Engineering Metamaterials

A couple of decades have passed since the advent of electromagnetic metamaterials. Although the research on artificial microwave materials dates back to the middle of the 20th century, the most prominent development in the electromagnetics of artificial media has happened in the new millennium. In the last decade, the electromagnetics of one-, two-, and three-dimensional metamaterials acquired robust characterization and design tools. Novel fabrication techniques have been developed. Many exotic effects involving metamaterials and metasurfaces, which initially belonged in a scientist’s lab, are now well understood by practicing engineers. Therefore, it is the right time for the metamaterial concepts to become a designer’s tools of choice in the landscape of electronics, microwaves, and photonics. Answering such a demand, the book “Engineering Metamaterials” focuses on the theory and applications of electromagnetic metamaterials, metasurfaces, and metamaterial transmission lines as the building blocks of present-day and future electronic, photonic, and microwave devices

Impedance Transformers

Non

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

Passive Planar Microwave Devices

The aim of this book is to highlight some recent advances in microwave planar devices. The development of planar technologies still generates great interest because of their many applications in fields as diverse as wireless communications, medical instrumentation, remote sensing, etc. In this book, particular interest has been focused on an electronically controllable phase shifter, wireless sensing, a multiband textile antenna, a MIMO antenna in microstrip technology, a miniaturized spoof plasmonic antipodal Vivaldi antenna, a dual-band balanced bandpass filter, glide-symmetric structures, a transparent multiband antenna for vehicle communications, a multilayer bandpass filter with high selectivity, microwave planar cutoff probes, and a wideband transition from microstrip to ridge empty substrate integrated waveguide

Wideband Microwave Imaging Systems for the Diagnosis of Fluid Accumulation in the Human Torso

According to the World Health Organization (WHO), cardiovascular diseases (CVDs) are the leading causes of death worldwide, with one third of deaths attributed to CVDs in 2012. Pulmonary oedema and pleural effusion are the most apparent symptoms of many diseases categorized under CVDs such as heart failure and lung cancer, at which fluid (mainly with high water content) is accumulated in or around the lungs. Therefore, constant monitoring of fluid levels inside the lungs is one of the most efficient ways of early detection of CVDs. Chest X-Rays and computational tomography (CT)-scans are the most widely used devices for fluid detection; however, they suffer from lack of sensitivity and ionizing radiation, respectively, that makes them unsuitable for long term monitoring purposes. Currently, magnetic resonance imaging (MRI) is the most reliable device that can be utilized for fluid accumulation detection. However, considering the fact that more than 75% of the CVDs occur in countries with low or middle income, it is not widely available. Moreover, due to their bulky structures, the abovementioned devices lack the capability of being used in mobile emergency units such as ambulances or clinics at rural areas. To that end, this thesis is dedicated to design and fabrication of a low cost, portable and non-invasive device that can be used as an initial decision making tool for medical staff to pursue further investigations to define the exact cause of the oedema. First chapter of the thesis is allocated to introduction of the cardiovascular diseases and their effects on the dielectric properties of the tissues inside the lungs. A complete literature review on various alternative methods for replacing the conventional devices is performed. The obtained results by these systems and their advantages as well as their limitations are discussed. Microwave imaging technique is then presented in chapter two as a robust method which can both provide information about the presence and location of the accumulated fluid. This is specifically of great importance for cases where biopsy is required to remove or take sample of the accumulated fluid for saving the life of the patient. Chapter two is also allocated to the introduction of microwave-based medical diagnostic and monitoring systems for different applications such as breast cancer detection and brain imaging. A prospect of the possible realizable systems is investigated and existing scanning approaches are discussed. The main contributions of the thesis that are the design of several complete platforms, design of novel and unidirectional microwave sensors (antennas), promotion of novel scanning and detection methods are clarified in these chapters. In chapter three, firstly the optimum operating frequency for torso imaging is defined. By applying a circuit model that models different layers of torso as circuit elements, it is shown that a wide operating bandwidth at lower ultra-high frequency (UHF) band provides a reasonable compensation between the resolution of the obtained images and signal penetration inside the body. It is explained that due to the limited allowed microwave power for safety considerations unidirectional antennas are required. Then, it is explained that due to the large wavelengths at lower UHF band the sizes of the prospective antennas are expected to be large. To that end, novel miniaturization techniques are proposed to reduce the sizes of the conventional antennas in chapters three and four. These antennas are categorized under three dimensional (3-D) and planar structure. A folding technique is introduced and used in the proposed 3-D structures and it is shown that by using this technique both size and directivity/back radiation suppression is improved. 3-D slot-antenna and cubic monopole-fed antennas are also proposed that wide operating bandwidth is achieved using slot impedance transformer, and multiple resonance-merging techniques, respectively. Regarding the planar structures that are presented in chapter four, it is shown that by combining the loop-dipole modes, both wide-operating bandwidth and directivity enhancement is achievable. Capacitive-loading of a loop antenna is the other proposed technique in which a loop antenna is partially and/or non-uniformly loaded with capacitors in the forms of simple slots and mu-negative (MNG) metamaterial-unitcells that help miniaturizing the size of the antenna by lowering its first resonance frequency. In chapters five and six, several platforms using single and multiple antennas with linear and circular configurations are presented and the utilized imaging technique for data processing is explained. The platforms are presented in a systematic progressive manner in which each system is covering the limitations of its previous prototype. Two final clinical platforms in the shape of clinical bed and doughnut-shaped chamber are proposed and the obtained test results on artificial phantom, animal lungs and human tests are presented. Based on the obtained results on healthy human beings it is shown that the scattered-field from torso of people with different body sizes vary in a reasonably limited range that is a welcoming result for building a global-database to define a threshold for healthy range. Chapter seven concludes the discussions made throughout the thesis and explains future works that can be carried out to further improve the reported systems

Development of high performance microwaves, millimetres and terahertz antennas based on negative/gradient refractive index, and anisotropic metatronics

In this thesis, Metatronics have been applied to develop high performance antennas. This thesis added five new achievements to the scientific world. Firstly, a volumetric Negative Refractive Index (NRI) medium composed of Split Ring Resonators and Thin Wires (SRRs/TWs) is designed and incorporated with patch antenna operating at 10 GHz and 300 GHz. The gain is improved by 1.5dB. Secondly, a double sided NRI composed of Circular Split Ring Resonators and Thin Wires (CSRRs/TWs) employing a lens is proposed and characterized. The measured gain is improved from 6.5dB to 11.4dB. Thirdly, a new slotted waveguide antenna incorporated with Electrically Split Ring Resonator (ESRR) Metasurface (MTS) exhibiting NRI is proposed. The measured gain of the 10 GHz proposed antenna is improved from 6.7 dB to 10.5 dB. Furthermore, an anisotropic Low Epsilon Medium (LEM) ESRR-MTS is designed to focus the E-plane beam of the slotted antenna. The measured gain is improved by 4dB. Fourthly, high fabrication tolerance non-resonance and resonance GRIN MTS are proposed and characterized up to THz. The gain is improved from 6.7 to 11.3dB for 10 and 60 GHz antennas. Finally, a semi-analytical model based on transfer function is proposed to model THz Photoconductive antenna (PCA) excited by a femtosecond pulsed laser beam

Electrically Small Particles for Energy Harvesting in the Infrared and Microwave Regimes

Harnessing energy from clean and sustainable resources is of crucial importance to our planet. Several attempts through different technologies have been pursued to achieve efficient and sustainable energy production systems. However, having systems with a high energy harvesting efficiency and at the same time low energy production cost are challenging with the existing technologies. In this research, several novel structures based on electrically small particles are proposed for harvesting the microwave and infrared energy efficiently. First, a proof of concept demonstrates a metamaterial unit cell's ability to harness the ambient electromagnetic energy. A split-ring resonator (SRR) representing the metamaterial unit cell is designed at a microwave frequency (5.8 GHz) and then fabricated by using printed circuit board technology to prove this concept. A bow-tie antenna, operating at the above frequency, is also designed to show the power efficiency improvement achieved by utilizing the SRR. More than 37% of power efficiency is achieved using SRRs-based structure compared to the 13% of the bow-tie antenna. A new efficiency term is also proposed to take into account the size reduction and efficiency advancement resulting from SRR structures. To this end, two comparable arrays of SRRs and bow-tie antennas are made. Power efficiency of 63.2% and 15.3% for the SRRs and bow-tie arrays, respectively, are achieved. Another structure composed of an ensemble of electrically small resonators for harvesting microwave energy is presented. A flower-like structure composed of four electrically small SRRs arranged in a cruciate pattern, each with a maximum dimension of less than ʎo/10, is shown to achieve more than 43% microwave-to-alternating current (AC) conversion efficiency at 5.67 GHz. Even- and odd-mode currents are realized in the proposed harvester to improve the efficiency and concurrently reduce the dielectric loss in the substrate. An experimental validation is conducted to prove the harvesting capability. To extend the work to operate at the far-infrared regime, a novel structure based on electrically small resonators is proposed for harvesting the infrared energy and yielding more than 80% harvesting efficiency. The dispersion effects of the dielectric and conductor materials of the resonators are taken into account by applying the Drude model. A new scheme to channel the infrared waves from an array of SRRs is proposed, whereby a wide-bandwidth collector is utilized by employing this new channeling concept. With the same pattern of the flower-like harvester operating in microwave regime, a new structure composed of electrically small SRRs, each of whose greatest length is less than ʎo/21, is proven to achieve more than 85% of power harvesting efficiency at 0.348 THz. Furthermore, the infrared energy harvesters are fabricated using nano-fabrication tools. At last, the infrared harvesters are experimentally validated with the numerical findings using THz time-domain spectroscopy (THz-TDS).1 yea