对科技期刊《信号处理》的分析研究

本文以《信号处理》刊载的论文数量、内容、作者群分布作为分析研究对象,进行了定量的分析与评价.     

A nearly-optimum signal in communication theory

The method presented in this paper enables us to obtain, starting from a physical point of view, a nearly-optimum signal for communication theory. The product of pulse duration and spectral width, referred to the positive frequency spectrum only, is 1.1814 … as compared with the minimum theoretical value 1.1802 … obtained by Hilberg and Rothe for the Weber signal. With respect to the Weber signal our proposed function offers the not-negligible advantage of analytical simplicity. Some possible applications are outlined.     

A new technique for the identification of ultrasonic flaw signals using deconvolution

The identification of ultrasonic flaw signals is a difficult task in the angle beam ultrasonic testing of welded joints due to the presence of non-relevant signals from the geometric reflectors such as weld-roots and counter-bores. This paper describes a new approach to identify ultrasonic flaw signals in such a problematic situation. A similarity function is defined as the deconvolution of a target signal by a reference signal. The similarity functions for the same type of flaws/references are symmetric bandlimited impulse-like patterns with larger amplitudes while those for different types of flaws/references are asymmetrical broad patterns with relatively smaller amplitudes. Therefore, ultrasonic signals could be identified by the pattern of the similarity function. In the initial experiments, the proposed technique showed great potential for identifying ultrasonic flaw signals in the inspection of weld joints.     

Multivariate Polynomial Minimization and Its Application in Signal Processing

We make a conjecture that the number of isolated local minimum points of a 2n-degree or (2n+1)-degree r-variable polynomial is not greater than n ^r when n 2. We show that this conjecture is the minimal estimate, and is true in several cases. In particular, we show that a cubic polynomial of r variables may have at most one local minimum point though it may have 2^r critical points. We then study the global minimization problem of an even-degree multivariate polynomial whose leading order coefficient tensor is positive definite. We call such a multivariate polynomial a normal multivariate polynomial. By giving a one-variable polynomial majored below a normal multivariate polynomial, we show the existence of a global minimum of a normal multivariate polynomial, and give an upper bound of the norm of the global minimum and a lower bound of the global minimization value. We show that the quartic multivariate polynomial arising from broad-band antenna array signal processing, is a normal polynomial, and give a computable upper bound of the norm of the global minimum and a computable lower bound of the global minimization value of this normal quartic multivariate polynomial. We give some sufficient and necessary conditions for an even order tensor to be positive definite. Several challenging questions remain open.     

Application of adaptive time-frequency decomposition in ultrasonic NDE of highly-scattering materials

In the paper, adaptive time-frequency decomposition by basis pursuit (BP) is utilized to improve ultrasonic flaw detection in highly-scattering materials as an alternative to the Wavelet Transform technique. The detection of ultrasonic pulses using the BP is described. Computer simulation was performed to verify the signal detection improvements for an ultrasonic wave embodied in white noise, and numerical results show good detection even for signal-noise ratio (SNR) of -18 dB. The improvement in detection is experimentally verified using cast steel samples with artificial flaws.     

新颖的移动代理动态数据完整性保护协议

通过引入攻击者能力来对完整性的强弱进行划分和定义，在此基础上，分析了合谋情况下对动态数据进行截断攻击的问题，并给出了一个新颖的移动代理数据保护协议，该协议通过引入反向签名机制，形成一条从源节点到当前节点的信任链，实现对漫游路径的完整性保护，很好地解决了合谋情况下对动态数据的截断攻击，为自由漫游移动代理提供了更强的完整性保护。还使用形式化方法对协议的安全属性进行了分析验证。     

传输线中信号反射的研究

现代高速电路设计中的信号完整性问题,尤其是过度的反射现象,常常造成严重的电路问题。研究了反射形成的机理,即阻抗突变引发信号反射,通过分析给出了减少反射的措施。由Altium Designer的信号完整性分析工具对设想进行了验证,仿真结果表明:适当的端接能大幅度改善传输线中信号的反射。     

UWS脉冲雷达回波低信杂比识别检测算法研究

UWS脉冲雷达属于全新体制的雷达系统,低信杂比信号检测是系统关键性技术之一。现有雷达采用的相关检测理论,不适于UWS脉冲雷达系统。通过对脉冲雷达接收信号的时域特征分析,提出波形特征矢量提取及双门限识别检测理论,给出了详细的理论分析和实际算法的实验效果。基于识别检测思想,将信号检测与特征识别进行有机结合,有效减少了数据处理步骤,对于波形保真、快速处理等具有较大优势,为远距离UWS脉冲雷达的工程化实现提供了一定的理论基础。     

A versatile signal flow graph realization of a general transfer function by using CDBA

A general synthesis procedure is given for a versatile signal flow graph realization of a general transfer function by using current differencing buffered amplifier (CDBA). The proposed configuration uses n+1 CDBAs, n capacitors and at most 2n+4 resistors. This number of resistors can be reduced to n+1 for special cases. The circuit is eligible to obtain a variety of transfer characteristics with the same common denominator polynomial, and it is easily converted to different modes of operations. It is straightforward to find the values of the passive elements from the coefficients of the transfer function to be realized. Simulations results are obtained by using commercially available active component AD844 and CMOS technology as well. All of these make the proposed circuit attractive.     

高速差分过孔的仿真分析

高速差分信号传输中也存在着信号完整性问题。差分过孔在频率很高的时候会明显地影响差分信号的完整性,现介绍差分过孔的等效RLC模型,在HFSS中建立了差分过孔仿真模型并分析了过孔尤其过孔长度对信号完整性的影响。