A high-gain, hemi-spherical coverage, multi-sided flattened luneburg lens antenna

Abstract

A multiple flat sided modified Luneburg Lens antenna to provide a broadband and hemi-spherical coverage. The Modified Luneburg Lens antenna has a flat surface at the bottom and quadrilateral / hexagonal / octagonal / decagon / dodecagon flat surfaces at the sides (e.g., "cupcake shaped") to manipulate the signal directivity of a radio frequency transmission or reception of interest in a plurality of octaves of bandwidth. The antenna may be configured with a Planar Ultra-Wideband Modular Array (PUMA) Antenna array structure with a broadband anti-reflective layer added between the two devices. The anti-reflective layer marries the two devices (lens and PUMA) and creates a broadband impedance matching between the new modified Luneburg lens antenna and dipoles of the PUMA array while maintaining the capability of the system to transmit and receive signals in a plurality of octaves of bandwidth.

Description

A HIGH-GAIN, HEMI-SPHERICAL COVERAGE, MULTIE-SIDED FLATTENED LUNEBURG LENS ANTENNA CROSS-REFERENCE TO RELATED APPLICATIONS

[0601] This patent application is an international application which claims priority to U.S. Provisional Patent Application Number 63 / 627,142, filed on May 19, 2020, the disclosure of which is incorporated herein in its entirety. FIELD OF THE INVENTION

[0002] This disclosure relates to communications and radar antenna technology, and more particularly to multiband microwave electronically steered fens anicnms with relatively high gain and wide beamscanning angle. BACKGROUND OF THE INVENTION

[0003] Satellite communications (SATCOM) and terrestria microwave communications systems such as microwave line-of-sight, cellular, and tactical networking typically require the use of transmitter / receivers connected io directional antennas that aim the energy of a signal in cither a general or specific direction towards another directional antenna connected to a transmitter / receiver, The most cotunon {ype of antenna used in both SATCOM and ierresirial communications is a parabolic reflector with a waveguide feed located at the focal point of the parabola. These antennas are highly effective in networks where both the antenna and the distant end antenna are both stationary, such as in the case of a Geosynchronous Earth Orbit (GEO) satellite, or a microwave point-to-point link between two buildings or a building and a tower.

[0004] New satellite consicliations that operate in Non-Geastationary Satellite Orbit (NGSO). specifically in Medium Earth Orbit (MEO) and Low Earth Orbit (LEQ), as well as the increasingly ubiquitous implemeniation of terrestrial communications systems that require line-of-sight and nonline- of-sight beam-steering base stations with multiple beams of energy being radiated simultaneously are challenging the paradigm of single-beam, mechanically articulated parabolic reflector antennas. Several new and innovative solutions involving Electronicaly Steerable Array (ESA) antennas and, more specifically, Active ESA (AESA) amenmas have been developed by companies such as Gilat, Phasor, and Boeing. The value these terminals bring to the marketplace is their inherent ability to direct one or several energy beams in different directions without any moving parts, allowing installers to place an antenna in one position and have it connect to distant end antennas that are in motion, such as NGSQ LEO and MEQ conununication satellites, and antennas attached to moving vehicles such as Unmanned Acriaf Vehicles (UAVs) and manned aircrafi, Furthermore, these antennas can be placed on a moving vehicle such as an airplane, naval vessel, or ground vehicle such as a train, automobile, and drone, and concurrently track a distant end antenna regardless of whether that antenna is also moving or hot.

[6005] AESA antennas are inherently expensive due to the complexity of the circuitry being used and the vast volume of clements that must be employed to replicate the gain and directivity of a parabolic reflector. Furthermore, most implementations of AESA technology are narrow-bandwidth devices and are unable to opevate across multiple frequencies simultaneously. There exists a need in the art for improved antennas for use in SATCOM. SUMMARY OF VARIOUS EMBODIMENTS OF THE INVENTION

[0006] The invention provides a low-cost, hemi-spherical beamscanning coverage, multi-beam, multi- band beamforming electronically steerable fens antenna for terrestrial wireless, satelite, and radar applications.

[0007] The present invention achieves technical advantages by using a multi-sided fattened Lunchurg (Luneburg) Lens that allows a direct connection to a {lat radiating antenna device as opposed to a curved radiating antenna device. By connecting the Planar Ultra-wideband Multiband Array (PUMA) antenna to the geomeiric (e.¢., octagonal or decagonal shaped) flattened Luncburg Lens with a broadband anti- reflective luver, a new class of ultra-wideband Jens antennas is created that allows for near hemispherical coverage pattems across multiple frequency ranges, ideal for terrestrial wireless, satellite, and radar applications.

[0008] The methods described herein comprise connecting the two elements by removing the top dielectric fayer of the PUMA antenna and using the mualti-sided flattened Lunebarg Lens to match the impedance of the dipole elements of the PUMA to the Luneburg lens instead of matching the impedance to free space. By connecting the PUMA antenna to the Modified Lancburg Lens with the removal of the top dielectric Jayer of the PUMA, an easily manufacturable lens antenna that provides multiple simultaneous beams with high directivity and Iow side-lobes is created. Yostead of using the PUMA as an array of feeds that create gain through phasing, one clement of the PUMA is ithuninated ata time in order to develop transmit and receive beam in the desired direction based on where the beam illuminates the lens. The spacing between the PUMA antenna and Modified Luncburg Lens is designed carefully to minimize sidelobes.

[0009] A phased array antenna, such as a patch array or slot array, requires multiple independent feed networks, each possessing their own phase shifters and other key elements, increasing the cost and complexity of the apparatus. By implementing PUMA Antenna clements feeding a multi-sided flattened Luncburg lens instead of a phased array antenna, no phase shifters are necessary, as well as no dielectric layer for the PUMA antenna. The inventors discovered that the approaches described herein simplify the antenna architecture and reduce cost substantially.

[0010] In an embodiment, a modified Luncbury lens antenna may comprise fattened side surfaces and a flat bottom. The modified Luncberg lens antenna may have 4, 6, 8, 10, or 12 flattened side surfaces. The flattened side surfaces may be in the lower hemisphere of the fens. The flattened side surfaces may be arraigned around the circamfcrence of the modified Luncburg lens.

[0011] In an embodiment, the fattened side surfaces may be configured with a broadband anti-reflective {AR} layer. The anti-reflective layer may bave an inhomogeneous graded dielectric permittivity profile. The inhomogeneous graded dielectric permitiivity profile may be Klopfenstein, Exponential, Gaussian, or Triangular.

[0012] In an embodiment, the flattened side surfaces may be configured with Planar Ulrawideband Modular Arrays (PUMA).

[0013] In an embodiment, the Luneberg lens may achieve nultipte simultaneous beams on a 180° clevation plane and 360° azimuthal plane, optionally with high gain and low side-lobes.

[0014] In an embodiment, the Luneberg lens may have an increased aperture efficiency of more than about 80%.

[0015] In an embodiment, the intersection of the adjacent scanned beams pray be be designed to be about {dB-3dB below to peak gain value.

[0016] In an embodiment, the Luncberg lens may have a wideband frequency coverage, optionally 6:1 bandwidth ratio, allowing for operation in multiple frequency bands simultaneously.

[0017] In an embodiment, the Luncberg lens may be configured for multiple simuliancous beams.

[0018] In an embodiment, the Luneberg lens may be configured to provide up to +7 90 degrees of sky coverage In a semi-hemispherical pattern.

[0019] In an embodiment, the flattened side surfaces may be configured with ultra-wideband (UWB) antenna structure, The UWB antenna structure may be matched to the lens via an anti-reflective layer. The anti-reflective layer may have an inhomogencous graded dielectric permittivity profile. The inhomogeneous graded dielectric permittivity profile may be Klopfenstein, Exponential, Gaussian, or Triangular.

[0020] In an embodiment, the individual elements of the UWB antenna may function as individual feeds for individual beams aimed in separate directions through the lens.

[0021] In an embodiment, a method for manufacturing a modified Luncburg lens may comprise connecting the modified Luneburg Jens to a PUMA antenna comprising removing the top dielectric layer of the PUMA antenna and using the multi-sided flattened Luneburg Lens to match the impedance of the dipole elements of the PUMA to the Lunebwrg lens. The method may not comprise matching the impedance to free space. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The advamages and features of the present invention will become better understood with reference to the following more detaifed description taken in conjunction with the accompanying drawings.

[0023] FIG. 1 ilfustrates a particular implementation of a Luncburg Lens, showing two different points of excitation and two beams being formed through the fens.

[0024] FIG. 2 depicts a generalized Luncberg fens’ beamforming image.

[0025] FIG. 3 depicts Luneburg Lens configured with a waveguide array, illustrating potential problems with standard waveguide feed integration with spherical Luneberg fens.

[0026] FIG. 4 depicts a flat sided Luncburg lens design, showing spherical Luneberg lens modified into multiple flat-surfaced lenses. The Luncburg lens may have 4, 6, &, 10, or 12 flattened sides. The modified Tauneberg lens has a {lattened feed surface at the bottom and nwiltiple flattened surfaces at the sides surrounding the lens. This allows for the housing of a maximum number of feed elements along the fens’s surfaces using multiple flattened sides instead of one single fattened bottom surface.

[0027] FIG. 5 depicts multiple flattened sided Luncburg lens with PUMA array. The Lunchurg lens may have 4, 6, 8, 10, or 12 flattened sides. The surfaces may be configured with a broadband anti-reflective (AR) layer can be included with cach flattened surface to minimize any possible impedance mismaiches resuiting from the permittivity mismatches between the fens and free space. The anti-refective layer may have an inhomogeneous graded dielectric permittivity profile, e.g. Klopfensicin, Exponential, Gaussian, Triangular, to minimize the impedance mismatches between the flattened surface and feed sources.

[0028] FIG. 6 depicts a multiple flattened sided Luncbury lens with anti-reflective layer incorporated around the flattened surface. The Luncburg lens may have 4, 6, 8, 10, or 12 flaticned sides.

[0029] FIG. 7 depicts a PUMA array. In an embodiment, the modified Laneburg lens may comprise flatiened sides configured with Planar Ultrawideband Modular Arrays (PUMA) configured as feed

[0030] FIG. 8 is PUMA single efement topology. In an embodiment, the modified Luncburg lens may comprise {fattened sides configured with Planar Ultrawideband Modular Arrays (PUMA) configured as feed sources.

[0031] FIG. 9 depicts an octagonal shaped Luncburg Tens (8 fattened sides) with a flat bottom.

[0032] FIG. 10 depicts a hexagonal shaped Luncbarg lens (6 flatiened sides) with a flat bottom {top] and an octagonal shaped Luncburg lens (R flattened sides) with a flat bottom [bottom].

[0033] FIG. 11 depicts an octagonal shaped Lunebury lens (8 fattened sides) with a fat bottom configured with an anti-reflective layer and a PUMA feed network. The surfaces may be configured with a broadband anti-reflective (AR) layer can be included with cach flattened surface to minimize any possible impedance mismatches resulting from the permittivity mismatches between the lens and free space. The anti-reflective layer may have an inhomogencous graded dielectric perntittivity profile, e.g. Kloplensiein, Exponential, Gaussian, Triangular, to minimize the impedance mismatches between the flattened surface and feed sources.

[0034] FIG. 12 depicts a PUMA architecture accordingly to an embodiment. Tn an embodiment, the modified Lancburg lens may comprise flattened sides configured with Planar Ulrawideband Modular Arrays (PUMA) configured as [eed sources.

[0035] FIG. 13 depicts a hexagonal shaped Luncburg lens (6 flatiened sides) with a flat bottom itfustrating multiple simultaneous beamforming using lens antenna configured with a PUMA feed network,

[0036] FIG. 14 depicts a decagonal shaped Luneburg Tens (10 (fattened sides) with a flat bottom {bottom] and a depicts a dodecagonal shaped Luncburg lens (12 flattened sides) with a flat bottom [top]. The scale bars are for illustrative purposes only and are not intended to be limiting, DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Beam Forming Lens

[0037] An alternative class of antennas, specifically lens-based antennas, have existed in theory since 1854 when J.C. Maxwell proposed the fish-eye lens, Radolf Luncburg proposed another lens solution which bears his name in 1944. R. K. Luncburg, Mathematical Theory of Optics. Providence, RI: Brown Univ. Press, 1944.

[0038] Conventional spherical lens antennas are ideafly suited for mmulti-beam applications as they allow signals to travel through them at many various angles without interfering with one another, However, they are difficult and expensive 10 manufacture as the radio energy feed assemblages must be connceted to the lens around the lower hemisphere, requiring a physical connection to various points along a curved surface. This makes it difficult to move a signal from onc portion of the lens to another, usually requiring a complex mechanically driven moving feed assemblage. Multiple beans ave even more difficult as the various moving mechanical assemblages must not interfere with one another.

[0039] A new type of radio frequency optical lens, called a Modified Luncburg Lens, uses rransformational optic (TO) mathematics to flatten the portion of the fower hemisphere of the spherical fens, allowing for a flat printed circuit board antenna feed to be connected to the lower hemisphere of the lens. The Modified Luncburg Lens has an inherently broadband nature to the device, allowing for signals in a plurality of octaves to transit the fens in the desired directions,

[0040] To date there has been no mechanism for connecting this lens to an ultra-wideband (UWB) antenna that can also transmit and receive signals in a plurality of octaves in frequency through many or all of the antcana ports of the Modified Luneburg Lens.

[0041] A new class of ultra-wideband antennas. one of which is called a Planar Ultrawideband Multiband Antenna (PUMA), use a unique configuration of dipoles in order to create a broadband antenna that can transmit and receive radio signals in a plurality of octaves of frequency. U.S. Patent Pablication No. 2012 / 0146869.

[0042] While UWB aniennas such as the PUMA are able to transmit multiple beams sinmliancousty, the scan angle of the PUMA is only + 35 degrees from boresite (2enith), below which the radiated signal begins to degrade in both insertion Joss and axial ratio. Furthermore, the PUMA is typically used as an array of antennas and has not been connected to a fens to create a broadband lens antenna system.

[0043] UWB antennas and Luncbarg Lenses have not been successfully connected to one another before. The challenge in doing so resides in connecting a flat array antenna to a spherical object, and matching the impedance of the UWB antenna to the Luncburg Lens, as typically both devices must have their impedance match free space, requiring competing dielectric layers and ercating a complex matching challenge.

[0044] Embodiments of the present disclosure provide systems and methods that enable an ultra- wideband, high-gain, wide-angle, multi-beam antenna / lens system that creates an electronically steered array (ESA) lens antenna. Maudified Luneburg Lens for Beamforming & Beam-steering

[0045] Due to the inherent property of essentially infinite focal points. a Luneburg Lens may be used in an antenna because it can focus on radio wives emanating [rom any direction. From a practical standpoint, there are three characteristics of a real lens that present chalienges.

[0046] (1) Since the fens is spherical, the feeds must be attached to the outside of a round strucure. This requires an claborate three-dimensional structure to be created to support these feed assemblages. This most often involves a manual process or a complex sutomated process to assemble and align the structure. This increases cost.

[0047] (2) For traditional feeds such as horn and patch antennas, the lens structure presents a radio frequency (RF) impedance tw the feed. In order 10 match the feed to the structure, an RF matching network must be designed in order to achieve acceptable performance when the feed is mated to the antenna. Both RF matching networks and tradivonal feeds tend to be limited in bandwidth. If constructed properly, the lens itself is broadband, but the resulting antenna assembly is narrowband due to the limitations of the feed and the match,

[0048] (3) Since the diclectric is non-uniform, manufacuwre the lens is difficult. Approximations of Luncburg lenses are made using layers of dielectric materials with varying dielectric constants, however making a lens with a cominuously varying dicleciric constant has not been described. Modified Luneberg Leas Manufacturing Methods

[0049] Methods for designing and manufacturing a Modified Luneburg lens that has both a non-uniform and non-circular varying diclectric constant are described herein. The problem of having to feed ihe fens with a circular (non-planar) feed arrangement may be solved by using transformational optics (TQ) mathematics to transform the feed surface from one that is round to one that is flat (planar). Manufacturing a flat (planar) feed structure may be done using printed circuit board development techniques known in the art.

[0050] The problem of manufacturing the continuousty-varying dielectric lens may be sotved by using additive manufacturing (also known as three-dimensional (3D) printing) to create a structure with a non- homogenous dicleciric constant. The additive manufacturing process may be used to create a structure that incorporates small air gaps of varying size within the dielectric material. If the air gaps and the dielectric structure are small with respect 10 the wavelength of the desired signal, the structure approximates a diclectric constant of 1.0. If the dielectric constant of the structure material is 3.0, the range of possible diclectric constants in the structare can vary from 3.0 (no air pockets) to close to LO {very small amounts of dicleciric material with mostly air gaps). The printing process builds the structure with small individual blocks called “cells” and allows the dielectric constant to be varied on a ceft-by-cell basis. The cells can be small with respect to the wavelength of the signal, so good granularity in the gradient of the dielectric constant is achievable.

[0051] If the air gaps and the diclectric structure are smail with respect to the wavelength of the desired signal, the structure approximates a dielectric constant of 1.0. If the dielectric constant of the structure material is 3.0, the range of possible dielectric constants in the structure can vary from 3.0 (substantially 10 air pockets in the material) to close to 1.0 (a small amount of dielectric material as compared to large amount air gaps). For example, a structure with a dielectric constant of around 3.0 would be substantially free of sir pockets in the material. In contrast, a swructare with a dielectric constant around 1.0 may comprise a larger amount of air gaps than dielectric material, e.g., the material will be mostly air gaps by vohune.

[0052] A specific problem with Luncburg lenses is the match between the feed and the fens. Instead of attaching the feed directly to the fens. which has a varying match to the feed from center to the edge of the flat part of the structure, an interface layer (referred to as an “anti-reflective layer”) may be insericd between the feed and the modified lens. This layer designed so that a good match between the feed and the lens is obtained across the entire interface surface.

[0053] A nultipie flat sided modified Luncburg Lens antenna can provide a broadband mud hemi- spherical coverage. The Modified Lunebury Lens antenna may have a geometric shape, e.g. a CupCake shape, comprising a flat surface at the bottom and multiple flat surfaces at the sides to manipulate the signal directivity of a radio {requency transmission or reception of interest in a plurality of octaves of bandwidth. The modified Luncburg lens may be quadrilateral (4 flat side surfaces), hexagonal {6 flat side surfaces), octagonal (8 flat side surfaces), decagon (10 flat side surfaces), or dodecagon (12 flat side surfaces) in shape. 0054] The antenna may be coupled to a Planar Ulira-Wideband Modular Array (PUMA) Antenna aray structure with a broadband anti-reflective layer added between the two devices. The anti-reflective layer marrics the two devices (Jens and PUMA) and creates a broadband impedance matching between the new modified Luneburg lens antenna and dipoles of the PUMA array while maintaining the capability of the system to transmit and receive signals in a plurality of octaves of bandwidth. Ultrawideband (UWB) Arvay Antenna Structure

[0055] An ongoing challenge with flat panel and phased array antennas has been to develop an antenna that is both ultra-wideband (UWB) and easily manaefacturable. There exist antennas that are wideband but not easily manufacturable (such as the Vivaldi array) and there are many different flat panel antennas that arc casily manufactured but which only operate over one or two frequency bands.

[0056] An antenna called the Planar Ultrawideband Modular Array (PUMA) that is both wideband (6:1 bandwidth} which is also manafacturable using standard Printed Circuit Board (PCB) processes by board houses using standard materials such as Rogers 3000 and 6600. U.S. Patent Application Publication No. 20§2 / 0146869.

[0057] UWB antennas such as the PUMA have the following properties that make them interesting for SATCOM and terrestrial microwave communications: (3) they can be manufactured by different PCB board houses using standard PCB processes: (b) they can be made wo operate UWB (6:1 bandwidth ratios are common}; and (¢) (hey retain good cross-polarization and gain performance up to 60 degrees scanned off-axis from boresite.

[0058] Figures 8 and 12 depict exemplary structures of a PUMA antenna. There is a trace layer, shown. in Figure 8 as Dipole Arms suspended above « ground plane by a dielectric layer and connected with vias to the layer shown as the ground plane. Above the trace layer there is an additionai dielectric layer shown in Figure 8. The spacing of the trace layer above the ground plane and the thickness and chosen material of the dielectric layers determines the frequency, bandwidth, and performance of this class of antennas. Connecting the Lens to the Array

[0059] The muluple flat sided modified UWB Luncbwry Lens provides the following benefits: (a) A flat- faced feed interface; (b) Inherently very wideband; (¢) These can now be manufactured using currently- available additive manufacturing techniques; (d) The shape of the fens inherently supports very wide- angle coverage (ap to -+ / - 90 degrees off boresite in a semi-hemispherical coverage pattern); and (¢) The lens is inherently efficient (efficiencies of 80% or greater ~ on par with parabolic reflectors).

[0060] The UWB antenna class such as a PUMA provides the following benefits: (a) Extremely wideband (6:1 bandwidth ratio) operation with directive signals; (b) Excellent off-axis performance up to iv 60 degrees off boresite in a serai-hemispherical coverage pattern: and (¢) Manafacuurable using standard PBC fabrication techniques.

[0061] A new class of UWB Luneburg Lenses are described herein that provide a flat (planar) interface in the southern hemisphere of the lens and surrounding the bottom hemisphere to which an antenna can be mated and connect that to an UWB planar array such as the PUMA. This new class of UWB lens antennas wtilizes a UWB antenna such as a PUMA as a feed network to ithuminate several cells of the Modified Luncburg Lens simultaneously.

[0062] This new class of UWB lens antennas has the following properties, among other properties: (a) Wideband frequency coverage (6:1 bandwidth ratio) allowing for operation in multiple frequency bands simultaneously; (b) Multiple simultaneous beams (potentially complete sky coverage with enough beams itluminated simultaneously); {¢) Wide area sky coverage (up to + / - 90 degrees of sky coverage in a semi- hemispherical pattern: (d) No moving parts required io operate: (0) Excellent efficiency relative to other directive antenna solutions (such as parabolic reflectors); and {f) A flat interface between the Modified Luncburg Lens and the UWB Antenna.

[0063] A high-level diagram of the proposed lens antenna system is depicted in Figures 8, 11, and 14. The figure depicts a multiple flat sided modified Luncburg lens fed by a PUMA antenna structure with or without an anti-reflective layer. The presence of the anti-reflective layer provides a broadband impedance matching and marry the two structures,

[0064] In a traditional UWB antenna such as a PUMA, the elements are spaced at one-half the wavelength at the highest frequency (3 / 2). This is because the UWB antenna traditionally phase- combines multiple elements to create a phased array of antennas. In this implementation, the antenna is using one (or a small number of) feed clement(s) to drive a single beam of energy. Tn the embodiments described herein, the UWB antenna is deviated from the traditional instantiation as follows: (a) The element location 1s dictated not by phased array formulas but instead by the location of the beams. Because of this, the elements will not necessarily be spaced at M2, and elements will not necessarily be evenly spaced, but insicad match the appropriate mapping of the modified Luneburg lens to cover a cell of area that wanslates to a specific direction out of the lens. (b) In the waditional UWB antenna, adjacent elements interact with one another and this interaction is integral to the operation of the UWB antenna in a phased array application. In embodiments described herein, the elements can operate independently of adjacent elements, so the nature of the interection between elements will be quite different.

[0068] In a traditional UWB antenna such as a PUMA, the top fayer of the anienna is matched to aiv / free space. In embodiments described herein, the UWB antenna structure will be matched to the lens via the anti-reflective layer. Because of this, the UWB antenna structure design described herein deviates quite significantly from other UWB antennas in at least the following ways. (a) The top layer of dielectric ina UWB antenna design will be integrated into the anti-reflective layer, or it will be replaced entirely by the anti-reflective layer. There will exist a single layer of material between the dipole layers of the UWB antenna and the modified Luneburg lens. This layer will be designed to provide good matching between the UWB antenna and the modified Luncburg lens. (b) Because the lens and the anti-reflective layer may not be homogenous across the interface surface, it is possible that, in addition to being spaced differently, the UWB antenna elements may have different designs at different points across the surface. The design criteria for the antenna is to have weli-behaved gain both spatially and across frequency. Having the ability to optimize the design of the lens, the anti-reflective layer, and the individual feed elements maximizes the efficiency and bandwidth of this invention.

[0066] In an embodiment, the UWB antenna array does not function as a phased array. Rather, individual elements of the UWB antenna function as individual feeds for individual beams aimed in separate directions through the ens. In Figure 13. the relationship between the adjacent feeds and the adjacent beams is depicted. The lens and feed are designed in such a way that adjacent feeds will correspond to adjacent antenna beams. Assuming all elements are spaced correctly. the beams will overlap in such a way as to allow simuhaneous illumination of an entire field of regard, in this case a field of roughly 60 degrees semi-hemispherical from boresite, By providing an RF switch matrix in the system that connects to alf of the beam ports, a desired single beam can be selected. Alternatively by using maltiple switch networks cach having its own wansmit receive moduics, a number of beams can be illuminated simultaneously.

[0067] As an example, a 25-cm. (10-in.) antenna has a hail power beamwidth on the order of 2.3 degrees at 30GHz. For the coverage of + / - 45 degrees, a total of approximately 675 beans and feeds are required. This is a circular array of UWB antenna feeds approximately 30 elements across. If the feed surface also has a diameter of 25-om., the feeds are spaced on the order of ¥-cm. apart.

[0068] The modified Luncburg fens antenna with PUMA may require low DC electrical power. In contrast, to achieve high beam scanning coverage with phased array, it requires multiple independent feed networks each having their own phase shiflers. With the PUMA coupled to the flattened sides of the modified Luneburg lens described herein, no phase shifters are necessary.

[0669] The modified Luncberg lens antenna described herein may be configured for muliiple simultaneous bears, potentially providing complete sky coverage with enough beams ihuminated simuftancously.

[0078] The modified Luncberg lens antenna described herein may be configured to provide wide area sky coverage (e.., ap to +i 90 degrees of sky coverage in a semi-hemispherical pattern.)

[0071] The modified Luneburg Jens fed by a PUMA antenna structure described herein may or may not have an anti-reflective layer. The presence of the anti-reflective layer provides « broadband impedance matching and marry the two structures.

[0072] The modified Luneberg lens antenna may have a wideband frequency coverage allowing for operation in multiple frequency bands simultaneously. The modified Luncberg lens antenna may have a 5:1 bandwidth ratio, 6:1 bandwidth ratio, 7:1 bandwidth ratio, 8:1 bandwidth ratio, 9:1 bandwidth ratio, 10:1 bandwidth ratio, 11:1 bandwidth ratio, 12:1 bandwidih ratio, 13:1 bandwidth ratio, or 13:1 bandwidth ratio.

[0073] While the present invention is described with respect to what is presently considered to be the preferred embodiments, it is understood that the invention is not limited to the disclosed embodiments, The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0074] Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. Tt is also understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to limit the scope of the present invention, which is limited only by the appended claims,

[0075] Although the invention has been described in some detail by way of iflustration and example for purposes of clarity of understanding. it should be understood that certain changes and modifications may be practiced within the scope of the appended clyims, Modifications of the above-described modes for carrying out the invention that would be understood in view of the foregoing disclosure or made apparent with routine practice or implementation of the invention to persons of skill in electrical engineering, telecommanications, computer science, and / or related fields are intended to be within the scope of the following claims.

[0076] All publications (e.g. Non-Patent Literature), patents, patent application publications, and patent applications mentioned in this specification ave indicative of the level of skill of those skilled in the art to which this invention pertains. All such publications (¢.g., Non-Patent Literature), patents, patent application publications, and patent applications are herein incorporated by reference to the same extent as if cach individual publication, patent, patent application publication, or patent application was specifically and individually indicated to be incorporated by reference.

Claims

Claims:

1. A modified Luneburg lens antenna comprising fattened side surfaces and a flat bottom, 2. The modified Luneberg lens antenna of claim 1, wherein the fens has 4, 6, 8, 10, or 12 flatiened side surfaces.

3. The modified Lancberg lens antenna of claim 1 or 2, wherein the flattened side surfaces are in the lower hemisphere of the lens.

4. The modified Luneberg lens antenna of any one of claims 1-3, wherein the flattened side surfaces are configured with a broadband anti-reflective {AR) layer.

5. The modified Luncburg lens antenna of claim 4, wherein the anti-reflective layer has an inhomogeneous graded diclectric permittivity profile.

6. The modified Luneburg lens antenna of claim 5, wherein the inhomogeneous graded dielectric permittivity profile is Klopfenstein, Exponential, Gaussian, or Triangular, 7. The modified Lancberg lens antenna of any one of claims 1-6, wherein the flattened side surfaces are configured with Planar Ulirawideband Modular Arrays (PUMA). X. The modified Loncherg lens antenna of any one of claims 1-6, wherein the Luncbery lens can achieve multiple simultancous beams on a 180° elevation plane and 360° azinwthal plane, optionally with high gain and low side-lobes.

9. The modified Luncherg lens antenna of any one of claims 1-8, wherein the Luneberg lens has an increased aperture efficiency of more than 80%, 10. The modified Luncberg lens antenna of any one of claims 1-9, wherein the intersection of the adjacent scanned beams can be designed to be about 1dB-3dB below to peak gain vahie, 11, The modified Luncberg lens antenna of any one of claims 1-10, wherein the Luneberg lens has a wideband frequency coverage. optionally a 6:1 bandwidth ratio, allowing for operation in nusltiple frequency bands simultaneously.

12. The modified Luncberg lens antenna of any one of claims 1-11. wherein the Lunebery lens is configured for multiple simultancous beams.

13. The modified Luncberg lens antenna of any one of claims 1-12, wherein the Luncberg lens is configured to provide up to + 90 degrees of sky coverage in a semi-hemispherical patter. i4. The modified Luneberg lens antenna of any one of claims 1-13, wherein the flattened side surfaces are configured with ultra-wideband (UWB) antenna structure.

15. The modified Luncberg lens antenna of claim 14, wherein the UWB antenna structure is matched to the lens via an anti-reflective layer.

16. The modified Luneburg lens antenna of claim 15, wherein the anti-reflective layer has an inhomogeneous graded diclectric permittivity profile.

17. The modified Luncburg lens antenna of claim 16, wherein the inhomogeneous graded dielectric permittivity profile is Klopfenstein, Exponential, Gaussian, or Triangular, 18. The modified Luneberg lons antenna of any one of claims 14-17, wherein the individual elements of the UWB antenna function as individual! feeds for individual beams aimed in separate directions through the lens.

19. A method for manufacturing a modified Luneburg lens comprising connecting the modified Luneburg fens to a PUMA antenna comprising removing the top dielectric layer of the PUMA antenna and using the pwlti-sided flattened Luneburg Lens to match the impedance of the dipole clements of the PUMA to the Luncburg lens.

20. The method of claim 19, wherein the method does not comprise matching the impedance to free space.

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