Flexible ceramic polymer composite substrates with spatially variable dielectrics for miniaturized RF applications

The goal of this research is to develop a process suitable for producing monolithic conformal substrates with a spatial arrangement of material cells according to a particular design creating novel material systems, useful for many multi- functional electronic and Radio Frequency devices. In this study, MCT ceramics (Mg-Ca-Ti-O systems) and organic binders (polymer solution) are mixed and fabricated as films through a process called tape casting to compromise between high dielectric constant and flexibility. Prior to optimizing the process, several characterization studies are carried out: Commercial spray dried MCT powders (Transtech Inc.) with dielectric constant k=70 and k=20 were analyzed as pressed and produced into tape cast films. Dielectric properties are then measured by an Agilent 16451B material analysis kit and their microscopic behavior is examined by scanning electron microscopy. Results show that flexible composite films show a maximum dielectric constant of e~22 unlike their powder pressed form with e ~16 but their loss behavior deteriorates when compared with their sintered form and a loss tangent factor of 0.001. The difference is attributed to the air content vs. polymer presence of the material in powder pressed form. Also, these substrates naturally are no longer flexible; hence studies are focused on their tape cast form. The potential of these dielectric shades to serve as candidate constituents for producing monolithic textured polymer-ceramic-composites with controllable loss is studied further. Four properties are of prime importance: tunability of dielectric constants to achieve miniaturization, flexibility via low temperature processing of polymers and loss controllability

A novel 1.5 '' quadruple antenna for tri-band GPS applications

A new global positioning system (GPS) antenna is proposed to cover the three GPS bands (L1, L2, and L5, namely 1575, 1227, and 1176 MHz) with the L5 band to be added after 2006. The developed antenna size is only 1.5" x 1.5" in aperture corresponding to lambda/7 x lambda/7 (lambda = free space wavelength) and lambda/13 thick. Quadrature feeding is employed to ensure right-hand circular polarized (RHCP) radiation. The final miniature antenna exhibits a gain greater than 2 dBi, and to our knowledge this is the smallest such size for circular polarized (CP) operation covering all three bands. Detailed parametric simulations leading to the best design along with measurements for the constructed antenna are presented

Optimization of aperture coupled microstrip patch antennas

Aperture coupled microstrip patch antennas (ACMPA) are special class of microstrip antennas with high gain and wide impedance bandwidth. These antennas differ from other microstrip antennas with their feeding structure of the radiating patch element. Input signal couples to the radiating patch through the aperture that exists on the ground plane of the microstrip feedline. These special antennas are multilayer stacked type of antennas with so many design variables that will affect the antenna performance. This paper presents the design and optimization procedure of ACMPA while taking care of all possible design variables and parameters to get the highest possible antenna gain and minimum VSWR

Circularly polarized localized near-field radiation at the nanoscale

A novel nano-antenna configuration is suggested to achieve circularly polarized optical spots beyond the diffraction limit. Intense optical spots with circular polarization are obtained using a cross-dipole nano-antenna

Automated Topology Design for Electromagnetic Devices

In this paper a novel automated design procedure based on the integration of a full wave Finite Element Analysis (FEA) and a topology design method employing Sequential Linear Programming (SLP) is introduced. The employed topology design method is the Solid Isotropic Material with Penalization (SIMP) technique which is formulated as a general non‐linear optimization problem. SLP is used to solve the optimization problem with the sensitivity analysis based on the adjoint variable method for complex variables. A key aspect of the proposed design method is the integration of optimization tools with a fast simulator based on the Finite Element‐Boundary Integral (FE‐BI) method. The capability of the proposed design method is demonstrated by designing a patch antenna subject to pre‐specified bandwidth and miniaturization criteria. Results show that the proposed design method is capable of designing full three‐dimensional volumetric material textures and printed conductor topologies for filters and patch antennas with enhanced performance. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87915/2/2155_1.pd

Incorporation of biochar to improve mechanical, thermal and electrical properties of polymer composites

The strive for utilization of green fillers in polymer composite has increased focus on application of natural biomass-based fillers. Biochar has garnered a lot of attention as a filler material and has the potential to replace conventionally used inorganic mineral fillers. Biochar is a carbon rich product obtained from thermochemical conversion of biomass in nitrogen environment. In this review, current studies dealing with incorporation of biochar in polymer matrices as a reinforcement and conductive filler were addressed. Each study mentioned here is nuanced, while addressing the same goal of utilization of biochar as a filler. In this review paper, an in-depth analysis of biochar and its structure is presented. The paper explored the various methods employed in fabrication of the biocomposites. A thorough review on the effect of addition of biochar on the overall composite properties showed immense promise in improving the overall composite properties. An analysis of the possible knowledge gaps was also done, and improvements were suggested. Through this study we tried to present the status of application of biochar as a filler material and its potential future applications

Airport Retailing at European airports using the example of Hamburg Airport

Die vorliegende Arbeit beschäftigt sich mit dem Airport Retailing an europäischen Flughafenstandorten mit dem Fokus auf Einzelhandel und Gastronomie. Ziel ist es zu klären, von welchen Faktoren der Erfolg eines Shoppingcenter Konzepts abhängig ist. Dabei wird zunächst die theoretische Grundlage erarbeitet, in der das Forschungsfeld des Retailbereiches in seinen Eigenschaften und die Auswirkungen der architektonischen Gestaltung von Flughafengebäuden auf das Kaufverhalten der Konsumenten erläutert wird, um anschließend Erfolgsfaktoren von Shoppingcenter Konzepten an Flughäfen herauszustellen. Das theoretische Fundament ist durch eine Analyse der Retailaktivitäten des Flughafens Hamburg erweitert und soll eine Aufklärung über den Deckungsgrad der Beobachtungen mit der Theorie und die Funktionstüchtigkeit eines solchen Konzepts leisten, um unterschiedliche Zukunftsstrategien herausarbeiten zu können