Antonios X. Lalas

Tunable terahertz metamaterials by means of piezoelectric MEMS actuators

A programmable THz metamaterial, derived from the utilisation of a piezoelectric controlled microgripper as a split-ring resonator (SRR), is introduced in this paper. By applying the appropriate actuation voltage on the piezoelectric microelectromechanical systems (MEMS), a reconfigurable complex medium, offering enhanced bandwidth tunability, is attained. Several polarisation topologies are examined in order to clarify the interesting attributes of the metamaterial. Finally, thorough numerical investigations, via a robust finite element method (FEM), support the efficiency and reveal the advantages and applicability of the proposed device.

Powering nanonetworks by exploiting metamaterial-inspired wireless energy transfer

An elaborate investigation regarding the efficiency of a novel metamaterial-based wireless power transfer (WPT) system, capable of delivering useful energy to the nodes of a nanonetwork, is systematically pursued in this paper. The WPT apparatus incorporates metamaterial fundamental blocks as its elementary resonators to exploit magnetic resonance coupling. The proposed arrangement unveils a noteworthy enhancement of the power supplied to the load as well as a promising minimization of the interaction with adjacent nanodevices.

Efficiency enhancement of metamaterial-inspired wireless energy transfer topologies

The significant efficiency improvement along with the relevant performance assessment of a wireless power transfer (WPT) system, is comprehensively pursued in this paper. The new device involves several arrangements of metamaterial components as its principal resonators. Moreover, a detailed examination regarding the competence of the proposed topology reveals a noteworthy advancement of the power delivered to the load.

Accelerating FDTD Simulations for Eigenfrequency Detection in EBG Devices by Means of the GPOF Method

In this paper, a technique introducing the generalized-pencil-of-function (GPOF) algorithm as a post processing procedure in the finite-difference time-domain (FDTD) method is presented to facilitate the study of electromagnetic bandgap (EBG) devices. Correction criteria are also developed to deal with erroneous eigenfrequencies associated with computational noise. The numerical results obtained are considered sufficiently accurate, while the potentials of this approach are thoroughly discussed.

Optimized wireless power transfer schemes with metamaterial-based resonators

A systematic technique for the accurate implementation of electromagnetic resonance-based wireless power transfer (WPT) implementations by means of diverse metamaterials is presented in this paper. To this aim, two distinct resonating elements are selected, i.e. the edge-coupled split ring resonator (EC-SRR) and the E2 SRR. In particular, the macroscopic properties of these elements are precisely retrieved and the preceding SRRs are then incorporated in the featured WPT scheme. The performance of the system, including the magnetically resonant SRR, is proven to be very promising for distances within a few centimeters, as expected from the initial theoretical analysis, contrary to the case of the electrically resonant elements.

Circular and square SRR exploitation as a means for wireless power transfer

As wireless power transfer (WPT) systems emerge, the efficiency and achievable transmitting distance are two constraining factors for their prevalence over wired ones. In this paper, two split ring resonator (SRR)-based WPT configurations, with circular and square SRRs, as their transmitting and receiving elements, are investigated for various frequencies and distances. The efficiency is found to be very satisfactory in both cases, exceeding 98% for certain sets of parameters. Thus, the general response of both arrangements seems to be promising for effective power transfer over distances of a few centimeters.

Wireless power transfer via negative permittivity metamaterials as resonating elements

A negative permittivity type of split-ring resonator (SRR) is proposed as an efficient resonating component for wireless power transfer (WPT) systems, functioning via electromagnetic resonance. The principal properties of the SRR are firstly studied and introduced as a guide for the WPT system. The overall efficiency varies depending on the values of the system parameters and is proven to be very satisfactory, as successfully validated by an assortment of realistic applications.

Exploitation of Piezoelectric Micro-Devices as Building Blocks of Controllable Terahertz Complex Materials

A reconfigurable THz complex medium, consisting of fundamental piezoelectric micro-devices, is introduced in this paper. By actuating the piezoelectric modules, a controllable metamaterial, presenting enhanced bandwidth tunability, is accomplished. Two diverse polarization topologies are examined, revealing the anisotropic performance of this material. The advantages of the proposed component are sufficiently clarified through several numerical data, derived by a robust finite element method (FEM).

Metamaterial-based wireless power transfer through interdigitated SRRs

Purpose – Wireless power transfer (WPT) is deemed as an emerging technology with exciting applications, like wireless charging devices, and electric vehicles, whereas metamaterials exhibit exceptional properties. For every WPT system that occupies coupled magnetic resonances, it is also mandatory to involve resonators. The purpose of this paper is to introduce a new interdigitated split-ring resonator (I-SRR) as the basic part of a WPT system, pursuing advanced levels of efficiency. Design/methodology/approach – A novel WPT system, which exploits I-SRRs as its elementary blocks, is comprehensively examined. The analysis investigates the distance between the modules, the distance between transmitting and receiving components as well as the geometrical features of the structure. Several numerical data derived via the finite element method unveil the merits of the featured configuration. Findings – The proposed arrangement reveals a noteworthy enhancement of the power delivered to the load and a promising tu...

Piezoelectrically programmable electric-field driven LC (ELC) resonators acting as THz modulators

Purpose – Metamaterials are artificially tailored complex media with extraordinary properties, not available in nature. Due to their unique performance, they are considered as a crucial component of modern radio-frequency technology, especially in the THz regime. However, their lack of wide spectral bandwidths introduce constraints for realistic applications. The purpose of this paper is to propose piezoelectric micro-electromechanical systems (MEMS) actuators to modify the shape of electric field-driven LC (ELC) resonators. A THz modulation capability is revealed by connecting/disconnecting the associated metal parts. Design/methodology/approach – Piezoelectric MEMS actuators are proposed to provide the desired bandwidth enhancement along with THz modulation. Two setups with different degrees of freedom in altering the behaviour of the novel modulator are investigated. A variety of numerical data, acquired via the finite element method, substantiate the advantageous characteristics of the proposed struct...