超声相控阵扇扫诊断仪中提高帧频的新方法

文章通过仔细分析相控延时及超声波束的空间特征，导出了相邻波束指向与延时之间的相互关系；找出了其中的规律性及可用特征。提出一种提高帧频的新方法：多波束同时合成法，从而能有效地改善彩色超声成像质量。     

Multiple-focus ultrasound phased-array pattern synthesis: optimal driving-signal distributions for hyperthermia

A method for computing array element amplitude and phase distributions for direct synthesis of multiple-focus field patterns using ultrasonic phased arrays is shown to be capable of producing desired field levels at a set of control points in the treatment volume. The complex pressure at any of these control points can be chosen to produce the desired power deposition at the point, including reducing the field level to avoid potential hot spots, thus providing a powerful tool for hyperthermia treatment planning. The method also allows the complex excitation vector to be weighted to reduce the dynamic range of the driving signals without disturbing the relative field levels at the control points, allowing near maximum power transfer from the array into the treatment volume.     

Ultrasonic spray pyrolysis for nanoparticles synthesis

This article presents new findings regarding the effects of precursor drop size and precursor concentration on product particle size and morphology in ultrasonic spray pyrolysis. Large precursor drops (diameter > 30 m) generated by ultrasonic atomization at 120 kHz yielded particles with holes due to high solvent evaporation rate, as predicted by the conventional one particle per drop mechanism. Precursor drops 6–9 m in diameter, generated by an ultrasonic nebulizer at 1.65 MHz and 23.5 W electric drive power, yielded uniform spherical particles 90 nm in diameter with proper control of precursor concentration and residence time. Moreover, air-assisted ultrasonic spray pyrolysis at 120 kHz and 2.3 W yielded spherical particles about 70% of which were smaller than those produced by the ultrasonic spray pyrolysis of the 6–9 m precursor drops, despite much larger precursor drop size (28 m peak diameter versus 7 m mean diameter). These particles are much smaller than predicted by the conventional one particle per drop mechanism, suggesting that a gas-to-particle conversion mechanism may also be involved in spray pyrolysis.     

Ultrasonic scanner for in vivo measurement of cancellous bone properties from backscattered data

A dedicated ultrasonic scanner for acquiring RF echoes backscattered from the trabecular bone was developed. The design of device is based on the goal of minimizing of custom electronics and computations executed solely on the main computer processor and the graphics card. The electronic encoder-digitizer module executing all of the transmission and reception functions is based on a single low-cost field programmable gate array (FPGA). The scanner is equipped with a mechanical sector-scan probe with a concave transducer with 50 mm focal length, center frequency of 1.5 MHz and 60% bandwidth at -6 dB. The example of femoral neck bone examination shows that the scanner can provide ultrasonic data from deeply located bones with the ultrasound penetrating the trabecular bone up to a depth of 20 mm. It is also shown that the RF echo data acquired with the scanner allow for the estimation of attenuation coefficient and frequency dependence of backscattering coefficient of trabecular bone. The values of the calculated parameters are in the range of corresponding in vitro data from the literature but their variation is relatively high.     

面向医学内窥诊断的数字超声多普勒成像系统

研究基于现场可编程门阵列（FPGA）的超声多普勒内窥成像系统,针对内窥系统超声探头体积小、回波信号微弱的特点,设计了具有较高增益和较低噪声的超声信号前端接收电路.在FPGA中对微弱信号进行全数字化处理,实现了正交解调与频谱分析等功能,系统具有电路匹配性好、信噪比高、处理速度快及体积小等优势;搭建基于多普勒物理模型的实验平台进行实验验证,分析对比不同实验条件下的声谱,验证了系统及信号处理方法的合理性和正确性.     

Target velocity estimation with FM and PW echo ranging Doppler systems I. Signal analysis

The theoretical foundation is presented for velocity estimation with a pulsed wave (PW) Doppler system transmitting linear FM signals. The Doppler system possesses echo ranging capabilities and is evaluated in the context of Doppler ultrasound for blood velocity measurement. The FM excitation signal is formulated and the received signal is derived for a single moving particle. This signal is similar to the transmitted signal, but with modified parameters due to Doppler effect and range. The demodulated received signal is subsequently derived and analyzed. It is shown that, due to the Doppler effect, this is a linear sweep signal as well. The velocity and range information obtainable from one and two consecutively received signals are described. The latter case establishes the basis for an FM Doppler system for blood velocity measurements.     

Target velocity estimation with FM and PW echo ranging Doppler systems. II. Systems analysis

For part I see ibid., vol.40, no.4, pp.366-372 (1993). In Part I, the encoding of the velocity and range information into the received and demodulated signals based on transmission of coherent repetitive linear sweep signals, was discussed. In the present work, two different implementations of FM Doppler systems that can be used to obtain velocity profiles are presented. The first implementation is similar to the implementation of a conventional pulsed wave (PW) Doppler system, based on measurement of phase shift (correlation based system): the second implementation is a frequency-domain analog to the PW Doppler system, based on time shift measurements (cross correlation-based system).     

Constrained digital matched filter method for optimum filter synthesis

We present a new method to directly calculate the optimum filter in presence of any additive stationary noise, with arbitrary time and domain constraints (flat-top, zero-area, etc.). A more concise re-deduction of digital penalized LMS method (DPLMS) is given. This method is fully developed, and synthesis results of a typical situation are given and compared with the DPLMS method. Optimum filter can be synthesized without a prior knowledge of the noise power spectral density, which makes it suitable to be used in adaptive, self-calibrating digital spectroscopy.     

A direct digital synthesis system for acoustic wave sensors

Current designs for acoustic wave sensor system electronics are typically based on surface acoustic wave (SAW) oscillators, phase detectors, or phase-locked loops to measure changes in SAW velocity. The advantage of oscillators is a high resolution frequency output, as compared to phase detection systems which are more stable and can more easily provide amplitude information. Phase-locked loops (PLL) offer advantages of both the oscillator and phase detection systems but have the disadvantages of a fixed frequency range and the need for frequency counting circuitry. The objectives of this work were to study the performance of a direct digital synthesis (DDS) based PLL system with the advantages of a programmable frequency range, elimination of the need for frequency counting circuitry, and tolerance of large SAW sensor insertion losses. The DDS system tested had a resolution of 4 Hz and a range of 80 to 120 MHz in SAW humidity and temperature sensing applications indicating that the DDS based PLL is a practical electronic system for SAW sensors.     

流量测量中超声多普勒信号的频谱特点及其与管道中流速的关系

研究了工业测流的超声多普勒信号的频谱特点，并以此为依据分析了不同安装方式对多普勒频谱的影响，提出了不同测量环境下，应用多普勒频谱计算流速的公式及必要的修正，为提高检测准确度提供了理论依据。     

Analysis and synthesis of detection devices for radar systems of laser Doppler velocimeters

The principles have been worked out for a systems approach to the choice of technical designs for detection devices of radar systems of laser Doppler velocimeters.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 50–53, November, 1993.     

Fast-Fourier-domain delay line for in vivo optical coherence tomography with a polygonal scanner

We demonstrate in vivo optical coherence tomography using a Fourier-domain optical delay line constructed with a commercially available polygonal scanner. The 20-faceted polygonal mirror array, capable of scanning at rates up to 15 kHz, is implemented at 4 kHz to acquire 500 x 500 pixel images at 8 frames/s with a signal-to-noise ratio of 80 dB. Features of this delay line include scalability to high repetition rates, 98.6% linearity in group delay over 2 mm, and bandwidth support exceeding 150 nm. Images are obtained in an animal model (Xenopus laevis), and limitations due to phase-delay nonlinearity and polygon asymmetry are discussed.     

Comparative Study of Laser Doppler Vibrometer and Capacitive Air‐coupled Transducer for Ultrasonic Propagation Imager and the New Development of an Efficient Ultrasonic Wavenumber Imaging Algorithm

Damage detection techniques using guided waves have been studied for decades with very few successful real‐world applications. The recent development with the full wavefield technique using the Ultrasonic Propagation Imager (UPI) is one of those few exceptions. In this paper, we study two non‐contact sensors: the laser Doppler vibrometer and the capacitive air‐coupled transducer in the context as the sensing modules for the UPI. The aim of this paper is to provide a comprehensive study for optimisation of the two sensors, as well as a comparison between them for use in the UPI. First, the parameters for laser ultrasonic measurement of each sensor were studied: surface treatment, measurement angle and stand‐off distance in the case of the laser Doppler vibrometer and measurement angle, lift‐off distance and bias voltage in the case of the capacitive air‐coupled transducer. Two optimised sensors were then compared in terms of their ability to detect damages using the UPI. Also, in this paper, we presented the ultrasonic wavenumber imaging (UWI) algorithm with the new development towards an efficient implementation. The uniqueness of the UWI algorithm with the capability of damage size estimation makes this algorithm very attractive for the future study with full wavefield signal processing.     

Ultrasonic phased arrays with variable geometric focusing for hyperthermia applications

An ultrasonic applicator, which utilizes both electronic and variable geometric focusing, for deep-localized hyperthermia is investigated. The applicator is based around a linear phased array that furnishes its electronic focusing capability. The output of the array radiates through a spherical liquid-lens that provides the applicator a variable geometric focusing capability as well. A lens of this type adds dynamic focusing to the elevation dimension of the linear phased array. By controlling the volume of liquid in the lens (and thus the radius of curvature of its membrane), dynamic control of the geometrical focus can be achieved. Comparisons of computer simulations and experimental measurements of the field intensity distribution of a small-scale prototype applicator are presented. Important design parameters, such as the choice of the liquid for the lens and the size and number of array elements, are examined.     

钢锻件的超声波纵波手动检测工艺的优化

钢锻件超声波手动检测时,其工艺类似钢板纵波检测,但锻件厚度较大,不易确定其缺陷位置,也不易确定其当量。本文对此工艺进行了优化：包括对超声波检测仪器、试块、探头的选择、直探头偏离的测定、检测时机和表面准备、方向、灵敏度的确定校准和复核、手动扫查方法、灵敏度补偿、缺陷当量确定、记录和评级等。     

A digital divider with extension bits for position-sensitive detectors

Digitizing errors produced in a digital divider for position-sensitive detectors have been reduced by adding extension bits to data bits. A relation between the extension bits and the data bits to obtain perfect position uniformity is also given. A digital divider employing 10 bit ADCs and 6 bit extension circuits has been constructed.     

Calibration system for electronic instrument transformers with digital output

A high-accuracy system for calibration of electronic instrument transformers with digital output is described. Its design is based on International Electrotechnical Commission (IEC) standards 61850, 60044-8, and 60044-7. The performance of the calibration system has been evaluated. Its estimated relative uncertainty (2/spl sigma/) is within 40/spl middot/10/sup -6/ in magnitude and within 40 /spl mu/rad in phase.