Structural topology optimization for the design of broadband dielectric resonator antennas using the finite difference time domain technique

Abstract

SUMMARYDielectric resonator antennas (DRAs) are a relatively new class of antenna that utilizes the radiation phenomena of dielectric resonators in open space. Since mainly analytical approaches have been applied to investigate DRA designs, the current DRA forms are limited to simple geometric shapes and highperformance DRAs with complex shapes have not yet been developed. Topology optimization is capable of yielding high-performance structures, and has been extensively applied to a variety of structural optimization problems. Applying it to the task of DRA design may be extremely useful for the design of high-performance antennas. On the other hand, the finite difference time domain (FDTD) method has been used to numerically evaluate general antenna performance, since it is numerically robust during time domain analyses and can handle complex models. Thus, the integration of topology optimization with the FDTD method has the potential to enable innovative designs of advanced antennas that offer exceptional performance. In this research, we propose a new topology optimization method for the design of DRAs that aim to operate with enhanced bandwidths, using the FDTD method. First, the concept of topology optimization is briefly discussed, and a way to integrate topology optimization with the FDTD method is proposed. Next, design requirements are clarified and the corresponding objective functions and the optimization problem are formulated. An optimization algorithm is constructed based on these formulations. Finally, several DRA design examples are presented to confirm the usefulness of the proposed method.

Length scale and manufacturability in density-based topology optimization

“…Following the idea of state solver re-utilization in the filtering process, the implementation of topology optimization problems with transient behavior, e.g., [110] would benefit from transient PDE filtering schemes. Based on regularization strategies utilized in image processing [16] a time dependent non-linear diffusion regularization scheme in topology optimization is proposed in [150] where the focus is mainly on reducing the gray transition regions by tuning the diffusion coefficient along the design edges.…”

Topology optimization of compact wideband coaxial-to-waveguide transitions with minimum-size control

“…To simulate the matched ports, the waveguide is terminated by a perfectly matched layer, and (3) together with boundary condition (4) provide perfect absorption of outgoing waves through the coaxial cable end. To control the frequency spectrum of the incoming energy, we use, as a feeding signal, a truncated time-domain sinc pulse modulated to the center of the frequency band of interest (Lathi 1998). The FDTD code is implemented to run on graphics processing units (GPUs) using the parallel computing platform CUDA (https://developer.nvidia.com/what-cuda).…”

“…During the last decade, topology optimization has started to be applied to the design of various electromagnetic components, such as antennas (Nomura et al 2007;Erentok and Sigmund 2011;Zhou et al 2010;Aage 2011;Hassan et al 2014b), metamaterials (Diaz and Sigmund 2010;Otomori et al 2012), and filters (Kiziltas et al 2004;Nomura et al 2013;Aage and Egede Johansen 2017). As opposed to classical topology optimization approaches applied to elastic material, the layout optimization of conducting materials suffers from an ohmic barrier issue.…”

Topology optimization for three-dimensional electromagnetic waves using an edge element-based finite-element method

“…For this complexity, physical intuitionbased electromagnetic structure design has its limitations. To overcome these bounds, several inverse design tests have been implemented based on structural optimization methods [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], in which the method employed most is the topology optimization method. Topology optimization is currently regarded to be the most robust methodology for the inverse determination of material distribution in structures that meet given structural performance criteria.…”