Dual Polarized Slot Antenna
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*Dual Polarized Slot Antenna Booster
*A Dual-polarized Square-ring Slot Antenna For Uwb Imaging And Radar Applications
*Dual-polarization Slot-coupled Printed Antennas Fed By Stripline
This patent application is the divisional of pending U.S. application Ser. No. 13/839,839, filed on Mar. 15, 2013, that claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/615,006, filed Mar. 23, 2012, the disclosure of which is incorporated by reference herein.
Layered dual frequency antenna array: 1997-08-26: Uher et al. 343/700MS: 5619216: Dual polarization common aperture array formed by waveguide-fed, planar slot array and linear short backfire array: 1997-04-08: Park: 343/771: 5596336: Low profile TEM mode slot array antenna: 1997-01-21: Liu: 343/770: 5581266: Printed-circuit crossed-slot antenna. For multi-band linearly polarization systems, a dual band antenna with arc-shaped slot operating at 1.6 GHz and 2.05-2.29 GHz is reported in. The subtending angle of the slot can be adjusted for operating frequency tuning and band spacing ratio. Horizontally polarized and dual polarized antennas are described herein. In some examples, a horizontally polarized and dual polarized antenna may be mounted or operated with the physical vertical axis of the antenna being substantially perpendicular to a plane defined by the surface of the earth, and emanate an electric field that is parallel. This paper investigates an annular-ring slot antenna loaded by reactive components to generate dual-band dual-sense circular polarization. The antenna consists of two microstrip-line-fed and concentric annular-ring slots.
Wireless communication has become an integral part of modern life in personal and professional realms. It is used for voice, data, and other types of communication. Wireless communication is also used in military and emergency response applications. Communications that are made wirelessly rely on the electromagnetic spectrum as the carrier medium. Unfortunately, the electromagnetic spectrum is a limited resource.
Although the electromagnetic spectrum spans a wide range of frequencies, only certain frequency bands are applicable for certain uses due to their physical nature and/or due to governmental restrictions. Moreover, the use of the electromagnetic spectrum for wireless communications is so pervasive that many, if not most, frequency bands are already over-crowded. This crowding may cause interference between and among different wireless communication systems.
Such interference jeopardizes successful transmission and reception of wireless communications that are important to many different aspects of modern society. Wireless communication interference can necessitate retransmissions, cause the use of ever greater power outlays, or even completely prevent some wireless communications. Consequently, there is a need to wirelessly communicate with reduced electromagnetic interference that may hinder the successful communication of information.
An antenna having a single aperture may introduce a significant disparity in the field strength and consequently a difference in the surface current density along the opposite surface from the aperture of the antenna. This results in a difference in the radiation intensity and, hence, a difference in the far field radiation pattern in the horizontal plane giving rise to maximum to minimum variance in the omni-directional (circular) pattern of 2.5 dB to 4 dB.
Example embodiments of antennas having a multi-slot aperture that reduce the variation in the far field omni-directional pattern are described herein.
While described individually, the foregoing embodiments are not mutually exclusive and any number of embodiments may be present in a given implementation. Moreover, other antennas, systems, apparatuses, methods, devices, arrangements, mechanisms, approaches, etc. are described herein.
The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items.
FIG. 1 illustrates an exemplary conducting tube having two slots.
FIG. 2 illustrates electric fields of an exemplary conducting tube having two slots.
FIGS. 3A and 3B illustrate an exemplary two-slot antenna construction with two rectangular U-channels affixed to a supporting structure utilizing Printed Circuit Board (PCB) techniques.
FIGS. 4A and 4B illustrate one of the U-channel halves and a PCB support structure of an exemplary antenna construction.
FIGS. 5A and 5B illustrate PCB approaches utilizing a modified microstrip line configuration used for a supporting structure.
FIGS. 6A and 6B illustrate a support structure approach utilizing a modified coplanar waveguide (CPW).
FIG. 7A illustrates a perspective view of an exemplary assembled antenna.
FIG. 7B illustrates a perspective view of a PCB support structure showing feed lines, a feed pin, a pin fastener, a short section of a coaxial cable and four location tabs.
FIG. 7C illustrates an end view of a two-slot antenna.
FIG. 8A illustrates a perspective view of an antenna.
FIG. 8B illustrates a perspective view of a square cross-section inner conductor showing feed pins and a coaxial cable.
FIG. 8C illustrates an end view showing relationships of feed pins to each other and to slots.
FIGS. 9A and 9B illustrate two exemplary four-slot (or quadru-slot) embodiments utilizing a circular and square, respectively, cross-sectional tube for the antenna body.
FIG. 10A illustrates a perspective view of a support structure with conducting strips.
FIG. 10B illustrates two components that make up a support structure separated to show axial slits cut into a laminate.
FIG. 10C illustrates a perspective view of a support structure without conducting strips.
FIG. 11 illustrates exemplary three-slot (or tri-slot) antenna embodiments utilizing a circular and triangular cross-sectional tube, respectively, for the antenna body.
FIGS. 12A and 12B illustrate a circular rod configuration and a thin plate configuration, respectively.
FIGS. 13A and 13B illustrate an input end view and a perspective view of feed plates without feed plate supports.
FIG. 14 illustrates angular coordinates for a 3-dimensional coordinate system.
FIG. 15 illustrates a multi-slot antenna elevation far field pattern.
FIG. 16 illustrates a multi-slot antenna azimuth far field pattern.
FIGS. 17A and 17B illustrate a perspective view and an end view of an example high gain two-slot antenna.
FIGS. 18A-18D illustrate a microstrip series feed support structure.
FIGS. 19A-19D illustrate a modified CPW support structure.
FIGS. 20A-20C illustrate an exemplary high gain antenna utilizing a four feed set configuration energized by a coaxial line.
FIG. 21 illustrates a simulated typical elevation far field radiation pattern for the high gain two-slot antenna.
FIG. 22 illustrates a simulated typical azimuth far field radiation pattern for the high gain two-slot antenna.
FIG. 23 illustrates an embodiment of a common aperture antenna utilizing a two-slot horizontal polarized λ/2 antenna and a uniquely configured dipole antenna.
FIG. 24 illustrates an embodiment of a duple-coaxial line construction.
FIG. 25 illustrates an in-line duple-coaxial line.
FIG. 26 illustrates a common aperture dual polarized antenna with a feed technique using two independent coaxial lines to feed two orthogonal polarized antennae.
FIG. 27 illustrates common aperture antenna far field elevation patterns for horizontal polarization.
FIG. 28 illustrates common aperture antenna far field elevation patterns for vertical polarization.
FIG. 29 illustrates common aperture antenna far field azimuth patterns for horizontal polarization.
FIG. 30 illustrates common aperture antenna far field azimuth patterns for vertical polarization.
FIG. 31 illustrates three embodiments of two common aperture dual polarized antennae collinearly arrayed.
An antenna operated such that the electric field emanating from the antenna is parallel to a plane defined by the surface of the earth is said to be horizontally polarized. In example embodiments, this disclosure describes a horizontally polarized antenna that may be mounted or operated with the physical vertical axis of the antenna (e.g., a vertical longitudinal axis) being substantially perpendicular to a plane defined by the surface of the earth, and still emanate an electric field that is parallel to the surface of the earth. Use of horizontal polarization may improve communications reliability by reducing interference from predominantly vertically polarized signals in overlapping and adjacent frequency bands.
Compact horizontally polarized antennas have not proliferated in the marketplace. Most horizontally polarized antennas that have been developed and marketed are relatively large or are aesthetically obtrusive. Until recently, no slim horizontally polarized antenna having physical similarities to a vertical dipole has been commercially available. U.S. Pat. No. 7,948,440, issued on 24 May 2011, by inventors Royden M. Honda and Raymond R. Johnson, entitled “Horizontal Polarized Omni-Directional Antenna” describes an omni-directional horizontally polarized antenna. U.S. patent application Ser. No. 12/576,207 by inventors Royden M. Honda and Robert J. Conley entitled “Spiraling Surface Antenna” also describes an omni-directional polarized antenna. Both U.S. Pat. No. 7,948,440 and U.S. patent application Ser. No. 12/576,207 are herein incorporated by reference in their entirety. The present application discloses various embodiments of a subsequently developed omni-directional antenna that has a number of additional features discussed below.
Exemplary embodiments of a two-slot antenna having cross sections that may be substantially square, substantially rectangular or substantially circular are described herein. However, other cross sections, for example, substantially polygonal or substantially elliptical cross sections, may also be employed.
Poker tournament leaks sites. Although this disclosure discusses various embodiments of a two-slot tubular antenna, the concept may be extended into a multi-slot antenna, whereby alternate walls or every wall of a substantially polygonal structure may have a slot fashioned into it. As an example of a substantially elliptical tubular structure, the longitudinal axes of the slots may generally be parallel to the axis of the tube and spaced along the surface judiciously and excited appropriately to maintain correct relative amplitude and relative electrical phase from one slot to an adjacent slot. This allows the resultant vector sum of the emanating electric field to produce a well-behaved far field generally circular (omni-directional) pattern in the plane normal to the axis of the antenna.
Well-behaved, in the context of this disclosure, is defined to mean that the ripple (variation from crest to trough) in the generally circular pattern is less than or equal to 3 dB, with the trough angular spacing in the generally circular pattern occurring approximately 360°/n around the antenna axis, where n=the number of slots. As an example, a well-behaved far field generally circular (omni-directional) pattern in the plane normal to the axis of the antenna yields a maximum to minimum gain variation in omni-directionality of the antenna of less than or equal to 3 decibels (dB). The same relationship of the multiple slots in a substantially polygonal structure to electrical phasing as discussed previously is to be maintained. For example, in embodiments of antennas having a square, a rectangle or a circular cross section with four slots, each slot may be fashioned into opposite sides of the structure. From the end view of the cross section, the slots may be physically oriented 90° apart around the antenna axis. In this example, the relative electrical phase relationship of adjacent slots may be 90° to each other with increasing or decreasing phase sum in the clockwise (CW) or counter clockwise (CCW) direction as observed from the end view of the structure. As an example, one slot may be selected as reference with a relative phase of 0°, the adjacent slot in the CW direction may be a relative phase of 90°, the next slot may be a relative phase of 180°, and the fourth slot may be a relative phase of 270°. Hence, the total electrical phase when the clockwise circuit is traversed from the reference slot back to the reference slot may be 360°.
As an example, FIG. 9 illustrates two embodiments of a four-slot (quadru-slot) antenna configuration. Embodiments of a three-slot (tri-slot) antenna configuration are illustrated in FIG. 11.
FIG. 1 illustrates an exemplary conducting tube 100 configured to have two slots (slot A and slot B) fashioned into opposite walls of a square or rectangular conducting tube that requires two feeds. One feed may be at one of the slots (e.g., slot A) with another feed at the other slot (e.g., slot B). One feed may introduce a positive charge along an edge of slot A, and the other feed may introduce a negative charge along an edge of slot B, where both slot edges may be located on the same conducting tube half. Thus, in exemplary conducting tube 100, a surface current flow in one direction may be induced along the surface of the conducting tube half from one edge of slot A to an edge of slot B. The other edge of slots A and B may be negatively and positively charged, respectively. These slot edges may also induce current flow along their common conducting tube half. This surface current may flow in the same direction as the current induced on the previously described conducting surface. The continuous flow of the surface currents around the conducting tube is disrupted at the slots (i.e., Slot A and B). However, at a slot, a potential difference is created by the negative and positive charges introduced by the feed, producing electric fields across the slot. Exemplary conducting tube 100 is shown to have a slot length L that coincides with the axis (i.e., longitudinal axis) of conducting tube 100 and a slot width W, such that L>>W, as described in greater detail herein. Conducting tube 100 may be configured as part of an antenna having a longitudinal axis that is collinear with slot length L. As an example, when the longitudinal axis is substantially perpendicular to a plane defined by the surface of the earth, the longitudinal axis is considered collinear with a vertical longitudinal axis, and the antenna is configured to transceiver (e.g., receive and/or transmit) a horizontally polarized omni-directional signal.
FIG. 2 illustrates an exemplary environment 200 where electric fields are represented by vectors. In exemplary environment 200, an electric field vector may be associated with a first slot (e.g., Slot A of FIG. 1) denoted as E. The other feed may induce a potential difference equal to but 180° out of phase to that of the first slot, generating E-field vectors opposite in direction to the electric field vectors of the first slot. If the vector of the first slot is E, then the second slot (e.g., Slot B of FIG. 1) vector is denoted as −E.
As an example, continuity of the surface current flow in the conducting surface is sustained at the slot by the electric fields across the slot. The generated electric field vectors do not exist within the conducting medium. The field vectors travels outward, away from the slot, while its end points maintain contact with the conducting surfaces until the tip of the arrow head of one set of vectors meets the tail end of the arrow of the other set of vectors. These vectors join together to form circular rings of closed vectors, which continues to emanate outward from the antenna forming the far field omni-directional pattern of the two-slot antenna, as illustrated in FIG. 2.
The exemplary embodiments in the following discussion use specific cross sectional shapes in describing the antenna structure. However, as mentioned in the Electrical Considerations section above, the cross sectional shapes of the two-slot antenna are not necessarily confined to the specific shapes utilized in the following examples. Dimensions for the two-slot antenna using a substantially circular, substantially square or a substantially rectangular cross section are given in wavelength of the design frequency. The antenna is physically scalable from a given design frequency to other designated frequencies.
The antenna conducting surfaces may be fabricated from available conductive materials such as metal tubing, U-channels, rods or sheet metal. Alternate fabrication techniques may utilize molding, forming, and extrusion type process for metals, plastics, ceramics or other materials. When non-conductive materials are utilized, surfaces may be made to exhibit conductive properties through various techniques such as metal plating, infusion of conducting materials etc.
It is to be understood for the purposes of this disclosure that reference to wavelength (λ) implies a wavelength within a medium, the medium having a permittivity of 1.0 (free space) or greater or smaller as in the case of metamaterials including those with negative permittivity. For example, a permittivity greater than 1.0 alters the velocity of propagation of an electromagnetic wave within the mediumrelative to free space, resulting in a wavelength that is shorter in non-free space media. The expression for a wavelength within a medium is as follows:
λ=λo/(∈r)1/2
where: λ=wavelength in the mediumλo=free space wavelength∈r=permittivity of the medium
Generally, the diameter and diagonal is approximately 0.117λ, for the cylindrical and the rectangular tube, respectively, and the structure height along the structure’s longitudinal axis is approximately 0.54λ (e.g., L1 of FIG. 8) to accommodate the slot which is substantially λ/2 (e.g., L of FIG. 1 or L2 of FIG. 8) in height. The slot width (e.g., W of FIG. 1) may be approximately 0.002λ, to approximately 0.026λ. The tubes may utilize conducting or non-conducting or combinations of both material types for end caps to seal the ends of the tubes.
Also it is to be understood for the purposes of this disclosure that reference to the terms “couple” or “coupling” are used in the following discussion to refer to energy transfer from one conductor to another conductor or from one wave guide to another wave guide, as including a physical connection or a nonphysical connection. A nonphysical connection may include inductive and/or capacitive methods.
Various embodiments are disclosed herein to facilitate the manufacture and assembly of the two-slot antenna. As an example, the antenna utilizes a supporting structure to hold two halves of either semi-circular troughs or rectangular or square U-channels. This design may use tubes described herein a
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*Dual Polarized Slot Antenna Booster
*A Dual-polarized Square-ring Slot Antenna For Uwb Imaging And Radar Applications
*Dual-polarization Slot-coupled Printed Antennas Fed By Stripline
This patent application is the divisional of pending U.S. application Ser. No. 13/839,839, filed on Mar. 15, 2013, that claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/615,006, filed Mar. 23, 2012, the disclosure of which is incorporated by reference herein.
Layered dual frequency antenna array: 1997-08-26: Uher et al. 343/700MS: 5619216: Dual polarization common aperture array formed by waveguide-fed, planar slot array and linear short backfire array: 1997-04-08: Park: 343/771: 5596336: Low profile TEM mode slot array antenna: 1997-01-21: Liu: 343/770: 5581266: Printed-circuit crossed-slot antenna. For multi-band linearly polarization systems, a dual band antenna with arc-shaped slot operating at 1.6 GHz and 2.05-2.29 GHz is reported in. The subtending angle of the slot can be adjusted for operating frequency tuning and band spacing ratio. Horizontally polarized and dual polarized antennas are described herein. In some examples, a horizontally polarized and dual polarized antenna may be mounted or operated with the physical vertical axis of the antenna being substantially perpendicular to a plane defined by the surface of the earth, and emanate an electric field that is parallel. This paper investigates an annular-ring slot antenna loaded by reactive components to generate dual-band dual-sense circular polarization. The antenna consists of two microstrip-line-fed and concentric annular-ring slots.
Wireless communication has become an integral part of modern life in personal and professional realms. It is used for voice, data, and other types of communication. Wireless communication is also used in military and emergency response applications. Communications that are made wirelessly rely on the electromagnetic spectrum as the carrier medium. Unfortunately, the electromagnetic spectrum is a limited resource.
Although the electromagnetic spectrum spans a wide range of frequencies, only certain frequency bands are applicable for certain uses due to their physical nature and/or due to governmental restrictions. Moreover, the use of the electromagnetic spectrum for wireless communications is so pervasive that many, if not most, frequency bands are already over-crowded. This crowding may cause interference between and among different wireless communication systems.
Such interference jeopardizes successful transmission and reception of wireless communications that are important to many different aspects of modern society. Wireless communication interference can necessitate retransmissions, cause the use of ever greater power outlays, or even completely prevent some wireless communications. Consequently, there is a need to wirelessly communicate with reduced electromagnetic interference that may hinder the successful communication of information.
An antenna having a single aperture may introduce a significant disparity in the field strength and consequently a difference in the surface current density along the opposite surface from the aperture of the antenna. This results in a difference in the radiation intensity and, hence, a difference in the far field radiation pattern in the horizontal plane giving rise to maximum to minimum variance in the omni-directional (circular) pattern of 2.5 dB to 4 dB.
Example embodiments of antennas having a multi-slot aperture that reduce the variation in the far field omni-directional pattern are described herein.
While described individually, the foregoing embodiments are not mutually exclusive and any number of embodiments may be present in a given implementation. Moreover, other antennas, systems, apparatuses, methods, devices, arrangements, mechanisms, approaches, etc. are described herein.
The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items.
FIG. 1 illustrates an exemplary conducting tube having two slots.
FIG. 2 illustrates electric fields of an exemplary conducting tube having two slots.
FIGS. 3A and 3B illustrate an exemplary two-slot antenna construction with two rectangular U-channels affixed to a supporting structure utilizing Printed Circuit Board (PCB) techniques.
FIGS. 4A and 4B illustrate one of the U-channel halves and a PCB support structure of an exemplary antenna construction.
FIGS. 5A and 5B illustrate PCB approaches utilizing a modified microstrip line configuration used for a supporting structure.
FIGS. 6A and 6B illustrate a support structure approach utilizing a modified coplanar waveguide (CPW).
FIG. 7A illustrates a perspective view of an exemplary assembled antenna.
FIG. 7B illustrates a perspective view of a PCB support structure showing feed lines, a feed pin, a pin fastener, a short section of a coaxial cable and four location tabs.
FIG. 7C illustrates an end view of a two-slot antenna.
FIG. 8A illustrates a perspective view of an antenna.
FIG. 8B illustrates a perspective view of a square cross-section inner conductor showing feed pins and a coaxial cable.
FIG. 8C illustrates an end view showing relationships of feed pins to each other and to slots.
FIGS. 9A and 9B illustrate two exemplary four-slot (or quadru-slot) embodiments utilizing a circular and square, respectively, cross-sectional tube for the antenna body.
FIG. 10A illustrates a perspective view of a support structure with conducting strips.
FIG. 10B illustrates two components that make up a support structure separated to show axial slits cut into a laminate.
FIG. 10C illustrates a perspective view of a support structure without conducting strips.
FIG. 11 illustrates exemplary three-slot (or tri-slot) antenna embodiments utilizing a circular and triangular cross-sectional tube, respectively, for the antenna body.
FIGS. 12A and 12B illustrate a circular rod configuration and a thin plate configuration, respectively.
FIGS. 13A and 13B illustrate an input end view and a perspective view of feed plates without feed plate supports.
FIG. 14 illustrates angular coordinates for a 3-dimensional coordinate system.
FIG. 15 illustrates a multi-slot antenna elevation far field pattern.
FIG. 16 illustrates a multi-slot antenna azimuth far field pattern.
FIGS. 17A and 17B illustrate a perspective view and an end view of an example high gain two-slot antenna.
FIGS. 18A-18D illustrate a microstrip series feed support structure.
FIGS. 19A-19D illustrate a modified CPW support structure.
FIGS. 20A-20C illustrate an exemplary high gain antenna utilizing a four feed set configuration energized by a coaxial line.
FIG. 21 illustrates a simulated typical elevation far field radiation pattern for the high gain two-slot antenna.
FIG. 22 illustrates a simulated typical azimuth far field radiation pattern for the high gain two-slot antenna.
FIG. 23 illustrates an embodiment of a common aperture antenna utilizing a two-slot horizontal polarized λ/2 antenna and a uniquely configured dipole antenna.
FIG. 24 illustrates an embodiment of a duple-coaxial line construction.
FIG. 25 illustrates an in-line duple-coaxial line.
FIG. 26 illustrates a common aperture dual polarized antenna with a feed technique using two independent coaxial lines to feed two orthogonal polarized antennae.
FIG. 27 illustrates common aperture antenna far field elevation patterns for horizontal polarization.
FIG. 28 illustrates common aperture antenna far field elevation patterns for vertical polarization.
FIG. 29 illustrates common aperture antenna far field azimuth patterns for horizontal polarization.
FIG. 30 illustrates common aperture antenna far field azimuth patterns for vertical polarization.
FIG. 31 illustrates three embodiments of two common aperture dual polarized antennae collinearly arrayed.
An antenna operated such that the electric field emanating from the antenna is parallel to a plane defined by the surface of the earth is said to be horizontally polarized. In example embodiments, this disclosure describes a horizontally polarized antenna that may be mounted or operated with the physical vertical axis of the antenna (e.g., a vertical longitudinal axis) being substantially perpendicular to a plane defined by the surface of the earth, and still emanate an electric field that is parallel to the surface of the earth. Use of horizontal polarization may improve communications reliability by reducing interference from predominantly vertically polarized signals in overlapping and adjacent frequency bands.
Compact horizontally polarized antennas have not proliferated in the marketplace. Most horizontally polarized antennas that have been developed and marketed are relatively large or are aesthetically obtrusive. Until recently, no slim horizontally polarized antenna having physical similarities to a vertical dipole has been commercially available. U.S. Pat. No. 7,948,440, issued on 24 May 2011, by inventors Royden M. Honda and Raymond R. Johnson, entitled “Horizontal Polarized Omni-Directional Antenna” describes an omni-directional horizontally polarized antenna. U.S. patent application Ser. No. 12/576,207 by inventors Royden M. Honda and Robert J. Conley entitled “Spiraling Surface Antenna” also describes an omni-directional polarized antenna. Both U.S. Pat. No. 7,948,440 and U.S. patent application Ser. No. 12/576,207 are herein incorporated by reference in their entirety. The present application discloses various embodiments of a subsequently developed omni-directional antenna that has a number of additional features discussed below.
Exemplary embodiments of a two-slot antenna having cross sections that may be substantially square, substantially rectangular or substantially circular are described herein. However, other cross sections, for example, substantially polygonal or substantially elliptical cross sections, may also be employed.
Poker tournament leaks sites. Although this disclosure discusses various embodiments of a two-slot tubular antenna, the concept may be extended into a multi-slot antenna, whereby alternate walls or every wall of a substantially polygonal structure may have a slot fashioned into it. As an example of a substantially elliptical tubular structure, the longitudinal axes of the slots may generally be parallel to the axis of the tube and spaced along the surface judiciously and excited appropriately to maintain correct relative amplitude and relative electrical phase from one slot to an adjacent slot. This allows the resultant vector sum of the emanating electric field to produce a well-behaved far field generally circular (omni-directional) pattern in the plane normal to the axis of the antenna.
Well-behaved, in the context of this disclosure, is defined to mean that the ripple (variation from crest to trough) in the generally circular pattern is less than or equal to 3 dB, with the trough angular spacing in the generally circular pattern occurring approximately 360°/n around the antenna axis, where n=the number of slots. As an example, a well-behaved far field generally circular (omni-directional) pattern in the plane normal to the axis of the antenna yields a maximum to minimum gain variation in omni-directionality of the antenna of less than or equal to 3 decibels (dB). The same relationship of the multiple slots in a substantially polygonal structure to electrical phasing as discussed previously is to be maintained. For example, in embodiments of antennas having a square, a rectangle or a circular cross section with four slots, each slot may be fashioned into opposite sides of the structure. From the end view of the cross section, the slots may be physically oriented 90° apart around the antenna axis. In this example, the relative electrical phase relationship of adjacent slots may be 90° to each other with increasing or decreasing phase sum in the clockwise (CW) or counter clockwise (CCW) direction as observed from the end view of the structure. As an example, one slot may be selected as reference with a relative phase of 0°, the adjacent slot in the CW direction may be a relative phase of 90°, the next slot may be a relative phase of 180°, and the fourth slot may be a relative phase of 270°. Hence, the total electrical phase when the clockwise circuit is traversed from the reference slot back to the reference slot may be 360°.
As an example, FIG. 9 illustrates two embodiments of a four-slot (quadru-slot) antenna configuration. Embodiments of a three-slot (tri-slot) antenna configuration are illustrated in FIG. 11.
FIG. 1 illustrates an exemplary conducting tube 100 configured to have two slots (slot A and slot B) fashioned into opposite walls of a square or rectangular conducting tube that requires two feeds. One feed may be at one of the slots (e.g., slot A) with another feed at the other slot (e.g., slot B). One feed may introduce a positive charge along an edge of slot A, and the other feed may introduce a negative charge along an edge of slot B, where both slot edges may be located on the same conducting tube half. Thus, in exemplary conducting tube 100, a surface current flow in one direction may be induced along the surface of the conducting tube half from one edge of slot A to an edge of slot B. The other edge of slots A and B may be negatively and positively charged, respectively. These slot edges may also induce current flow along their common conducting tube half. This surface current may flow in the same direction as the current induced on the previously described conducting surface. The continuous flow of the surface currents around the conducting tube is disrupted at the slots (i.e., Slot A and B). However, at a slot, a potential difference is created by the negative and positive charges introduced by the feed, producing electric fields across the slot. Exemplary conducting tube 100 is shown to have a slot length L that coincides with the axis (i.e., longitudinal axis) of conducting tube 100 and a slot width W, such that L>>W, as described in greater detail herein. Conducting tube 100 may be configured as part of an antenna having a longitudinal axis that is collinear with slot length L. As an example, when the longitudinal axis is substantially perpendicular to a plane defined by the surface of the earth, the longitudinal axis is considered collinear with a vertical longitudinal axis, and the antenna is configured to transceiver (e.g., receive and/or transmit) a horizontally polarized omni-directional signal.
FIG. 2 illustrates an exemplary environment 200 where electric fields are represented by vectors. In exemplary environment 200, an electric field vector may be associated with a first slot (e.g., Slot A of FIG. 1) denoted as E. The other feed may induce a potential difference equal to but 180° out of phase to that of the first slot, generating E-field vectors opposite in direction to the electric field vectors of the first slot. If the vector of the first slot is E, then the second slot (e.g., Slot B of FIG. 1) vector is denoted as −E.
As an example, continuity of the surface current flow in the conducting surface is sustained at the slot by the electric fields across the slot. The generated electric field vectors do not exist within the conducting medium. The field vectors travels outward, away from the slot, while its end points maintain contact with the conducting surfaces until the tip of the arrow head of one set of vectors meets the tail end of the arrow of the other set of vectors. These vectors join together to form circular rings of closed vectors, which continues to emanate outward from the antenna forming the far field omni-directional pattern of the two-slot antenna, as illustrated in FIG. 2.
The exemplary embodiments in the following discussion use specific cross sectional shapes in describing the antenna structure. However, as mentioned in the Electrical Considerations section above, the cross sectional shapes of the two-slot antenna are not necessarily confined to the specific shapes utilized in the following examples. Dimensions for the two-slot antenna using a substantially circular, substantially square or a substantially rectangular cross section are given in wavelength of the design frequency. The antenna is physically scalable from a given design frequency to other designated frequencies.
The antenna conducting surfaces may be fabricated from available conductive materials such as metal tubing, U-channels, rods or sheet metal. Alternate fabrication techniques may utilize molding, forming, and extrusion type process for metals, plastics, ceramics or other materials. When non-conductive materials are utilized, surfaces may be made to exhibit conductive properties through various techniques such as metal plating, infusion of conducting materials etc.
It is to be understood for the purposes of this disclosure that reference to wavelength (λ) implies a wavelength within a medium, the medium having a permittivity of 1.0 (free space) or greater or smaller as in the case of metamaterials including those with negative permittivity. For example, a permittivity greater than 1.0 alters the velocity of propagation of an electromagnetic wave within the mediumrelative to free space, resulting in a wavelength that is shorter in non-free space media. The expression for a wavelength within a medium is as follows:
λ=λo/(∈r)1/2
where: λ=wavelength in the mediumλo=free space wavelength∈r=permittivity of the medium
Generally, the diameter and diagonal is approximately 0.117λ, for the cylindrical and the rectangular tube, respectively, and the structure height along the structure’s longitudinal axis is approximately 0.54λ (e.g., L1 of FIG. 8) to accommodate the slot which is substantially λ/2 (e.g., L of FIG. 1 or L2 of FIG. 8) in height. The slot width (e.g., W of FIG. 1) may be approximately 0.002λ, to approximately 0.026λ. The tubes may utilize conducting or non-conducting or combinations of both material types for end caps to seal the ends of the tubes.
Also it is to be understood for the purposes of this disclosure that reference to the terms “couple” or “coupling” are used in the following discussion to refer to energy transfer from one conductor to another conductor or from one wave guide to another wave guide, as including a physical connection or a nonphysical connection. A nonphysical connection may include inductive and/or capacitive methods.
Various embodiments are disclosed herein to facilitate the manufacture and assembly of the two-slot antenna. As an example, the antenna utilizes a supporting structure to hold two halves of either semi-circular troughs or rectangular or square U-channels. This design may use tubes described herein a
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