Method for array gain and phase uncertainties calibration based on ISM and ESPRIT

A new method for array calibration of array gain and phase uncertainties, which severely degrade the performance of spatial spectrum estimation, is presented. The method is based on the idea of the instrumental sensors method （ISM）, two well-calibrated sensors are added into the original array. By applying the principle of estimation of signal parameters via rotational invariance techniques （ESPRIT）, the direction-of-arrivals （DOAs） and uncertainties can be estimated simultaneously through eigen-decomposition. Compared with the conventional ones, this new method has less computational complexity while has higher estimation precision, what＇s more, it can overcome the problem of ambiguity. Both theoretical analysis and computer simulations show the effectiveness of the proposed method.

Modeling of the nonlinear acoustic field generated from a phased array using Gaussian superposition technique

The nonlinearity has significant effect on the ultrasonic therapy using phased ar- rays. A numerical approach is developed to calculate the nonlinear sound field generated from a phased array based on the Gaussian superposition technique. The parameters of the phased array elements are first estimated from the focal parameters using the inverse matrix algorithm; Then the elements are expressed as a set of Gaussian functions; Finally, the nonlinear sound field can be calculated using the Gaussian superposition technique. In the numerical simulation, a 64~ 1 phased array is used as the transmitter. In the linear case, the difference between the results of the Gaussian superposition technique and the Fresnel integral is less than 0.5%, which verifies the feasibility of the approach. In the nonlinear case, the nonlinear fields of single-focus modes and double-focus modes are calculated. The results reveal that the nonlinear effects can improve the focusing performance, and the nonlinear effects are related with the source pressures and the excitation frequencies.

球罐焊缝TOFD+相控阵自动化检测系统的开发和应用

TOFD或超声相控阵机器人爬行器已陆续应用于特种设备检测中,但仍存在爬行车不能沿焊缝指定检测轨迹扫查、球罐等大型设备数据线过长导致信号衰减等问题。本文将TOFD和相控阵技术有效结合,采用爬行器差速运行、手机端无线控制、超声成像数据无线传输等技术,设计出一套球罐焊缝自动检测系统,有效解决了球罐环焊缝自动检测问题。

Experimental demonstration of λ/8 DFB semiconductor laser array for 1.3 μm CWDM system

In this article,we report the first experimental demonstration of an eight-wavelength λ/8 phased-shifted laser array based on the REC technique in the 1.3 μm wavelength domain.Measurement results exhibit good linearity of lasing wavelength with+/-0.35 nm wavelength residual.The SLM property was ensured with SMSRs all larger than 38 dB.Moreover,the directmodulation performance was also tested.The experimental results show that the modulation bandwidth can reach up to 13GHz even at the small injection current of 40 mA and the measured spurious-free dynamic range(SFDR)is up to 87 dB/Hz2/3,which shows good linearity.These measurements show that REC-based λ/8 phased-shifted laser array has good modulation performance and it may find potential application in actual fiber-optic systems.

焊缝超声NDT三法比照评析

在内植典型缺陷的焊接试样上,比较了用超声衍射时差法(TOFD)和相控阵(PA)法与传统法进行检测的结果。评析了计算机成像(CI)法与传统法的缺陷检测能力、缺陷信号显示、检测成本及时间效率。指出CI法最终取代传统法的必然性与注意点。