Using LMS Adaptive Filter in Direct Wave Cancellation

The way to use the least-mean-square (LMS) arithmetic to cancel the direct wave for a passive radar system is introduced. The model of the direct wave is deduced. By using the LMS adaptive FIR filter, the software solution for FM passive radar system is developed instead of the hardware consumption of the existent experiment system of passive radar. Further more some simulative results are given. The simulative results indicate that using LMS arithmetic to cancel the direct wave is effective.

Simulation of Cellular Neural Networks by Wave Digital Filter Principles

Based on wave digital filter(WDF) principles, this paper presents a digital model of cellular neural networks(CNNs). The model can precisely simulate the dynamic behavior of CNNs.

DESIGN OF POLYPHASE WAVE DIGITAL FILTERS WITH APPROXIMATELY LINEAR PHASE

It is well known that IIR digital filters require quite fewer computations,comparedwith FIR filters,in order to meet stringent magnitude specifications when the phase distortioncan be tolerated.An approximately linear phase,however,can be also obtained with the IIRfilter by making use of a technique without increasing the complexity.Based on a certain numberof attenuation zeros in the pass band,a new approach is developed for the design of polyphasewave digital filters with exact magnitude responses and Chebyshev approximation of the desiredphase responses.The minimum number of attenuation zeros is estimated,and some examples areincluded.

Pspice Equivalent Circuit Model for Implementation of Surface Acoustic Wave Filter

The crystals of quartz,lithium,and piezoelectric ceramics have a piezoelectric effect as their major characteristic.The surface acoustic wave filter(SAWF) was designed by using this property.However,the experimental cost of the fabrication of SAWF is higher than that of mechanical filter or LC filter.Through the RLC(resistor,inductor and capacitor) network equivalent circuit and the interdigital transducer(IDT) equivalent circuit model,the electromotive force,the mechanical impedance of piezoelectric plate,and the wave number of Mason circuit model were researched.The equivalent circuit can be used to reduce product development costs and shorten the development cycle.Comparing simulation result by Pspice software with the theory of SAWF,the simulated waveform is similar to theory measurement,and the equivalent circuit model is verified.

Optimized Implementation for Wave Digital Filter Based Circuit Emulation on FPGA

A binary tree representation is designed in this paper for optimization of wave digital filter（WDF）implementation.To achieve this,an equivalent WDF model of the original circuit is converted into abinary tree representation at first.This WDF binary tree can then be transformed to several topologies with the same implication,since the WDF adaptors have a symmetrical behavior on their ports.Because the WDF implementation is related to field programmable gate array（FPGA）resource usage and the cycle time of emulation,choosing aproper binary tree topology for WDF implementation can help balance the complexity and performance quality of an emulation system.Both WDF-FPGA emulation and HSpice simulation on the same circuit are tested.There is no significant difference between these two simulations.However,in terms of time consumption,the WDF-FPGA emulation has an advantage over the other.Our experiment also demonstrates that the optimized WDF-FPGA emulation has an acceptable accuracy and feasibility.

Robust autopilot with wave filter for ship steering

Research was done to overcome traditional problems associated with automatic steering systems of a ship in a seaway. A ship’s dynamic model with wave disturbances was built and a wave filter was designed by means of an extended states observer (ESO). The model estimated the low frequency motion component from a heading measurement corrupted by colorednoise, so back-and-forth steering caused by high frequency wave disturbances was avoided. At the same time, a robust autopilot system, designed by variable structure control theory, was presented. Simulation results achieved in dangerous sea status show that the wave filter works very well and the autopilot has strong robustness to environmental disturbances and model perturbation, and more importantly, the frequency of rudder adjustments is reduced noticeably.

ARBITRARY E-PLANE STRIP DISCONTINUITIES AND THEIR APPLICATION TO MILLIMETER WAVE FILTERS

Various E-plane strip discontinuities are analyzed by the moment method and gener-alized network analysis technique.By introducing an idea of waveguide in a wide-sense,the effectsof the thickness of the strips are taken into account and a unified treatment of such problems isrealized.A set of curves of the equivalent circuit parameters for the discontinuities of E-planestrips are given.Two E-plane bandpass filters are designed at W-band.The experimental resultsagree well with theoretical predietions.

Polarization Filtering Method for Suppressing Surface Wave in Time-Frequency Domain

In order to suppress the surface wave in three-component seismic exploration, according to the polarization characteristics of body wave and surface wave, a time-frequency domain polarization filtering method based on wavelet transform was studied. A covariance matrix was constructed in the time-frequency domain for the three-component seismic data, measured the polarization parameters of seismic waves. Combining the corresponding eigenvalues and eigenvectors of the matrix, the elliptic rate and elevation angle were used as constraints, and the polarization filter function was built to separate the surface waves. The separated surface waves were inversely transformed and then were adaptively subtracted from the original records. After the polarization filtering suppressed the surface wave, the signal-to-noise ratio of the converted wave was effectively improved. It laid a good foundation for the next seismic data processing and seismic exploration development. The actual data processing results show that the method can effectively extract surface waves from three-component seismic records and avoid the interference of surface waves on seismic signals.

Adaptive Match-Filtering: A Biomedical Application to Identify T-Wave Alternans

T-wave alternans (TWA), consisting in an alternation of the electrocardiographic (ECG) repolarization segment (T-wave), is a promising index of the risk of sudden cardiac death. By definition, it is characterized by a frequency component, termed fTWA, that matches half heart rate. The heart-rate adaptive match filter (AMF) based method is a technique for automatic TWA identification from the digital ECG. Aim of the present study was to provide a complete technical description of the filter able to explain its methodological principles. The AMF is usually realized as a 6th order Butterworth filter with a narrow (0.12 Hz) passing band centered in fTWA. It is applied in a bidirectional fashion, so that final filtering order is 12. While extracting the TWA component, the AMF simultaneously filters out every ECG component including noise and artefacts, and thus results are very robust. Goodness of the technique was tested using 8 synthetic ECG tracings corrupted by typical noisy factors, such as white random noise, baseline wanderings, heart-rate variability, and others. Six ECG tracings were affected by 100 μV TWA, whereas two were not. Results indicate that the AMF-based method is able to prevent false-positive and false-negative detections and, thus, represents a useful tool for a reliable TWA identification.

VDTA-Based Wave Active Filter

In this paper we present a wave active filter based on Voltage Differencing Transconductance Amplifiers (VDTAs). The synthesis of active filters basically based on processing of wave quantities. The wave method is presented for basic building blocks of active filters i.e. a series inductor and parallel capacitor through which realization of various active circuits is made by appropriate connections. The proposed wave active filter is verified by realizing a 4th order low pass Butterworth filter using SPICE simulation with 0.18 μm TSMC CMOS technology parameters.

CMOS Realization of VDTA Based Electronically Tunable Wave Active Filter with Minimum Power Consumption at Low Supply Voltage ±0.82 V

This paper presents a higher order voltage and current mode low pass or high pass filter for wave active filter based on Voltage Differencing Transconductance Amplifiers (VDTAs). The wave equivalent variable technique and topological simulation as well as operational realization using wave variables techniques are proposed for basic active building blocks of wave active filters. The proposed wave equivalent technique is employed for wave active filter with the proper selection of the terminal connections. This work presented the basic element for the realizing wave active filter is the series inductor with parallel grounded capacitor. The proposed wave active filter is verified by realizing a 4th order low pass and high pass Butterworth filter with minimum power consumption at ±0.82 V using SPICE simulation with 0.18 μm TSMC CMOS technology parameters.

Directional Filtering Due to Mesospheric Wind Shear on the Propagation of Acoustic-gravity Waves

Gravity waves with periods close to the Brunt-V(a|¨)is(a|¨)l(a|¨) period of the upper troposphere are often observed at mesopause altitudes as short period,quasi-monochromatic waves.The assumption that these short period waves originate in the troposphere may be problematic because their upward propagation to the mesosphere and lower thermosphere region could be significantly impeded due to an extended region of strong evanescence above the stratopause.To reconcile this apparent paradox,an alternative explanation is proposed in this paper.The inclusion of mean winds and their vertical shears is sufficient to allow certain short period waves to remain internal above the stratopause and to propagate efficiently to higher altitudes.A time-dependent numerical model is used to demonstrate the feasibility of this and to determine the circumstances under which the mesospheric wind shears play a role in the removal and directional filtering of short period gravity waves. Finally this paper concludes that the combination of the height-dependent mean winds and the mean temperature structure probably explains the existence of short period,quasi-monochromatic structures observed in airglow images of mesopause region.

特种车辆多维载荷谱加速方法及在振动环境模拟试验中的应用

目的 解决车辆多轴轴耦合台架试验耗时长、花费大以及振动环境模拟精度低等问题。方法 将雨流投影方法运用到多维载荷加速处理中,利用传统雨流滤波法和多轴雨流投影滤波方法分别对特种车辆部件实际所受的多轴载荷进行加速处理,对加速后的多维载荷信号开展基于时域波形再现的振动环境模拟,以更有效地利用轮式车多轴轴耦合试验台开展加速疲劳试验。结果 对比加速前后的多维载荷信号,在时域、频域、损伤域基本一致的前提下,多维载荷信号时间压缩了50%,多轴振动环境的模拟精度大于80%。结论 采用该方法开展车轮加速疲劳试验,能够精确再现被试件的实际振动环境。通过实际试验验证,可以很好地再现故障出现的时间和形式,与实际野外路试结果十分吻合。

适用于直流保护的数学形态学降噪与噪声干扰识别方法

柔性直流输电系统是调节我国能源分布不均问题的重要手段,直流保护是保证柔直系统安全的重要技术。现有工程中多采用行波保护作为主保护,然而行波保护存在易受噪声影响、故障波头不易捕捉等问题,制约了其广泛应用。针对上述问题,提出数学形态学降噪与噪声干扰识别方法,并根据直流保护采样信号特点进行参数设计,用于直流保护采样信号降噪和噪声干扰的识别。首先,确定基于自适应多尺度形态滤波的直流信号降噪方法,并设计结构元素长度和形态学滤波器类型、自适应多尺度形态滤波器的滤波器阶数和步长。其次,确定基于形态学梯度变换的噪声干扰识别方法,并设计形态学梯度变换的阈值。接着,从不同角度对形态学降噪方法与现有典型信号处理方法的滤波效果进行对比分析。最后,对形态学降噪与噪声干扰识别方法和保护的配合效果进行验证。形态学降噪与噪声干扰识别方法所需采样频率较低,运算量适中,滤波效果好,对直流保护适用性好。

基于环形阵列的空间滤波器结构损伤扫描监测方法研究

本文提出了一种基于环形阵列的空间滤波器结构损伤扫描监测方法,在结构中央布置环形压电传感器阵列实现对结构的全方位扫描监测,消除了主动Lamb波空间滤波器监测方法中盲区及远场对监测效果的影响。环形阵列由直径方向不同角度的4个线阵组成,每个线阵采用主动Lamb波空间滤波监测方法对结构损伤进行监测、成像,各阵列成像结果通过PCA-小波变换进行融合对损伤位置进行判别,从而实现结构全方位损伤扫描监测,消除单个阵列损伤监测的盲区、远场及虚假成像等影响,进而获得更加准确的损伤监测结果。通过实验研究,验证了该方法的有效性和实用性。

基于巴特沃斯滤波器的特殊人群防睡眠窒息提醒装置设计

有一种特殊人群,他们在晚上处于睡眠状态时,易出现睡眠窒息现象。一旦出现睡眠窒息,将会对人体生命构成威胁。针对此问题,文章设计了一种可在睡眠窒息初期发出声、光、振动报警提示信号的系统。通过及时报警,系统能够唤醒睡眠人员,解决特殊人群面临的健康安全隐患。

基于Kalman滤波与应变信号的舰船轴系推力辨识研究

在线、实时、准确监测舰船螺旋桨推力对船-机-桨匹配设计、舰船快速性预报及推进轴系健康管理等具有重要意义。然而,受轴系振动及环境干扰等测量噪声影响,螺旋桨推力产生的微弱应变信号易被测量噪声淹没,导致难以准确测量推力。当前,一些常用的信号降噪方法,比如傅里叶变换、小波分析等均是基于纯数据降噪,未考虑测量数据中潜藏的力学机制。不同于这类降噪方法,Kalman滤波可同时考虑测量数据噪声及数据中的力学机制,对目标实现最小方差无偏估计,因而有更高的估计精度。因此,本文利用Kalman滤波结合应变测量信号提出一种螺旋桨推力高精度、在线辨识方法。以恒定转速、变转速及低频波动转速3种工况为例,研究了不同信噪比下本文方法的推力辨识精度与鲁棒性。研究表明,在信噪比仅为20 d B时,推力辨识最大相对误差仅为4.85%,因此本文方法在低信噪比下仍有很高的辨识精度与鲁棒性。同时,本文提出方法属于时域辨识方法,在转速突变、螺旋桨缠绕渔网等突发工况时亦能实时跟踪推力变化,因此可用于螺旋桨推力及轴系状态的在线、实时监测。

基于对称光纤模式选择耦合器的多波长高阶横模光纤激光器

提出并实现了一种基于对称光纤模式选择耦合器和单模-少模-单模光纤滤波器的环形腔高阶横模光纤激光器,获得了多波长、高纯度的LP11模式激光输出。实验结果表明,该激光器可以稳定地工作在单波长、双波长、三波长和四波长状态,对应的LP11模式激光纯度分别为97.60%、97.54%、97.34%和97.19%。对称光纤模式选择耦合器制造工艺简单,性能稳定,为高阶横模光纤激光的获得提供了一种新的可选方案,在光通信、光传感等领域具有潜在的应用价值。

声表面波滤波器温度敏感性仿真研究

针对不同温度场情况下任意复杂膜系结构和电路拓扑结构的声表面波(SAW)滤波器的温度敏感性精确计算问题,首先将温度场以热应力、热应变的方式耦合声/电本征方程并考虑封装模型的电磁因素,再结合分层级联算法和全波仿真技术,计算任意复杂膜系结构和电路拓扑结构的SAW滤波器的温度敏感性,实现不同温度作用下SAW滤波器频率响应曲线、频率温度系数(TCF)值、损耗、带宽及带外抑制等性能的综合分析。通过41°Y-X LiNbO_(3)/SiO_(2)/Si_poly/Si(111)复合衬底SAW滤波器的优化设计与研制,其设计优化结果与实验结果吻合较好,验证了该方法的有效性和可行性。