Search Results (14)

Air-coupled ultrasound (ACU) is emerging as a fully non-contact sensing modality in biomedical applications. ACU applications can be broadly classified into two main domains: (i) contactless monitoring of physiological parameters and (ii) assistive aids, robotic perception in unstructured real-world environments, enabling tracking and geometric reconstruction. Advances in electronic materials and sensor design have enhanced ultrasonic sensor characteristics (e.g., bandwidth, directivity, and intensity). In parallel, progress in front-end electronics and signal processing, including artificial intelligence (AI)-assisted analysis, has enhanced ACU performance under low signal-to-noise (SNR) conditions. This review focuses on low-frequency ACU systems, with emphasis on sensor technologies, electronic interfaces, and system architectures that enable non-contact biomedical and robotic applications. Full article

Ultrasonic guided wave interdigital transducers realized with piezoelectric materials are of interest for structural health monitoring systems because of their capability of performing Lamb wave mode selection with respect to single-element transducers. Besides this advantage, the coverage of large areas with a minimum number of elements is an important challenge and the problem of efficient excitation with integrated electronics must be solved. This work proposes an electrical matching network topology made of L and C passive components that can be designed for the trade-off between electrical to mechanical conversion efficiency and bandwidth. The network circuit is analyzed considering the equivalent transducer impedance and the output impedance of the driving electronics. The design rules derived by the transfer function analysis are described and a case study for a piezopolymer IDT is presented. Finally, with the implementation of the integrated matching network with the connector of the IDT, the effect of cable capacitance is minimized. In conclusion this article is a contribution to the study of using IDT efficiently and in a versatile mode for different electronic front-ends that usually operate at low power supply voltage. Full article

There are various commercially available multifunctional electronics laboratory test equipment on the market that integrates an oscilloscope, signal generator, and logic analyzer. The price point for all these devices typically exceeds USD 250. To lower this cost to around USD 100, the data acquisition components of these devices need to be re-evaluated. In this paper, we present the design of an analog front-end (AFE) for low-cost multifunctional laboratory equipment, mainly for electronics students. The primary objective was to meet student requirements while ensuring minimal cost, maximum functionality, and high robustness. Through our research, we optimized our AFE design to achieve these objectives effectively. Our approach addresses key limitations found in existing designs, as we developed four-stage attenuation and three-stage op-amp gain architecture. This arrangement optimizes signal clarity and achieves high bandwidth while maintaining a cost-effective framework suitable for educational applications. With this study, a 20 MHz bandwidth, ±40 V input voltage range, volt/div range from 5 mV to 10 V, and minimum amplitude resolution of 9.7 µV were achieved in the design of the analog front-end and data acquisition unit. The achieved bandwidth and linearity enable designed AFE to accommodate applications such as ultrasonic discrete TGC (Time Gain Compensation). Full article

This article presents a method of ultrasonic testing (UT) that detects and quantifies interlaminar delaminations in CFRP composites with high resolution in terms of both spatial resolution in the planar dimension and depth into the laminate. Unidirectional and woven CFRP laminates were fabricated for this study, with a PTFE film inserted at various depths throughout the laminate to act as intentional crack initiation sites. All samples were mechanically tested via a three-point, end-notched flexure (ENF) test, followed by a quantification of the extent of the induced interlaminar delaminations using UT and X-ray computed tomography (CT). UT analysis for unidirectional CFRP samples was able to show a clear contrast between the delaminated area and the non-delaminated area. UT analysis of the woven CFRP samples yielded comparable results but required finer tuning of analysis parameters due to the interlocking woven fabric. CT results revealed a significant contrast between the crack and composite; thus, fine geometrical features of the crack front could be observed. UT and CT measurements were then compared, revealing an average difference of 1.09% in the delamination area, with UT overestimating as compared to CT. A UT depth study was also performed to automatically locate the interlaminar delamination at different depths throughout the components, with the delamination being predicted within one lamina interface for all samples. These results demonstrate UT’s ability to accurately detect and quantify the extent and location of interlaminar delaminations due to bending. Full article

This study conducted longitudinal ultrasonic-assisted milling (UAM) tests and optimized a combination of milling technological parameters to achieve high-quality machining of TC18 titanium alloy. The motion paths of the cutter under the coupled superposition states of longitudinal ultrasonic vibration and end milling were analyzed. Based on the orthogonal test, the cutting forces, cutting temperatures, residual stresses, and surface topographical patterns of TC18 specimens under different UAM conditions (cutting speeds, feeds per tooth, cutting depths, and ultrasonic vibration amplitudes) were examined. The differences between ordinary milling and UAM in terms of machining performance were compared. Using UAM, numerous characteristics (including variable cutting thickness in the cutting area, variable cutting front angles of the tool, and the lifting of the cuttings by the tool) were optimized, reducing the average cutting force in all directions, lowering the cutting temperature, increasing the surface residual compressive stress, and significantly improving the surface morphology. Finally, fish scale bionic microtextures with clear, uniform, and regular patterns were formed on the machined surface. High-frequency vibration can improve material removal convenience, thus reducing surface roughness. The introduction of longitudinal ultrasonic vibration to the end milling process can overcome the limitations of traditional processing. The optimal combination of UAM parameters for titanium alloy machining was determined through the end milling orthogonal test with compound ultrasonic vibration, which significantly improved the surface quality of TC18 workpieces. This study provides insightful reference data for subsequent machining process optimization. Full article

High-frequency ultrasound has developed rapidly in clinical fields such as cardiovascular, ophthalmology, and skin with its high imaging resolution. However, the development of multi-elements high-frequency ultrasonic transducers and multi-channel high-frequency ultrasound imaging systems is extremely challenging. Here, a high-frequency ultrasound imaging system based on mechanical scanning was proposed in this paper. It adopts the method of reciprocating feed mechanism, which can achieve reciprocating scanning in the 14 mm range at 168 mm/s with a small 60 MHz transducer. A single-channel high-frequency ultrasonic imaging system consisting of the transmitting module, analog front end, acquisition module, and FPGA control module was developed. To overcome the non-uniformity of mechanical scanning, the ultrasound images are compensated according to the motion trajectory. The wire target and ex vivo tissue experiments have shown that the system can obtain an imaging resolution of 51 μm, imaging depth of 8 mm, and imaging speed of 12 fps. This high-frequency mechanical scanning ultrasound imaging system has the characteristics of simple structure, high-frequency, real-time, and good imaging performance, which can meet the clinical needs of high-resolution ultrasound images. Full article

The purpose of this work is to present a flexible system that supports the study of wideband underwater acoustic communications (UAC). It has been developed both to measure channels and to test transmission techniques under realistic conditions in the ultrasonic band. This platform consists of a hardware (HW) part that includes multiple hydrophones, projectors, analog front-ends, acquisition boards, and computers, and a software (SW) part for the generation, reception, and management of acoustic sounding signals and noise. UAC channels are among the most hostile ones and exhibit an important attenuation and distortion, essentially due to both multipath propagation, which results in a very long channel impulse response, and time-varying behavior, which produces a notable Doppler spread. To cope with this challenging medium, sophisticated transmission techniques must be employed. In this sense, adequate signal processing algorithms have been designed aiming not only at the analysis and characterization of underwater communication channels but also at the evaluation of diverse modulation, detection, and coding schemes, from Orthogonal Frequency Division Multiplexing (OFDM) to single-carrier digital modulations with a single-input multiple-output (SIMO) configuration that takes advantage of diversity techniques. Wideband sounding signals, to be injected into the sea from the transmitter side, are created with patterns that allow multiple tests on a batch. With offline processing of the captured data at the receiver side, different trials can be carried out in a very flexible manner. The different aspects of the platform are described in detail: the HW equipment used, the SW interface to control acquisition boards, and the signal processing algorithms to estimate the UAC channel response. The platform allows the analysis and design of new proposals for underwater communications systems that improve the performance of the current ones. Full article

As traditional ultrasonic imaging systems (UIS) are expensive, bulky, and power-consuming, miniaturized and portable UIS have been developed and widely utilized in the biomedical field. The performance of integrated circuits (ICs) in portable UIS obviously affects the effectiveness and quality of ultrasonic imaging. In the ICs for UIS, the analog-to-digital converter (ADC) is used to complete the conversion of the analog echo signal received by the analog front end into digital for further processing by a digital signal processing (DSP) or microcontroller unit (MCU). The accuracy and speed of the ADC determine the precision and efficiency of UIS. Therefore, it is necessary to systematically review and summarize the characteristics of different types of ADCs for UIS, which can provide valuable guidance to design and fabricate high-performance ADC for miniaturized high resolution UIS. In this paper, the architecture and performance of ADC for UIS, including successive approximation register (SAR) ADC, sigma-delta (Σ-∆) ADC, pipelined ADC, and hybrid ADC, have been systematically introduced. In addition, comparisons and discussions of different types of ADCs are presented. Finally, this paper is summarized, and presents the challenges and prospects of ADC ICs for miniaturized high resolution UIS. Full article

We present a new spatial compounding method to improve the contrast of ultrasonic images for non-delayed sequential beamforming (NDSB). Sequential beamforming adopts more than one beamformer to reconstruct B-mode images which has the advantage of simple front-end electronics and fast data transfer rate. Via field pattern analysis, we propose a compounding method where two more sub-images can be reconstructed along with the NDSB sub-image. These sub-images can be seen as being produced with different transmit origins; thus, their summation enhances image contrast. Image quality was analyzed in terms of spatial resolution, contrast ratio (CR), and contrast-to-noise ratio (CNR). The proposed compounding method improves the lateral resolution up to 41%. In vitro results confirm a 13.0-dB CR and 4.0-dB CNR improvement. In vivo results reveal 10.9-dB and 6.0-dB improvement in CR and CNR for cross-section jugular vein and 8.0-dB and 4.5-dB improvement in CR and CNR for the longitudinal-section carotid artery. Full article

This review article is focused on the analysis of the state of the art of sensors for guided ultrasonic waves for the detection and localization of impacts for structural health monitoring (SHM). The recent developments in sensor technologies are then reported and discussed through the many references in recent scientific literature. The physical phenomena that are related to impact event and the related main physical quantities are then introduced to discuss their importance in the development of the hardware and software components for SHM systems. An important aspect of the article is the description of the different ultrasonic sensor technologies that are currently present in the literature and what advantages and disadvantages they could bring in relation to the various phenomena investigated. In this context, the analysis of the front-end electronics is deepened, the type of data transmission both in terms of wired and wireless technology and of online and offline signal processing. The integration aspects of sensors for the creation of networks with autonomous nodes with the possibility of powering through energy harvesting devices and the embedded processing capacity is also studied. Finally, the emerging sector of processing techniques using deep learning and artificial intelligence concludes the review by indicating the potential for the detection and autonomous characterization of the impacts. Full article

To conduct burst-echo imaging with air-coupled capacitive micromachined ultrasonic transducers (CMUTs) using the same elements in transmission and reception, this work proposes a dedicated and integrated front-end circuit board design to build an imaging system. To the best of the authors’ knowledge, this is the first air-coupled CMUT burst-echo imaging using the same elements in transmission and reception. The reported front-end circuit board, controlled by field programmable gate array (FPGA), consisted of four parts: an on-board pulser, a bias-tee, a T/R switch and an amplifier. Working with our 217 kHz 16-element air-coupled CMUT array under 100 V DC bias, the front-end circuit board and imaging system could achieve 22.94 dB signal-to-noise ratio (SNR) in burst-echo imaging in air, which could represent the surface morphology and the three-dimensional form factor of the target. In addition, the burst-echo imaging range of our air-coupled CMUT imaging system, which could work between 52 and 273 mm, was discussed. This work suggests good potential for ultrasound imaging and gesture recognition applications. Full article

This paper presents an analog front-end transceiver for an ultrasound imaging system based on a high-voltage (HV) transmitter, a low-noise front-end amplifier (RX), and a complementary-metal-oxide-semiconductor, aluminum nitride, piezoelectric micromachined ultrasonic transducer (CMOS-AlN-PMUT). The system was designed using the 0.13-μm Silterra CMOS process and the MEMS-on-CMOS platform, which allowed for the implementation of an AlN PMUT on top of the CMOS-integrated circuit. The HV transmitter drives a column of six 80-μm-square PMUTs excited with 32 V in order to generate enough acoustic pressure at a 2.1-mm axial distance. On the reception side, another six 80-μm-square PMUT columns convert the received echo into an electric charge that is amplified by the receiver front-end amplifier. A comparative analysis between a voltage front-end amplifier (VA) based on capacitive integration and a charge-sensitive front-end amplifier (CSA) is presented. Electrical and acoustic experiments successfully demonstrated the functionality of the designed low-power analog front-end circuitry, which outperformed a state-of-the art front-end application-specific integrated circuit (ASIC) in terms of power consumption, noise performance, and area. Full article

This paper describes the design of a front-end receiver amplifier for capacitive micromachined ultrasonic transducer (CMUT). The proposed operational amplifier (op amp) consists of a full differential folded-cascode amplifier stage followed by a class AB output stage. A feedback resistor is applied between the input and the output of the op amp to make a transimpedance amplifier. We analyzed the equivalent circuit model of the CMUT element operating in the receiving mode and obtained the static output impedance and center frequency characteristics of the CMUT. The op amp gain, bandwidth, noise, and power consumption trade-offs are discussed in detail. The amplifier was fabricated using GlobalFoundries 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology. The open loop gain of the amplifier is approximately 65 dB, and its gain bandwidth product is approximately 29.5 MHz. The measured input reference noise current was 56 nA/√Hz@3 MHz. The amplifier chip area is 325 μm × 150 μm and the op amp is powered by ±3.3 V, the static power consumption is 11 mW. We verified the correct operation of our amplifier with CMUT and echo-pulse shown that the CMUT center frequency is 3 MHz with 92% fractional bandwidth. Full article

The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications. Full article