Dynamic Mechanical Simulation of Miniature Silicon Membrane during Air Blast for Pressure Measurement

The development of new ultra-fast sensors for pressure air blast monitoring requires taking into account the very short rise time of pressure occurring during explosion. Simulations show here that the dynamic mechanical behavior of membrane-based sensors depends significantly on this rise time when the fundamental mechanical resonant frequency of the membrane is higher than 10 MHz.

Modeling and Validation of Capacitive Type RF MEMS Switches for Low Actuation Voltage and High Isolation

Design objectives in capacitive type radio frequency micro electro mechanical switches (RF-MEMS) are to reduce actuation voltages and to obtain low insertion losses with high isolation. In this study, we report design, modeling and simulation of three new structural configurations using ANSYS to obtain the optimum geometry; further high frequency simulations are performed using HFSS to obtain low insertion losses and high isolation. The designed switches require only 3.9 to 5 V as pull-in voltage for actuation. The mechanical resonant frequency and quality factor are in the range of 6.5 to 8.7 kHz and 1.1 to 1.2, respectively. Switching times for all the designs are 32 to 38 μs at their respective pull-in voltages. Two of the switch designs have insertion loss of less than 0.25 to 0.8 dB at 60 and 50 GHz, and isolation greater than 58 dB for all three designs.

Design of Reliable Analog DMTL Phase Shifter with Improved Performance for Ku Band Applications

<p>An analog phase shifter based on distributed MEMS transmission line (DMTL) is designed for Ku band applications. Traditional RF MEMS phase shifter comprising 6 switches has limited phase shift of 37.75° due to instability region. A new concept of stopper is incorporated to achieve high phase shift. In the present paper, optimisation of the analog phase shifter is done to increase its phase shift upto 88.63°. Phase shift is a strong function of capacitance ratio which is increased from 1.75 to 2.95. The maximum operating voltage and mechanical resonant frequency for the phase shifter are 16 V and 8.3 KHz, respectively. The switching time is calculated to 56 μs. The simulated insertion loss of the phase shifter is -1.75 dB with return loss of -20.49 dB at 17 GHz. The simulated results are verified with analytical modelling which are in close match.</p>

TUNING THE RESONANT FREQUENCIES OF FLEXURE MODE FLEXOELECTRIC PIEZOELECTRIC COMPOSITES

The newly developed flexure mode flexoelectric composites have extremely high direct piezoelectric response around mechanical resonant frequency. Methods of tuning the resonant frequencies of the composites were studied in this paper. The resonant frequencies can be adjusted by changing dimensions of ferroelectric ceramic bars in the composites or by adding an additional mass on the composites. Design of flexure mode composites with multiple resonant frequencies was also studied.

The Effect of High Order Non-Linearities on Sub-Harmonic Excitation With Parallel Plate Capacitive Actuators

Electrostatic actuation of motion is commonly used in resonant MEMS. Drive signal feed-through is undesirable as it masks the detection signal. This paper reports analysis and demonstration of a resonant motion excitation scheme, which uses a combination of a DC bias with a sinusoidal AC voltage, frequency of which is twice of the mechanical resonant frequency. This configuration is experimentally demonstrated to excite a gyroscope with a parallel plate drive capacitor into high amplitude periodic vibrations. The feed-through has a frequency higher than the main motional harmonic and thus can be eliminated by simple low pass filtering. Full nonlinear dynamics along with several higher-order approximations are considered. Analysis of the effect of the approximation order on the frequency response accuracy shows that the complete nonlinear equation should be used for modeling of high amplitude actuation. Two distinct types of frequency responses are examined as functions of driving AC and DC voltages and damping.

Fracture Behavior of Thin Film PZT on Silicon Mems and Membranes

ABSTRACTThis research focuses on identifying the fracture mechanism in thin film silicon membranes and PZT on silicon composite structures under static and dynamic loading conditions. Square silicon membranes with a 3mm side-length and thickness between 1.5 and 3.0μm, with and without 1.5μm of PZT, were pressurized to failure while laser interferometry was used to determine the maximum strain at failure. The strain at fracture of silicon membranes, initiating from the sharp corner radius inside the micromachined cavity, was improved from 0.37% to 0.8% by an isotropic etch of the sharp corner. Fracture of PZT on silicon membranes, tested at the mechanical resonant frequency suggested that fracture initiates in the blanket PZT layers under reversed bending. Etching the PZT from high strain regions along the membrane surface improved the strain at failure of the composite device by 40%.