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31 pages, 28202 KiB

Open AccessArticle

Analysis of Acoustic Surface Wave Focused Unidirectional Interdigital Transducers Using Coupling-of-Mode Theory

by Guopeng Hui, Tinglun Ao, Haotian Liu, Minglei Li and Chen Chen

Micromachines 2025, 16(1), 3; https://doi.org/10.3390/mi16010003 - 24 Dec 2024

Viewed by 958

In cell or droplet separation, high acoustic wave energy of a surface acoustic wave (SAW) device is required to generate sufficient acoustic radiation force. In this paper, the electrode width-control floating electrode focused unidirectional interdigital transducer (EWC-FEFUDT) is proposed due to its enhanced [...] Read more.

In cell or droplet separation, high acoustic wave energy of a surface acoustic wave (SAW) device is required to generate sufficient acoustic radiation force. In this paper, the electrode width-control floating electrode focused unidirectional interdigital transducer (EWC-FEFUDT) is proposed due to its enhanced focusing properties. The performance of the EWC-FEFUDT is investigated using the Coupling-of-Mode (COM) theory, and the COM parameter is extracted using the Finite Element Method (FEM). The four different forbidden band edge frequencies account for the unidirectionality of the proposed EWC-FEFUDT. A direction angle of

ϕ_{κ} - ϕ_{ζ} = 44.5 °

of the EWC-FEFUDT (Design 3) is obtained, being fairly close to the optimum value of 45°. The EWC-FEFUDT (Design 3) has a lower insertion loss (IL) of −5.1 dB and greater unidirectionality (20 × log₁₀(

D

) = 13.8 dB). The SAW maximum amplitude of the EWC-FEFUDT (Design 3) is increased by about

1.5 \times 1 0^{- 4} µ m

compared to that of the focused interdigital transducers (FIDTs). The maximum acoustic pressure of the EWC-FEFUDT is an order of magnitude higher than that of FIDTs. The EWC-FEFUDT exhibits enhanced focusing properties. The proposed EWC-FEFUDT may provide an alternative method for cell or droplet separation in an efficient manner. Full article

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14 pages, 4626 KiB

Open AccessArticle

The Extraction of Coupling-of-Modes Parameters in a Layered Piezoelectric Substrate and Its Application to a Double-Mode SAW Filter

by Lingqi Li, Qiaozhen Zhang, Yang Yang, Baichuan Li, Yahui Tian, Xiangyong Zhao and Sulei Fu

Micromachines 2023, 14(12), 2205; https://doi.org/10.3390/mi14122205 - 3 Dec 2023

Cited by 3 | Viewed by 2547

Abstract

This paper presents an advanced method that combines coupling-of-modes (COM) theory and the finite element method (FEM), which enables the quick extraction of COM parameters and the accurate prediction of the electroacoustic and temperature behavior of surface acoustic wave (SAW) devices. For validation, [...] Read more.

This paper presents an advanced method that combines coupling-of-modes (COM) theory and the finite element method (FEM), which enables the quick extraction of COM parameters and the accurate prediction of the electroacoustic and temperature behavior of surface acoustic wave (SAW) devices. For validation, firstly, the proposed method is performed for a normal SAW resonator. Then, the validated method is applied to analysis of an I.H.P. SAW resonator based on a 29°YX−LT/SiO₂/SiC structure. Via optimization, the electromechanical coupling coefficient (K²) is increased up to 13.92% and a high quality (Q) value of 1265 is obtained; meanwhile, the corresponding temperature coefficient of frequency (TCF) is −10.67 ppm/°C. Furthermore, a double-mode SAW (DMS) filter with low insertion loss and excellent temperature stability is also produced. It is demonstrated that the proposed method is effective even for SAW devices with complex structures, providing a useful tool for the design of SAW devices with improved performance. Full article

(This article belongs to the Special Issue Recent Advances in Microwave Components and Devices, 2nd Edition)

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16 pages, 7178 KiB

Open AccessArticle

Electrical and Optical Characterization of SAW Sensors Coated with Parylene C and Their Analysis Using the Coupling-of-Modes (COM) Theory

by Nikolay Smagin, Meddy Vanotti, Marc Duquennoy, Lionel Rousseau, Hassan Alhousseini, Virginie Blondeau-Patissier, Mohammadi Ouaftouh, Laurie Valbin and Etienne Herth

Sensors 2022, 22(22), 8611; https://doi.org/10.3390/s22228611 - 8 Nov 2022

Cited by 6 | Viewed by 3047

Abstract

In this paper, we present how complementary characterization techniques, such as electrical measurements with a vector network analyzer (VNA), optical measurements with a laser Doppler vibrometer (LDV), and numerical simulations with the finite element method, coupled with spectral domain analysis (FEMSDA), allow us [...] Read more.

In this paper, we present how complementary characterization techniques, such as electrical measurements with a vector network analyzer (VNA), optical measurements with a laser Doppler vibrometer (LDV), and numerical simulations with the finite element method, coupled with spectral domain analysis (FEMSDA), allow us to independently access different properties of a SAW device and fully characterize its operation using the coupling-of-modes theory (COM). A set of chemical SAW sensors coated with parylene C layers of different thicknesses (1, 1.5, and 2 µm) and an uncoated sensor were used as test samples. The sensors represent dual-channel electroacoustic delay lines operating in the vicinity of 77 MHz. The IDTs consist of split aluminum electrodes deposited on a AT-cut quartz substrate. The thickness-dependent influence of the parylene C layer was observed on the operating frequency (SAW velocity), static capacitance, attenuation, crosstalk, and reflection coefficient. COM parameters were reported for the four cases considered; measured and simulated data show good agreement. The presented approach is suitable for the design, characterization, and validation of polymer film-coated SAW sensors. Full article

(This article belongs to the Section Biosensors)

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13 pages, 5660 KiB

Open AccessArticle

Analysis and Design of Single-Phase Unidirectional Transducers with High Directivity

by Xueping Sun, Shaobo Ge, Xiuting Shao, Shun Zhou, Wen Wang, Dabin Lin and Weiguo Liu

Appl. Sci. 2021, 11(16), 7500; https://doi.org/10.3390/app11167500 - 16 Aug 2021

Cited by 6 | Viewed by 3248

Abstract

Electrode-width-controlled (EWC) single-phase unidirectional transducers (SPUDT) contribute to reduction of insertion loss of surface acoustic wave (SAW) devices due to their strong unidirectional properties. In this work, we propose a method to optimize the unidirectionality of EWC-SPUDT based on our research results that [...] Read more.

Electrode-width-controlled (EWC) single-phase unidirectional transducers (SPUDT) contribute to reduction of insertion loss of surface acoustic wave (SAW) devices due to their strong unidirectional properties. In this work, we propose a method to optimize the unidirectionality of EWC-SPUDT based on our research results that the unidirectionality of the EWC-SPUDT cell is strongly related to its reflectivity and its unidirectional angle. Furthermore, in order to ensure strong unidirectionality to achieve low insertion loss, a simulator based on the finite element method (FEM) is used to study the relationship between geometrical configuration of the EWC-SPUDT cell and its reflection coefficient, as well as its transduction coefficient. Simulation results indicate that the reflection coefficient of the optimized EWC-SPUDT cell composed of 128° YX lithium niobite (LiNbO₃) substrate and Al electrodes with thickness of 0.3μm reaches the optimal value of 5.17% when the unidirectional angle is designed to be −90°. A SAW delay line is developed with the optimized EWC-SPUDT cell without weighing, and the simulation results are verified by experiments. The experimental results show that the directivity exceeds 30 dB at the center frequency and the insertion loss is just 6.7 dB. Full article

(This article belongs to the Special Issue Wireless and Passive Surface Acoustic Wave Sensor)

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12 pages, 38265 KiB

Open AccessLetter

Simulation of SAW Sensors with Various Distributed Mass Loadings Using Two-Dimensional Coupling-of-Modes Theory

by Ran You, Jiuling Liu, Minghua Liu, Zhiyuan Chen and Shitang He

Sensors 2020, 20(24), 7260; https://doi.org/10.3390/s20247260 - 18 Dec 2020

Cited by 2 | Viewed by 2981

Abstract

In order to accurately investigate the disturbance of complex distributed mass loading on surface acoustic wave (SAW) propagation characteristics, two-dimensional coupling-of-modes (2-D COM) theory and finite element method (FEM) were used to simulate the responses of SAW sensors. By using the PDE mode [...] Read more.

In order to accurately investigate the disturbance of complex distributed mass loading on surface acoustic wave (SAW) propagation characteristics, two-dimensional coupling-of-modes (2-D COM) theory and finite element method (FEM) were used to simulate the responses of SAW sensors. By using the PDE mode of FEM software, four SAW resonators with the loads in different distribution patterns were modeled. Also, we fabricated and measured a series of SAW resonators accordingly. The results showed that the 2-D COM theory combined with the finite element method was able to simulate the transverse modes of the device and the disturbance of the mass loading on the transverse mode effectively, making the simulation more accurate. Full article

(This article belongs to the Section Physical Sensors)

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12 pages, 9790 KiB

Open AccessArticle

Fabrications of L-Band LiNbO₃-Based SAW Resonators for Aerospace Applications

by Baofa Hu, Shaoda Zhang, Hong Zhang, Wenlong Lv, Chunquan Zhang, Xueqin Lv and Haisheng San

Micromachines 2019, 10(6), 349; https://doi.org/10.3390/mi10060349 - 28 May 2019

Cited by 20 | Viewed by 6681

Abstract

High frequency surface acoustic wave (SAW) technology offers many opportunities for aerospace applications in passive wireless sensing and communication. This paper presents the design, simulation, fabrication, and test of an L-band SAW resonator based on 128° Y-X LiNbO₃ substrate. The design [...] Read more.

High frequency surface acoustic wave (SAW) technology offers many opportunities for aerospace applications in passive wireless sensing and communication. This paper presents the design, simulation, fabrication, and test of an L-band SAW resonator based on 128° Y-X LiNbO₃ substrate. The design parameters of SAW resonator were optimized by the finite element (FEM) method and the coupling-of-mode (COM) theory. Electron-beam lithography (EBL) technology was used to fabricate the submicron-scale of interdigital transducers (IDTs) and grating reflectors. The effects of some key EBL processes (e.g., the use of electron beam resist, the choice of metal deposition methods, the charge-accumulation effect, and the proximity-effect) on the fabrication precision of SAW devices were discussed. Experimentally, the LiNbO₃-based SAW resonators fabricated using improved EBL technology exhibits a Rayleigh wave resonance peaks at 1.55 GHz with return loss about −12 dB, and quality factor Q is 517. Based on this SAW resonator, the temperature and strain sensing tests were performed, respectively. The experimental results exhibit a well linear dependence of temperature/strain on frequency-shift, with a temperature sensitivity of 125.4 kHz/°C and a strain sensitivity of −831 Hz/με, respectively. Full article

(This article belongs to the Special Issue MEMS for Aerospace Applications)

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11 pages, 3810 KiB

Open AccessArticle

Surface Acoustic Wave Gyroscopic Effect in an Interdigital Transducer

by Xueping Sun, Weiguo Liu, Xiuting Shao, Shun Zhou, Wen Wang and Dabin Lin

Sensors 2019, 19(1), 106; https://doi.org/10.3390/s19010106 - 29 Dec 2018

Cited by 13 | Viewed by 5569

Abstract

The surface acoustic wave (SAW) gyroscopic effect in an interdigital transducer (IDT) deposited on a piezoelectric substrate is different from that in the piezoelectric substrate due to a reflection induced by IDT. In this work, an extended coupling-of-mode (COM) model including the gyroscopic [...] Read more.

The surface acoustic wave (SAW) gyroscopic effect in an interdigital transducer (IDT) deposited on a piezoelectric substrate is different from that in the piezoelectric substrate due to a reflection induced by IDT. In this work, an extended coupling-of-mode (COM) model including the gyroscopic effect and the reflection was developed to analyze the SAW gyroscopic effect. First, dispersion characteristics parameters of SAW were fitted according to the data derived using the finite element method (FEM). Then, variations of stop band edge frequency were calculated using the extended COM theory by integrating dispersion characteristics parameters into the COM model. We compared its results with those obtained via FEM analysis to confirm the proposed model’s validity. We found that the variation in stop band edge frequency related to gyroscope effect reached the maximum value with a zero reflectivity value. For split IDT, the sensitivity of gyroscope effect is 0.036 Hz/rad/s with a lower than 1% normalized thickness. Conversely, the value of sensitivity was almost zero for bidirectional IDT and electrode width controlled single-phase unidirectional transducer (EWC/SPUDT). Full article

(This article belongs to the Special Issue Surface Acoustic Wave Sensors)

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13 pages, 15721 KiB

Open AccessArticle

A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

by Jiuling Liu, Wenchang Hao, Minghua Liu, Yong Liang and Shitang He

Appl. Sci. 2018, 8(1), 82; https://doi.org/10.3390/app8010082 - 9 Jan 2018

Cited by 24 | Viewed by 7146

Abstract

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM_2.5 capture and a SAW [...] Read more.

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM_2.5 capture and a SAW sensor chip for PM_2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM) model and the PM_2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM) model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS) technology and semiconductor technology, the SAW based PM_2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM_2.5 sensor to the polystyrene latex (PSL) particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 μm, the response of the SAW based PM_2.5 sensor is linear, and in accordance with the response of the light scattering based PM_2.5 monitor. The developed SAW based PM_2.5 sensor has great potential for the application of airborne particle detection. Full article

(This article belongs to the Section Acoustics and Vibrations)

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12 pages, 2376 KiB

Open AccessArticle

Development of a Wireless and Passive SAW-Based Chemical Sensor for Organophosphorous Compound Detection

by Fang-Qian Xu, Wen Wang, Xu-Feng Xue, Hao-Liang Hu, Xin-Lu Liu and Yong Pan

Sensors 2015, 15(12), 30187-30198; https://doi.org/10.3390/s151229793 - 3 Dec 2015

Cited by 22 | Viewed by 8158

Abstract

A new wireless and passive surface acoustic wave (SAW)-based chemical sensor for organophosphorous compound (OC) detection is presented. A 434 MHz reflective delay line configuration composed by single phase unidirectional transducers (SPUDTs) and three shorted reflectors was fabricated on YZ LiNbO₃ piezoelectric [...] Read more.

A new wireless and passive surface acoustic wave (SAW)-based chemical sensor for organophosphorous compound (OC) detection is presented. A 434 MHz reflective delay line configuration composed by single phase unidirectional transducers (SPUDTs) and three shorted reflectors was fabricated on YZ LiNbO₃ piezoelectric substrate as the sensor element. A thin fluoroalcoholpolysiloxane (SXFA) film acted as the sensitive interface deposited onto the SAW propagation path between the second and last reflectors of the SAW device. The first reflector was used for the temperature compensation utilizing the difference method. The adsorption between the SXFA and OC molecules modulates the SAW propagation, especially for the time delay of the SAW, hence, the phase shifts of the reflection peaks from the corresponding reflectors can be used to characterize the target OC. Prior to the sensor fabrication, the coupling of modes (COM) and perturbation theory were utilized to predict the SAW device performance and the gas adsorption. Referring to a frequency-modulated continuous wave (FMCW)-based reader unit, the developed SAW chemical sensor was wirelessly characterized in gas exposure experiments for dimethylmethylphosphonate (DMMP) detection. Sensor performance parameters such as phase sensitivity, repeatability, linearity, and temperature compensation were evaluated experimentally. Full article

(This article belongs to the Section Chemical Sensors)

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