Modern Antenna Design

This article introduces retroreflective lenses for millimeter-wave radio-frequency indoor localization. A three-dimensional (3D) gradient-index Luneburg lens is employed to increase radar cross section (RCS) of photonic-crystal high-Q resonators and its performance is compared to conventional radar retroreflectors. A classic Luneburg lens with and without a reflective layer is realized with 25 mm diameter ( $6.7~\lambda _{0}$ ), showing a realized gain of 24.6 dBi and a maximum RCS of −9.22 dBm2 at 80 GHz. The proposed Luneburg lens with embedded high-Q resonators as frequency-coded particles in a photonic crystal structure, operating as a reflective layer, achieved a maximum RCS of −15.84 dBm2 at the resonant frequency of 76.5 GHz and showed a repeatable response each 18° over ±36° in two perpendicular planes. With this high RCS of the Luneburg lens, a maximum readout range of 1.3 m could be achieved compared to 0.15 m without the lens at 76.5 GHz for the same transmit power, receiver sensitivity, and gain of the reader antenna.

/pdf/gradient-index-based-frequency-coded-retroreflective-lenses-3t33xw7q3l.pdf

Gradient-Index-Based Frequency-Coded Retroreflective Lenses for mm-Wave Indoor Localization

In this work we present a method for fabricating three dimensional, ultralight and flexible millimeter metamaterial units using a commercial household 3D printer. The method is low-cost, fast, eco-friendly and accessible. In particular, we use the Fused Deposition Modeling 3D printing technique and we fabricate flexible conductive Spilt Ring Resonators (SRRs) in a free-standing form. We characterized the samples experimentally through measurements of their spectral transmission, using standard rectangular microwave waveguides. Our findings show that the resonators produce well defined resonant electromagnetic features that depend on the structural details and the infiltrating dielectric materials, indicating that the thin, flexible and light 3D printed structures may be used as electromagnetic microwave components and electromagnetic fabrics for coating a variety of devices and infrastructure units, while adapting to different shapes and sizes.

https://www.mdpi.com/1996-1944/13/17/3879/pdf

Flexible 3D Printed Conductive Metamaterial Units for Electromagnetic Applications in Microwaves.

This article presents a parametric study of a fully 3D-printed hemispherical dielectric resonator antenna (DRA) using low loss dielectric filament and high-conductive filaments jointly with a low-cost customized dual-extruding 3D printer. The parametric study consisted in the design and evaluation of five different hemispherical DRA topologies with different internal shapes and the same overall size, in which the printing infill percentage of the DRA was reduced. A 3D-printed metallic cap was included in the antenna to compensate for the resonant frequency shift in order to maintain its original dimensions. Measurement results show that all evaluated antennas kept the same resonant frequencies and similar radiation patterns while reducing the overall weight of the topology in 22% of the nominal weight.

/pdf/parametric-study-of-a-fully-3d-printed-dielectric-resonator-1sn9zntrat.pdf

Parametric Study of a Fully 3D-Printed Dielectric Resonator Antenna Loaded With a Metallic Cap

This article presents a fully 3D-printed dielectric planar lens operating in the entire Ka-band manufactured using additive manufacturing and a relatively low-cost 3D-printer. The lens consists of ten concentric rings implemented using low-loss ABS filaments with high permittivity values. By varying the infill percentages of them the required refractive indexes of each section are achieved. An additional 3D-printed matching layer, using the same manufacturing and design method was included in the lens, to reduce reflections. Simulation and measurement results show a very good agreement, which confirms the possibility of manufacturing a cost-effective broadband and planar lens solution operating in millimeter wave bands, where Low Earth Orbit Satellites (LEO) networks, future mobile communication systems (5G, 6G) and radar systems operate. 

/pdf/cost-effective-wideband-dielectric-planar-lens-antenna-for-1qj8o0do.pdf

Cost-effective wideband dielectric planar lens antenna for millimeter wave applications

In this letter, we propose and study a 2-D glide-symmetric dielectric periodic structure. We demonstrate that glide symmetry broadens the bandwidth of operation and achieves lower effective refractive indices when compared to non-glide configurations. These two properties are beneficial for producing graded-index lens antennas. To demonstrate the potential of the proposed unit cell, we designed a Luneburg lens operating in the K- and K $_\text {a}\!$ -bands. The lens was manufactured with conventional additive manufacturing and it has a potential use for future wireless communications given its low-cost and low-profile.

/pdf/two-dimensional-glide-symmetric-dielectric-structures-for-4q8ucgw3my.pdf

Two-Dimensional Glide-Symmetric Dielectric Structures for Planar Graded-Index Lens Antennas

This article presents the design, construction and analysis of a 3D-printed transformed hyperbolic flat lens working on the 30 GHz band. The transformed lens was printed using only one ABS dielectric filament of relative permittivity of 12, varying the infill percentage of each transformed lens section in order to achieve the permittivity values obtained with the transformation optics. The 3D-printed hyperbolic transformed lens exhibits good radiation performance compared to the original canonical lens.

https://www.mdpi.com/1996-1944/13/12/2700/pdf

3D-Printing for Transformation Optics in Electromagnetic High-Frequency Lens Applications.

A flat wideband lens antenna operating in the Ka band is presented. The design corresponds to the transformation of a hyperbolic lens via quasi-optic transformation into a flat lens. The implementation of the lens is made using 3D printing technology as it allows cheap and precise manufacturing of the complicated shapes obtained with the transformation. The required refractive indices are calculated and implemented with varying infill percentages of the used filaments in each transformed layer. The experimental results show excellent agreement with the simulations, including low losses. The presented design is a low-cost antenna with the measured gain above 23 dBi in the whole Ka band (26.5–40 GHz).

Wideband hyperbolic flat lens in the Ka-band based on 3D-printing and transformation optics

This article presents the design of a 3D-printed wideband planar graded index (GRIN) lens operating on the Ka band from 25 to 40 GHz. The frequency band was chosen to cover candidate frequencies for the new 5G technology such as 28 and 38 GHz bands. The designed lens is composed of ten concentric rings. The lens shows a good wideband behavior, with a maximum gain on the broadside above 25 dB on the whole band. For the construction, the lens will be manufactured using 3D-printing with low-loss dielectric filaments. The different permittivity values of each ring are obtained by varying the infill percentage of the sections on the 3D-printing process.

Jose-Manuel Poyanco

Papers

Two-Dimensional Glide-Symmetric Dielectric Structures for Planar Graded-Index Lens Antennas

3D-Printing for Transformation Optics in Electromagnetic High-Frequency Lens Applications.

Cost-effective wideband dielectric planar lens antenna for millimeter wave applications

Wideband hyperbolic flat lens in the Ka-band based on 3D-printing and transformation optics

3D-printed dielectric GRIN planar wideband lens antenna for 5G applications