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22 pages, 9221 KiB

Open AccessArticle

Analysis of Structural Design Variations in MEMS Capacitive Microphones

by Tzu-Huan Peng, Huei-Ju Hsu and Jin H. Huang

Sensors 2025, 25(3), 900; https://doi.org/10.3390/s25030900 - 2 Feb 2025

Cited by 2 | Viewed by 1659

Different microstructures significantly affect the acoustic performance of MEMS capacitive microphones, particularly in key specifications of interest. This paper presents several microstructures, including rib-reinforced backplates, suspended diaphragms, and outer vent holes. Three MEMS microphone designs were implemented to analyze the impact of these microstructures. Equivalent circuit models corresponding to each design were constructed to simulate specifications such as sensitivity, signal-to-noise ratio (SNR), and low corner frequency (LCF), which were validated through experimental measurements. Finite Element Analysis (FEA) was also employed to calculate the acoustic damping of certain microstructures, the mechanical lumped parameters of the diaphragm, and the pre-deformation of the MEMS structure. A compressed air test (CAT) was conducted to evaluate the mechanical reliability of microphone samples. The results of simulations and measurements indicate that rib-reinforced backplates effectively improve microphone reliability, increasing the pass rate in CAT. Compared to fully clamped diaphragms, suspended diaphragms exhibit higher mechanical compliance, which enhances SNR performance but reduces AOP. Outer vent holes can achieve similar functionality to diaphragm vent holes, but their impact on improving AOP requires further design and testing. Full article

(This article belongs to the Collection Next Generation MEMS: Design, Development, and Application)

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18 pages, 4805 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Piezoelectric Micromachined Microphone with High Acoustic Overload Point and with Electrically Controlled Sensitivity

by Libor Rufer, Josué Esteves, Didace Ekeom and Skandar Basrour

Micromachines 2024, 15(7), 879; https://doi.org/10.3390/mi15070879 - 3 Jul 2024

Cited by 1 | Viewed by 4842

Abstract

Currently, the most advanced micromachined microphones on the market are based on a capacitive coupling principle. Capacitive micro-electromechanical-system-based (MEMS) microphones resemble their millimetric counterparts, both in function and in performance. The most advanced MEMS microphones reached a competitive level compared to commonly used measuring microphones in most of the key performance parameters except the acoustic overload point (AOP). In an effort to find a solution for the measurement of high-level acoustic fields, microphones with the piezoelectric coupling principle have been proposed. These novel microphones exploit the piezoelectric effect of a thin layer of aluminum nitride, which is incorporated in their diaphragm structure. In these microphones fabricated with micromachining technology, no fixed electrode is necessary, in contrast to capacitive microphones. This specificity significantly simplifies both the design and the fabrication and opens the door for the improvement of the acoustic overload point, as well as harsh environmental applications. Several variations of piezoelectric structures together with an idea leading to electrically controlled sensitivity of MEMS piezoelectric microphones are discussed in this paper. Full article

(This article belongs to the Special Issue Micromachined Acoustic Transducers for Audio-Frequency Range)

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13 pages, 14374 KiB

Open AccessArticle

The Performance Characterization and Optimization of Fiber-Optic Acoustic Pressure Sensors Based on the MOEMS Sensitized Structure

by Ruling Zhou, Chenggang Guan, Hui Lv, Shasha Li, Puchu Lv, Haixin Qin, Wenxiu Chu, Yikai Zhou, Yihao Zhang and Xiaoqiang Li

Sensors 2023, 23(19), 8300; https://doi.org/10.3390/s23198300 - 7 Oct 2023

Cited by 4 | Viewed by 1863

Abstract

In order to investigate the factors affecting the acoustic performance of the extrinsic Fabry–Perot interferometer (EFPI) fiber-optic acoustic pressure sensor and to effectively improve its detection capability, this paper enhances the sensor’s detection sensitivity by adding more sensitized rings to its acoustic pressure-sensitive film. Furthermore, a novel real-time coupled acoustic test method is proposed to simultaneously monitor the changes in the spectral and acoustic metrics of the sensor to characterize its overall performance. Finally, an EFPI-type fiber-optic acoustic pressure sensor was developed based on the Micro-Optical Electro-Mechanical System (MOEMS). The acoustic tests indicate that the optimized fiber-optic acoustic pressure sensor has a sensitivity as high as 2253.2 mV/Pa, and the acoustic overload point (AOP) and signal-to-noise ratios (SNRs) can reach 108.85 dB SPL and 79.22 dB, respectively. These results show that the sensor produced through performance characterization experiments and subsequent optimization has a very high acoustic performance index, which provides a scientific theoretical basis for improving the overall performance of the sensor and will have broad application prospects in the field of acoustic detection. Full article

(This article belongs to the Special Issue Advances in the Design and Application of Optical Fiber Sensors)

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10 pages, 3010 KiB

Open AccessArticle

Multi-Channel Long-Distance Audio Transmission System Using Power-over-Fiber Technology

by Can Guo, Chenggang Guan, Hui Lv, Shiyi Chai and Hao Chen

Photonics 2023, 10(5), 521; https://doi.org/10.3390/photonics10050521 - 1 May 2023

Cited by 8 | Viewed by 3046

Abstract

To establish stable communication networks in harsh environments where power supply is difficult, such as coal mines and underwater, we propose an effective scheme for co-transmission of analog audio signals and energy. By leveraging the advantages of optical fibers, such as corrosion resistance and strong resistance to electromagnetic interference, the scheme uses a 1550 nm laser beam as the carrier for analog audio signal propagation, which is then converted to electrical energy through a custom InGaAs/InP photovoltaic power converter (PPC) for energy supply and information transfer without an external power supply after a 25 km fiber transmission. In the experiment, with 160 mW of optical power injection, the scheme not only provides 4 mW of electrical power, but also transmits an analog signal with an acoustic overload point (AOP) of 105 dBSPL and a signal-to-noise ratio (SNR) of 50 dB. In addition, the system employs wavelength division multiplexing (WDM) technology to transform from single-channel to multi-channel communication on a single independent fiber, enabling the arraying of receiving terminals. The passive arrayed terminals make the multi-channel long-distance audio transmission system using power-over-fiber (PoF) technology a superior choice for establishing a stable communication network in harsh environments. Full article

(This article belongs to the Special Issue Latest Papers Related to OWPT 2023 on the Topics of Devices, Components and Systems)

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