Hardware-efficient realization of a real-time ultrasonic target detection system using IIR filters - [correspondence]

In this study, we address the increased computational demands of a frequency-diverse ultrasonic target detection system by developing a zero-phase IIR (ZP-IIR) filter. Several ZP-IIR filter types including Chebyshev-I, Chebyshev- II, and Butterworth were analyzed for their detection performance. The 4th-order filters with 8-bit quantized coefficients are shown to improve the flaw-to-clutter ratio by approximately 10 dB. Furthermore, the reduced adder graph algorithm is used for a hardware realization of ZP-IIR filters that does not require any dedicated multipliers. A small number of coefficients inherent to IIR filters and their multiplierless implementation provide efficient architecture suitable for compact, real-time ultrasonic imaging devices.     

An FPGA-based open platform for ultrasound biomicroscopy

Ultrasound biomicroscopy (UBM) has been extensively applied to preclinical studies in small animal models. Individual animal study is unique and requires different utilization of the UBM system to accommodate different transducer characteristics, data acquisition strategies, signal processing, and image reconstruction methods. There is a demand for a flexible and open UBM platform to allow users to customize the system for various studies and have full access to experimental data. This paper presents the development of an open UBM platform (center frequency 20 to 80 MHz) for various preclinical studies. The platform design was based on a field-programmable gate array (FPGA) embedded in a printed circuit board to achieve B-mode imaging and directional pulsed-wave Doppler. Instead of hardware circuitry, most functions of the platform, such as filtering, envelope detection, and scan conversion, were achieved by FPGA programs; thus, the system architecture could be easily modified for specific applications. In addition, a novel digital quadrature demodulation algorithm was implemented for fast and accurate Doppler profiling. Finally, test results showed that the platform could offer a minimum detectable signal of 25 μV, allowing a 51 dB dynamic range at 47 dB gain, and real-time imaging at more than 500 frames/s. Phantom and in vivo imaging experiments were conducted and the results demonstrated good system performance.     

杂乱背景中隐藏信号的三重相关检测技术

针对噪声中检测微弱信号难的问题,提出了一种实用的三重相关检测方法。该方法利用有信号和无信号噪声背景下,三重自相关集平均值的差异,排除噪声干扰,判断出信号的存在;采用似三维图形法计算峰值,实现杂乱背景中隐藏信号的检测,获得信号的确定位置。实验表明,采用三重相关峰值检测方法,在峰值信噪比为0.8702313、功率信噪比为-0.9257607dB时,可获得的信噪比改善约为23dB。在背景为随机噪声的二维图像序列中,也能判断和检测出微弱的点目标,为防伪机器识别提供了一种可供选择的方法。     

基于TMS320VC5402的数字图像空间滤波系统设计

针对红外成像观测系统中获取的低信噪比、背景及噪声干扰严重的小目标图像的特点,设 计一种具有保护带(5×5 G)的5×5 Robinson空间滤波器,采用TMS320VC5402进行硬件实现。实验表明,该空间滤波器能够大大提高目标的信噪比,抑制背景和噪声,保证系统实时性要求,很适用于小目标检测。     

Coherent array imaging using phased subarrays. Part II: simulations and experimental results

The basic principles and theory of phased subarray (PSA) imaging imaging provides the flexibility of reducing the number of front-end hardware channels between that of classical synthetic aperture (CSA) imaging--which uses only one element per firing event--and full-phased array (FPA) imaging-which uses all elements for each firing. The performance of PSA generally ranges between that obtained by CSA and FPA using the same array, and depends on the amount of hardware complexity reduction. For the work described in this paper, we performed FPA, CSA, and PSA imaging of a resolution phantom using both simulated and experimental data from a 3-MHz, 3.2-cm, 128-element capacitive micromachined ultrasound transducer (CMUT) array. The simulated system point responses in the spatial and frequency domains are presented as a means of studying the effects of signal bandwidth, reconstruction filter size, and subsampling rate on the PSA system performance. The PSA and FPA sector-scanned images were reconstructed using the wideband experimental data with 80% fractional bandwidth, with seven 32-element subarrays used for PSA imaging. The measurements on the experimental sector images indicate that, at the transmit focal zone, the PSA method provides a 10% improvement in the 6-dB lateral resolution, and the axial point resolution of PSA imaging is identical to that of FPA imaging. The signal-to-noise ratio (SNR) of PSA image was 58.3 dB, 4.9 dB below that of the FPA image, and the contrast-to-noise ratio (CNR) is reduced by 10%. The simulated and experimental test results presented in this paper validate theoretical expectations and illustrate the flexibility of PSA imaging as a way to exchange SNR and frame rate for simplified front-end hardware.     

基于霍尔效应的印刷机能耗检测方法研究

目的采用霍尔元件法搭建印刷机群能耗数字化检测平台。方法通过建立印刷机能耗指标模型框架体系,形成以总耗电量指标、均值类指标、耗电比例类指标等为主的印刷机耗电评价标准,完善能耗评价准则。采用灵敏度高、稳定性好的霍尔元件作为能耗检测元件,并分析霍尔效应、磁平衡式电流和电压霍尔传感器的检测电路。采用伏安法功率测量方式分别检测各负载电路的电流与电压,通过A/D转换模块实现检测数据数字化,并通过硬件控制核心对采集的数字信号进行运算、输出和显示,采用CAN总线实现硬件控制系统与上位机之间数字信息交互。结果搭建了印刷机群能耗数字化检测系统平台,实现了外围设备与上位机间的数据交互,实现了印刷机群以数据为核心,通过能耗检测、能效分析、能源成本控制以及能源指标优化,提高了能源利用效率。结论能耗检测的实现既能减少冗余电量损耗,又有利于监测电路稳定性,利用霍尔元件法实现印刷机群能耗检测的方法是可行的。     

A digital hardware correlation system for fast ultrasonic data acquisition in peak power limited applications

The theoretical and experimental evaluation of a digital hardware correlation system for low-power ultrasonic applications is presented. The system, which incorporates dual Golay code matched filtering, is capable of 20-MHz processing rates with a signal-to-noise-ratio enhancement (SNRE) of 23 dB over a conventional pulse-echo system operating at the same peak power levels. The effects of digitization have been investigated, and a TTL (transistor transistor logic)-based hardware correlator has been developed. For many applications, low-voltage driving followed by differential detection is sufficient, permitting the system to be used in a number of power-limited environments. Sample tests conducted on three different transducers have demonstrated that the system is operational over a wide variety of probe configurations.     

Performance evaluation of the Golay code pulse compression technique

The Center for NDE, Iowa State University, has developed a laboratory prototype Golay code pulse compression system and tested it on a variety of materials. The performance of the system was evaluated in terms of signal-to-noise ratio enhancement (SNRE), resolution, and computation speed. The system's error sources also were discussed. The Golay code pulse compression was simulated on a computer and demonstrated the effective noise suppression. In addition, an equivalent pulse of the Golay code (delta-like pulse) was derived theoretically using a simple ultrasonic inspection model, which demonstrated its equivalence on the output correlated signal. Overall, the pulse compression technique extended the detection range for a given peak power and considerably reduced the system'swhite noise, hence providing enhanced signal-to-noise ratios (SNRs). An average of 30 dB improvement in SNR was obtained from highly energy-absorbent materials such as rubber, plastics, corks (insulation materials), and thick composites using the Golay codes of up to 512 bits. However, the technique did not effectively reduce coherent scattering noises from the coarse grain boundaries in cast stainless steels, Inconel weld metal, and material lay-ups in thin composites. Furthermore, it was found that, depending upon the system's hardware capabilities, the overall performance could be degraded considerably.     

水下激光成像系统探测距离的计算与仿真

为了估计水下激光成像系统的工作距离,根据水下激光成像系统的成像过程,通过分析目标的辐射特性,水体的衰减特性等各因素,建立了水下激光成像系统的信噪比模型.根据识别目标所需要的信噪比阈值、脉冲激光器等器件的性能指标,推导出水下激光成像系统的工作距离公式,并且完成了系统成像距离的计算与仿真.采用532 nm的Nd∶YAG固体激光器、自组ICCD相机以及基于FPGA技术设计的同步控制电路板,进行了距离选通水下激光成像实验.实验结果表明:理论模型计算的信噪比与实际图像的信噪比平均误差为1.37 dB,证实了该模型的合理性.     

Amplified detection of DNA through the enzyme-free autonomous assembly of hemin/G-quadruplex DNAzyme nanowires

An enzyme-free amplified detection platform is described using the horseradish peroxidase (HRP)-mimicking DNAzyme as an amplifying label. Two hairpin structures that include three-fourths and one-fourth of the HRP-mimicking DNAzyme in caged, inactive configurations are used as functional elements for the amplified detection of the target DNA. In the presence of the analyte DNA, one of the hairpins is opened, and this triggers the autonomous cross-opening of the two hairpins using the strand displacement principle. This leads to the formation of nanowires consisting of the HRP-mimicking DNAzyme. The resulting DNA nanowires act as catalytic labels for the colorimetric or chemiluminescent readout of the sensing processes (the term "enzyme-free" refers to a protein-free catalyst). The analytical platform allows the sensing of the analyte DNA with a detection limit corresponding to 1 × 10(-13) M. The optimized system acts as a versatile sensing platform, and by coaddition of a "helper" hairpin structure any DNA sequence may be analyzed by the system. This is exemplified with the detection of the BRCA1 oncogene with a detection limit of 1 × 10(-13) M.     

Model analysis and resonance suppression of wide-bandwidth inertial reference system

In the fields of earth observation, deep space detection, laser communication, and directional energy weapon, the target needs to be observed and pointed at accurately. Acquisition, tracking, and pointing(ATP) systems are usually designed to stabilize the line of sight(LOS) within sub-micro radian levels. In the case of an ATP system mounted on a mobile platform, angular disturbances experienced by the mobile platform will seriously affect the LOS. To overcome the problem that the sampling frequency of detectors is usually limited and achieving several hundreds of hertz is difficult, the wide-bandwidth inertial reference system(WBIRS) and fast steering mirror are usually integrated into ATP systems to mitigate these angular disturbances. To reduce the structural stress, a flexible support providing two rotational degrees of freedom is usually adopted for the system. However, the occurrence of resonant points within the bandwidth will be inevitable. Measurements have to be taken to compensate these low-frequency resonant points to realize a wide bandwidth and high precision. In this paper, the lowfrequency resonant points of a system were simulated using finite element analysis and tested by a system identification method. The results show that the first-order resonance happened at 34.5 Hz with a gain of 28 dB. An improved double-T notch filter was designed and applied in a real-time system to suppress the resonance at34.5 Hz. The experimental results show that the resonance was significantly suppressed. In particular, the resonance peak was reduced by 79.37%. In addition, the closed-loop system settling time was reduced by 36.2%.     

Balanced detection spectral domain optical coherence tomography with a multiline single camera for signal-to-noise ratio enhancement

In this study, the use and advantages of balanced detection (BD) in spectral domain optical coherence tomography (SD-OCT) are demonstrated. A-scans are calculated as a combination of two phase-opposed interferometric spectra acquired simultaneously by using a multiline single camera spectrometer. Not only does this system suppress artifacts due to autocorrelation, but also the signal of interest is increased by a factor of 2 as experimentally verified. Our BD-based SD-OCT gives a signal-to-noise ratio improvement of 8-14?dB for the peak within 1?mm compared to standard SD-OCT using a single detection scheme. This method is validated by experimental measurement of a glass plate.     

A new ultrasound contrast imaging approach based on the combination of multiple imaging pulses and a separate release burst

A new ultrasound contrast imaging technique is described that optimally employs the rupture of the contrast agent. It is based on a combination of multiple high frequency, broadband, imaging pulses and a separate release burst. The imaging pulses are used to survey the target before and after the rupture and release of free gas bubbles. In this way, both processes (imaging and release) can be optimized separately. The presence of the contrast agent is simply detected by correlating or subtracting the signal responses of the imaging pulses. Because the time delay between the imaging pulses can be very short, the subtraction is less affected by tissue motion and can be done in real time. In vitro measurements showed that by using a release burst, the detection sensitivity increased 12 to 43 dB for different types of contrast agents. In the presence of a moving phantom, the increase in sensitivity was 22 dB. This new method is very sensitive for contrast agent detection in fundamental imaging mode and, therefore, non-linear propagation effects do not limit the maximum obtainable agent-to-tissue ratio. However, because of the inherent destruction of the contrast agent, it has to operate in an intermittent way. Through experiments, we have demonstrated the potential of the method to achieve simultaneous high sensitivity for contrast detection, i.e., high agent-to-tissue ratio, and high spatial resolution performance for different types of contrast agents     

Estimation and correction of ultrasonic wavefront distortion using pulse-echo data received in a two-dimensional aperture

Pulse-echo measurements from random scattering and from a point target have been used to quantify transmitter beam size effects and isoplanatic patch size as well as to evaluate the performance of different aberration compensation techniques. Measurements were made using a single-element transmitter with a diameter of 1/2 in., 1 in., or 2 in., each focused at 3 in. A tissue-mimicking scattering phantom or a point target was used to produce echoes that were received in a two-dimensional aperture synthesized by scanning a linear array. A specimen of abdominal wall was placed in the reception path to produce aberration. B-scan images were formed with no compensation, with time-shift compensation in the receiving aperture, and with backpropagation followed by time-shift compensation. The isoplanatic patch size was estimated by compensating the focus of a test point target with the parameters estimated for an original point target position, and observing the deterioration of compensation effects with increasing distance between the test and the original point targets. The results of the measurements using different transmitter diameters quantify the improvement of time-delay estimation with the increase in wavefront coherence that accompanies decreased transmitter beam size. For seven specimens, the average isoplanatic patch size determined from a 10% increase in the -10 dB effective diameter was 16.7 mm in the azimuthal direction and 39.0 mm in the range direction. These sizes increased after backpropagation to 19.0 mm and 41.4 mm, respectively. For the 1/2 in., 1 in., and 2 in. diameter transmitters, the average contrast ratio improvement was 2.0 dB, 2.1 dB, and 2.8 dB, respectively, with time-shift compensation, and 2.3 dB, 2.7 dB, and 3.5 dB, respectively, with backpropagation of 20 mm followed by time-delay estimation and compensation. The investigation indicates that a tightly focused transmitter beam is necessary to create a scattered wavefront satisfactory for time-shift estimation, the isoplanatic patch is about twice as long in the range direction as in the azimuthal direction, and backpropagation followed by time-shift compensation provides better compensation of distortion than time-shift compensation alone.     

曲面结构石英纤维增强树脂复合材料分层损伤缺陷太赫兹智能检测

为探索先进预警机雷达罩石英纤维增强树脂复合材料中典型分层缺陷的智能化检测手段,将协作机器人与反射式太赫兹时域光谱系统相结合,搭建了一种基于光纤耦合的反射式太赫兹时域光谱扫查系统,测试所得信噪比的动态范围约60 dB。利用搭建系统对预埋模拟分层缺陷的曲面结构石英纤维增强树脂复合材料样件进行太赫兹无损检测,不同扫描区域获得的反射式太赫兹成像图中均能通过目视辨认出内部预埋缺陷。利用改进的YOLOv4算法在缺陷自动识别中获得90.18%的准确率和91.26%召回率,分别较原YOLOv4算法提高3.37%和4.01%,对小目标缺陷的检测效果良好。实验丰富了预警机雷达罩样件的设计和检测研究内容,探索了曲面结构石英纤维增强树脂复合材料缺陷太赫兹成像,为预警机雷达罩的无损检测提供了新的智能检测工艺,具备工程应用价值。      

Enhanced antenna-pattern measurements for Satellite systems

This paper describes an enhanced measurement technique for earth-station antennas in a satellite communication system. A new data-acquisition algorithm improves the dynamic range of the measurements by increasing the signal-to-noise ratio in the test setup. The resolution limitation of conventional techniques is eliminated without any modifications to the ground station setup. The proposed approach improves the conventional measurement techniques by utilizing pulse modulation of the test-signal amplitude and its synchronous detection. The noise floor in the pattern is reduced by biasing out the average noise power calculated during the OFF cycle of the pulse. In addition, a randomly fluctuating local mean in the receiver output is reduced. Experimental results show improvements of as much as 25 dB in the noise variance and over 11 dB in the dynamic range of the antenna pattern.     

Online Magnetic Flux Leakage Detection System for Sucker Rod Defects Based on LabVIEW Programming

Aiming at the detection of the sucker rod defects, a real-time detection system is designed using the non-destructive testing technology of magnetic flux leakage (MFL). An MFL measurement system consists of many parts, and this study focuses on the signal acquisition and processing system. First of all, this paper introduces the hardware part of the acquisition system in detail, including the selection of the Hall-effect sensor, the design of the signal conditioning circuit, and the working process of the single chip computer (SCM) control serial port. Based on LabVIEW, a graphical programming software, the software part of the acquisition system is written, including serial port parameter configuration, detection signal recognition, original signal filtering, real-time display, data storage and playback. Finally, an experimental platform for the MFL detection is set up, and the MFL measurement is carried out on the transverse and longitudinal defects of the sucker rod surface. The experimental result shows that the designed acquisition and processing system has good detection performance, simple design and high flexibility.     

一种应用于水下目标探测的激光声系统

用激光在海洋中产生声波的方式机动性非常好,在海洋监测方面具有非常强的潜在应用前景.介绍了已经成功研制出的一套可以用于水下目标探测的激光声技术实验系统,详尽地介绍了用于水下目标探测的激光声系统原理、硬件设计以及软件设计.该系统不仅通过了实验室的试验,并且参加了海上试验,实验结果表明本系统的原理正确,性能良好,工作稳定可靠,能够检测到水中目标的回波,探测到水下目标.说明激光声技术用于水下目标探测是切实可行的,这套激光声探测系统的研制成功填补了国内的空白.     

Adaptive feature-specific imaging: a face recognition example

We present an adaptive feature-specific imaging (AFSI) system and consider its application to a face recognition task. The proposed system makes use of previous measurements to adapt the projection basis at each step. Using sequential hypothesis testing, we compare AFSI with static-FSI (SFSI) and static or adaptive conventional imaging in terms of the number of measurements required to achieve a specified probability of misclassification (Pe). The AFSI system exhibits significant improvement compared to SFSI and conventional imaging at low signal-to-noise ratio (SNR). It is shown that for M=4 hypotheses and desired Pe=10(-2), AFSI requires 100 times fewer measurements than the adaptive conventional imager at SNR= -20 dB. We also show a trade-off, in terms of average detection time, between measurement SNR and adaptation advantage, resulting in an optimal value of integration time (equivalent to SNR) per measurement.