Dimitri Galayko

Design, realization and testing of micro-mechanical resonators in thick-film silicon technology with postprocess electrode-to-resonator gap reduction

This paper presents the design, fabrication and testing of high-Q high-frequency lateral-mode clamped–clamped beam micro-resonators driven by parallel-plate electrostatic transducers fabricated in a thick epipoly technology. An innovative approach is employed to reduce an intrinsically high transducer gap value (>3.0 μm) required by the need of 15 μm thick structural layer etching down to 0.2–0.4 μm after the fabrication. This is achieved by employing an electrostatic motor that approaches the actuating and sensing electrodes close to the resonator. The electrode motor is driven with 30 V dc voltage, without any dc current consumption. Two resonators having a resonance frequency of 10 MHz have been fabricated with gap values of 0.2 and 0.4 μm respectively. A comparative analysis of performances of the two resonators is given in the paper.

Microelectromechanical variable-bandwidth if frequency filters with tunable electrostatical coupling spring

This paper describes the theory, design and test of a novel architecture of highly-selective micromechanical filters employing electrostatically coupled resonators with floating or biased coupling electrodes. This original method avoids the use of mechanical coupling springs thus extending the potential of a given process to higher frequencies. It gives also the possibility to implement more complex filter architectures and to tune the coupling factor of resonators. Filters with 2.8 MHz and 10.6 MHz center frequency having tunable relative bandwidths of 0.025-0.17% have been built from pairs of clamped-clamped beam resonators. Special design techniques have been used to reduce parasitic capacitances on the coupling node.

Clamped-Clamped Beam Micro-Mechanical Resonators in Thick-Film Epitaxial Polysilicon Technology

This paper presents design and test results of clampedclamped beam resonators fabricated in thick-film epitaxial polysilicon technology. A new technique is used to achieve a 0.2 μm sensing electrod-to-resonator lateral gap in a structural polysilicon layer of 15 μm thickness. The frequencies of the designed resonators belong to the range of 2.3-16.4 MHz, the measured quality factors are of 450-15500 for different resonance frequencies.

Low-frequency and ultra-wideband MEMS electrostatic vibration energy harvester powering an autonomous wireless temperature sensor node

We report a 1-cm2 ultra-wideband MEMS electrostatic vibration energy harvester (e-VEH) that combines a frequency-up conversion system with a vertical electret layer obtained by corona discharge. At 2.0 grms, the device can harvest more than 1 μW from 59 to 148 Hz, and more than 0.5 μW from 14 to 152 Hz. Thanks to this new device, we demonstrate the self-starting power supply of an energy autonomous temperature sensor node with a data transmission beyond a distance of 10 m at 868 MHz.

Low-Frequency MEMS Electrostatic Vibration Energy Harvester With Corona-Charged Vertical Electrets and Nonlinear Stoppers

This paper reports for the first time a MEMS electrostatic vibration energy harvester (e-VEH) with corona-charged vertical electrets on its electrodes. The bandwidth of the 1-cm2 device is extended in low and high frequencies by nonlinear elastic stoppers. With a bias voltage of 46 V (electret@21 V + DC external source@25 V) between the electrodes, the RMS power of the device reaches 0.89 μW at 33 Hz and 6.6 μW at 428 Hz. The -3dB frequency band including the hysteresis is 223~432 Hz, the one excluding the hysteresis 88~166 Hz. We also demonstrate the charging of a 47 μF capacitor used for powering a wireless and autonomous temperature sensor node with a data transmission beyond 10 m at 868 MHz.

An analytical model of the oscillation period for tri-state inverter based DCO

Tri-state inverter based DCO are emerging as an attractive circuit for the implementation of fully digital PLL. In this paper, we first introduce an analytical expression of the tuned period as a function of design and technology parameters. Then, we propose a sizing methodology for the CMOS implementation of a tri-state inverter based DCO. Finally, we applied this methodology to the design of such a DCO. We achieved an average error of 5.4% for our analytical expression compared to simulation results. In conclusion, we showed that our analytical expression and sizing methodology are directly applicable to the design of tri-state inverter based DCO.

Architecture-level center frequency drift compensation method for micromechanical filters used in IF stages of wireless telecommunication receivers

A prototype of a 433.92 MHZRF receiver using a micro- mechanical resonator as channel-selection filter in the 2nd IF stage has been realized (94.5 kHz center frequency, 20 Hz bandwidth). A novel approach is used for managing the temperature drift of the center frequency of the micro-mechanical filter. Instead of stabilizing the filters center frequency by complex device-level and technological modifications (bias voltage tuning, mechanical or thermal compensation), we modified the architecture of the IF stage in order to continuously adapt the IF frequency to the filters center frequency deviations. This is achieved by periodical real-time measurements of the filters center frequency and by then generating the appropriate second LO frequency. The measurement of the center frequency is achieved by putting the filter in an oscillating closed loop. The measured relative matching error between the 2nd IF frequency and the filters center frequency is better than 0.005%.

Design methods for microelectromechanical bandpass filters

A design method for high-order electro-mechanical filters that makes use of the equivalence between lumped-parameters electrical and mechanical systems is presented. Conditions for existence of the equivalent mechanical system are derived, and electro-statical coupling of micro-mechanical resonators is introduced. The application to the simulation and design of a bandpass filter with finite transmission zeros implemented in a thick-layer epi-poly silicon micro-machining technology is shown.