Separation of the common-mode- and differential-mode-conducted EMInoise

A device is developed to decipher common-mode and differential-mode noise from a conducted EMI noise measurement. This device is a useful tool for power supply circuit noise diagnosis and line filter design     

Coherence-Free Microwave Photonic Bandpass Filter Using a Frequency-Shifting Recirculating Delay Line

A new microwave photonic filter that realizes a high-resolution bandpass filter response with coherence-free operation and without the limitations of phase-induced intensity noise is presented in this paper. It is based on a frequency-shifting recirculating delay line, which can simultaneously achieve a multitap, high-resolution filter and a very large suppression of noise, while also enabling the use of a conventional narrow-linewidth laser source without suffering from coherent interference effects. Experimental results demonstrate a filter $Q$ value of 200 and an SNR improvement of 40.3 dB compared to conventional recirculating delay line structures.      

A real-time adaptive line enhancer hardware implementation designed for a plasma estimation application†

A real-time adaptive line enhancer hardware system has been implemented for noise cancellation in a nuclear fusion instrumentation project. The noise cancellation circuitry, realized with a standard digital signal processor (DSP) chip, uses a direct form adaptive filter and adapts using the least-mean-squares (LMS) algorithm. The noise cancellation circuitry adapts the noise filter weights to the line noise prior to an experiment. Upon initiation of the experiment, the adaption is stopped for the duration of the experiment. Experimental data with noise cancelling may be recorded during the experiment. After the experiment, noise filter weights may be read out to be included with the experimental record for possible later evaluation. The use of these hardware systems could significantly reduce the presently enormous requirements for off-line signal processing to extract plasma information. In this paper, real-time capabilities of the line enhancer circuitry for noise cancellation are demonstrated for simple examples and for the nonstationary fusion experiment data. Performance trade-offs in terms of sampling rate and filter complexity are given.     

Multistage adaptive filters for in-phase processing ofline-frequency signals

The authors describe two adaptive multistage digital filters for 50/60-Hz line-frequency signal processing in zero-crossing detectors and synchronous power systems. These filters combine a median filter with adaptive predictors, either finite-impulse response (FIR)- or infinite-impulse response (IIR)-based, thus making it possible to extract the sinusoidal signals from noise and strong disturbances without phase shifting the primary frequency signal. The median filter is used as a prefilter because it can remove deep commutation notches from the waveform. Adaptation allows the filters to track the exact instantaneous line frequency and avoids the selectivity problem encountered with a fixed filter     

A hybrid neuro-fuzzy filter for edge preserving restoration of images corrupted by impulse noise.

A new operator for restoring digital images corrupted by impulse noise is presented. The proposed operator is a hybrid filter obtained by appropriately combining a median filter, an edge detector, and a neuro-fuzzy network. The internal parameters of the neuro-fuzzy network are adaptively optimized by training. The training is easily accomplished by using simple artificial images that can be generated in a computer. The most distinctive feature of the proposed operator over most other operators is that it offers excellent line, edge, detail, and texture preservation performance while, at the same time, effectively removing noise from the input image. Extensive simulation experiments show that the proposed operator may be used for efficient restoration of digital images corrupted by impulse noise without distorting the useful information in the image.     

Removal of power line interference in signal-averagedelectrocardiography systems

A method for line interference reduction to be used in signal-averaged electrocardiography (SAECG) systems is proposed and its performance is analyzed. This new method is an adaptation of a previously reported technique for removal of line interference from conventional electrocardiograms. It involves the recording of a line reference signal simultaneous with the lead signals, so that a shifted and sealed version of it can be used to subtract line interference from the leads. It is shown that this line interference subtraction method can reduce line interference effectively and without introducing any additional noise into the ECG signal. It is also shown that Late Potential diagnostic decisions are not altered when this filter is applied. It is recommended that this technique be used in SAECG when line interference is unavoidable     

Photonic notch filter without optical coherence limitations

A new topology for a photonic notch filter that can solve the coherent interference problem in photonic signal processors is presented in this paper. It is based on a double-pass modulation technique. The key advantage of this new structure is that it completely removes the dominant phase noise limitation, which is a fundamental problem with existing incoherent processor approaches. It also enables arbitrary narrow-linewidth telecommunication-type lasers to be used with stable and robust filter operation. Extensions to obtain tunable notch frequency and wide-passband notch filter operation are presented. Results demonstrate robust notch filter operation with a narrow-linewidth source, no phase-induced intensity noise, and a vastly superior signal-to-noise ratio performance (i.e., a nearly 60-dB increase) compared with the conventional delay line notch filter. Tunable coherence-free operation of the notch filter is also shown. Finally, a new structure that not only operates without coherence limitations but also realizes a notch filter with a wide passband of more than 50% of the free spectral range is demonstrated.     

语音信号的滤波设计

在现代通信系统中,噪声会不可避免地掺杂在其中,最通用的方法就是利用滤波器来滤除这些杂波噪声。基于此,设计了FIR与IIR数字滤波器来消除语音信号中的噪音,并且使用MATLAB对其进行仿真分析,从仿真结果中可以清晰地看出两种滤波器对语音信号的处理效果。     

基于模糊理论的自适应联邦滤波算法研究

针对先验噪声统计特性与实际不符引起卡尔曼滤波精度下降的情况,提出了一种基于模糊自适应联邦卡尔曼滤波方法。算法基于模糊推理思想通过理论残差与实际残差的比值来对观测噪声协方差阵进行加权调整,实现对观测噪声统计特性的实时跟踪,在此基础上,利用信息分配因子对各子滤波器及主滤波器输出进行加权,得到滤波器的全局输出,将此输出周期性反馈给各个子滤波器以校正子滤波系统的偏差。SINS/GPS/TAN组合导航系统的仿真试验表明该算法具有更强的自适应性、滤波精度更高、鲁棒性更强。     

X射线环焊缝图像降噪及增强方法研究

为了降低X射线焊缝图像中的椒盐和高斯混合噪声,在结合中值和均值滤波优点的基础上,提出一种基于噪声强度概率识别滤波器,首先对两种噪声分离,然后根据像素点受噪声污染的概率大小,选择不同的滤波窗口,这样既保留了图像的细节又有针对性的除去了噪声;在增强部分,提出一种非线性图像增强方法,具有自动针对焊缝区域增强而非背景区域,可以有效增强环焊缝X射线图像至个人最佳视觉感受值,较传统方法增强效果好且更符合工业现场需求,最后,通过实验验证了所提降噪及增强方法的可行性及优势。     

Applications of adaptive filtering to ECG analysis: noisecancellation and arrhythmia detection

Several adaptive filter structures are proposed for noise cancellation and arrhythmia detection. The adaptive filter essentially minimizes the mean-squared error between a primary input, which is the noisy ECG, and a reference input, which is either noise that is correlated in some way with the noise in the primary input or a signal that is correlated only with ECG in the primary input. Different filter structures are presented to eliminate the diverse forms of noise: baseline wander, 60 Hz power line interference, muscle noise, and motion artifact. An adaptive recurrent filter structure is proposed for acquiring the impulse response of the normal QRS complex. The primary input of the filter is the ECG signal to be analyzed, while the reference input is an impulse train coincident with the QRS complexes. This method is applied to several arrhythmia detection problems: detection of P-waves, premature ventricular complexes, and recognition of conduction block, atrial fibrillation, and paced rhythm.     

基于自适应卡尔曼滤波的捷联去耦算法

针对捷联相控阵雷达导引头中弹体姿态干扰弹目视线角速率提取的问题,提出了基于自适应卡尔曼滤波去耦算法,引入合适的遗忘因子优化了滤波的性能,建立了噪声特性递推和预测的数学模型,联立滤波方程和噪声估计方程解决了弹目视线角速率去耦的问题,在误差的允许的范围内提取了弹目视线角速率。最后通过仿真实验表明所提算法在捷联去耦上的有效性以及相对于标准卡尔曼滤波去耦的优良性,提高了提取弹目视线角速率的精度,优化了导弹制导性能,具有较高的工程运用价值。      

An Edge‐Based Adaptive Method for Removing High‐Density Impulsive Noise from an Image While Preserving Edges

This paper presents an algorithm for removing high‐density impulsive noise that generates some serious distortions in edge regions of an image. Although many works have been presented to reduce edge distortions, these existing methods cannot sufficiently restore distorted edges in images with large amounts of impulsive noise. To solve this problem, this paper proposes a method using connected lines extracted from a binarized image, which segments an image into uniform and edge regions. For uniform regions, the existing simple adaptive median filter is applied to remove impulsive noise, and, for edge regions, a prediction filter and a line‐weighted median filter using the connected lines are proposed. Simulation results show that the proposed method provides much better performance in restoring distorted edges than existing methods provide. When noise content is more than 20 percent, existing algorithms result in severe edge distortions, while the proposed algorithm can reconstruct edge regions similar to those of the original image.     

低压电力线载波通信结合滤波器设计

低压电力线作为载波通信信道时,其通信特性并不理想,各种负载、用电设备及外界都将引起大量的噪声,给电力线载波通信带来了严重的干扰问题,从而影响电力线通信系统的性能。为了保证载波通信信号和数据的有效传输,通过电路分析并设计一种低压电力线载波通信结合滤波器,经仿真与实验该滤波器能有效过滤低压电力线载波通信信道中的各种干扰信号,从而达到了保证载波通信信号和数据的有效传输的作用。     

Noise performance of low-sensitivity active filters

The noise limitations of some important low-sensitivity RC-active filter realizations are derived; the inherent rms noise (noise from essential network resistors) that exists at the output terminals of a bandpass active filter is determined for two-integrator loop and positive impedance converter filter realizations. Output noise spectral density and total rms output noise are determined for the two-integrator loop section. The noise contributed by the essential circuit resistors and the operational amplifiers is taken into account and it is shown that exact calculation of output noise may be obtained in terms of Q factor and impedance level. The results are used to obtain the theoretical noise limitations of these low-sensitivity active filters. It is found that the deterioration in signal-to-noise ratio (SNR), due to the internal filter noise, is independent of Q factor for high Q realizations.     

基于稀疏重构的色噪声背景下未知线谱信号估计

针对色噪声背景下的未知线谱信号估计问题,该文提出一种基于分子频带处理的稀疏重构类线谱估计方法。首先,利用多速率余弦调制滤波器组对观测信号进行子带分解,得到功率谱相对平坦的子带信号。之后,在每个子带信号上,利用基于迭代最小化的稀疏学习方法进行线谱估计,并将各子带上的线谱估计结果进行频域综合滤波以及门限判决等处理。最终得到色噪声背景下的线谱估计结果。理论推导及仿真实验表明所提方法在色噪声背景下具有较好的线谱估计性能。其能够有效地去除色噪声背景,同时保留稀疏重构类线谱估计方法所具有的高频率分辨力等优点。     

Adaptive noise removal from biomedical signals using warpedpolynomials

Presents the time-warped polynomial filter (TWPF), a new interval-adaptive filter for removing stationary noise from nonstationary biomedical signals. The filter fits warped polynomials to large segments of such signals. This can be interpreted as low-pass filtering with a time-varying cutoff frequency. In optimal operation, the filter's cut-off frequency equals the local signal bandwidth. However, the author also presents an iterative filter adaptation algorithm, which does not rely on the (complicated) computation of the local bandwidth. The TWPF has some important advantages over existing adaptive noise removal techniques: it reacts immediately to changes in the signal's properties, independently of the desired noise reduction; it does not require a reference signal and can be applied to nonperiodical signals. In case of quasiperiodical signals, applying the TWPF to the individual signal periods leads to an optimal noise reduction. However, the TWPF can also be applied to intervals of fixed size, at the expense of a slightly lower noise reduction. This is the way nonquasiperiodical signals are filtered. The author presents experimental results which demonstrate the usefulness of the interval-adaptive filter in several biomedical applications: noise removal from ECG, respiratory and blood pressure signals, and base-line restoration of electroencephalograms (EEGs)     

高炮校射中弹目图像的滤波方法研究

运用基于数字图像处理技术进行高炮武器系统射击诸元校正工作中,针对弹丸与目标的图像在获取和传输过程中会受到来自电气系统和外界的干扰而产生一定的噪声信号,需要首先对图像进行预处理,滤除噪声信号这一问题,在综合分析目前典型地滤波方法的基础上,提出了采用自适应中值滤波算法进行弹目图像预处理,制定了具体的滤波算法工作流程,并通过滤波算法的仿真效果对比,证明了自适应中值滤波算法能够有效地滤除图像中的噪声,是一种快速有效的弹目图像预处理方法。     

微弱信号非线性检测在随钻电磁波中的应用

在随钻电磁波测井工程中, 随着勘探深度加深, 信号呈现越来越微弱的特性, 有效提取强噪声背景下的微弱电磁波信号对于指导随钻工程勘探具有重要的意义.传统的滤波方法仅滤除带外噪声, 带内噪声不能被很好解决, 针对此问题, 文章设计带外硬件滤波电路和带内基于最小均方算法的可变参数自适应谱线增强(adaptive line enhancer, ALE)算法来构造组合滤波算法.理论分析和仿真研究表明:该组合算法能够提高高动态、低信噪比的微弱电磁波有用信号的估计精度, 有效提高信噪比和抑制工程环境噪声的能力.该组合算法在滤除带外噪声的基础上, 对于带内高斯白噪声抑制能力提高约10 dB, 进一步解决了实际工程问题.     

一种基于互补谐振结构的宽带共模噪声滤波器

提出了一种用于高速差分信号传输的宽带共模噪声滤波器,采用在差分线正下方参考地平面上刻蚀内外互补的共面波导1/4波长谐振器和Z字形短路枝节线来实现。滤波器采用内外互补耦合λ/4开路枝节线谐振器结构,有效减小了横向尺寸,利用Z字形枝节线增大互感以改善滤波器的带内增益平坦度,最后用级联实现了共模噪声抑制阻带的展宽。仿真和测试结果表明,该滤波器在4.1~12.5 GHz频率范围内实现了20 dB的共模噪声抑制,共模阻带相对带宽(FBW)为101%,尺寸仅为0.78λ_g×0.18λ_g(15.8 mm×3.6 mm),其中λ_g为阻带中心频率处对应的波长。且该结构在实现共模噪声宽带抑制的同时,还可有效保证差分信号传输特性良好。