Нелинейные эффекты в реконфигурируемой антенне

Полный текст доступен на сайте издания по подписке: http://radio.kpi.ua/article/view/S0021347018030020Современные телекоммуникационные системы, работающие с различными стандартами передачи данных, часто строятся на основе использования реконфигурируемых антенн. Включение в излучающую структуру антенны нелинейных радиоэлементов позволяет получить не только расширение функциональных возможностей антенны (переключение рабочей частоты, изменение формы диаграммы направленности, изменение поляризации, входного импеданса и т. п.), но и может вызывать ряд нелинейных эффектов, искажающих характеристики антенны и передаваемые данные. В связи с этим актуальными являются вопросы, рассмотренные в данной работе. А именно: описана методика численного анализа нелинейных эффектов в реконфигурируемых антеннах, рассмотрены особенности применяемых в антеннах нелинейных коммутационных радиоэлементов, проведены численные исследования влияния вольт-фарадной характеристики коммутатора излучающей структуры и мощности возбуждения на характеристики антенны. Выполненные оценочные исследования позволяют получать общие представления и осуществлять прогнозирование нелинейных искажений в реконфигурируемых антеннах, вызванных присутствием в них коммутаторов различных типов

High-Performance Piezoresistive MEMS Strain Sensor with Low Thermal Sensitivity

This paper presents the experimental evaluation of a new piezoresistive MEMS strain sensor. Geometric characteristics of the sensor silicon carrier have been employed to improve the sensor sensitivity. Surface features or trenches have been introduced in the vicinity of the sensing elements. These features create stress concentration regions (SCRs) and as a result, the strain/stress field was altered. The improved sensing sensitivity compensated for the signal loss. The feasibility of this methodology was proved in a previous work using Finite Element Analysis (FEA). This paper provides the experimental part of the previous study. The experiments covered a temperature range from −50 °C to +50 °C. The MEMS sensors are fabricated using five different doping concentrations. FEA is also utilized to investigate the effect of material properties and layer thickness of the bonding adhesive on the sensor response. The experimental findings are compared to the simulation results to guide selection of bonding adhesive and installation procedure. Finally, FEA was used to analyze the effect of rotational/alignment errors

Optimizing microneedle arrays for transdermal drug delivery: extension to non-square distribution of microneedles

The technology of fabricating microneedle arrays to deliver high molecular weight drugs across skin in a minimally invasive manner is receiving increasing attention. Microneedle arrays with different geometries have been manufactured using materials such as glass, polymer, metal, etc. However, a framework that can identify the optimum designs of these arrays seems to be lacking. This is important since by optimising the microneedles dimensions (e.g., surface area of the patch, microneedle radius, etc) the permeability of drugs in skin can be increased. To address this issue, this study presents an optimization framework for transdermal delivery of high molecular weight drug from microneedle. The optimization process is based on determining an optimisation function (g) for various microneedles patterns (e.g., square, diamond, triangular, etc). We argue that higher the value of g is the higher the drug permeability in skin is. The outputs of the developed framework have allowed us to identify the optimum design of both solid and hollow microneedles. In particular, the results have been used to predict skin permeability of high molecular weight using microneedle system. Also, optimum designs based on different classifications of skin thickness (e.g., race, age, etc) for transdermal delivery of drugs are suggested

Modelling and control strategies for hydrokinetic energy harnessing

The high prices and depletion of conventional energy resources and the environmental concern due to the high emission of CO2 gases have encouraged many researchers worldwide to explore a new field in renewable energy resources. The hydrokinetic energy harnessing in the river is one of the potential energies to ensure the continuity of clean, reliable, and sustainable energy for the future generation. The conventional hydropower required a special head, lots of coverage area, and some environmental issues. Conversely, the hydrokinetic system based on free stream flowing is one of the best options to provide the decentralised energy for rural and small-scale energy production. Lately, the effort of energy harnessing based on hydrokinetic technology is emerging significantly. Nevertheless, several challenges and issues need to be considered, such as turbine selection for energy conversion, generalised turbine model and control strategies for the grid and non-grid connection. To date, no detailed information on which turbines and turbine model are most suited to be implemented that match Malaysia’s river characteristics. Besides, a large oscillation has occurred on the output current and power during dynamic steady state due to the water variation and fluctuation in the river. Hence, reducing the energy extraction and controller efficiency for stand-alone and grid-connected systems, respectively. Therefore, the study aims to analyse the different turbine's design, proposed the turbine model, and propose the potential control strategies for stand-alone and grid-connected hydrokinetic energy harnessing in the river. In this work, three types of vertical axis turbines, including the H-Darrieus, Darrieus, and Gorlov with twelve different NACA and NREL hydrofoils, were analysed using the QBlade and MATLAB software, respectively. The effect of symmetrical and non-symmetrical geometry profiles, hydrofoils thicknesses, and turbine solidities have been compared to choose one of the best option turbines based on the highest power coefficient (CP) and a torque coefficient (CM), respectively. Subsequently, the turbine power model generalised equation has been proposed to represent the hydrokinetic turbine characteristic using a polynomial estimation equation. On the other hand, the MPPT control strategy is employed for the off-grid system using the sensorless method. The circuit topology based on an uncontrolled rectifier with the DC boost converter is implemented to regulate the rectifier output voltage through duty ratio. Subsequently, the metaheuristic method based on the combination of the Hill-Climbing Search (HCS) MPPT algorithm and the Fuzzy Logic Controller has been proposed to produce a variable step size compared to the fixed step size in conventional HCS algorithm. On the contrary, the dynamic model of the grid-connected hydrokinetic system has been linearised for small-signal stability analysis. The eigenvalues analysis-based approached has been applied to evaluate the system stability due to the small disturbance. The PI controller with the eigenvalues tracing method has been proposed to improve the system stability by reducing the oscillation frequency. The research outcomes indicated that the H-Darrieus with NACA 0018 was the best turbine for energy conversion in the river. Besides, the HCS-Fuzzy MPPT algorithm improved the energy extraction up to 88.30 % as well as reduced 74.47 % the oscillation compared to the SS-HCS MPPT. The stability of grid-connected hydrokinetic energy harnessing was improved up to 63.63 % by removing the oscillation frequency at states of λ8,9,10,11 as well as reducing 40.1 % oscillation of the generator stator current at the rotor side controller (RSC)

Microrobots for wafer scale microfactory: design fabrication integration and control.

Future assembly technologies will involve higher automation levels, in order to satisfy increased micro scale or nano scale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to micro-electronics and MEMS industries, but less so in nanotechnology. With the bloom of nanotechnology ever since the 1990s, newly designed products with new materials, coatings and nanoparticles are gradually entering everyone’s life, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than with top-down robotic assembly. This is due to considerations of volume handling of large quantities of components, and the high cost associated to top-down manipulation with the required precision. However, the bottom-up manufacturing methods have certain limitations, such as components need to have pre-define shapes and surface coatings, and the number of assembly components is limited to very few. For example, in the case of self-assembly of nano-cubes with origami design, post-assembly manipulation of cubes in large quantities and cost-efficiency is still challenging. In this thesis, we envision a new paradigm for nano scale assembly, realized with the help of a wafer-scale microfactory containing large numbers of MEMS microrobots. These robots will work together to enhance the throughput of the factory, while their cost will be reduced when compared to conventional nano positioners. To fulfill the microfactory vision, numerous challenges related to design, power, control and nanoscale task completion by these microrobots must be overcome. In this work, we study three types of microrobots for the microfactory: a world’s first laser-driven micrometer-size locomotor called ChevBot，a stationary millimeter-size robotic arm, called Solid Articulated Four Axes Microrobot (sAFAM), and a light-powered centimeter-size crawler microrobot called SolarPede. The ChevBot can perform autonomous navigation and positioning on a dry surface with the guidance of a laser beam. The sAFAM has been designed to perform nano positioning in four degrees of freedom, and nanoscale tasks such as indentation, and manipulation. And the SolarPede serves as a mobile workspace or transporter in the microfactory environment

Koseido purasuchikku maikuro nano kozotai sakusei to kagaku seikagaku maikurochippu eno oyo

制度:新 ; 報告番号:甲3060号 ; 学位の種類:博士(工学) ; 授与年月日:2010/3/15 ; 早大学位記番号:新532

LIGA cavity resonators and filters for microwave and millimetre-wave applications

High performance microwave cavities for various circuits in the front-end of transceivers such as filters, diplexers, and oscillators have conventionally been built with rectangular or cylindrical metallic waveguides, which typically have low loss, high quality (Q) factor, and higher power handling capability. However such waveguide cavity based circuits made by traditional metal machining techniques tend to be costly, particularly for complex multiple cavity based circuits, and not well suited to high volume commercial applications and integration with planar microwave integrated circuits. As commercial transceiver applications progress toward higher microwave and millimetre-wave frequencies, the use of waveguide based circuits for compact, highly integrated transceivers is becoming feasible, along with an increasing need for cost effective batch fabrication processes for realizing complex metallic cavity circuits without sacrificing structural quality and performance. It is expected that significant advancements in both microwave performance and integration will be achieved through the development of novel technologies for realizing vertically oriented three-dimensional (3-D) structures.Although improvement has been made on increasing the resonator Q factor by exploiting silicon micromachining and low-temperature cofired ceramics (LTCC) techniques, there are some drawbacks inherent to silicon cavity micromachining and LTCC technology, including non-vertical sidewalls, depth limitations, and surface roughness for the silicon resonator, and dielectric and radiation loss for LTCC resonator.Polymer-based fabrication is a promising alternative to silicon etching and LTCC technologies for the batch fabrication of ultra-deep microwave cavity structures. In particular, deep X-ray lithography (XRL), as part of the LIGA process, is a microfabrication technology for precisely structuring polymers, and is increasingly being applied to RF/microwave microstructures. In addition to precise patterning capabilities, deep XRL is able to structure ultra-deep cavities due to the penetration ability of hard X-rays. Cavities of several millimetres are possible in a single lithographic exposure, and with excellent sidewall quality, including verticality near 90 degrees and surface roughness on the order of tens of nanometres. These structured polymers are subsequently used as electroforming templates for fabricating metal structures with correspondingly good sidewall quality.This thesis investigates the possibility of realizing high-Q cavity resonators and filters at microwave frequencies using the LIGA microfabrication process. Finite element method (FEM) electromagnetic simulation results based on the cavity models representing different fabrication conditions show that smooth LIGA cavity structures result in promising Q improvement over silicon and LTCC structures. And the potential advantages of LIGA resonators are more dramatic with cavity height and increasing operating frequency. Deep polymer cavity structures (1.8 mm) fabricated using deep XRL demonstrate excellent sidewall verticality in the PMMA structure, with only slight shrinkage at the top surface of 8.5 2.5 mm in either lateral dimensions. This corresponds to sidewalls with verticality between 89.82o and 89.9o. The structure polymers are subsequently used as templates for metal electroforming to produce cavity resonators. The performance of the resonator is measured in a planar environment. A RT/duroid6010 soft substrate patterned with coupling structures forms the sixth side, and thus completes the cavity. Despite the rather crude test assembly for the sixth side made by clamping, the measured resonator has a high unloaded Q of 2122.2 85 at the resonant frequency of 24 GHz, indicating that LIGA cavities are especially promising for high performance applications. The relatively simple, single-step lithographic exposure also facilitates extension to more structurally complicated waveguide and multiple cavity-based circuits. This research work also proposes a high performance ``split-post' 3-pole cylindrical post coupled Chebyshev bandpass filter suitable for LIGA fabrication. In addition to potentially batch fabricating such a filter lithographically by exposing the entire waveguide depth in a single exposure, the filter structures composed of three cavities with metallic multi-post coupling would be extremely difficult to fabricate using traditional machining techniques, due to the extremely fine post structure and high vertical aspect ratio required. However, these types of structures could be ideal for LIGA fabrication, which offers sub-micron features, aspect ratios of 100:1 or higher, resist thicknesses of up to 3 mm, and almost vertical and optically smooth sidewalls. Also, representative LIGA sidewall roughness is used to predict very low loss and high performance, suggesting that complicated structures with multiple resonator circuits and high internal components with high aspect ratios are possible

Biologically inspired feature extraction for rotation and scale tolerant pattern analysis

Biologically motivated information processing has been an important area of scientific research for decades. The central topic addressed in this dissertation is utilization of lateral inhibition and more generally, linear networks with recurrent connectivity along with complex-log conformal mapping in machine based implementations of information encoding, feature extraction and pattern recognition. The reasoning behind and method for spatially uniform implementation of inhibitory/excitatory network model in the framework of non-uniform log-polar transform is presented. For the space invariant connectivity model characterized by Topelitz-Block-Toeplitz matrix, the overall network response is obtained without matrix inverse operations providing the connection matrix generating function is bound by unity. It was shown that for the network with the inter-neuron connection function expandable in a Fourier series in polar angle, the overall network response is steerable. The decorrelating/whitening characteristics of networks with lateral inhibition are used in order to develop space invariant pre-whitening kernels specialized for specific category of input signals. These filters have extremely small memory footprint and are successfully utilized in order to improve performance of adaptive neural whitening algorithms. Finally, the method for feature extraction based on localized Independent Component Analysis (ICA) transform in log-polar domain and aided by previously developed pre-whitening filters is implemented. Since output codes produced by ICA are very sparse, a small number of non-zero coefficients was sufficient to encode input data and obtain reliable pattern recognition performance

Multi-Agent Systems

A multi-agent system (MAS) is a system composed of multiple interacting intelligent agents. Multi-agent systems can be used to solve problems which are difficult or impossible for an individual agent or monolithic system to solve. Agent systems are open and extensible systems that allow for the deployment of autonomous and proactive software components. Multi-agent systems have been brought up and used in several application domains

Fabrication and Characterization of Polypyrrole/Gold Bilayer Microactuators for Bio-Mems Applications

The proof of concept for conjugated polymer bilayer microactuators had been demonstrated prior to this dissertation with numerous devices, and their advantages in biomedical applications had been recognized. The next step for this technology was implementation in real systems, which required knowledge of the main performance metrics and limitations. In this dissertation, work focused on measuring these metrics for the first time to facilitate the development of cell-clinics, which are microsystems for cell study and for cell-based sensing. The conjugated polymer used throughout the dissertation was polypyrrole doped with dodecylbenzenesulfonate, PPy(DBS), and the second layer in the bilayer was gold. Device fabrication challenges were first identified and addressed, focusing particularly on methods to produce PPy/Au bilayers that did not suffer from delamination. By electroplating Au onto the electrodes or by wet etching them to increase mechanical interlocking, this problem, which had plagued the field for the last decade, was solved. Another important contributor to lifetime, which is a key actuator metric, is loss of electro-activity with extended cycling. This metric was quantified through measurements of the total exchanged charge of PPy(DBS) with cycles of electromechanical redox. This result impacts how these actuators can be used. Two other key metrics on which this work focused were bending angle, analogous to stroke in a linear actuator, and force. It was necessary to determine bending angle as a function of film thickness experimentally because the traditional bilayer beam models could not account for microfabricated bilayer radius of curvature data. Through experimental testing over a wide range of PPy and Au thicknesses, the relationship between PPy:Au thickness ratio and curvature was mapped out. The experimental results demonstrated the existence of strain gradients within the conjugated polymer films, with the material at the surface having greater actuation strain than that at the gold interface. Finally, accurate force measurements had not been done prior to this dissertation research because of the significant challenges involved in developing a method for measuring force in microactuators. This dissertation described the development of such a methodology and provides data for the blocked force as a function of polypyrrole thickness