Advances in Antenna Engineering and Wireless Systems Research

It is a major duty of researchers to keep up with the advances in engineering and technology that occur almost daily. United Scholars Publications has recognized this duty and designed a book series that provide scientists, engineers, educators, and researches in this vital field with the cutting edge developments and to disseminate it globally. This book, organized into eight chapters, features scientists from around the globe contributing diverse topics in mostly antenna theory and engineering. The book aims at highlighting the state of the art research and recent findings in new technologies and designs, and bridging theoretical research with applications. This collection will be of significant value to academic researchers, graduate students as well as practicing engineers working in this vibrant field. Chapter One presents an optimized design procedure of a slot-coupled cylindrical dielectric resonator antenna. The technique exploits an equivalent circuit of the resonating antenna to significantly reduce the number of full-wave EM simulations. The target values of the equivalent circuit elements are determined from the desired specifications such as bandwidth, center frequency and in-band return loss level. Chapter Two proposes novel broadband single-layered microstrip elements for dual-polarized reflectarray. The structure of the proposed elements has four-axial symmetry in the unit cell, which can achieve low cross-polarization property. These elements can lead to a linear phase curves with almost the same slop characteristics for the frequency, thereby achieving the desirable reflection phase over the wide frequency range. Chapter Three presents an optimization study of a patch-fed dielectric rod antenna design at millimeter wave band. The proposed design is composed of simple dielectric rod antenna made of low cost Teflon with relative permittivity of 2.1 that is fed by a rectangular patch antenna. Compared to the conventionally used tapered dielectric rod antennas, this configuration is capable of producing higher gain for a given antenna length. Chapter Four presents a new type of mobile handset PIFA antenna design to reduce the specific absorption rate (SAR) in human head. PIFA antenna structures operating at 1.8 GHz are considered. Current density in human head is decreased by reducing the near electric field radiation coming from the radiating antenna to the human head, which in turns leads to a reduction in SAR. This SAR reduction is accomplished by inserting several edges at each corner in the ground plane. Chapter Five examines genetic algorithm optimizer in antenna design. Specifically, the authors design and optimize the Yagi-Uda using Genetic Algorithm (GA) optimizer for digital terrestrial television (DTT) reception. The results show enhanced antenna performance as compared to current conventional antennas available in the market. Chapter Six investigates the effects of uncut and cut single rectangular spiral metamaterial unit cells on the performance of a microstrip antenna. Chapter Seven demonstrates a variety of Defected Ground Structure (DGS) to suppress cross-polarization in H-plane for rectangular and circular patch. It also shows the importance of DGS in impedance bandwidth broadening. Furthermore, the DGS used for suppression in cross-polarization, improves the co- polar radiation in the E-plane for the same antenna. Hence, the proposed DGS can be used for both purposes and can be applied to array elements. Thus, the functional properties showed significant enhancement with the application DGS. Chapter Eight analyzes Orthogonal Frequency Division Multiplexing (OFDM) system and the effect of varying the cyclic prefix length on OFDM System over different channel models. The simulations were carried out over Additive White Gaussian Noise (AWGN), Rayleigh fading channels, standard wireless channel models, and the results have been compared with the theoretical ones.