each outer conductive rod 512 can be coupled to an outer conductor of the coaxial signal feed line.

[0038] The center conductor of a coaxial signal feed line is coupled to a center 514 of an antenna element 504 via the center conductive rod 510. The outer conductor (e.g., the shield) of the coaxial signal feed line is coupled to the slotted coplanar sectors 516 of the antenna element 504 via the outer conductive rods 512. Each slotted coplanar sector 516 is coupled to the outer conductor of the coaxial signal feed line via one outer conductive rod 512. Each additional antenna element 504 added to the antenna assembly 500 is coupled to the structure via an additional center conductive rod and multiple additional outer conductive rods.

[0039] FIG. 6 illustrates an exemplary antenna assembly 600 that includes multiple E-plane omni-directional antenna elements 602 each coupled with a transmission signal connection system 502 as shown in FIG. 5. The antenna elements 602 can each be implemented as an exemplary E-plane omni-directional antenna element 100 as shown in FIGS. 1 and 2. The multiple antenna elements 602 can be stacked to form a vertical array of the antenna elements. Each center conductive rod 510 and each of the outer conductive rods 512 can be implemented with male to female stand-offs 604, for example, that are screwed together to mechanically couple each antenna element 602 to the next. Alternatively, the outer and center conductive rods can be implemented with any type of mechanism that couples the antenna elements 602 together to form antenna assembly 600.

[0040] The antenna assembly 600, with the multiple antenna elements 602, provides a high-gain horizontally polarized omni-directional transmission pattern. Although only four antenna elements 602 are shown communicatively coupled in FIG. 6, any number of antenna elements 602 can be coupled together, either horizontally or vertically, with conductive rods 510 and 512 to increase the gain of antenna assembly 600.

[0041] FIG. 7 further illustrates the exemplary transmission signal connection system 502 shown in FIGS. 5 and 6. The connection system 502 can be implemented to replace a coaxial cable that contains two conductors which share the same axis and are concentric. A coaxial cable has one center conductor and an outside conductor formed around the center conductor and separated by an insulating layer. Similar to a coaxial cable, the connection system 502 has the center conductive rod 510 separated from the outer conductive rods 512 which are grounded returns that provide an outer shield for the center conductive rod 510. The outer conductive rods 512 serve to concentrate e-fields 700 between the center conductor (e.g., center conductive rod 510) and an outer conductor (e.g., an outer conductive rod 512) to form a transverse electromagnetic (TEM) propagated wave within a space 702 between the center conductive rod 510 and an outer conductive rod 512.

[0042] FIG. 8 illustrates an exemplary antenna system 800 that can be implemented in a wireless communications system. Antenna system 800 includes a series fed (resonant array) antenna assembly 802 that is coupled at one end to a network switch 804, such as via a wired communication cable to a local area network (LAN) switch. The network switch is communicatively coupled to a server computing device 806 that communicates data information to antenna assembly 802 for wireless transmission. The antenna assembly 802 can be implemented as antenna assembly 600 (FIG. 6) that includes multiple E-plane omni-directional antenna elements 100 (FIG. 1) each coupled with the transmission signal connection system 502 as shown in FIGS. 5-7.

[0043] The antenna assembly 802 is implemented to wirelessly communicate the data information received via the network connection 804 to any number of electronic and computing devices that are client devices configured to recognize and receive transmission signals 808 transmitted from the antenna assembly 802. Such electronic and computing devices can include desktop and portable computing devices that are configured with a wireless communication card, such as portable computing device 810, and any other type of electronic device to include a personal digital assistant (PDA), cellular phone, and similar mobile communication devices, or devices that can be configured for wireless communication connectivity. Some of the electronic and computing devices may also be connected together via a wired network and/or communication link.

[0044] FIG. 9 illustrates an exemplary antenna system 900 that can be implemented in a wireless communications system. Antenna system 900 includes a center fed antenna assembly 902 that is coupled at a center connection point to a network switch 904, such as via a wired communication cable to a local area network (LAN) switch. The network switch is communicatively coupled to a server computing device 906 that communicates data information to antenna assembly 902 for wireless transmission. The antenna assembly 902 can be implemented as antenna assembly 600 (FIG. 6) that includes multiple E-plane omni-directional antenna elements 100 (FIG. 1) each coupled with the transmission signal connection system 502 as shown in FIGS. 5-7.

[0045] The antenna assembly 902 is implemented to wirelessly communicate the data information received via the network connection 904 to any number of electronic and computing devices that arc client devices configured to recognize and receive transmission signals 908 transmitted from the antenna assembly 902. Such electronic and computing devices can include desktop and portable computing devices that are configured with a wireless communication card, such as portable computing device 910, and any other type of electronic device to include a personal digital assistant (PDA), cellular phone, and similar mobile communication devices, or devices that can be configured for wireless communication connectivity. Some of the electronic and computing devices may also be connected together via a wired network and/or communication link.

[0046] FIG. 10 illustrates a method 1000 for an E-plane omni-directional antenna. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method.

[0047] At block 1002, coplanar waveguide dipoles (of an antenna element) arc formed such that each dipole is configured to generate an e-field transmission. At block 1004, each of the coplanar waveguide dipoles are coupled to a center section to form an antenna element. The center section is configured to couple a radio frequency transmission signal to each of the coplanar waveguide dipoles such that the e-field transmissions from each of the coplanar waveguide dipoles are combined to form an E-plane omni-directional transmission pattern. For example, a center section 514 (FIG. 5) of an antenna element 504(1) has a center conductor connection 506 to couple a radio frequency transmission signal to each antenna element.

[0048] Each of the coplanar waveguide dipoles can be formed with a balun to balance radio frequency currents between adjacent coplanar waveguide dipoles and/or to balance a current in a first half of a coplanar waveguide dipole with an opposing current in a second half of the coplanar waveguide dipole. For example, antenna clement 100 (FIG. 1) includes coplanar waveguide dipoles, such as coplanar waveguide dipole 102, which have a balun to balance radio frequency currents between adjacent coplanar waveguide dipole halves, such as slotted coplanar sector 104(1) and slotted coplanar sector 104(2). A balun of the coplanar waveguide dipole 102 is formed by the shorted coplanar waveguide channel 118 and the coplanar waveguide channel 122.

[0049] The coplanar waveguide dipoles are each formed with a first slotted coplanar sector (e.g., a first half of a coplanar waveguide dipole) positioned adjacent a second slotted coplanar sector (e.g., a second half of a coplanar waveguide dipole) such that a coplanar waveguide channel is formed between the first slotted coplanar sector and the second slotted coplanar sector. For example, a first slotted coplanar sector 104(1) is positioned adjacent a second slotted coplanar sector 104(2) to form the coplanar waveguide dipole 102, and to form the coplanar waveguide channel 122 between the slotted coplanar sectors 104(1) and 104(2). The coplanar waveguide channel 122 can be implemented to have an impedance that matches an impedance of a transmission signal conductor coupled to the antenna element 100. Additionally, the slotted coplanar sector 104(2) includes a shorted coplanar waveguide channel 118 and a conductor 114 (with respect to the coplanar waveguide dipole 102).

[0050] At block 1006, one or more additional antenna elements are formed. Each additional antenna element can also be formed with coplanar waveguide dipoles that each generate an e-field transmission. The coplanar waveguide dipoles are coupled to a center section of an additional antenna element and the center section couples a radio frequency transmission signal to each of the coplanar waveguide dipoles. The e-field transmissions from each of the coplanar waveguide dipoles are combined to form an E-plane omni-directional transmission pattern. For example, an antenna element 100 (FIG. 1) includes five slotted coplanar sectors 104 that are coupled to a center section 514 (FIG. 5) of the antenna element 100 to form five coplanar waveguide dipoles, such as coplanar waveguide dipole 102 (FIG. 1). The e-field transmissions 302 (FIG. 3) from each of the coplanar waveguide dipoles (e.g., dipole 102) are combined to form the E-plane omni-directional transmission pattern 300.

[0051] At block 1008, an antenna assembly is formed with antenna elements, such as with the first antenna element (blocks 1002-1004) and with one or more of the additional antenna elements (block 1006). For example, at block 1010, the antenna element is coupled to a second antenna element with a center conductive rod configured to couple a radio frequency transmission signal to the first antenna element and to the second antenna element. For example, antenna element 504(1) (FIG. 5) is coupled to the second antenna element 504(2) with the center conductive rod 510 of the transmission signal connection system 502.

[0052] Further, at block 1012, outer conductive rods are coupled to the antenna element and to the second antenna element. The outer conductive rods shield the center conductive rod, similar to that of a coaxial cable. For example, antenna element 504(1) (FIG. 5) is coupled to the second antenna element 504(2) with the outer conductive rods 512. The outer conductive rods 512 provide a grounded return for the radio frequency transmission signal and form a transverse electromagnetic propagated wave 700 between the center conductive rod 510 and an outer conductive rod 512 as shown in FIG. 7.

[0053] At block 1014, the antenna element (or the antenna assembly) is horizontally polarized to generate the E-plane omni-directional transmission pattern. At block 1016, the antenna element (or the antenna assembly) transmits a communication signal in the E-plane omni-directional transmission pattern.

[0054] Although the invention has been described in language specific to structural features and/or methods, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as preferred forms of implementing the claimed invention.