ABSTRACT
Capacitive micromachined ultrasonic transducers (CMUT) are MEMS-based transducers with advantages over conventional ultrasonic transducers, such as their small size, the ease of integration with semiconductor electronics, and batch fabrication. In this study, the effect of different membrane topologies on the displacement, resonant frequency, and output pressure of the CMUT membrane is investigated in the transmission mode in an air environment. A novel structural-support feature, the rocker stem, is introduced, where the membrane is weakly held to the substrate in order to minimize mechanical constraints. Four different CMUT topologies are designed and assessed to analyze the impacts of topological variations. A new CMUT array configuration is also designed to provide an approach for maximizing CMUT density. This study aims to contribute to efficient CMUT design and the determination of optimum structural parameters for portable applications in air.
ABSTRACT
This paper presents the design and simulation of a mass sensitive Lamb wave microsensor with CMOS technology provided by SilTerra. In this work, the effects of the metalization ratio variation on the transmission gain, total harmonic distortion (THD), and two different resonant modes (around 66 MHz and 86 MHz) are shown. It has been found that the metalization ratio can be adjusted in order to obtain a compromise between transmission gain and sensitivity, depending on the design criteria. By adding a Si3N4 layer on top of the device, a five-fold improvement in transmission gain is reached. It was also shown that the transmission of the input differential IDT configuration is 20% more efficient than a single terminal. With this combination, the mass sensitivity is about 114 [cm2/gr].
Subject(s)
Acoustics , Computer Simulation , ElectrodesABSTRACT
In this article, a methodology for increasing the displacement of the membrane in nonlinear transducers is presented. This methodology that relies on pulse shaping is based on the frequency modulation of the excitation signal which in turn results in an amplitude modulation of the displacement of the resonator. The benefits of pulse shaping include the increase of the displacement of the membrane of the resonator, the ability to leverage two mechanisms to dynamically tune the resonant frequency of the device and a relative control of the decay time of the resonator. These properties have been verified using simulations and experimental results. The experimental results are performed using two nonlinear resonators with a frequency of 3.9 and 7.9 kHz. With a constant amplitude of the excitation voltage, experimental results show that the use of pulse shaping allows a velocity increase of the membrane of a piezoelectric microelectromechanical systems (MEMS) resonator of up to 191% for a softening type resonator (STR), and 348% for a hardening type resonator (HTR). The frequency tuning mechanism allowed the operation of the STR and of the HTR over a bandwidth of 280 and 115 Hz, respectively, while providing higher velocity than with the non-optimized excitation signal. The resulting pulse shaping methodology can be applied to other nonlinear resonators as shown using simulation and experimental results. Therefore, this work should lead to an increase of the use of nonlinear resonators for various applications.
Subject(s)
Micro-Electrical-Mechanical Systems , Computer Simulation , TransducersABSTRACT
This paper proposes a system in package (SiP) for ultrasonic ranging composed of a 4 × 8 matrix of piezoelectric micromachined ultrasonic transducers (PMUT) and an interface integrated circuit (IC). The PMUT matrix is fabricated using the PiezoMUMPS process and the IC is implemented in the AMS 0.35 µm technology. Simulation results for the PMUT are compared to the measurement results, and an equivalent circuit has been derived to allow a better approximation of the load of the PMUT on the IC. The control circuit is composed of a high-voltage pulser to drive the PMUT for transmission and of a transimpedance amplifier to amplify the received echo. The working frequency of the system is 1.5 MHz.
