Metamaterial inspired radar absorbers: Emergence, trends and challenges

The advances in metamaterial science and technology have raised the expectations of camouflage or stealth researchers to one order higher in terms of absorption characteristics. As metamaterial inspired radar absorbing structures are proving themselves as a good candidate with near unity absorption, feasibility towards hardware realization is necessary. Hence an extensive literature survey of metamaterial inspired radar absorbing structure has been carried out and reported in this paper along with the challenges and material issues. The various types of metamaterial structures that can be used as absorber have been provided along with simulation figures. To make the review more useful, graphene and carbon nanotube (CNT) based radar absorbing structures are also included along with their simulation and fabrication techniques

A Review of Metamaterial Invisibility Cloaks

The exciting features of metamaterial in conjunction with transformation optics leads to various applications in the microwave regime with such examples as invisible cloak, frequency selective surfaces (FSS), radomes, etc. The concept of electromagnetic invisibility is very much important in aerospace platform. Hence to study the feasibility of implementation of this concept for stealth, an extensive literature survey of metamaterial cloaks has been carried out and reported in this paper along with the basic concept of cloaking. To make the review more effective, the technical papers are classified into three broad sections viz. mathematical modeling, design and simulations, and fabrications and experimental demonstration. Further the design and simulation is focused on different techniques implemented such as finite difference time domain (FDTD), finite element method (FEM), finite integration technique (FIT), inductor-capacitor representation of metamaterial (LC MTM) etc. The review also reports the methods implemented for analysis of metamaterial cloaks with possibility of application to the specific frequency rang

Bacteria Foraging Algorithm for Metamaterial Design and Optimization

Soft computing techniques are emerging as highly efficient global optimization techniques in the field of electromagnetics. These techniques along with the EM software have proved their efficiency in antenna engineering, wireless communication, absorber design and a few in the field of metamaterial structural analysis. Bacteria foraging algorithm, although has been used recently in controls, is still new to the field of metamaterial science and technology. In this paper, bacteria foraging algorithm (BFA) is used for design optimization of a double ring circular split ring resonator. Equivalent circuit analysis is used the EM tool for analysis of the CSRR. The aim of bacteria foraging algorithm is the estimation of structural parameters of the CSRR at a desired frequency range. Further the developed algorithm is proved through extraction of parameters of the optimized metamaterial structure. A comparative study with other soft computing techniques w.r.t. accuracy and computational time is provided

Implementation of Refined Ray Tracing inside a Space Module

Modern space modules are susceptible to EM radiation from both external and internal sources within the space module. Since the EM waves for various operations are frequently in the high-frequency domain, asymptotic raytheoretic methods are often the most optimal choice for deterministic EM field analysis. In this work, surface modeling of a typical manned space module is done by hybridizing a finite segment of right circular cylinder and a general paraboloid of revolution (GPOR) frustum. A transmitting source is placed inside the space module and test rays are launched from the transmitter. The rays are allowed to propagate inside the cavity. Unlike the available ray-tracing package, that use numerical search methods, a quasi-analytical ray-propagation model is developed to obtain the ray-path details inside the cavity which involves the ray-launching, ray-bunching, and an adaptive cube for ray-reception

Bacteria Foraging Optimization in Antenna Engineering: An Application to Array Fault Finding

Finding fault elements in linear antenna arrays using bacteria foraging optimization (BFO) is presented. One of the better options of array diagnosis is to perform it by measuring the radiated field, because in this case, removal of the array from its working site is not required and thereby not interrupting its normal operation. This task of fault finding from far-field data is designed as an optimization problem where the difference between the far-field power pattern obtained for a given configuration of failed element(s) and the measured one is minimized w. r. t. the excitations of the array elements. This set of excitations on comparison with the excitations of the original array gives the idea of the fault position and their type, such as either complete fault or partial fault. BFO being relatively new to microwave community when compared with other soft-computing techniques, its performance was observed w. r. t. time of computation and convergence of the iterative process. Possibility of finding the faults from random sample points and use of minimum number of sample points for array fault finding are the novelties of the present work

Soft Computing Techniques for Mutual Coupling Reduction in Metamaterial Antenna Array

Application of soft computing techniques for various metamaterial designs and optimizations is an emerging field in the microwave regime. In this paper, a global optimization technique, namely, particle swarm optimization (PSO), is used for the design and optimization of a square split ring resonator (SSRR) having a resonant frequency of 2.4GHz.The PSO optimizer yields the structural parameters, which is further simulated and validated with the optimized value. This optimized structure results in the mutual coupling reduction in a microstrip antenna array designed for wireless application

Metamaterial inspired electromagnetic applications: role of intelligent systems

This book focuses on the role of soft-computing-based electromagnetic computational engines in design and optimization of a wide range of electromagnetic applications. In addition to the theoretical background of metamaterials and soft-computing techniques, the book discusses novel electromagnetic applications such as tensor analysis for invisibility cloaking, metamaterial structures for cloaking applications, broadband radar absorbers, and antennas. The book will prove to be a valuable resource for academics and professionals, as well as military researchers working in the area of metamaterials

Adaptive Tuning in Terahertz Metamaterials using Swarm Intelligence

Terahertz imaging is growing at the rapid pace and finds application in fields such as astronomy, material characterization, tumor detection, security and detection of concealed items, etc. Advances in this wide range of applications are hindered by the lack of natural dielectrics in the terahertz range of frequencies. This challenge is combated by the usage of artificially engineered material called metamaterial – electromagnetic structures obtained by patterning metal on a dielectric. Metamaterial based absorbers are used to improve the performance of detectors in terahertz imaging. These EM structures are often resonant and their application is restricted to narrow bands. However, the applications in terahertz require reception of signals over wide band of frequencies. This issue can be sorted out by designing active metamaterials whose resonant frequency can be tuned. Mathematical formulation for the design of metamaterial based absorbers is cumbersome. While equations for the design of the metamaterial itself may be found, the presence of additional dielectrics in the construction of absorbers shift the resonant frequency. This brings about the need for the use of computational optimization tools in order to arrive at the best structural parameters. In addition, the lack of mathematical formulation necessitates the integration of these optimization tools with EM simulators in order to achieve optimization through iterative simulations. In this paper, a swarm intelligence based algorithm viz. particle swarm optimization (PSO) is used to develop a computational engine for the design of an active terahertz metamaterial absorber. The computational engine arrives at the optimum solution by simulating designs in a commercially available EM simulator. In this paper, a circular split ring resonator (CSRR) is used as the metamaterial unit cell for the absorber whose structural parameters are obtained using the PSO. It has been observed that the resonant frequency of the absorber can be varied by rotating the inner ring of each CSRR. Further, the developed swarm intelligence based computational engine is used to find the optimum rotation angles of the inner rings of each CSRR for a range of frequencies. Therefore, a database of rotation angles for a range of frequencies is obtained. This database can be used for the rapid, adaptive tuning of the absorber array in practical applications

RF Field Build-up inside a Manned Space Vehicle using Novel Ray-Tracing Algorithm

The radio-frequency (RF) field mapping and its analysis inside a space vehicle cabin, although of immense importance, represents a complex problem due to its inherent concavity. Further hybrid surface modeling required for such concave enclosures leads to ray proliferation, thereby making the problem computationally intractable. In this paper, space vehicle is modeled as a double-curvatured general paraboloid of revolution (GPOR) frustum, whose aft section is matched to an end-capped right circular cylinder. A 3D ray tracing package is developed that involves an uniform ray launching scheme, an intelligent scheme for ray bunching and an adaptive reception algorithm for obtaining ray path details inside the concave space vehicle. Due to non-availability of image method for concave curvatured surfaces, the proposed ray-tracing method is validated w.r.t. the RF field build-up inside a closed lossy cuboid using image method. The RF field build-up within the space vehicle is determined using the details of ray-paths and the material parameters. The results for RF field build-up inside a metal-backed dielectric space vehicle are compared with that of highly metallic one for parallel and perpendicular polarizations. The convergence of RF field within the vehicle is analyzed w.r.t. the propagation time and the number of bounces a ray undergoes before reaching the receiving point

Spatially Uniform Ray Launching from an Isotropic Source Inside a Rectangular Cavity: Software User Manual

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