MEMS-Based Millimeter Front-end for Automotive Radar Applications

Automotive front-end radars are key components in modern vehicles. They are used in automatic cruise control (ACC) for advanced drive-assistance and security functions, including collision-avoidance systems. Automotive safety is being studied intensively both in industry and academia. One of the most serious limitations of high performance radar are beam-forming network systems, due to the complexity and bulkiness arising from the additional circuitry and hardware needed to implement multiple functionalities into the systems. This limitation can, however, be minimized and made cost-effective by capitalizing on the numerous advantages of RF MEMS and WG technologies. To resolve this issue, the present study covers the characterization of SPST and SPNT RF-MEMS switches at 77 GHz, the investigation and fabrication of a Rotman lens at 77 GHz, and the development of the ground work for a 3D monolithically integrated BFN on a single silicon substrate

Intégration d'un amplificateur RF reconfigurable en fréquence

De nos jours la téléphonie sans fil utilise plusieurs fréquences différentes (900 MHz, 1800 MHz, 1900 MHz, 2200 MHz…) ce qui fait que la majorité des téléphones portables actuellement sur le marché proposent de couvrir les différentes bandes de fréquences avec des téléphones tri-bandes ou quadri-bandes, ce qui impose la multiplication des circuits de réception et d’émission radiofréquences afin de traiter chacune de ces fréquences. Une solution envisageable pour réduire l’espace occupé par les amplificateurs RF au sein de la chaîne d’émission-réception est l’utilisation d’amplificateurs RF reconfigurables en fréquence (aussi appelés amplificateurs intelligents). Cette reconfigurabilité en fréquence est rendue possible grâce aux composants issus de la filière MEMS-RF. En effet, le développement de technologies de fabrication comme le micro usinage de surface a permis de réaliser des structures suspendues dont le mouvement mécanique permet de réaliser des fonctions de commutation. L'utilisation de tels composants dans le domaine des hyperfréquences a permis de fabriquer des synthétiseurs d’impédances MEMS qui permettent d’adapter en impédance l’amplificateur RF quelque soit la fréquence d’opération. On se propose d’étudier dans le cadre de ce mémoire les différents types de synthétiseurs d’impédances RF et en particulier les synthétiseurs d’impédances électromécaniques ainsi que les synthétiseurs d’impédances MEMS et leur utilisation dans les amplificateurs reconfigurables

RF MEMS switches : survey and analysis

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 95-97).Microelectromechanical systems known as MEMS, are an enabling technology that describe a field capable of creating very small electromechanical devices with feature sizes on the order of microns, or 10-6 meters. MEMS technology has received considerable attention recently as a way to produce switches. The technology leverages the fabrication instruments, processing and design techniques of the mature integrated circuit (IC) industry. While MEMS technology has shown great successes in producing commercial devices like accelerometers and pressure sensors, the same has not been true for switches. MEMS switches have shown great RF characteristics via low losses and high isolation. However, they possess several important shortcomings. At present, RF MEMS switches have low reliability, limited power handling capabilities, and slow switching times. Nonetheless, MEMS switches are poised to provide advantages over other switching technologies. The goal of this thesis is to understand the limits of their operation and predict their impact in practical applications. To that end, this thesis surveys the present state of the art of MEMS RF switches, identifies the benefits and drawbacks of switches created using this technology, and formulates predictions for the future of MEMS RF switches.by Antoinne Y. Machal-Cajigas.M.Eng

Use of Instabilities in Electrostatic Micro-Electro-Mechanical Systems for Actuation and Sensing

This thesis develops methods to exploit static and dynamic instabilities in electrostatic MEMS to develop new MEMS devices, namely dynamically actuated micro switches and binary micro gas sensors. Models are developed for the devices under consideration where the structures are treated as elastic continua. The electrostatic force is treated as a nonlinear function of displacement derived under the assumption of parallel-plate theorem. The Galerkin method is used to discretize the distributed-parameter models, thus reducing the governing partial differential equations into sets of nonlinear ordinary-differential equations. The shooting method is used to numerically solve those equations to obtain the frequency-response curves of those devices and the Floquet theory is used to investigate their stability. To develop the dynamically actuated micro switches, we investigate the response of microswitches to a combination of DC and AC excitations. We find that dynamically actuated micro switches can realize significant energy savings, up to 60 %, over comparable switches traditionally actuated by pure DC voltage. We devise two dynamic actuation methods: a fixed-frequency method and a shifted-frequency method. While the fixed-frequency method is simpler to implement, the shifted-frequency method can minimize the switching time to the same order as that realized using traditional DC actuation. We also introduce a parameter identification technique to estimate the switch geometrical and material properties, namely thickness, modulus of elasticity, and residual stress. We also develop a new detection technique for micro mass sensors that does not require any readout electronics. We use this method to develop static and dynamic binary mass sensors. The sensors are composed of a cantilever beam connected to a rigid plate at its free end and electrostatically coupled to an electrode underneath it. Two versions of micro mass sensors are presented: static binary mass sensor and dynamic binary mass sensor. Sensitivity analysis shows that the sensitivity of our static mass sensor represents an upper bound for the sensitivity of comparable statically detected inertial mass sensors. It also shows that the dynamic binary mass sensors is three orders of magnitude more sensitive than the static binary mass sensor. We equip our mass sensor with a polymer detector, doped Polyaniline, to realize a formaldehyde vapor sensor and demonstrate its functionality experimentally. We find that while the static binary gas sensor is simpler to realize than the dynamic binary gas sensor, it is more susceptible to external disturbances