Enhanced band multiple polarization antenna assembly

An antenna assembly is provided for receiving and transmitting radio frequency signals over an enhanced frequency band. A first radiative element has a first end, a second end, and an associated length, and is comprised of an electrically conductive material. The first end of the first radiative element is electrically connected to an antenna feed at an apex and at least a portion of the first radiative element is disposed outwardly away from the apex at an acute angle relative to, and on a first side of, an imaginary plane intersecting the apex. A second radiative element has a first end and a second end and is comprised of an electrically conductive material. The first end of the second radiative element is electrically connected to the antenna feed and the first radiative element at the apex. The second end of the second radiative element has an associated height above the imaginary plane that is less than the product of the length of the first element and the sine of the acute angle at which the first element is disposed outwardly from the apex. The assembly further comprises an electrically conductive ground reference.

RELATED APPLICATIONS

This application claims priority from pending U.S. application Ser. No. 11/279,941, filed Apr. 17, 2006 and published as U.S. Published Patent Application No. 2007/0132651 which is a divisional of patent application Ser. No. 10/786,656, filed on Feb. 25, 2004, now U.S. Pat. No. 7,030,831, issued Apr. 18, 2006, which was a continuation-in-part of patent application Ser. No. 10/294,420 filed on Nov. 14, 2002, now U.S. Pat. No. 6,806,841 which issued on Oct. 19, 2004. Each of these documents are incorporated herein by reference in their entirety.

TECHNICAL FIELD

Certain embodiments of the present invention relate to antennas for wireless communications. More particularly, certain embodiments of the present invention relate to an apparatus and method providing a multi-band, wide-band, or broadband multi-polarized antenna exhibiting substantial spatial diversity for use in point-to-point and point-to-multipoint communication applications for the Internet, land, maritime, aviation, and space.

BACKGROUND OF THE INVENTION

For years, wireless communications have struggled with limitations of audio/video/data transport and internet connectivity in both obstructed (indoor/outdoor) and line-of-site (LOS) deployments. A focus on antenna gain as well as circuitry solutions have proven to have significant limitations. Unresolved, non-optimized (leading edge) technologies have often given way to “bleeding edge” attempted resolutions. Unfortunately, all have fallen short of desirable goals.

While lower frequency radio waves benefit from an ‘earth hugging’ propagation advantage, higher frequencies do inherently benefit from (multi-) reflection/penetrating characteristics. However, with topographical changes (hills & valleys) and object obstructions (e.g., natural such as trees, and man-made such as buildings/walls) and with the resultant reflections, diffractions, refractions and scattering, maximum signal received may well be off-axis (non-direct path) and multi-path (partial) cancellation of signals results in null/weaker spots. Also, some antennas may benefit from having gain at one elevation angle (‘capturing’ signals of some pathways), while other antennas have greater gain at another elevation angle, each type being insufficient where the other does well. In addition, the radio wave can experience altered polarizations as they propagate, reflect, refract, diffract, and scatter. A very preferred (polarization) path may exist; however, insufficient capture of the signal can result if this preferred path is not utilized.

BRIEF SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, an antenna assembly is provided for receiving and transmitting radio frequency signals over an enhanced frequency band. A first radiative element has a first end, a second end, and an associated length, and is comprised of an electrically conductive material. The first end of the first radiative element is electrically connected to an antenna feed at an apex and at least a portion of the first radiative element is disposed outwardly away from the apex at an acute angle relative to, and on a first side of, an imaginary plane intersecting the apex. A second radiative element has a first end and a second end and is comprised of an electrically conductive material. The first end of the second radiative element is electrically connected to the antenna feed and the first radiative element at the apex. The second end of the second radiative element has an associated height above the imaginary plane that is less than the product of the length of the first element and the sine of the acute angle at which the first element is disposed outwardly from the apex. The assembly further comprises an electrically conductive ground reference.

In accordance with another aspect of the invention, an antenna assembly is provided for receiving and transmitting radio frequency signals over an enhanced frequency band. The antenna assembly comprises an electrically conductive ground reference. A first set of a plurality of curvilinear radiative elements are each electrically connected at respective first ends to an antenna feed at an apex and are comprised of an electrically conductive material. At least a portion of each of the first set of radiative elements are disposed outwardly away from the apex on a first side of the imaginary plane. Each of the first set of curvilinear elements having a length are tuned to a first characteristic frequency and curved such that respective second ends of the first set of radiative elements are located below a predetermined height above the imaginary plane.

In accordance with yet another aspect of the present invention, an antenna assembly is provided for receiving and transmitting radio frequency signals over an enhanced frequency band. A set of a plurality of radiative elements are each electrically connected to an antenna feed at an apex and comprised of an electrically conductive material, At least a portion of each of the set of radiative elements are disposed outwardly away from the apex at an acute angle relative to, and on a first side of the imaginary plane. Each of the set of radiative elements has a length within a first range associated with a first characteristic frequency, such that the associated lengths of the set of radiative elements are selected as to tune the antenna to the first characteristic frequency.

A second set of a plurality of radiative elements are each electrically connected to the antenna feed at the apex and comprised of an electrically conductive material. At least a portion of each of the second set of radiative elements is disposed outwardly away from the apex at an acute angle relative to, and on a first side of the imaginary plane. Each of the second set of radiative elements has a length within a second range that does not overlap the first range. The assembly further comprises an electrically conductive ground reference.

DETAILED DESCRIPTION OF THE INVENTION

Generally stated, a novel three-dimensionally constructed antenna with in-built spatial diversity (one part perhaps in a “null spot,” while another part of the antenna in a: “hot spot”), relatively broad signal patterning, and in-built polarization diversity serves to stabilize signal and throughput (minimizing Ethernet rejects and the like) in the real “obstructed,” often dynamic world.FIG. 1illustrates a first embodiment of an enhanced band, multi-polarized antenna10for transmitting and receiving radio frequency signals in accordance with various aspects of the present invention. It will be appreciated that the term “radio frequency,” is intended to encompass frequencies within the microwave and traditional radio bands, specifically frequencies between 3 kHz and 3 THz. Further, the term “enhanced band” is intended to refer to wideband and multiband applications. The antenna comprises a multi-polarized driven assembly20that includes at least a first radiative element22and a second radiative element24, each formed from a conductive material. The two radiative elements22and24of the driven element20have respective first ends are electrically connected to one another and an antenna feed30at an apex point32such that the radiative elements22and24each extend to respective second ends. In accordance with an aspect of the invention, at least a portion of the first radiative element extends outwardly from the apex point at an acute angle, that is an angle less than ninety degrees, relative to an imaginary plane34intersecting the apex point32. The radiative elements22and24are all located to a first side of the imaginary plane34. It will be appreciated that additional radiative elements (not shown) can be utilized in the driven element in accordance with various implementations of the invention.

Electromagnetic waves are often reflected, diffracted, refracted, and scattered by surrounding objects, both natural and man-made. As a result, electromagnetic waves that are approaching a receiving antenna can be arriving from multiple angles and have multiple polarizations and signal levels. The antenna10illustrated inFIG. 1is configured to capture or utilize the preferred approaching signal whether the preferred signal is a line-of-sight (LOS) signal or a reflected signal, and no matter how the signal is polarized. In the illustrated antenna10, the multiple radiative members22and24are positioned over a ground plane and properly spaced to allow signals of diverse polarizations to generated and/or received in various different directions. Therefore, such a driven element is said to be “multi-polarized” as well as providing “geometric spatial capture of signal”. If a driven element produced all polarizations in all planes (e.g., all planes in an x, y, z coordinate system) and the receiving antenna is capable of capturing all polarizations in all planes, then the significantly greatest preferred polarization path, that is the signal path allowing for maximum signal amplitude, may be utilized, as well as well as a variety of polarization diverse and spatially diverse resultant signals.

A conductive ground plane structure40can be located at the imaginary plane or on a second side of the imaginary plane34. The ground plane structure40is illustrated herein as a conical member, but it will be appreciated that the ground plane structure can be configured in any of a number of ways. For example, a planar or cylindrical ground plane can be utilized. Further, the ground plane structure40does not need to be a single, solid structure. For example, the ground plane can be implemented as a conductive mesh or comprise a number of discrete conductive elements evenly spaced around the apex point32.

In accordance with an embodiment of the present invention, the first radiative antenna element22can have a length, L, and an angle of incidence, θ, with the imaginary plane34. The second radiative antenna element24can be configured such that a second end42of the second radiative element is at a height, H, above the imaginary plane34that is less than the product of the length of the first antenna element22and the sine of the angle of incidence, such that:
H<Lsin(θ)  Eq. 1

By maintaining the height of the second end42of the second radiative element24below this level, it is possible to introduce enhanced band sensitivity to the antenna assembly without significantly increasing the size and complexity of the antenna assembly.

FIG. 2illustrates a side view of a first exemplary implementation of an antenna assembly50in accordance with an aspect of the present invention.

FIG. 3illustrates an overhead view of the first exemplary implementation of the antenna assembly. The illustrated antenna assembly50comprises a driven antenna assembly52located on a first side of an imaginary plane54, and a ground reference56located at the imaginary plane or on a second side of the imaginary plane. The driven antenna assembly52can be driven by an antenna feed that is electrically connected to the driven antenna assembly approximately at the imaginary plane54. In the illustrated implementation, the ground reference56is illustrated as planar, but it will be appreciated that other configurations of the ground plane can be utilized within the illustrated antenna assembly. The ground reference56may be comprised of any appropriate electrically conductive material such as, for example, copper or stainless steel. The radius of the ground reference56is at least one-quarter of a wavelength of the lowest frequency of operation.

The surface of the ground reference56may be continuous or may be a crosshatched wired mesh, in accordance with various embodiments of the present invention. Also, three or more linear elements disposed in a substantially conical shape may form the ground reference, in accordance with an embodiment of the present invention. In other implementations, the ground reference56can include a conical assembly or a cylindrical sleeve having a closed upper base side. Alternatively, the shield of a coaxial associated with the antenna feed can serve as the ground reference, and various styles of stubs, sleeves, matching systems, baluns, transformers, etc. may also be used. The antenna feed58can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect to the driven antenna assembly52and allows a ground braid of the coaxial cable to electrically connect to the ground reference56. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly52from the ground reference56.

The driven antenna assembly52comprises six radiative elements62-64and66-68that radiate out from a common apex70. The driven antenna assembly52and its constituent elements62-64and66-68are formed from a conductive material. The radiative elements62-64and66-68are electrically connected to the antenna feed58and one another at the apex70. A first set of radiative elements comprise first, second, and third radiative elements62-64that are generally linear and extend away from the apex70at an acute angle relative to the imaginary plane54. Each of the first, second, and third radiative antenna elements62-64may be at a unique acute angle or at the same acute angle relative to the imaginary plane54. In the illustrated implementation, the first, second, and third radiative elements62-64are oriented such that the first, second, and third elements are spaced evenly, that is, at intervals of one-hundred and twenty degrees. Each of the first set of radiative elements62-64have a length within a first range of lengths associated with a first characteristic frequency. For example, a first element62can have a length, L1, tuned to be receptive to the first characteristic frequency and each of the second and third elements63and64can have a length within an approximately ten percent variance of the length of the first element. Varying the lengths of the first set of radiative elements62-64can provide an improvement in the broadband properties of the driven antenna assembly, but it will be appreciated that a common antenna length, for example, the tuned antenna length L1, can be utilized for the first set of radiative elements in while still maintain the wideband properties of the antenna.

A second set of radiative elements comprise fourth, fifth, and sixth radiative elements66-68that are generally linear and extend away from the apex70at an acute angle relative to the imaginary plane54. Each of the fourth, fifth, and sixth radiative antenna elements66-68may be at a unique acute angle or at the same acute angle relative to the imaginary plane54as one another or one of the first set of radiative elements62-64. In the illustrated implementation, the fourth, fifth, and sixth radiative elements66-68are oriented such that they are spaced evenly between the first set of radiative elements62-64, such that each of the second set of radiative elements is spaced at sixty degree intervals from two of the first set of radiative elements and at intervals of one-hundred and twenty degrees from one another. Each of the second set of radiative elements66-68have a length within a second range of lengths associated with a second characteristic frequency. For example, the fourth element66can have a length, L2, tuned to be receptive to the second characteristic frequency and each of the fifth and sixth elements67and68can have a length within an approximately ten percent variance of the length of the fourth element. The lengths of the radiative elements62-64and66-68can be configured such that the first range of lengths and the second range of lengths do not overlap.

In the illustrated implementation, the antenna assembly50is designed with a first characteristic frequency of 2.4 GHz and a second characteristic frequency of 5 GHz, allowing the antenna to operate at a wide band of radio frequencies ranging from approximately 2.0 GHz to approximately 11 GHz. The lengths of the first set of radiative elements62-64can be tuned to a frequency of 2.4 GHz, with the first radiative element62having a length of approximately 0.875 inches, the second radiative element63being shorter by a factor less than ten percent (e.g., ˜0.813 inches) and the third radiative element64can longer by a factor less than ten percent (e.g., 0.938 inches). The lengths of the second set of radiative elements66-68can be tuned to a frequency of 5 GHz, such that the fourth radiative element66has a length of approximately 0.563 inches, the fifth radiative element67can be shorter by a factor less than ten percent (e.g., ˜0.5 inches) and the sixth radiative element68can be longer by a factor of less than ten percent (e.g., 0.625 inches). Each of the radiative elements can have a diameter of approximately one-sixteenth of an inch. By implementing the driven antenna assembly52as a series of elements of varying lengths, an ultra wide band, multi-polarized antenna assembly can be realized.

In accordance with an aspect of the present invention, each of the first and second sets of radiative elements62-64and66-68can be generalized to only two or greater than three elements having similar length and orientation. For example, in place of the first set of radiative elements62-64, four radiative elements, circumferentially spaced at intervals of ninety degrees, or otherwise, may be used. In fact, in one implementation, the first and second sets of radiative elements62-64and66-68may be effectively replaced with a continuous surface of a cone, a pyramid, or some other continuous shape that is spatially diverse on one side (e.g., has significant spatial extent) and comes substantially to a point (e.g., an apex) on the other side. For example, in accordance with an aspect of the present invention, a linear radiative member connected at one end to a radiative loop having a certain spatial extend may be used.

FIG. 4illustrates a side view of a second exemplary implementation of an antenna assembly100in accordance with an aspect of the present invention.

FIG. 5illustrates an overhead view of the second exemplary implementation of the antenna assembly. The illustrated antenna assembly100comprises a driven antenna assembly102located on a first side of an imaginary plane104, and a ground reference106located at the imaginary plane or on a second side of the imaginary plane. The driven antenna assembly102can be driven by an antenna feed that is electrically connected to the driven antenna assembly approximately at the imaginary plane104. In the illustrated implementation, the ground reference106is illustrated as planar, but it will be appreciated that other configurations of the ground plane can be utilized within the illustrated antenna assembly. The ground reference106may be comprised of any appropriate electrically conductive material such as, for example, copper or stainless steel. The radius of the ground reference106is at least one-quarter of a wavelength associated with the lowest frequency of operation.

The surface of the ground reference106may be continuous or may be a crosshatched wired mesh, in accordance with various embodiments of the present invention. Also, three or more linear elements disposed in a substantially conical shape may form the ground reference, in accordance with an embodiment of the present invention. In other implementations, the ground reference106can include a conical assembly or a cylindrical sleeve having a closed upper base side. Alternatively, the shield of a coaxial associated with the antenna feed can serve as the ground reference, and various styles of stubs, sleeves, matching systems, baluns, transformers, etc. may also be used. The antenna feed108can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect the driven antenna assembly102and allows a ground braid of the coaxial cable to electrically connect to the ground reference106. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly102from the ground reference106.

The driven antenna assembly102comprises six radiative elements112-114and116-118that radiate out from a common apex120. The driven antenna assembly102and its constituent elements112-114and116-118are formed from a conductive material. The radiative elements112-114and116-118are electrically connected to the antenna feed108and one another at the apex120. A first set of radiative elements comprise first, second, and third radiative elements112-114that are generally linear and extend away from the apex120at an acute angle relative to the imaginary plane104. Each of the first, second, and third radiative antenna elements112-114may be at a unique acute angle or at the same acute angle relative to the imaginary plane104. In the illustrated implementation, the first, second, and third radiative elements112-114are oriented such that the first, second, and third elements are spaced evenly, that is, at intervals of one-hundred and twenty degrees. Each of the first set of radiative elements112-114have a length within a first range of lengths associated with a characteristic lower bound frequency. For example, a first element112can have a length, L1, tuned to be receptive to the characteristic lower bound frequency and each of the second and third elements113and114can have a length within an approximately ten percent variance of the length of the first element. Varying the lengths of the first set of radiative elements112-114can provide an improvement in the broadband properties of the driven antenna assembly, but it will be appreciated that a common antenna length, for example, the tuned antenna length L1, can be utilized for the first set of radiative elements in while still maintain the wideband properties of the antenna.

A second set of radiative elements comprise fourth, fifth, and sixth radiative elements116-118that are generally linear and extend away from the apex120at an acute angle relative to the imaginary plane104. Each of the fourth, fifth, and sixth radiative antenna elements116-118may be at a unique acute angle or at the same acute angle relative to the imaginary plane104as one another or one of the first set of radiative elements112-114. In the illustrated implementation, the fourth, fifth, and sixth radiative elements116-118are oriented such that they are spaced evenly between the first set of radiative elements112-114, such that each of the second set of radiative elements is spaced at sixty degree intervals from two of the first set of radiative elements and at intervals of one-hundred and twenty degrees from one another. Each of the second set of radiative elements116-118have a length in a second range around a length of approximately four-fifths the tuned length associated with the characteristic frequency. In one implementation, the length of each of the second set of radiative elements116-118can be equal to four-fifths the length of a corresponding one of the first set of radiative elements112-114.

In the illustrated implementation, the antenna assembly100is designed with a characteristic lower bound frequency around 700 MHz, and the lengths of the first set of radiative elements112-114selected as to tune the antenna to that frequency. In the illustrated implementation, the first radiative element112can have a length of approximately 3.19 inches, the second radiative element113can have a length of approximately 2.88 inches, and the third radiative element114can have a length of approximately 3.25 inches). The lengths of the second set of radiative elements116-118can be cut to approximately four-fifths the length of the first set of radiative elements112-114. Accordingly, the fourth radiative element116can have a length of around 2.56 inches, the fifth radiative element117can have a length on the order of 2.31 inches, and the sixth radiative element118can have a length of approximately 2.63 inches. Each element112-114can have a diameter of approximately one-sixteenth of an inch, and the planar ground reference106can have a diameter of eleven inches. The illustrated antenna100can operate at an extremely wide band of radio frequencies ranging from approximately 700 MHz to approximately 6 GHz.

In accordance with an aspect of the present invention, each of the first and second sets of radiative elements112-114and116-118can be generalized to only two or greater than three elements having similar length and orientation. For example, in place of the first set of radiative elements112-114, four radiative elements, circumferentially spaced at intervals of ninety degrees, or otherwise, may be used. In fact, the first and second sets of radiative elements112-114and116-118may be effectively replaced with a continuous surface of a cone, a pyramid, or some other continuous shape that is spatially diverse on one side (e.g., has significant spatial extent) and comes substantially to a point (e.g., an apex) on the other side. For example, in accordance with an aspect of the present invention, a linear radiative member connected at one end to a radiative loop having a certain spatial extend may be used.

FIG. 6illustrates a side view of a third exemplary implementation of an antenna assembly150in accordance with an aspect of the present invention. The illustrated antenna assembly150comprises a driven antenna assembly152located on a first side of an imaginary plane154, and a ground reference156located at the imaginary plane or on a second side of the imaginary plane. The driven antenna assembly152can be driven by an antenna feed that is electrically connected to the driven antenna assembly approximately at the imaginary plane154. In the illustrated implementation, the ground reference156is illustrated as planar, but it will be appreciated that other configurations of the ground plane can be utilized within the illustrated antenna assembly. The ground reference156may be comprised of any appropriate electrically conductive material such as, for example, copper or stainless steel. The antenna feed158can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect the driven antenna assembly152and allows a ground braid of the coaxial cable to electrically connect to the ground reference156. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly152from the ground reference156.

The driven antenna assembly152comprises three radiative elements162-164that spiral outward from a common apex170. It will be appreciated, however, that one element, two elements, or more than three elements can also be utilized. The driven antenna assembly152and its constituent elements162-164are formed from a conductive material. The radiative elements162-164are electrically connected to the antenna feed158and one another at respective first ends at the apex170. Each of the radiative elements162-164are curvilinear and radiate away from the apex170. In the illustrated implementation, the first, second, and third radiative elements162-164are oriented such that the first, second, and third elements are spaced evenly as they leave the apex170, that is, at intervals of one-hundred and twenty degrees.

Each of the first set of radiative elements162-164has a length within a first range of lengths associated with a first characteristic frequency. It will be appreciated that length, as used herein, refers to the straightened length of the element, as opposed to the distance it extend from the apex170. For example, a first element162can have a length, L1, tuned to be receptive to the first characteristic frequency and each of the second and third elements163and164can have a length within an approximately ten percent variance of the length of the first element. Varying the lengths of the radiative elements162-164can provide an improvement in the broadband properties of the driven antenna assembly, but it will be appreciated that a common antenna length, for example, the tuned antenna length L1, can be utilized for the first set of radiative elements in while still maintain the enhanced band properties of the antenna.

In accordance with an aspect of the present invention, the radiative elements162-164can be curved such that respective second ends172-174of the radiative elements are located at a predetermined height above the ground reference156. This height can be selected to be approximately one-quarter of a wavelength associated with a second characteristic frequency. The rate of ascent of the curvilinear elements162-164can be relatively high until this height is approached and then significantly slowed to maximize the length of the curvilinear element at or near this height. By curving the curvilinear elements162-164in this manner, an additional degree of capacitive and inductive coupling between the elements162-164and the ground reference156can be established, allowing the antenna increased sensitivity around the second characteristic frequency. Accordingly, the illustrated antenna assembly150is sensitive to frequencies in bands around both the first characteristic frequency and the second characteristic frequency, allowing for true dual-band operation from a single driven radiative assembly.

In accordance with an aspect of the present invention, the polarization diversity of the antenna assembly150around the horizon can be greatly enhanced through the use of the curvilinear elements162-164. In the illustrated antenna assembly150, the radiation pattern includes alternating horizontally and vertically polarized lobes around the horizon of the pattern, allowing the antenna to be responsive to multiple polarizations even at a low elevation. This alternating horizontal and vertical polarization is particularly useful in dynamic environments and mobile applications. The use of the curvilinear elements162-164also allows for a significant reduction in the size of the ground reference156, such that the radius of the ground reference can be significantly smaller than one-quarter of the wavelength associated with the lowest frequency of operation.

In the illustrated implementation, the antenna assembly150is designed to operate in a first band around 800 MHz and a second band around 1.8 GHz to 1.9 GHz. To this end, the lengths of the curvilinear radiative elements162-164can be as to tune the antenna to a frequency of 800 MHz. Accordingly, the first curvilinear element162can have a length of approximately 4 inches, the second curvilinear element163can have a length of approximately 4.13 inches, and the third curvilinear element214can have a length of approximately 3.44 inches. The height of each of the second ends172-174of the curvilinear elements162-164above the ground reference156can range around one-quarter of a wavelength corresponding to a frequency of 1.8 GHz. It has been determined in implementing the illustrated antenna that a height of approximately 1.75 inches for the second ends172-174of the curvilinear elements162-164allows for operation in the 1.8 GHz-1.9 GHz band.

FIG. 7illustrates a side view of a fourth exemplary implementation of an antenna assembly200in accordance with an aspect of the present invention. The illustrated antenna assembly200comprises a driven antenna assembly202located on a first side of an imaginary plane204, and a ground reference206located at the imaginary plane or on a second side of the imaginary plane. The driven antenna assembly202can be driven by an antenna feed that is electrically connected to the driven antenna assembly approximately at the imaginary plane204. In the illustrated implementation, the ground reference206is illustrated as planar, but it will be appreciated that other configurations of the ground plane can be utilized within the illustrated antenna assembly. The ground reference206may be comprised of any appropriate electrically conductive material such as, for example, copper or stainless steel. The antenna feed208can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect the driven antenna assembly202and allows a ground braid of the coaxial cable to electrically connect to the ground reference206. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly202from the ground reference206.

The driven antenna assembly202comprises a first set of three radiative elements212-214and a second set of radiative elements216-218that spiral outward from a common apex220. It will be appreciated, however, that one element, two elements, or more than three elements can also be utilized in each set. The driven antenna assembly202and its constituent elements212-214and216-218are formed from a conductive material. The radiative elements212-214and216-218are electrically connected to the antenna feed208and one another at respective first ends at the apex220. Each of the radiative elements212-214and216-218are curvilinear and radiate away from the apex220. In the illustrated implementation, the curvilinear elements extend away from the apex220near a desired horizontal radius from the apex at a first rate of ascent, and tend proceed at a second rate of ascent, greater than the first rate of ascent. In the illustrated implementation, this is accomplished without any change to the sign of the curvature; the direction of concavity of the element does not change. Accordingly, the maximum horizontal extent of the curvilinear elements, and thus, the radius of the ground reference206, can be limited without a significant loss of sensitivity in the lower frequency portion of the band. It will be appreciated, however, that due to the curvature of the curvilinear elements, the height of the curvilinear elements will also be limited, lowering the overall profile of the antenna assembly.

In the illustrated implementation, the first, second, and third radiative elements212-214are oriented such that the first, second, and third elements are spaced evenly as they leave the apex220, that is, at intervals of one-hundred and twenty degrees. The fourth, fifth, and sixth radiative elements216-218are oriented such that they are spaced evenly between the first set of radiative elements212-214, such that each of the second set of radiative elements is spaced at sixty degree intervals from two of the first set of radiative elements as they leave the apex and at intervals of one-hundred and twenty degrees from one another.

Each of the first set of radiative elements212-214has a length within a first range of lengths associated with a first characteristic frequency. It will be appreciated that by “length,” reference the actual or straightened length of the curvilinear element is intended. A first element212can have a length, L1, tuned to be receptive to the first characteristic frequency and each of the second and third elements213and214can have a length within an approximately ten percent variance of the length of the first element. Varying the lengths of the first set of radiative elements212-214can provide an improvement in the broadband properties of the driven antenna assembly, but it will be appreciated that a common antenna length, for example, the tuned antenna length L1, can be utilized for the first set of radiative elements in while still maintain the enhanced band properties of the antenna. Each of the second set of radiative elements216-218have a length in a second range around a length of approximately four-fifths the tuned length associated with the characteristic frequency. In one implementation, the length of each of the second set of radiative elements216-218can be equal to four-fifths the length of a corresponding one of the first set of radiative elements212-214. In the illustrated implementation, the antenna assembly100is designed to operate band of frequencies ranging from around 700 MHz to around 6 GHz continuously. To this end, the first curvilinear element212can have a length of approximately 4.25 inches, the second curvilinear element213can have a length of approximately 4.5 inches, and the third curvilinear element214can have a length of approximately 4 inches. The maximum height of each of the of the first set of curvilinear elements212-214above the ground reference206can be limited to approximately 2.5 inches. The lengths of the second set of radiative elements216-218can be cut to approximately four-fifths the length of the first set of radiative elements212-214. Accordingly, the fourth radiative element216can have a length of around 3.5 inches, the fifth radiative element217can have a length on the order of 3.75 inches, and the sixth radiative element218can have a length of approximately 3.25 inches. Each element212-214and216-218can have a diameter of approximately one-sixteenth of an inch.

FIG. 8illustrates a side view of a fifth exemplary implementation of an antenna assembly250in accordance with an aspect of the present invention. The illustrated antenna assembly250comprises a driven antenna assembly252located on a first side of an imaginary plane254, and a ground reference256. The driven antenna assembly252can be driven by an antenna feed258that is electrically connected to the driven antenna assembly approximately at the imaginary plane254. The ground reference256may be comprised of any appropriate electrically conductive material such as, for example, copper or stainless steel.

In the illustrated implementation, the ground reference256is implemented as a series of curvilinear ground elements262-264that extend along the second side of the imaginary plane254to form an outline of a conical structure having a crenellated edge. Each of the curvilinear ground elements262-264can have a substantially linear portion that extends from a shield portion of the antenna feed258at an acute angle relative to the imaginary plane254. In generally, the acute angle between each of the curvilinear ground elements262-264and the imaginary plane254will be between forty-five degrees and seventy degrees, and in the illustrated implementation, each curvilinear ground element forms a sixty degree angle with the imaginary plane. A crenellated portion of each of the curvilinear ground elements262-264can run substantially parallel to the imaginary plane as to form at least a portion of an elliptical or circular outline in a plane parallel to the imaginary plane.

The antenna feed258can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect the driven antenna assembly252and allows a ground braid, or shield portion, of the coaxial cable to electrically connect to each of the discrete curvilinear elements comprising the ground reference256. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly252from the ground reference256.

The driven antenna assembly252comprises a set of curvilinear radiative antenna elements266-268that spiral outward from a common apex270. It will be appreciated, however, that one element, two elements, or more than three elements can also be utilized in each set. The driven antenna assembly252and its constituent elements266-268are formed from a conductive material. The radiative elements266-268are electrically connected to the antenna feed258and one another at respective first ends at the apex270. Each of the radiative elements266-268are curvilinear and radiate away from the apex270. In the illustrated implementation, the curvilinear elements extend away from the apex270near a desired horizontal radius from the apex at a first rate of ascent, and then proceed at a second rate of ascent that is less than the first rate of ascent. It will be appreciated, however, that in other implementations, the second rate of ascent can be greater than the first rate of ascent. Accordingly, the maximum vertical extent of the curvilinear elements266-268, and thus the vertical profile of the antenna assembly250, can be limited without a significant loss of sensitivity in the lower frequency portion of the band. The vertical profile and ground plane radius of the assembly can be further reduced through use of the discrete curvilinear ground elements262-264, greatly reducing the amount of space necessary to implement the antenna assembly.

In the illustrated implementation, the curvilinear ground elements262-264are oriented such that respective first, second, and third elements are spaced evenly as they leave the shield portion of the antenna feed, that is, at intervals of one-hundred and twenty degrees. The respective first, second, and third radiative elements266-268are oriented such that they are spaced evenly as they leave the apex, at intervals of one-hundred and twenty degrees. Each of the set of curvilinear ground elements262-264has a length within a first range of lengths associated with a first characteristic frequency. It will be appreciated that by “length,” reference the actual or straightened length of the curvilinear element is intended. A first curvilinear ground element262can have a length, L1, the second and third curvilinear ground elements263and264can have a length within an approximately ten percent variance of the length of the first element. Varying the lengths of the curvilinear ground elements262-264can provide an improvement in the broadband properties of the antenna assembly, but it will be appreciated that a common antenna length, for example, L1, can be utilized while still maintaining the enhanced band properties of the device.

Each of the radiative elements266-268have a length within a second range of lengths associated with a second characteristic frequency. For example, the First radiative element266can have a length, L2, tuned to be receptive to the second characteristic frequency and each of the second and third radiative elements267and268can have a length within an approximately ten percent variance of the length of the first element. In one implementation, the antenna assembly250is designed to operate the three ISM bands of radio frequencies, including a first frequency band around 912-928 MHz, a second frequency band around 2.4 GHz, and a third frequency band around 5-6 GHz. The three curvilinear ground elements can be cut to lengths associated with the first and lowest frequency band, such that the first curvilinear ground element262can have a length of approximately 5.81 inches, the second curvilinear ground element263can have a length of approximately 5.63 inches, and the third curvilinear ground element264can have a length of approximately 6 inches. The lengths of the second set of radiative elements266-268can be cut to tune the antenna to the second frequency band, such that the first radiative element266can have a length of approximately 0.81 inches, the second radiative element267can have a length of approximately 0.69 inches, and the third radiative element268can have a length of approximately 0.94 inches. Capacitive and inductive interaction among the various elements262-264and266-268increase the sensitivity of the antenna250in the third frequency band. Each of the radiative elements266-268can have a diameter of approximately one-sixteenth of an inch.

FIG. 9illustrates a sixth exemplary implementation of an antenna assembly300in accordance with an aspect of the present invention. The illustrated antenna assembly300comprises a driven antenna assembly302located on a first side of an imaginary plane304, and a ground reference306located at the imaginary plane or on a second side of the imaginary plane. In the illustrated implementation, the ground reference306is illustrated as planar, but it will be appreciated that other configurations of the ground plane can be utilized within the illustrated antenna assembly. The driven antenna assembly302can be driven by an antenna feed that is electrically connected to the driven antenna assembly approximately at the imaginary plane304.

The antenna feed308can include an SMA (or similar) coaxial connector and a transmitter/receiver circuit board (not shown). The SMA connector and board can be electrically connected together by a length of coaxial cable. The SMA connector allows a center conductor of the coaxial cable to electrically connect the driven antenna assembly302and allows a ground braid of the coaxial cable to electrically connect to the ground reference306. A dielectric material can be used to electrically insulate the center conductor and the driven antenna assembly302from the ground reference306.

The driven antenna assembly302comprises three radiative elements312-314that extend outward from a common apex320. The driven antenna assembly302and its constituent elements312-314are formed from a conductive material. The radiative elements312-314are electrically connected to the antenna feed308and one another at respective first ends at the apex320. The radiative elements312-314comprise respective first linear segments332-334that extend away from the apex320at an acute angle relative to the imaginary plane304, and respective second linear elements336-338that extend in a direction substantially parallel to the imaginary plane. Each first segment332-334is connected to its associated second segment336-338at an acute angle at a vertex346-348. In accordance with an aspect of the invention, each second linear segment342-344can extend from their associated vertex346-348to the vertex of another radiative element312-314, such that each radiative element has a second end terminating on the vertex of another radiative element, forming the outline of an inverted pyramid. By bending the radiative elements312-314into the illustrated pyramidal shape in this manner, an additional degree of capacitive and inductive coupling is provided such that the pyramidal shape allows for a significant reduction in the vertical profile of the antenna300.

FIG. 10illustrates a seventh exemplary implementation of an antenna assembly350in accordance with an aspect of the present invention. The illustrated antenna assembly350comprises a driven antenna assembly352and an SMA connector356having a center lead and a shield element that serves as a ground reference. The driven antenna assembly352comprises three radiative elements362-364that extend outward from a common apex370. The driven antenna assembly352and its constituent elements362-364are formed from a conductive material. The radiative elements362-364are electrically connected to the center lead358and one another at respective first ends at the apex370. The radiative elements362-364comprise elliptical loops that extend away from the apex370and loop back to terminate on the shield element of the SMA connector356. The radiative elements362-364are generally substantially circular, but can be compressed to reduce the horizontal footprint of the antenna. In accordance with an aspect of the invention, the antenna assembly350is designed with a characteristic lower bound frequency, and each radiative element362-364has a length approximately equal to a wavelength associated with the characteristic lower bound frequency. In the illustrated example, the characteristic lower bound frequency is around 300 MHz, and the length of each radiative element362-364is approximately 40 inches, allowing the antenna350to be sensitive across at least dual frequency bands of 310-325 MHz and 915-917 MHz.

FIG. 11illustrates a cross sectional view of a parabolic reflector dish400for directing radiation received at and transmitted from an omni-directional enhanced band antenna402to provide directionality to the antenna in accordance with an aspect of the present invention. The parabolic reflector dish400is formed from a conductive material and shaped as a circular paraboloid that can be represented by the revolution of a parabola around its axis, wherein the parabola having dimensions as described herein, can be described by the formula:

The cross-sectional view represents a center plane in the parabolic reflector400, wherein the center plane is a plane that encompasses an apex404of the parabolic reflector and a focal point406of the parabolic reflector. It will be appreciated that while there are a number of planes that encompass these two points, the parabolic reflector400is a circular paraboloid, and thus all of these planes will produce substantially identical cross-sectional views. In the cross sectional plane, a horizontal axis represents the y variable and a vertical axis represents the x variable, with the origin at the apex404of the parabolic reflector400,

In accordance with an aspect of the present invention, the parabolic reflector dish400is configured such that the focal depth408of the dish is well within a volume defined by the dish. For example, the parabolic reflector dish400can be continued past the focal point406to a point where a line tangent to the edge412of the dish forms an angle between fifty-five and sixty degrees with an axis of dish. By configuring the dish to have a focal point within the volume of the dish, significant electromagnetic energy that might otherwise escape around the edge412of the dish is redirected along the axis of the dish. Accordingly, the directionality, and corresponding gain, of the enhanced band antenna402located at the focal point406of the dish400can be significantly increased, greatly enhancing the utility of the antenna for point-to-point communications.

In the illustrated implementation, the parabolic reflector400is configured for a wide band antenna402sensitive to a frequency band between 2.4 GHz and 11 GHz. The focal point406of the dish is located at point six inches from the apex. The parabolic reflector dish400has a focal point radius416of twelve inches. The dish has a depth418of thirteen and one-half inches, and a maximum radius420of eighteen inches. Using the illustrated parabolic reflector dish, a gain of the order of 25-35 dBi can be realized.

FIG. 12illustrates a cross-sectional view of a folded sheet reflector450for providing directionality to an omni-directional enhanced band antenna assembly452in accordance with an aspect of the present invention. The folded sheet reflector450is folded along a vertex454and extends from the vertex in two substantially planar conductive members456and458. In the illustrated implementation, the folded sheet reflector450is folded at an angle of approximately ninety degrees at the vertex454and each planar is substantially rectangular, extending to a length of twelve inches with a width of seven inches. In accordance with an aspect of the present invention, the antenna assembly452is placed immediately adjacent to a center point460of the vertex, such that a ground reference462of the antenna is physically and electrically connected to the folded sheet reflector450. It will be appreciated that the planar members456and458can be slightly deformed near the vertex to accommodate the antenna assembly452. This electrical connection between the ground reference462and the folded sheet450substantially mitigates the effects of any mismatch in impedance at the antenna assembly, allowing for significant increase of the directionality, and corresponding gain, of the enhanced band antenna452, greatly enhancing the utility of the antenna for point-to-point communications. Using the illustrated folded sheet reflector450, a gain of the order of 10 dBi can be realized.