In this thesis, we described our efforts to achieve antenna radomes that enhance antenna gain by using the artificial synthesis structure of the left-handed material. The characteristics of the metamaterial are introduced. Also, we will analyze the phenomena of the left-handed material which distinguish them from the right-handed material. Moreover, we analyze and derive the theory to obtain the effect of the meta-materials with the metal line artificial synthesis array structure. Then, we will focus on the method of lowering the frequency of the left-handed material structure and discuss the frequency influence of the permeability, permittivity, and refractive index as the modulus of the refractive index is smaller than one or negative. We will adjust the structure to allow a wider useful frequency bandwidth. In order to prevent from the reflection of the metal lines to cause too much loss, we will simplify the structure of the single unit. Making use of the above-mentioned methods, we use the material to achieve an antenna radome. The meta-material radome can reduce the 3 dB beam-width by about 30 percent compared with the conformal patch at 5.25 GHz. Finally, we design a novel structure of unit cell based on the CSRR which is provided with a broadband negative index of refraction. The relative bandwidth of the LHM proposed in this thesis is 36.5%. In order to reduce loss tangent we remove the dielectric substrate, which further reduce the 3 dB beam-width.

No description available.

Les métamatériaux sont des matériaux artificiels devenus très attractifs du fait de leurs propriétés électromagnétiques atypiques. Les structures CRLH (Composite Right Left-Handed) à ondes de fuite en particulier, permettent d’effectuer un balayage angulaire très important sur une large bande passante. Toutefois l’état de l’art montre qu’il faudrait un très grand nombre de cellules pour atteindre une efficacité de rayonnement acceptable. Vue la demande récurrente des nouveaux systèmes de transmission d’avoir des antennes de faible encombrement, il serait plus intéressant de trouver de nouvelles architectures d’antennes utilisant ces structures CRLH. L’objectif de la thèse est en premier lieu d’avoir une connaissance approfondie du comportement électromagnétique des structures CRLH. Afin de tirer profit de leurs propriétés électromagnétiques atypiques, de nouvelles architectures d’antennes inspirées des structures CRLH sont proposées. Ces nouvelles antennes permettent de réaliser différents types de diagrammes de rayonnement (large ouverture angulaire, faisceau étroit, double polarisation). Elles sont caractérisées grâce à une modélisation analytique qui aura été validée auparavant par la simulation électromagnétique. / Metamaterials are artificial structures with unusual electromagnetic properties. Composite Right-Left Handed (CRLH) radiating structures are very attractive antennas because of their scanning capability and wideband performances. However crlh lines must contain a large number of cells in order to have sufficient radiation efficiency. Due to the recurring request of having small antennas in new communication systems, new designs based on crlh structures must be found. The first objective of this thesis is to have full knowledge of electromagnetic properties of crlh structures. To take advantages of atypical electromagnetic behavior of CRLH structures, new CRLH based antennas designs are proposed. These new inspired antennas could produce different radiation patterns (with large beamwidth, narrow beam, double polarization). Analytical model, previously validated by electromagnetic simulator, is used to characterize the new proposed antennas.

No description available.

No description available.

In our thesis we deal with the development of writing skills of left-handed children and with dificulties which are caused by uncorrect methodological help. Our thesis is divided into two parts. In the theoretic one we outline problems of the occurrance of the left-handness with regard to the brain asymmetry and changes of the laterality during person{\crq}s development. We focus on the way how to recognize wether the child is the left-hander or the right-hander and on the correct methodological help with writing of left-handed children. The other part of our thesis is practical part. In this part we make the concept of the copy-book for left-handed children, it means the copy-book with the neutral slope of letters. This neutral slope is more natural for left-handers. The thesis is documented with supplementory material.

DIPOMA THESIS IS CONCERNED IN ISSUES OF LATERALITY, FOCUSED ON LEFT HANDED WRITING. THESIS ACQUAINTS READERS WITH AN INVESTIGATION OF LATERALITY AND INDIVIDUAL TESTS OF UPPER AND LOWER EXTREMITIES AND THE LEADING EYE AND EAR. IT EMPHASIZES THE NEGATIVE CONSEQUENCES OF SUPPRESSED LEFT HANDED WRITING, THE HARMONIOUS DEVELOPMENT OF A LEFT-HANDED CHILD AND THE NEED OF HIS OR HER APPROPRIATE TRAINING. DIPLOMA THESIS CONCERNS IN THE METHODOLOGY OF LEFT-HANDED WRITING. DIPLOMA THESIS POINTS OUT THE PROBLEM AREAS AND COMPARES THE METHODOLOGY OF HOW THE CHILDREN LEARN TO WRITE WITH THEIR LEFT HAND IN THE FIRST AND THE SECOND CLASS AND HOW THE CHILDREN WRITE AT SECONDARY SCHOOL.

Chinese left-handed are found to be very few, especially in terms of handwriting. The Chinese educational policy that fully entitles teachers in primary school to change the left-handed students to write with their right-hand, by nudging and even force, is found to be mainly blamed as the main cause. The thesis is to raise the ethical discussion and define this policy as being discriminatory against the left-handed by checking the features, definition and identification of discrimination, and reasons forming and supporting such a discriminatory policy will be taken into the major consideration as the source of discrimination. Therefore, the thesis is to propose solutions to help with the abolishment of the policy and the elimination of the prejudicial attitudes toward the left-handed, especially in terms of writing. The thesis itself, due to the limit of previous research and scientific support, has its own blindness or disadvantage, however, such a work could be helpful with the later discussion.

A full wave finite-difference time-domain method (FDTD) combined with thin-wire and thin-slot algorithms to analyze a metamaterial fabricated with periodic mushroom structures, is proposed in this dissertation. This proposed method is suitable for analyzing problems involving large structures with fine structural details. A periodic analysis for mushroom structures is presented. Only a single unit mushroom cell is required to present the phenomena of infinite periodicity with the help of periodic boundary conditions (PBCs). The composite right-/left-handed (CRLH) transmission line (TL) approach is introduced and used to approximate CRLH metamaterial through lumped L and C. Finally, several CRLH metamaterial mushroom-based structures are investigated. A 19 by 8 flat microwave lens and a parabolic microwave lens structure composed of 410 unit mushroom cells are investigated. These structures demonstrate negative refractive index (NRI) characteristics while operate in the left-hand (LH) region. The simulation and measurement results of one- and two-dimensional CRLH mushroom-based structures are compared.

In this thesis, we introduce a LHM (Left-Handed Material) with both negative permittivity and permeability. Improvement of gain antenna is achieved by utilizing the characteristics of the LHM which can focus the EM wave. We start with an analysis of electromagnetic characteristic of LHM, especially its negative index of refraction. Structures with only negative permittivity or negative permeability are also analyzed. Then, we design the structure of LHM that can reduce the sensitivity of S11 of an antenna. So that the antenna operating frequency is not changed even in the presence of the LHM. The LHM unit cell structure comes from the idea by combination of two basic SNG (Single Negative) structure. We design a unit cell whose index of refraction is negative and close to zero. Further, we combine LHM and antenna. Simulation and measurement results show that the LHM is effective. The reflection coefficient of antenna does not change much by the combination of proposed LHM. The half power beam¡Ðwidth of antenna become narrower. The antenna gain improvement can be about 3 dB or higher. Finally, the LHM has been miniaturized successfully, resulting in reduction in size by about 50%. Comparing simulation and measurement, we find the LHM is still effective. A dipole antenna is used to verify out design. The antenna gain has been enhanced and the reflection coefficient does not change much.