Constantinos Zekios

Constantinos Zekios
Florida International University | FIU · Department of Electrical and Computer Engineering

Doctor of Philosophy

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119
Publications
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Introduction
Skills and Expertise

Publications

Publications (119)
Article
Full-text available
A rigidly foldable and reconfigurable origami antenna is developed here. This antenna uses thick folding panels thereby providing robust operation and folding/unfolding actuation, which are very important for many applications in extreme environments, such as space. Also, this antenna can be constructed using standard printed circuit boards, which...
Article
In the above article [1] , there was a misplaced reference that it might create confusion for anyone interested on re-creating or verifying our results. Specifically, in Table VIII, we mention that we used reference [32] to evaluate the results marked by an asterisk that were not readily available. The correct reference is from Chang et al. [2]...
Article
Full-text available
Butler Matrix networks are well established as beamforming networks for phased antenna arrays. The challenge we address in this work is to cover the entire (advanced 5G or 6G) FR3 band (7–24 GHz) with a single network, while retaining low losses and minimal size. The employed multilayer topology is also well established; however, the matching betwe...
Article
Full-text available
Two of the main challenges in origami antenna designs are creating a reliable hinge and achieving precise actuation for optimal electromagnetic (EM) performance. Herein, a waterbomb origami ring antenna is introduced, integrating the waterbomb origami principle, 3D‐printed liquid metal (LM) hinges, and robotic shape morphing. The approach, combinin...
Preprint
Full-text available
Butler matrix networks are well established as beam forming networks for phased antenna arrays. The challenge we address in this work is to cover the entire, (advanced 5G or 6G), FR3 band (7-24 GHz) with a single network, while retaining low losses and minimal size. The employed multilayer topology is also well established, however, the matching be...
Article
Full-text available
Ensemble modeling has been widely used to solve complex problems as it helps to improve overall performance and generalization. In this paper, we propose a novel TemporalAugmenter approach based on ensemble modeling for augmenting the temporal information capturing for long-term and short-term dependencies in data integration of two variations of r...
Article
Full-text available
Smart home control systems have been widely used to control multiple smart home devices such as smart TVs, smart HVAC, and smart bulbs. While targeting the design of a smart home environment, the accessibility of the entire system is crucial to achieving a comfortable and accessible environment for all home individuals. Thus, in this paper, we are...
Article
In this work, we investigate the theoretical limitations of the frequency pulling technique (FPT), a newly introduced technique that uses the insertion loss design methodology of bandpass filters for increasing the bandwidth of antennas. Notably, we show that by applying the FPT on antennas, the maximum theoretical impedance bandwidth defined by th...
Article
This work introduces a new class of low-cost, passive, planar, multibeam, true-time-delay millimeter wave (mmWave) beamforming networks that scan in both azimuth and elevation plane. Namely, the traditional Blass matrix topology, which is capable of exciting M beams in a linear array of N antenna elements, is redesigned to excite M beams in a...
Article
Full-text available
This study investigates the use of deep learning techniques for building a generalized surrogate model that can accurately and very efficiently predict antenna performance parameters. Notably, we focus on applications where a substantial amount of simulation time is required and prior data is available for deep learning use. Specifically, for these...
Article
This work introduces a novel synthesis method for optimal efficiency multibeam networks. Our design method can create networks able to excite any set of non-orthogonal beams with the optimal power efficiency as dictated by Stein’s limit. To achieve this, we decompose the desired non-orthogonal excitation matrices to two orthogonal and one diagonal...
Article
Full-text available
This work presents a deep neural network (DNN)-based approach for identifying the modal field distributions of closed non-radiating waveguides. Specifically, physics-informed neural networks (PINNs) are used to solve the Helmholtz partial differential equation. The PINN architecture includes incorporation of boundary conditions and selection of ini...
Article
It was Bode in 1930 [1] that sparked the conversation about impedance matching using multiple elements/stages. In 1945 [2] he was the first to evaluate the theoretical maximum limit achievable for the quality factor-bandwidth ( QB ) product when employing an infinite number of impedance matching networks (this is the perfect impedance matching tha...
Article
Full-text available
Abstract Holographic phase-shifting surfaces (PSSs) have been proven to offer a cost-effective solution for enabling passive arrays to mechanically steer their beams toward desired directions. However, even though the principle of operation of PSSs is straightforward, designing a PSS is very challenging, because it involves an extremely high comput...
Article
Full-text available
Frequency pulling technique (FPT) is a recently developed method for increasing the bandwidth (BW) of microstrip antennas. It is based on the insertion loss methodology used for the design of bandpass filters. Namely, to apply this technique, the resonators in a bandpass filter are replaced with antennas that have identical equivalent resonant circ...
Article
This work introduces a new class of ultra-wideband beamforming networks that covers the legacy sub-6 GHz bands for both traditional and fifth generation (5G) satellite and terrestrial communication systems. To cover the multi-octave sub-6 GHz bandwidth, we translate the microwave-photonics concept, to the radio frequency-millimeter waves (mm-waves)...
Article
This work introduces a multiple-input multiple-output (MIMO) channel model to characterize propagation in a small satellite swarm environment. By using the Rician $K$ -factor, this model appropriately combines fixed line-of-sight (LoS), satellite-reflected, and earth-reflected (ER) channel components with a randomly varying diffuse component that...
Article
Full-text available
Microwave absorbers have been used to mitigate signal interference, and to shield electromagnetic systems. Two different types of absorbers have been presented: (a) low-cost narrowband absorbers that are simple to manufacture, and (b) expensive wideband microwave absorbers that are based on complex designs. In fact, as designers try to increase the...
Article
Full-text available
A novel Green’s function-free characteristic modes formulation is introduced in this work. The desired impedance or admittance matrix is obtained utilizing and appropriately modifying the versatile finite element method. For this purpose, the generalized eigenvalue problem of the electric or magnetic field vector wave equation is formulated. In the...
Article
In a multi-objective optimization process, several goals are traditionally combined into a single fitness function. In such cases, the choice of the objective function is critical, as it should accurately represent the desired optimization goals. Here, we introduce a new class of multi-objective functions with non-linearity and switching behavior,...
Article
Full-text available
This work introduces an extremely low profile ( $0.4\lambda _{high}$ ) planar ultra-wideband dual-polarized reflectarray. The unit-cell structure of the array is modular in nature, and without any electrical connection between adjacent unit-cells. The array uses tightly coupled dipoles arranged in an egg-crate fashion connected with true-time-dela...
Article
A novel leaky-wave antenna (LWA), which operates at the $TM_{11}$ high-order mode, is proposed. This LWA achieves a 4.6 times higher gain than the traditional TE10-based LWAs. An analytical formulation is derived, which shows that a $TM_{11}$ -based LWA couples more energy to free space through an appropriately designed slot than traditional TE...
Article
In this work, a new method is proposed to derive the initial approximate model for a multi-fidelity surrogate optimization. Specifically, the proposed method is trained using a set of eigenfunction expansions that characterizes the solution domain of the desired geometry and high-fidelity full-wave simulations. To demonstrate and validate the propo...
Article
Full-text available
In this work, we present a rigorous full-wave eigenanalysis for the study of nanoantennas operating at both terahertz (THz) (0.1–10 THz), and infrared/optical (10–750 THz) frequency spectrums. The key idea behind this effort is to reveal the physical characteristics of nanoantennas such that we can transfer and apply the state-of-the-art antenna de...
Article
Full-text available
The field of foldable and physically reconfigurable antennas has recently attracted significant interest from diverse scientific communities, including researchers on antennas, material science, mechanical engineering and numerical modeling. Deployable, packable and multifunctional systems are very important for many applications, including satelli...
Article
Origami electromagnetic (EM) structures are promising technologies for deployable and reconfigurable EM structures such as antennas and frequency-selective surfaces (FSSs). However, these structures present CAD modeling difficulties due to their complex geometries. Studying the effects of origami substrate folding on EM performance demands multiple...
Article
This paper presents a thick origami foldable traveling wave antenna. A typical microstrip rampart-line antenna is appropriately modified to enable folding/unfolding capability using a surrogate hinge. This antenna is designed on a 1:5 mm thick FR4 substrate circularly polarized at 3:4 GHz and exhibits a peak gain of approximately 2:85 dB at broadsi...
Article
Full-text available
In this paper, an elegant approach is presented for designing multi-band multi-mode rectangular microstrip antennas (MSAs) with high isolation between the bands. The coupling properties of a gap (an extended slot), which is introduced in a rectangular MSA operating in the TM010 and TM100 modes, are first qualitatively explained through field equiva...
Patent
Full-text available
Arrays that are deployable and can change their electromagnetic behavior by changing their shape are provided. An array can include a central panel and at least one foldable panel attached thereto. The central panel can include radiating elements on its upper surface while each foldable panel can have radiating elements on its bottom surface. The a...
Article
Full-text available
Millimeter wave (mm-Wave) technology is likely the key enabler of 5G and early 6G wireless systems. The high throughput, high capacity, and low latency that can be achieved, when mm-Waves are utilized, makes them the most promising backhaul as well as fronthaul solutions for the communication between small cells and base stations or between base st...
Article
Full-text available
Frequency selective surfaces (FSSs) have been used to control and shape electromagnetic waves. Previous design approaches use complex geometries that are challenging to implement. With the purpose to transform electromagnetic waves, we morph the shapes of FSS designs based on origami patterns to attain new degrees of freedom and achieve enhanced el...
Article
This article presents the first foldable thick-origami based antenna array made of a single nonflexible (rigid) printed circuit board (PCB), which can be easily fabricated using a standard milling machine. The foldability of the design is achieved using a surrogate hinge architecture that allows the array to fold in a range of almost 360°, without...
Article
Full-text available
Multilayer elements are used to miniaturize the size of highly efficient wireless power transfer systems based on the Strongly Coupled Magnetic Resonance (SCMR). Specifically, inspired by miniaturization techniques used in antennas, multilayer resonators in conformal SCMR systems (instead of single-layer resonators traditionally used) are tightly s...
Article
Full-text available
This work aims at the establishment of a rigorous full-wave eigenmode analysis technique based on a finite element scheme for the study of terahertz (THz) or photonic/optical unbounded structures. This numerical tool follows the last decades' trend to migrate the technological knowledge from microwave to THz and photonic regimes. The performed eige...