辐射力天平法测量相控阵超声换能器的声功率

超声换能器相控阵已用于聚焦超声治疗的研究和应用已有20多年历史,但其声功率P的测量仍缺乏方便有效简易的测量方法。文章旨在提出一种基于凸球面吸收靶的辐射力天平（Radiation Force Balance,RFB）方法,测量其声功率。理论推导了这种RFB在各种阵元组合下的比值r=P/cF（c为水中声速,F为阵的声束轴方向的总辐射力）。论述了测量各种组合的发射声功率的实施方法和测量程序。为实际的测量系统设计和应用建立了良好的工作基础。     

Low acoustic attenuation silicone rubber lens for medical ultrasonic array probe

Effects of heavy density (p = 9.2 x 10³ kg/m³) Yb²O³ fine dopant (16 nm in diameter) on the acoustic properties of a high-temperature-vulcanization (HTV) silicone rubber have been investigated, to develop a new acoustic lens material with a low acoustic attenuation (alpha) for the medical array probe application. The HTV silicone rubber has advantages in that it shows a lower alpha than that of a room-temperature-vulcanization (RTV) silicone rubber and it can be mixed by applying shear stress, using roll-milling equipment. Roll-milling time dependence of the HTV silicone rubber indicates that the alpha is closely affected by the dispersion of nanopowders in the rubber matrix. The 8 vol% Yb²O³-doped HTV silicone rubber mixed for 30 min showed the lowest alpha of 0.73 dB/mmMHz with an acoustic impedance [AI = sound speed (c) times density (p)] of 1.43 times 106 kg/m²s at 37degC. Moreover, simulation results reveal that a 5 MHz linear probe using the HTV silicone rubber doped with Yb²O³ powder showed relative sensitivity around 2.6 to 3.0 dB higher than a probe using RTV silicone rubber doped with Yb²O³ powder or SiO²-doped conventional silicone rubber for the ultrasonic medical application.     

声波测井仪井下数字滤波器设计与实现

交叉偶极阵列声波测井仪是目前主流的先进声波测井设备之一,但在测井过程中难免存在噪声干扰,对测井质量造成不利影响。在利用Matlab对大量实测信号进行时频分析的基础上,针对噪声的规律和特点,提出时域滤波和频域滤波相结合的方案。时域上采取限幅平均滤波法,频域上选择具有线性相位的FIR滤波器。利用Matlab滤波器设计与分析工具箱获取滤波器系数,借助DSP软件开发环境CCS,用汇编语言设计了基于DSP的井下实时FIR数字滤波器。现场测井试验表明,该滤波器对测井信号中存在的噪声具有良好的抑制作用,同时满足测井系统的实时性要求。     

全数字控制超声波金属焊接电源的设计

针对超声波金属焊接工艺的需求,设计了一种全数字控制的超声波焊接电源。该电源采用ARM嵌入式处理器,WINCE多任务操作系统,具有能量、时间及峰值功率控制模式。主电路采用移相方式控制全桥变换器,提出了一种新型的电流有效值偏差频率自动跟踪方法。电源同时具有自动谐振频率点搜索与存储、可编程的缓启动、可编程的幅度阶梯输出控制、可编程次品检测控制、基于ModBus协议的RS232/RS485通信接口等功能。     

Use of a ultrasonic transducer array for measuring the velocity and attenuation of leaky acoustic waves

We suggest a new method for measuring local values of the velocity and attenuation of leaky acoustic waves, which is based on wave field measurements using an immobile array of receiving ultrasonic transducers. In comparison to the methods using a single focused transducer mechanically scanned over a given region of the sample, the proposed technique is advantageous in having a higher operation speed due to the electronic switching of receiving channels in the array and in requiring no high-precision mechanical scanners. A ray model of the proposed measuring system comprising an array of ultrasonic transducers with an electronic scanning facility is described. Theoretical conclusions have been experimentally confirmed by tests on the samples with known properties.     

近场声全息测量阵架的设计与分析

全息测量系统设计的关键是测量全息面测点复声压(幅值和相位)的真实数据,介绍了自行设计的近场声全息(NAH)测量的传声器线阵扫描系统.利用边界元法计算了传声器线阵架结构表面声散射对阵上传声器测量全息复声压的影响,提出了敷设吸声材料以提高测量精度的措施;对在线阵架表面敷设吸声材料后的声散射效应仿真结果表明,吸声材料能够有效...     

Measuring the acoustic wave velocity and sample thickness using an ultrasonic transducer array

We suggest a new method for determining the longitudinal and transverse acoustic wave velocities and sample thicknesses, which is based on the measurement and analysis of pulsed echo signals by an array of ultrasonic transducers. Analytical expressions relating the delay of signals detected by the array and the values of parameters to be determined are obtained within the framework of a ray model of the measuring system. Measurements on a reference sample have been performed. The values of ultrasonic wave velocities and sample thickness obtained using the proposed technique agree with the results of measurements using independent methods.     

过钻具阵列声波测井采集电路设计与实现

针对过钻具阵列声波测井对信号采集电路高精度、大动态、低噪声、低功耗、高集成度以及各通道同步性好的要求,设计一种多通道数据采集电路。该电路采用各通道独立数字化方案以保证各通道信号采集的同步性,采用低噪音仪表放大器作为前置放大器以降低系统噪声,选用18位ADC扩大数字化动态,ADC输出采用菊花链连接以减少电路连线。实测结果表明:12通道采集电路功耗为550 mW,噪声均方根值小于13μV,信号测量动态范围达93 dB,单通道采集电路面积为19 mm×70 mm。因此,设计电路既能很好满足过钻具阵列声波测井信号采集要求,也可作为其他阵列声波测井信号采集的参考方案。     

测量超声场声强用组合式水听器的设计方案

介绍1种可用于测量超声波声场强度的新型水听器。它是由声压型水听器与振速水听器在结构上组合为一体而构成,文中描述了这种水听器的基本结构型式,工作原理及特性。     

Design of a hexagonal air-coupled capacitive micromachined ultrasonic transducer for air parametric array

An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great potential for air-coupled applications,mainly because of their low acoustic impedance.In this study,an air-coupled CMUT array is designed as an air parametric array.A hexagonal array is proposed to improve the directivity of the sound generated.A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell.The CMUT array is then fabricated by a wafer bonding process with high consistency.The performances of the CMUT are tested to verify the accuracy of the finite element analysis.By optimizing the component parameters of the bias-T circuit used for driving the CMUT,DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission.Finally,the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.     

HIFU聚焦探头声场功率测量的凹锥面反射靶设计分析

在HIFU聚焦探头声功率测量中,常用吸收靶来进行声功率测量。锥面反射靶是辐射压力法测量大功率超声功率常用的反射靶面,本文分析了凹锥面反射靶的设计参数与HIFU聚焦探头参数之间的关系。为这种靶面参数设计提供了理论依据。本文分析中未计及靶材及厚度对测量结果的影响。     

B1 瓦特计测量声功率方法的分析和简化

本文给出郎之万Ｌａｎｇｅｖｉｎ型换能器及变幅杆振动节点、腹点处振幅比随负载的变化情况，分析了瓦特计法测量声功率本身存在的理论偏差，并给出了两性能相同的换能器对接系统的实验结果，表明这种方法在轻负载（不大于水负载）测量中的准确性，提出工程上简化的测量方法     

阵列测量中的卡尔曼滤波器算法

针对经典波束形成算法不具备实时性、占用存储空间大、计算速度慢等缺点,提出了基于卡尔曼滤波器的算法。这种算法将信号处理领域中现有的卡尔曼滤波器理论与阵列信号处理过程相结合,在频域内对声学阵列所采集到的数据进行迭代处理,不仅能够及时发现风洞测量中存在的各种问题,而且可以实时消除由测量环境所引起的各种误差。仿真结果表明,这种算法比经典波束形成算法收敛速度更快,不仅成像效果很好,而且能够对低速运动声源进行定位。此算法具备实时性,为风洞声源的实时定位提供了重要的算法选择。     

Design considerations for a higher-order-mode dielectric-loaded power extractor set for millimeter-wave generation

The design of an electron-beam excited device for millimeter-wave generation is presented. Referred to as a dielectric-loaded power extractor, it is based on the higher-order-mode operation of a dielectric-loaded waveguide. With a matching transition, the unit can deliver power to the output waveguide at one of two frequencies, 20.8 and 35.1 GHz, corresponding to the TM₀₂ and TM₀₃ modes, respectively. By properly choosing the thickness of the dielectric lining, both modes are tuned to synchronize with an ultra-relativistic electron beam traversing the unit so that the wakefield generated by the beam is excited at these modes, chosen to be at 20.8 and 35.1 GHz, respectively, both corresponding to a harmonic of the 1.3 GHz operating frequency at an accelerator facility. Power generated in the unintended TM₀₁ mode is effectively suppressed for bunch train operation by a novel technique. The device consists of a dielectric-loaded decelerating structure and two changeable output couplers to deliver the millimeter-wave power to a standard waveguide. For a drive beam with 50 nC of charge per bunch, power levels of 90.4 and 8.68 MW are expected to be delivered by the device at 20.8 and 35.1 GHz, respectively.     

Design and optimization of an OPFC ultrasonic linear phased array transducer

In contrast to piezoceramics, orthotropic piezoelectric fibre composites (OPFC) which can be used as actuator/sensor elements in damage detection show clear advantages because of their high sensitivity along the fibre direction and directivity. The focusing acoustic field distribution of the OPFC phased array transducer is analyzed by the finite element method together with directivity analysis in metallic materials. The optimal array parameters such as spacing, width and number of elements are obtained by studying the total displacement changes as various parameters change at the focus point. The feasibility of an OPFC ultrasonic phased array transducer for damage detection is validated.     

随钻声波测井仪高效电源设计

为了保障随钻声波测井仪在锂电池供电条件下能够长时间工作,需要采用高效电源设计。根据随钻声波电子系统的供电特点、电池性能和工程应用要求,设计了随钻声波测井仪电源控制电路。随钻声波测井仪采用间歇工作方式,低功耗微处理器根据随钻测量系统的指令控制电源开关,对仪器主电子系统的电源进行控制。仿真和实验结果表明,电源控制电路功耗低、抗干扰能力强、可靠性高,能够满足随钻声波测井仪的工作要求。     

C2用于声化学研究的大功率超声系统的研制

根据声化学反应的特殊要求，我们研制了用于声化学研究的大功率超声系统，由参数可调节的超声发生器配合不同频率的换能器工作，并用它组合成杯式变幅杆结构声化学反应器。解决了有关声化学设备的一些技术问题，为声化学技术从实验室规模向工业应用过渡做了必要的准备     

一种用于相控阵B超成像的数字波束合成器的设计

本文介绍了一种能沿任意波束指向全程动态聚焦的数字波束合成器的设计，此合成器用于相控阵Ｂ超成像系统。回声信号的延时量分解为“指向延时”和“聚焦延时”两部分，分别用产生相控发射激励的时序逻辑电路和一个“动态聚焦延时量表”实现。通过对Ａ／Ｄ采样时钟的控制及对Ａ／Ｄ采样时钟、地址计数时钟和存储器写时钟的时序配合，实现了同相位数据点采样及无冗余数据的缓冲存储器。所设计的数字相控波束合成器只用廉价的高速数字电路即可实现，成本极低。实验结果验证了该方案的可行性。     

Design considerations for the absolute testing approach of aspherics using combined diffractive optical elements

Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement.