Optimization and Additive Manufacture of a Miniature 3-D Pixel Antenna for Dual-Band Operation

Abstract

This paper presents the design, manufacture, and experimental validation of a novel 3-D pixel antenna with volume-filling characteristics, and the design is based on our Method of Moments (MoM) solver that is efficiently coupled with a global/local optimizer for tailoring the antenna shape and concurrently selecting the location of the feeding port and shorting straps. The design, aimed at operating in the ISM bands of 2.45 GHz and 5.8 GHz, has dimensions under one-tenth of wavelength at the lowest frequency of operation. The optimization results are cross-validated using a commercial full-wave simulator, with a deviation of the reflection coefficient across the operating bands within 3%, showing also a high antenna efficiency of 99.6% and a gain of 1.06 and 4.53 dBi at the matching frequencies, with radiation patterns predominantly oriented towards the top hemisphere. Tolerance and parameter sensitivity studies were also performed. A scaled-up prototype of the antenna was built at a very low cost using standard additive manufacturing techniques, featuring a very good agreement between simulation and measurements, which proves the feasibility of this new kind of complex shape antennas in further applications where compact internal antennas are required.

Evaluation of a New Process for the Additive Manufacturing of Metal Antennas

“…Although PCB alternatives for building this kind of antennas have been documented, and conventional subtractive manufacturing approaches may be better suited for the shape herein considered. This geometry is chosen and tailored to validate the manufacturability of some complex 3D features such as cavities and the joints of vertical and horizontal walls which are pivotal in the manufacturing of intricate antenna geometries like the one in [9]. The antenna concept is inspired by the work in [22], where a planar "G"-shaped antenna with microstrip feed and dual-band operation is demonstrated and the work in [23], which introduces the term "cactus" antenna to describe a planar monopole loaded with one or two symmetrical sleeves, and the work in [24], in which a "fork"-shaped printed monopole for dual band operation is presented.…”

“…For these reasons, in fields where electrical rather than mechanical characteristics of metals are desired, e.g., electromagnetic design in microwaves and antenna engineering, alternative paths such as the metal cladding of structures made by AM of plastic materials have proven promising results as in [8] and enable the realization of designs that were inconceivable or only theoretically possible in the recent past as for example [9]. Some milestones on 3-D-printed antennas have been reached recently: horn antennas were made through Stereolithography (SLA) followed by a copper electroplating on top of a conductive silver ink layer in [10,11]; the fabrication of small antennas using a conductive ink for conformal printing on the surface of a 3D-shaped substrate introduced in [12]; a large reflector made by Nylon SLS and further coating with silver ink to achieve metallization presented in [13]; on the other hand we find the deployment of titanium and the later creation of a copper clad by vacuum sputtering of a selection of patch antennas produced by SLA presented in [14], and the variation presented in [15] with two steps metallization combining sputtering to create a thin copper (Cu) coating and a subsequent electroplating to attain a thick Cu layer.…”