Analytical modeling of plus shape MEMS paddle bridge resonant sensor for weak magnetic fields (original) (raw)
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2011 Saudi International Electronics, Communications and Photonics Conference (SIECPC), 2011
A novel design of micro paddle bridge resonant magnetic field sensor based on electrostatic actuation and capacitive detection technique is characterized and simulated using CoventorWare. The sensor consists of Aluminum plus shape paddle bridge resonator with two proof mass arms, driving electrodes, sensing electrode and silicon substrate. Working in a resonant condition, the sensor's vibration amplitude is converted into the sensing capacitance change, which reflects the outside magnetic flux-density. Based on the simulation, the key structure parameters are optimized and the resonant frequency is estimated. The results of the device are in accordance with the theoretical values of the designed model. The results indicate its sensitivity 0.252 pA/μT, when operating at 10% of critical damping. The sensitivity and resolution can be enhanced through vacuum packaging.
Sensors and Actuators A-physical, 2011
A resonant magnetic field microsensor based on Microelectromechanical Systems (MEMS) technology including a piezoresistive detection system has been designed, fabricated, and characterized. The mechanical design for the microsensor includes a symmetrical resonant structure integrated into a seesaw rectangular loop (700 μm × 450 μm) of 5 μm thick silicon beams. An analytical model for estimating the first resonant frequency and deflections of the resonant structure by means of Rayleigh and Macaulay's methods is developed. The microsensor exploits the Lorentz force and presents a linear response in the weak magnetic field range (40–2000 μT). It has a resonant frequency of 22.99 kHz, a sensitivity of 1.94 V T−1, a quality factor of 96.6 at atmospheric pressure, and a resolution close to 43 nT for a frequency difference of 1 Hz. In addition, the microsensor has a compact structure, requires simple signal processing, has low power consumption (16 mW), as well as an uncomplicated fabrication process. This microsensor could be useful in applications such as the automotive sector, the telecommunications industry, in consumer electronic products, and in some medical applications.
Resonant Magnetic Field Sensors Based On MEMS Technology
Sensors, 2009
Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration. OPEN ACCESS Sensors 2009, 9 7786 Keywords: Lorentz force; magnetic field sensors; Microelectromechanical Systems (MEMS); resonant structures
Journal of Microelectromechanical Systems, 2017
This paper presents the investigation of two different capacitive feedthrough current elimination methods with an analysis of the effect of the capacitive feedthrough current on the resonance characteristics of electrostatically actuated and sensed resonant MEMS sensors. Electrostatically actuated and sensed resonators have various applications, such as accelerometers, gyroscopes, mass sensors, and temperature sensors. In most of these applications, as sensitivity increases, gain decreases. The capacitive feedthrough current between the drive and sense electrodes disturbs the resonance characteristics of the resonator, especially when the gain is rather small. In order to eliminate the dominating feedthrough current in such cases, two methods were proposed. In the first method, differential input signals were applied to two separate resonators, one active and one passive, sharing the same sense electrode. Although this method seems to be easily applicable to all types of resonators, this study has shown that mismatches between the resonator pair prevent perfect elimination of the feedthrough current. In the second method, a novel lateral electrostatic resonator with differential sense electrodes was designed and fabricated to eliminate the feedthrough current. Measurements showed that the feedthrough effect was successfully eliminated and 27 times higher SNR dB was achieved with this method. Moreover, it was successfully demonstrated that any mismatch can be compensated by a simple resistive adjustment. [2016-0288] Index Terms-Differential reading, feedthrough current, MEMS, resonator. I. INTRODUCTION R ESONATING structures are widely used in MEMS based sensors, such as accelerometers and gyroscopes. Recently, mass and temperature sensors that depend on resonance frequency shifts have become popular [1]-[4]. Especially resonators for bio-mass detection promise breakthrough products [5]. Performance of such sensors depends highly on the precise determination of the resonance frequency.
2017 IEEE 30th International Conference on Micro Electro Mechanical Systems (MEMS), 2017
This paper reports the demonstration of an array of piezoelectric/magnetostrictive micro electromechanical system (MEMS) magnetic resonant sensors (PM-MRS) for multi-axis magnetic field (H-field) detection. An array of 43 MHz aluminum nitride (AlN) piezoelectric resonators vibrating along different in-plane directions (θ) but coated with a magnetostrictive layer (Fe 65.6 Co 9.4 B 25) with the same easy axis (EZ) exhibit unique mechanical/ electrical responses as a function of the applied H-field and its direction, enabling a high resolution multi-axis H-field detection. The sensor design yields resonators with a high quality factor (Q ~ 1500) and electromechanical coupling coefficient (k t 2 ~ 2%)-the highest value ever reported for an AlN PM-MRS. This sensor system paves the way for low power magnetometers that enables single-chip multi-axis H-field detection.
Enhancing the Linear Range of MEMS Resonators for Sensing Applications
IEEE Sensors Journal, 2000
In this paper, mechanical and electrical nonlinearities of MEMS resonators are discussed and their influence on the resonant sensing performance is analyzed. An "L-shaped" resonator is proposed in order to reduce the influence of the nonlinear mechanical term on the global response with respect to the more standard clamped-clamped ("I-shaped") resonator. An extended linear behavior of the "L-shaped" resonator is analytically demonstrated and validated through experimental results. As a consequence, the proposed resonator can be driven to larger vibration amplitudes through higher actuation voltages, allowing better signal-to-noise ratio (SNR).
Optical and capacitive characterization of MEMS magnetic resonator
IEICE Electronics Express, 2016
In this paper a Lorentz force driven Micro ELectro Mechanical Sytems (MEMS) resonator fabricated on PolyMUMP process with optical and capacitive sensing is presented. The resonator is designed by combining the two poly layers which result in an increase in the thickness of the resonator. Lorentz force generates lateral displacements at low driving voltages which are proportional to the magnetic field and the input current. A displacement of more than 9.8 µm was achieved with a magnetic field of 0.12 T and a driving current of 27 mA. Magnetic sensitivity of 1.41 V/T in air was experimentally measured using permanent magnets and capacitive sensing circuitry. Optical results demonstrate the sensitivity values between 0.090 µm/mT and 0.074 µm/mT.
Resonant mechanical magnetic sensor in standard CMOS
IEEE Electron Device Letters, 2000
A novel micromechanical magnetic sensor has been built and tested. The field is detected by measuring the vibration amplitude of a mechanical Lorentz force oscillator. This device is made from a standard 2-m CMOS fabrication process with a post-processing etch step to undercut and release the sensor. When operated at the resonant frequency of the mechanical system, a sensitivity of 20 V/G was measured.
An A/D interface for resonant piezoresistive MEMS sensor
2004 IEEE International Symposium on Industrial Electronics, 2004
This paper introduces a original architecture to measure and convert into digital data the oscillations of a resonant beam. An electromechanical CMOS magnetic field sensor is considered here for the purpose of a case study. The proposed architecture is based on the counting of periods at an oscillator output, which frequency depends on the deformation of the mechanical structure. In order to cancel drifts, the architecture implements a differential measure by counting both up and down within a mechanical vibration period, using the actuation signal for synchronization. Simulation results demonstrate that high resolution can be achieved with acceptable integration time. Such a signal processing architecture is particularly suitable for low-cost CMOS mechanical structures.