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

Obtaining circularly polarized optical spots beyond the diffraction limit using plasmonic nano-antennas

With advances in nanotechnology, emerging plasmonic nano-optical applications, such as all-optical magnetic recording, require circularly-polarized electromagnetic radiation beyond the diffraction limit. In this study, a plasmonic cross-dipole nano-antenna is investigated to obtain a circularly polarized near-field optical spot with a size smaller than the diffraction limit of light. The performance of the nano-antenna is investigated through numerical simulations. In the first part of this study, the nano-antenna is illuminated with a diffraction-limited circularly-polarized radiation to obtain circularly polarized optical spots at nanoscale. In the second part, diffraction limited linearly polarized radiation is used. An optimal configuration for the nano-antenna and the polarization angle of the incident light is identified to obtain a circularly polarized optical spot beyond the diffraction limit from a linearly polarized diffraction limited radiation

Optimization of plasmonic nano-antennas

The interaction of light with plasmonic nano-antennas is investigated. First, an extensive parametric study is performed on the material and geometrical effects on dipole and bow-tie nano-antennas. The transmission efficiency is studied for various parameters including length, thickness, width, and composition of the antenna as well as the wavelength of incident light. The modeling and simulation of these structures is done using 3-D finite element method based full-wave solutions of Maxwell’s equations. Next, a modeling-based automated design optimization framework is developed to optimize nano-antennas. The electromagnetic model is integrated with optimization solvers such as gradient-based optimization tools and genetic algorithms

SURALP-L – İnsansı Robot Platformu Bacak Modülü

SURALP, Sabancı Üniversitesi laboratuvarlarında tasarlanmıs ve imal edilmekte olan yeni bir insansı robot platformudur. Đmalatı tamamlandığında; bacaklarında, kollarında, boynunda ve gövdesinde toplamda 30 serbestlik derecesine sahip olması planlanmaktadır. Su ana kadar bu robotun bacak modülü olan, 12 serbestlik derecesine sahip SURALP-L’nin üretimi tamamlanmıstır. Bu bildiri, bacak modülünün ve tüm robotun tasarım esaslarını anlatmaktadır. Mekanik tasarım, tahrik mekanizmaları, algılayıcılar, kontrol donanımı ve algoritmaları ele alınmıstır. Tahrik sistemleri, DC motorlara bağlanmıs kayıs kasnak mekanizmaları ve Harmonic Drive redüktör ünitelerini içermektedir. Algılama sistemi, eklem motor kodlayıcıları, kuvvet/moment algılayıcıları ve atalet algılayıcılarından olusmaktadır. Kontrol sisteminin ana kısmını, dSpace sayısal sinyal isleme modülü olusturmaktadır. Robotun kararlı yürüyüsünü sağlamak amacıyla yumusak yürüyüs referansları kullanılmıstır. Zemin darbe telafisi, erken basma referans yörüngesi iyilestirmesi, ayak yönelim kontrolü ve bağımsız eklem konum kontrolü kullanılan ana kontrol algoritmalarıdır. Bacak modülüyle elde edilen deney sonuçları bildirinin son bölümünde sunulmustur