Design and realization for radar cross section reduction of patch antennas using shorted stubs metamaterial absorbers

This thesis is devoted to analyzing of the Radar Cross Section (RCS) of rectangular patch antenna using Metamaterial Absorber (MMA) and the analysis of its reducing techniques. The addressed theme has a great complexity and it covers various areas that include designing and optimization of target geometrical model of rectangular patch antenna structures and making it compatible with respect to metamaterial geometry. Analyses have been made to optimize and validate the structure performances that include numerical methods for electromagnetic field computation, MMA behavior, characterization, extraction of parameters, antenna radiation performance analyses, simulation, fabrication, testing, and optimization with back validating the designs. The MMA structure finds its applications in antenna designing for the reduction of Monostatic and Bistatic RCS in stealth platform for lower detectable objects. However, there is still more emphasis needed to devote for in-band frequency response for low RCS of the antenna. Therefore, making these assumptions, we have been proposing novel designs of single-band, dual-band, and triple-band MMA structures. These structures provide significant scattering characteristics and offering flexibility to the designer to control and tune the resonant frequency, based on the specific applications as compared to that of the other MMAs in the microwave regime of the Electromagnetic (EM) spectrum. To explore the research scope, a three dimensional Frequency Selective Surface (FSS) structure has been analyzed and its simulation responses with respect to parametric analyses have been made. The research investigation further extended to Electronic Band Gap (EBG) Structure and Defected Ground Structure (DGS). A hybrid structure of patch antenna is proposed and designed for an inset feed rectangular microstrip patch antenna operating at 2.45 GHz in the Industrial, Scientific, and Medical (ISM) band. This hybrid structure claims the size reduction, bandwidth, and gains enhancement. The main focus of this research work is limited to determine the potential and practical feasibility of MMA’s to enhance the stealth performance of rectangular patch antennas. For this purpose, Monostatic and Bistatic RCS simulation and measurements are carried out in an anechoic chamber and practical methods for Radar Cross Section reduction are discussed and analyzed

COMPARATIVE ANALYSES FOR RCS OF 10 GHz PATCH ANTENNA USING SHORTED STUBS METAMATERIAL ABSORBER

In this research work, a novel approach for the in-band reduction of Radar Cross Section (RCS) of rectangular patch antenna has been proposed. An ultrathin Metamaterial Absorber (MMA) consists of shorted stubs and rectangular bars has been loaded around the patch antenna. The referenced patch antenna and MMA are designed at the same central frequency of 10 GHz corresponds to X-band. Three different MMA loaded rectangular patch antenna designs are proposed and their behaviours are simulated, analysed and measured. Compared with the conventional patch antenna, the analysis shows that lower RCS values achieved as the number of MMA layers increase around the existing source. At 10 GHz, the maximum monostatic RCS reduction of 9.61 dBsm, 22.67 dBsm and 23.68 dBsm have been achieved for Design 1, Design 2 and Design 3 respectively. While the antenna characteristics and radiation performances almost remain unaffected and preserved

Disseny i mesura de teixits apantallants / antiradiació electromagnètica per a protecció

In recent years several studies regarding metamaterials have been carried out. The possibility of reaching new properties further from the ones offered by conventional materials has opened new ways of study. Among the different fields of investigation in which metamaterials and frequency selective surfaces are involved, applying them on fabrics and creating wearable structures is one of the newest, and still few investigation has been done on it since, although its potential applications, it is still difficult to reach good results. For this reason, and in order to prove that this is an important field in which very interesting results can be obtained by means of conventional procedures, in this thesis a FSS based on fabric and conductive thread is designed. To do so, the first step is to optimize the geometry using computer simulations until reaching the desired electromagnetic properties. Once done that, the designed unit cell is applied in a larger surface, which is tested and the obtained results compared to the ones given by the simulation. By doing this, it is proved that, although the final crafted surface is not exactly the same that the designed one because of the imperfections inherent in any construction process the properties reached are almost the same, offering similar levels of absorption and a small shift of frequency. Since the surface tested in this thesis is relatively small, testing bigger surfaces in order to better approximate the infinite extension hypothesis and improve the construction process are the logical steps to follow in order to improve a technology which has already been proved to be useful, possible and within reach

Wide Band Embedded Slot Antennas for Biomedical, Harsh Environment, and Rescue Applications

For many designers, embedded antenna design is a very challenging task when designing embedded systems. Designing Antennas to given set of specifications is typically tailored to efficiently radiate the energy to free space with a certain radiation pattern and operating frequency range, but its design becomes even harder when embedded in multi-layer environment, being conformal to a surface, or matched to a wide range of loads (environments). In an effort to clarify the design process, we took a closer look at the key considerations for designing an embedded antenna. The design could be geared towards wireless/mobile platforms, wearable antennas, or body area network. Our group at UT has been involved in developing portable and embedded systems for multi-band operation for cell phones or laptops. The design of these antennas addressed single band/narrowband to multiband/wideband operation and provided over 7 bands within the cellular bands (850 MHz to 2 GHz). Typically the challenge is: many applications require ultra wide band operation, or operate at low frequency. Low frequency operation is very challenging if size is a constraint, and there is a need for demonstrating positive antenna gain

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Advanced Radio Frequency Antennas for Modern Communication and Medical Systems

The main objective of this book is to present novel radio frequency (RF) antennas for 5G, IOT, and medical applications. The book is divided into four sections that present the main topics of radio frequency antennas. The rapid growth in development of cellular wireless communication systems over the last twenty years has resulted in most of world population owning smartphones, smart watches, I-pads, and other RF communication devices. Efficient compact wideband antennas are crucial in RF communication devices. This book presents information on planar antennas, cavity antennas, Vivaldi antennas, phased arrays, MIMO antennas, beamforming phased array reconfigurable Pabry-Perot cavity antennas, and time modulated linear array

Polarizable Particles and their Two-Dimensional Arrays: Advances in Small Antenna and Metasurface Technologies.

Metamaterials are subwavelength-structured materials designed to exhibit tailored electromagnetic properties. Metamaterials have allowed extreme control over constituent material parameters (i.e. permittivity, permeability, and chirality), which has enabled a myriad of counterintuitive physical phenomena. However, metamaterials typically suffer from high losses, difficulties in fabrication, and are bulky. This has led to the development of metasurfaces, which are the two dimensional equivalent of metamaterials. Metasurfaces can impart abrupt discontinuities on electromagnetic wavefronts, allowing electromagnetic fields to be tailored across subwavelength length scales. The building blocks of metasurfaces are subwavelength textured, polarizable particles. Near resonance, these particles support strong currents, which makes them excellent small antennas. In this thesis, a circuit model is developed that can model an arbitrary small antenna based on its frequency dependent polarizability. In addition, a direct transfer patterning process is developed that allows metallic patterns to be printed onto arbitrarily contoured substrates. This work will find immediate applications in a number of emerging technologies resulting from the rapid expansion of the mobile electronics industry. Next, extreme control of the polarization and profile of a wavefront is demonstrated using two-dimensional arrays of polarizable particles (i.e. metasurfaces). A new class of metasurfaces, referred to as metamaterial Huygens' surfaces, is shown to have a significantly improved efficiency over the state of the art. Metamaterial Huygens' surfaces utilize polarizable particles that exhibit both an electric and magnetic response, which allows for reflectionless wavefront control. Next, it is shown that simply cascading patterned metallic sheets can also provide high transmission and complete phase control. To demonstrate the design methodology, several different metasurfaces are developed that deflect incident Gaussian beams to a stipulated angle or convert an incident Gaussian beam into a vector Bessel beam. Further, utilizing sheets with anisotropic patterns provides additional magneto-electric coupling, which enables complete control of a wavefront (i.e. amplitude, phase, and polarization control). The experimental verification at frequencies ranging from microwaves to optics highlights the versatility of this work.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111395/1/carlpfei_1.pd

The First Multichroic Receiver and Results from ACTPol.

The Cosmic Microwave Background (CMB) is a unique and powerful tool for the study of cosmology and fundamental physics. The next frontier of CMB research is to extract the wealth of cosmological information available from its polarization. Accurate measurement of this polarization signal will enable us to probe inflation, provide an alternative means to measure the neutrino mass sum and number of neutrino species; improve our understanding of dark energy; explore the reionization history of our Universe; probe the large scale structure through gravitational lensing; and enable a multitude of other astrophysical studies. The polarized signatures of the early universe are extremely weak, dominated by foregrounds, and its measurement is susceptible to instrumental effects. Extracting the information contained in these faint signals requires instruments with high sensitivity, excellent control over systematic errors, and careful data analysis. The Atacama Cosmology Telescope Polarimeter (ACTPol) is a state-of-the-art experiment that measures CMB polarization over finer angular scales from the Atacama desert in Chile. In this thesis, I present an overview of this project and then describe my work on the project including development of a new polarization sensitive dichroic camera for ACTPol designed to increase the sensitivity of CMB telescopes and enable high precision measurements of CMB polarization; the development of novel metamaterial antireflection coatings for silicon lenses; diffraction from panel gaps; calibration of detector pass-bands; and a detailed description of my analysis of the polarization properties of extragalactic point sources discovered with the ACTPol data. I conclude with a discussion of the science of ACTPol, and the impact of my technical work on future CMB experiments.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135767/1/dattar_1.pd

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance