Abstract:
A wide-bandwidth antenna with antenna pattern control includes a radiator and a feed. The radiator includes two or more volumetric radiating elements. The feed includes two or more feed units, the feed units configured to provide wave signals to the volumetric radiating elements. The feed units provide an independent signal for each radiating element. The wave signals can be fed out of phase to each other. Depending on the dielectric filler inside the volume of the antenna and the phase shift between feeds, the pattern can be modified electronically leading to pattern control. The radiating elements are spaced at a distance at least one order of magnitude smaller than half of an operational wavelength of the antenna. At least one electrically conductive element of the antenna is capable of conducting a current that generates a magnetic field. The magnetic field lowers the total reactance of the antenna, thereby resulting in enhanced performance of the antenna in terms of bandwidth, gain, and pattern control. The volumetric design allows miniaturization of the antenna.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part application of, and claims priority to and the benefit of, U.S. patent application Ser. No. 12/501,973, filed on Jun. 13, 2009, which is expressly and entirely incorporated herein by reference. 
     
    
     STATEMENT OF GOVERNMENT INTEREST 
       [0002]    This invention was made with government support under W15QKN-08-C-0050 awarded by U.S. Army under Small Business Innovation Research (SBIR). The government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    This invention relates to antennas, and more specifically to volumetric antennas that achieve pattern control and wide bandwidth while occupying a small volume. 
       BACKGROUND OF THE INVENTION 
       [0004]    The performance of an antenna can be defined in terms of its gain, bandwidth, antenna pattern, and radiation efficiency. A gain of an antenna can be defined as the ratio between the radiation intensity of the antenna in a certain direction and the radiation intensity that would be obtained if the power accepted by the antenna were radiated isotropically. A bandwidth of an antenna can be defined as a range of frequencies, on either side of a center frequency (usually the resonance frequency for a dipole) where the matching antenna characteristics (the input impedance) are within an acceptable value. The antenna fractional bandwidth is the ratio of the bandwidth to its center frequency (percentage). When the bandwidth is larger than 100% it is measured as the ratio of the upper frequency to the lower frequency of the band. For example, the 2:1 antenna has a one octave bandwidth. 
         [0005]    An antenna radiation pattern is a graphical representation of the radiation properties of the antenna as a function of space coordinates. The radiation efficiency of an antenna is a measure of how well an antenna converts the radio-frequency power accepted at its terminals into radiated power. Efficiency depends on the antenna impedance matching. To avoid signal reflections (and therefore losses) at the interface between a transmission line and the antenna it is necessary to transform the antenna input impedance to the same value as the transmission line characteristic impedance. This process is called impedance matching. A type of impedance matching is LC matching. An LC network match consists of a network of inductors and capacitors that are used to transform the antenna impedance into the feed line impedance. 
         [0006]    Impedance is composed of resistance and reactance. Reactance is a measure of the opposition of capacitance and inductance to current. There are two types of reactance: capacitive reactance and inductive reactance. Capacitive reactance is inversely proportional to the frequency and the capacitance. Inductive reactance is proportional to the frequency and the inductance. Total reactance is a function given by the difference between the inductive reactance and the capacitive reactance. In small dipole antennas (small compare to the quarter wavelength) a high capacitive reactance is observed. To reduce this effect, inductive elements are introduced in the antenna design. 
         [0007]    Antennas in the prior art often include dipole antennas, helical antennas, loop antennas, and parabolic antennas.  FIG. 1A  shows a dipole antenna in the prior art. The dipole antenna can be used in communications. The dipole antenna  100  includes two conductors (e.g., a first pole  110 , second pole  120 ) and an antenna feed  150  (e.g., a center feed element). Electric current flow in the dipole antenna from the feed generates a first current flow  115  in the first pole  110  of dipole antenna  100 , and second current flow  125  in the second pole  120  of dipole antenna  100 . A common dipole is the half-wave dipole (e.g., a wire of total length equal to half the wavelength of operation or operational wavelength). The theoretical maximum gain of a half-wave dipole is 2.15 dB. The fundamental 10-12% bandwidth of a straight half-wavelength cylindrical dipole antenna is a weak function of the ratio of the length of the dipole to its diameter and the reactance as function of frequency. To fit in the small space available, and to comply with stealth requirements, the dipole antenna has to be reduced in size and become electrically small antennas that do not work at resonance (non-resonant dipole). Dipoles that are designed to be much smaller than the wavelength of operation have a very low radiation resistance and high capacitive reactance that makes them inefficient. The (matched) bandwidth of small dipoles drastically decreases from 10-12% to 0.1% and lower. 
         [0008]      FIG. 1B  shows a prior art helical antenna  130 . A helical antenna  130  has a conducting wire  131  wound in the form of a helix. Helical antennas  130  can operate in one or two principal modes: normal mode (broadside) or axial mode (end-fire). In the normal mode, the dimensions of the helix are small compared with the wavelength. The far field radiation pattern is similar to an electrically short dipole or monopole. Normal mode helical antennas  130  tend to radiate inefficiently and are typically used for mobile communications where reduced size is a critical factor. Helical antennas  130  possess erratic impedance behavior at low frequencies, especially for short helixes with many turns operating in the normal mode. In the axial mode, the helix dimensions are at or above the wavelength of operation. The helical antenna  130  produces circular polarization. Antenna size makes helical antennas  130  unwieldy for low frequency operation, so they are commonly employed only at frequencies ranging from VHF (e.g., about 30 MHz to about 300 MHz) up to microwaves. The axial mode helical antenna has a directive antenna beam, not appropriate for communications, where a wide beam is required. The helical antenna has about 3-15% bandwidth. 
         [0009]      FIG. 1C  shows a prior art loop antenna  140 . The loop antenna  140  is an alternative solution to the optimization of the volume occupied for RF communications. Even though the loop antenna  140  is overall smaller than a whip antenna resonating at the same frequency (e.g., the diameter of the loop is about λ/10), it is not practical since it can require assembly, has a very narrow bandwidth, and works well only when very close to the ground. The resonant loop has 10-15% bandwidth. The magnetic loop, however, poses serious health risks for the human body when exposed to its concentrated radiated field. 
         [0010]      FIG. 1D  shows a prior art parabolic antenna  145 . The parabolic dish antenna  145  has a gain that is mainly a function of its diameter  146  and operating frequency. The parabolic antenna has a narrow beam (antenna pattern) and is desirable for applications that require directive antennas and high gain. For instance, approximate gain and a 3 dB beam angle of a 3 meter parabolic dish are 22 dB at 500 MHz with a 3 dB beam angle of 14 degrees, and 28 dB at 1 GHz with a 3 dB beam angle of 7 degrees. The bandwidth of the parabolic dish antenna  145  is equal to the bandwidth of the feeding element (e.g., the horn). The parabolic dish antenna  145  has good gain and wide bandwidth, but is bulky and needs precise mechanical steering for proper pointing. 
       SUMMARY OF THE INVENTION 
       [0011]    The invention features a wide bandwidth, compact volumetric antenna with antenna pattern control. A volumetric antenna is one that is not planar or linear, but rather occupies a volume. A volumetric antenna comprises a radiator and a feed. The radiator in this invention occupies a volume and comprises two or more radiating elements closely spaced to each other at a distance d&lt;&lt;λ/2. The wavelength, λ, can be defined as λ=v/f (e.g. speed divided by frequency). The symbol “&lt;&lt;” indicates “much less than” e.g. that the term on the left is at least one order of magnitude smaller than the term on the right. Therefore, a distance d&lt;&lt;λ/2 means that the distance between radiating elements in the antenna radiator is λ/20 or smaller (e.g. d=λ/100 or d=λ/500). The radiating elements are designed and placed in such a way as to achieve a certain pattern interference and optimize the magnetic field inside the volume occupied by the antenna and increase the intrinsic inductive reactance of the antenna. 
         [0012]    A feed can comprise two or more feeding units. Each feed can feed one of the radiating elements of the antenna radiator independently. Each feed unit can provide each radiating element with an independent excitation signal having an independent magnitude and/or phase. Depending on the relative magnitude and phase of the feed units and certain dielectric constant filler, the total antenna radiation pattern can be modified (or deformed) both in direction and intensity. The axis of rotation and/or the magnitude of the directivity can also be changed. 
         [0013]    Advantages of a dipole antenna (e.g., feasible at very long wavelengths) can be retained but with better performance than traditional dipoles (e.g., better matching, wider bandwidth, and occupying a smaller volume). The volumetric dipole antenna allows the antenna radiation pattern to be modified (e.g. controlled). Pattern control can be achieved by changing the shape and/or intensity of the antenna pattern. In the present invention pattern control can be achieved by specifying (i) a specific shape for the radiator; (ii) a number of radiating elements within the radiator; (iii) a relative position and/or distance between radiating elements in the radiator; (iv) a magnitude of the signal provided by the feeding units; (v) a phase angle between the signals provided by the feeding units; and/or (vi) a dielectric constant for a material lining the radiating elements. 
         [0014]    The antenna can occupy a smaller volume to allow miniaturization while achieving wider bandwidth, pattern control, and low manufacturing cost as compared to state-of-the-art antennas. The volume of a volumetric dipole can be more efficiently used than in a traditional resonant dipole antenna. A volumetric dipole can be designed to be shorter than, for example, traditional dipole antennas at the same operating frequency. The wide bandwidth, compact volumetric antenna can be designed to be, for example, up to five times shorter than a conventional HF whip antenna. 
         [0015]    Capabilities of the present invention include a more stable antenna radiation pattern over the bandwidth and greater bandwidth than conventional dipole antennas in less than, for example, half the linear dimension. A 3:1 or even 4:1 bandwidth can be achieved for the high-performance compact volumetric antenna with ground plane. Applications for the technology include, for example, RF communications (e.g., on a soldier&#39;s manpack, on land vehicles, on UAV&#39;s, on munitions for HF, UHF and VHF communications), enhanced performance/safety for cell phones, and high definition digital TV. A directive antenna pattern can be obtained using an array of multiple volumetric antennas. Antenna arrays can be used in High Power Microwave systems and platforms (e.g., for directed energy applications to produce high-density bursts of energy capable of damaging or destroying nearby electronics). The technology has excellent performance in the HF frequency band (e.g., High Frequency of about 3 MHz to about 30 MHz) and in the VHF frequency band (e.g., about 30 MHz to about 300 MHz), where the large wavelengths (e.g., between about 100 m and about 1 m) require large antenna sizes for classic antennas. The high performance compact volumetric antenna can be scaled to work at other frequencies as well. 
         [0016]    An antenna having one compact volumetric radiator comprising multiple radiating elements can be distinguished from an antenna array comprising multiple radiators by the distance between radiating elements. In an antenna array the relative spacing d between radiators is approximately d=λ/2. This distance or spacing can be optimized differently to achieve different performance goals and can create a design tradeoff among at least the following: (i) the directivity of an antenna array can increase as d grows larger; (ii) a larger d can imply a larger antenna array size and/or cost of manufacturing; (iii) to avoid blind spots, d can be made greater than an operational wavelength of the antenna array; (iv) to minimize the effects of mutual coupling, e.g. element pattern distortion, the radiator impedance variation with scan angle, and/or polarization variation with scan angle, d can be greater than one quarter of the operational wavelength; (v) to avoid grating lobes, e.g., instances of strong radiation in unintended directions, d can be less than one half of the operational wavelength. 
         [0017]    As a compromise, the spacing between radiators in an antenna array is traditionally chosen to be approximately half of the operational wavelength. An array of radiators at approximate distance d=λ/2 from each other provides a pencil beam (e.g. highly directive) function of the array aperture (size) and high gain. The gain and directivity are functions of the antenna array aperture, e.g. the array total size L_Array, which is a multiple of the radiator size L_rad and a multiple of the spacing between elements, λ/2. In other words an antenna array total linear dimension is much larger than its single element (radiator) size being a multiple of N (number of elements) as L_Array=N*L_rad+N*λ/2. 
         [0018]    The present invention is not an array of multiple volumetric radiators (dipoles) in the sense known in literature because the present invention is composed of one single radiator made of multiple closely spaced radiating elements that occupy approximately the same volume as an antenna having a single radiator composed of a single volumetric radiating element. An antenna array, on the contrary, is more than N times larger than the size of the single radiator plus N times the spacing between elements. The present invention can include a radiator comprising multiple radiating elements located at distance d&lt;&lt;λ/2, e.g. d is at least one order of magnitude smaller than λ/2. Because of the close proximity of the radiating elements, in the far field the antenna is perceived as having a single radiating element, even though the radiator is composed of multiple radiating elements. Moreover, its antenna pattern can have a toroidal shape as in conventional dipoles and not be highly directive as an array. On the other hand, it is possible to design an array of volumetric dipoles (i.e. and array of radiators each composed of multiple radiating elements) to achieve narrow band as for conventional dipole elements. 
         [0019]    The present antenna can include a radiator composed of multiple radiating elements spaced at a distance much less than half of the operational wavelength (much less refers to less than an order of magnitude of a quarter wavelength). For instance the distance could be a fortieth of the wavelength or less. One or more radiating elements are provided with a signal (e.g. a wave signal) via a feeding unit. An antenna feed can comprise one or more feeding units. Each radiating element can be fed with a separate signal that has a different amplitude and/or phase. The antenna can have advantages for antenna pattern control, e.g. as demonstrated in greater detail below with respect to  FIG. 9B . A compact volumetric dipole having one radiator composed of multiple closely spaced radiating elements provides a radiation pattern similar to a dipole composed of one single radiating element, but its pattern can be modified: for example, it can be rotated around a different axis of symmetry; it can be deformed; and/or its intensity can be varied (e.g. increased or reduced). 
         [0020]    In one aspect, the invention features a wide-bandwidth antenna (e.g., a “rib-dipole” antenna) that includes a first pole formed by a first conductive member, a second pole formed by a second conductive member and an antenna feed between the first conductive member and the second conductive member. The antenna also can include at least one electrically conductive element. The electrically conductive element can include a surface having a portion that is electrically connected to the first conductive member or the second conductive member. The electrically conductive element can also extend from the first conductive member or the second conductive member. The at least one electrically conductive element can be capable of conducting a current that generates a magnetic field that lowers a total reactance of the antenna. 
         [0021]    At least one electrically conductive element can be attached/connected to (e.g., adjacent) the first conductive member or the second conductive member. In some embodiments, the portion of the surface of at least one electrically conductive element is connected/attached to, and extends laterally from, the first conductive member or the second conductive member. The electrically conductive element can be curvilinear and can include a contoured surface. In some embodiments, a portion of the contoured surface is connected to, and extends laterally from, the first conductive member or the second conductive member. In some embodiments, the antenna is “conformal.” The antenna can conform to any shape/surface (e.g., an irregular surface) on a body. By way of example, the antenna can conform to an aircraft wing or a vehicle body. 
         [0022]    The first conductive member and the second conductive member can be metal plates/sheets/blades. In some embodiments, the electrically conductive element is a planar electrically conductive element that is connected to, and extends from, the first conductive member or the second conductive member. The electrically conductive element can be disposed at an angle (e.g., substantially perpendicular) relative to the first conductive member or the second conductive member. 
         [0023]    In some embodiments, the antenna also includes a third pole formed by a third conductive member and a fourth pole formed by a fourth conductive member. The first conductive member, the second conductive member, the third conductive member, the fourth conductive member and the electrically conductive element(s) occupy a volume. The volume can be, for example, a cylindrical volume, a conical volume, a bi-conical volume, a sphere, a pyramid or a parallelepiped. 
         [0024]    The first conductive member can be substantially co-axial to the second conductive member. In some embodiments, the magnetic field generated by the electrically conductive element is substantially parallel to a longitudinal axis of a volume formed by the antenna (e.g., the first conductive member, the second conductive member and electrically conductive element(s)). 
         [0025]    The electrically conductive element(s) can be a metal plate or metal sheet. For example, the electrically conductive element can be a closed ring, a hollow cylinder, a cone, a sphere, a strip, a fractal strip, a slotted strip or include any combination/variation thereof. 
         [0026]    In some embodiments, the antenna includes a first, second and third electrically conductive element. The electrically conductive elements can be each spaced at a distance relative to one another. The distance can be, for example, constant, linear, increasing, decreasing, logarithmic, randomly distributed, or any combination/variation thereof. 
         [0027]    The length of the antenna (e.g., the largest dimension of the volume occupied by the antenna) can be greater than a width, thickness, or radial width of the antenna. 
         [0028]    In another aspect, the invention features a wide-bandwidth antenna (“rib-dipole”). The antenna can include a first pole formed by a first conductive plate, a second pole formed by a second conductive plate and an antenna feed between the first conductive plate and the second conductive plate. The antenna can also include two or more planar electrically conductive sheets that are electrically connected to, and disposed substantially perpendicular from, or at an angle from, the first conductive plate. The electrically conductive sheets(s) can be capable of conducting a current generating a magnetic field that lowers a total reactance of the antenna. 
         [0029]    In another aspect, the invention features a wide-bandwidth antenna (“rib-dipole”) that includes a first conductive member, a second conductive member, and an antenna feed between the first conductive member and the second conductive member. The antenna can also include at least two electrically conductive components disposed along the first conductive member or the second conductive member. The electrically conductive components each include respective surfaces each having a portion electrically connected to, and extending from, the first conductive member or the second conductive member. The electrically conductive components are capable of conducting a respective current that generates a respective magnetic field that increases the inductive reactance and therefore lowers an overall total reactance of the antenna. 
         [0030]    In some embodiments, the electrically conductive components extend laterally from the first conductive member or the second conductive member. The electrically conductive components can be curvilinear and include respective contoured surfaces, each having a portion connected to, and laterally extending from, the first conductive member or the second conductive member. The electrically conductive components can each have different lengths, widths, or thicknesses. 
         [0031]    The antenna can include two poles formed by a first metal plate and a second metal plate. The electrically conductive components can be planar electrically conductive sheets connected to, and substantially perpendicular to, the first metal plate and/or the second metal plate. In some embodiments, the antenna is substantially parallel relative to a ground plane. 
         [0032]    In some embodiments, the antenna includes a third conductive member and a fourth conductive member. The first conductive member, the second conductive member, the third conductive member, the fourth conductive member and the at least two electrically conductive components can occupy a volume. The volume can be, for example, a cylindrical volume, a conical volume, a bi-conical volume, a sphere, a pyramid, or a parallelepiped. 
         [0033]    The electrically conductive components can include a closed ring, a hollow cylinder, a curvilinear strip, a fractal strip, a slotted strip or any combination/variation thereof. The electrically conductive components can be disposed at an angle relative to a shared longitudinal axis of the first conductive member and the second conductive member (e.g., where the first conductive member and the second conductive member are substantially coaxial). 
         [0034]    In some embodiments, the antenna also includes a third electrically conductive component and the electrically conductive components are each spaced at a distance relative to one another. The distance can be, by way of example, constant, linear (e.g., linearly increasing or decreasing), increasing, decreasing, logarithmic, randomly distributed or any combination/variation thereof. 
         [0035]    In yet another aspect, the invention features a method for transmitting or receiving electromagnetic energy. The method can include the step of providing at least a first current flow in a first pole of an antenna and generating a second current flow in at least one electrically conductive element from the first current flow in the first pole. The at least one electrically conductive element can include a surface having a portion electrically connected to, and extending from, the first pole. The method can also include the step of generating a magnetic field from the second current flow in the at least one electrically conductive element, where the magnetic field lowers an intrinsic reactance of the antenna. 
         [0036]    In some embodiments, the at least one electrically conductive element is curvilinear and includes a contoured surface. A portion of the contoured surface can be electrically connected to, and extend laterally from, the first pole. In some embodiments, the electrically conductive element is a planar electrically conductive sheet that is electrically connected to, and substantially perpendicular to, the first pole. 
         [0037]    In another aspect, the invention features a wide-bandwidth antenna. The antenna includes a first pole formed by a conductive member and an antenna feed electrically connected to the conductive member. The antenna can also include at least one electrically conductive element configured to conduct a current from the first pole that generates a magnetic field that lowers a total reactance of the antenna. A portion of a surface of the electrically conductive element can be electrically connected to, and extend laterally from, the conductive member. 
         [0038]    In some embodiments, the at least one electrically conductive element includes a contoured surface having a portion electrically connected to, and extending laterally from, the conductive member. 
         [0039]    The first pole and the antenna feed can form a monopole antenna (e.g., together with the electrically conductive elements forming a “rib-monopole”). In some embodiments, the antenna also includes a second pole formed by a second conductive member. The second conductive member can be substantially coaxial to the conductive member. 
         [0040]    In another aspect, the invention features a system for transmitting and receiving electrical signals. The system can include a power source and an antenna. The antenna can include a first conductive member configured to conduct a first current from the power source and an antenna feed electrically coupled to the first conductive member. The system can also include at least one electrically conductive component including a surface having a portion electrically connected to, and extending from, the first conductive member. The electrically conductive component is capable of conducting a second current generated by the first current in the first conductive member and the second current can produce a corresponding magnetic field that lowers a total reactance of the antenna. 
         [0041]    In some embodiments, the system also includes a second conductive member configured to conduct a third current from the power source. The second conductive member can be electrically coupled to the antenna feed. The system can also include a second electrically conductive component including a surface having a portion electrically connected to, and extending from, the second conductive member. The second electrically conductive component can be configured to conduct a fourth current generated by the third current. The fourth current can produce a corresponding magnetic field that lowers the total reactance of the antenna. 
         [0042]    In another aspect, the invention features a wide-bandwidth antenna including a radiator and a feed. The radiator includes a first volumetric radiating element and a second volumetric radiating element. The feed includes a first feed unit and a second feed unit. The first feed unit can be configured to provide a first wave signal to the first volumetric radiating element. The second feed unit is configured to provide a second wave signal to the second volumetric radiating element. The second wave signal is out of phase to the first wave signal. The first and second volumetric radiating elements are spaced at a distance at least one order of magnitude smaller than half of an operational wavelength of the antenna. 
         [0043]    In some embodiments, the first volumetric radiating element occupies a first half cylinder volume. In some embodiments, the second volumetric radiating element occupies a second half cylinder volume. In some embodiments, a longitudinal axis of the first half cylinder volume is parallel or substantially parallel to a longitudinal axis of the second half cylinder volume. 
         [0044]    In some embodiments, the first wave signal and the second wave signal are about 45 degrees out of phase to one another, or optionally about 0 to 45 degrees out of phase to one another. In some embodiments, the first wave signal and the second wave signal are 90 degrees out of phase to one another, or optionally about 45 to 90 degrees out of phase to one another. In some embodiments, the first wave signal and the second wave signal are 135 degrees out of phase to one another, or optionally about 90 to 135 degrees out of phase to one another. In some embodiments, the first wave signal and the second wave signal are 233 degrees out of phase to one another, or optionally about 180 to 233 degrees out of phase to one another. In some embodiments, the first wave signal and the second wave signal are 180 degrees out of phase to one another, or optionally about 135 to 180 degrees out of phase to one another. 
         [0045]    In some embodiments, the antenna pattern is toroidal and has an axis of rotation along an axis perpendicular to the longitudinal axes and an axis defined by the first feed and the second feed. In some embodiments, the first and second volumetric radiating elements are filled and/or lined with a dielectric material. In some embodiments, the dielectric material has a dielectric constant value of about 1. In some embodiments, the dielectric material has a dielectric constant value of about 10. In some embodiments, the dielectric material has a dielectric constant value of about 20. 
         [0046]    In another aspect, the invention features a method of controlling the radiation pattern of an antenna. The method includes feeding a first wave signal to a first radiating element of the antenna radiator. The method includes feeding a second wave signal to a second radiating element of the antenna radiator. The second wave signal is out of phase relative to the first wave signal. In some embodiments, a dielectric material is provided to line at least one of the first or second radiating elements, the dielectric material characterized by a dielectric constant value. 
         [0047]    In some embodiments, the first wave signal and the second wave signal are about 45 degrees out of phase with respect to one another, or optionally about 0 to 45 degrees out of phase with respect to one another. In some embodiments, the first wave signal and the second wave signal are 90 degrees out of phase with respect to one another, or optionally about 45 to 90 degrees out of phase with respect to one another. In some embodiments, the first wave signal and the second wave signal are 135 degrees out of phase with respect to one another, or optionally about 90 to 135 degrees out of phase with respect to one another. In some embodiments, the first wave signal and the second wave signal are 180 degrees out of phase with respect to one another, or optionally about 135 to 180 degrees out of phase with respect to one another. In some embodiments, the first wave signal and the second wave signal are 233 degrees out of phase with respect to one another, or optionally about 180 to 233 degrees out of phase with respect to one another. In some embodiments, the dielectric material has a dielectric constant value of about 1, optionally about 0.1 to 9.9. In some embodiments, the dielectric material has a dielectric constant value of about 10, optionally about 10 to 99. In some embodiments, the dielectric material has a dielectric constant value of about 100, optionally about 10 to 999. 
         [0048]    In another aspect, the invention features a system for transmitting and receiving electrical signals. The system includes a power source. The system includes an antenna comprising a radiator. The radiator includes a first radiating element configured to conduct a first current from the power source. The radiator includes a first feed electrically coupled to the first radiating element. The radiator includes a second radiating element configured to conduct a second current from the power source. The radiator includes a second feed electrically coupled to the second radiating element. The second wave signal is out of phase to the first wave signal. The first and second volumetric radiating elements are spaced at a distance at least one order of magnitude smaller than half of an operational wavelength of the antenna. 
         [0049]    Other aspects and advantages of the invention can become apparent from the following drawings and description, all of which illustrate the principles of the invention, by way of example only. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0050]    The advantages of the invention described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
           [0051]      FIG. 1A  depicts a dipole antenna in the prior art. 
           [0052]      FIG. 1B  depicts a helical antenna in the prior art. 
           [0053]      FIG. 1C  depicts a loop antenna in the prior art. 
           [0054]      FIG. 1D  depicts a parabolic antenna in the prior art. 
           [0055]      FIG. 2A  is a schematic of a volumetric dipole antenna including a single radiator comprising a single radiating element. 
           [0056]      FIG. 2B  is a schematic of a volumetric monopole antenna. 
           [0057]      FIG. 3  is a schematic of electric currents and magnetic fields in the antenna of  FIG. 2A , according to an illustrative embodiment of the invention. 
           [0058]      FIG. 4  is a schematic of a cylindrical volumetric antenna, according to another illustrative embodiment of the invention. 
           [0059]      FIG. 5A  a schematic of a half-cylinder volumetric antenna, according to yet another illustrative embodiment of the invention. 
           [0060]      FIG. 5B  is a schematic of a half-cylinder volumetric antenna, according to an illustrative embodiment of the invention. 
           [0061]      FIG. 6A  is a schematic of a radiating element with open and shortened curvilinear electrically conductive elements, according to an illustrative embodiment of the invention. 
           [0062]      FIG. 6B  is a schematic of a radiating element with curvilinear electrically conductive elements of varying sizes, according to an illustrative embodiment of the invention. 
           [0063]      FIG. 7  is a schematic of a compact volumetric radiating element over a ground plane, according to an illustrative embodiment of the invention. 
           [0064]      FIG. 8  is a schematic of a cylindrical volumetric antenna comprising a radiator having two radiating elements and a feed having two feeding units, according to an illustrative embodiment of the invention. 
           [0065]      FIG. 9A  shows an antenna pattern of a half-cylinder volumetric antenna, according to an illustrative embodiment of the invention 
           [0066]      FIG. 9B  shows an antenna pattern for a cylindrical volumetric antenna, according to an illustrative embodiment of the invention. 
           [0067]      FIG. 10A  is a schematic of a cylindrical volumetric antenna according to an illustrative embodiment of the invention. 
           [0068]      FIG. 10B  is a schematic of a cylindrical volumetric antenna, comprising a cylindrical radiator having three radiating elements and a feed having three feeding units, according to another illustrative embodiment of the invention. 
           [0069]      FIG. 10C  is a schematic of a cylindrical volumetric antenna, comprising a cylindrical radiator having four radiating elements and a feed having four feeding units, according to yet another illustrative embodiment of the invention. 
           [0070]      FIG. 11A  is a schematic of a bi-conical volumetric antenna, comprising a bi-conical radiator having two radiating elements and a feed having two feeding units, according to an illustrative embodiment of the invention. 
           [0071]      FIG. 11B  is a schematic of a bi-conical volumetric antenna, comprising a bi-conical radiator having three radiating elements and a feed having three feeding units, according to another illustrative embodiment of the invention. 
           [0072]      FIG. 11C  is a schematic of a bi-conical volumetric antenna, comprising a bi-conical radiator having four radiating elements and a feed having four feeding units, according to another illustrative embodiment of the invention. 
           [0073]      FIG. 12A  is a schematic of a spherical volumetric antenna, comprising a spherical radiator having two hemispherical-surface radiating elements and a feed having two feeding units, according to an illustrative embodiment of the invention. 
           [0074]      FIG. 12B  is a schematic of a spherical volumetric antenna, comprising a spherical radiator having three radiating elements and a feed having three feeding units, according to another illustrative embodiment of the invention. 
           [0075]      FIG. 12C  is a schematic of a spherical volumetric antenna, comprising a spherical radiator having four radiating elements and a feed having four feeding units, according to yet another illustrative embodiment of the invention. 
           [0076]      FIG. 13  shows a further embodiment of an array of volumetric antennas composed of non-curvilinear high performance compact volumetric radiators, according to an illustrative embodiment of the invention. 
           [0077]      FIG. 14  shows a volumetric dipole antenna having a radiator comprising two differentially fed radiating elements, according to an illustrative embodiment of the invention. 
           [0078]      FIGS. 15A-15F  show simulations of radiation patterns in the azimuthal plane for the antenna shown in  FIG. 14 , according to an illustrative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0079]    A high performance, compact volumetric antenna (e.g., “rib-dipole” or “rib-monopole” antenna) has the advantages of a traditional dipole antenna (e.g., dipole  100  as shown in  FIG. 1A ), but with higher performance capabilities. Advantages of a rib-dipole/monopole antenna include, for example, a monotonic, predictable and smooth impedance curve. Another advantage is the lack of erratic impedance behavior at low frequencies (e.g., as compared to the helical antenna as shown in  FIG. 1B ). The volumetric dipole/monopole antenna is intrinsically better matched over a wider band as compared to small helical antennas in the prior art. The rib-dipole antenna can have a pattern that can be the same pattern of a traditional dipole antenna, regardless of size. In contrast, the helical antenna changes its pattern from broadside to end-fire when frequency increases. Therefore, the rib-dipole/monopole antenna can be used for both small and intermediate frequencies (e.g., over a wider bandwidth) in contrast to the helical antenna. As with a traditional dipole antenna, the rib-dipole antenna can be a high-impedance load at low frequencies and can also be used as a radiating antenna (e.g., as compared to a small loop antenna as shown in  FIG. 1C , which is a low-impedance load that cannot be used as a radiating antenna.) 
         [0080]    A traditional small dipole antenna (e.g., dipole  100  of  FIG. 1A ), however, has a large capacitive reactance, X C  that reduces the efficiency of the antenna. 
         [0000]    
       
         
           
             
               
                 
                   
                     X 
                     C 
                   
                   = 
                   
                     
                       - 
                       
                         1 
                         
                           ω 
                            
                           
                               
                           
                            
                           C 
                         
                       
                     
                     = 
                     
                       - 
                       
                         1 
                         
                           2 
                            
                           
                               
                           
                            
                           π 
                            
                           
                               
                           
                            
                           f 
                            
                           
                               
                           
                            
                           C 
                         
                       
                     
                   
                 
               
               
                 
                   EQN 
                   . 
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0000]    where f=frequency (hertz, Hz), C=capacitance (farads, F). To improve the performance of traditional dipole antennas, the high capacitive reactance of dipoles can be reduced. 
         [0081]    The enhanced performance of the high performance compact volumetric antenna (e.g., the rib-dipole/monopole antenna) can be attributed to the additional magnetic fields produced by the antenna&#39;s specific geometric volumetric configuration. The additional magnetic fields are produced from electrically conductive components/element(s) disposed along the pole(s) of the antenna. The electrically conductive component/elements can be curved/curvilinear or straight. The electrically conductive component/elements are attached to the pole(s) of the antenna and can extend from the poles (e.g., laterally extend outwards, like ribs). Layers of an electrically conductive material (e.g., metal layers, such as a copper, brass, gold, carbon fibers, carbon nanotubes, etc.) can be disposed to form the shape of electrically conductive components/elements on to a dielectric cylinder, making the antenna affordable to manufacture, less sensitive to damage and to manufacturing uncertainties. The antenna can conform to any surface/shape of a body (e.g., can conform to an aircraft wing, vehicle body, etc.) These additional magnetic fields produce a desirable inductive reactance that lowers the total reactance of the antenna, which results in higher performance (e.g., wider bandwidth, better matching). The improved performance of the antenna  200  is attributed, at least in part, to its intrinsic large inductive reactance, X L : 
         [0000]        X   L   =ωL= 2π fL   λEQN. 2
 
         [0000]    where f=frequency (Hertz, Hz), L=inductance (henrys, H). A large inductive reactance (X L ) (e.g., from EQN. 2) can reduce the total reactance (X) of the antenna: 
         [0000]        X=X   L   −X   C   EQN. 3
 
         [0000]    and where  Z   A  is the antenna impedance: 
         [0000]          Z     A   =R+jX   EQN. 4
 
         [0000]    where R is the antenna radiation resistance and j is the imaginary unit. 
         [0082]    EQN. 3 above shows that the lower is the frequency, the higher is X C  and the lower is X L . The smaller the capacitance, the higher is X C . The smaller the inductance, the lower is X L . Therefore, at lower frequencies of the RF spectrum (e.g. HF range), traditional dipole antennas (e.g., of  FIG. 1A ) have increasing high intrinsic capacitive reactance, a large total reactance, and therefore worse performance than at higher frequencies. The inductive reactance to lower the total reactance (X) can be achieved by introducing electrically conductive component/elements that produce additional magnetic fields that increase the inductive reactance and lower the total reactance of the antenna (e.g., the total reactance can be, for example, 5-8 times smaller than that of a traditional dipole antenna at low frequencies). Similarly, the inductive reactance is larger than the inductive reactance of a traditional small dipole antenna (e.g. non-resonant). 
         [0083]      FIG. 2A  shows a schematic of a high performance compact volumetric antenna (e.g., a rib-dipole antenna). The antenna  200  includes a first pole  110 , second pole  120 , antenna feed  150  and electrically conductive component/elements  210  and  220 . Poles  110  and  120  can be formed from conductive members (e.g., a metal member) having the antenna feed  150  between the members. The antenna  200  can include at least one electrically conductive component/element. In this embodiment, the antenna  200  includes a first curvilinear electrically conductive component/element  210  and a second curvilinear electrically conductive component/element  220 . As noted above, the electrically conductive component/element  210  and  220  can conduct a current that generates a magnetic field that lowers a total reactance of the antenna  200 , thereby resulting in enhanced performance. Accordingly, the antenna  200  has advantages of a traditional dipole antenna but with greater performance (e.g., wide bandwidth), thereby allowing for more efficient use of space. 
         [0084]    The electrically conductive component/elements  210  and  220  extend from the first pole  110  and the second pole  120  (e.g., the electrically conductive component/elements do not surround/encompass the first pole  110  and the second pole  120 ). The electrically conductive component/elements  210  and  220  can extend laterally from the first pole  110  and second pole  120  (e.g., like conductive “ribs” pointing out from and disposed along the poles). In some embodiments, the electrically conductive component/elements  210  and  220  are adjacent poles  110  and  120 . Each electrically conductive component/element  210  and  220  can include a surface  211  and  222  (e.g., or a wall). For example, electrically conductive component/element  210  or  220  can be curvilinear and the surface/wall  211  and  222  can be a contoured surface. A portion of the surface/wall  211  and  222  can be connected/attached (e.g., electrically connected) to the first pole  110  and the second pole  120 . 
         [0085]    The first pole  110  and the second pole  120  can be substantially coaxial and share a common longitudinal axis  213 . In some embodiments, the electrically conductive component/elements  210  and  220  form a volume (e.g., a cylindrical volume) having a longitudinal axis  214  that is substantially parallel to the longitudinal axis  213  of the poles  110  and  120 . In some embodiments, the magnetic field generated by electrically conductive component/elements  210  and  220  are substantially parallel to the longitudinal axis  214 . 
         [0086]    In this embodiment, the electrically conductive component/elements  210  and  220  are curved (e.g., curve metal sheets/plates that are closed rings). However, in some embodiments, as shown in  FIGS. 7 and 13 , the electrically conductive components/elements are planar sheets/plates that are disposed along and connected to (e.g., electrically connected and/or attached) the dipole antenna. In this embodiment, the electrically conductive component/elements  210  and  220  are hollow cylinders. However, in other embodiments, the electrically conductive component/elements can be metal plates or metal sheets (e.g., a closed ring, a strip, a fractal strip, a slotted strip, or any combination thereof). This might simplify numerical modeling and lower the cost of fabrication. Furthermore, in this embodiment, antenna  200  includes two electrically conductive component/elements  210  and  220 . However, it is contemplated that an antenna can include any number of electrically conductive component/elements (e.g., one or more). Furthermore, in some embodiments, the electrically conductive component/elements  210  and  200  are disposed at an angle relative to the longitudinal axis  213 . 
         [0087]    In some embodiments, the antenna  200  is “conformal.” The antenna  200  can conform to any shape/surface (e.g., an irregular surface) on a body. By way of example, the antenna can conform to an aircraft wing or a vehicle body. 
         [0088]      FIG. 2B  shows a high performance compact volumetric antenna  200 ′ (e.g., a “rib-monopole”). In this embodiment, the antenna  200 ′ includes one pole  110  (e.g., “monopole” from a conductive member) and antenna feed  150  electrically coupled to the pole  110 . An electrically conductive component/element  210  is attached/connected to pole  110 . A portion of a contoured surface/wall  211  of the electrically conductive component/element  210  is attached to pole  110  and also extends from (e.g., laterally extends from the sides, like a “rib”) the pole  110 . While antenna  200 ′ includes an electrically conductive component/element  210 , it is contemplated that an antenna could include any number of electrically conductive component/elements. Antenna  200 ′ can be “conformal” and conform to a body (e.g., aircraft wing, vehicle body, etc.). 
         [0089]    In this embodiment, the electrically conductive component/element  210  is a curvilinear electrically conductive component/element (e.g., a closed “ring” or cylinder). As described above, the electrically conductive component/element  210  is capable of conducting a current (e.g., generated by the current in pole  110 ) that generates a magnetic field that lowers an overall reactance of the antenna  200 ′, thereby providing enhanced performance (e.g., wide bandwidth) in a more compact volume. In this embodiment, the pole  110  can include a longitudinal axis  213 ′ and the antenna (e.g., the pole  110 , electrically conductive component/element  210 ) occupies a volume (e.g., a cylindrical volume) that has a longitudinal axis  214 ′ that is substantially parallel to longitudinal axis  213 ′. 
         [0090]      FIG. 3  is a schematic of electric currents and magnetic fields in antenna  200  of  FIG. 2A , according to an illustrative embodiment of the invention. In this embodiment, the first current flow  115  and second current flow  125  generates a current flow  215  in first curvilinear electrically conductive component/element  210  and a current flow  225  in the second curvilinear electrically conductive component/element  220 . Associated with the first current flow  215  is a first magnetic field  217  and associated with current flow  225  is a magnetic field  227 . The antenna  200  occupies a volume (e.g., cylindrical volume) having a longitudinal axis  214 . The magnetic field  217  and  227  can be substantially parallel to the longitudinal axis  214 . 
         [0091]    A power source  228  can supply power to generate a current  115  and  125  in the poles  110  and  120 , which subsequently generates a current  215  and  225  in the electrically conductive component/elements  210  and  220 . A method for transmitting or receiving electromagnetic energy can include the step of providing/conducting at least a first current flow  115  in a first pole  110  (e.g., from the power source  228 ) of an antenna and generating a second current flow  215  in at least one electrically conductive element  210  from the first current flow  115  in the first pole  110 . As noted above in  FIG. 2A , electrically conductive element  210  can include a surface having a portion electrically connected to, and extending from, the first pole  110 . The method can also include the step of generating a magnetic field  217  from the second current flow  215  in the electrically conductive element  210 , where the magnetic field  217  lowers a total/intrinsic reactance of the antenna  200 . In some embodiments, the method can also include providing/conducting a third current flow  125  (e.g., from the power source  228 ) in the second pole  120  and generating a fourth current flow  225  in the electrically conductive component  220  from the third current flow  125 . The method can also include generating a magnetic field  227  from the fourth current flow  225  in the electrically conductive component  220 , where the magnetic field  227  lowers a total/intrinsic reactance of the antenna  200 . 
         [0092]    An inductive reactance is generated by the magnetic fields  217  and  227 . The antenna  200  has an additional larger inductive reactance and, therefore, a smaller total reactance than a traditional dipole antenna (e.g., dipole antenna  100  of  FIG. 1A ). A reduction of the total reactance of the antenna  200  produces desirable performance enhancements, such as an increased bandwidth with respect to an equivalent traditional dipole configuration (e.g., a dipole antenna of  FIG. 1A  that does not have additional electrically conductive component/elements besides the poles  110  and  120 ), 
         [0093]    The power gain of a matching circuit is proportional to the fourth degree of an antenna&#39;s reactance: 
         [0000]    
       
         
           
             
               
                 
                   Gain 
                   ≈ 
                   
                     const 
                     
                       B 
                       · 
                       
                         
                            
                           
                             Im 
                              
                             
                               ( 
                               
                                 
                                   Z 
                                   A 
                                 
                                  
                                 
                                   ( 
                                   
                                     f 
                                     C 
                                   
                                   ) 
                                 
                               
                               ) 
                             
                           
                            
                         
                         4 
                       
                     
                   
                 
               
               
                 
                   EQN 
                   . 
                   
                       
                   
                    
                   5 
                 
               
             
           
         
       
     
         [0000]    where B is the bandwidth and f C  is the band center frequency. Considering the dipole antenna  100  of  FIG. 1A  and the antenna  200  of  FIG. 2A , and assuming the antennas  100  and  200  are equal in length, antenna  200  gives a power gain that exceeds the dipole antenna  100  power gain by 625-4096 times (28-36 dB). Equivalently, antenna  200  exhibits a matching bandwidth that is 625-4096 times higher compared to the dipole antenna  100  bandwidth at the equal power gain. The reason for the superior performance is the built-in inductive reactance (X L ) of antenna  200  caused by current flows  215  and  225  in the electrically conductive component/elements  210  and  220  and associated magnetic fields  217  and  227 . 
         [0094]      FIG. 4  shows a high performance compact volumetric antenna  300  (e.g., a “rib-dipole” antenna), according to an illustrative embodiment of the invention. The antenna  300  is a cylindrical volumetric antenna. The antenna  300  includes a first pole  110 , second pole  120  and antenna feed  150 . The antenna also includes sets of electrically conductive component/elements  310  and  320  (e.g., closed rings). In this embodiment, electrically conductive component/elements  310  and  320  are closed and curvilinear. Although not shown, there is a current flow in the closed set  310  of curvilinear electrically conductive component/elements and a current flow in the closed set  320  of curvilinear electrically conductive component/elements  310  and  320  and associated magnetic fields therefrom. Consequently, similar to the antenna  200  of  FIGS. 2A-2B  and  3 , the antenna  300  has desirable additional inductive reactance due to the closed curvilinear electrically conductive component/elements. The antenna  300  can be “conformal” and conform to a body (e.g., aircraft wing, vehicle body, etc.) 
         [0095]    A portion of the electrically conductive component/elements  310  and  320  are connected/attached (e.g., electrically connected) to the first pole  110  and second pole  120 . Each of the respective electrically conductive component/elements  310  and  320  has a wall/surface. In some embodiments, the electrically conductive component/elements  310  and  320  do not encompass/surround the poles  110  and  120 . Rather, a portion of the wall/surface is connected to poles  110  and  120 , such that the electrically conductive component/elements  310  and  320  extend from poles  110  and  120 . The electrically conductive component/elements  310  and  320  can extend laterally/outwardly from the sides of the poles  110  and  120  (e.g., like “ribs” along the poles  110  and  120 ). Electrically conductive component/elements  310  and  320  define a volume having a longitudinal axis  314 , which can be substantially parallel to the longitudinal axis  313  shared by poles  110  and  120 . 
         [0096]      FIG. 5A  shows a high performance compact volumetric antenna (e.g., a “rib-dipole”), according to another illustrative embodiment of the invention. The antenna  400  in  FIG. 5  occupies a half-cylinder volume. The half-cylinder volumetric antenna  400  includes a radiator comprising of one radiating element including a first pole  110 , a second pole  120  and an antenna feed  150 . The first pole  110  and second pole  120  can be coaxial. The half cylinder volumetric antenna  400  includes sets  410  and  420  of electrically conductive components/elements. In this embodiment, the curvilinear electrically conductive components/elements  410  and  420  are contoured and open (e.g., in contrast with curvilinear electrically conductive components/elements shown in  FIGS. 2A-2B  and  3 ) and in part, form the half-cylinder volume formed by antenna  400 . The antenna  400  can be “conformal” and conform to a body (e.g., aircraft wing, vehicle body, etc.) 
         [0097]    The electrically conductive component/elements  410  and  420  are connected to, and extend from, first pole  110  and second pole  120  (e.g., do not surround/encompass the dipole  110  and  120 ). In some embodiments, the electrically conductive component/elements  410  and  420  extend laterally from (e.g., extend outwards) from the poles  110  and  120  (e.g., like “ribs” attached to the poles  110  and  120 ). The electrically conductive component/elements  410  and  420  can be disposed along the first pole  110  and second pole  120 . In this embodiment, the electrically conductive component/elements  410  and  420  are curved/curvilinear. The electrically conductive component/elements  410  and  420  include a contoured surface/wall  411  and  412 . A portion of the contoured surface/wall  411  and  412  of each electrically conductive component/elements  410  and  420  is connected/attached (e.g., electrically connected) to the first pole  110  and the second pole  120 . The half-cylindrical volume formed by the electrically conductive component/elements  410  and  420  can have a longitudinal axis  414  substantially parallel to the shared longitudinal axis  413  of the dipole  110  and  120 . 
         [0098]    Although not shown in  FIG. 5A , there is a current flow in the first half-cylinder set  410  of curvilinear electrically conductive components/elements and a current flow in the second half-cylinder set  420  of electrically conductive components/elements and associated magnetic fields therefrom (e.g., as discussed in  FIG. 3 ). The magnetic field associated with the electric current flow in curvilinear electrically conductive components/elements  410  and  420  electrically connected to a dipole (e.g., poles  110  or  120 ) or a monopole (e.g., as shown in  FIG. 2B ) occurs in both the case of open or closed ribs. Consequently, the half-cylinder volumetric antenna  400  with open electrically conductive components/elements also produces the increased inductive reactance (e.g., as described above and as in cylindrical volumetric antennas  300  and  200  of  FIGS. 2A-2B  and  3 ) even though the curvilinear electrically conductive components/elements from  FIGS. 2A-2B  and  3  were closed, not open. 
         [0099]      FIG. 5B  shows an antenna having electrically conductive component/elements  410  and  420  spaced at varying distances  421 A-E relative to one another. The electrically conductive component/elements  410  and  420  can be each spaced at a distance  421 A-E relative to another electrically conductive component/element. In this embodiment, the distance is increasing from a first end of the antenna to the second end. However, the distance between the electrically conductive component/elements  310  and  320  can be, for example, constant (e.g., as shown in  FIG. 5A ), linear (e.g., linearly increasing/decreasing), logarithmic, randomly distributed, or any combination/variation thereof. 
         [0100]      FIG. 6A  is a schematic of a volumetric antenna that includes shortened and open curvilinear electrically conductive components/elements  510  and  520 . The antenna  500  in  FIG. 6A  shows a first pole  110 , second pole  120  and antenna feed  150 . The radiating element  500  also includes sets  510  or  520  of curvilinear electrically conductive components/elements that are shortened. The curvilinear electrically conductive components/elements  510  or  520  are “shortened” in that the curvilinear electrically conductive components/elements have a countered surface that has a length that is a fraction (e.g., 1/10) a closed cylinder perimeter. When the length of the electrically conductive components/elements is too short, then the antenna will have a performance similar to a traditional dipole antenna (e.g., antenna  100  in  FIG. 1A ), due to the absence of the additional magnetic field. By way of example, when the ribs (e.g., electrically conductive component/elements) are less than 20-30% of the cylinder circumference the rib-dipole performs similar to the traditional dipole. When the ribs (e.g., electrically conductive component/elements) are 50% or longer, the performance is enhanced (e.g., as rib-dipole), due to the magnetic fields generated from the current conducted in the electrically conductive component/elements. 
         [0101]      FIG. 6B  shows an antenna  600  with curvilinear electrically conductive components/elements  610  and  620  that vary in size. The variable length antenna  600  includes a first pole  110 , a second pole  120 , and antenna feed  150 . The antenna  600  can include electrically conductive component/elements  610  and  620 . A portion of a surface/wall  611  and  612  of each of the electrically conductive component/elements  610  and  620  are attached/electrically connected to poles  110  and  120 . The electrically conductive component/elements  610  and  620  are connected to, and extend from, poles  110  and  120 , The curvilinear electrically conductive components/elements in sets  610  and  620  have a contour length (e.g., at least 50% the length of a closed cylinder circumference) so that the currents in the ribs produce the desired additional magnetic field, thereby providing enhanced performance of the antenna  600 . 
         [0102]    In this embodiment, the electrically conductive component/elements  610  and  620  are curvilinear, but they do not necessarily have to be (e.g., as shown in  FIGS. 7 and 13 ). The curvilinear electrically conductive components/elements  610  and  620  are “shortened” (e.g., a contour length that is a fraction of a closed cylindrical perimeter), however, the contour lengths of the curvilinear electrically conductive components/elements  610  and  620  can vary. For example, the electrically conductive component/elements  610  and  620  can have different lengths, widths or thicknesses. The antenna  600  can include, for example, a variable length set of curvilinear electrically conductive components/elements  610  and  620 . 
         [0103]      FIG. 7  shows a non-curvilinear high performance compact volumetric antenna  700  (“rib-dipole antenna”) according to an illustrative embodiment of the invention. The antenna  700  includes a radiator and a feed, with the radiator comprising one single radiating element in the shape of a “blade” dipole parallel to a ground plane. The blade dipole has a first blade  710  (e.g., a first pole made of a conductive plate such as a flat metal plate or sheet) and a second blade  720  (e.g., a second pole made of a conductive plate such as a flat metal plate or sheet), and a feed  750  between poles  710  and  720 . The radiating element  700  also can include planar electrically conductive sheets  715 ,  717 ,  725  and  727 . The electrically conductive sheets  715 ,  717 ,  725  and  727  are capable of conducting a current that generates a magnetic field that lowers a total reactance of the antenna  700 . In this embodiment, the antenna  700  is substantially parallel relative to a ground plane  730 . 
         [0104]    In this embodiment, the antenna  700  includes a first planar electrically conductive sheet  715  (e.g., a metal sheet or flat metal strip) and a second planar electrically conductive sheets  717  (e.g., a metal sheet or a flat metal strip) attached/connected (e.g., electrically connected) to the pole  710  and disposed at an angle (e.g., substantially perpendicular) relative to the metal ground plane  730  and pole  710 . The electrically conductive sheets  715  and  717  extend from the pole  710 . 
         [0105]    The antenna  700  also includes a third planar electrically conductive sheet  725  (e.g., a metal sheet or flat metal strip) and a fourth planar electrically conductive sheet  727  attached to the pole  720  (e.g., a metal sheet or flat metal strip) and disposed at an angle (e.g., substantially perpendicular) relative to the metal ground plane  730  and pole  720 . The electrically conductive sheets  725  and  727  can be attached to, and extend from, the pole  720 . 
         [0106]    This antenna  700  configuration is very desirable for the low profile and wide bandwidth. It can be used as single element for planar antenna arrays (e.g., as shown in  FIG. 13 ) having a performance equivalent to a parabolic dish antenna (e.g., of  FIG. 1D ) but occupying a smaller volume. By way of example, a 2m by 2m antenna array can be constructed using multiple radiators, for example 64 volumetric antenna elements (composed of single or multiple radiating elements) which can have a similar performance as that of a 3m parabolic dish antenna (e.g., as shown in  FIG. 1D ). 
         [0107]    The electrically conductive component/elements  715 ,  717 ,  725  and  727  extend from blades/poles  710  and  720 . A portion of a surface of electrically conductive component/elements  715 ,  717 ,  725  and  727  are attached/connected (e.g., electrically connected) to poles  710  and  720 . The electrically conductive component/elements  715 ,  717 ,  725  and  727 , poles  710  and  720  and ground plane  730  can occupy a volume (e.g., a rectangular/square or parallelepiped). A longitudinal axis of the volume  713  can be substantially parallel to the longitudinal axis  714  shared by the poles  710  and  720  (e.g., along the y-axis). 
         [0108]      FIG. 8  shows an antenna  800  that includes one radiator comprising two half cylinder volumetric radiating elements  400  that occupy a cylindrical space, according to an illustrative embodiment of the invention. A half-cylinder volumetric radiating element  400  can be disposed to face another half-cylinder multi-rib volumetric radiating element  400 . The antenna  800  can include a first, second, third and fourth pole. For example, each half-cylinder volumetric radiating element  400  includes a first pole  110 , a second pole  120  and a feeding unit  150 . Each radiating element  400  also includes several electrically conductive components/elements  410  and  420  that are attached/connected (e.g., electrically connected to) and extend from poles  110  and  120 . The cylindrical volume can include a longitudinal axis  814  (e.g., the y-axis) substantially parallel to the longitudinal axis  813  shared by poles  110  and  120 . 
         [0109]    The antenna  800  (e.g., first, second, third, and fourth poles and the electrically conductive component/elements) occupies a volume. In this embodiment, the volume is a cylindrical volume (e.g., also shown in  FIGS. 10A-C ) and the length of the antenna (e.g., along the z-axis) is greater than a width, thickness or radial width (e.g., along the x-axis). However, in some embodiments, the antenna (e.g., poles, feed and electrically conductive component/elements) occupies a conical volume (e.g., such as the bottom or top half of the volume occupied by the antenna shown in  FIGS. 11A-11C ), bi-conical volume (e.g., as shown in  FIGS. 11A-11C ), a spherical volume (e.g., as shown in  FIGS. 12A-12C ), a pyramid, or parallelepiped (e.g., as shown in  FIG. 7 ). 
         [0110]    The radiating element  400  can be about 5 times shorter than a conventional HF whip antenna and can feature higher gain and pattern control due to, at least in part, the magnetic fields generated by the curvilinear electrically conductive components/elements  410  and  420 . The radiating element  400  can also be used for directed energy applications (e.g., 10 kW) while reducing overall antenna size as compared to, for example, parabolic antenna designs (e.g., as shown in  FIG. 1D ). In some embodiments, the half-cylinder volumetric radiating elements  400  are facing one another and are fed about or exactly 180 degrees out of phase. In some embodiments, the half-cylinder volumetric radiating elements  400  are fed out of phase by a different phase angle, e.g. about 45 degrees, 90 degrees, 135 degrees, 233 degrees, or any other angle. The radiating element  400  can be used for HF (e.g., 2 MHz to about 30 MHz). The radiating element  400  can also have a height of about 65 cm and a diameter of about 10 cm. In some embodiments, each of the electrically conductive components/elements  410  and  420  have a length of about 17.5 cm, a width of about 1.2 cm and are spaced 4.5 cm relative to one another. The gain at 2 MHz can be about 4 dB and the gain at 16 MHz can be about 7 dB. In contrast, a conventional dipole (e.g., “whip”) antenna has a height of about 3-5 in and has a gain at 2 MHz of about −10 dB and a gain at 16 MHz of about 3 dB. At 8 MHz, the antenna  800  can have an operational wavelength (λ) of about 30 meters. The half-cylinder volumetric radiating elements  400  can be spaced about 6.0 centimeters from each other, e.g. at a distance of about λ/500. The distance between the volumetric radiating elements  400  can be less (e.g. much less) than half of the operational wavelength (e.g. the condition d&lt;&lt;λ/2 can be satisfied). 
         [0111]      FIG. 9A  shows the antenna pattern for a half-cylinder volumetric antenna  400  including one radiator comprising one radiating element (e.g., as shown in  FIG. 5 ) and  FIG. 9B  shows an antenna pattern for a volumetric antenna  800  having one radiator comprising two closely spaced radiating elements  400  (e.g., as shown in  FIG. 8 ). The volumetric antenna  800  has advantages compared to the volumetric antenna  400  in terms of pattern control and higher gain. The antenna pattern of the antenna  400  has the shape of a toroid with axis of rotation along the z-axis and is shown in  FIG. 9A . The antenna pattern of the antenna  800  is also a toroid, but with axis of rotation along the x-axis, as shown in  FIG. 9B . This rotation of the antenna pattern (e.g., having an axis of rotation along the x-axis as shown in the Figure) can have advantageous applications, for instance in communications, for stealth and optimal placement on vehicles. The antenna  800  can have better stealth, aerodynamic shape in land vehicles or safer cell operation for cell phone users. 
         [0112]      FIGS. 10A-C  show different embodiments of cylindrical volumetric antennas, according to illustrative embodiments of the invention. A cylindrical volumetric antenna can include a single cylindrical volumetric radiating element (e.g., as shown in  FIG. 2 ) with closed curvilinear electrically conductive components/elements. As noted above in  FIG. 2 , a portion of a contoured surface of each of the electrically conductive component/elements is connected/attached (e.g., electrically connected) to the poles. The electrically conductive component/elements are connected to, and extend from, the poles. In some embodiments, the electrically conductive component/elements extend laterally from (e.g., extend from the sides of the poles). As shown in  FIG. 10A , a cylindrical volumetric antenna  800  can also include two half cylinder volumetric radiating elements  400 A and  400 B disposed to face each other to occupy a cylindrical volume/space. Each half cylinder volumetric radiating element  400  includes two poles and several curvilinear electrically conductive elements/components  410  and  420 . A first half-cylinder volumetric radiating element  400 A can be fed out of phase relative to a second half cylinder volumetric radiating element  400 B, for example by about or exactly 180°, or any other phase angle. 
         [0113]    Alternatively, as shown in  FIGS. 10B and 10C , a cylindrical volumetric antenna  803  can include a radiator comprising three or more volumetric radiating elements, each having shortened curvilinear electrically conductive components/elements. The electrically conductive component/elements are connected to, and extend from (e.g., laterally extend from), the poles. A portion of a contoured surface of each of the electrically conductive component/elements is connected to the poles.  FIG. 10B  shows a cylindrical volumetric antenna  803  that includes three “third-cylinder volumetric radiating elements”  400 ′A-C where each third-cylinder volumetric radiating element  400 ′A,  400 ′B or  400 ′C includes two poles (e.g., poles  110  and  120  as shown in  FIGS. 2A-2B ,  3 - 5 , and  6 A- 6 B) and shortened curvilinear electrically conductive components/elements  410 ′ and  420 ′ (e.g., each having a contour length about ⅓ that of a closed cylindrical perimeter). The three third-cylinder volumetric radiating elements  400 ′A-C can be fed about or exactly 120° out of phase with respect to one another. 
         [0114]      FIG. 10C  shows cylindrical volumetric antenna  804  that includes a radiator comprising four “fourth cylinder volumetric radiating elements”  400 ″A-D where each fourth cylinder volumetric radiating element has two poles and shortened curvilinear electrically conductive components/elements  410 ″ and  420 ″ (e.g., each having a contour length of about ¼ that of a closed cylindrical perimeter). The four volumetric radiating elements  400 ″A-D can be disposed to face one another so that the antenna  804  occupies a cylindrical volume. The fourth cylinder volumetric radiating elements  400 ″A-D can be fed about or exactly 90° out of phase with respect to one another. 
         [0115]      FIGS. 11A-11C  show bi-conical volumetric antennas, according to illustrative embodiments of the invention. The bi-conical volumetric antennas in  FIGS. 11A-11C  include a radiator comprising two or more fractional bi-cone volumetric radiating elements that are oriented to occupy a bi-conical volume. For example, in  FIG. 11A  the antenna  900  includes two half-bi-cone volumetric radiating elements  901 A and  901 B, each including two poles  110  and  120 , a feed  150  and sets of curvilinear electrically conductive components/elements  902  and  903  disposed along the poles. The electrically conductive component/elements  902  and  903  are connected to/attached to (e.g., electrically connected), and extend from, the poles  110  and  120 . The electrically conductive component/elements  902  and  903  can extend laterally from the poles  110  and  120 . In this embodiment, the two half bi-cone volumetric radiating elements  901 A and  901 B are faced towards each other, so that the antenna  900  occupies a bi-conical volume. Each half-bi-conical volumetric radiating element  901 A and  901 B can be fed about or exactly 180° out of phase to one another. 
         [0116]      FIG. 11B  shows a volumetric antenna  904  having a radiator comprising three third-bi-cone volumetric radiating elements  905 A-C, each including two poles  110  and  120 , a feed  150  and curvilinear electrically conductive components/elements  906  and  907  disposed along each pole. As  FIG. 11B  shows third-bi-cones, the electrically conductive components/elements  906  and  907  are shorter than those in  FIG. 11A . The three third-bi-cone volumetric radiating elements  905 A-C can be faced towards one another, so that the antenna  904  occupies a bi-conical volume. Each third-bi-cone volumetric radiating element  905 A-C can be fed about or exactly 120° out of phase to one another. 
         [0117]      FIG. 11C  shows a volumetric antenna  908  having a radiator comprising four fourth-bi-cone volumetric radiating elements  908 A-D, each including two poles  110  and  120  and curvilinear electrically conductive components/elements  909  and  910  disposed along each pole  110  and  120 . The four volumetric radiating elements  908 A-D are faced/disposed towards each other such that the antenna  908  occupies a bi-conical volume. Each fourth-bi-cone volumetric radiating element  908 A-D can be fed about or exactly 90° out of phase to one another. 
         [0118]      FIGS. 12A and 12B  show spherical volumetric antennas, according to different illustrative embodiments of the invention. The spherical volumetric antennas can include two or more fractional spherical volumetric radiating elements disposed to face one another so that the antenna occupies a spherical volume. For example,  FIG. 12A  shows an antenna  1000  having the radiator comprising two half-sphere volumetric radiating elements  1001 A-B that are being one another to occupy a spherical volume  1000 . Each half-sphere volumetric radiating element  1001 A-B includes two curvilinear poles  110 ′ and  120 ′, a radiating element feed (not shown for purposes of clarity) and curvilinear electrically conductive components/elements  1002  and  1003  disposed along the poles  110 ′ and  120 ′. A portion of a surface/wall of each electrically conductive component/element  1002  and  1003  is connected to and extends from the poles  110 ′ and  120 ′. In some embodiments, a portion of the electrically conductive component/elements  1002  and  1003  is attached/connected to (e.g., electrically connected to) the poles, but also laterally extend from the poles  110 ′ and  120 ′. The curvilinear electrically conductive components/elements  1002  and  1003  of  FIG. 12A  have a contour length that is less than or equal to half of a perimeter for a closed cylinder and are of varying lengths so as to form the spherical volume. The half-sphere volumetric radiating elements  1001 A-B can be fed about or exactly 180° out of phase relative to one another. 
         [0119]      FIG. 12B  shows a volumetric antenna  1004  having a radiator comprising three third-sphere volumetric radiating elements  1005 A-C that face one another to occupy a spherical volume  1004 . Each third-sphere volumetric radiating elements  1005 A-C includes two curvilinear poles  110 ′ and 120′ and curvilinear electrically conductive components/elements  1006  and  1007  disposed along the poles  110 ′ and 120′. In this embodiment, the curvilinear electrically conductive components/elements  1006  and  1007  of  FIG. 12B  have a contour length that is less than or equal to a third of a perimeter for a closed cylinder and are of varying lengths so as to form the spherical volume. The third-sphere volumetric radiating elements  1005 A-C can be fed about or exactly 120° out of phase relative to one another. 
         [0120]      FIG. 12C  shows a volumetric antenna  1008  having a radiator comprising four fourth-sphere volumetric radiating elements  1009 A-D that face one another to form an antenna  1008  that occupies a spherical volume. Each fourth sphere volumetric radiating element  1009 A-D includes two curvilinear poles  110 ′ and  120 ′ and curvilinear electrically conductive components/elements  1010  and  1011  disposed along each pole  110 ′ and  120 ′. In this embodiment, the curvilinear electrically conductive components/elements  1010  and  1011  of  FIG. 12C  have a contour length that is less than or equal to a fourth of a perimeter for a closed cylinder and are of varying lengths so as to form the spherical volume. The fourth-sphere volumetric radiating elements  1009 A-D can be fed about or exactly 90° out of phase relative to one another. 
         [0121]      FIG. 13  shows a further embodiment of an array of volumetric antennas  1100  composed of non-curvilinear high performance compact volumetric radiators  700 , according to an illustrative embodiment of the invention. The antenna array  1100  includes a plurality (e.g., two or more) of radiators  700  placed at a distance approximately half a wavelength from each other. Each radiator has poles (e.g., poles  710  and  720  as in  FIG. 7 ) and planar electrically conductive component/elements (e.g., electrically conductive component/element  715 ,  717 ,  725  and  727  as in  FIG. 7 ) that are connected to, and extend from, the poles. A portion of the electrically conductive component/elements are connected/attached to (e.g., electrically connected to) the poles. The electrically conductive component/elements also extend from the poles (e.g., extend from the sides like “ribs”). In this embodiment, each electrically conductive component/element is substantially perpendicular to each pole and ground plan  730 . This antenna array  1100  has excellent performance for directed energy applications (e.g., focused narrow beam). The antenna array  1100  can have performance equivalent to the parabolic dish antenna  1 D while occupying a smaller volume. By way of example, the antenna array  1100  can be 2m by 2m and have a similar performance as that of a 3m parabolic dish antenna (e.g., as shown in  FIG. 1D ). The array  1100  can be made of radiators  700  each comprising a single radiating element as in  FIG. 13 . Alternatively or in addition, the array  1100  can be an array of volumetric radiators  800  each comprising multiple radiating elements. 
         [0122]      FIG. 14  shows a volumetric dipole antenna  1400  having a radiator  1405  comprising two radiating elements  1410 ,  1415 , according to an illustrative embodiment of the invention. The radiating elements  1410 ,  1415  are spaced from each other at a distance d, e.g. d=0.13λ (measured across the straight, vertical portions of the radiators). The resonant frequency for the antenna  1400  can be about 500 MHz. The radiating elements  1410 ,  1415  can be filled and/or lined with a dielectric material having a dielectric constant ∈. The radiating elements  1410 ,  1415  can be differentially fed (e.g. fed with signals that are out of phase with respect to one another and/or fed having different intensities) via feeding units  1420 ,  1425  respectively. Differential feeding can shape the antenna pattern as desired, e.g. can produce a radiation pattern that varies as a function of the phase shift between signals and/or the dielectric constant r. 
         [0123]      FIGS. 15A-15F  show computer simulations  1500 ,  1510 ,  1520 ,  1530 ,  1540 ,  1550  of radiation patterns in the azimuthal plane for the antenna shown in  FIG. 14 , according to an illustrative embodiment of the invention. Taken together, the computer simulations  1500 ,  1510 ,  1520 ,  1530 ,  1540 ,  1550  show that radiation patterns for the dipole antenna  1400  can be produced and/or controlled by varying the dielectric constant ∈ and/or the phase shift between the signals provided by the differential feeds. 
         [0124]      FIG. 15A  shows a simulation  1500  of radiation patterns  1502 ,  1504 ,  1506  on azimuthal grid  1508  for the antenna  1400  fed with a phase shift of zero degrees. For antenna pattern  1502 , ∈=1. The antenna pattern  1502  is substantially circular in the azimuthal direction. For antenna pattern  1504 , ∈=10. The antenna pattern  1504  is highly directional along the axis from −90 degrees to 90 degrees. For antenna pattern  1506 , ∈=20. The antenna pattern  1506  is substantially circular in the azimuthal direction. Simulation  1500  thus shows that a highly directional field can be achieved by selecting a dielectric constant ∈ of approximately 10 and without feeding the radiating elements  1410 ,  1415  out of phase. 
         [0125]      FIG. 15B  shows a simulation  1510  of radiation patterns  1512 ,  1514 ,  1516  on an azimuthal grid  1518  for the antenna  1400  fed with a phase shift of 45 degrees. For the antenna pattern  1512 , ∈=1. For the antenna pattern  1514 , ∈=10. For the antenna pattern  1516 , ∈=20. The simulation  1510  shows that using differential feeding can create a directional antenna pattern. 
         [0126]      FIG. 15C  shows a simulation  1520  of radiation patterns  1522 ,  1524 ,  1526  on azimuthal grid  1528  for the antenna  1400  fed with a phase shift of 90 degrees. For the antenna pattern  1522 , ∈=1. For the antenna pattern  1524 , ∈=10. For the antenna pattern  1526 , ∈=20. The simulation  1520  shows that using differential feeding can create a directional antenna pattern. The antenna pattern can be made highly directional (e.g. the directionality can be at 90 degrees as shown on the azimuthal grid  1528 ). In these simulations it is evident that for ∈=20 and a phase shift of 90 degrees the antenna pattern  1526  becomes almost hemispherical between 0 degrees and 180 degrees on the azimuthal grid  1528 . 
         [0127]      FIG. 15D  shows a simulation  1530  of radiation patterns  1532 ,  1534 ,  1536  on azimuthal grid  1538  for the antenna  1400  fed with a phase shift of 135 degrees. For the antenna pattern  1532 , ∈=1. For the antenna pattern  1534 , ∈=10. For the antenna pattern  1536 , ∈=20. The simulation  1530  shows that using differential feeding can create a directional antenna pattern. 
         [0128]      FIG. 15E  shows a simulation  1540  of radiation patterns  1542 ,  1544 ,  1546  on azimuthal grid  1548  for the antenna  1400  fed with a phase shift of 180 degrees. For the antenna pattern  1542 , ∈=1. For the antenna pattern  1544 , ∈=10. For the antenna pattern  1546 , ∈=20. The simulation  1540  shows that using differential feeding can create a directional antenna pattern. The gain can be increased by the proper choice of the dielectric filter. This pattern corresponds to the rotated toroidal antenna pattern as shown above in  FIG. 9B . Generally, the antenna pattern can be shaped to become almost hemispherical, in this case between 0 degrees and 180 degrees on the azimuthal grid  1548 . 
         [0129]      FIG. 15F  shows a simulation  1550  of radiation patterns  1552 ,  1554 ,  1556  on azimuthal grid  1558  for the antenna  1400  fed with a phase shift of 233 degrees. For the antenna pattern  1552 , ∈=1. For the antenna pattern  1554 , ∈=10. For the antenna pattern  1556 , ∈=20. The simulation  1550  shows that using differential feeding can create a directional antenna pattern. The gain can be increased by the proper choice of the dielectric filter. It can be seen that  FIG. 15F  shows substantially similar patterns to  FIG. 15D  above, except that the antenna patterns are rotated 180 degrees in the azimuthal plane. Thus, the orientation of the antenna pattern can be controlled by varying the phase shift and dielectric constant. Taken together,  FIGS. 15F and 15D  demonstrate that changing only the signal phase provided by the feed can change the antenna pattern from one hemisphere (0 degrees-180 degrees in the azimuthal plane) to the opposite hemisphere (−180 degrees-0 degrees in the azimuthal plane) in a controlled fashion. 
         [0130]    The invention has been described in terms of particular embodiments. While the invention has been particularly shown and described with reference to specific illustrative embodiments, it should be understood that various changes in form and detail may be made without departing from the spirit and scope of the invention. The alternatives described herein are examples for illustration only and not to limit the alternatives in any way. The steps of the invention can be performed in a different order and still achieve desirable results.