基于R半径DFT信号时频灰度特征的辐射源识别

针对通信辐射源的个体识别问题,提出一种基于R半径离散傅里叶变换(DFT)对寄生调制信号的DFT采样圆内以及采样圆外零极点进行时频灰度特征提取的新方法。以零点特征提取为例,在寄生调制信号的幅频特性于零点处表现为谷值的基础上,结合R半径DFT变换,生成时频二维灰度图,并通过边缘检测对增强后的时频二维灰度图进行图像断点检测,以完成对寄生调制信号的特征提取,通过在不同模拟发射机下寄生调制信号所携带的零点位置半径不同,说明寄生调制信号发射自不同的辐射源。仿真实验结果表明,该方法提取出的两辐射源特征差异明显,稳定性高,可靠性好,能够快速有效地完成辐射源的个体识别。     

宽开通信侦察中多信号盲分离应用研究

宽开通信侦察系统可以大大提高搜索速度,提高信号的截获概率,但如何快速有效地分离出同时截获的多信号是一个急待解决的难题,盲分离技术为多信号分离提供了一种新的思路,实验结果表明盲分离技术在宽开通信侦察中的有效性,并显示出它在通信侦察中的广阔前景。     

宽开通信侦察中多信号盲分离应用研究

宽开通信侦察系统可以大大提高搜索速度，提高信号的截获概率，但如何快速有效地分离出同时截获的多信号是一个急待解决的难题，盲分离技术为多信号分离提供了一种新的思路，实验结果表明盲分离技术在宽开通信侦察中的有效性，并显示出它在通信侦察中的广阔前景。     

基于峭度的盲分离在通信信号盲侦察中的应用

为实现复杂多信号环境下的通信信号侦察,采用一种新的盲侦察技术,即运用盲源分离算法,在没有任何先验知识的情况下分离出源信号,然后对分离的各个信号进行后续处理。提出一种改进的基于峭度的盲分离算法,可以自适应地确定激活函数。将其应用在通信信号盲侦察中,可以实现对任意源信号进行盲分离,而不管它是超高斯还是亚高斯信号。选择超高斯和亚高斯混合通信信号进行了仿真实验,结果验证了该算法的有效性。     

MSK信号的参数估计

针对通信侦察中MSK信号参数估计的实际应用,提出构造延迟相乘自混频辅助信号获取与原信号同码速率的基带脉冲,对该脉冲采用小波变换提取边沿信息并进行谱分析实现信号码速率的估计;提出采用平方律和一阶循环矩子集相结合,通过检测循环频率位置的方法实现MSK信号的载波估计.这些算法无需MSK信号的任何先验信息,从而有利于通信侦察机...     

一种基于盲分离技术的宽开通信侦察系统

通信侦察系统具有实时性要求，目前都采用宽开通信侦察系统，它可以大大提高搜索速度，提高信号的截获概率，但如何快速有效地分离出同时截获的多信号是一个急待解决的难题。文章提出一种基于盲分离技术的宽开通信侦察系统，具有良好的应用前景。     

短波信道中3G-ALE信号的载波检测方法

第三代短波通信系统的自动链路建立协议（3G-ALE）具有更高的数据速率和更强的噪声适应能力,研究3G-ALE信号的检测和参数估计技术对电子侦察和干扰具有重要意义。在推导了多径和衰落信道对信号自相关的影响后,提出一种载波检测与估计方法,即信号经过相关运算后,运用现代功率谱估计的方法,实现对3G-ALE信号的检测与载波估计,并进行性能仿真。仿真结果证明了多径衰落条件下所提出的检测方法的有效性。     

基于HOUGH变换的QPSK信号盲处理结果可信性评估

本文研究了QPSK信号盲处理结果的可靠性检验问题,提出了一种基于HOUGH变换的检验算法。该方法可在缺乏信号先验知识的条件下,利用盲处理结果并根据调制识别结果对应的信号模型构造辅助信号,将辅助信号与观测信号相关累加。在分析不同可信性假设下相关累加模值曲线特征的基础上,通过对HOUGH变换极值点聚类数是否为1的检验,来实现对信号盲处理的可信性检验。计算机仿真结果表明,本算法在较低信噪比条件下,可实现对QPSK信号盲处理结果的可信性校验。     

一种短波波段跳频信号的检澳和识别新方法

在介绍了盲源分离算法的基本理论和经典算法的基础上,给出了通过阵列天线接收混合通信信号并经过能量检测等预处理后,采用FASTICA盲分离算法分离出原始信号,然后对分离出的各个信号进行识别,以进行跳频侦察的系统模型及其仿真结果。     

基于阵列天线的无线电侦察信号盲分离

盲源分离技术有非常重要的理论意义和实用价值,在信号处理的一些领域得到了广泛应用。提出将盲源分离技术用于无线电侦察系统,实现无线电侦察多信号的盲分离。理论分析和仿真结果表明具有良好的效果。     

A note on digital filter synthesis

It is commonly assumed that digital filters with both poles and zeros in the complex z-plane can be synthesized using only recursive techniques while filters with zeros alone can be synthesized by either direct convolution or via the discrete Fourier transform (DFT). In this letter it is shown that no such restrictions hold and that both types of filters (those with zeros alone or those with both poles and zeros) can be synthesized using any of the three methods, namely, recursion, DFT, or direct convolution.     

Blind identification of ARMA channels with periodically modulatedinputs

Previous results have pointed out the importance of inducing cyclostationarity at the transmitter for blind identification of FIR communication channels. The present paper considers the blind identification problem of an ARMA (p,q) channel by exploiting the cyclostationarity induced at the transmitter through periodic encoding of the input. It is shown that causal and stable ARMA (p,q) channels can be uniquely identified from the output second-order cyclic statistics, irrespective of the location of channel poles and zeros and color of additive stationary noise, provided that the cyclostationary input has at least q+1 nonzero cycles     

Digital-filter 2nd-order element with low quantising noise for poles and zeros at low frequencies

A 2nd-order recursive digital-filter element is proposed that gives an appreciable reduction in signal quantising noise and coefficient sensitivity compared with the direct or canonic forms of filter element when the poles or the zeros are near the point Z= 1+0j. This is a modificalion to a previously published 2nd-order element that only gives an improvement when the poles are near the point Z=1+0j.     

Generalized digital Butterworth filter design

This correspondence introduces a new class of infinite impulse response (IIR) digital filters that unifies the classical digital Butterworth filter and the well-known maximally flat FIR filter. New closed-form expressions are provided, and a straightforward design technique is described. The new IIR digital filters have more zeros than poles (away from the origin), and their (monotonic) square magnitude frequency responses are maximally flat at ω=0 and at ω=π. Another result of the correspondence is that for a specified cutoff frequency and a specified number of zeros, there is only one valid way in which to split the zeros between z=-1 and the passband. This technique also permits continuous variation of the cutoff frequency. IIR filters having more zeros than poles are of interest because often, to obtain a good tradeoff between performance and implementation complexity, just a few poles are best     

Tunable/adaptive second-order IIR notch filter

A modified second-order infinite impulse response (IIR) notch filter with constrained poles and zeros is presented to eliminate or retrieve sinusoids embedded in a broadband signal. Such a filter is ideally suited to either parallel or cascaded implementation. Two classes of problems are considered. The first is where the sinusoidal frequencies are known a priori. For this case a straightforward design procedure based on a set of design characteristic graphs is used to select tunable notch filter parameters. An interesting property of the notch filter model is that it can be converted to a line enhancer by interchanging the position of the poles and zeros. The second type of problem arises when the sinusoidal frequencies are unknown and possibly varying with time. This means that an adaptive solution is required and an important consideration is the parameter estimation accuracy. For this purpose, the paper derives the Cramer–Rao lower bound for the adaptive cascaded notch filter using a frequency-domain approach. Some simulation results are included to demonstrate the effectiveness of the proposed adaptive notch filter.     

Blind system identification

Blind system identification (BSI) is a fundamental signal processing technology aimed at retrieving a system's unknown information from its output only. This technology has a wide range of possible applications such as mobile communications, speech reverberation cancellation, and blind image restoration. This paper reviews a number of recently developed concepts and techniques for BSI, which include the concept of blind system identifiability in a deterministic framework, the blind techniques of maximum likelihood and subspace for estimating the system's impulse response, and other techniques for direct estimation of the system input     

Detection and diagnosis of abrupt changes in modal characteristics of nonstationary digital signals (Corresp.)

New "instrumental" tests for detecting and diagnosing changes in the poles of a signal having unknown time-varying zeros are proposed. Numerical results for nonstationary scalar signals are given. The extension of these tests to the vector case may be used for vibration monitoring.     

Digital models for arterial pressure and respiratory waveforms

Digital models for arterial pressure pulse (APP) and respiratory volume waveforms (RVW) are proposed for efficient representation of these signals. When these signals are discrete cosine transformed (DCT), the pole-zero technique of Steiglitz-McBride (SM) (1965) gives system functions of much lower order than those obtained directly from the signals. The DCT of a bell-shaped biphasic wave needs two poles and two zeros, so the model order is fixed by the number of distinct peaks in the magnitude spectrum of the transformed APP/RVW signal. The partial fraction expansion (PFE) of the system function allows delineation of component waves present in the time signal. The angles of model poles and zeros enable easy determination of several important features from both of these signals. The model performance is evaluated using the normalized root mean-square error. A Bayes classifier using the pole angles as the feature vector performs satisfactorily when a limited number of RVWs recorded under deep and rapid maneuver are classified as normal and abnormal respiratory pathways     

Generalisation of a theorem by mitra and hurtig on positive real functions

Utilising a polar-plot approach, a theorem by Mitra and Hurtig on positive real (p.r.) functions with noninterlaced real distinct poles and zeros is shown to be a special case of a generalised theorem on p.r. functions with noninterlaced real multiple poles and zeros.