基于自适应滤波的信号分离与窄带干扰抑制

变电站复杂的电磁环境有时会对变电站电气试验工作产生干扰。基于对干扰信号的分析,讨论了自适应滤波器的基本原理,围绕最小均方误差准则以及最小均方(LMS)算法,设计了一种自适应信号分离器,并基于自适应信号分离器研究了低频窄带干扰抑制,利用快速傅里叶分解(FFT)进行了频域分析,进而实现了窄带干扰抑制,研制了一种变电站用电磁环境净空间生成装置。实验仿真结果验证了所提设计的可行性和装置的有效性,南京地区220 kV以上变电站的现场试验表明,基于该方法研制的变电站用电磁净空间生成装置能可靠抑制干扰信号,有效提升试验效率。     

继电保护装置干扰防护若干措施

高压变电站、发电厂是具有高强度电磁场环境的特殊区域，容易对继电保护装置造成干扰，使保护误动或拒动，危及系统安全稳定运行。为此，介绍了现阶段广东省所采取的若干抗干扰措施，并对这些措施的原理及实现方法进行了简单的阐述。     

一种新的SAR窄带干扰抑制方法

合成孔径雷达易受电视网、通信网等无线设备的电磁干扰,严重影响成像质量。本文在分析SAR受到的干扰特点和信号模型的基础上,提出了一种基于压缩感知的SAR窄带干扰抑制方法。该方法根据SAR回波信号和窄带干扰信号在Chirplet字典上的调频斜率参数不同,在SAR回波信号重构过程中对干扰信号进行筛选并抑制,再把去除干扰后的压缩数据利用常规SAR成像算法进行成像。仿真结果表明,该方法不仅能有效抑制窄带干扰,而且大大减少了SAR系统成像处理的数据量,验证了本文所提方法的有效性。     

天波超视距雷达流星余迹瞬态干扰抑制方法

天波超视距雷达（OTHR）易受到流星余迹回波等强瞬态干扰的影响。目前对于流星余迹的抑制方法大多需预先抑制海、地杂波,复杂度高,实用性不强。实测数据统计表明,流星余迹与地海杂波信号的分形维区别较大,可利用其作为检测识别特征。本文提出了一种基于分形检测和预测恢复的流星余迹干扰抑制方法。该方法应用分形检测,提取信号的相似性特征,找到流星余迹干扰位置,再去掉相应干扰数据段,并通过线性预测算法恢复有效数据,达到干扰抑制的目的。该方法的优点是干扰检测前无需抑制海杂波,实用性强。仿真结果表明该方法能有效的检测干扰并抑制。     

改进的SAR图像干扰抑制算法

合成孔径雷达(SAR)图像中出现干扰条纹是由电视、广播和各类通信系统辐射源的频率在系统带宽内,造成接受的信号中混有干扰信号。由于这些干扰通常具有高于系统背景噪声的功率电平,会对SAR造成不同的影响。在某些系统中SAR信号在距离频域沿着距离向相邻的点会具有一定的相关性。如果某些频谱值被干扰信号污染,则可以利用它周围的点估计出该频段的信息。基于这一想法,提出一种干扰抑制算法,能有效的估计出被干扰影响的频谱信息。当频谱中干扰信号所污染的频段的个数较多时,相比传统方法,这种方法能更为有效地估计出原始信号。     

ZPW2000系列移频信号谐波干扰处理方法研究

不平衡牵引电流与ZPW2000系列轨道电路移频信号存在共同传输通道,其中牵引回流和高次谐波成分都将对移频信号产生影响,当列车依靠CTCS-2级列车运行控制系统提供运行许可时,增加了安全运行风险。为有效去除高次谐波干扰,获取无绝缘轨道电路移频信息,设计了基于VMD与Hilbert变换相结合的移频信号处理方法。首先利用VMD将谐波干扰信号分解为若干不同频率段的IMF;然后对所有IMF求解中心频率,确定各谐波干扰频率,根据预测算法和相关性验证,确定当前无绝缘轨道电路所对应的本征模态函数;最后通过对该IMF进行Hilbert变换分析确定当前无绝缘轨道电路中移频信息。通过对仿真和实验室实测信号分析发现：该方法不但可以有效抑制模态混叠现象,使各谐波干扰成分从混合信号中准确的分离,而且能够准确求解出移频信息,为干扰条件下准确解调行车许可信号提供了借鉴意义。     

直流输电系统对通信干扰的分析及措施

介绍了高压直流输电(HVDC)系统对通信干扰的机理,重点对换流器和输电线路无线电通信干扰的横向衰减与频谱特性、大气条件的影响等进行了较深入的研究,并结合实际高压直流输电工程,提出了具体的抑制干扰的措施。     

Numerically optimized hard pulse sequences for fast frequency selective excitation and inversion

Numerically optimized hard pulse sequences were developed providing a frequency selective response of the transverse and longitudinal magnetization for several applicationsin vivo. The sequences are based on pulse trains with binomial ratios of the pulse angles and constant time intervals between the pulses. These pulse trains were systematically optimized to obtain broad Larmor frequency ranges in which the magnetization is not markedly influenced by the pulse sequence. In addition, the sequences had to provide maximum transverse magnetization or complete inversion of the magnetization beside the suppression range. Such behaviour is needed for chemical shift selective imaging, pulsed magnetization transfer, and frequency selective spectroscopyin vivo. The phase of the magnetization response is shown and adequate rephasing conditions are discussed as well as the actual phase duration. Short optimized hard pulse sequences for water and fat-selective imaging provide lowT ₂-sensitivity of the resulting magnetization. The new optimized hard pulse sequences are suitable, if optimum suppression of signals at one single point in the Larmor frequency spectrum is less important than good suppression in a larger frequency range.     

Efficient foldover suppression using SENSE

Parallel imaging techniques, which in principle represent procedures of unfolding a reduced dataset, are well known and well established in MR imaging. This paper presents a further application of one particular reconstruction method, the SENSE algorithm, considered from a different point of view to remove potential foldover in conventional images acquired with multiple receive coils. Based on the coil sensitivity information, a body coverage map in the excited plane is calculated. This is used together with the measured raw data in a SENSE-type reconstruction to optimize the signal-to-noise ratio (SNR) as well as to remove foldover reliably by unfolding the image to a larger field of view. The reconstruction is performed automatically, without any user interaction, and does not affect data acquisition. Based on phantom and in vivo studies, which retain high image quality after the removal, the potential and limits of this approach are discussed, also taking into account future scanner hardware that will support a large number of parallel receiver channels.Acknowledgement The authors would like to thank Romhild Hoogeveen from Philips Medical Systems in Best, Netherlands, for helpful discussions.     

Preprocessing of ionospheric echo Doppler spectra

The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system (WIOBSS), which adopts a discontinuous wave mechanism. After the characteristics of the ionospheric echo Doppler spectra were analyzed, the signal preprocessing was developed in this paper, which aimed at improving the Doppler spectra. The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6–7 dB. __________ Translated from Journal of Wuhan University (Natural Science), 2006, 52(1): 114–118 [译自: 武汉大学学报(理学版)]     

电气控制系统电磁干扰及抑制策略

针对电气传动控制系统现场应用中电磁干扰问题的形成及其危害,并提出了相应的抗干扰策略。     

车载通信系统设备间互调干扰研究

在车载通信系统电磁兼容（EMC）测试中,车载电台间的互调干扰测试是很重要的内容.由于系统内的互调干扰相当严重,常常可以引起电台的通信信道完全阻塞.本文就是从系统电磁兼容的角度考虑,重点阐述了互调干扰的原理和测试方法,并给出了解决互调干扰问题的一些方法.     

ZDD—12型机转接电路中铃频信号串扰的原因分析

分析了ZDD - 12型电力线载波机在远动信号转接电路中时受串扰的原因 ,并提供了简便易行的解决方法     

Separating cyclostationary signals from spectrally overlapping interference

This paper studies an algorithm about separating spectrally overlapping signals using the cyclostationary properties of signals. On the basis of direct sequence spread system (DSSS), frequency shift filter is added into the receiver of the communication system. Although the structure of frequency shift filter is more complicated than the time-domain filter, it uses both time correlations and frequency spectrum correlations so it can achieve better performances on separating the overlapping signals. After the analysis of cyclostationary characteristic and frequency spectrum correlation, the structure of the frequency shift filter can be gained. Then, a self-adaptive algorithm is utilized for the purpose of achieving optimum multidimensional tap weights of frequency shift components. The simulation results indicate that this method can efficiently separate overlapping signals, and its error rate is lower than the time-domain filter or DSSS system by two orders of magnitude on the condition that high-power interference is added into the system. __________ Translated from Journal of Southeast University (Natural Science Edition), 2005, 35(3): 333–337 (in Chinese)     

火电厂热控系统抗干扰技术

对火力发电厂中热控系统干扰的产生及抑制进行了综合分析,并有针对性地提出了一些抗干扰的技术措施.     

光伏发电直流侧共模电压干扰的抑制研究

光伏电站直流监测系统的放电管持续闪烁放电会导致通信异常和印制板烧毁,阐述了其排查、分析和处理方法。通过对现场测试波形曲线、干扰源耦合通道、印制板通信防雷回路等方面进行分析,得出其主因是由逆变器开关管工作过程中对地产生的共模电压未得到有效抑制而引起的。经过现场设备电路接地回路改造并测试验证,问题得到有效解决。在光伏电站投运前应对各相关设备及电磁干扰进行专门严格的设计和检测,可有效地抑制共模电压,提高系统性能。     

基于滑膜干扰抑制的两轮小车自平衡控制算法

新型滑板两轮小车在野外作业和城市道路巡逻等方面具有重要的应用价值,对两轮小车自平衡控制保证小车稳定可靠性运行的关键。由于两轮小车的轮动控制系统是一个多输入多输出的非线性强耦合系统,在不平稳道路中容易产生抖振。在常规的滑膜控制的基础上,引入一个非线性滑模切换面误差跟踪项,通过滑膜干扰抑制抖振,提出一种基于滑膜干扰抑制的两轮小车自平衡控制算法。构建了两轮小车的运动状态方程和平衡控制参量分析模型,通过非线性滑模切换面误差跟踪进行滑膜自平衡控制律设计,加入非线性取代积分项补偿小车抖振,提高小车平衡控制系统的鲁棒性。仿真结果表明,采用该控制算法对两轮小车进行自平衡控制过程中,具有较好的平衡性能,输出的姿态误差减少,小车的稳定性较好,实现了对两轮小车的自平衡控制和调节,且调节作用是长期,持续的,有效保障了两轮小车的稳定运行。     

窄带干扰对P波段InSAR干涉相位的影响分析

窄带干扰信号是P频段SAR回波中常见的一类射频干扰信号,它的存在会对该频段InSAR系统的干涉相位产生严重的影响。首先推导了SAR接收的窄带干扰信号的数学模型,基于该模型通过仿真分析了窄带干扰对P波段SAR图像和InSAR干涉相位的影响。结果表明,窄带干扰的存在,使SAR图像中出现较亮的干扰条带,在这些条带处,干涉条纹被完全破坏。此外,随着干信比的增加,InSAR的相干系数在下降,干涉相位标准差在增加。分析结果对P波段InSAR系统的设计具有重要意义。     

抑制DAB变换器回流功率的双重移相调制策略

双有源桥(Dual Active Bridge, DAB)变换器在传统双重移相(Dual Phase Shift, DPS)调制下,变压器两侧电压不匹配时,中小功率区域内回流功率较大。针对以上问题,提出一种抑制回流功率的双重移相(Dual Phase Shift for Reactive Power Suppression, DPS-RPS)调制策略。首先对DPS-RPS调制的工作原理进行分析并建立数学模型,基于该模型对电流应力进行优化。然后在电流应力最小化条件下分别对DPS调制和DPS-RPS调制的回流功率及电流应力大小进行对比。结果表明,相比较于DPS调制,DPS-RPS调制在中小功率区域内减小了回流功率的同时降低了电流应力。最后通过实验验证了所提DPS-RPS调制的可行性及有效性。     

基于遗传算法和傅里叶级数的局部放电窄带干扰抑制

阐述了傅里叶级数法利用原始数据来重构窄带干扰的基本思想,分析了其重构精度受频率估计偏差和随机干扰影响较大的不足.在此基础上,结合遗传优化算法提出了一种抑制局部放电信号中窄带干扰的新方法.它不需要预知窄带干扰频率的精确值,而是通过遗传算法优化选择重构参数,避免了求解冗余方程组带来的累积误差,具有较强的自适应逼近能力和抗随...