Novel LMS adaptive filtering algorithm with variable step size

By analyzing algorithms available for variable step size least mean square(LMS)adaptive filter,a new modified LMS adaptive filtering algorithm with variable step size is proposed,along with performance analysis based on different parameters.Compared with the existing algorithms through the simulation,the proposed algorithm has faster convergence speed and smaller steady state error.

Compact superconducting single-and dual-band filter design using multimode stepped-impedance resonator

This study presents two multimode stepped-impedance structures to design single-and dual-band filters. Transmission zeroes are introduced for the single-band filter by using dual-mode stepped-impedance resonators. The single-band filter with high selectivity is centered at 6.02 GHz and has a fractional bandwidth （FBW） of 25.6%. Four stubs （two low frequency and two high frequency ones） are connected to the rectangular patch in the center to construct a quadruple-mode resonator. The independent conditions of the center frequencies of the high and low bands of the resonator are analyzed. A dual-band filter, which operates at 1.53 GHz and 2.44 GHz with FWBs of 12.1% and 14.1%, respectively is designed. The single-and dual-band filters are both fabricated with double-sided YBCO films and they can be used in mobile and satellite communications.

COMPACT INTERLOCKED-COUPLED FILTER USING FOLDED STEPPED-IMPEDANCE RESONATORS

A microstrip interlocked-coupled bandpass filter is proposed with a markedly compact structure. The low-impedance open-end line of the quarter-wavelength Stepped-Impedance Resonator (SIR) is replaced by two open-end high-impedance lines, which not only facilitate the coupling mechanism but also provide the strong electric coupling between resonators. With the proper utilization of folded SIRs, the occupied area of coupled-resonator pair can be reduced. By applying the proposed coupled-resonator pair, the passband filter with the compact size can be realized. Good agreement between measured and simulated results is observed. The proposed filter is desirable for compact and high-performance microwave circuit applications.

COMPACT BANDPASS FILTER WITH HIGH SELECTIVITY AND WIDE STOPBAND USING SLOTTED STEPPED-IMPEDANCE RESONATOR

In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a potential finite transmission zero fz close to f0.Based on the proposed SSIR,a fourth-order Chebychev BandPass Filter (BPF) is designed at f0=1 GHz.The measured results show that a better than-65 dB rejection is achieved on both the lower and the upper stopband.Moreover,the new filter has a wide-30 dB rejection upper stopband from 1.13f0 to 6.52f0.The fabricated filter exhibits a size of The new filter has a planar topology and is easily integrated with modern portable communication systems.

Most relevant weighted filtering with one-step singular correlation recognition

Based on the recognition of one-step singular correlation and the remedying methods obtained before,the correlation properties of the neighborhood pixels and the characteristics of image de-noising were analyzed.A kind of most relevant weighted filtering method based on one-step singular correlation recognition(OSSC-MRWF)was put forward.The simulation experiments were done and the comparison with some commonly used methods under salt-and-pepper noises was made.The results show that the proposed method can not only effectively recognize salt-and-pepper noises and mend up the noise points,but also protect the original information such as the edge details very well.The accuracy and performance indicators are further improved considerably.

Static filtering and collocation in successive steps for measurements with colored noises

The theory of static filtering in successive steps with colored noises is ample scope for its application in the procedure of GPS data processing. A majority of error and round-cycle distinctness in the measurements of GPS carrier phase can be eliminated through three times of differential calculations of stations, satellites and epochs, in which the cycle beatings became isolated values. The observation error of three-differentials in the intervals between epochs results in block diagonal matrixes in the covariance matrixes, so that the desired matrixes occupy too large memory and the processing time is too long. Therefore, by using the theory of static filtering in successive steps with colored noises, the interrelation can be eliminated and can save the processing time and memory.

基于sigmoid-sinh分段函数的变步长FxLMS算法

为改善滤波-x最小均方(filtered-x least mean square,FxLMS)算法在噪声主动控制时无法兼顾收敛速度和稳态误差的问题,提出了基于sigmoid-sinh分段函数的FxLMS(SSFxLMS)算法,并引入蚁狮算法对SFxLMS(sigmoid filtered-x least mean square)、ShFxLMS(sinh filtered-x least mean square)、SSFxLMS算法的参数进行优化。分别采用高斯白噪声和实测簇绒地毯织机噪声为输入信号,采用FxLMS、SFxLMS、ShFxLMS、SSFxLMS算法进行噪声主动控制仿真,对比分析这4种算法的性能。结果表明:与其他3种算法相比,采用SSFxLMS算法对高斯白噪声和簇绒地毯织机噪声进行控制时,误差信号的平均绝对值更小,平均降噪量与收敛速度也有大幅度提升。由此可知,SSFxLMS算法有效改善了FxLMS算法无法兼顾收敛速度和稳态误差的问题,研究结果为噪声主动控制算法设计提供了一定的参考。

基于阶跃阻抗谐振器的四阶频率可调滤波器设计

提出一种基于阶跃阻抗谐振器的紧凑型四阶四零点频率可调滤波器设计。滤波器使用变容二极管加载的阶跃阻抗谐振器(VL-SIR),有效拓宽了滤波器的调谐范围。在VL-SIR之间引入交叉耦合,从而在滤波器通带近端产生一对传输零点,显著提高了滤波器的选择性。同时,引入源和负载端的交叉耦合,在通带远端生成一对传输零点,以提高带外抑制。此外,采用基于VL-SIR的频变耦合结构来实现恒定绝对带宽。仿真结果与实测结果吻合良好。测量结果显示,可调滤波器频率调谐范围为0.78~1.15 GHz,3 dB绝对带宽约为55±3 MHz,滤波器的回波损耗大于10 dB,插入损耗约为2.8~3.3 dB。

基于反步控制的特定次谐波电流补偿研究

电网中广泛采用非线性负载,由此造成的谐波污染问题日益严重,有源电力滤波器是解决谐波污染的有效手段之一。基于谐波提取算法,兼顾稳态响应以及参数选取,提出将反步法引入谐波补偿的设计,对谐波电流跟踪控制器进行重新构建。依据反步法理论进行控制器的设计,能够达到较好的稳态补偿效果,其参数的选取较易。在MATLAB/Simulink中进行PI控制与反步控制的仿真对比,结果验证了所提控制策略对特定次谐波补偿的有效性,直流侧电容电压的反步控制较PI控制超调小、响应速度快,仿真结果证明了反步控制具有更高的补偿精度以及较快的动态响应。

基于动态步长梯度下降的EKF-SLAM改进算法

现代重型货物运输所处环境日益复杂,要求AGV-SLAM算法具备更高的鲁棒性和准确性以实现高精确装卸作业.因此,本文提出基于动态步长梯度下降的改进EKF-SLAM算法.首先对AGV行进过程建模分析,分别建立AGV的运动学模型和观测模型.考虑到EKF-SLAM算法在状态估计时可能引入的截断误差问题,本文针对AGV自身位姿和环境特征位置预测估计精确度较低的问题,提出了一种改进算法.该算法引入梯度下降算法,并结合动态步长策略,步长的取值与AGV系统的前进速度、采样时间正相关.仿真结果表明,该改进算法相较于标准EKF-SLAM算法,在停车场数据集下能够快速生成更优的估计路标和路径,从而在一定程度上提高了传统算法的鲁棒性和准确性,具有行业应用的参考价值.

一种基于自适应滤波的VFRM无位置传感器控制

可变磁通磁阻电机(variable flux reluctance machine,VFRM)的空间磁链谐波和逆变器非线性等因素会在扩展反电动势中产生谐波,进而降低无位置传感器的控制精度。为解决此问题,首先通过构建双曲正切函数滑模观测器,减小传统滑模观测器造成的高频抖振和相位延迟;然后分析了扩展反电动势谐波对转子位置估计的影响,并在此基础上提出了一种变步长最小二乘(least mean square,LMS)自适应滤波算法,准确地提取了扩展反电动势的基波分量,提高了转子位置和转速的估计精度。实验结果表明,所提算法与传统定步长LMS自适应滤波算法相比具有更好的控制性能。

一种求解非线性互补问题的外梯度-Filter方法

结合Josephy-Newton方法,建立了一种不含价值函数的求解非线性互补问题的全局策略.该策略基于外梯度步和Filter技术,提出一个外梯度-Filter算法.此算法中的外梯度步可以减少与最优解之间的距离,从而使该算法具有全局收敛性.在适当的条件下,该算法还具有超线性收敛性.

柔性直流光纤电流互感器阶跃响应特性研究

传统直流光纤电流互感器无法满足柔性直流输电工程的高速响应需求,因此需要研究直流光纤电流互感器的阶跃响应特性及其动态性能改善方法。文中结合直流光纤电流互感器的离散数学模型,对其动态特性进行了全面的仿真、计算和实验研究,结果表明:影响直流光纤电流互感器阶跃响应特性的关键参数是渡越时间、前向通道增益、滤波器阶数和通讯延迟。搭建了直流光纤电流互感器阶跃响应测试平台,经参数优化后的直流光纤电流互感器的阶跃响应上升时间小于50μs,满足相关应用要求。

基于变步长凸组合LMS自适应滤波高原动态血氧检测系统设计

针对基于光电检测方法的血氧仪只能在静止状态下测试血氧饱和度(血氧)的问题,提出一种基于变步长凸组合LMS自适应滤波动态血氧检测方法。方法对原始光电描记脉搏波信号经预处理后,通过固步长与变步长LMS自适应算法组合,以三轴加速度计采集信号作为运动噪声参考信号,获得理想脉搏波信号再准确计算血氧值。在此基础上,开发了一套基于物联网的穿戴式高原血氧检测系统,经过模拟正常行走及在不同海拔条件下测试,最大误差不超过4%,验证了算法的有效性和准确性。结果显示,基于物联网的血氧监测系统对于高原旅游中高原反应的实时监测与提醒具有实际意义。

铁路机车电台设备电磁发射测量专用带阻滤波器设计

铁路无线通信设备发射的信号往往较强,因而在电磁发射测量过程中,极易导致测量接收机出现乱真响应。基于450 MHz无线列调机车电台通信设备的工作特性,研制了一种新型可调阶跃阻抗谐振器腔体窄带带阻滤波器,用于避免电磁发射测量过程中所引起的测量接收机过载问题。通过软件仿真和实物测试,验证了所设计的带阻滤波器较传统腔体滤波器减少了阻带带宽,具有良好的通带特性,且结构简单,体积较小,可以很好地满足机车电台电磁发射测量的需求,有效提高电磁发射测量结果的准确性。

Step Sized DGS结构的毫米波带通滤波器的设计

文中利用一种渐变尺寸的 DGS(Defected Ground Structure)结构的带阻特性,以改善毫米波滤波器的阻带性能.仿真及实验结果证明了优化的渐变尺寸周期 DGS 结构能有效地改善滤波器带外抑制特性,同时对通带内插入损耗影响较小.

OPTIMAL DISTRIBUTED FUSION ALGORITHM WITH ONE-STEP OUT-OF-SEQUENCE ESTIMATES

The transmission modes of multi-hop and broadcasting for Wireless Sensor Networks(WSN)often make random and unknown transmission delays appear,so multisensor data fusion based ondelayed systems attracts intense attention from lots of researchers.The existing achievements for thedelayed fusion all focus on Out-Of-Sequence Measurements(OOSM)problem which has many dis-advantages such as high communication cost,low computational efficiency,huge computational com-plexity and storage requirement,bad real-time performance and so on.In order to overcome theseproblems occurred in the OOSM fusion,the Out-Of-Sequence Estimates(OOSE)are considered tosolve the delayed fusion for the first time.Different from OOSM which belongs to the centralized fusion,the OOSE scheme transmits local estimates from local sensors to the central processor and is thus thedistributed fusion;thereby,the OOSE fusion can not only avoid the problems suffered in the OOSMfusion but also make the design of fusion algorithm highly simple and easy.Accordingly,a novel optimallinear recursive prediction weighted fusion method is proposed for one-step OOSE problem in this letter.As a tradeoff,its fusion accuracy is slightly lower than that of the OOSM method because the currentOOSM fusion is a smooth estimate and OOSE gets a prediction estimate.But,the smooth result of theOOSE problem also has good fusion accuracy.Performance analysis and computer simulation show thatthe total performance of the proposed one-step OOSE fusion algorithm is better than the current one-step OOSM fusion in the practical tracking systems.

Particle filter with importance density function generated by updated system equation

The current measurement was exploited in a more efficient way. Firstly, the system equation was updated by introducing a correction term, which depends on the current measurement and can be obtained by running a suboptimal filter. Then, a new importance density function(IDF) was defined by the updated system equation. Particles drawn from the new IDF are more likely to be in the significant region of state space and the estimation accuracy can be improved. By using different suboptimal filter, different particle filters(PFs) can be developed in this framework. Extensions of this idea were also proposed by iteratively updating the system equation using particle filter itself, resulting in the iterated particle filter. Simulation results demonstrate the effectiveness of the proposed IDF.

Lattice structure adaptive IIR notch filter based on least square kurtosis

A new variable step-size algorithm for a second-order lattice form structure adaptive infinite impulse response （IIR） notch filter to detection and estimation frequency of sinusoids in Gaussian noises is proposed. Utilizing least square kurtosis of output signals as a cost function, the new gradient-based algorithm to update frequency of the adaptive IIR notch filter and the new variable step-size algorithm are given. The computer simulation results show that the proposed algorithm has better ability in suppressing colored Gaussian noises and better accuracy in estimating parameters at low SNR than previous algorithms.

NOVEL FIBER GRATING SENSOR DEMODULATION TECHNIQUE BASED ON OPTICAL WAVELET FILTERING

The optical wavelet filter is designed. It can filter and choose frequency swiftly. It can realize demodulation of distributed fiber Bragg grating（FBG） measurement system. Its scanning resolution and scanning period depend on wavelet function. Wavelet function is controlled by computer. Compared to conventional scan filter, optical wavelet filtering has some advantages such as simple structure, high scan frequency, high resolution and good linearity. At last, the error of optical wavelet filter scanning procedure is analyzed. Scanning step length refers to the shifting of optical wavelet window＇s central frequency. It affects system precision directly. If scanning step length is different, the measured signal is different. The methods of reducing step length guarantee scanning periodic time are presented.