一种新的最优小波基选择准则及其应用

针对分数低阶口稳定分布信号具有显著脉冲这一特性,参照最优小波包基选择的熵准则,提出了一种针对该类噪声的最优小波基选择新准则,解决了以往最优小波基选择的熵准则中,由于需计算二阶统计量而不适合分析分数低阶口稳定分布信号的问题.还得出了针对该类信号,在运用该新准则进行判别最优小波基时,只需对各个小波基函数在第1层尺度下的变换系数进行对比判别的结论,极大地减化了以往多尺度的判别过程.将新准则应用于医学超声图像消噪时,获得了较好的效果.     

二进制混沌键控信号的最佳解调

本文通过对二进制混沌键控（２ＣＳＫ）系统同步误差信号的分析，提出２ＣＳＫ的最佳解调方案，同时给出了以Ｌｏｒｅｎｚ电路为例的计算机模拟结果。     

Design Criteria for Crosstalk Interference Between Digital Signals in Multipair Cable

This paper proposes design criteria for the crosstalk interference between digital line systems operating in multipair cable, with plesiochronous and synchronous network configurations. Existing solutions are shown to be appropriate in some cases, in some other cases to be based on imperfect design criteria, and in other cases, such as the plesiochronous case, to be absent. For engineering purposes, the application of a 3 dB additional margin to the design criterion based on the classical solution should be adequate for practical application in the network.     

跳频同步信号的最佳干扰

跳频同步法较普遍以时间信息作为发方发送同步信息,具有跳频周期短、跳频点少、周期性循环规律明显等特点。基于这些特点用干扰同步信号的方式来对跳频同步信号实施同步瞄准式干扰。并探讨了跳频同步信号最佳干扰。     

Spatially Close Signals Separation via Array Aperture Expansions and Spatial Spectrum Averaging

A resolution enhancement method for estimating the direction‐of‐arrival (DOA) of signals is presented. The proposed method is by virtually expanding a real array into virtual arrays and then averaging the spatial spectrum of the virtual arrays, each of which has a different aperture size. Superior DOA resolutions are shown in comparison with the standard algorithm, MUltiple SIgnal Classification (MUSIC), for incoherent signals incident on a uniform circular array.     

伽利略伪卫星脉冲调制方案最优化研究

概述并评估了已有的几种关于GPS的脉冲图案和脉冲调制技术。由于Galileo和GPS在信号结构方面的不同,在Galileo中这些脉冲方案不能直接被采用,所以必须研究和确立新的脉冲方案方式和脉冲图案。讨论并研究了脉冲方案方法的各个要素,完成了基于Galileo信号结构(伪码,码速率,互相关性)的仿真研究并对结果进行了分析。通过仿真确立了脉冲调制的几个关键要素,并由此研究设计了一种新的Galileo伪卫星脉冲优化方案。     

Optimal Two-Stage Search for Sparse Targets Using Convex Criteria

We consider the problem of estimating and detecting sparse signals over a large area of an image or other medium. We introduce a novel cost function that captures the tradeoff between allocating energy to signal regions, called regions of interest (ROI), versus exploration of other regions. We show that minimizing our cost guarantees reduction of both the error probability over the unknown ROI and the mean square error (MSE) in estimating the ROI content. Two solutions to the resource allocation problem, subject to a total resource constraint, are derived. Asymptotic analysis shows that the estimated ROI converges to the true ROI. We show that our adaptive sampling method outperforms exhaustive search and are nearly optimal in terms of MSE performance. An illustrative example of our method in radar imaging is given.      

给定重构滤波器条件下连续信号的最佳离散表示

在重构滤波器给定的条件下,导出了最小平方意义下连续信号的最佳离散表示的傅里叶变换.为了更适应于某些应用,在推导时采用了有别于通常的内积定义,该内积诱导出的范数考虑了信号的变化速率.最佳离散表示可通过对连续信号依次进行模拟滤波、等间隔采样和数字滤波获得.此外,还把结果推广到二维信号的情形.     

Decision Bayes Criteria for Optimal Classifier Based on Probabilistic Measures

This paper addresses the high dimension sample problem in discriminate analysis under nonparametric and supervised assumptions.Since there is a kind of equivalence between the probabilistic dependence measure and the Bayes classification error probability,we propose to use an iterative algorithm to optimize the dimension reduction for classification with a probabilistic approach to achieve the Bayes classifier.The estimated probabilities of different errors encountered along the different phases of the system are realized by the Kernel estimate which is adjusted in a means of the smoothing parameter.Experiment results suggest that the proposed approach performs well.     

Class of Optimal Polynomial Window Functions for Spectral Analysis of Signals

Journal of Communications Technology and Electronics - The problem of synthesis of low-order polynomial window functions with an arbitrarily specified decay rate of spectral lobes (optimal with...     

QPSK最佳干扰研究与仿真

由于四相位绝对移相键控（QPSK）的调制方式在卫星通信中占有十分重要的地位,详细的分析了QPSK信号的调制与解调原理,并以此为基础,理论推导出用于QPSK干扰的3种干扰方式的误比特率（BER）,这三种方式包括：连续噪声干扰,单音干扰以及指向性单音干扰。通过分析仿真,得到3种干扰方式的干扰效果,证明了干扰的有效性。     

周期非均匀采样信号的重建中的优化子频带划分

对于周期非均匀采样,由于每个均匀采样流的采样率通常都是小于Nyquist率的,因此,采样信号频谱中会发生频率混叠。这表明在采样信号的重建频带内将会有多于1的谱分量。因为不是所有的与重建频带相交的谱分量都会覆盖整个重建频带,所以有必要将重建频带分成若干个子频带进行分析,构造内插函数,这样有利于减小重建所必需的最小采样率。本文提出一种优化的子频带划分方法,通过该方法在重建频带上定义子频带,能在保证重建所需的采样率最低的情况下使子频带的个数最少,这对于简化内插滤波器的结构有重要的意义。     

多分量信号的最优时频表示

利用模糊函数（AF），基于信号的先验知识，我们定义了依赖于信号的最优核表示，给出了多分量信号的最优时频表示，并讨论在掺有噪声情况下，最优核也能抑制噪声，上述思想都通过计算机做了模拟结果。     

Criteria to Improve Time-Delay Estimation of Spread Spectrum Signals in Satellite Positioning

Positioning accuracy in satellite navigation systems depends on time-delay estimation (TDE) between satellite transmitted codes and local receiver replicas. This paper explores the fundamental limits of TDE accuracy of spread spectrum signals making use of estimation theory. In particular, this contribution derives some criteria to improve positioning accuracy in the additive white Gaussian noise (multipath-free) scenario, focusing on the (satellite) transmitter side of a direct sequence spread spectrum (DS-SS) system. Three different solutions based on the minimization of the variance of the TDE are presented. The first method derives a design criterion for the shaping pulse format. The second approach outlines a method to design binary pseudorandom spreading sequences. The third solution considers a joint shaping pulse-spreading code optimization to derive band-limited, non-binary spreading waveforms. Performance of the proposed solutions is compared with that of existing DS-SS signals for current satellite positioning systems. Possible countermeasures to the effects of multipath propagation are also discussed.     

BER Performance of Finite in Time Optimal FTN Signals for the Viterbi Algorithm

In this article, we consider the faster than Nyquist (FTN) technology in aspects of the application of the Viterbi algorithm (VA). Finite in time optimal FTN signals are used to provide a symbol rate higher than the “Nyquist barrier” without any encoding. These signals are obtained as the solutions of the corresponding optimization problem. Optimal signals are characterized by intersymbol interference (ISI). This fact leads to significant bit error rate (BER) performance degradation for “classical” forms of signals. However, ISI can be controlled by the restriction of the optimization problem. So we can use optimal signals in conditions of increased duration and an increased symbol rate without significant energy losses. The additional symbol rate increase leads to the increase of the reception algorithm complexity. We consider the application of VA for optimal FTN signals reception. The application of VA for receiving optimal FTN signals with increased duration provides close to the potential performance of BER, while the symbol rate is twice above the Nyquist limit.     

On Optimal Detection of Band-Limited PAM Signals with Excess Bandwidth

PAM data transmission receivers accomplishing maximum likelihood sequence detection (MLSD) usually require a matched filter prefilter, a sampler at the symbol rate, and a Viterbi algorithm detector. When the channel is unknown or slowly changing, one must use an adaptive matched filter prefilter. We examine an alternative optimum receiver whose optimality is independent of the matched filter prefilter and which is applicable when the channel is effectively band-limited. The sampler in the proposed receiver operates at a rate faster than the data symbol rate, enabling one to replace the matched filter by a fixed low-pass filter and still ensure that the maximum likelihood detector is supplied with a set of sufficient statistics. It is shown that the matched filter is incorporated within a modified Viterbi detector without increasing the number of states in the algorithm, although the Viterbi detector must perform computations at approximately twice the usual rate. Simulations support the optimality of the new receiver and quantitatively indicate the degradation in performance experienced by some adaptive receivers previously proposed.     

地面情报雷达天线罩最佳效费比设计准则

在进行雷达天线加罩后效费比增量分析的基础上,以取得最佳效费比为最终目标,讨论了地面情报雷达天线罩的若干设计准则。     

Optimal Equalization of Discrete Signals Passed Through a Random Channel

The problem of equalizing a discrete signal that has been transmitted through a channel selected at random from an ensemble of channels is considered. Using mean-square error as the performance index, the minimum number of adjustable parameters required to achieve a given level of performance is sought. For certain special cases, it is shown that, using nonrecursive sampled data filters, the optimum tap weights are given by the eigenvectors of the matrix formed from the covariances of the channel's impulse response. A numerical algorithm is developed to find the optimum equalizer structure for a wide class of channels with the restriction that the number of channels in the given ensemble is finite. Results worked out for several examples show that the optimum equalizer structure requires significantly fewer adjustable parameters than the standard transversal equalizer in order to obtain the same level of performance.     

Two Methods for Optimal MECG Elimination and FECG Detection from Skin Electrode Signals

Two signal processing techniques for the suppression of the maternal ECG and simultaneously optimal detection of fetal ECG with respect to noise are presented. Both techniques are based on the singular value decomposition of a measurement matrix. Criteria are given in order to evaluate, a priori, electrode locations and sampling schemes for both methods. A fundamental difference with other methods is that the number of linearly independent FECG signals is not constrained to one. One of the presented techniques is a typical offline method. It is well suited for a large number of electrodes and large number of samples, which results in a better signal to noise ratio. The second technique is a typical on-line method. It gives fetal ECG signals within about 1 s, and is adaptive to changes of the transfer (e.g., due to fetal movement). It can be applied with a small number of electrodes (e.g., eight). It is shown that if three of these signals are from thoracic electrodes, the MECG suppression is guaranteed.     

Optimal Detection of Hard-Limited Data Signals in Different Noise Environments

A number of digital techniques for detecting binary antipodal signals are based on examining the polarities of the received signal samples and ignoring their amplitudes. The structure of the optimum detector for the hard-limited samples is derived, and its performance is compared to those of some commonly used schemes in impulsive as well as Gaussian noise environments. The optimum receiver forM-ary signaling based on received signal samples quantized to an arbitrary number of levels is obtained and compared to other detectors.