In this work, design and realization of high performance, low-cost X-band multilayered cylindrical dielectric lens antenna (MLCDLA) is presented using 3D printing technology. Firstly, MLCDLA is designed and simulated in the complete 3D CST microwave studio (MWS) within the X-band as consisting of six layers and being fed through a conventional rectangular waveguide (WR90). These layers are in the form of cylindrical discs having different radii, thicknesses and made of a cheap polylactic acid material. These layers have also varying dielectric constant from 1.2 to 2.7 that are compatible for fused deposition modeling (FDM) based 3D-printing process. Secondly, a prototype of MLCDLA is produced by using a FDM based 3D-printer. 3D printed dielectric lens antenna is measured and a good return loss of almost more than 10 dB within the X-band with a high gain of 16-18 dBi are achieved as compared with the counterpart alternative designs. Thus, it can be concluded that the proposed novel design and prototyping method not only achieves the high radiation performance characteristics along X-band but also is a fast, low-cost, and effective method for prototyping dielectric lens structures for the microwave applications. K E Y W O R D S3D printer, broadband, high gain, lens antenna, nonuniform lens

In this work, computationally efficient design optimization of frequency selective surface (FSS)-loaded ultra-wideband Vivaldi antenna via the use of data-driven surrogate model is studied. The proposed design methodology consists of a multi-layer FSS structure aimed for performance improvement of the Vivaldi design, which makes the design a multi-objective multi-dimensional optimization problem. For having a fast and accurate optimization process, a data-driven surrogate model alongside the metaheuristic optimizer honeybee mating optimization (HBMO) had been used. The optimally designed antenna had been prototyped and its performance characteristics had been measured. The obtained experimental results are compared with the simulated results of the proposed method. Results show that the obtained FSS-loaded structure has enhanced directivity compared with the design without FSS structure, without any performance losses in the return loss characteristics. The FSS-loaded Vivaldi antenna operates at 2–12 GHz band with a maximum gain of 10 dBi at 10 GHz which makes the design a good solution for RADAR applications.

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Reflectarray antenna designs have become an efficient solution alternative to their counterpart designs due to their beam scanning capability, low profile, high gain, and mounting flexibility. Herein, design and realization of a wideband, flat gain multi-layer nonuniform reflectarray (MNURA) using 3D printing technology is presented. Design optimization of the proposed MNURA has been achieved in the two stages: First, a 3D CST Microwave Studio based Multilayer Perceptron Neural Network (MLP NN) model establishes the reflection phase characteristic of the MNURA unit element as an accurate continuous function of the geometrical design parameters and dielectric constant. Then Differential Evolutionary Algorithm DEA is selected as a powerful optimization algorithm for determining the optimum geometrical design parameters and dielectric constant of MNURA throughout the X-band to have a large range, wideband, and flat gain RA design. 3D printing technology has been used for prototyping of the proposed MNURA design. Here, the resulted optimum dielectric constant value of 2.2 is realized by 56% infill rate of "Polar White" PLA using the relation between the infill rate and dielectric constant. The prototyped antenna has a total size of 300 × 300 (mm), and its measured performance characteristics achieve a wideband flat gain of 23.2 dBi with a ripple level of almost 1.5 dBi and return loss characteristic of less than −10 dB over the operation band of 8 to 12 GHz. K E Y W O R D S 3D printer, flat gain, multilayer perceptron neural network, reflectarray, wideband, X-band 1 | INTRODUCTION Due to their beam scanning capability and being low profile, reflectarrays (RAs) have become an efficient solution alternative to their counterpart design of reflector and phased array antennas. RA designs are simply hybrid of a reflector antenna and a planar phased array antenna which has a suitable phasing scheme in order to convert the incoming spherical wave produced by a feed antenna into a pencil beam in a specified direction. 1-4 With respect to their unique features of high gain, mounting flexibility, and being planar, Microstrip Reflectarray (MRA) designs have a wide range of applications such as space, radar, and long-distance communication applications. 5 However, these designs suffer from disadvantage of having a narrow bandwidth characteristic. Thus, the narrow bandwidth characteristics caused by intrinsic narrow bandwidth of a microstrip patches and spatial phase delays between the feed and unit cell elements 6 is a challenging design problem.

In this work, design of a pattern reconfigurable antenna is presented for X‐band applications as a leaky wave antenna (LWA) realization. Due to the advantages of simple design schematic, low profile, and easy impedance matching, LWA designs have been using as an efficient solution for reconfigurable antenna in many wireless communication applications. Optimization and simulation of the proposed LWA is carried out in 3‐D Microwave simulation CST environment and Honey Bee Mating is used as the optimization algorithm. Dimensions of the proposed LWA is 130 × 30 mm, which is fabricated on Rogers 5880 as capacitive loaded eight identical rectangular microstrip patches operating over 9.5‐12 GHz with a fractional bandwidth. The proposed LWA exhibits a measured peak gain of 11.8 dBi at 10 GHz with an overall gain characteristic of between 9.5 and 11.8 dBi over the range of 9.5 to 12 GHz with a steerable pattern characteristics between −45 and 50° as agreed with the theory. Furthermore, the fabricated LWA has been found to have the superior performance as compared with its counterparts.