High-Efficiency, Wideband GRIN Lenses With Intrinsically Matched Unit Cells

Garcia, Nicolas; Chisum, Jonathan

doi:10.1109/tap.2020.2990289

Cited by 36 publications

(36 citation statements)

References 35 publications

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“…The optimizer is first seeded with a matched unit-cell design with reasonable performance: the matched unit-cells and preliminary lens design are generated using the matched unitcell library and design algorithm in Garcia and Chisum. 6 The permittivity cut across the core of the lens is then fitted to a function and the constituent parameters are optimized for various cost functions using MATLAB's built-in Nelder-Mead simplex algorithm. 19 In each design iteration the lens is characterized in a 2D FDTD full-wave electromagnetic solver.…”

Section: Metamaterials Grin Lens Optimizermentioning

confidence: 99%

“…In principle any GRIN media technology (including metallo-dielectric GRIN 4 ) could be used to realize the prototype but the all-dielectric approach discussed in Garcia and Chisum. 6 is preferred here for its improved bandwidth and proven compatibility with the matched unit-cell approach. The prototype lens was fabricated with drilled perforated dielectrics in multiple Rogers AD-Series substrates: AD250, AD350 and AD1000 with ε host values of 2.5, 3.5, and 10.2, respectively.…”

Section: Prototype and Measurementsmentioning

confidence: 99%

“…Lens antennas have the potential to serve as a low-power, frequency-independent aperture for these bands and have seen reduction in cost, mass, and volume as a result of emerging metamaterial GRIN technologies including alldielectric, and metallo-dielectric media. [2][3][4][5][6] An arbitrary GRIN lens with a 3D permittivity profile provides many degrees of freedom which can be reliably fabricated up to low millimeter-wave bands with either additive 7,8 or subtractive 5,6 manufacturing. With such flexibility in design and fabrication, compact lenses which simultaneously satisfy multiple performance objectives (e.g., wideband performance and high aperture efficiency) are possible.…”

Section: Introductionmentioning

confidence: 99%

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Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

Garcia

Chisum

2020

Micro & Optical Tech Letters

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In this article we present a method for the rapid design of wideband, high efficiency metamaterial GRIN lenses with rotational symmetry. The method achieves rapid optimization by reducing the number of optimized parameters while maintaining wideband impedance matching for high aperture efficiency. For rotationally symmetric lenses with isotropic GRIN media it is sufficient to design a two-dimensional (2D) cross section. By using intrinsically matched unit-cells which prescribe a permittivity gradient along the axis of beam propagation the optimizer only needs to define the transverse permittivity gradient along a line, reducing the design domain from three dimensions (3D) to a single dimension (1D). At each step of the optimizer a 2D finite-difference-timedomain code rapidly solves each realization of the GRIN lens cross-section across a wide bandwidth. We demonstrate the proposed method by optimizing and fabricating a 4-inch GRIN lens which achieves 60%-65% measured aperture efficiency from 26 to 40 GHz. The prototype lens provides a high-efficiency aperture for Ka-band satcom and 5G millimeter-wave bands and the approach is suitable for higher future millimeter-wave bands in 6G and beyond networks.

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Section: Metamaterials Grin Lens Optimizermentioning

confidence: 99%

Section: Prototype and Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

Garcia

Chisum

2020

Micro & Optical Tech Letters

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“…5G millimeter‐wave bands already coexist with the Ka‐band fixed‐satellite service (FSS) allocations (27.5–30 GHz) and strategies are being investigated to mitigate interference 4 . Single apertures capable of servicing existing and future satellite communications bands (e.g., 12.5, 14.25, 20/30 GHz) and 5G MMW bands (e.g, 28, 39 GHz) have been demonstrated 5 but to maintain efficiency they require a feed, which can provide a constant edge‐taper over frequency 6 . In addition, such wideband apertures are vulnerable to significantly more interference across such “wide open” front‐ends.…”

Section: Introductionmentioning

confidence: 99%

“…Tuning switches short various segments of the antenna, which resonates in 3.9 or 6.2 GHz sub-bands. In 11,12 the wideband antenna covers the UWB-band (3)(4)(5)(6)(7)(8)(9)(10)(11) and four switches are used to select various sub-bands.…”

Section: Introductionmentioning

confidence: 99%

VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Connelly

Chisum

2020

Micro & Optical Tech Letters

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In this article, we demonstrate a reconfigurable antenna concept based upon a film of vanadium dioxide (VO2) with embedded metallic surface inclusions to increase radiation efficiency. We fabricate a monopole antenna with the proposed film, demonstrate a good match between measurement and simulation, and propose methods for increasing performance. We show that the addition of metallic inclusions in the VO2 film results in a 37‐fold increase in the radiation efficiency. This concept, if paired with a spatially addressable micro‐heater array, could enable extremely flexible and low‐loss frequency‐agile cognitive radio antennas for dynamic spectrum applications as well as polarization and pattern reconfiguration for operation in 5G and beyond systems where spectrum is congested and coexistence is compulsory.

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Compact Multifunctional Gain Enhancing GRIN Lens for Widely Separated Frequency Band Shared Aperture Antennas

Whiting

Campbell

et al. 2023

Advanced Optical Materials

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these solutions, gradient index (GRIN) lenses have shown tremendous potential due to their ability to manipulate electromagnetic wave propagation in the desired way by exploiting their tailored spatiallyvarying permittivity profiles. GRIN lenses have been used to reduce the size of existing antennas, [15,16] reduce sidelobe levels, [17,18] and enhance gain. [19][20][21] To fabricate any GRIN lens, one must have the ability to tune the dielectric permittivity throughout the lens volume. To this end, perhaps the most common approach is to vary the volume fraction of two materials to create an effective permittivity. This is often achieved by mixing a base dielectric material and air and is realized through the introduction of negative inclusions (i.e., holes) whose relative size is used to tune the local permittivity value. [22,23] This can easily be accomplished with additive manufacturing techniques (i.e., 3D printing). [21,[24][25][26][27] Historically, 3D-printed GRIN lenses have been mainly created from plastics. However, ceramic materials offer a much larger range of relative permittivity values than plastics which designers can exploit to realize significant performance improvements over conventional GRIN lenses. A significant contribution of this work is the demonstration of a functionalized ceramic GRIN lens produced via a state-of-the-art additive manufacturing process. Alternatively, GRIN lenses have been realized with metamaterials consisting of engineered metal-dielectric unit cells. [28,29] Compared to those based on metamaterials, all-dielectric GRIN lenses can be bulky and heavy; however, all-dielectric GRIN lenses often operate over much broader bandwidths with lower losses than those based on metamaterials as they do not rely on resonant effects. In addition, all-dielectric lenses are often better suited for high power applications due to the complete absence of metal and the elimination of large local field enhancement hot-spots on the edges/corners and in the capacitive gaps of the metamaterial unit cells.Common GRIN lens solutions have been realized using analytical approaches (e.g., the Luneburg lens [30] and Maxwell fisheye lens [31] ), geometrical optics, [32,33] Transformation Optics (TO), [34][35][36] or the field transformation approach. [37] Among these approaches, TO has been the predominant method for its ability to recreate the performance of conventional solutions in more desirable geometries. For example, the flattened Luneburg lens has been demonstrated for a variety of beam steering and multibeam applications. [38][39][40][41] However, it is not Gradient index (GRIN) lenses embody a powerful technology that enables control of electromagnetic wave propagation over wide frequency bands. However, GRIN lenses that achieve multifunctional (i.e., dual broadband) performance have not been realized mainly due to the limitations of conventional techniques such as Transformation Optics (TO). This paper proposes a multiobjective inverse-design approach for the optimization of multi-band GRIN...

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High-Efficiency, Wideband GRIN Lenses With Intrinsically Matched Unit Cells

Cited by 36 publications

References 35 publications

Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Compact Multifunctional Gain Enhancing GRIN Lens for Widely Separated Frequency Band Shared Aperture Antennas

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High-Efficiency, Wideband GRIN Lenses With Intrinsically Matched Unit Cells

Cited by 36 publications

References 35 publications

Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

Reduced dimensionality optimizer for efficient design of wideband millimeter‐wave 3D metamaterial GRIN lenses

VO2 antennas with metallic inclusions for low‐loss reconfigurable cognitive radios

Compact Multifunctional Gain Enhancing GRIN Lens for Widely Separated Frequency Band Shared Aperture Antennas

Contact Info

Product

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VO₂ antennas with metallic inclusions for low‐loss reconfigurable cognitive radios