一种自相关基音检测算法

自相关基音检测算法是语音信号处理的关键技术,算法的效率直接影响了语音信号实时处理的质量。目前有许多较好的检测算法提高了基音检测算法的效率。而自相关基音检测算法是一种时域算法,它能直接对时域信号采样值进行分帧、求短时自相关函数,并根据一定的判决准则进行清浊音判断。提供了一种自相关基音检测算法,经过实验,它在保持较好的性能的基础上提高了检测效率。     

Blind identification with periodic modulation: a time-domain approach

We propose a method for blind identification of finite impulse response (FIR) channels with periodic modulation. The time-domain formulation in terms of block signals is simple compared with existing frequency-domain formulations. It is shown that the linear equations relating the products of channel coefficients and the autocorrelation matrix of the received signal can be further arranged into decoupled groups. The arrangement reduces computations and improves accuracy of the solution; it also leads to very simple identifiability conditions and a very natural formulation of the optimal modulating sequence selection problem. The proposed optimal selection minimizes the effects of channel noise and error in autocorrelation matrix estimation; it results in a consistent channel estimate when the channel noise is white. Simulation results show that the method yields good performance. It compares favorably with an existing subspace modulation-induced-cyclostationarity method, and it is robust with respect to channel order overestimation. The effect of modulation period and threshold of the modulating sequence are also discussed.     

Empirical frequency-domain optimal parameter estimate for black-box processes

Most of the previous signal processing identification results have been achieved using either time-domain or frequency-domain algorithms. In this study, the two methods were combined to create a novel identification algorithm called the empirical frequency-domain optimal parameter (EFOP) estimate and the recursive EFOP algorithm for common linear stochastic systems disturbed with noise. A general prediction error criterion was introduced in the time-domain estimate. By minimizing the frequency-domain estimate, some general prediction error criteria were constructed for Black-box models. Then, the parameter estimation was obtained by minimizing the general prediction error criterion. This method theoretically provides the globally optimum frequency-domain estimate of the model. It has advantages in anti-disturbance performance, and can precisely identify a model with fewer sample numbers. Lastly, some simulations were carried out to demonstrate the validity of the new method.     

连续信号频域分析的教学内容编排方式

本文介绍连续信号频域分析教学内容编排方式。它首先用正交积分变换的概念引入连续信号的傅里叶变换FT;然后基于FT的延迟性质推导时域理想冲激序列的频域理想冲激序列谱,最后利用此FT对和FT的时域卷积定理及频域卷积定理导出周期信号的离散谱和采样信号的周期谱,并给出了周期信号的傅里叶级数FS展开式和证明了频域采样定理和时域采样定理。这种新的教学编排方式的优点是叙述简明、条理清晰,而且较深刻地阐述了FT理论与FS理论及采样定理的关系,有助于学生学习和掌握连续信号频域分析技术。     

基于Snake活动轮廓模型的视频跟踪分割方法

基于Snake活动轮廓模型,采用时空融合的方式,根据短时间内相邻帧的运动趋势差异相似的前提,首先将视频序列分成若干个小段,每段有k帧视频,选取段内的前两帧为关键帧,通过运动检测的方式自动得到这两帧中运动对象的大致区域;然后进行帧内Snake演变,搜索精确轮廓;最后以关键帧间运动对象形心的运动矢量预测勾勒后续帧的初始轮廓,进行帧内Snake精确轮廓定位,从而实现所有帧的视频对象分割。相比于传统方法,本文方法克服了手动绘制初始轮廓的缺点,在空域对Snake贪婪方法进行了改进而且精确度高,速度快。实验表明,本文方法成功地实现了前后帧图像之间运动对象的对应匹配关系,并通过改进后的Snake贪婪方法得到了精确的分割结果。     

A class of frequency-domain adaptive approaches to blind multichannel identification

We extend our previous studies on adaptive blind channel identification from the time domain into the frequency domain. A class of frequency-domain adaptive approaches, including the multichannel frequency-domain LMS (MCFLMS) and constrained/unconstrained normalized multichannel frequency-domain LMS (NMCFLMS) algorithms, are proposed. By utilizing the fast Fourier transform (FFT) and overlap-save techniques, the convolution and correlation operations that are computationally intensive when performed by the time-domain multichannel LMS (MCLMS) or multichannel Newton (MCN) methods are efficiently implemented in the frequency domain, and the MCFLMS is rigorously derived. In order to achieve independent and uniform convergence for each filter coefficient and, therefore, accelerate the overall convergence, the coefficient updates are properly normalized at each iteration, and the NMCFLMS algorithms are developed. Simulations show that the frequency-domain adaptive approaches perform as well as or better than their time-domain counterparts and the cross-relation (CR) batch method in most practical cases. It is remarkable that for a three-channel acoustic system with long impulse responses (256 taps in each channel) excited by a male speech signal, only the proposed NMCFLMS algorithm succeeds in determining a reasonably accurate channel estimate, which is good enough for applications such as time delay estimation.     

Detection and Location of Multiple Wiring Faults via Time–Frequency-Domain Reflectometry

In this paper, we propose a high-resolution time–frequency-domain reflectometry technique as a methodology of detection and estimation of faults on a wire. This method adopts the time–frequency cross-correlation characteristics of the observed signal in both the time and frequency domains simultaneously. The accuracy of the proposed method is verified with experiments using a radio-guide-type coaxial cable and comparing it with traditional time-domain as well as frequency-domain reflectometry methods. It is clearly shown here that the proposed algorithm produces excellent results compared to the conventional methods for single as well as multiple fault cables.      

基于相关的SFFT的卫星信号捕获算法

GPS(Global Positioning System)接收机中,常用的捕获方法有时域串行捕获方法、基于FFT( Fast Fourier Transform)的并行频率捕获方法和基于FFT的并行码相位捕获方法,但在某些应用场景下,会对卫星信号的捕获速度提出更高的要求,因此给出了一种基于相关的SFFT(Sparse Fast Fourier Transform)的卫星信号快速捕获算法。该算法结合卫星信号伪随机码的强自相关性的特性,将原有的SFFT的幅度估值去掉,利用时域串行的捕获方法,将SFFT算法中输出的大值坐标点对应的本地伪码与接收卫星信号做相关,进而捕获卫星信号。通过实验对算法进行验证,并与已有的卫星信号捕获方法进行对比,结果表明该方法能有效地运用于卫星信号捕获中,并且该算法的运算量要比传统捕获算法更低。      

Potentials of ultra-short-pulse time-domain scattering measurements

This article illustrates the potentials of ultra-short-pulse time-domain scattering measurements, and describes a facility to perform such measurements. The main advantages of measuring in the time domain are the high range resolution and the relatively simple measurement setup. A time-domain radar cross section measurement of a flat plate is performed, to illustrate the advantages of such methods over a conventional frequency-domain setup. The measurement was performed with a sampling oscilloscope, a pulse generator, and two 2-12 GHz ridged-horn antennas. Because the horns were not designed for transmitting transient signals, an additional system-response measurement, in combination with a software deconvolution algorithm, restored the impulse response of the object under test. Further processing separated the response of the object from clutter. A comparison of the time-domain data with calculated and measured frequency-domain radar cross sections shows good agreement. The high range resolution (100 ps) enabled the separation of scattering mechanisms (i.e., reflection, single and multiple diffraction). It is concluded that ultra-short-pulse time-domain measurements could be very beneficial     

Blind Receiver Design for OFDM Systems Over Doubly Selective Channels

We develop blind data detectors for orthogonal frequency-division multiplexing (OFDM) systems over doubly selective channels by exploiting both frequency-domain and time-domain correlations of the received signal. We thus derive two blind data detectors: a time-domain data detector and a frequency-domain data detector. We also contribute a reduced complexity, suboptimal version of a time-domain data detector that performs robustly when the normalized Doppler rate is less than 3%. Our frequency-domain data detector and suboptimal time-domain data detector both result in integer least-squares (LS) problems. We propose the use of the V-BLAST detector and the sphere decoder. The time-domain data detector is not limited to the Doppler rates less than 3%, but cannot be posed as an integer LS problem. Our solution is to develop an iterative algorithm that starts from the suboptimal time-domain data detector output. We also propose channel estimation and prediction algorithms using a polynomial expansion model, and these estimators work with data detectors (decision-directed mode) to reduce the complexity. The estimators for the channel statistics and the noise variance are derived using the likelihood function for the data. Our blind data detectors are fairly robust against the parameter mismatch     

基于模糊聚类的运动对象分割算法研究

为了从视频序列中分割出完整的、一致的运动视频对象,该文使用基于模糊聚类的分割算法获得组成对象边界的像素,从而提取对象。该算法首先使用了当前帧以及之前一些帧的图像信息计算其在小波域中不同子带的运动特征,并根据这些运动特征构造了低分辨率图像的运动特征矢量集;然后,使用模糊C-均值聚类算法分离出图像中发生显著变化的像素,以此代替帧间差图像,并利用传统的变化检测方法获得对象变化检测模型,从而提取对象;同时,使用相继两帧之间的平均绝对差值大小确定计算当前帧运动特征所需帧的数量,保证提取视频对象的精确性。实验结果证明该方法对于分割各种图像序列中的视频对象是有效的。     

Super-resolution reconstruction using spatio-temporal filtering

It has been known for some time that temporal dependence (motion) plays a key role in the super-resolution (SR) reconstruction of a single frame (or sequence of frames). While the impact of global time-invariant translations is relatively well known, the general motion case has not been studied in detail. In this paper, we discuss SR reconstruction for both motion models from a frequency-domain point of view. A noniterative algorithm for SR reconstruction is presented using spatio-temporal filtering. The concepts of motion-compensated windows and sinc interpolation kernels are utilized, resulting in a finite impulse response (FIR) filter realization. In the simulations, we assume a priori knowledge of the motion (optical flow), which is commonly done throughout much of the SR reconstruction literature. The proposed process is localized in nature, and this enables the selective reconstruction of desired parts of a particular frame or sequence of frames.     

基于局部相似的红外小目标跟踪算法

连续图片序列中的运动对象与其局部背景保持相对稳定。相邻图像序列的目标局部灰度分布具有相似性。针对红外小目标跟踪杂波干扰与运动模糊问题,设计了基于局部相似的目标增强方法,并提出一种基于局部相似和运动估计的跟踪算法。该算法根据目标的局部相似性构建搜索空间,采用运动估计机制缩小搜索域,然后利用时空上下文学习跟踪算法产生跟踪结果。实验表明,本文方法能够有效应对杂波干扰和运动模糊情况,实现红外小目标的稳健跟踪,且具有较好的实时性。     

基于频域块LMS算法的实时虚拟暗室测试方法

针对电磁辐射现场测试被测设备信号和干扰未知的情况,提出了一种基于频域块最小均方算法的实时虚拟暗室测试方法。该方法采用双通道接收机,根据测试通道和背景通道中干扰信号的相关性设计自适应滤波器,在频域对背景通道信号滤波以趋近测试通道中的干扰分量,采用瞬时双通道信号迭代更新滤波器系数,滤波器系数收敛后系统输出中只有被测设备信号。仿真与分析表明,该方法在背景通道有无被测设备信号泄露的情况下都能有效抑制干扰,与基于时域最小均方算法的方法相比,在滤波器长度相同的情况下其计算复杂度更低,适用于实时现场测试。     

基于回波数据的高分辨力机载SAR运动补偿

该文详细地分析了基于距离压缩数据的运动补偿和基于复图像的运动补偿的机理,提出了基于 回波数据的高分辨力机载SAR运动补偿算法。该算法采用子孔径技术,利用修改的最大对比度法提取子孔径的多普勒调频斜率,作距离压缩数据的时域运动补偿,然后用PGA作复图像的频域运动补偿。实录数据的成像实验表明,该算法能有效地克服单一运动补偿算法的场景依赖性,获得比较满意的成像质量。     

一种基于改进残差神经网络的直扩信号感知方法

非合作条件下直扩信号感知问题一直是通信对抗领域研究的热点，传统的感知方法在低信噪比条件下性能下降严重。为有效提升直扩信号感知的性能，提出了一种基于改进残差神经网络的直扩信号感知方法。首先，通过广义互相关算法，快速提取直扩信号的相关峰特性；然后，以残差神经网络为基础，融合注意力机制，建立网络模型，分析识别抽象特征；最后，在仿真的数据集中进行实验验证。结果表明，相较于时域自相关法、卷积神经网络法等，所提方法具备更好的感知效果，能够在信噪比为-16 dB的情形下有效地感知直扩信号。     

Coincident bit counting-a new criterion for image registration

A similarity measure based on the number of coincident bits in multichannel images is presented. The similarity criterion incorporated in the image registration algorithm uses a coincident bit counting (CBC) method to obtain the number of matching bits between the frames of interest. The CBC method not only performs favorably compared with traditional techniques, but also renders simpler implementation in conventional computing machines. An image registration algorithm that incorporates the CBC criterion is proposed to determine the translation motion among sequences of images. The errors caused by noise, misregistration, and a combination of these two are analyzed. Some experimental studies using low-contrast coronary images from a digital angiographic sequence are discussed. The results compare favorably with those obtained by using other nonparametric methods.     

Contour image sequence compression through motion analysis and hybrid coding method

This paper presents a motion analysis algorithm (MAA) and a hybrid coding method for contour image sequence compression. The contour image sequence consists of objects moving and rotating in a 3-D world with occlusion, shape, and size variations from frame to frame. The MAA separates the moving image sequence into several object-oriented subsequences (OOSs). In each OOS, the component is either stationary or moves smoothly, and the motion parameters can be easily estimated. The first and last frames of OOS are key frames, and the others are in-between frames. The key frames are unpredictable, and the entire frames need to be encoded. The in-between frames are compensable, and they are encoded by the motion parameter coding. The hybrid coder uses vectorgraph coding to remove spatial redundancy of the key frames and motion parameter coding to reduce the temporal redundancy of the OOSs. The motion parameters are encoded as combinations of 2-D translation, 2-D rotation, and scaling. There are many applications for contour image sequence compression. The cartoon image sequence (a sequence of line drawing sketches) and the high-frame-rate videophone for sign language transmission are good examples. Experiments show that our method encodes the contour image sequence at a very high compression ratio without losing intelligibility.     

一种稳健的语音信号检测方法

本文提出一和种基于谱相关技术的语音信号检测方法。该方法以信号幅度谱的自相关函数为基础,通过峰值检测来达到自动检测语音的目的。