基于水下超声成像分时复用数据采集系统的设计

利用压阻式水声传感器采集超声回波信号,通过行共用电源线,列共用信号线的方式将水声传感器组成成像阵列.使用MAX4617八选一高速模拟开关控制每个传感器与采集电路的通断,从而实现采集电路的分时复用功能.利用AD6655采集数据,FPGA作为模拟开关和采集电路的时序控制器,异步FIFO作为采集数据传送给EZ-USB的缓冲器,EZ-USB单片机负责任务的协调,并把数据打包上传给计算机.初步测试了传感器与采集通道的开关时延特性,以及分时采集样本与原始声信号吻合程度,实验结果证明系统能够完成水声传感阵列的实时数据采集任务.     

High-Q micro-ring resonators and grating couplers for silicon-on-insulator integrated photonic circuits

An ultra-small integrated photonic circuit has been proposed,which incorporates a high-quality-factor passive micro-ring resonator(MR) linked to a vertical grating coupler on a standard silicon-on-insulator(SOI) substrate.The experimental results demonstrate that the MR propagation loss is 0.532 dB/cm with a 10μm radius ring resonator,the intrinsic quality factor is as high as 202.000,the waveguide grating wavelength response curve is a 1 dB bandwidth of 40 nm at 1540 nm telecommunication wavelengths,and the measured fiber-to-fiber coupling loss is 10 dB.Furthermore,the resonator wavelength temperature dependence of the 450 nm wide micro-ring resonator is 54.1 pm/℃.Such vertical grating coupler and low loss MR-integrated components greatly promote a key element in biosensors and high-speed interconnect communication applications.     

水下探测微电容超声波换能器线阵设计与封装

提出一种应用于水下探测的低频微电容超声波换能器阵列。在分析微电容超声波换能器阵列复合结构和工作原理的基础上,建立了换能器阵元和一维线阵的指向性表达式,并通过分析结构参数对指向性的影响,确定了阵列几何参数。针对微电容超声波换能器水下应用需求,研究了阵列水下封装方法,通过封装结构设计和封装材料的选取,完成了换能器阵列水密封装。同时,制定了换能器阵列性能测试方案,并搭建了相应的测试、探测系统,经测试换能器线阵-3dB主瓣宽度为5°,最大旁瓣级为-13.5dB,可实现水下1m范围内的目标清晰探测。实验表明,提出的微电容超声波换能器阵列设计和封装方法合理,为改善微电容超声波换能器阵列水下探测性能提供了设计依据。     

RTD在压力下的弛豫振荡特性

报道了共振隧穿二极管(RTD)在压力下的弛豫振荡特性.采用Pspice 8.0软件仿真并设计了振荡电路,测得其振荡频率达200kHz.在(100)半绝缘(SI)GaAs衬底上利用分子束外延(MBE)技术生长了AlAs/InxGa1-xAs/GaAs双势垒共振隧穿结构(DBRTS),并采用Au/Ge/Ni/Au金属化和空气桥结构成功加工出了RTD.由于RTD的压阻效应,采用显微喇曼光谱仪标定所加应力大小,对RTD在加压条件下的振荡特性进行了研究,结果表明其弛豫振荡频率大致有-17.9kHz/MPa的改变量.     

基于SiCl4/SF6的GaAs/AlAs ICP选择性干法刻蚀

报道了GaAs/AlAs的电感耦合等离子体(ICP)选择性干法刻蚀,刻蚀气体为SiCl4/SF6混合物.研究了在不同SiCl4/SF6气体配比、RF偏压电源功率和气室压力下,GaAs,AlAs的平均刻蚀速率与二者的选择比.合适的SiCl4/SF6气体比例(15/5sccm),低的RF偏压电源功率和高的气室压力将加强AlF3非挥发性生成物的形成,进而提高GaAs/AlAs的选择比.在SiCl4/SF6气体比例为15/5sccm,RF偏压电源功率为10W,主电源功率为500W,气室压力为2Pa时,GaAs/Al-As的选择比达1500以上.采用喇曼光谱仪对不同RF偏压电源功率和气室压力下,GaAs衬底被刻蚀面等离子体损伤进行了测试,表面形貌和被刻蚀侧壁分别采用原子力显微镜(AFM)和扫描电镜(SEM)进行观察.     

基于共振隧穿二极管的应力检测方法

共振隧穿二极管(RTD)具有微分负阻效应,且其共振隧穿的I-V特性随着廊力的变化而变化,这就是RTD的压阻效应.与半导体材料压阻效应的应用类似,RTD也可用于应力检测.文中研究了两种基于RTD的应力检测方法.在讨论频率-应力检测法的基础上提出了一种新颖的应力检测方法--惠斯通RTD电桥检测法.测试结果表明,基于惠斯通RTD电桥检测法得到的压阻灵敏度随偏置电压可调,町调范围达到三个数量级.     

硅基PZT热释电薄膜湿法刻蚀技术研究

通过对不同组合比的PZT薄膜湿法刻蚀技术研究,成功地配制出两种不同的刻蚀液,主要以HF、NH4F、HCl、NH4ClEDTA、HNO3为原料,NH4F、NH4Cl和EDTA的引入,有效地实现了刻蚀速率的可控性,并对PZ0.15R0.85、PZ0.3T0.7、PZ0.5T0.5和P1.1Z0.3T0.3四种薄膜进行微图形化研究,分析了刻蚀液对各种成份的刻蚀机理,通过实验,得到了分别刻蚀四种薄膜的刻蚀液的最佳配比,并对四种薄膜的刻蚀速率进行了研究。     

(Pb0.97La0.02) (Zr0.75Sn0.25-xTix) O3 反铁电陶瓷温度诱导相变效应

Pb0：97La0：02（Zr0：75Sn0：25x Ti x/O3（x D0.10, 0.105, 0.11）（PLZST） antiferroelectric ceramics with highly preferred-（110） orientation were successfully fabricated via the conventional solid-state reaction method.The antiferroelectric nature of PLZST ceramics induced by electric field was demonstrated by the dielectric constant-temperature（D-T） and the polarization-electric field（P-E） measurement. Typical phase transition from ferroelectric（FE） to antiferroelectric（AFE）, and then to paraelectric（PE） is obtained. The results indicate that the phase transition behavior is suppressed with increasing of x, and T c is remarkably shifted to higher temperature of168 ℃, 170 ℃ and 174 ℃, respectively. Besides, high phase transition current（110 6A, 810 7A and 610 7A, respectively） is obtained with temperature induced. Consequently, the excellent electric properties and the restraint between temperature and electric field would provide basis on the application of PLZST antiferroelectric ceramics in microelectronic integrated systems and sophisticated weapons systems.     

基于MEMS的压阻式超声传感器的设计与测试

A kind of piezoresistive ultrasonic sensor based on MEMS is proposed,which is composed of a membrane and two side beams.A simplified mathematical model has been established to analyze the mechanical properties of the sensor.On the basis of the theoretical analysis,the structural size and layout location of the piezoresistors are determined by simulation analysis.The boron-implanted piezoresistors located on membrane and side beams form a Wheatstone bridge to detect acoustic signal.The membrane-beam microstructure is fabricated integrally by MEMS manufacturing technology.Finally,this paper presents the experimental characterization of the ultrasonic sensor,validating the theoretical model used and the simulated model.The sensitivity reaches -116.2 dB(0 dB reference = 1 V/μbar,31 kHz),resonant frequency is 39.6 kHz,direction angle is 55°.     

Design and test of a capacitance detection circuit based on a transimpedance amplifier

This paper presents a transimpedance amplifier (TIA) capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic transducer (CMUT). In the capacitance interface, a TIA is adopted to amplify the received signal with a center frequency of 400 kHz, and finally detect ultrasound pressure. The circuit has a strong anti-stray property and this paper also studies the calculation of compensation capacity in detail. To ensure high resolution, noise analysis is conducted. After optimization, the detected minimum ultrasound pressure is 2.1 Pa, which is two orders of magnitude higher than the former. The test results showed that the circuit was sensitive to changes in ultrasound pressure and the distance between the CMUT and stumbling block, which also successfully demonstrates the functionality of the developed TIA of the analog-front-end receiver.