Approximate electromagnetic cloaking of a conducting cylinder using homogeneous isotropic multi-layered materials

AbstractCloaking refers to hiding a body from detection by surrounding it with a coating consisting of an unusual anisotropic nonhomogeneous material. Its function is to deflect the rays that would have struck the object, guide them around the object, and return them to their original trajectory, thus no waves are scattered from the body. The permittivity and permeability of such a cloak are determined by the coordinate transformation of compressing a hidden body into a point or a line. Some components of the electrical parameters of the cloaking material (ɛ, μ) are required to have infinite or zero value at the boundary of the hidden object. Approximate cloaking can be achieved by transforming the cylindrical body (dielectric and conducting) virtually into a small cylinder rather than a line, which eliminates the zero or infinite values of the electrical parameters. The radially-dependent cylindrical cloaking shell can be approximately discretized into many homogeneous anisotropic layers; each anisotropic layer can be replaced by a pair of equivalent isotropic sub-layers, where the effective medium approximation is used to find the parameters of these two equivalent sub-layers. In this work, the scattering properties of cloaked perfectly conducting cylinder is investigated using a combination of approximate cloaking, together with discretizing the cloaking material using pairs of homogeneous isotropic sub-layers. The solution is obtained by rigorously solving Maxwell equations using angular harmonics expansion. The scattering pattern, and the back scattering cross section against the frequency are studied for both transverse magnetic (TMz) and transverse electric (TEz) polarizations of the incident plane wave for different transformed body radii

Cluster-Based Multi-User Multi-Server Caching Mechanism in Beyond 5G/6G MEC

The work on perfecting the rapid proliferation of wireless technologies resulted in the development of wireless modeling standards, protocols, and control of wireless manipulators. Several mobile communication technology applications in different fields are dramatically revolutionized to deliver more value at less cost. Multiple-access Edge Computing (MEC) offers excellent advantages for Beyond 5G (B5G) and Sixth-Generation (6G) networks, reducing latency and bandwidth usage while increasing the capability of the edge to deliver multiple services to end users in real time. We propose a Cluster-based Multi-User Multi-Server (CMUMS) caching algorithm to optimize the MEC content caching mechanism and control the distribution of high-popular tasks. As part of our work, we address the problem of integer optimization of the content that will be cached and the list of hosting servers. Therefore, a higher direct hit rate will be achieved, a lower indirect hit rate will be achieved, and the overall time delay will be reduced. As a result of the implementation of this system model, maximum utilization of resources and development of a completely new level of services and innovative approaches will be possible

A multiple‐input‐multiple‐output on‐chip Quasi‐Yagi‐Uda antenna for multigigabit communications: Preliminary study

This article presents a solution for the low gain and the poor efficiency of the on‐chip antennas (OCA). The four elements of Quasi‐Yagi‐Uda antennas (QYUA) are introduced based on the diversity technique to reduce the interference between the elements. In addition, these antennas achieve high isolations between them due to the use of reflector for each antenna. The QYUA is selected to improve the radiation properties of the end‐fire radiator in the millimeter‐wave range for on‐chip systems. The proposed MIMO antenna is used for the point to point communications. The complementary metal‐oxide semiconductor with 180 nm standard is used in the antenna design with six metal layers. The QYUA combines three parts (driven element, reflector, and director); the driven consists of two meander lines fed by coplanar‐slot and operates as a dipole, the reflector is an arc likes a semicircle to prevent the back radiation and increase the front to back ratio, and the director is a meander line to directive the radiation into the proposed direction (front end‐fire direction). All MIMO parameters such as envelope correlation coefficient, channel capacity loss, diversity gain, and total active reflection coefficient in addition to the different configurations of the MIMO are presented. All results are verified by computer simulation technology and high‐frequency structure simulator. The contribution of this article is the MIMO antenna design for point to point communications to serve multigiga communications systems with high data rate and high gain. This MIMO system is considered here to solve the problems of OCA designs

MOM/GA-based virtual array for radar systems

This paper introduces a novel antenna array synthesis for radar systems based on the concept of a virtual antenna array (VAA) and the method of moments/genetic algorithm (MoM/GA) synthesis method. The VAA concept is applied to both scanning and fixed radiation pattern arrays. The proposed VAA is introduced to simultaneously support the medium-range radar (MRR) and the long-range radar (LRR) with beam width ±7° for LRR and ±37° for MRR. The proposed VAA is distinguished by its minimum number of antenna elements, simple feeding network, high efficiency, and gain, but all of these are at the expense of a large aperture antenna size compared to the planar antenna array (PAA). The VAA has the ability to have the feeding network and the radiating elements on the same layer, as compared to the multilayer PAA. The newly proposed concept is analyzed and verified analytically and experimentally. Two orthogonal (16 elements) VAAs are designed to operate in the frequency range from 23.55 to 24.7 GHz and to support a flat-shoulder shape (FSS) radiation pattern for LRR/MRR. The antenna was fabricated and tested experimentally, and good agreements between the simulated and measured results were noticed. The proposed VAA is introduced to solve the problems of large size, low isolations, low efficiency, feeding network, low resolution, and small coverage range for the antenna arrays of automotive radars. The proposed antenna array is introduced for automotive radar applications at 24 GHz