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The past few decades have witnessed the ultra-fast development of wireless telecommunication systems, such as mobile communication, global positioning, and data transmission systems. In these applications, radio frequency (RF) acoustic devices, such as bulk acoustic waves (BAW) and surface acoustic waves (SAW) devices, play an important role. As the integration technology of BAW and SAW devices is becoming more mature day by day, their application in the physical and biochemical sensing and actuating fields has also gradually expanded. This has led to a profusion of associated literature, and this article particularly aims to help young professionals and students obtain a comprehensive overview of such acoustic technologies. In this perspective, we report and discuss the key basic principles of SAW and BAW devices and their typical geometries and electrical characterization methodology. Regarding BAW devices, we give particular attention to film bulk acoustic resonators (FBARs), due to their advantages in terms of high frequency operation and integrability. Examples illustrating their application as RF filters, physical sensors and actuators, and biochemical sensors are presented. We then discuss recent promising studies that pave the way for the exploitation of these elastic wave devices for new applications that fit into current challenges, especially in quantum acoustics (single-electron probe/control and coherent coupling between magnons and phonons) or in other fields.

This Research article document discussed about a new structure composed of a sub‐micron‐thick layer of a single‐crystal piezoelectric material on a substrate. Longitudinal waves are used for experimental demonstration with 4’’ collective processes. Electrical experimental–computation validate the concept with Q × f products near 1012. Microscope observation at the end of the collective process of one single‐port resonator with Bragg mirrors on the left and one single‐port resonator with vertical etched mirrors on the right.

Bird strikes are a major safety and financial concern for modern aviation. Audible stimuli are common bird dispersal techniques, but their effectiveness is limited by the saliency and relevance of the stimulus. Furthermore, high ambient sound levels present at airfields might require that effective audible stimuli rely more on total volume (i.e., exceeding physiological tolerances) than ecological relevance. Acoustic hailing devices (AHD) are capable of sound output with a narrow beam width and at volumes high enough to cause physical discomfort at long distances. We tested the effectiveness of an AHD as a dispersal tool on free-ranging birds recognized as hazardous to aviation safety at the Savannah River Site and Phinizy Swamp Nature Park in South Carolina and Georgia, USA, respectively, between October 2013 and March 2015. Our study design included experimental trials with timed-interval counts of birds directly before and after AHD treatment. For most species, counts of birds associated with treatment periods (use of AHD) and control periods (no use of AHD) occurred on different days. Sound treatments yielded variable success at dispersing birds. Specifically, AHD treatment was effective for dispersing vultures (Coragyps atratus and Cathartes aura) and gulls (Laridae), but ineffective for dispersing blackbirds (Icteridae), diving ducks (Aythya spp., Bucephala spp., Oxyura spp.), and coots (Fulica americana). Trials were conducted in a relatively quiet environment with birds that were unhabituated to excessive noise; thus, we cannot unequivocally recommend an AHD as a universally effective avian dispersing tool. However, future research should consider AHD testing integrated with other methods, as well as investigation of treatments that might be salient to specific target species.

AlN-based bulk acoustic wave (BAW) filters have emerged as crucial components in 5G communication due to their high frequency, wide bandwidth, high power capacity, and compact size. This paper mainly reviews the basic principles and recent research advances of AlN-based BAW resonators, which are the backbone of BAW filters. We begin by summarizing the epitaxial growth of single-crystal, polycrystalline, and doped AlN films, with a focus on single-crystal AlN and ScAlN, which are currently the most popular. The discussion then extends to the structure and fabrication of BAW resonators, including the basic solidly mounted resonator (SMR) and the film bulk acoustic resonator (FBAR). The new Xtended Bulk Acoustic Wave (XBAW) technology is highlighted as an effective method to enhance filter bandwidth. Hybrid SAW/BAW resonators (HSBRs) combine the benefits of BAW and SAW resonators to significantly reduce temperature drift. The paper further explores the application of BAW resonators in ladder and lattice BAW filters, highlighting advancements in their design improvements. The frequency-reconfigurable BAW filter, which broadens the filter’s application range, has garnered substantial attention from researchers. Additionally, optimization algorithms for designing AlN-based BAW filters are outlined to reduce design time and improve efficiency. This work aims to serve as a reference for future research on AlN-based BAW filters and to provide insight for similar device studies.

This article presents an investigation into the use of nanoscale phononic crystals (PnCs) as reflectors for surface acoustic wave (SAW) resonators, with a focus on pillar-based PnCs. Finite element analysis was employed to simulate the phononic dispersion characteristics and to study the effects of the pillar shape, material and geometric dimensions on achievable acoustic bandgap. To validate our concept, we fabricated SAW resonators and filters incorporating the proposed pillar-based PnC reflectors. The PnC-based reflector shows promising performance, even with smaller number of PnC arrays. In this regard, with a PnC array reflector consisting of 20 lattice periods, the SAW resonator exhibits a maximum bode-Q of about 1600, which can be considered to be a reasonably high value for SAW resonators on bulk 42° Y-X lithium tantalate (42° Y-X LiTaO3) substrate. Furthermore, we implemented SAW filters using pillar-based PnC reflectors, resulting in a minimum insertion loss of less than 3 dB and out-of-band attenuation exceeding 35 dB. The authors believe that there is still a long way to go in making it fit for mass production, especially due to issues related with the accuracy of fabrication. But, upon its successful implementation, this approach of using PnCs as SAW reflectors could lead to reducing the foot-print of SAW devices, particularly for SAW-based sensors and filters.

An injection‐locked divider oscillator that converts a 6‐GHz‐band signal into a 3‐GHz‐band signal was developed. The injection‐locked divider oscillator was specifically designed to lock on the clock transition frequency of 87Rb of 6.824 GHz to provide a laser modulation signal at 3.417 GHz for an on‐chip coherent population trapping atomic clock system. To obtain high frequency stability and low‐phase noise with low power consumption in the super‐high‐frequency band, a thin‐film bulk acoustic resonator is used instead of the conventional LC tank circuit. The fabricated oscillator operated well with a power consumption of 4.5 nW. The maximum lock range was 1.5% in fractional frequency. Also, unlike the conventional injection‐locked divider oscillator with an LC tank, the bifurcation of the lock range width was observed when sweeping the injection power of the 6‐GHz‐band signal, and in the down sweep, the locking operation was maintained even at an injection power of −20 dBm.

A novel enlarging fractional bandwidth (FBW) technique for acoustic‐wave‐lumped‐element resonator (AWLR)‐based bandpass filters is presented. The new technique is based on a series of matching inductors that replace the parallel or series acoustic wave (AW) resonators of AW filters to beak the bandwidth constraint of the ladder‐type structure. In addition, the transmission response analysis of the proposed AWLR‐based filter is provided. A prototype of the AWLR‐based filter is fabricated and tested to validate the proposed FBW widening technique. The measured insertion loss, FBW, and out‐of‐band rejection are 1.5 dB, 1.63kt2 (kt2 is the electromechanical coupling coefficient of the AWR), and 38 dB, respectively. A novel enlarging fractional bandwidth (FBW) technique for acoustic‐wave‐lumped‐element resonator (AWLR) ‐based bandpass filters is present. The new technique is based on a series of matching inductors that replace the parallel or series acoustic wave (AW) resonators of AW filters to beak the bandwidth constraint of the ladder‐type structure.

Three‐dimensional positioning in large indoor environments poses a significant challenge for achieving high‐precision 5G positioning. This letter proposes an indoor 5G differential positioning solution, which is constrained by the ranging measurements from a low‐cost audio anchor. The method first eliminates receiver and 5G base station clock biases using double‐differenced 5G time of arrival (ToA) and carrier phase observations. It then incorporates a single high‐precision audio range measurement. Extended Kalman filtering is employed to estimate the float solution, followed by a ratio test to validate the resolution of the ambiguity and obtain the fixed solution. When the 5G ToA accuracy is 0.4 m, the proposed method improves positioning accuracy by 44.4% under static conditions and 29.2% under dynamic conditions compared to using five 5G base stations, achieving a positioning accuracy of approximately 0.10 and 0.17 meters, respectively. Our findings further demonstrate that the audio constraints facilitate 5G carrier phase ambiguity resolution, thereby accelerating positioning convergence. This letter presents a comprehensive analysis of how high‐precision audio ranging significantly enhances the accuracy and ambiguity resolution of 5G carrier differential positioning, thereby offering a novel approach to indoor positioning.

The application of standing surface acoustic wave (SSAW) tweezers based on backpropagation superposition to achieve precise behavior manipulation of microscale cells and even nanoscale bacteria has been widely studied and industrialized. However, the structure requires multiple transducer components or full channel resonance. It is very challenging to design a simple structure for nano-control by complex acoustic field. In this study, a reflector-interdigital transducer (R-IDT) acoustofluidic device based on unilateral coherence enhancement is proposed to achieve SSAW definition features of periodic particle capture positions. The SAW device based on a unilateral transducer can not only generate leaky-SAW in water-filled microchannel, but also have a contribution of spherical waves in the vibration area of the substrate-liquid interface due to the Huygens-Fresnel diffractive principle. Both of them form a robust time-averaged spatial periodicity in the pressure potential gradient, accurately predicting the lateral spacing of these positions through acoustic patterning methods. Furthermore, a reflector based on Bragg-reflection is used to suppress backward transmitted SAW and enhance forward conducted SAW beams. By using a finite element model, R-IDT structure’s amplitude enhances 60.78% compared to single IDT structure. The particle manipulation range of the diffractive acoustic field greatly improves, verified by experimental polystyrene microspheres. Besides, biocompatibility is conformed through red blood cells and Bacillus subtilis. We investigate the overall shift of periodic pressure field that can still occur when the phase changes. This work provides a simpler and low-cost solution for the application of acoustic tweezer in biological cell culture and filtering.

Milk and dairy products are common foods and, therefore, are subject to regular controls. Such controls cover both the identification and quantification of specific components and the determination of physical parameters. Components include the usual milk ingredients, mainly carbohydrates, proteins, and fat, and any impurities that may be present. The latter range from small molecules, such as drug residues, to large molecules, e.g., protein-based toxins, to pathogenic microorganisms. Physical parameters of interest include viscosity as an indicator of milk gelation. Bulk and surface acoustic wave sensors, such as quartz crystal microbalance (QCM) and surface acoustic wave (SAW) devices, can principally be used for both types of analysis, with the actual application mainly depending on the device coating and the test format. This review summarizes the achievements of acoustic sensor devices used for milk analysis applications, including the determination of physical liquid parameters and the detection of low- and high-molecular-weight analytes and microorganisms. It is shown how the various requirements resulting from the respective analytes and the complex sample matrix are addressed, and to what extent the analytical demands, e.g., with regard to legal limits, are met.