人体内外間のマイクロ波伝搬に関する研究

Tohoku University陳強課

Near field interactions in terahertz metamaterials

Terahertz (THz) frequencies comprise the portion of the electromagnetic spectrum more energetic than microwaves, but less energetic than infrared light. The THz band presents many opportunities for condensed matter physics and optics engineering. From the physics perspective, advances in the generation and detection of THz radiation have opened the door for spectroscopic studies of a range of solid-state phenomena that manifest at THz frequencies. From an engineering perspective, THz frequencies are an under-used spectral region, ripe for the development of new devices. In both cases, the challenge for researchers is to overcome a lack of sources, detectors, and optics for THz light, termed the THz Gap. Metamaterials (MMs), composite structures with engineered index of refraction, n, and impedance, Z, provide one path towards realizing THz optics. MMs are an ideal platform for the design of local EM field distributions, and far-field optical properties. This is especially true at THz frequencies, where fabrication of inclusions is easily accomplished with photolithography. Historically, MM designs have been based around static configurations of resonant inclusions that work only in a narrow frequency band, limiting applications. Broadband and tunable MMs are needed to overcome this limit. This dissertation focuses on creating tunable and controllable MM structures through the manipulation of electromagnetic interactions between MM inclusions. We introduce three novel MM systems. Each system is studied computationally with CST-Studio, and experimentally via THz spectroscopy. First, we look at the tunable transmission spectrum of two coupled split ring resonators (SRRs) with different resonant frequencies. We show that introducing a lateral displacement between the two component resonators lowers the electromagnetic coupling between the SRRs, activating a new resonance. Second, we study an SRR array, coupled to a non-resonant closed ring array. We show that lowering the interaction strength through lateral displacement changes the MM oscillator strength by ~ 40% and electric field enhancement by a factor of 4. Finally, we show that interactions between a superconducting SRR array and a conducting ground plane result in a temperature and field strength dependent MM absorption. The peak absorption changes by ~ 40% with increasing electric field and by ~ 66% with increasing temperature

Préparation, caractérisation et application du fluide flexible dans l'antenne composite

Innovation is generally the main driver of most technological developments. This work deals with a typical example in the communication sector, through the development of some flexible composite-based antennas. The efficiency of ordinary fluidic antenna was increased by using ionic liquid assembled with nano metals composites. They possess unique advantages like their conductivity, flexibility, non-toxicity and profitability. Moreover, they are highly efficient with a radio wave frequency of 2GH applicable in the underground mining sector. An ideal solution is to realise the EM components on flexible/stretchable materials encapsulation using a micro in polydimethylsiloxane (PDMS) substrates. This thesis contains various innovative and creative aspects divided into different sections. Chapter one gives the general introducation and the literature review Chapter two explores the fabrication, characterization, and applications of polydimethylsiloxane and bentonite clay nanocomposites impregnated with silver, copper, and graphene nanoparticles for the fabrication of a stretchable and robust micro-strip antenna. The nanocomposites’ physical, mechanical, and thermal properties were evaluated based on their respective reinforcements’ proportions. The applied techniques included the tensile and flexural tests for the mechanical characterization as well as the rheological and the thermogravimetric analysis. In addition, the surface morphology was evaluated by different techniques such as the X-ray diffraction, the scanning and transmission electron microscopy, and the UV-Vis spectroscopy. Moreover, the conductivity was characterized by electrochemical impedance spectroscopy, the dynamic viscosity analysis, and the ion coupled plasma measurements. The fabricated nanocomposites were shown to be excellent candidates for microstrip antenna applications due to both their electrical conductivity and their mechanical flexibility. These findings pave the way for the fabrication of flexible RF devices for advanced applications in the military, sensor, and space industries. Chapter three deals with Fabricated Wearable and Flexible Chip made of Gallium and Silver Metals composites assembled on Graphene inside a PDMS Matrix. Chapter four deals with the topic entitled "Perparation and evaluation of Conductive polymeric composites from Metal and Alloys and Graphene to be future flexible Antenna Device”. Chapter five presents the Studying and Evaluting The Physical characteristics of the Composite Substrate Chip and its Applications Chapter six presents the topic entitled “Preparation and Estimation of the physical characterization of Nanofluidic Solution and its application". Chapter Seven discusses the topic entitled “Specific Integrated Imidazole Solution Incorporating with Metallic Copper-Silver alloys in Nanoscales assembled on Graphene to be applicable FOR Future Antenna Devices "

Novel Flexible Wearable Antennas Based on Advanced Materials and Fabrication Techniques.

PhD Theses.Wearable technology has evolved gradually in parallel with other technological advancements, and nowadays, it plays a key role in a wide range of applications. New antenna designs within wearable environments should explore solutions using exible materials, remaining ergonomic and comfortable but o ering mechanical robustness at the same time. Among these materials, carbon-based materials are up-and-coming candidates for these types of solutions and fabrics to fully integrate into e-textiles and smart clothing. The target of this research is to develop novel designs for exible antennas that will provide solutions to overcome the challenges associated with wearable technology by using modern fabrication techniques and materials. A comprehensive literature review regarding fabrication methods, together with material characterisation techniques is presented. A lack of experimental work was noticed, and for the rst time, a full campaign of measurements was carried out to accurately describe the temperature's impact on fabric-based devices using resonator antenna structures. Wearables in general and e-textiles, in particular, are about to tackle tremendous environmental and sustainability challenges. In the context of exploring sustainable materials in e-textiles, a novel soft and conformal textile-based antenna using multi-layer graphene sheets has been thoroughly analysed, describing its performance, the e ects of bending, and proximity to the human body. Within this research, printing techniques have been considered as an alternative to assembly processes. Two antenna designs (PICA/LOOP) with the advantages of carbon nanotubes inks and screen-printing methods, such as lightness, malleable and washability are characterized. In addition, a quasi-Yagi-Uda design has been optimized, fabricated, and characterised. The specimen was inkjet printed on Kapton substrate using graphene ink. A post-numerical analysis was used to characterise the e ect of a not ideal fabrication. The measured data was post-processed in order to overcome some of the associated challenges of measurements for exible devices in a wearable environment. The outcomes of this research ful l the gap between the use of carbon-based alternatives and fabrication procedures on di erent exible substrate

Solid State Technology Branch of NASA Lewis Research Center Second Annual Digest, June 1989 - June 1990

A collection of papers and presentations authored by the branch between June 1989 and June 1990 is presented. The papers are organized into four sections. Section 1 deals with research in microwave circuits and includes full integrated circuits, the demonstration of optical/RF interfaces, and the evaluation of some hybrid circuitry. Section 2 indicates developments in coplanar waveguides and their use in breadboard circuits. Section 3 addresses high temperature superconductivity and includes: thin film deposition, transport measurement of film characteristics, RF surface resistant measurements, substrate permittivity measurements, measurements of microstrip line characteristics at cryogenic temperatures, patterning of superconducting films, and evaluation of simple passive microstrip circuitry based on YBaCuO films. Section 4 deals with carbon films, silicon carbide, GaAs/AlGaAs, HgCdTe, and other materials

The left hand of electromagnetism : metamaterials

Ankara : The Department of Physics and the Institute of Engineering and Science of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 160-172.Metamaterials are artificial periodic structures whose electromagnetic response is solely dependent on the constituting unit cells. In the present thesis, we studied unit cell characteristics of metamaterials that has negative permeability and permittivity. We investigated negative permeability medium elements, especially in terms of their electrical size and resonance strength. Experimental and numerical study of µ-negative (MNG) materials: multi split ring resonators (MSRRs), spiral resonators (SRs) and multi-spiral resonators are presented. The resonance frequency of the structures is determined by the transmission measurements and minimum electrical size of λ0/17 for the MSRRs and of λ0/82 for the SRs observed. We explain a method for tuning the resonance frequency of the multi-split structures. We investigated scalability of MNG materials and designed a low loss double negative composite metamaterial that operates at the millimeter wave regime. A negative pass-band with a peak transmission value of -2.7 dB was obtained experimentally at 100 GHz. We performed transmission based qualitative effective medium theory analysis numerically and experimentally, in order to prove the double negative nature of the metamaterial. These results were supported by the standard retrieval analysis method. We confirmed that the effective index of the metamaterial was indeed negative by performing far field angular scanning measurements for a metamaterial prism. Moreover, we illuminated the split-ring resonator based metamaterial flat lens with oblique incidence and observed from the scanning experiments, the shifting of the beam to the negative side. The first device was a horn antenna and metamaterial lens composite whose behavior was similar to Yagi-Uda antenna. We numerically and experimentally investigated planar fishnet metamaterials operating at around 20 GHz and 100 GHz and demonstrated that their effective index is negative. The study is extended to include the response of the metamaterial layer when the metamaterial plane normal and the propagation vector are not parallel. We also experimentally studied the transmission response of a one dimensional rectangle prism shaped metamaterial slab for oblique incidence angles and confirmed the insensitivity of split-ring resonator based metamaterials to the angle of incidence. After the demonstration of complete transmission enhancement by using deep subwavelength resonators into periodically arranged subwavelength apertures, we designed and implemented a metamaterial with controllable bandwidth. The metamaterial based devices can be listed under the categories of antennas absorbers and transmission enhancement. We studied electrically small resonant antennas composed of split ring resonators (SRR) and monopoles. The electrical size, gain and efficiency of the antenna were λ0/10, 2.38 and 43.6%, respectively. When we increased the number of SRRs in one dimension, we observed beam steerability property. These achievements provide a way to create rather small steerable resonant antennas. We also demonstrated an electrically small antenna that operates at two modes for two perpendicular polarizations. The antenna was single fed and composed of perpendicularly placed metamaterial elements and a monopole. One of the metamaterial elements was a multi split ring resonator and the other one was a split ring resonator. When the antenna operates for the MSRR mode at 4.72 GHz for one polarization, it simultaneously operates for the SRR mode at 5.76 GHz, but for the perpendicular polarization. The efficiencies of the modes were 15% and 40% with electrical sizes of λ/11.2 and λ/9.5. Finally, we experimentally verified a miniaturization method of circular patch antennas. By loading the space between the patch and ground plane with metamaterial media composed of multi-split ring resonators and spiral resonators, we manufactured two electrically small patch antennas of electrical sizes λ/3.69 and λ/8.26. The antenna efficiency was 40% for the first mode of the multi-split ring resonator antenna with broad far field radiation patterns similar to regular patch antennas. We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of i) a metal back plate and an artificial magnetic material layer; ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a λ/4.7 thick absorber of type i), with a 99.8% absorption peak along with a 8% fractional bandwidth. We have also demonstrated experimentally a λ/4.7 and a λ/4.2 thick absorbers of type ii), based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. We conveyed these concepts to optical frequencies and demonstrated a metamaterial inspired absorber for solar cell applications. We finalized the study by a detailed study of split ring resonators at the infrared and visible band. We studied i) frequency tuning, ii) effect of resonator density, iii) shifting magnetic resonance frequency by changing the resonator shape, iv) effect of metal loss and plasma frequency and designed a configuration for transmission enhancement at the optical regime. By using subwavelength optical split ring resonator antennas and couplers we achieved a 400-fold enhanced transmission from a subwavelength aperture area of the electrical size λ2 /25. The power was transmitted to the far field with 3.9 dBi directivity at 300 THz.Alıcı, Kamil BoratayPh.D

Compact and Efficient Millimetre-Wave Circuits for Wideband Applications

Radio systems, along with the ever increasing processing power provided by computer technology, have altered many aspects of our society over the last century. Various gadgets and integrated electronics are found everywhere nowadays; many of these were science-fiction only a few decades ago. Most apparent is perhaps your ``smart phone'', possibly kept within arm's reach wherever you go, that provides various services, news updates, and social networking via wireless communications systems. The frameworks of the fifth generation wireless system is currently being developed worldwide. Inclusion of millimetre-wave technology promise high-speed piconets, wireless back-haul on pencil-beam links, and further functionality such as high-resolution radar imaging. This thesis addresses the challenge to provide signals at carrier frequencies in the millimetre-wave spectrum, and compact integrated transmitter front-ends of sub-wavelength dimensions. A radio frequency pulse generator, i.e. a ``wavelet genarator'', circuit is implemented using diodes and transistors in III--V compound semiconductor technology. This simple but energy-efficient front-end circuit can be controlled on the time-scale of picoseconds. Transmission of wireless data is thereby achieved at high symbol-rates and low power consumption per bit. A compact antenna is integrated with the transmitter circuit, without any intermediate transmission line. The result is a physically small, single-chip, transmitter front-end that can output high equivalent isotropically radiated power. This element radiation characteristic is wide-beam and suitable for array implementations