P31 - Optimization of Harmonic Distortions for Electrostatic MEMS Push-Pull NED-Microspeakers
- Event
- iCCC2024 - iCampµs Cottbus Conference
2024-05-14 - 2024-05-16
Cottbus - Band
- Poster
- Chapter
- Aktorik
- Author(s)
- F. Wall, H. Schenk - Fraunhofer IPMS, Dresden , H. Schenk, A. Melnikov, L. Ehrig, B. Kaiser - Bosch Sensortec GmbH, Dresden
- Pages
- 218 - 221
- DOI
- 10.5162/iCCC2024/P31
- ISBN
- 978-3-910600-00-3
- Price
- free
Abstract
Electrostatic actuators realizing the push-pull principle enable a MEMS-based microspeaker with the perspective of a power efficient CMOS-compatible and RoHs compliant sound transducer for in-ear applications. Each clamped-free actuator is placed within its own cavity. A periodic oscillation of an actuator ensemble generates the sound signal. Combining a differential drive with two independent actuator layers ideally allows an actuation without even harmonic distortions. Further, various combinations of signal and bias voltages result in the same sound pressure level (Iso-SPL), leading to the question, how to choose the working point from the perspective of high fidelity. Based on a previous distortion analysis of the voltage scaling, a reduced order model is scaled to reproduce not only distortions but also the experimentally observed pressure signal. Further, Iso-SPL working points are evaluated numerically. Close to the pull-in voltage, above which no stable equilibrium between elastic and electrostatic forces exist, harmonic distortions become from a product point of view unacceptable. Distortions can be minimized for voltage combinations with the same fundamental response, by optimizing the distance not only towards the DC induced pull-in but also towards the quasi-static AC pull-in.