Micromachines

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13 pages, 5919 KiB

Open AccessArticle

Parametric Synthesis of Single-Stage Lattice-Type Acoustic Wave Filters and Extended Multi-Stage Design

by Wei-Hsien Tseng and Ruey-Beei Wu

Micromachines 2024, 15(9), 1075; https://doi.org/10.3390/mi15091075 - 26 Aug 2024

Viewed by 600

This study proposes a single-stage lattice-type acoustic filter using an analytical solution method for either a narrow passband filter or a wider passband filter using two kinds of parameter assignments in the Butterworth–Van Dyke (BVD) model. To achieve the goal of a large [...] Read more.

This study proposes a single-stage lattice-type acoustic filter using an analytical solution method for either a narrow passband filter or a wider passband filter using two kinds of parameter assignments in the Butterworth–Van Dyke (BVD) model. To achieve the goal of a large bandwidth or high return loss, two first-order all-pass conditions are used. For multi-stage lattice-type filters, the cost function is defined and design parameters are extracted by using pattern search, while the initial values are provided through single-stage design to shorten optimization time and allow convergence to a better solution. This method provides the S-parameter frequency response for the filter on the YX 42° cut angle of lithium tantalate (electromechanical coupling coefficient of about 6%) that can meet the system specifications as much as possible. Finally, the three-stage lattice-type was applied to various 5G bands with a fractional bandwidth of 2–5%, resulting in a passband return loss of 10 dB and an out-of-band rejection of 40 dB or more. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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14 pages, 3908 KiB

Open AccessArticle

Experimental and Theoretical Analysis of Rayleigh and Leaky-Sezawa Waves Propagating in ZnO/Fused Silica Substrates

by Cinzia Caliendo, Massimiliano Benetti, Domenico Cannatà, Farouk Laidoudi and Gaetana Petrone

Micromachines 2024, 15(8), 974; https://doi.org/10.3390/mi15080974 - 29 Jul 2024

Cited by 1 | Viewed by 754

Abstract

Piezoelectric c-axis oriented zinc oxide (ZnO) thin films, from 1.8 up to 6.6 µm thick, have been grown by the radio frequency magnetron sputtering technique onto fused silica substrates. A delay line consisting of two interdigital transducers (IDTs) with wavelength λ = 80 [...] Read more.

Piezoelectric c-axis oriented zinc oxide (ZnO) thin films, from 1.8 up to 6.6 µm thick, have been grown by the radio frequency magnetron sputtering technique onto fused silica substrates. A delay line consisting of two interdigital transducers (IDTs) with wavelength λ = 80 µm was photolithographically implemented onto the surface of the ZnO layers. Due to the IDTs’ split-finger configuration and metallization ratio (0.5), the propagation of the fundamental, third, and ninth harmonic Rayleigh waves is excited; also, three leaky surface acoustic waves (SAWs) were detected travelling at a velocity close to that of the longitudinal bulk wave in SiO₂. The acoustic waves’ propagation in ZnO/fused silica was simulated by using the 2D finite-element method (FEM) technique to identify the nature of the experimentally detected waves. It turned out that, in addition to the fundamental and harmonic Rayleigh waves, high-frequency leaky surface waves are also excited by the harmonic wavelengths; such modes are identified as Sezawa waves under the cut-off, hereafter named leaky Sezawa (LS). The velocities of all the modes was found to be in good agreement with the theoretically calculated values. The existence of a low-loss region in the attenuation vs. layer thickness curve for the Sezawa wave below the cut-off was theoretically predicted and experimentally assessed. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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12 pages, 5410 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Rational Design of a Surface Acoustic Wave Device for Wearable Body Temperature Monitoring

by Yudi Xie, Minglong Deng, Jinkai Chen, Yue Duan, Jikai Zhang, Danyu Mu, Shurong Dong, Jikui Luo, Hao Jin and Shoji Kakio

Micromachines 2024, 15(5), 555; https://doi.org/10.3390/mi15050555 - 23 Apr 2024

Viewed by 1538

Abstract

Continuous monitoring of vital signs based on advanced sensing technologies has attracted extensive attention due to the ravages of COVID-19. A maintenance-free and low-cost passive wireless sensing system based on surface acoustic wave (SAW) device can be used to continuously monitor temperature. However, [...] Read more.

Continuous monitoring of vital signs based on advanced sensing technologies has attracted extensive attention due to the ravages of COVID-19. A maintenance-free and low-cost passive wireless sensing system based on surface acoustic wave (SAW) device can be used to continuously monitor temperature. However, the current SAW-based passive sensing system is mostly designed at a low frequency around 433 MHz, which leads to the relatively large size of SAW devices and antenna, hindering their application in wearable devices. In this paper, SAW devices with a resonant frequency distributed in the 870 MHz to 960 MHz range are rationally designed and fabricated. Based on the finite-element method (FEM) and coupling-of-modes (COM) model, the device parameters, including interdigital transducer (IDT) pairs, aperture size, and reflector pairs, are systematically optimized, and the theoretical and experimental results show high consistency. Finally, SAW temperature sensors with a quality factor greater than 2200 are obtained for real-time temperature monitoring ranging from 20 to 50 °C. Benefitting from the higher operating frequency, the size of the sensing system can be reduced for human body temperature monitoring, showing its potential to be used as a wearable monitoring device in the future. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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11 pages, 2690 KiB

Open AccessArticle

Ultra-High Frequency Surface Acoustic Wave Sensors for Temperature Detection

by Qi Dong, Qutong Yang, Xiaoyang Liu, Shenghe Hu, Wenzhe Nie, Zhao Jiang, Xiaoming Fan, Jingting Luo, Ran Tao and Chen Fu

Micromachines 2024, 15(1), 135; https://doi.org/10.3390/mi15010135 - 15 Jan 2024

Viewed by 1618

Abstract

Highly sensitive surface acoustic wave (SAW) sensors have recently been recognized as a promising tool for various industrial and medical applications. However, existing SAW sensors generally suffer from a complex design, large size, and poor robustness. In this paper, we develop a simple [...] Read more.

Highly sensitive surface acoustic wave (SAW) sensors have recently been recognized as a promising tool for various industrial and medical applications. However, existing SAW sensors generally suffer from a complex design, large size, and poor robustness. In this paper, we develop a simple and stable delay line ultra-high frequency (UHF) SAW sensor for highly sensitive detection of temperature. A Z-shaped delay line is specially designed on the piezoelectric substrate to improve the sensitivity and reduce the substrate size. Herein, the optimum design parameters of extremely short-pitch interdigital transducers (IDTs) are given by numerical simulations. The extremely short pitch gives the SAW sensor ultra-high operating frequency and consequently ultra-high sensitivity. Several experiments are conducted to demonstrate that the sensitivity of the Z-shaped SAW delay line sensor can reach up to 116.685°/°C for temperature detection. The results show that the sensor is an attractive alternative to current SAW sensing platforms in many applications. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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17 pages, 7785 KiB

Open AccessArticle

Design for SAW Antenna-Plexers with Improved Matching Inductance Circuits

by Min-Yuan Yang and Ruey-Beei Wu

Micromachines 2024, 15(1), 89; https://doi.org/10.3390/mi15010089 - 30 Dec 2023

Cited by 1 | Viewed by 1699

Abstract

This study designs antenna-plexers, including a surface acoustic wave (SAW) extractor and an upper- and mid-high band (UHB + MHB) diplexer, for LTE 4G and 5G bands using carrier aggregation. The SAW extractor combines a bandpass filter (BPF) and a band-stop filter (BSF) [...] Read more.

This study designs antenna-plexers, including a surface acoustic wave (SAW) extractor and an upper- and mid-high band (UHB + MHB) diplexer, for LTE 4G and 5G bands using carrier aggregation. The SAW extractor combines a bandpass filter (BPF) and a band-stop filter (BSF) in a single unit that consists of eight modified Butterworth–van Dyke (mBVD) resonators that resonate in parallel with an inductor and SAW resonators. This BSF behaves as a high-pass filter at frequencies lower than the designed WIFI band and as a capacitor at higher frequencies. The SAW extractor meets product specifications in the frequency range 0.7 to 2.7 GHz. The UHB + MHB diplexer, which is composed of a microwave filter, a SAW filter, and a simple matching inductor, uses frequency response methods to create an RF component for 2.4 GHz + WIFI 6E applications. The design uses a SAW’s interdigital transducer (IDT) structure, and the experimental results are in agreement with the simulation results, so the design is feasible. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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14 pages, 7102 KiB

Open AccessArticle

Optimization of Surface Acoustic Wave Resonators on 42°Y-X LiTaO₃/SiO₂/Poly-Si/Si Substrate for Improved Performance and Transverse Mode Suppression

by Hongzhi Pan, Yang Yang, Lingqi Li, Qiaozhen Zhang, Zeyu Zheng, Xuesong Du, Pingjing Chen, Jiahe Dong, Chuan Lu, Xiao Xie, Hualin Li, Qiang Xiao, Jinyi Ma and Zhenglin Chen

Micromachines 2024, 15(1), 12; https://doi.org/10.3390/mi15010012 - 21 Dec 2023

Cited by 2 | Viewed by 1453

Abstract

SAW devices with a multi-layered piezoelectric substrate have excellent performance due to advantages such as a high quality factor, Q, low loss insertion, large bandwidth, etc. Prior to manufacturing, a comprehensive analysis and proper design are essential to evaluating the device’s key [...] Read more.

SAW devices with a multi-layered piezoelectric substrate have excellent performance due to advantages such as a high quality factor, Q, low loss insertion, large bandwidth, etc. Prior to manufacturing, a comprehensive analysis and proper design are essential to evaluating the device’s key performance indicators, including the Bode Q value, bandwidth, and transverse mode suppression. This study explored the performance of SAW resonators employing a 42°Y-X LiTaO₃ (LT) thin-plate-based multi-layered piezoelectric substrate. The thicknesses for each layer of the 42°Y-X LT/SiO₂/poly-Si/Si substrate were optimized according to the index of phase velocity, Bode Q value, and bandwidth. The effect of the device structure parameters on the dispersion curve and slowness curve was studied, and a flat slowness curve was found to be favorable for transverse mode suppression. In addition, the design of the dummy configuration was also optimized for the suppression of spurious waves. Based on the optimized design, a one-port resonator on the 42°Y-X LT/SiO₂/poly-Si/Si substrate was fabricated. The simulation results and measurements are presented and compared, which provides guidelines for the design of new types of SAW devices configured with complex structures. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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14 pages, 2576 KiB

Open AccessArticle

Phononic-Crystal-Based SAW Magnetic-Field Sensors

by Mohsen Samadi, Julius Schmalz, Jana Marie Meyer, Fabian Lofink and Martina Gerken

Micromachines 2023, 14(11), 2130; https://doi.org/10.3390/mi14112130 - 20 Nov 2023

Cited by 3 | Viewed by 1573

Abstract

In this theoretical study, we explore the enhancement of sensing capabilities in surface acoustic wave (SAW)-based magnetic field sensors through the integration of engineered phononic crystals (PnCs). We particularly focus on amplifying the interaction between the SAW and magnetostrictive materials within the PnC [...] Read more.

In this theoretical study, we explore the enhancement of sensing capabilities in surface acoustic wave (SAW)-based magnetic field sensors through the integration of engineered phononic crystals (PnCs). We particularly focus on amplifying the interaction between the SAW and magnetostrictive materials within the PnC structure. Through comprehensive simulations, we demonstrate the synchronization between the SAWs generated by IDTs and the resonant modes of PnCs, thereby leading to an enhancement in sensitivity. Furthermore, we investigate the ΔE effect, highlighting the sensor’s responsiveness to changes in external magnetic fields, and quantify its magnetic sensitivity through observable changes in the SAW phase velocity leading to phase shifts at the end of the delay line. Notably, our approach yields a magnetic field sensitivity of approximately

S ~ 138 \frac{°}{m T}

for a delay line length of only 77 µm in homogeneous magnetic fields. Our findings underline the potential of PnCs to advance magnetic field sensing. This research offers insights into the integration of engineered materials for improved sensor performance, paving the way for more effective and accurate magnetic field detection solutions. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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14 pages, 3105 KiB

Open AccessArticle

Research on the SAW Gyroscopic Effect in a Double-Layer Substrate Structure Incorporating Non-Piezoelectric Materials

by Hengbiao Chen, Lili Meng, Mengjiao Lu, Ziwen Song, Wen Wang and Xiuting Shao

Micromachines 2023, 14(10), 1834; https://doi.org/10.3390/mi14101834 - 26 Sep 2023

Viewed by 1110

Abstract

The SAW (surface acoustic wave) gyroscopic effect is a key parameter that reflects the sensitivity performance of SAW angular velocity sensors. This study found that adding a layer of non-piezoelectric material with a lower reflection coefficient than that of the upper-layer material below [...] Read more.

The SAW (surface acoustic wave) gyroscopic effect is a key parameter that reflects the sensitivity performance of SAW angular velocity sensors. This study found that adding a layer of non-piezoelectric material with a lower reflection coefficient than that of the upper-layer material below the piezoelectric substrate to form a double-layer structure significantly enhanced the SAW gyroscopic effect, and the smaller the reflection coefficient of the lower-layer material, the stronger the SAW gyroscopic effect, with values being reached that were two to three times those with single-layer substrate structures. This was confirmed using a three-dimensional model, and the experimental results also showed that the thickness of the piezoelectric layer and the type of the lower-layer material also had a significant impact on the SAW gyroscopic effect. This novel discovery will pave the way for the future development of SAW angular velocity sensors. Full article

(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)

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