IEEE transactions on ultrasonics, ferroelectrics, and frequency control最新文献

This study presents a comprehensive dispersion analysis and characterization of guided surface acoustic waves (SAWs) in 30% scandium aluminum nitride (ScAlN) alloy thin films on sapphire (SoS). The solidly mounted platform, which supports the fundamental Rayleigh and Sezawa SAW modes, offers mechanical robustness and high electromechanical coupling (k²_t), while maintaining high confinement of the acoustic modes. Numerical modeling, coupled with experimental results, showcases the characteristics of focusing interdigitated transducers (FIDTs) for injecting acoustic energy into piezoelectric etch-defined acoustic waveguides and highlights their advantages over conventional uniform aperture transducers. Identity mapping of boundary conditions significantly reduces degrees of freedom in modeling energy injection into acoustic waveguides. The theory of Gaussian beams in optics is applied to the FIDTs to model the physical response of the transducers accurately and emphasize their high-intensity focusing nature. This work also demonstrates the ability of FIDTs to facilitate phononic devices and phononic integrated circuit applications in slow-on-fast piezoelectric platforms.

Ultrasound open scanners have recently boosted the development and validation of novel imaging techniques. They are usually split into hardware- or software-oriented systems, depending on whether they process the echo data using embedded FPGAs/DSPs or a GPU on a host PC. The goal of this work was to realize a high-performance heterogeneous open scanner capable of leveraging the strengths of both hardware and software-oriented systems. The elaboration power of the 256-channel ultrasound advanced open platform (ULA-OP 256) was further enhanced by embedding a compact co-processing GPU system-on-module (SoM). By carefully avoiding latencies and overheads through low-level optimization work, an efficient PCIe communication interface was established between the GPU and the processing devices onboard the ULA-OP 256. As a proof of concept of the enhanced system, the high frame rate color flow mapping technique was implemented on the GPU SoM and tested. Compared to a previous DSP-based implementation, higher real-time frame rates were achieved together with unprecedented flexibility in setting crucial parameters such as the ensemble length (EL). For example, by setting EL=64 and a continuous-time high-pass filter, the flow was investigated with high temporal and spatial resolution in the femoral vein bifurcation (frame rate = 1.1 kHz) and carotid artery bulb (4.3 kHz), highlighting the flow disturbances due to valve aperture and secondary velocity components, respectively. The results of this work promote the development of other computational-expensive processing algorithms in real-time and may inspire the next generation of ultrasound high-performance heterogeneous scanners.

This paper describes prototype temperature compensated piezoelectric MEMS oscillators operating in the wide temperature range of -40 °C to 85 °C for RTC applications. The AlN-on-Si resonator is centrally anchored at one point and designed for low power operation with a wide frequency tuning range of 5000 ppm. The oscillators exhibit a stable sinusoidal output at about 497 kHz frequency for time keeping applications with an integrated phase jitter being 10× better than the best commercially available MEMS RTC oscillators for supplementary use in portable devices for clocking audio circuits. The measured oscillator performance remains relatively unchanged when comparing the wafer level packaged capped MEMS resonator with the uncapped one, showing great potential for a high performance low-power RTC oscillator.