# Patent

## Title
Broadband dual polarization omni-directional antenna with dual conductive antenna bodies and associated methods

## Abstract

An antenna includes first and second conductive antenna bodies. The first conductive antenna body has first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points adjacent the first slot for a first polarization. The second conductive antenna body has first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points adjacent the second slot for the first polarization. The first end of the second conductive antenna body is adjacent the second end of the first conductive antenna body. Third antenna feed points are between the first and second conductive antenna bodies for a second polarization.

## Background
FIELD OF THE INVENTION
The present invention relates to the field of antennas, and more particularly, to a biconical antenna and related methods.
BACKGROUND OF THE INVENTION
Conical antennas, which include a single inverted cone over a ground plane, and biconical antennas, which include a pair of cones oriented with their apexes pointing toward each other, are used as broadband antennas for various applications.
Excitation of biconical dipoles is accomplished by imparting an electrical potential across the apex of the two opposing cones, causing a TEM mode. This mode is analogous to the TE01 mode of sectoral horns, but as the biconical dipole is a complete figure of revolution, symmetric about the cone axis, the TEM mode results. In a biconical dipole, excitation is by the dipole moment formed across the horn walls (opposing cones), so the structure is self exciting. A biconical dipole antenna is an example of an omni-directional vertically polarized antenna of relatively great bandwidth.
TE10 modeling of conventional biconical dipole structures has been proposed for the purpose of horizontal polarization and omni-directional radiation. In one instance, a circle of wire operates as a loop antenna and an excitation probe, and is placed normal to the bicone axis. For example, U.S. Pat. No. 7,453,414 discloses a biconical loop antenna that is the dual to the biconical dipole antenna, and has broadband omni-directional horizontally polarized radiation. This patent is assigned to the current assignee of the present invention, and is incorporated herein by reference in its entirety.
The cone is an example of an Euclidian geometry. Euclidian geometries often provide excellent antenna shapes. In terms of geometry, a cone is a solid figure bounded by a plane base and a surface called the lateral surface formed by the locus of all straight line segments joining the apex to the perimeter of the base. The first instance of a cone as an antenna may be unknown, but the textbook “Antennas”, 2nd edition, by John Kraus, W8JK, states that Sir Oliver Lodge constructed a biconical dipole antenna by 1897.
Even in view of the advances made in biconical antennas, there is still a need for such an antenna that supports both vertical polarization and horizontal polarization.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the present invention to provide a broadband omni-directional biconical antenna that is dual polarized.
This and other objects, features, and advantages in accordance with the present invention are provided by an antenna comprising first and second conductive antenna bodies. The first conductive antenna body has first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points adjacent the first slot for a first polarization. Similarly, the second conductive antenna body has first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points adjacent the second slot for the first polarization. The first end of the second conductive antenna body is adjacent the second end of the first conductive antenna body. Third antenna feed points are between the first and second conductive antenna bodies for a second polarization.
The first polarization associated with the first and second conductive antenna bodies may correspond to horizontal polarization. The second polarization associated with the third feed points between the first and second conductive antenna bodies may correspond to vertical polarization which is orthogonal to the horizontal polarization.
The first and second conductive antenna bodies may each be configured as a biconical omni-directional antenna with the horizontal polarization, whereas the vertical polarization is provided via the third antenna feed points between the first and second conductive antenna bodies. Collectively, the first and second conductive antenna bodies and the third antenna feed points may provide a dual polarized omni-directional antenna that advantageously operates over a wide band of frequencies.
The first and second conductive antenna bodies may each comprise first and second conical antenna elements coupled together at the medial portion. The medial portion of the first conductive antenna body may be aligned with the medial portion of the second conductive antenna body.
The antenna may further comprise a first coaxial cable having inner and outer conductors coupled to respective ones of the first antenna feed points of the first conductive antenna body, a second coaxial cable extending through the first conductive antenna body and having inner and outer conductors coupled to respective ones of the second antenna feed points of the second conductive antenna body, and a third coaxial cable extending through the first conductive antenna body and having inner and outer conductors coupled to respective ones of the third antenna feed points.
The first and second conductive antenna bodies may each comprise a continuous conductive layer. Alternatively, the first and second conductive antenna bodies may each comprise a wire structure.
Another aspect is directed to a method for making an antenna comprising forming first and second conductive antenna bodies. The first conductive antenna body has first and first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points adjacent the first slot for a first polarization. The second conductive antenna body has first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points adjacent the second slot for the first polarization. The method may further comprise positioning the first end of the second conductive antenna body adjacent the second end of the first conductive antenna body, forming third antenna feed points between the first and second conductive antenna bodies for a second polarization.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side perspective view of an antenna in accordance with the present invention with continuous conductive layers.
FIG. 2 is a side perspective view of another embodiment of the antenna illustrated in FIG. 1 with wire structures.
FIG. 3 is a side perspective view of the antenna illustrated in FIG. 1 mounted to an aircraft via an airfoil post.
FIG. 4 is a side perspective view of antenna illustrated in FIG. 1 in the radiation pattern coordinate system.
FIGS. 5 and 6 are respectively horizontal polarization radiation patterns in azimuth and elevation for the antenna illustrated in FIG. 1.
FIGS. 7 and 8 are respectively vertical polarization radiation patterns in azimuth and elevation for the antenna illustrated in FIG. 1.
FIG. 9 is a graph illustrating VSWR for horizontal polarization for the antenna illustrated in FIG. 1.
FIG. 10 is a graph illustrating VSWR for vertical polarization for the antenna illustrated in FIG. 1.
FIG. 11 is a block diagram of a communications system coupled to the antenna illustrated in FIG. 1.
FIG. 12 is a flowchart illustrating a method for making the antenna illustrated in FIG. 1.
FIG. 13 is a side perspective view of another embodiment of the antenna illustrated in FIG. 1 with dual biconical conductive antenna bodies.
FIG. 14 is a flowchart illustrating a method for making the antenna illustrated in FIG. 13.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments.
Referring initially to FIG. 1, an antenna 20 includes a conductive antenna body 30 and a conductive antenna member 60 adjacent the conductive antenna body. The conductive antenna body 30 has first and second opposing ends 32, 36 with an enlarged width medial portion 34 therebetween. One or more slots 38 extend from at least adjacent the first end 32 to at least adjacent the second end 36. First antenna feed points 40, 42 are adjacent the slot 38 for a first polarization. The conductive antenna member 60 has a planar shape and a second antenna feed point 62 for a second polarization.
The antenna 20 may be mounted such that the first polarization associated with the conductive antenna body 30 corresponds to horizontal polarization and the second polarization associated with the conductive antenna member 60 corresponds to vertical polarization. The conductive antenna body 30 is configured as a biconical omni-directional antenna with the horizontal polarization while the conductive antenna member 60 advantageously provides the vertical polarization. Of course, other mounting arrangements of the antenna 20 will change the polarization, but in general they will be orthogonal to one another. Collectively, the conductive antenna body 30 and the conductive antenna member 60 provide a dual polarized omni-directional antenna 20 that advantageously operates over a wide band of frequencies. As background, polarization refers to the orientation of radio wave electric fields. For horizontal polarization the E fields are parallel to the earth's surface, and for vertical polarization the E fields are normal to the earth's surface.
The conductive antenna body 30 illustratively includes first and second conical antenna elements 52, 54 coupled together at the medial portion 34. The medial portion 34 is also referred to as the rim or chine of the conductive antenna body 30. The conductive antenna member 60 is configured as a conductive antenna disk. The medial portion 34 of the conductive antenna body 30 is illustratively aligned with a periphery 66 of the conductive antenna disk 60.
The conductive antenna body 30 and the conductive antenna member 60 may be hollow or solid. In the illustrated embodiment of the solid configuration for the conductive antenna body 30, the slot 38 extends from a central axis of the conductive antenna body 30 to an exterior surface thereof. The conductive antenna member 60 carries a radially expanding and contracting RF current distribution for vertical polarization excitation, and may be thought of as a radial dipole form of the annular slot. The conductive antenna member 60 may be a rather modest size diameter relative to a diameter of the conductive antenna body 30 with useful results.
The conductive antenna body 30 and the conductive antenna member 60 may be made from a continuous conductive layer, such as brass sheet metal, for example. Alternatively, the conductive antenna body 30′ and/or the conductive antenna member 60′ may be made from a wire structure, as illustrated in FIG. 2.
The wire structure for the conductive antenna member 60′ may be formed by a cage construction or plurality of concentric loops 61′ that become smaller in size from the periphery 66′ to the center of the conductive antenna disk. A plurality of spaced-apart spokes 57′ extend from the center to the periphery 66′ of the conductive antenna disk 60′ and intersect the plurality of concentric loops 61′. Other configurations would also be recognized by those skilled in the art.
Similarly, the wire structure for the conductive antenna body 30′ may be formed by a plurality of concentric loops 53′, 55′ that become smaller in size from the medial portion 34′ to the first and second opposing ends 32′, 36′ of the conductive antenna body 30′. A plurality of spaced-apart spokes 51′, 55′ extend from the first and second opposing ends 32′, 36′ to the medial portion 34′ of the conductive antenna body 30 and intersect the plurality of concentric loops 53′, 55′.
For the conductive antenna body 30, a first coaxial cable 70 having inner 72 and outer conductors 74 are coupled to respective ones of the first antenna feed points 40, 42. As readily appreciated by those skilled in the art, curling current on the rim 34 of the conductive antenna body 30 creates horizontal polarization. The first coaxial cable 70 may be fed along the slot 38 to the first antenna feed points 40, 42, as illustrated in the figures. Here, the outer conductor 74 may be further coupled along a portion of the slot 38 as well as to the first antenna feed point 40.
The conductive antenna body may also be configured to have multiple slots, with a respective first coaxial cable for each slot. An advantage of multiple slots/first coaxial cables connected in parallel is that the horizontal polarization radiation pattern is more uniformly circular. The routing of the coaxial cables 70, 80 is not critical to antenna function. For instance, the coaxial cables 70, 80 may run inside or outside the antenna 20. FIG. 1 routing is one non-limiting example. Furthermore, coaxial cable baluns have not been required.
For the conductive antenna member 60, a second coaxial cable 80 having inner 82 and outer conductors 84 is fed up though a center of the conductive antenna body 30. The inner conductor 82 is coupled to the second antenna feed point 62 on the conductive antenna member 60. The outer conductor 84 is coupled to the conductive antenna body 30, i.e., at least the second conical antenna element 54.
As readily appreciated by those skilled in the art, diverging current at a cone apex of the conductive antenna body 30 creates vertical polarization. Alternatively, the second coaxial cable 80 may be fed along the slot 38 instead of along the center of the conductive antenna member 60. The curl and divergence currents are everywhere mutually orthogonal so that dual polarization is possible for the illustrated antenna 20.
The antenna 20 may be mounted to fixed or mobile platforms. When mounted to a mobile platform, such as an aircraft 90, for example, an airfoil post 92 may be used to support the conductive antenna body 30, as illustrated in FIG. 3. A radome, not shown, may also be used to enclose the antenna 20.
The conductive antenna member 60 may be configured as a folded conductive antenna member. An example of a folded conductive antenna member may be found in U.S. Pat. No. 7,864,127. This patent is assigned to the current assignee of the present invention, and is incorporated herein by reference in its entirety. The folded conductive antenna member may have a zero ohm termination resistor. Such a DC grounded folded conductive antenna member may be preferential for use on an aircraft to bleed static charges, for example.
The antenna 20 is not limited to any particular frequency of operation, as it can be linearly scaled. For instance, halving the antenna 20 size doubles antenna frequency, as readily understood by those skilled in the art. For illustration purposes, the antenna may be configured to operate at 2.44 GHz. At this frequency of operation, a diameter of the conductive antenna body 30 and the conductive antenna member 60 is about 2 inches, which corresponds to about 0.41 wavelengths (0.41λair). A thickness of the conductive antenna body 30 is about 0.5 inches, which corresponds to about 0.1 wavelengths (0.10λair). A thickness of the conductive antenna member 60 is about 0.10 inches, which corresponds to about 0.02 wavelengths (0.21λair). A thinner conductive antenna body 30 provides less wind resistance but less bandwidth. A thicker conductive antenna body 30 provides more wind resistance but more bandwidth.
The radiation pattern coordinate system 100 illustrated in FIG. 4 is used to define angles relative to the antenna 20. The different radiation patterns for the antenna 20 will now be discussed using the radiation pattern coordinate system 100.
A measured horizontal polarization radiation pattern 110 at a first resonance, i.e., 2.44 GHz, in the XY plane cut/azimuth is provided in FIG. 5. Units are a realized gain in dBi or decibels with respect to an isotropic antenna. An anechoic chamber was used for the XZ plane cut/elevation. A horizontal polarization radiation pattern 120 is provided in FIG. 6. Measured horizontal polarization realized gain was about 2.0 dBi.
The FIG. 6 radiation pattern is for a single excitation slot 38. Smoother, more circular omni-directional radiation is provided by increasing the number of excitation slots 38. A finite element analysis was executed for a 4 slot 38 conductive antenna body 30. Each slot 38 was driven with equal amplitude and equal phase, and the azimuth cut radiation pattern was circular to within +/−1 dB. The elevation cut was nearly cos2 θ, which is similar to a two petal rose of the canonical half wave dipole.
A vertical polarization radiation pattern 130 at the first resonance in the XX plane cut/azimuth is provided in FIG. 7. For the XZ, plane cut/elevation, a vertical polarization radiation pattern 140 is provided in FIG. 8. Measured vertical polarization realized gain was about 2.0 dBi. There is a minor tendency for the vertical polarization radiation pattern lobe to walk downwards with rising frequency, an effect that is commonly known to discone antennas and conical monopoles. This may be attributed to a surface wave attaching to the cone and possibly ground plane diffraction effects.
The VSWR (voltage standing wave ratio) for horizontal polarization is indicated by plot 150 on the graph illustrated in FIG. 9. The VSWR for vertical polarization is indicated by plot 160 on the graph illustrated in FIG. 10. A near perfect electrical load of 50 ohms is provided at 2.44 GHz. VSWR bandwidth for vertical polarization is greater than that for horizontal polarization because the conductive antenna body 30 and the conductive antenna member 60 together provide an expanding transmission line for the diverging and vertical polarization currents.
TABLE 1 provides a performance summary based on a prototype antenna.







TABLE 1







Performance Summary Of Antenna









Parameter
Result
Basis





Antenna requirement
Aeronautical mobile,
Specified



dual linear




polarizations



Antenna type,
Dipole by divergence
Theory


vertical polarization
of electric current



Antenna type,
Loop by curl of
Theory


horizontal
electric current



polarization




Diameter of the
2 inches (0.41λair)
Measured and


conductive antenna

calculated


body 30




Thickness of the
0.5 inches (0.1λair)
Measured and


conductive antenna

calculated


body 30




Thickness of the
0.10 inches (0.02λair)
Measured and


conductive antenna

calculated


member 60




Frequency
2441 Mhz
Calculated


Realized gain,
+2.0 dBi
Measured


horizontal




polarization




3 dB realized gain
1470 Mhz
Measured


bandwidth, horizontal




polarization




Realized Gain,
+2.0 dBi
Measured


Vertical Polarization




3 dB realized gain
Nearly high pass, >10,000 Mhz,
Measured


bandwidth, vertical
>1000



polarization
percent



Radiation pattern
Omni-directional, both
Measured



polarizations



Load impedance
50 ohms nominal
Design




criteria


VSWR, Horizontal
1.2 to 2
Measured


Polarization at




2441 MHz




2 to 1 VSWR
409 Mhz or 16 percent
Measured


Bandwidth, Horizontal




Polarization at




2441 Mhz




VSWR, Vertical
1.4 to 1
Measured


Polarization




2 to 1 VSWR
>10,000 Mhz, >1000
Measured


Bandwidth, Vertical
percent



Polarization









As background, while vertically polarized omni-directional antennas of great bandwidth are well known, horizontally polarized omni-directional antennas having similar bandwidth appear unknown. For instance, a prior art biconical dipole antenna, such as the one described in U.S. Pat. No. 2,175,252, which is an example of a vertically polarized omni-directional antenna, has a nearly high pass response with a bandwidth of 10 octaves or more. An example of a broadband horizontally polarized omni-directional antenna is the prior art Batwing Dipole Turnstile, as described in U.S. Pat. No. 2,510,290. Batwing dipole turnstile bandwidth is less than 1 octave, which is much less than that of the biconical dipole.
The antenna 20 may be coupled to a communications system, wherein the communications system includes a diversity signal processor 170 and radio frequency (RF) electronics 172, as illustrated in FIG. 11. The diversity signal processor 170 selects or synthesizes copolarization or cross-polarization for the RF electronics 172. The diversity signal processor 170 may be as straightforward as a single pole double throw (SPDT) switch for selecting between vertical and horizontal polarization for best signal strength or lowest bit error rate, for example. The diversity signal processor 170 may also operate based on aircraft orientation when mounted on an aircraft 90.
More advanced embodiments of the diversity signal processor 170 may adjust amplitude and phase of the incoming orthogonal polarizations, and combine them to synthesize copolarization for the desired station and cross-polarization for the interference. Even though the function of the diversity signal processor 170 may be primarily directed toward selecting between dual linear polarizations, i.e., vertical and horizontal, slant linear and circular polarization may be synthesized from the orthogonal polarizations provided by the antenna 20 and the diversity signal processor 170. Adding 90 degrees of phase shift to the horizontal polarization and summing it with the vertical polarizations produces circular polarization, for instance.
Referring now to the flowchart 200 in FIG. 12, another aspect is directed to a method for making an antenna 20 as described above. The method comprises, from the start (Block 202), forming a conductive antenna body 30 having first and second opposing ends 32, 36 with an enlarged width medial portion 34 therebetween at Block 204. A slot 38 extends from at least adjacent the first end 32 to at least adjacent the second end 36. First antenna feed points 40, 42 are adjacent the slot 34 for a first polarization.
A conductive antenna member 60 is formed at Block 206 and has a planar shape and a second antenna feed point 62 for a second polarization. The conductive antenna member 60 is positioned adjacent the second end 36 of the conductive antenna body 30 at Block 208. The method comprises at Block 210 coupling a first coaxial cable 70 having inner and outer conductors 72, 74 to respective ones of the first antenna feed points 40, 42. The method comprises at Block 212 coupling a second coaxial cable 80 extending through the conductive antenna body 30 and having an inner conductor 82 coupled to the second antenna feed point 62 and an outer conductor 84 coupled to the conductive antenna member 60. The method ends at Block 214.
While not being bound by a particular theory of operation, curling electric currents on the “flying saucer” like conductive antenna body 30 provides a horizontally polarized form of the loop antenna. Diverging (and alternately converging) electric currents between the conductive antenna body 30 and the conductive antenna member 60 provides a vertically polarized form of the dipole antenna. An infinite number of line shaped wire dipoles can be imagined to exist on the cone surface, and an infinite number of circular wire loop antennas can be imagined to exist on the cone surface as well. The current distributions on the antenna 20 surfaces are standing wave for both vertical and horizontal polarizations.
Antennas can exist in complimentary forms as panels, slots or skeleton slots according to Babinet's Principle and Booker's Relation. As the conductive antenna body 30 does not have hole in it, like a thin wire loop does, the conductive antenna body realizes the panel form of the loop antenna. The conductive antenna body 30 also implements a self exciting horn antenna, with the form of horn being one where fields are guided not by confinement, but by surface wave.
The one or more slots 38 provide impedance matching capability. For instance, the coaxial drive connections 40, 42 may be moved away from the medial portion 34 towards either of the first and second opposing ends 32, 36 to adjust antenna electrical load resistance. Driving the conductive antenna body 30 close to either the first and second opposing ends 32, 36 reduces resistance. Driving the conductive antenna body 30 close to medial portion 34 increases resistance. Moving the driving point along the slot 38 does not appreciably change the radiation pattern. A length of the slot 38 may be varied to adjust resonance frequency or for double tuning.
An additional embodiment of the antenna 320 will now be discussed in reference to FIG. 13, which is based on dual biconical conductive antenna bodies 330(1) and 330(2). This embodiment is advantageous for increased gain and for increased radiation pattern bandwidth while also providing horizontal and vertical polarization.
The antenna 320 includes a first conductive antenna body 320(1) having first and second opposing ends 332(1), 336(1) with an enlarged width medial portion 340(1) therebetween. A first slot 338(1) extends from at least adjacent the first end 332(1) to at least adjacent the second end 336(1). First antenna feed points 340(1), 340(2) are adjacent the first slot 338(1) for a first polarization.
Similarly, a second conductive antenna body 320(1) has first and second opposing ends 332(2), 336(2) with an enlarged width medial portion 340(2) therebetween. A second slot 338(2) extends from at least adjacent the first end 332(2) to at least adjacent the second end 336(2). Second antenna feed points 340(2), 342(2) are adjacent the second slot 338(2) for the first polarization. The first end 332(2) of the second conductive antenna body 330(2) is adjacent the second end 336(1) of the first conductive antenna body 330(1).
The antenna 320 further includes third antenna feed points 370, 372 between the first and second conductive antenna bodies 330(2), 330(2) for a second polarization. The first and second polarizations are orthogonal to one another. As discussed above, the first polarization may correspond to horizontal polarization and the second polarization may correspond to vertical polarization.
Excitation for the first polarization may be provided by RF sources 360(1), 360(2). The RF sources 360(1), 360(2) are preferentially equal in amplitude and equal in phase for providing a broadside, horizon radiation. The RF sources 360(1), 360(2) are connected by coaxial transmission lines as discussed above and which are not shown for clarity. Nonetheless, a first coaxial cable having inner and outer conductors would be coupled to respective ones of the first antenna feed points 340(1), 342(1) of the first conductive antenna body 330(1). A second coaxial cable having inner and outer conductors would be coupled to respective ones of the second antenna feed points 340(2), 342(2) of the second conductive antenna body 330(2).
Excitation for the second polarization may be provided by an RF source 380. This RF source 380 may be connected by a coaxial cable which is not shown for clarity. A third coaxial cable having inner and outer conductors may be coupled to respective ones of the third antenna feed points 370, 372. The vertical polarization pattern radiation pattern is very constant with frequency, e.g., the radiation pattern lobes stay on the horizon over a broad bandwidth. Dual linear polarizations may be provided by the antenna structure itself or by phase quadrature excitation (0, 90 degrees) at the RF sources 360(1), 360(2), 380 to synthesize circular polarization.
The first and second conductive antenna bodies 330(1), 330(2) each comprises first and second conical antenna elements 352(1), 354(1) and 352(2), 354(2) coupled together at the respective medial portion 340(1) and 340(2). The medial portion 340(1) of the first conductive antenna body 330(1) is aligned with the medial portion 340(2) of the second conductive antenna body 330(2).
Referring now to the flowchart 400 in FIG. 14, another aspect is directed to a method for making an antenna 320 as described above. The method comprises, from the start (Block 402), forming a first conductive antenna body 330(1) having first and second opposing ends 332(1), 336(1) with an enlarged width medial portion 340(1) therebetween at Block 404. A first slot 338(1) extends from at least adjacent the first end 332(1) to at least adjacent the second end 336(1), and first antenna feed points 340(1), 340(2) are adjacent the first slot 338(1) for a first polarization.
A second conductive antenna body 330(2) is formed at Block 406 and has first and second opposing ends 332(2), 336(2) with an enlarged width medial portion 340(2) therebetween. A second slot 338(2) extends from at least adjacent the first end 332(2) to at least adjacent the second end 336(2), and second antenna feed points 340(2), 342(2) are adjacent the second slot 338(2) for the first polarization. The first end 332(2) of the second conductive antenna body 330(2) is positioned adjacent the second end 336(2) of the first conductive antenna body 330(1) at Block Third antenna feed points 370, 372 are formed between the first and second conductive antenna bodies 330(1), 330(2) for a second polarization at Block 410.
The method further includes coupling a first coaxial cable having inner and outer conductors coupled to respective ones of the first antenna feed points 340(1), 342(1) of the first conductive antenna body 330(1) at Block 412, coupling a second coaxial cable having inner and outer conductors to respective ones of the second antenna feed points 340(2), 342(2) of the second conductive antenna body 330(2) at Block 414, and coupling a third coaxial cable having inner and outer conductors to respective ones of the third antenna feed points 370, 372 at Block 416. The method ends at Block 418.
In view of the above discussions, other antenna embodiments are also practical, where multiple conductive antenna bodies and multiple conductive antenna members may be stacked and interposed, akin to a totem pole, as readily appreciated by those skilled in the art.
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.
This application is related to copending patent application entitled, “BROADBAND DUAL POLARIZATION OMNI-DIRECTIONAL ANTENNA AND ASSOCIATED METHODS,” attorney docket number GCSD-2745 (62036) which is filed on the same date and by the same assignee and inventors, the disclosures which are hereby incorporated by reference.

## Claims

1. An antenna comprising:
a first biconically-shaped conductive antenna body having first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points on opposite sides of the first slot for a first polarization;
a second biconically-shaped conductive antenna body also having first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points on opposite sides of the second slot for the first polarization, with the first end of said second conductive antenna body adjacent the second end of said first conductive antenna body so that the antenna has a dual biconical shape; and
third antenna feed points between said first and second conductive antenna bodies for a second polarization.

2. The antenna according to claim 1 wherein said first and second conductive antenna bodies each comprises first and second conical antenna elements coupled together at the medial portion.

3. The antenna according to claim 2 wherein the medial portion of said first conductive antenna body is aligned with the medial portion of said second conductive antenna body.

4. The antenna according to claim 1 further comprising:
a first coaxial cable having inner and outer conductors coupled to respective ones of said first antenna feed points of said first conductive antenna body;
a second coaxial cable extending through said first conductive antenna body and having inner and outer conductors coupled to respective ones of said second antenna feed points of said second conductive antenna body; and
a third coaxial cable extending through said first conductive antenna body and having inner and outer conductors coupled to respective ones of said third antenna feed points.

5. The antenna according to claim 1 wherein said first and second conductive antenna bodies each comprises a continuous conductive layer.

6. The antenna according to claim 1 wherein said first and second conductive antenna bodies each comprises a wire structure.

7. The antenna according to claim 1 further comprising an airfoil post supporting said first conductive antenna body.

8. The antenna according to claim 1 wherein the first and second polarizations are orthogonal to one another.

9. An antenna comprising:
a first conductive antenna body comprising first and second conical antenna elements arranged to define having first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points on opposite sides of the first slot for a first polarization;
a second conductive antenna body comprising first and second conical antenna elements arranged to define having first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points on opposite sides of the second slot for the first polarization, with the first end of said second conductive antenna body adjacent the second end of said first conductive antenna body so that the antenna has a dual biconical shape; and
third antenna feed points between said first and second conductive antenna bodies for a second polarization.

10. The antenna according to claim 9 wherein the medial portion of said first conductive antenna body is aligned with the medial portion of said second conductive antenna body.

11. The antenna according to claim 9 further comprising:
a first coaxial cable having inner and outer conductors coupled to respective ones of said first antenna feed points of said first conductive antenna body;
a second coaxial cable extending through said first conductive antenna body and having inner and outer conductors coupled to respective ones of said second antenna feed points of said second conductive antenna body; and
a third coaxial cable extending through said first conductive antenna body and having inner and outer conductors coupled to respective ones of said third antenna feed points.

12. The antenna according to claim 9 wherein said first and second conductive antenna bodies each comprises a continuous conductive layer.

13. The antenna according to claim 9 wherein said first and second conductive antenna bodies each comprises a wire structure.

14. The antenna according to claim 9 further comprising an airfoil post supporting said first conductive antenna body.

15. The antenna according to claim 9 wherein the first and second polarizations are orthogonal to one another.

16. A method for making an antenna comprising:
forming a first biconically--shaped conductive antenna body having first and second opposing ends with an enlarged width medial portion therebetween, a first slot extending from at least adjacent the first end to at least adjacent the second end, and first antenna feed points on opposite sides of the first slot for a first polarization;
forming a second biconically-shaped conductive antenna body also having first and second opposing ends with an enlarged width medial portion therebetween, a second slot extending from at least adjacent the first end to at least adjacent the second end, and second antenna feed points on opposite sides of the second slot for the first polarization;
positioning the first end of the second conductive antenna body adjacent the second end of the first conductive antenna body so that the antenna has a dual biconical shape; and
forming third antenna feed points between the first and second conductive antenna bodies for a second polarization.

17. The method according to claim 16 wherein the first and second conductive antenna bodies each comprises first and second conical antenna elements coupled together at the medial portion.

18. The method according to claim 17 further comprising aligning the medial portion of the first conductive antenna body with the medial portion of the second conductive antenna body.

19. The method according to claim 16 further comprising:
coupling a first coaxial cable having inner and outer conductors coupled to respective ones of the first antenna feed points of the first conductive antenna body;
coupling a second coaxial cable having inner and outer conductors to respective ones of the second antenna feed points of the second conductive antenna body; and
coupling a third coaxial cable having inner and outer conductors to respective ones of the third antenna feed points.

20. The method according to claim 16 wherein the first and second conductive antenna bodies each comprises a continuous conductive layer.

21. The method according to claim 16 wherein the first and second conductive antenna bodies each comprises a wire structure.

22. The method according to claim 16 wherein the first and second polarizations are orthogonal to one another.