Lowpass and bandpass transadmittance filter using operational amplifier pole

A new topology simultaneously implementing lowpass (LP) and bandpass (BP) transadmittance filtering signals using a single operational amplifier (OA), one capacitor, and two resistors is presented. The input impedance is very high which is essential for cascading without employment of buffers. The circuit uses absolute minimum number of active and passive components. The filter employs pole-model of OA and as such has acquired suitability for extended frequency operation. The circuit permits separate adjustment of natural frequency (ω₀) and quality factor (Q) in an orthogonal manner. The circuit has low sensitivity figures unlike the reported single amplifier biquads. The PSPICE simulation results are included.     

钽酸锂晶体宽带滤波器

本文简要介绍钽酸锂晶体及器件的一些特性,对用该材料制作的21.4MHz宽带滤波器的设计、制作和测试结果作了较详细的介绍,滤波器的带宽达225kHz,矩形系数(BW_(?0dB)/BW_(3dB)为2.66,带外衰减在50dB以上。该材料在做宽带滤波器和压控振荡器方面具有优越性。     

热轧厂35kV右母线滤波装置优化

热轧厂在轧制难度大的产品时，引进的３５ｋＶ右母线滤波装置经常过流跳闸，并影响主变压器跳闸。通过现场测试，对过流跳闸原因进行综合分析，确定了设备优化改造对策。经１年多时间的实践考核证明改造是成功的。     

Automated synthesis of multiple analog circuits using evolutionary computation for redundancy-based fault-tolerance

Analog circuits are one of the most important parts of modern electronic systems and the failure of electronic hardware presents a critical threat to the completion of modern aircraft, spacecraft, and robot missions. Compared to digital circuits, designing fault-tolerant analog circuits is a difficult and knowledge-intensive task. A simple but powerful method for robustness is a redundancy approach to use multiple circuits instead of single one. For example, if component failures occur, other redundant components can replace the functions of broken parts and the system can still work. However, there are several research issues to make the redundant system automatically. In this paper, we used evolutionary computation to generate multiple analog circuits automatically and then we combined the solutions to generate robust outputs. Evolutionary computation is a natural way to produce multiple redundant solutions because it is a population-based search. Experimental results on the evolution of the low-pass, high-pass and band-stop filters show that the combination of multiple evolved analog circuits produces results that are more robust than those of the best single circuit.     

Filters of residuated lattices and triangle algebras

An important concept in the theory of residuated lattices and other algebraic structures used for formal fuzzy logic, is that of a filter. Filters can be used, amongst others, to define congruence relations. Specific kinds of filters include Boolean filters and prime filters.In this paper, we define several different filters of residuated lattices and triangle algebras and examine their mutual dependencies and connections. Triangle algebras characterize interval-valued residuated lattices.     

Accurate video text detection through classification of low and high contrast images

Detection of both scene text and graphic text in video images is gaining popularity in the area of information retrieval for efficient indexing and understanding the video. In this paper, we explore a new idea of classifying low contrast and high contrast video images in order to detect accurate boundary of the text lines in video images. In this work, high contrast refers to sharpness while low contrast refers to dim intensity values in the video images. The method introduces heuristic rules based on combination of filters and edge analysis for the classification purpose. The heuristic rules are derived based on the fact that the number of Sobel edge components is more than the number of Canny edge components in the case of high contrast video images, and vice versa for low contrast video images. In order to demonstrate the use of this classification on video text detection, we implement a method based on Sobel edges and texture features for detecting text in video images. Experiments are conducted using video images containing both graphic text and scene text with different fonts, sizes, languages, backgrounds. The results show that the proposed method outperforms existing methods in terms of detection rate, false alarm rate, misdetection rate and inaccurate boundary rate.     

NEMS diaphragm sensors integrated with triple-nano-ring resonator

Two types of circular diaphragm, made by Si and Si/SiO₂, integrated with hexagonal photonic crystal (PhC) lattice with triple-nano-ring (TNR) resonator created at the centre are proposed as nano-scale force and pressure sensor. The optimized channel drop effect of the TNR resonator brings a strong forward drop resonant peak in both the cases and with Q-factor of 1602 and 1737, respectively. The resonant wavelength peak experience red shifts upon the applied load on the circular diaphragm along the normal direction, in terms of a 2nd-order polynomial relationship. The devices can detect a wide range of applied load. Si diaphragm based micro force sensor gives minimum detectable force of 0.847 μN in the region of applied force from 10 to 20 μN. Si/SiO₂ diaphragm based pressure sensor gives minimum detectable pressure of 4.17 MPa in the region of applied pressure from 20 to 40 MPa. From the derived wavelength shift versus a given centre displacement of the diaphragm, Si diaphragm based sensor shows higher sensitivity than Si/SiO₂ diaphragm sensor.     

Crack and flaw identification in elastodynamics using Kalman filter techniques

Filter-driven optimization based on the extended Kalman filter concept is used here for the numerical solution of crack and flaw identification problems in elastodynamics. The mechanical modeling of the studied two-dimensional problem, which includes the effect of unilateral contact along the sides of the crack, is done with the help of the boundary element method. The effect of various dynamical test loads and the applicability of this method for crack and defect identification in disks are investigated. The work has been supported by the German Research Foundation (DFG). Partial support has been provided by a Greek-German Research Cooperation Grant (IKYDA2001). This support is greatfully acknowledged.     

双原型离散傅里叶变换调制滤波器组的快速设计方法

针对大规模的离散傅里叶变换(DFT)调制滤波器组设计算法复杂度高的问题,该文提出一种基于无约束优化的快速设计算法。该算法将两个原型滤波器的设计问题归结为一个无约束优化问题,将滤波器组的传递失真,混叠失真以及原型滤波器阻带能量的加权和作为目标函数。进而,采用双迭代机制来求解该优化问题。在单步迭代中,运用矩阵求逆的等效条件和Toeplitz矩阵求逆的快速算法,显著地降低了迭代的计算代价。仿真对比表明,与已有的设计算法相比,新算法计算代价低 ,可以得到整体性能更好的滤波器组,并且可以快速设计大规模的滤波器组。     

无人机载软件接收机同步方案研究

为确保无人飞机进行稳定的数据传输,该文提出了一种基于部分匹配滤波器和两级FFT的快速同步捕获算法,该算法能在搜索出同步点位置的同时,有效估计载波频偏,且计算复杂度显著下降。在动态环境中,载波多普勒频移变化剧烈,普通接收机跟踪环容易失锁,该文提出了一种基于经验值查表的载波跟踪算法,在锁频环内引入经验值查找表,环路能自适应调整滤波器带宽,任意时刻都能保证高精度跟踪。仿真实验表明,当输入信噪比高于-35 dB,载波初始多普勒频偏在12.8 kHz以内,机动载体相对于卫星转发器的径向加速度为5 m/s2(等效多普勒频移变化速度为180 Hz/s),无人机载软件接收机可以进行稳定的数据传输。