Gotowa bibliografia na temat „Dielectric embedded monopole radiating structures”

A microstrip-fed new UWB monopole antenna with a band-notch characteristic mounted on the finite cylindrical surface is presented. The proposed antenna consists of a rectangular metal radiation patch fed by a 50 ohm microstrip line and a rectangular ground plane. To achieve ultra-wideband, three modifications are introduced. The first one is to blend the upper and lower corners of the radiating plates. The second one is to remove a circular section from the radiating metal. The third one is to blend the upper corners of the ground plane. The antenna is designed on a substrate with dielectric constant εr=3 and 1.6 mm height. The proposed antenna is conformed on finite cylindrical substrates of radiuses 4, 5 and 6 cm. The cylindrical structures were simulated through CST microwave studio finite element package. The simulation results, obtained via CST package on the return losses, VSWR and radiation pattern of the antenna are presented. For both planar and conformal antennas, results show that the impedance bandwidth of the designed antenna is from 2-18 GHz with a return loss less than -10 dB (VSWR<2) and a band rejection of 5-6 GHz for wireless LAN (WLAN), that includes the band 5.15-5.825 GHz limited by IEEE 802.11.a and HIPERLAN/2 with return loss greater than -10dB. The proposed simple shaped conformal antenna provides a good radiation pattern and gain between 3.84 and 5.96 dBi over the entire frequency band excluding the rejected band.

Purpose Development of techniques for expedited design optimization of complex and numerically expensive electromagnetic (EM) simulation models of antenna structures validated both numerically and experimentally. The paper aims to discuss these issues. Design/methodology/approach The optimization task is performed using a technique that combines gradient search with adjoint sensitivities, trust region framework, as well as EM simulation models with various levels of fidelity (coarse, medium and fine). Adaptive procedure for switching between the models of increasing accuracy in the course of the optimization process is implemented. Numerical and experimental case studies are provided to validate correctness of the design approach. Findings Appropriate combination of suitable design optimization algorithm embedded in a trust region framework, as well as model selection techniques, allows for considerable reduction of the antenna optimization cost compared to conventional methods. Research limitations/implications The study demonstrates feasibility of EM-simulation-driven design optimization of antennas at low computational cost. The presented techniques reach beyond the common design approaches based on direct optimization of EM models using conventional gradient-based or derivative-free methods, particularly in terms of reliability and reduction of the computational costs of the design processes. Originality/value Simulation-driven design optimization of contemporary antenna structures is very challenging when high-fidelity EM simulations are utilized for performance utilization of structure at hand. The proposed variable-fidelity optimization technique with adjoint sensitivity and trust regions permits rapid optimization of numerically demanding antenna designs (here, dielectric resonator antenna and compact monopole), which cannot be achieved when conventional methods are of use. The design cost of proposed strategy is up to 60 percent lower than direct optimization exploiting adjoint sensitivities. Experimental validation of the results is also provided.

With the rapid of growth of wireless connectivity more demand is placed on the need for innovative technologies capable of satisfying increasing user demand and network capacity. Adaptive antennas systems or most commonly known as Smart Antennas are expected to be implemented in the next generation of wireless systems. Their implementation avails in dynamic adaptation to spatial and temporal conditions affecting the quality of communication, while offering tremendous flexibility to wireless providers. However one of the major challenges facing Smart Antenna technology is the inherent complexity of the antenna structure, associated control algorithm and implemented RF components possibly contributing to the delay of commercial interest. This thesis will present various adaptive antenna configurations that utilize an embedded dielectric in order to achieve significant size reduction and mechanical rigidity while maintaining favorable electromagnetic performance. In order to constrict the lateral ground plane dimension, a cylindrical shaped hollow ground skirt was attached to the antenna structures effectively compromising between effective beam forming in the azimuth plane and physical size. The complexity of these antenna structures requires a more contemporary design approach which involved computer modeling using a commercial available Finite Element software package and optimization using a developed generic Genetic Algorithm based optimization program. A dielectric embedded 7-element monopole array antenna featuring switched parasitic elements is presented and optimized for maximum vertically polarized gain in the horizontal plane, producing an antenna structure with a radial length of less then 0.25λ and total height of 0.4&alamba which was shown to radiate a main lobe beamwidth of 80 degrees with an absolute gain of 4.8dBi at 2.45GHz. Further on a dielectric embedded 7-element monopole array antenna featuring parasitic elements terminated with finite set of terminating reactive loads is presented with a radial length of less then 0.25&alambda and total height of 0.4&alambda. The antenna structure and reactive load combination were optimized for maximum horizontal gain producing a principal main lobe with a measured gain of 5.1dBi and beamwidth of 110 degrees at 2.48GHz. Finally it was shown single and dual radiation lobes maybe produced when active monopoles elements are placed eccentric in a circular shaped dielectric material. A circular array of elements embedded in a dielectric material was realized with measured gains of single and dual beam radiation at 2.45GHz was shown to be 5.18dBi and 3.65Bi respectively with corresponding beamwidths of 78.5 degrees and 53 degrees.

With the rapid of growth of wireless connectivity more demand is placed on the need for innovative technologies capable of satisfying increasing user demand and network capacity. Adaptive antennas systems or most commonly known as Smart Antennas are expected to be implemented in the next generation of wireless systems. Their implementation avails in dynamic adaptation to spatial and temporal conditions affecting the quality of communication, while offering tremendous flexibility to wireless providers. However one of the major challenges facing Smart Antenna technology is the inherent complexity of the antenna structure, associated control algorithm and implemented RF components possibly contributing to the delay of commercial interest. This thesis will present various adaptive antenna configurations that utilize an embedded dielectric in order to achieve significant size reduction and mechanical rigidity while maintaining favorable electromagnetic performance. In order to constrict the lateral ground plane dimension, a cylindrical shaped hollow ground skirt was attached to the antenna structures effectively compromising between effective beam forming in the azimuth plane and physical size. The complexity of these antenna structures requires a more contemporary design approach which involved computer modeling using a commercial available Finite Element software package and optimization using a developed generic Genetic Algorithm based optimization program. A dielectric embedded 7-element monopole array antenna featuring switched parasitic elements is presented and optimized for maximum vertically polarized gain in the horizontal plane, producing an antenna structure with a radial length of less then 0.25λ and total height of 0.4&alamba which was shown to radiate a main lobe beamwidth of 80 degrees with an absolute gain of 4.8dBi at 2.45GHz. Further on a dielectric embedded 7-element monopole array antenna featuring parasitic elements terminated with finite set of terminating reactive loads is presented with a radial length of less then 0.25&alambda and total height of 0.4&alambda. The antenna structure and reactive load combination were optimized for maximum horizontal gain producing a principal main lobe with a measured gain of 5.1dBi and beamwidth of 110 degrees at 2.48GHz. Finally it was shown single and dual radiation lobes maybe produced when active monopoles elements are placed eccentric in a circular shaped dielectric material. A circular array of elements embedded in a dielectric material was realized with measured gains of single and dual beam radiation at 2.45GHz was shown to be 5.18dBi and 3.65Bi respectively with corresponding beamwidths of 78.5 degrees and 53 degrees.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Microelectronic Engineering
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Natural toroidal molecules, such as biomolecules [1] and proteins [2], possess toroidal dipole moments that are hard to be detected, which leads to extensive studies of artificial toroidal materials. Metamaterials [3-4] are sub-wavelength artificial structures that can be specifically designed to manipulate the intensity of induced electromagnetic multidipoles. Recently, toroidal metamaterials [5-6] have been widely investigated to enhance toroidal dipole moments while the other multipoles are eliminated due to the spacial symmetry. However, to effectively excite a toroidal dipole, a specific excitation method is necessary since a closed-loop of induced magnetic dipoles in a toroidal metamaterial weakly interact with the external wave. This is a key issue that has to be carefully taken into account in existing toroidal experiments. Moreover, most of generated toroidal dipole moments are either aligned vertically to the substrate surface or embedded in a dielectric, leading to another constraint for further applications. In this paper, we present a novel design for a toroidal metamaterial with multilayered structures, which composed of a gold dumbbell-shaped aperture and a vertical split-ring resonator (VSRR). The induced toroidal dipoles show several advantages like free-standing and vertically oscillating configuration that are distinguishable from previously reported works. It is worth to mention that the non-radiating from the destructive interference from the toroidal and electric dipoles can also be generated in our proposed structures.