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SAW devices and their wireless communications applications
Abstract
Due to the superior performance of SAW filters, combined with
additional features, e.g., impedance transformation, balun
functionality, and integration of two or even three filter functions
into one package, SAW filters have become the key components in mobile
communication and multimedia applications. More cost-effective and
miniaturized designs are effectively supported by reducing overall
component count and PCB space used
... This wide usage of LN in numerous applications can be explained by its rich array of material characteristics, exhibiting strong pyroelectric, piezoelectric, electro-optic, photorefractive, acousto-optic, photovoltaic, and nonlinear optical properties 4−10 . Furthermore, LN has a wide optical transparency window (350 nm to 5 μm) 11,12 , providing the means to utilise the attractive material properties over a wide spectrum, which has enabled record-breaking experimental demonstrations in fundamental science 12 . LN's maturity has also enabled many commercial LN devices, such as acoustic frequency bandpass filters for mobile communications 13 and high-speed electro-optical modulators that helped to underpin the Internet 14 . ...
... This wide usage of LN in numerous applications can be explained by its rich array of material characteristics, exhibiting strong pyroelectric, piezoelectric, electro-optic, photorefractive, acousto-optic, photovoltaic, and nonlinear optical properties 4−10 . Furthermore, LN has a wide optical transparency window (350 nm to 5 μm) 11,12 , providing the means to utilise the attractive material properties over a wide spectrum, which has enabled record-breaking experimental demonstrations in fundamental science 12 . LN's maturity has also enabled many commercial LN devices, such as acoustic frequency bandpass filters for mobile communications 13 and high-speed electro-optical modulators that helped to underpin the Internet 14 . ...
... In the last few years, LN has attracted renewed interest, particularly from the integrated photonic community, due to the commercial availability of thin-film LN on insulator (LNOI). This integrated photonic platform has sparked a renaissance in exploiting the optical material properties of LN as it enables low-loss optical waveguides with much stronger confined optical modes compared to the traditional diffusion-based waveguides in bulk LN 12,18,19 , enabling more compact and complex integrated optical devices with more than an order of magnitude improved nonlinear optical efficiencies 20−22 and more efficient and faster electro-optical modulators 23−25 . In LNOI, ferroelectric domain engineering also plays a crucial role in designing optical circuit components. ...
... The surface acoustic wave (SAW) resonator is one example. The most existing acoustic wave resonators are those based on piezoelectric materials such as quartz (SiO 2 ) [6,7], lithium niobate (LiNbO 3 ) [8][9][10], and lithium tantalate (LiTaO 3 ) [11,12]. Quartz crystals have been dominating the market because of its accuracy, high quality factor and high temperature stability [13]. ...
... Series and parallel resonance frequencies are obtained as shown in Eqn. (12) and Eqn. (13) respectively. ...
... Acoustic wave resonators for surface acoustic wave (SAW) technology have rapidly developed and can reache up to GHz frequency [12]. The integration of SAW devices with accompanying circuitry, as a single chip is essential to reduce insertion loss, simplify the packaging, and reduce the device size and area. ...
Continuous advancement in wireless technology and silicon microfabrication has fueled exciting growth in wireless products. The bulky size of discrete vibrating mechanical devices such as quartz crystals and surface acoustic wave resonators impedes the ultimate miniaturization of single-chip transceivers. Fabrication of acoustic wave resonators on silicon allows complete integration of a resonator with its accompanying circuitry. Integration leads to enhanced performance, better functionality with reduced cost at large volume production. This paper compiles the state-of-the-art technology of silicon compatible acoustic resonators, which can be integrated with interface circuitry. Typical acoustic wave resonators are surface acoustic wave (SAW) and bulk acoustic wave (BAW) resonators. Performance of the resonator is measured in terms of quality factor, resonance frequency and insertion loss. Selection of appropriate piezoelectric material is significant to ensure sufficient electromechanical coupling coefficient is produced to reduce the insertion loss. The insulating passive SiO2 layer acts as a low loss material and aims to increase the quality factor and temperature stability of the design. The integration technique also is influenced by the fabrication process and packaging. Packageless structure using AlN as the additional isolation layer is proposed to protect the SAW device from the environment for high reliability. Advancement in miniaturization technology of silicon compatible acoustic wave resonators to realize a single chip transceiver system is still needed.
ABSTRAK: Kemajuan yang berterusan dalam teknologi tanpa wayar dan silikon telah menguatkan pertumbuhan yang menarik dalam produk tanpa wayar. Saiz yang besar bagi peralatan mekanikal bergetar seperti kristal kuarza menghalang pengecilan untuk merealisasikan peranti cip. Silikon serasi gelombang akustik resonator mempunyai potensi yang besar untuk menggantikan unsur-unsur diskret kerana keupayaan untuk mengintegrasikan dengan litar yang disertakan itu. Integrasi ini membawa kepada peningkatan prestasi, fungsi yang lebih baik dengan pengurangan kos pada pengeluaran jumlah yang besar. Oleh itu, Karya ini mengkaji silikon resonator akustik yang serasi, yang bersepadu dengan muka litar untuk membolehkan integrasi yang lengkap. Resonator gelombang akustik yang digunakan adalah gelombang permukaan akustik ( SAW ) dan gelombang akustik pukal ( BAW ) resonator . Kriteria penting untuk menilai prestasi resonator seperti faktor kualiti, frekuensi resonans dan kehilangan sisipan juga digariskan dalam setiap kerja sebelumnya. Pemilihan bahan piezoelektrik yang sesuai adalah penting untuk memastikan pekali gandingan elektromekanik yang mencukupi dihasilkan untuk mengurangkan kehilangan sisipan. Lapisan tambahan pasif SiO2 yang bertindak sebagai bahan rendah sisipan dipercayai meningkatkan faktor kualiti dan kestabilan suhu reka bentuk. Teknik integrasi juga dipengaruhi oleh proses fabrikasi dan pembungkusan. Struktur tanpa pembungkusan menggunakan AlN sebagai lapisan pengasingan tambahan itu dicadangkan untuk melindungi peranti SAW dari persekitaran untuk kebolehpercayaan yang tinggi. Banyak lagi kemajuan perlu dilakukan dalam pengecilan silikon serasi resonator gelombang akustik untuk merealisasikan sistem cip transceiver tunggal.
KEYWORDS: RF-MEMS; piezoelectric; resonator; surface acoustic wave (SAW);bulk acoustic wave (BAW); FBAR
... In general, these filters are used to isolate diverse communication bands and avoid cross talk and unwanted noise signals, which puts demands on the high-precision frequency control of SAW resonators in industrial manufacturing [6][7][8][9][10]. For instance, the multiplexer of mobile communication is integrated by a series of SAW resonators, and the neighboring bands are very close in frequency (e.g., Bands 5,8,22,and 25); the excessive frequency offset of SAW resonance would lead to the generation of undesired signals between two adjacent bands [11]. Nowadays, lithium tantalate (LT, LiTaO 3 ) wafers are the most widely used acoustic-electric material for the fabrication of SAW resonators. ...
... C 0 is the static capacitance between the IDT and the LT-based wafer. Typically, the IDT width W e is designed as λ∕4 [22], and the SAW frequency is determined by f v∕λ, where λ and v denote the SAW wavelength (4.5 μm) and velocity (3800 m/s), respectively. Thus, the SAW resonance frequency f r and anti-resonance frequency f a can be defined as below [23][24][25]: ...
Surface acoustic wave (SAW) resonators based on lithium tantalate (LT, LiTaO 3 ) wafers are crucial elements of mobile communication filters. The use of intrinsic LT wafers typically brings about low fabrication accuracy of SAW resonators due to strong UV reflection in the lithography process. This hinders their resonance frequency control seriously in industrial manufacture. LT doping and chemical reduction could be applied to decrease the UV reflection of LT wafers for high lithographic precision. However, conventional methods fail to provide a fast and nondestructive approach to identify the UV performance of standard single-side polished LT wafers for high-precision frequency control. Here, we propose a convenient on-line sensing scheme based on the colorimetry of reduced Fe-doped LT wafers and build up an automatic testing system for industrial applications. The levels of Fe doping and chemical reduction are evaluated by the lightness and color difference of LT-based wafers. The correlation between the wafer visible colorimetry and UV reflection is established to refine the lithography process and specifically manipulate the frequency performance of SAW resonators. Our study provides a powerful tool for the fabrication control of SAW resonators and will inspire more applications on sophisticated devices of mobile communication.
... A non-uniformity of the temperature on wafer surface due to a large wafer size in the plasma chamber leads to deterioration of yield and lowering of productivity [1]. In the Fourth Industrial Revolution, real-time in situ process monitoring of the wafer surface temperature during IC chip fabrication through the installation of associated sensors inside The present work is an extension of the paper "ICEE-CCA 2023 Development of highly sensitive and stable SAW-based temperature sensor array and its interface electronics for real-time monitoring of wafer surface temperature in plasma chamber" presented to ICEE-CCA 2023 Conference, [16][17][18][19] August, Tashkent, Uzbekistan, and published in Journal of Electrical Engineering & Technology (JEET). manufacturing equipment becomes important because when an abnormalities are detected during the process, the equipment itself makes decisions based on artificial intelligence (AI) and takes the necessary measures to resolve the problems and improve the yield in semiconductor manufacturing processes by adjusting chamber pressure, gas flow rate, RF power, etc. ...
... COM modeling was performed to determine the optimal structural parameters of the two-port SAW resonator and then predict the frequency shifts depending on the temperature variations. A 128° YX LiNbO 3 was selected as the piezoelectric material because it has a large electromechanical coefficient factor (K 2 ) of ~ 5.5% and a high temperature coefficient of delay (TCD) of ~ 75 ppm/ o C [18]. Taking into account transmission line capacitance, and impedance matching with the oscillator, a two-port SAW resonator with ~ 380 MHz center frequency was designed and modeled via COM. ...
Temperature sensor array and its associated peripheral interface electronics has been developed for real-time monitoring of the wafer surface temperature at multiple spots on wafer in the plasma chamber. The developed sensor system comprises multiple surface acoustic wave (SAW) temperature sensors and their associated oscillators inside the chamber, and multiplexer, mixer, low pass filter, comparator, field-programmable gate array, and PC outside the chamber. The interface electronics were assembled on a single printed circuit board to improve the system performance and facilitate the installation of the system. All the SAW temperature sensors on the wafer surface have the same configurations including the same center frequency and the same variations in the resonant frequency with temperature. A multiplexer with several channels was developed to separate the sensor’s signals and then display each sensor signal on PC one by one through a time interval of 0.2 s. The increases in temperature on wafer surface downshifted the resonant frequencies of the SAW temperature sensors. The resultant sensitivity and linearity of the wired temperature sensor system were 24.2 kHz/°C and 0.99, respectively. A wireless wafer temperature measurement was also developed by putting antennas on the output port of the multiplexer and the input port of the mixer. A clear and noticeable frequency shifts were observed on PC display depending on different temperatures at the reading distance of 5 m. The evaluated sensitivity and the linearity were almost the same as those obtained by the wired measurement. The developed SAW sensors showed long term stability against energetic UV-C radiation and electromagnetic interference owing to a thin Si3N4 protection layer.
... (a) (b) Another critical component of the impedance tuners is the SAW resonators, fabricated on various materials and structures to achieve a high Q-factor characteristic [52][53][54][55][56][57]. A SAW device is composed of a piezoelectric substrate with metallic structures, such as IDTs in Figure 3.12, and the reflection or coupling gratings deposited on its plain-polished surface. ...
... 11 (a) Cross-section of DTC[50] (b) Schematic of a dual-gap relay-type DTC[51] (c) DTC silicon schematic[49] (d) Extracted DTC equivalent circuit[49]. 12 (a) Schematic of an IDT with pitch p (b) Associated P-matrix model with u in and i in being the electrical voltage and current, as a and b the incident and outgoing acoustic waves (c) Input and output IDTs layout of a two-port SAW resonator[52]. ...
Today's radio frequency front-ends (RFFEs) employed in cellular devices achieve duplex operation by utilizing discrete, fixed-frequency surface acoustic wave (SAW) or bulk acoustic wave (BAW) filters. The state-of-the-art tunable filters cannot meet the demanding requirements for steep roll-off and low insertion loss, supporting multi-band operation. As a result, they require multiple fixed-frequency duplexers and switches for band selection. However, supporting all the frequency bands increases circuit design complexity, area consumption, and manufacturing cost. It is a crucial challenge and research interest to develop a tunable RFFE. This thesis starts with an introduction to this work. The first chapter presents the motivation and objective, then in the following chapter, fundamental and background knowledge of duplexers is reviewed. From the works of literature and state-of-the-art, various architectures in hardware domains such as SAW-, circulator- and hybrid transformer-based or software domains like digital cancellation have been proposed to achieve full-duplexing (FD). Motivated by the concept of electrical balance, two alternative duplexer design approaches from literature are presented for LTE low band application. One of them is the Wheatstone bridge balanced duplexer (WBD). This architecture combines the electrical balanced duplexer (EBD) and the Wheatstone bridge circuit. It uses the SAW technology and digitally tunable capacitors (DTCs) to realize the circuit blocks in the system, as shown in Chapter 3. Another proposed architecture is a phase gradient supported balanced duplexer (PBD) which has been investigated at the Institute of Electronics Engineering in FAU Erlangen-Nürnberg to overcome the insertion loss limitation that features at least 3 dB in the EBD concept. Through the equation-defined design parameters of circuit blocks and detailed system analysis, the PBD concept is described theoretically in Chapter 4. With these two presented architectures, the key performance indicator of duplexer insertion loss at Tx and Rx band can achieve 2.9 and 2.8 dB, respectively, and the transmit-to-receive isolation can reach over 50 dB. Last, this thesis summarizes and reviews the WBD and PBD performance in Chapter 5. It is feasible to have a small form-factor and tunable duplexer realization targeted at LTE low band application by implementing complementary metal-oxide-semiconductor (CMOS) and metal-based micro-electro-mechanical systems (MEMS) technology in the proposed architectures.
... In recent years, significant advancements in surface acoustic wave (SAW) design and manufacturing technology have given it obvious advantages over other competing technologies, including compact size, excellent performance, high stability, low cost, and simple fabrication processes. These advantages have made it a key component in various radio frequency (RF) and microwave systems, such as radar, wireless communication, satellite navigation, and sensing applications [1][2][3][4][5]. ...
A SAW device with a multi-layered piezoelectric substrate has excellent performance due to its high Q value. A multi-layer piezoelectric substrate combined with phononic crystal structures capable of acoustic wave reflection with a very small array can achieve miniaturization and high performance. In this paper, a honeycomb-shaped phononic crystal structure based on 42°Y-X LT/SiO2/poly-Si/Si-layered substrate is proposed. The analysis of the bandgap distribution under various filling fractions was carried out using dispersion and transmission characteristics. In order to study the application of PnCs in SAW devices, one-port resonators with different reflectors were compared and analyzed. Based on the frequency response curves and Bode-Q value curves, it was found that when the HC-PnC structure is used as a reflector, it can not only improve the transmission loss of the resonator but also reduce the size of the device.
... Acoustic antennas could be used to launch surface acoustic waves (SAW) in a solid and these waves have found myriad applications in sensors [36], filters [37], and micro/nano mechanical systems (MEMS/NEMS) [38]. They have also been used for quantum control [39]. ...
Magnetic straintronics made its debut more than a decade ago as an extremely energy-efficient paradigm for implementing a digital switch for digital information processing. The switch consists of a slightly elliptical nano-sized magnetostrictive disk in elastic contact with a piezoelectric layer (forming a two-phase multiferroic system). Because of the elliptical shape, the nanomagnet’s magnetization has two stable (mutually antiparallel) orientations along the major axis, which can encode the binary bits 0 and 1. A voltage pulse of sub-ns duration and amplitude few to few tens of mV applied across the piezoelectric generates enough strain in the nanomagnet to switch its magnetization from one stable state to the other by virtue of the inverse magnetostriction (or Villari) effect, with an energy expenditure that is roughly an order of magnitude smaller than what it takes to switch a modern-day electronic transistor. That possibility, along with the fact that such a switch is non-volatile unlike the conventional transistor, generated significant excitement. However, it was later tempered by the realization that straintronic switching is also extremely error-prone , which may preclude many digital applications, particularly in Boolean logic. In this perspective, we offer the view that there is plenty of room for magnetic straintronics in the analog domain, which is much more forgiving of switching errors, and where the excellent energy-efficiency and non-volatility are a boon. Analog straintronics can have intriguing applications in many areas, such as a new genre of aggressively miniaturized electromagnetic antennas that defy the Harrington limit on the radiation efficiency of conventional antennas, analog arithmetic multipliers (and ultimately vector matrix multipliers) for non-volatile deep learning networks with very small footprint and excellent energy-efficiency, and relatively high-power microwave oscillators with output frequency in the X-band. When combined with spintronics, analog straintronics can also implement a new type of spin field effect transistor employing quantum materials such as topological insulators, and they have unusual transfer characteristics which can be exploited for analog tasks such as frequency multiplication using just a single transistor. All this hints at a world of new possibilities in the analog domain that deserves serious attention.
... This passive sensor exhibits a compact size of a few centimeters, enabling its deployment in controlled laboratory settings. Moreover, its manufacturing costs are significantly lower than other comparable methods, such as remote sensing and sample colletion and analysis in environmental monitoring [10] [11]. Fig. 1 illustrates a schematic of the SAW sensor's operating principle. ...
Surface acoustic wave sensors can be implemented within the feedback loop of sinusoidal oscillators for detecting pollutants. This detection process involves analyzing the variation of oscillator output voltage parameters, such as amplitude and oscillation frequency. However, each oscillator topology has a distinct operating range concerning frequency and component values. Therefore, a comparative analysis is necessary to determine the oscillator with optimal performance to use with the sensor. To obtain results, a surface acoustic wave sensor model was chosen based on a piezoelectric crystal with a resonant frequency of 117.6 MHz, and three sinusoidal oscillator topologies were used: Pierce, Colpitts, and Clapp. The oscillators were simulated with the sensor model in the feedback loop using the Montecarlo method. The simulation occurred in two steps: individually varying each component by +/- 20% with 250 iterations, and simultaneously varying all components by +/- 20% with 1000 iterations. The variables analyzed in the simulations were amplitude, oscillation frequency, and a new parameter indicating the percentage of time there is an oscillation, termed "robustness." As a result, it was determined that all three oscillators generated oscillations in the output voltage, making them viable for use with the sensor. Furthermore, it was discovered that the Clapp oscillator had a robustness of 84.5%, while the Colpitts and Pierce oscillators had a robustness of 56.3% and 49.9%, respectively. Therefore, based on the results presented in this study, the Clapp oscillator is the optimal choice for use with the surface acoustic wave sensor.
... A related issue of vital importance is noise generated by ferroelectric elements which has widespread applications. Ferroelectric materials are used as an insulating layer in the Gate electrode of CMOS devices [5], as a filter in the front end part of wireless devices [6] and as data storage elements [7]. They are also used as actuator elements in scanning tunnelling microscope [8,9], atomic force microscope [10,11], disk drives [12] besides having a widespread use as sensors for infrastructure monitoring [13,14], magnetic field sensing [15] and related applications where extremely high sensitivity is necessary [16]. ...
We present a novel analytical formulation on generation of electro-acoustic noise in ferroelectric materials where the thermal fluctuations induced polarization and acoustic modes distinctly contribute to noise. The conservative force fields associated with ferroelectric materials drive feedback of the spectral modes in the system. It results in symmetry breaking of the frequency spectrum of broadband noise leading to enhancement of specific modes which generate high amplitude narrowband noise. We describe the process under the theoretical framework of fluctuation-dissipation theorem in the context of ferroelectric materials. We further note that such spectral feedback are absent in Johnson-Nyquist noise generation in conductors which have spectral symmetry.
... SAW devices have become essential components for filters and oscillators in wireless communication due to their advantages of lithographically defined resonance frequencies, simple fabrication process despite the use of materials that have historically been difficult to etch, low manufacturing cost, and low sensitivity to acceleration [1]- [3]. They are also widely used in sensor applications due to SAW sensitivity to various environmental factors including temperature, pressure, viscosity, humidity, etc. at the surface of the device [3]- [6]. ...
This paper presents a comprehensive study of the performance of Sezawa surface acoustic wave (SAW) devices in SweGaN QuanFINE ultrathin GaN/SiC platform, reaching frequencies above 14 GHz for the first time. Sezawa mode frequency scaling is achieved due to the elimination of the thick buffer layer typically present in epitaxial GaN technology. Finite element analysis (FEA) is first performed to find the range of frequencies over which the Sezawa mode is supported in the grown structure. Transmission lines and resonance cavities driven with Interdigital Transducers (IDTs) are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics. We observe a strong correlation between measured and simulated dispersion of the phase velocity (vp) and piezoelectric coupling coefficient (k^2). Maximum k^2 of 0.61% and frequency-quality factor product (f.Qm) of 6x10^12 1/s are achieved for Sezawa resonators at 11 GHz, with a minimum propagation loss of 0.26 dB/wavelength for the two-port devices. Sezawa modes are observed at frequencies spanning up to 14.3 GHz, achieving a record high in GaN microelectromechanical systems (MEMS) to the best of the authors' knowledge.
... The wireless local area network (WLAN) operations cover the industrial, scientific, and medical (ISM) frequency band (2.5 GHz) and the UN-II band (5 GHz) [27]. Nowadays, WLAN devices are deployed in a wide variety of environments. ...
Metamaterials, which are called as left-handed materials, exhibit electromagnetic properties that do not exist in nature, such as negative refractive index and reverse Doppler effect, at the frequency range for which they are designed. These unique properties of metamaterials have made them indispensable in a wide variety of applications such as sensor applications, signal absorption, antenna, and energy harvesting. In this study, the design and analysis of a metamaterial (MTM) perfect absorber at 5 GHz frequency band were performed to investigate the usability of the proposed structure in energy harvesting applications. A negative refractive index of -0.15 was obtained at 5GHz. The variation of absorption, transmission, and reflection of the proposed MTM structure exhibited that a maximum absorbance was monitored at 5 GHz as 0.9949. According to the harvesting application study, the proposed structure has a maximum absorption of 88.3% at 4.98 GHz which is close to resonant frequency in 8000 Ω resistor value. The results of the study revealed that the proposed MTM structure has potentials to be used in energy harvesting applications.
... SAW and BAW filters basically operate by first converting the incident electrical signals into acoustic waves through a piezoelectric material, and then converting them back into the electrical waves upon propagation with the speed of sound in the device. As the wavelength in these filters is shorter than that of an electromagnetic guide by a factor of 10 5 , such filters can allow for a lower propagation velocity, enabling the delay of hundreds of nanoseconds [16][17][18]. Note that the BAW filters are more suitable than the SAW filters in practice when the center frequency of ambient signals is above 1 GHz [15]. ...
This paper investigates a backscatter communications system that exploits ambient pilot symbols used in existing standards based on orthogonal frequency-division multiplexing, such as IEEE802.11, in order to realize ultra-low power communications with longer transmission range and higher data rate than conventional ambient backscatter systems. Two modulation schemes, phase-shift keying (PSK) and a new approach named delay-shift keying (DSK), are investigated for the proposed system, and the optimal design of DSK is provided based on the theoretical upper bound of the symbol error rate (SER) over double frequency-selective channels. An optimal maximum-likelihood (ML) detector is also developed for the proposed system along with a feasible transmission protocol including channel estimation. Computer simulation results reveal that, at a bandwidth efficiency less than 3 bits per channel use (bpcu), PSK achieves the lowest SER while DSK achieves the lowest SER at efficiencies greater than 2 bpcu. The performance of the proposed detector was comparable to that of the conventional joint ML detectors with a lower degree of complexity, even when a limited number of subcarriers were available as pilot symbols.
... High frequency bandpass filters (until several dozen of GHz) started to be developed, opening the door to telecommunication [46]. Among them we can cite * surface acoustic waves * (SAW) [47] and * bulk acoustic waves * (BAW) filters [48]. They are piezoelectric substrates either sandwiched between two electrodes in the case of BAWs, or on which are laid * inter digital transducers * (IDT) generating SAWs. ...
There is an ever growing interest in ultra-accurate mass detection in the health, environment and agri-food fields. In this context, the last decade has seen the emergence of resonant sensors based on Anderson localization in an array of weakly coupled resonators. Known to be highly sensitive to mass perturbations, this phenomenon however requires identical and coupled resonators, which is a challenge due to microfabrication constraints. In order to overcome this limitation, we present in this thesis an alternative solution based on a hybrid system, where a hardware (field programmable gate array) plays the role of a resonator as well as the coupling in closed loop with a quartz cristal microbalance (QCM) having a Q-factor greater than 100000. The digital aspect of the system allows maximum sensitivity to be achieved with a fine tuning of the different parameters. In addition, this system can be adapted to the geometry of the physical resonator, indeed allowing the implementation of mode localization in shear waves resonant structures such as the QCM which is widely used in biosensing for its high Q-factor and large binding surface. This solution has been designed, implemented and tested with digital and mass perturbations, and the results are consistent with theoretical models. Finally, the experimental sensitivities achieved in this work are at least an order of magnitude higher than those found in the literature, which is promising for the design of a new generation of ultrasensitive sensors based on Anderson localization. However, these results have yet to be confronted with signal-to-noise ratio problems, as suggested by the theoretical studies carried out in the framework of this thesis.
... response. [12] Surface acoustic wave (SAW) and bulk acoustic wave (BAW) have emerged as the preferred technologies for manufacturing the microacoustic resonators for use in mobile devices [5,13], by simultaneously achieving high quality and performance as well as small form factor and cost. High performance of a filter is characterized by low insertion loss, high return loss, sharp transition slopes and strong out-of-band rejection. ...
Es wird vorhergesagt, dass der weltweite mobile Datenverkehr bis Ende 2025 um ein fünffaches anwachsen wird und, weshalb die Übertragungsraten hierzu Schritt halten müssen. Der Standard der 5. Generation (5G) verspricht gesteigerte Übertragungsraten durch größere relative Bandbreite der für die mobile Kommunikation verwendeten Frequenzbänder. Die relative Bandbreite von Radiofrequenz- (RF-) Filtern entspricht in etwa der Hälfte des Wertes der effektiven elektromechanischen Kopplung der verbauten Komponenten, wie zum Beispiel Oberflächenwellen- und Volumenwellen-Resonatoren (engl. surface acoustic wave - SAW und bulk acoustic wave - BAW). Etablierte Materialien wie Aluminiumnitrid (AlN) eignen sich nur bedingt für 5G RF-Filter. Verglichen mit AlN zeigt das Material Aluminiumscandiumnitrid (Al1–xScxN mit x < 0,43) einen bis zu doppelt so hohen piezoelektrischen Koeffizienten e33 und einen halb so großen elastischen Koeffizienten C33, was bei Erhalt der positiven Eigenschaften von AlN zu einer höheren elektromechanischen Kopplung führt. Folglich ist dies ein vielversprechendes Material für 5G RF-Filter.
Das Potential von AlScN lässt sich durch Herstellung und systematische Untersuchung von SAW Resonatoren aus diesem neuartigen Material überprüfen. Des Weiteren lässt sich die elektromechanische Kopplung von SAW Resonatoren auf Basis von beispielsweise AlN oder GaN optimieren indem die polare c-Achse des Kristalls in die Ebene der Dünnschicht gelegt wird, so wie es bei Schichten der Fall ist, die mit der unpolaren a-Ebene (engl. a-plane) auf dem Substrat wachsen. Für das a-plane AlScN wird eine noch höhere Kopplung erwartet als für das c-plane ausgerichtete Material, bei dem die polare c-Achse senkrecht zum Schichtoberfläche steht und auf welches sich bisher die meisten Untersuchungen konzentrierten. Das Ziel dieser Dissertation ist es darum, AlScN-basierte SAW Resonatoren zu entwerfen und herzustellen, ihre Leistung in Abhängigkeit der Sc Konzentration, des gewählten Substrats, der Temperatur, der Kristallorientierung (a-plane, c-plane) und Ausbreitungsrichtung der akustischen Oberflächenwellen zu untersuchen sowie das beste Design für eine hohe effektive elektromechanische Kopplung zu ermitteln.
In dieser Arbeit wurden SAW Resonatoren aus Al1–xScxN mit x = {0; 0,14; 0,23; 0,32; 0,41} und Wellenlängen zwischen 2 und 24 µm hergestellt sowie ihre Kenngrößen ermittelt. Grundlage waren mit dem Sputter-Verfahren hergestellte c-plane orientierte AlScN Schichten auf Si(100) und Al2O3(0001) Substraten, als auch a-plane AlScN auf Al2O3(1-102) Substraten. Die Resonanzfrequenzen der Strukturen lagen zwischen 0,18 und 2,1 GHz. Die Kopplung steigt mit zunehmender Anzahl an Elektroden-Fingern der Resonatoren und ein Bestwert für Apertur und Zuleitungslänge konnte ermittelt werden.
Verglichen mit AlN-basierten Resonatoren verbesserte sich die Kopplung um bis zu 500 % bei x = 0,41. Eine derartige Steigerung erklärt sich durch die erwähnte Veränderung der Al1–xScxN Materialparameter e33 und C33 mit der Sc Konzentration x. Die elastischen Eigenschaften beeinflussen außerdem die Resonanzfrequenz, die bei steigendem x leicht abnimmt. Nach bestem Wissen der Autorin wurde eine solche systematische Untersuchung von SAW-Resonatoren auf der Basis von Al1-xScxN mit x = [0; 0,41] noch nicht durchgeführt erledigt. Darüber hinaus wurde nur eine Studie über die Leistung von SAW-Resonatoren basierend auf Al1–xScxN mit x berichtet, die so knapp unterhalb der Grenze liegt (x = 0,43), bei der das Material beginnt kubische Kristallite zu bilden.
Es ist darüber hinaus das erste Mal, dass hochqualitative a-plane AlScN Dünnschichten hergestellt wurden. Für a-plane Al0,77Sc0,23N wurde eine Steigerung der Kopplung um bis zu 1000 % im Vergleich zu c-plane Al0,77Sc0,23N-basierten Resonatoren festgestellt. Dies könnte durch die teilweise parallele Ausrichtung des von den IDTs ausgehenden elektrischen Feldes mit der polaren Achse zusammenhängen. Weiterhin wurde beobachtet, dass die Kopplung von a-plane AlScN-basierten Resonatoren stark von der Orientierung auf der Waferoberfläche abhängt. Der höchste Wert lag 1200 % über dem niedrigsten Wert und wurde bei einer Abweichung von ±30° von der wahrscheinlichen Ausrichtung der c-Achse beobachtet. Die könnte sich durch einen zusätzlichen Beitrag von e15 und C44 erklären lassen.
Der Wechsel von c-plane zu a-plane geht mit einer Veränderung der optimalen Resonatorwellenlänge einher, bei der der höchste positive Einfluss von e33 und C33 auf die Kopplung erzielt wird. Die veränderten Bestwerte für Kopplung in Abhängigkeit der Wellenlänge erlauben die Abdeckung des Frequenzbereichs von 1,14 bis 1,71 GHz bei einer Kopplung von 3,7 bis 4,1 %. Darüber hinaus kann auf Grundlage der beobachteten Trends der Frequenzbereich zu beiden Seiten hin erweitert werden und eine höhere Kopplung kann ebenfalls erreicht werden. Selbst Frequenzen von 2,05 GHz, bzw. 2,87 GHz wurden bei einer Kopplung von etwa 2,8 % erreicht, wenn die zweite Ordnung von Oberflächenwellenmoden auf a-plane, bzw. c-plane Al0,68Sc0,32N-basierten Resonatoren untersucht wurde.
Die Beständigkeit der Resonatoren über die Zeit und bei thermischer Beanspruchung wurde ebenfalls untersucht. Der Temperaturkoeffizient der Frequenz (engl. temperature coefficient of frequency - TCF) von Resonatoren mit einer Wellenlänge von 2 µm steigt in den Untersuchungen nicht-linear, allerdings nur leicht um 6,8 % mit x von 0 nach 0,32. Die experimentell bestimmten Verläufe der Phasengeschwindigkeit und Kopplungsdispersion wurden zur Ableitung der elastischen und piezoelektrischen Materialparameter der gewachsenen Al1–xScxN Dünnschichten herangezogen. Aufbauend auf diesen Parametern wurden Simulationen der Resonatoren durchgeführt. Die erzielten Ergebnisse verbessen das Verständnis, wie das temperaturabhängige Verhalten der Materialien die Resonanzfrequenz beeinflusst. Auf diese Weise können das Design und die Modelle zur Simulation von SAW Resonatoren mit komplexem Schichtaufbau weiter optimiert werden. Zum ersten Mal wurde der intrinsische SAW TCF von Al1–xScxN bestimmt und das Ergebnis wird die Weiterentwicklung der Technologie zur Kompensation von Temperatureffekten in Resonatoren vorantreiben. Dies ist von großer Bedeutung für heutige Smartphones, bei denen einzelne Komponenten im Inneren eine Temperatur von bis zu 90 °C erreichen können. Die Konsistenz der erzielten Ergebnisse der hohen Kopplung mit dem aktuellen Stand der Technik, sowie die thermische und dauerhafte Beständigkeit der Resonatoren spiegeln die Robustheit der hier entwickelten Technologie zur Abscheidung von AlScN Dünnschichten und der Herstellung von SAW Resonatoren wider.
Wie bereits erwähnt, muss die Kopplung im Resonator ungefähr doppelt so groß wie die relative Bandbreite der RF-Filter und der anvisierten Frequenzbänder sein. Die vorgestellten Ergebnisse zeigen, dass die hergestellten SAW Resonatoren die Anforderung für RF-Filter für drei 5G Bänder (n51, n70 und n76) erfüllen könnten, von denen zwei bereits für eine Nutzung in Nordamerika vorgesehen sind.
... The SAW velocity is an inherent property of the substrate, and the resonant frequency is determined by the finger pitch and wave velocity. IDT devices are most commonly used in wireless network systems [1][2][3][4][5][6] and acousto-optic technologies. [7][8][9][10][11] These SAW-based devices have also found significant use as bio, 12 gas, 13,14 pressure, 15,16 and temperature 17,18 sensors as well as actuators, pumps, and mixers in microfluidic applications. ...
Surface acoustic wave devices have been fabricated on a GaAs 100 substrate to demonstrate the capability of 2D Raman microscopy as an imaging technique for acoustic waves on the surface of a piezoelectric substrate. Surface acoustic waves are generated using a two-port interdigitated transducer platform, which is modified to produce surface standing waves. We have derived an analytical model to relate Raman peak broadening to the near-surface strain field of the GaAs surface produced by the surface acoustic waves. Atomic force microscopy is used to confirm the presence of a standing acoustic wave, resolving a total vertical displacement of 3 nm at the antinode of the standing wave. Stress calculations are performed for both imaging techniques and are in good agreement, demonstrating the potential of this Raman analysis.
... Surface acoustic wave (SAW) scattering due to gratings (electrodes, grooves, or strips) in the propagation path has long been a key scientific problem in SAW fields [1][2][3][4][5]. Wave reflection has extensive applications in fabricating acoustoelectric devices such as resonators [6,7], filters [8], and SAW reflective delay line devices [9], which are used for wireless communication field [10], wireless passive sensing [11] or radio frequency identification (RFID) [12,13]. Because of increasingly rigorous requirements on device performances, accurate computation of scattering fields that arise from the interaction of SAW with gratings used as either inter-digital transducers (IDTs) or reflective structures (Bragg reflectors) is of great importance [2,[14][15][16][17]. ...
In this paper, we investigate numerically the coupling of the Rayleigh mode with the micro-wall resonance modes in inter-digital transducers (IDTs) electrodes of surface acoustic wave (SAW) devices. We perform a finite element analysis (FEA) of the SAW features using an implemented model using COMSOL Multiphysics® software. The SAW structure comprises identical transmitter and receiver IDTs electrodes, with different electrode heights (he). The proposed FEA study is based on the extraction of reflection (S11) and transmission (S21) coefficients of the SAW device. The IDTs are considered to be a micro-wall phononic crystal acting as local resonators at frequencies inside the SAW passband. The locally resonance gap is strongly dependent on the he value, S11 and S21 parameters are affected by the SAW energy absorption in the IDTs system. We have chosen two he values (0.5 and 3 µm) to study low and high aspect ratios of micro-walls; corresponding respectively to Bragg-type and resonance-type bandgaps appearing near to the SAW central frequency. At the SAW resonance frequency, the return (S11) and the insertion (S21) losses are reduced. S21 is reduced by 12.73 and 18.49 dB for he=0.5 and 3 µm, respectively, accompanied by an increase in the quality factor, and S11 parameter is reduced by 1.357 and 4.98 dB for he=0.5 and 3 µm, respectively.
... Slanted IDTs have been widely employed in the field of data terminals as wide-band filters [24]. More recently, slanted IDTs have been adopted as an efficient acoustical tool for droplet microfluidics manipulation [25]. ...
... So wird ein 5G fähiges Endgerät bis zu 100 Filter im seinem HF-Front-End verbaut haben [14]. Die Kombination aus guten Leistungsmerkmalen und geringer Grundfläche machen mikroakustische Filter zur bevorzugten Wahl für den Einsatz in mobilen Endgeräten [12,13,[15][16][17]]. von R p und f Rs P von R S sind gleich. ...
Piezoelektrische mikroakustische Hochfrequenzfilter werden in der Empfangs- und Sendeelektronik von mobilen Endgeräten aufgrund ihrer geringen Baugröße sowie hohen Gütefaktoren bevorzugt verbaut. Derzeit etablierte Materialien wie Aluminiumnitrid oder Lithiumniobat sind nur begrenzt für den Einsatz in Hochfrequenzfiltern der nächsten Mobilfunkgeneration - 5G - geeignet.
Dies bedingt den Bedarf an neuartigen piezoelektrischen Dünnschichten.
Aluminium-Scandium-Nitrid (AlScN) weist eine deutlich gesteigerte elektromechanische Kopplung im Vergleich zu Aluminiumnitrid auf. Daher ist AlScN ein vielversprechender Kandidat für den Einsatz in mikroakustischen Hochfrequenzfiltern der nächsten Mobilfunkgeneration. Bisherige Forschungen beschäftigten sich hauptsächlich mit der Herstellung und grundlegende Charakterisierung von Schichten und Bauelementen. Für die Entwicklung von kommerziellen Bauelementen wird jedoch ein vollständiger Satz an elektro-akustischen Materialparametern benötigt. Ziel dieser Arbeit ist es, zum ersten Mal einen vollen Satz an elektro-akustischen und pyroelektrischen Materialparametern allumfassend experimentell zu bestimmen. Dadurch soll der Weg zu neuartigen Bauelementen auf Basis von AlScN eröffnet werden.
In dieser Arbeit wurden AlScN-Dünnschichten mit einer Dicke von etwa 1 μm Dicke
und Sc-Konzentrationen zwischen 0% und 42% untersucht. Die Schichten wurden mittels reaktivem Magnetronsputtern auf Siliziumsubstrate aufgebracht und wiesen eine hochgradig c-achsenorientierte Fasertextur auf. Mittels Röntgenbeugung wurden Phasenanalysen durchgeführt, die Gitterparameter gemessen und die Dichte bestimmt. Das bereits beobachtete untypische Verhalten der Gitterparameter als Funktion des Scandiumgehalts, konnte durch eine tiefgreifende Analyse auf das Absinken des mittleren Bindungswinkels bei gleichzeitigem Anstieg der mittleren Bindungslänge zurückgeführt werden. Trotz der nichtlinearen Änderung der Gitterparameter stieg die Dichte beinahe linear an.
Die dielektrische Permittivität wurde aus der Kapazität von Dünnschichtplattenkondensatoren ermittelt. Für die Bestimmung der elastischen und piezoelektrischen Eigenschaften wurden zwei Ansätze verfolgt. Im ersten Ansatz wurden die Materialparameter aus
Dispersionen von akustischen Oberflächenwellenresonatoren bestimmt. Dazu wurden zunächst Dünnschicht-Oberflächenwellenresonatoren mit Wellenlängen zwischen 2 μm und 24 μm hergestellt und jeweils die serielle und parallele Resonanzfrequenz bestimmt. Die eigentliche Extraktion der elastischen und piezoelektrischen Materialparameter ergab sich durch Abgleich von experimenteller und simulierter Dispersion anhand einer Parameteranpassung
eines Finite Elemente Methode Modells. Der zweite Ansatz basierte auf
akustischen Volumenwellenresonatoren. Dazu wurden Balken- und Scheiben-Resonatoren mit einer Länge von 200 μm, 250 μm und 300 μm bzw. mit Radien von 50 μm, 60 μm, und 70 μm hergestellt und die Resonanzfrequenzen extrahiert. Die seriellen und parallelen Resonanzfrequenzen der Resonatoren hängen nur von wenigen Materialparametern ab. Dadurch erlaubt es dieser Ansatz, die elastischen und piezoelektrischen Materialparameter mathematisch eindeutig und mit hoher Genauigkeit zu extrahieren. Wie bereits beim ersten Ansatz wurden die Materialparameter anhand einer Parameteranpassung eines Finite Elemente Methode Modells bestimmt. Der Vergleich der mit den beiden Ansätzen
ermittelten Materialparametern ergab sowohl untereinander als auch mit Literaturwerten eine gute Übereinstimmung.
Der effektive pyroelektrische Koeffizient als Funktion der Scandiumkonzentration und der Temperatur wurde mithilfe der dynamischen Sharp-Garn-Methode bei niedrigen Frequenzen von 10 mHz gemessen. Aus dem effektiven pyroelektrischen Koeffizienten konnten die intrinsischen pyroelektrischen Koeffizienten mithilfe der zuvor bestimmten elastischen und piezoelektrischen Materialparameter und den semi-experimentellen linearen Wärmeausdehnungskoeffizienten berechnet werden.
Eine nichtlineare Abhängigkeit der dielektrischen, elastischen und piezoelektrischen Materialparameter wurde beobachtet und bestätigte theoretische Vorhersagen von Berechnungen auf Basis der Dichtefunktionaltheorie. Abgesehen von c₁₃, sanken die Koeffizienten der elastischen Steifigkeit, wohingegen die polarisationsabhängigen Materialparameter, wie die dielektrische Permittivität, die piezoelektrischen und pyroelektrischen Parameter anstiegen, umso mehr Scandium in den Kristall eingebracht wurde. Es wurde betont, dass die relativen Änderungen von Materialparametern senkrecht zur polaren Achse signifikant schwächer ausgeprägt sind als solche parallel zur polaren Achse.
Um die anisotrope Natur von AlScN zu erklären, wurde ein Federmodell entwickelt, mit dem gezeigt wurde, dass die Änderungen in der Bindungsgeometrie primär die Entwicklung der Materialparameter als Funktion der Scandiumkonzentration bestimmt. Außerdem konnte das Modell den Anstieg der piezoelektrischen und pyroelektrischen Koeffizienten in Übereinstimmung mit bereits bestehenden Dichtefunktionaltheorie-Modellen erklären.
... In general, there are two main RF surface acoustic wave (SAW) filter configurations according to the connection type for mobile phone applications, namely, ladder-type and double-mode SAW (DMS) filters. (1)(2)(3)(4)(5)(6)(7)(8)(9) This version has been created for advance publication by formatting the accepted manuscript. Some editorial changes may be made to this version. ...
... A related issue of vital importance is noise generated by ferroelectric elements which has widespread applications. Ferroelectric materials are used as an insulating layer in the gate electrode of CMOS devices, 5 as a filter in the front end part of wireless devices, 6 and as data storage elements. 7 They are also used as actuator elements in scanning tunnelling microscopes, 8,9 atomic force microscopes, 10,11 and disk drives, 12 besides having a widespread use as sensors for infrastructure monitoring, 13,14 magnetic field sensing, 15 and related applications where extremely high sensitivity is necessary. ...
We present a novel analytical formulation on generation of electro-acoustic noise in ferroelectric materials where the thermal fluctuation induced polarization and acoustic modes distinctly contribute to noise. The conservative force fields associated with ferroelectric materials drive feedback of the spectral modes in the system. It results in symmetry breaking of the frequency spectrum of broadband noise, leading to enhancement of specific modes which generate high amplitude narrowband noise. We describe the process under the theoretical framework of fluctuation-dissipation theorem in the context of ferroelectric materials. We further note that such spectral feedback is absent in Johnson-Nyquist noise generation in conductors which have spectral symmetry.
... Thin film technology forms the core of current semiconductor industries. One important sector is the fabrication and development of electro-acoustic filters often used in modern mobile phones [1,2]. Many applications require an exact knowledge of film thicknesses in the nanometer range, as well as their respective sound velocities which depend on the strain inside the films. ...
Many applications of thin films necessitate detailed information about their thicknesses and sound velocities. Here, we study SiO2/LiNbO3 layer systems by picosecond photoacoustic metrology and measure the sound velocities of the respective layers and the film thickness of SiO2, which pose crucial information for the fabrication of surface-acoustic-wave filters for communication technology. Additionally, we utilize the birefringence and the accompanying change in the detection sensitivity of coherent acoustic phonons in the LiNbO3 layer to infer information about the LiNbO3 orientation and the layer interface.
... 11,12 In many on-chip devices, surface acoustic waves (SAWs) 8,13 are preferred against bulk acoustic waves (BAWs) 14 because they have better temporal/spatial accuracy and more efficient energy consumption 6 and are highly integrable. 15 The growth in acoustofluidic applications has attracted great interest for understanding how the movement of particles/cells could be precisely controlled. Objects in an acoustofluidic environment are generally subjected to the acoustic radiation force (ARF) and the drag force (DF) from fluid viscosity. ...
Acoustofluidic devices based on standing surface acoustic waves (SSAWs) have shown great potential in the manipulation of particles and cells. However, characterizing the acoustic field in a microchannel is difficult. This work introduces an analytical acoustophoretic model that shows that, by identifying the time period of particle rearrangement and the width of the eventually formed “particle strip,” acoustic pressure amplitude in a one-dimensional (1D) SSAW-actuated microchamber could be estimated quantitatively. Experiments are carried out with the help of a micro-PIV (PIV: particle image velocimetry) system, the results of which show that in-channel acoustic pressure is proportional to the square of voltage and the duty factor of an applied pulsed signal. This work links external excitation with acoustic pressure via only one parameter, i.e., the electroacoustic scaling factor. The method is simple and effective enough to serve as a candidate for standardizing 1D SSAW-based acoustofluidic devices.
... Table 2 presents the electrical characteristics (relative permittivity, relative permeability, dielectric loss, and resistivity) of different substrate materials for the capacitive RF MEMS capacitive switch. 17 ...
... SAW resonators are one or two port SAW devices [1][2][3][4] with performance related to Insertion loss, Quality factor and the resonant frequency [5]. ...
... Surface Acoustic Wave (SAW) filters have conquered one application after another over the past 30 years, first in TV sets and later in mobile phones [1]. Since SAW filters have a superior filter functionality and a small size, they play an important role in the evolution of mobile phones. ...
Surface Acoustic Wave (SAW) filters are key components of mobile phones and TV sets. In SAW components mechanical waves propagate on the surface of a chip, so the package must provide a cavity. Solid materials on the chip would inhibit the propagation of the surface waves. Reduction of size and cost, improved reliability and electrical performance are the main trends of SAW component evolution. In the past SAW filters were exclusively soldered directly on the PCBs. Now more and more filters are integrated in modules, which are often packaged by a transfer molding process. So the ability to withstand pressures up to 100 bars was added to the list of requirements. In this paper the SAW package evolution from packages using bonded wires to flip chip packages is reviewed. Our new SAW package developments for single SAW filters, 2in1 filters and duplexers using HTCC or LTCC interposers are presented.
Surface acoustic wave devices are key components for processing radio frequency signals in wireless communication because these devices offer simultaneously high performance, compact size and low cost. The optimization of the device structure requires a quantitative understanding of energy conversion and loss mechanisms. Here we use stroboscopic full-field diffraction x-ray microscopy to reveal an unanticipated acoustic loss in a prototypical one-port resonator device. A non-uniform acoustic excitation in the active area was responsible for the substantial end and side leakages observed at the design frequency. Quantitative analysis of the strain amplitude using a wave decomposition method allowed the determination of several key device parameters. This high-resolution high-throughput spatiotemporal strain imaging technique is more generally applicable to the study of dynamic strain modulation in nanoscale acoustic, electronic, optical and quantum devices. The high sensitivity allows precise measurement of the strain modulation with picometer-scale amplitude.
In Brillouin and Raman lasers, light is amplified by an input pump light through the excited acoustic and molecular oscillations in a medium. However, can medium oscillations alone amplify light in a realistic photonic circuit? Here, we demonstrate that modulating an optical resonator by a traveling wave having a frequency and phase velocity much smaller than the frequency and phase velocity of light can result in dramatically large narrow-band light amplification. Our calculations show that the proposed light amplifier can be realized in a lithium niobate racetrack resonator with millimeter-scale perimeter modulated by a surface acoustic wave with a surprisingly small amplitude and with the propagation constant satisfying the Brillouin phase matching condition.
Magnetic straintronics made its debut more than a decade ago as an extremely energy-efficient paradigm for implementing a digital switch for digital information processing. The switch consists of a slightly elliptical nano-sized magnetostrictive disk in elastic contact with a poled ultrathin piezoelectric layer (forming a two-phase multiferroic system). Because of the elliptical shape, the nanomagnet’s magnetization has two stable (mutually antiparallel) orientations along the major axis, which can encode the binary bits 0 and 1. A voltage pulse of sub-ns duration and amplitude few to few tens of mV applied across the piezoelectric generates enough strain in the nanomagnet to switch its magnetization from one stable state to the other by virtue of the inverse magnetostriction (or Villari) effect, with an energy expenditure that is roughly an order of magnitude smaller than what it takes to switch a modern-day electronic transistor. That possibility, along with the fact that such a switch is non-volatile unlike the conventional transistor, generated significant excitement. However, it was later tempered by the realization that straintronic switching is also extremely error-prone , which may preclude many digital applications, particularly in Boolean logic. In this perspective, we offer the view that there is plenty of room for magnetic straintronics in the analog domain, which is much more forgiving of switching errors, and where the excellent energy-efficiency and non-volatility are a boon. Analog straintronics can have intriguing applications in many areas, such as a new genre of aggressively miniaturized electromagnetic antennas that defy the Harrington limits on the gain and radiation efficiency of conventional antennas, analog arithmetic multipliers (and ultimately vector matrix multipliers) for non-volatile deep learning networks with very small footprint and excellent energy-efficiency, and relatively high-power microwave oscillators with output frequency in the X-band. When combined with spintronics, analog straintronics can also implement a new type of spin field effect transistor employing quantum materials such as topological insulators, and they have unusual transfer characteristics which can be exploited for analog tasks such as frequency multiplication using just a single transistor. All this hints at a world of new possibilities in the analog domain that deserves serious attention.
Surface acoustic wave (SAW) technology has been extensively used in communications and highly sensitive sensing applications. For SAW based gas sensing applications, the sensitive material or sensing layer which is...
This article presents a comprehensive study of the performance of Sezawa surface acoustic wave (SAW) devices in SweGaN QuanFINE ultrathin GaN/SiC platform, reaching frequencies above 14 GHz for the first time. Sezawa mode frequency scaling is achieved due to the elimination of the thick buffer layer typically present in epitaxial GaN technology. Finite element analysis (FEA) is first performed to find the range of frequencies over which the Sezawa mode is supported in the grown structure. Transmission lines and resonance cavities driven with interdigital transducers (IDTs) are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics. We observe a strong correlation between measured and simulated dispersion of the phase velocity (
) and piezoelectric coupling coefficient (
). Maximum
of 0.61% and frequency-quality factor product (
) of
are achieved for Sezawa resonators at 11 GHz, with a minimum propagation loss of 0.26 dB/
for the two-port devices. Sezawa modes are observed at frequencies spanning up to 14.3 GHz, achieving a record high in GaN microelectromechanical systems (MEMS) to the best of the authors’ knowledge.
Cooling of quartz-SAW devices leads to a noticeable increase in sensitivity. However, the effect of heating on the output characteristics of quartz-SAW resonators in terms of sensitivity has not yet been studied. Here we examine the inverse parabolic temperature characteristics of a quartz-SAW resonator in order to study the effect of temperature rise on the sensitivity. Various characteristics of a quartz SAW resonator are measured such as frequency shifts, phase, and group delay by Vector Network Analyzer (VNA) over a temperature range of 5 °C to 150 °C. It is shown that the sensitivity could be increased at certain combinations when the operating frequency (fo) is tuned away from the centre frequency (fc) along with temperatures higher or lower than room temperature. Sensitivity increases up to 24-fold was achieved when T > 120 °C and fo > fc. This study of temperature tuning of SAW device will be useful for enhancing the sensitivity in various SAW sensing applications for various industrial purposes.
This work presents the first investigation of the SweGaN QuanFINE ultrathin GaN-on-SiC platform for the performance of surface acoustic wave (SAW) devices over 14 GHz. Frequency scaling is made possible by the absence of a thick buffer layer typical in epitaxial GaN technology. After finite element analysis (FEA) simulation to identify acoustic modes, SAW devices were designed, fabricated, and characterized. Measurements from one-port interdigital transducers (IDTs), two-port delay lines, and one-port resonators were fitted with modified Mason and Butterworth-Van-Dyke (BVD) models. Extracted piezoelectric coupling coefficient (k^2 ) matches well with simulation for the IDTs with the highest value of 0.53% at 11.1 GHz. Maximum Qm of 542 and f.Qm product of 6×10^12 are achieved for the resonators at the same frequency with a propagation loss of 0.08dB/λ. Sezawa modes up to 14.3 GHz are observed, a record high in GaN MEMS to the best of the authors' knowledge.
This paper presents a short review of the microwave acoustics area, where exciting material innovations and performance advancements have been made in the past decade. The ever-growing demand for more sophisticated passive signal processing functions on-chip has fueled these developments. As a result, microwave acoustic devices have maintained performance leadership in mobile applications. By evaluating three fundamental parameters, namely electromechanical coupling (
k
2
), quality factors, and frequency scalability, of microwave acoustics, this paper aims to, extensively but not exhaustively, capture the rationales behind approaches achieving higher performance microsystems. Outlooks for different material systems and addressing their underlying challenges are also offered in hopes of establishing a balanced roadmap for future microwave acoustics development.
Surface acoustic waves (SAWs) are used in a broad range including electronic systems and various sensors. Especially, SAW‐based microfluidic actuations at microscale represent an effective way with unrivaled precision and technological relevance. However, it remains a daunting challenge to develop a reliable and robust method for in situ and real time probing of the acoustic propagation of SAWs. Approach‐based sophisticated equipment claims large consumption and fussy operation, and is also limited for rapid analysis inside microfluidic channels. Other emerging methods suffer from limitations associated with the reproducibility or the application scenarios. Here, a convenient approach is achieved by interfacing with lanthanide emitters. The coupling between ferroelectric host and lanthanide ions promises effective emission manipulation upon external stimuli induced by the SAWs. The photoluminescence fluctuations of lanthanide emitters reflect their interaction with the strain and piezoelectric fields accompanying the propagating SAWs. The strong correlation between the lanthanide luminescence and the acoustic fields can visualize the resonant frequency, energy flow as well as propagation loss of the propagating SAWs on demand without degrading the SAW‐based functionality. These findings would accelerate the development of SAW‐based devices owing to the added functionality provided by the SAW‐luminescence correlative character.
We investigate surface-acoustic-wave- (SAW) induced ferromagnetic-resonance- (FMR) assisted spin-transfer-torque (STT) switching of perpendicular magnetic tunnel junctions (PMTJs) with inhomogeneities using micromagnetic simulations that include the effect of thermal noise. With suitable frequency excitation, the SAW can induce ferromagnetic resonance in magnetostrictive materials, and the magnetization can precess in a cone with high deflection from the perpendicular direction. With incorporation of inhomogeneity via lateral anisotropy variation as well as room-temperature thermal noise, the magnetization precession in different gains can be significantly incoherent. Interestingly, the precession in different grains are found to be in phase, even though the precession amplitude (angle of deflection from the perpendicular direction) varies across grains of different anisotropy. Nevertheless, the high mean deflection angle due to acoustically induced FMR can complement the STT switching by reducing the STT current significantly; even though the applied stress induced change in anisotropy is much lower than the total anisotropy barrier. This work indicates that SAW-induced FMR-assisted switching can improve energy efficiency while being scalable to very small dimensions, which is technologically important for STT random-access memory and elucidates the physical mechanism for the potential robustness of this paradigm in realistic scenarios with thermal noise and material inhomogeneity.
Optomechanical properties have been explored widely on the interactions between phonon, photon and electrons. The applications range from acoustic filters for mobile handsets to quantum information science. However, up to date, the interaction between harmonic modes of surface acoustic waves and photons hasn’t been studied in detail. Here, we develop radio frequency (RF) modulated light emitters driven by the coupling between of electrical and acoustic signals at room temperature. The light emitter demonstrates a 990 MHz oscillation behavior which can’t be achieved solely by electrical driving due to resistance-capacitance (RC) limit. Instead, the result is attributed to the excitation by the harmonics of surface acoustic waves in the light emitter. The ∼GHz light oscillation enables a new architecture for information processing. In this work, we also demonstrate coupling between acousto-optical and electro-optical interactions by simultaneously applying 990 MHz acoustic signals and 20 MHz modulated electrical inputs.
The manipulation of cells and microparticles within microfluidic systems using external forces is valuable for many microscale analytical and bioanalytical applications. Acoustofluidics is the ultrasound-based external forcing of microparticles with microfluidic systems. It has gained much interest because it allows for the simple label-free separation of microparticles based on their mechanical properties without affecting the microparticles themselves.
Microscale Acoustofluidics provides an introduction to the field providing the background to the fundamental physics including chapters on governing equations in microfluidics and perturbation theory and ultrasound resonances, acoustic radiation force on small particles, continuum mechanics for ultrasonic particle manipulation, and piezoelectricity and application to the excitation of acoustic fields for ultrasonic particle manipulation. The book also provides information on the design and characterization of ultrasonic particle manipulation devices as well as applications in acoustic trapping and immunoassays.
Written by leading experts in the field, the book will appeal to postgraduate students and researchers interested in microfluidics and lab-on-a-chip applications.
The propagation of surface acoustic waves (SAWs) in two-dimensional phononic crystals (PnCs) with and without coupling-enhancement slabs was theoretically investigated using a three-dimensional finite element method. Different piezoelectric substrates, for example, lithium niobate (LiNbO3), gallium nitride (GaN), and aluminium nitride (AlN), were taken into account. Compared to the PnCs without coupling-enhancement slabs, the coupling between each pillar and its nearest neighbor was largely enhanced in the presence of slabs. The bandwidth of the first directional band gap increased markedly compared with its initial value for the PnCs without a slab (within square symmetry). In addition, with increasing thicknesses of the slabs bonded between neighboring pillars, the first directional band-gap and second directional band gap of the PnCs tend to merge. Therefore, the structure with coupling-enhancement slabs can be used as an excellent electrical band elimination filter for most electro-SAW devices, offering a new strategy to realize chip-scale applications in electroacoustic signal processing, optoacoustic modulation, and even SAW microfluidic devices.
Surface acoustic waves are used in magnetism to initiate magnetization switching, in microfluidics to control fluids and particles in lab-on-a-chip devices, and in quantum systems like two-dimensional electron gases, quantum dots, photonic cavities, and single carrier transport systems. For all these applications, an easy tool is highly needed to measure precisely the acoustic wave amplitude in order to understand the underlying physics and/or to optimize the device used to generate the acoustic waves. We present here a method to determine experimentally the amplitude of surface acoustic waves propagating on Gallium Arsenide generated by an interdigitated transducer. It relies on Vector Network Analyzer measurements of S parameters and modeling using the Coupling-Of-Modes theory. The displacements obtained are in excellent agreement with those measured by a very different method based on X-ray diffraction measurements.
We report the comparison of electrode metals for LiNbO3 surface acoustic wave (SAW) devices. Palladium (Pd) was systematically studied as a SAW electrode metal for the first time, compared with gold (Au). Simulations were first conducted to gain an understanding of the differences of the materials and the metallization ratio. Two sets of identical SAW devices were then fabricated using Au and Pd as electrodes with different electrode widths and same SAW period. The insertion losses, types of resonance mode, the resonance frequencies, peak amplitudes, quality factors and trends with different metallization ratios were systematically compared and analyzed. We found that Pd electrode devices only exhibit the parallel resonance frequency and have higher resonance frequency for both the first-order and third-order harmonics. Au electrode devices tend to have a smooth response and a quality factor two times higher than Pd. Both Pd and Au electrode devices have nearly identical electromechanical coupling coefficients, and the quality factor and third-order harmonics both improve with increasing metallization ratio.
Surface acoustic wave(SAW)transducers are a well-established component used in numerous sensors, communications, and electronics devices. In this work, the authors report a systematic study of 320–800 nm period lithium niobate SAWinterdigitated transducers(IDTs) corresponding to resonant frequencies in the 4–12 GHz range. An optimized SAW design and a nanofabrication process flow were developed, which enabled superior device performance in terms of frequency, signal losses, and electromagnetic coupling. The influence of the device alignment on the substrate crystal planes, in addition to the IDT period and electrode design, is found to have a significant impact on various process metrics. As an example, two identical SAW transducers fabricated perpendicular to each other may have a resonant frequency difference approaching 1 GHz, for the same harmonic mode. These and other trends are presented and discussed.
CMOS integration for RF-MEMS is desired to yield compact, low-power and portable devices. In this work, we illustrate the usage of double electrode CMOS SAW resonators using both ZnO and AlN as its piezoelectric material. Double electrode transducers were chosen, as they are better at suppressing undesired acoustic reflections compared to single electrodes. The structure and dimension of the device is based on 0.35 μm CMOS process where the IDTs are fabricated using standard CMOS fabrication process. 2D Finite element modeling of the CMOS SAW resonator using COMSOL Multiphysics® is presented. Two-step eigenfrequency and frequency domain analyses were performed. The acoustic velocities generated are 3,925 and 5,953 m/s for ZnO and AlN CMOS SAW resonator respectively. Higher acoustic displacement and surface potential were observed in ZnO compared to AlN. It can be concluded that ZnO thin films have higher electromechanical coupling coefficients and are more efficient than AlN thin films.
Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films.
S.V. Biryukov YU.V. Gulyaev
V.V. Krylov V.P. Plessky
Surface Acoustic Waves
in Inhomogeneous Media
With 138 Figures and 5 Tables
Springer-Verlag Berlin Heidelberg Gmbh
"...
The book deals with traditional and new methods of theoretical analysis
of the mechanisms of propagation of surface acoustic waves in inhomogeneous
solids. The processes of scattering, reflection and transformation of waves
by local and periodic discontinuities of various types, as well as SAW waveguides,
are considered. The propagation of SAW on smooth surfaces of variable curvature and their scattering at the boundaries of wedge-like regions are examined.
Certain aspects of the effect of random irregularities on surface wave
propagation are touched upon. The book on the whole is of a theoretical nature;
however, the relevant experimental investigations are described as well.
The book, which represents a shortened and corrected version of the
first Russian edition, is based to a large extent on original works by the
authors although the results in this field obtained by other investigators are
also included; this helps to treat the problem under consideration all the more
fully. Chapters I, 2, 6-8 have been written jointly by Yu. V. Gulyaev and
V. P. Plessky, Chaps. 3-5, II, 14, by S. V. Biryukov, and Chaps. 9, 10, 12,
13, 15, by V. V. Krylov. All chapters of the book are mutually independent to
a large extent and can be read in an arbitrary order. ..."
Surface acoustic wave (SAW) devices can be used as identification and sensor elements (SAW transponders) for measuring physical quantities such as temperature, pressure, torque, acceleration, humidity, etc., that do not need any power supply and may be accessed wirelessly. The complete wireless sensor system consists of such a SAW transponder and a local radar transceiver. An RF burst transmitted by the radar transceiver is received by the antenna of the SAW transponder. The passive transponder responds with an RF signal-like a radar echo-which can be received by the front-end of the local transceiver. Amplitude, frequency, phase and time of arrival of this RF response signal carry information about the SAW reflection and propagation mechanisms which in many cases can be directly attributed to the sensor effect for a certain measurand. Usually no intersymbol interference (ISI) due to environmental echoes occur, due to the high delay time of the SAW transponder in the order of some fj,s. The present work reviews the operating principles of such sensor systems and their state-of-the-art performance by way of some examples which include the wireless measurement of temperature, pressure, torque, acceleration, tire-road friction, magnetic field, and water content of soil.
An overview of surface acoustic wave (SAW) filter techniques available for different applications is given. Techniques for TV IF applications are outlined, and typical structures are presented. This is followed by a discussion of applications for SAW resonators. Low-loss devices for mobile communication systems and pager applications are examined. Tapped delay lines (matched filters) and convolvers for code-division multiaccess (CDMA) systems are also covered. Although simulation procedures are not considered, for many devices the theoretical frequency response is presented along with the measurement curve.< >
An inexpensive frequency-modulated continuous-wave (FMCW) radar
system is presented in this paper, which, nevertheless, meets all
industrial requirements. The FMCW radar uses a low-cost nonlinear
voltage-controlled oscillator (VCO), operating at an IF of 2.45 GHz to
generate the frequency modulation of the radar system. This VCO signal
is applied twice, first to generate the radar transmitter signal at 24
GHz, and then it is fed to a surface acoustic wave (SAW) delay line. The
SAW delay line generates a fixed delay time, which corresponds with a
fixed radar distance. Thus, all systematic nonlinearities and stochastic
phase errors of the FMCW system can be monitored and, afterwards, can be
compensated for in real time. This linearization technique leads to a
significant enhancement in dynamic range for a FMCW radar system. For
this FMCW system, SAW delay lines with a linear phase characteristic
have been designed using a linear optimization program. The delay line
consists of two chirped and weighted interdigital transducers. For high
volume, low-cost, and high-yield production of the required SAW
structures, with linewidths down to 0.3 μm, technological
improvements had to be achieved, especially in photolithography. Based
on these design and fabrication techniques, delay lines at 2.45 GHz
operating at the fundamental and third harmonic with bandwidths up to
800 MHz have been realized
Design and performance of a low-cost wireless communication system
for indoor and industrial environments are presented. The system is
based on chirp-signal transmission to achieve a robust communication
link. For the chirp expansion and compression, surface acoustic wave
chirped delay lines fabricated from LiTaO3-X112rotY are used.
Center frequency, bandwidth, and chirp rate are 348.8 MHz, 80 MHz, and
±40 MHz/μs, respectively. An optimized square-root weighting
was chosen to reduce the sidelobes of the compressed pulse to -42 dB
compared to the correlation peak. The chirp filters have been deployed
in a hardware demonstrator for data rates of up to 5 Mb/s. Limiting
factors for the data rate according to simulations and measurements are
mainly intersymbol interferences due to the time overlapping of
consecutive symbols and, to a lower extent, the multipath propagation
Surface acoustic waves can be generated at the free surface of an elastic solid. This phenomenon has been exploited for electronic analog signal processing over the past 30 years, with the development of a host of devices and systems for consumer, commercial and military applications running at a some hundred million dollar annual rate. The objective of this paper is to provide an overview of the latest developments in the surface acoustic wave (SAW) field and to identify upcoming applications in remote sensing and communications. It. is intended to address some of the key issues in the successful design and manufacture of SAW devices and to discuss the operating principles from a microwave design viewpoint.
This chapter deals with the impedance method for analysing surface waves in inhomogeneous piezoelectric structures. This analysis is based on the following arguments. We do not construct wave field solutions in the whole inhomogeneous structure by joining these fields on boundaries of irregularity, but consider only the fields on a certain convenient plane and describe the half-spaces (bordering this plane) by surface impedance matrices; the form of these matrices is defined not only by the medium character, but also by the properties of scattering inhomogeneities. This approach is quite natural because of the plane character of typical structures and allows us to split a complicated boundary-value problem of obtaining fields into two simpler independent problems: a problem of finding the surface impedances independent of fields and a problem of solving equations of motion on a plane with given impedances of adjusting half-spaces. And in this case a minimal number of variables is used for the description of both problems, and the problems themselves are posed in a compact form convenient for constructing both exact and approximate solutions by means of methods of perturbations.
To meet the increasing demand of high performance filters in GHz
radio communication systems, we have improved design techniques and
fabrication processes. Different types of filters in the range of 1 to 3
GHz, a 2.45 GHz resonator with 18 dB insertion attenuation and a quality
factor of 1500, wideband delay lines at 2.45 GHz, with 400 MHz and 600
MHz bandwidth, identification tags at 2.45 GHz, and ladder type bandpass
filters for PCS and WLAN applications at 1.9 GHz and 2.45 GHz, were
developed and manufactured. It will be shown, that these devices with
submicron linewidth transducers down to 0.3 μm can be manufactured
with tight process tolerances
New surface acoustic wave (SAW) convolver structures with high conversion efficiency and self-temperature compensation characteristics have been developed. Strong piezoelectric substrates, regardless of temperature coefficients of delay (TCD), can be used in these convolvers. New demodulation techniques using the developed SAW convolver for high bit rate and wideband spread spectrum code division multiple access (CDMA) communications have also been developed. I- and Q-channel demodulation data can be derived directly from binary phase shift keying (BPSK) or quadri-phase shift keying (QPSK) CDMA signals. In an experiment using a 128 degrees YX-LiNbO(3) substrate, CDMA signals of 9 Mbps (megabits per second) with 60 Mcps (megachips per second) spread by 13-chip Barker code and 11 Mbps with 140 Mcps spread by 25-chip Shiba's code were clearly demodulated, demonstrating the effectiveness of these techniques for use in future CDMA communications.
Apart from the active semiconductor chips a multitude of surface
acoustic wave filters (SAW filters) are the key components that make
modern RF circuits for mobile telecommunication and multimedia
applications work. The latter are the most sophisticated and delicate
species of passive components of which today's RF applications contain
several hundred. While active integration has led to decreasing numbers
of semiconductors inside a phone, at the time being the passive
components outnumber the actives by far. Obviously, the highest
potential for further miniaturization lies in the passive components. As
the market asks for further miniaturized mobile phones and digital
tuners EPCOS tackles this challenge not only by further shrinking the
SAW filters but also by integrating additional functions into the SAW
filters which were originally not SAW related at all. This paper briefly
presents several applications for such highly miniaturized SAW filters
offering superior filter performance combined with additional features
like impedance transformation, balun functionality or double balanced
operation, allowing for smaller and cheaper designs by effectively
reducing PCB space as well as component count
Mobile market in Japan is rapidly growing as well as Europe, North
America and other countries. The major mobile phone system in Japan are
PDC (Personal Digital Cellular) and PHS (Personal Handy Phone System),
and the new service called cdmaOneTM has just started since
last year. And W-CDMA system is expected to start on 2001 as new
generation of mobile phone system in Japan. Since these system utilize
different communication method, the specifications of the intermediate
frequency (IF) filters for the systems are totally different from each
other and from that of European GSM and north American AMPS. In
addition, tiny and light mobile phone products are preferable in
Japanese market, the size of these IF SAW filters are shrinking year by
year. In this paper the technical outlines of IF SAW filter for mobile
phones in Japanese market and their recent trends will be described, and
also their future trend will be discussed
To meet the increasing demand of high performance filters in GHz
radio communication systems, we have improved the design techniques and
fabrication processes for SAW devices. The standard optical projection
printing technique based on i-line lithography used for mass-production
was optimized, thus attaining a linewidth of 0.3 microns. As a first SAW
device prototype we designed and fabricated a ladder type bandpass
filter from 42° rotYX-LiTaO3 substrate, at 3.15 GHz
having a bandwidth of close to 200 MHz and a minimum insertion loss of
1.7 dB
The phase velocity and the attenuation of surface acoustic waves
(SAW) are determined for Rayleigh waves on free and metallized quartz
substrates. The measurement setup and the evaluation procedure based on
the direct modeling of the phase for the transmitted signal are
discussed. The used method is compared to other evaluation techniques.
The results for the phase velocity are given and compared to theoretical
values determined with a boundary element method (BEM). Parameter values
for an improved model are extracted for the phase velocity as well as
for the attenuation. The model is applied to the simulation of
TCF-resonators and a comparison between experiment and simulation is
performed
Design and performance of SAW chirped delay lines on LiTaO3 -X112rotY for a wireless communication system are presented. Center frequency, bandwidth and chirp rate are 350 MHz, 80 MHz, and ±20 MHz/s, respectively. An optimized square-root weighting was chosen to reduce the sidelobes of the compressed pulse to -42 dB compared to the correlation peak. The chirp filters have been deployed in a hardware demonstrator for a wireless indoor communication system for data rates of a few Mbit/s. Limiting factors for the data rate according to simulations and measurements are mainly the intersymbol interference due to the time-overlapping of consecutive symbols and to a lesser extent the multipath propagation
The most frequently used models for surface acoustic wave (SAW) devices are the impulse model, the equivalent circuit models, the Coupling-of-Modes model, and the matrix models. While the impulse-model is only a first order model the other models include second order effects, e.g. reflections, dispersion, and charge distribution effects. The influence of diffraction and refraction on the transfer function of a SAW filter can be described by the angular spectrum of straight-crested waves model. A survey of these different models will be given. The simulation of low-loss filters requires flexible analysis tools, which can cope with different geometries and substrates. Operating with a parameter set, which depends only on the substrate crystal and not on the specific geometry of the SAW filter, is advantageous. Due to the high insertion attenuation of conventional transversal filters the requirements on the accuracy of the analysis are focused on S21, whereas for low-loss filters all elements of the S-matrix are important. The comparison of simulations with a P-matrix model, which fulfills the above mentioned prerequisites, and measurements of different types of low-loss filters, e.g. SPUDT, DMS, and transverse-mode coupled resonator filters are presented
To meet the increasing demand for high-performance filters in
gigahertz radio-communication systems, we have improved the design
techniques and fabrication processes for surface-acoustic wave (SAW)
devices. The standard optical projection printing technique based on
i-line lithography used for mass-production was optimized, thus
attaining a linewidth of 0.3 μm. As a first SAW device prototype, we
designed and fabricated a ladder-type bandpass filter from LiTaO<sub>3
</sub> substrates, at 3.15 GHz having a 3 dB-bandwidth of 128 MHz and a
minimum insertion loss of 1.7 dB
Efficient modeling of microacoustic structures in terms of electromagnetic field concepts
- Weigel
R. Weigel, "Efficient modeling of microacoustic structures in terms
of electromagnetic field concepts," in Proc. Int. Symp. Antennas and
Propagation, Chiba, Japan, 1996, pp. 897-900.
High performance SAW convolvers used in high bit rate and wideband spread spectrum CDMA communication systems
- M Hitica
- C Takubo
- K Assi
Surface acoustic waves in inhomogeneous media
- S V Biryukov
- Y V Gulaev
- V V Krylov
- V P Plessky
S.V. Biryukov, Y.V. Gulaev, V.V. Krylov, and V.P. Plessky, "Surface
acoustic waves in inhomogeneous media," in Springer Series on
Wave Phenomena 20. Berlin, Germany: Springer-Verlag, 1995.