A Method for Optimising Superdirectivity of Coupled Meta-Atoms via Planar Directivity Evaluation

Abstract

We propose a simple and rapid way of optimising directivity in metamaterial-inspired endfire antenna arrays with strong interelement coupling. We introduce, in addition to the traditional 3D directivity, also its planar equivalents defined as the ratio of the power density in the desired endfire direction to the average power density calculated either in the horizontal (azimuthal) or vertical (elevation) plane. Using dimers of magnetically coupled split-ring resonators with only one element driven by an external source, we derive conditions that must be satisfied in order to realise superdirective current distributions. The superdirective conditions link the quality factor of the resonators and their coupling constant to the array size and the operating frequency. We demonstrate that a rapid measurement in the azimuthal plane can be used as a reliable indicator for whether the superdirective conditions for the 3D directivity are satisfied. Analytical calculations are verified by CST simulations in the MHz frequency range for meta-atoms of circular and square shape. Our method can be extended to arrays comprising larger number of meta-atoms of various shape and would enable rapid prototyping of 3D-printed meta-atoms with desired radiation properties.

Genetically Synthesized Supergain Broadband Wire-Bundle Antenna

“…These algorithmic approaches were introduced into engineering problems in the 1960-70s 27 and since then, being supported by ever-growing computational power, started to shift aside from conventional design rules, e.g., 28,29 . In the context of this report, it is worth mentioning existing studies looking into circular rods superscatterers 30 , superabsorptive nanoparticles 31 , coreshell cylindrical superscatterers 32 , subwavelength superscattering nanospheres 33 , antenna design, nanoplasmonic particles 23,34,35 , and others [36][37][38][39][40][41][42] .…”

A Tutorial on Holographic MIMO Communications—Part III: Open Opportunities and Challenges

“…Moreover, implementing super-directivity by relying on metamaterial elements may not require separately exciting each individual element. Specifically, Yan et al [14] proposed an efficient technique for optimizing the directivity in metamaterial-inspired end-fire antenna arrays having strong inter-element coupling. As shown in Fig.…”

Efficient Design of Super-Directive Antenna Array using Schelkunoff Method and Genetic Algorithm

“…However, by reducing the separation distance and using appropriate excitation functions, the mutual coupling effect between array elements can be compensated through the optimized excitations of the super-directive feed network. Composite polynomials have been widely utilized to generate efficient array excitation functions [1] - [5] that lead to a 20-30% reduction in the half-power beam width. However, for an N-element antenna array with an overall length of several wavelengths, the computational time and design challenges in realizing the array excitation functions have hindered the application of this class of super-directive arrays [6] - [14].…”