Complete Simulation of an IEEE 802.11 Wireless Network using a Full Wave Electromagnetic Tool Dynamically Coupled to a RF System Simulator

The purpose of this study is to fully evaluate a short range IEEE 802.11g channel at 2.4 GHz frequency by dynamic linking Ansys HFSS, a full wave electromagnet tool, and Ansys Designer, a system level design simulator. The study presented in paper shows the integration of a 3D field solver and a circuit solver that enables the calculation of radiation patterns, electric field plots, bit error rate, constellation plots while incorporates the actual transmitter and receiver antennas and devices as well as TX/RX system with numerous modulation schemes. Multipath effects are also considered because the entire physical environment is modeled. Frequency and time domain responses are seamlessly combined in order to yield a complete response of the entire system. The scenario of the WiFi network is a room comprised of a router, a notebook and a phone. The concepts shown in this paper can be applied to Zigbee, Bluetooth, WiMax and many other wireless network types

Estudo e implementação de um processo de fabricação de microponteiras de Si utilizando plasma de hexafluoreto de enxofre e oxigenio

Orientador: Edmundo da Silva BragaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Desenvolvemos e caracterizamos um processo de fabricação de microponteiras de silício utilizando plasma de radiofreqüência (RF). Foram estabelecidos processos de corrosão iônica reativa (RIE) do silício e dióxido de silício em um reator de placas paralelas utilizando SF6 e a mistura gasosa SF6/O2. Foram caracterizadas as grandezas exigidas ao processo de fabricação, tais como taxa de corrosão, seletividade, anisotropia e qualidade da superfície, e foram comparadas a outros processos. Foram analisados e caracterizados os mecanismos de corrosão do processo desenvolvido. Microponteiras de silício com diferentes razões de aspectos foram caracterizadas e fabricadas utilizando a mistura gasosa em diferentes proporções. Os melhores resultados foram obtidos utilizando-se um plasma com uma concentração de 25% de oxigênio e 75% de hexafluoreto de enxofreAbstract: We have developed and characterized a silicon microtip fabrication process using radiofrequency (RF) plasma. Reactive Ion Etching processes of silicon and silicon dioxide in a parallel plate reactor were established using SF6 and SF6/O2 gas mixture. The parameters of the fabrication process, such as the etch rate, selectivity, anisotropy and surface quality were characterized and compared with other processes. The etching mechanisms of the developed process were analyzed and characterized. Silicon microtips with different aspect ratios were fabricated and characterized using the gaseous mixture at different concentrations. The best results were obtained using plasma comprised of 25% of oxygen and 75% of sulfur hexafluorideMestradoEletrônica, Microeletrônica e OptoeletrônicaMestre em Engenharia Elétric

Optimizing the e-beam profile of a single carbon nanotube field emission device for electric propulsion systems

Preliminary studies on field emission (FE) arrays comprised of carbon nanotubes (CNT) as an electron source for electric propulsion system show remarkably promising results. Design parameters for a carbon nanotube (CNT) field-emission device operating on triode configuration were numerically simulated and optimized in order to enhance the e-beam focusing quality. An additional focus gate (FG) was integrated to the device to control the profile of the emitted e-beam. An axisymmetric finite element model was developed to calculate the electric field distribution on the vacuum region and a modified Fowler-Nordheim (FN) equation was used to evaluate the current density emission and the effective emitter area. Afterward, a FE simulation was employed in order to calculate the trajectory of the emitted electrons and define the electron-optical properties of the e-beam. The integration of the FG was fully investigated via computational intelligence techniques. The best performance device according to our simulations presents a collimated e-beam profile that suits well for field emission displays, magnetic field detection and electron microscopy. The automated computational design tool presented in this study strongly benefits the robust design of integrated electron-optical systems for vacuum field emission applications, including electrodynamic tethering and electric propulsion systems