Papers by Maher Bakri-Kassem
2015 10th International Symposium on Mechatronics and its Applications (ISMA), 2015
An efficient method for energy harvesting through MEMS based devices, driven by ambient vibration... more An efficient method for energy harvesting through MEMS based devices, driven by ambient vibrations is presented. This particular method relies on the utilization of time varying magnetic fields to induce electromotive forces which in turn drive current through coils fabricated on a substrate. This allows for the conversion of energy contained within naturally occurring vibrations to usable forms of electrical energy. The process primarily hinges on fundamental principals in electromagnetic theory related to induction. Here we propose a miniaturized MEMS energy harvester comprising of coils on a substrate measuring mere mm in dimension, two permanent magnets and a shuttle that is connected to flexible beams. The relationship between number of coil turns on the substrate, induced voltage and vibrational motion were studied and a proposed model was devised.
2017 18th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2017
This paper proposes a nonlinear model and reports the current-voltage (I–V) characteristics of a ... more This paper proposes a nonlinear model and reports the current-voltage (I–V) characteristics of a thermally driven V-shaped MEMS actuator with a folded spring (FS) reference beam. The nonlinear lumped element model is developed using circuit elements with temperature-dependent material properties. In addition, it is shown experimentally that the Joule heating occurring across the polysilicon layer is a nonlinear phenomenon. The equivalent resistance of the polysilicon layer is therefore a function of temperature and thus the resulting nonlinear I–V characteristics is obtained. The experimental I–V data are used to find the resistance-voltage data which are then fed into the model. The actuator with the FS is also compared to the actuator without it in terms of the I–V characteristics, power consumption, experimental tip displacement, and simulated temperature.
2016 IEEE 59th International Midwest Symposium on Circuits and Systems (MWSCAS), 2016
This paper analyzes a V-shaped thermal MEMS actuator for RF MEMS applications which has been fabr... more This paper analyzes a V-shaped thermal MEMS actuator for RF MEMS applications which has been fabricated using MetalMUMPs process from MEMSCAP Inc. and can withstand maximum actuation voltage of 15 V corresponding to 41.56 μm. The analysis is made through characterization of thin film polysilicon which is the source of producing heat in the thermal MEMS actuator. In addition, a lumped-element model with circuit elements is utilized to find the temperature in the polysilicon layer. The current-voltage characteristics of the thermal MEMS actuator is then simulated and compared against experimental data. The results show a very good agreement between experimental and simulated current-voltage characteristic curves. The developed model helps to design and fabricate V-shaped thermal MEMS actuators with high durability against higher actuation voltages which will enable them to exhibit higher displacements.
2021 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers), 2021
Fabrication recipes usually are designed to eliminate residual stress, while majority of electros... more Fabrication recipes usually are designed to eliminate residual stress, while majority of electrostatic models considers fringing field to be negligible. The work presented here tries to make a benefit of these two to make a new design for an AFM probe. The curvature caused by residual stress was experimentally exported from profilometer into COMSOL to show the effect of curvature on the probe's static behavior (under DC voltage) at two different beam lengths. The results show that the curvature could turn the forcing on the probe from repulsive to attractive, which is analogues to results in existing literature.
A novel slotted multi-step RF MEMS-CMOS parallel plate varactor with a tuning range of 89%, that ... more A novel slotted multi-step RF MEMS-CMOS parallel plate varactor with a tuning range of 89%, that works as a digital varactor, is designed and simulated. The designed varactor is simulated using ANSYS to order to obtain the curved 3d shape and the collapse voltages however HFSS and ADS were utilized to build the equivalent circuit model. The designed varactor exhibits a minimum capacitance of 1 pF and maximum capacitance of 2 pF.
Journal of Micromechanics and Microengineering, 2020
This work reports on the design, fabrication and characterization of compact digital RF MEMS capa... more This work reports on the design, fabrication and characterization of compact digital RF MEMS capacitors and phase shifters that are built in the back end of line (BEOL) of CMOS 0.35 µm technology. The devices are micromachined using a maskless post-processing sequence with cryogenic cooling on to control the out-of-plane warping of the metal-oxide structural layers. The implemented vertical electrostatic actuation in the developed post process allows the realization of highly compact designs of both devices, and an operating voltage of the devices is stay below 70 V. The 4-bit capacitors provide a measured tuning ratio close to 10:1 which corresponds to 0.15 pF to 1.2 pF over the frequency range 3–10 GHz. The overall footprint of the digital capacitor is 0.6 mm × 0.9 mm. The measured quality factor after de-embedding the losses due to the RF probing pads is up to 120. The measurement of the 4-bit phase shifters reveals low insertion loss <3 dB at 20 GHz along with low variation of the insertion loss <1 dB up to the same frequency. The measured phase shift is 150 at 20 GHz. The overall footprint of the 4-bit phase shifter is around 1 mm × 1 mm.
Journal of Micromechanics and Microengineering, 2018
In this paper, we propose a new dynamic model to describe the nonlinear characteristics of a V-sh... more In this paper, we propose a new dynamic model to describe the nonlinear characteristics of a V-shaped (chevron) metallic-based thermally driven MEMS actuator. We developed two models for the thermal actuator with two configurations. The first MEMS configuration has a small tip connected to the shuttle, while the second configuration has a folded spring and a wide beam attached to the shuttle. A detailed finite element model (FEM) and a lumped element model (LEM) are proposed for each configuration to completely characterize the electro-thermal and thermo-mechanical behaviors. The nonlinear resistivity of the polysilicon layer is extracted from the measured current–voltage (I–V) characteristics of the actuator and the simulated corresponding temperatures in the FEM model, knowing the resistivity of the polysilicon at room temperature from the manufacture's handbook. Both developed models include the nonlinear temperature-dependent material properties. Numerical simulations in comparison with experimental data using a dedicated MEMS test apparatus verify the accuracy of the proposed LEM model to represent the complex dynamics of the thermal MEMS actuator. The LEM and FEM simulation results show an accuracy ranging from a maximum of 13% error down to a minimum of 1.4% error. The actuator with the lower thermal load to air that includes a folded spring (FS), also known as high surface area actuator is compared to the actuator without FS, also known as low surface area actuator, in terms of the I–V characteristics, power consumption, and experimental static and dynamic responses of the tip displacement.
Journal of Microelectromechanical Systems, 2019
This paper presents a multiphysics analysis of thermally actuated RF MEMS switches for use in pow... more This paper presents a multiphysics analysis of thermally actuated RF MEMS switches for use in power limiter applications. RF MEMS switches can self-actuate when operating under high RF power levels. The level of power at which the switch actuates, can be varied by controlling the applied dc actuation voltage. MEMS switches are, therefore, proposed for use in power limiter applications. The objective of the multiphysics analysis presented in this paper is to combine thermal analysis, with mechanical analysis and RF analysis to derive a relationship between the RF power needed for self-actuation and the dc voltage applied to the thermal actuator. A thermally actuated MEMS switch is fabricated and tested. It is used as a test bed for demonstrating the proposed multiphysics analysis. The experimental results obtained for this switch confirm the approach used to construct a multiphysics analysis for thermally actuated MEMS switches. The results obtained also demonstrate that thermally actuated MEMS switches offer improved device sensitivity, when used in power limiter applications, in comparison with their counterparts electrostatically actuated MEMS switches. [2018-0106] Index Terms-RF-MEMS, thermally actuated switch, high power application, power limiter, frequency dependent power limiter.
Journal of Micromechanics and Microengineering, 2018
2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2016
In this paper, a new electro-thermal dynamic model for V-shaped thermal micro-electromechanical a... more In this paper, a new electro-thermal dynamic model for V-shaped thermal micro-electromechanical actuators is proposed. The experimental observation of the dynamic voltage-displacement relationship for a thermal micro-actuator shows a complex characteristic indicating the simultaneous presence of electrical/thermal energy storage and mechanical energy dissipation mechanisms. To completely characterize these mechanisms and yet have a simple representation for control, a new electro-thermal model using the lumped elements concept of dynamic systems is developed. This model represents the electrical-thermal energy conversion phenomenon by an equivalent resistive and capacitive circuit leading to a mathematically well-posed linear differential equation. The Lumped-Element (LE) electro-thermal dynamic model accounts for both conduction and convection losses. Experimental results along with numerical simulations with MATLAB and ANSYS are used to verify the accuracy of the proposed modeling approaches.
2015 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC), 2015
A high power nickel based electroplated 4-bit RF MEMS capacitors bank is designed, fabricated and... more A high power nickel based electroplated 4-bit RF MEMS capacitors bank is designed, fabricated and tested. The proposed design is capable to handle high power up to 30 Watts and utilizes co-planar transmission lines that use eight latching SPDT RF MEMS switches. The capacitors bank design is made of 4 cascaded bit units where every bit has two different paths, the first path is a conventional CPW while the second path is a CPW loaded with an inter-digitated capacitor. The measured maximum capacitance when all loaded CPW are engaged in almost 20 pF. The minimum measured capacitance however is 0.7 pF, at 1 GHz. The measured tuning ratio is around 28 times. The capacitors bank is built on high resistive silicon substrate using MetalMUMPs process.
Canadian Journal of Electrical and Computer Engineering, 2006
Surface micromachining technology implemented by the PolyMUMPs process is used to fabricate on-ch... more Surface micromachining technology implemented by the PolyMUMPs process is used to fabricate on-chip RF microelectromechanical systems (MEMS) components. Parasitic effects due to coupling to the low-resistivity silicon substrate are eliminated by the introduction of a customized wet etching post-processing technique. The maskless post-processing technique consists of a wet etching step using open windows through the nitride layer that covers the silicon substrate. The etchant used to etch the silicon substrate is tetramethylammonium hydroxide (TMAH). The best etching recipe that meets the PolyMUMPs requirements is determined. A variety of RF passive components are designed, fabricated, and tested. A comparison between the measurement results both before and after application of the proposed post-processing is presented. La technologie de micro-usinage de surface implémentée par le processus PolyMUMPs est utilisée pour fabriquer des composantesà systèmes micro-électro-mécaniques (MEMS) RF on chip. Les effets parasites provoqués par le couplage au substrat de silicium qui possède une faible résistance sontéliminés par l'introduction d'une technique de post-traitement de gravure humide personnalisée. La technique sans masque de post-traitement consiste en une gravure humide utilisant une fenêtre ouverteà travers la couche de nitrure qui couvre le substrat de silicium. L'hydroxyde d'ammonium tétraméthylique (TMAH) aété utilisé pour la gravure du substrat de silicium. La meilleure méthode de gravure qui rencontre les conditions du processus PolyMUMPs est déterminée. Une variété de composantes passives RF sont conçues, fabriquées et testées. La comparaison entre les résultats obtenus avant et après l'application du post-traitement proposé est présentée.
IEEE Transactions on Antennas and Propagation, 2014
SPIE Proceedings, 2004
This paper addresses the use of RF MEMS devices in wireless and satellite communication systems. ... more This paper addresses the use of RF MEMS devices in wireless and satellite communication systems. It describes the MEMS actuators typically needed for such devices. Novel configurations are presented for MEMS variable capacitors, MEMS tunable inductors and RF MEMS mutiport switches. The tuning range of the variable capacitor was measured and found to be 280%, which far exceeds that of the traditional parallel plate MEMS variable capacitors. The MEMS tunable inductor is realized using MEMS fixed inductors, capacitors ...
A novel CPW based phase shifter that relies on automatic collapse of capacitive switches is desig... more A novel CPW based phase shifter that relies on automatic collapse of capacitive switches is designed, fabricated and tested. The novel design of the phase shifter is due to a novel CPW topology and automatic collapse mechanical design that is designed to operate at several and gradual collapse voltages. The novelty of the CPW has been achieved through the corrugated grounds to create a slow wave transmission line. The resulted compact CPW will have an effective electrical length that is physically equivalent to a relatively longer conventional CPW. The automatic collapse of the designed capacitive switches comes through deferent lengths of the beams that are carrying those capacitive switches. The worst measured insertion loss and return loss are 1.7 dB and 13 dB, respectively, at 30 GHz with a phase shift of almost 106 degrees. The phase shifter is built on alumina substrate of gold material using UWMEMS process.
ABSTRACT A novel latching RF MEMS Switch is proposed. The single pole single throw (SPST) switch ... more ABSTRACT A novel latching RF MEMS Switch is proposed. The single pole single throw (SPST) switch is built on a 20 μm thick nickel layer eliminating any potential warping due to thermal mismatch. The switch exhibits a 40 μm displacement with a power consumption of 175 mW at 80K under vacuum. The measurement was done over ambient and vacuum and over wide range of temperatures from 300 K to 80 K. The switch demonstrates an excellent RF performance up to 26 GHz.
2013 8th International Conference on Design & Technology of Integrated Systems in Nanoscale Era (DTIS), 2013
ABSTRACT A frequency reconfigurable LNA is designed using novel tunable RF-MEMS varactors. The de... more ABSTRACT A frequency reconfigurable LNA is designed using novel tunable RF-MEMS varactors. The designed MEMS varactor can be fabricated and integrated in 0.35μm CMOS technology from Taiwan Semiconductor Manufacturing Company (TSMC). The frequency of operation of the LNA varies from 2.7 GHz to 3.1 GHz by tuning the capacitance of the MEMS varactor. The MEMS varactor is simulated in ANSYS and the obtained results are included in the LNA design. The LNA performance is simulated and the results are discussed.
Proceedings International Conference on MEMS, NANO and Smart Systems
2008 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, 2008
A maskless post-processing technique for CMOS chips is developed that enables the fabrication of ... more A maskless post-processing technique for CMOS chips is developed that enables the fabrication of RF MEMS parallel-plate capacitors with a high quality factor and a very compact size. Simulations and measured results are presented for several MEMS/CMOS capacitors. A 2-pole coupled line tunable bandpass filter with a center frequency of 9.5 GHz is designed, fabricated and tested. A tuning range of 17% is achieved using integrated variable MEMS/CMOS capacitors with a quality factor exceeding 20. The tunable filter occupies a chip area of 1.2 × 2.1 mm 2. I.
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Papers by Maher Bakri-Kassem