共查询到20条相似文献,搜索用时 31 毫秒
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1968,56(12):2149-2157
The evaluation of radar and active sonar matched filter ambiguity functions is critical to waveform choice, the proper selection of reference signals, and the ability to estimate system performance. In the radar case the evaluation is facilitated by use of the narrow-band approximation wherein Doppler distortion of the transmitted modulation function is neglected. However, modern-day sonar signals are usually broad-band with respect to the carrier frequency and long in duration so that the narrow-band approximation cannot be employed. This creates difficulties in both analytic and computer ambiguity function evaluations. Analytic difficulties arise from the inability to solve the appropriate integrals; computer difficulties, based on direct cross correlation, arise from the long computation time required. This paper shows how evaluation of the ambiguity functions of FM sonar signals having high time-bandwidth products can be greatly facilitated by asymptotic approximations derived on the basis of the principle of stationary phase. Application of the theory allows many seemingly difficult ambiguity evaluation problems involving highly complicated integrals to be solved rapidly using algebraic techniques. As examples of the theory, the cases of linear FM under constant target velocity conditions and hyperbolic (Doppler invariant) FM under constant target acceleration conditions are worked out. In addition, some interesting adjustable Doppler tolerant characteristics of a special modulation technique (parabolic FM) are described. 相似文献
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A wide-band ambiguity function featuring a finite volume of ambiguity has been proposed for location signals. The volume of
ambiguity is determined by simple identical formulas for the time and spectral forms of presentation of signals. The ambiguity
function proposed is recommended for the analysis of arbitrary location systems: radar, ultrasonic, and sonar. 相似文献
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Target position estimation in radar and sonar means joint estimation of range and angle in the presence of noise and clutter. The global behavior of a maximum likelihood (ML) position estimator, and the clutter suppression capability of the system, can be written in terms of a range-angle ambiguity function. This function depends upon signal waveform and array configuration, i.e., upon both temporal and spatial characteristics of the system. Ambiguity and variance bound analysis indicates that system bandwidth can often be traded for array size, and direction-dependent signals can be used to obtain better angle resolution without increasing the size of the array. Wide-band direction-dependent signals (temporal diversity) can be traded for large real or synthetic arrays (spatial diversity). This tradeoff is apparently exploited by some animal echolocation systems. The above insights are obtained mostly from the properties of the range-angle ambiguity function. In general, an appropriate ambiguity function should be very useful for the design and evaluation of any ML parameter estimator. System identification methods and radio navigation systems, for example, can be optimized by minimizing the volume of a multiparameter ambiguity function. 相似文献
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随着低空空域开放和无人机等航空技术的发展,对城市或郊区等电磁频谱紧张的区域开展低空目标探测愈发重要,采用5G信号作为机会照射源的外辐射源雷达在该领域展现出了广阔的应用前景。相比4G网络,5G波形方案的实现细节发生了本质的改变,因此基于不同外辐射源信号的模糊函数也存在较大差异,而现有文献对基于5G信号的外辐射源雷达模糊函数的相关研究仍然较为缺乏。本文从信号的基本结构入手,采用对比分析的方法,从理论上对5G信号和4G信号在帧结构及物理资源结构等方面存在的差异进行了详细对比;搭建了系统仿真模型,并对基于5G信号的外辐射源雷达的模糊函数进行了仿真实验;最后,针对模糊函数中的各类副峰,分析了该模糊副峰产生的原因以及可能对信号探测性能造成的影响,并对部分副峰的抑制方式进行简单阐述。该文为基于5G信号的外辐射源雷达副峰的抑制提供了新的思路和方向。 相似文献
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This paper deals with direction of arrival (DOA) estimation and blind signal separation (BSS) based on independent component
analysis (ICA) with robust capabilities. An efficient demixing procedure of complex-valued ICA is presented here, which combines
the signal-subspace demixing procedure exploiting individual signal-subspace projection and Newton’s iteration algorithm based
on maximization of the approximate negentropy of non-Gaussian signal for array signal processing. It resolves the problems
of order ambiguity and identifiability of traditional ICA for time-domain BSS. The proposed method could be directly applied
to radar, sonar, radio surveillance, and communications systems for separating signals and estimating relative DOAs of signals.
Several computer simulation examples for perturbations to the array manifold, unknown noise environments, and Rayleigh fading
channel are provided to illustrate the effectiveness of the proposed method. 相似文献
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作为处理非平稳信号的一种重要工具,模糊函数(ambiguity function,AF)已经被广泛应用于雷达信号处理、声纳技术等领域,并对线性调频信号信号的参数估计具有极好的处理能力。但对应用于众多领域的二次调频信号,模糊函数就显得无能为力了。作为Fourier变换的更广义形式,分数阶Fourier变换(Fractional Fourier transform)近年来受到了广泛关注。为解决二次调频信号的估计问题,本文研究了基于分数阶Fourier变换的模糊函数,给出了这种变换的一些新的重要性质,如共轭对称性、Moyal公式、时移性等,推导出了它与经典模糊函数、基于分数阶Fourier变换的Wigner分布、短时Fourier变换、小波变换等其他时频变换的关系。作为应用,最后本文用这种分数阶模糊函数来估计二次调频信号,应用实例的仿真结果表明了分数阶模糊函数在估计二次调频信号参数方面的可行性和有效性。 相似文献
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Tao Ran Shan Tao Zhou Siyong Wang Yue 《电子科学学刊(英文版)》2001,18(2):121-126
The phenomenon of frequency ambiguity may appear in radar or communication systems. S. Barbarossa(1991) had unwrapped the frequency ambiguity of single component uri-dersampled signals by Wigner-Ville distribution(WVD). But there has no any effective algorithm to analyze multicomponent undersampled signals by now. A new algorithm to analyze multicomponent undersampled signals by high-order ambiguity function (HAF) is proposed here. HAF analyzes polynomial phase signals by the method of phase rank reduction, its advantage is that it does not have boundary effect and is not sensitive to the cross-items of multicomponent signals. The simulation results prove the effectiveness of HAF algorithm. 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1982,28(5):817-820
In radio and sonar applications it sometimes happens that narrow-band signals, originated from a remote source and observed at a pair of receivers, differ by unknown differential phase and Doppler shift in addition to the differential delay corresponding to the range difference. The correspondence presents the joint maximum likelihood (ML) estimate of the differential delay, Doppler, and phase and examines their accuracy by deriving the Cramér-Rao bound. It is shown that the joint ML estimators are the values of the delay and Doppler that maximize the magnitude of a generalized ambiguity function analogous to the one used in radar. It is also shown that for long observation time and high enough signal-to-noise ratio there is no degradation in the accuracy of the time-delay estimator due to the additional phase and Doppler uncertainty and that the differential Doppler is uncorrelated with the differential delay and phase estimators. 相似文献
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This is a collection of articles written by members of the Underwater Acoustic Signal Processing (UASP) Technical Committee. The first article, by D. W. Tufts, deals with the history of UASP prior to 1980. In this period, initial mathematical models were developed and the first experimental investigations of underwater acoustic propagation were performed. It was also recognized during this time that there are many similarities between radar and sonar signal processing. The article by J.P. Ianniello deals with research in passive and active sonar from 1980 to the present. Work in this period included experimental verification of algorithms that had been developed in the 1960s and 1970s (e.g. for adaptive beamforming), as well as the development of new approaches, which include acoustic propagation modeling in the design of signal processing algorithms. Such processing is referred to as matched field processing. A common task in passive sonar systems is to estimate the difference in times at which different sensors receive the same signal. Time-delay estimation is a first stage that feeds into subsequent processing blocks. I. Lourtie provides a concise review of work in this field. The article by J.C. Preisig deals with underwater acoustic communications. The underwater channel has several features that make reliable communication a challenging problem. Nevertheless, progress is being made by combining results from ocean acoustic modeling, communication theory, and signal processing. The final article, by J.M.F. Moura, deals with the future of signal processing in the ocean. In addition to considering advances in detection and localization, he deals with new applications such as acoustic tomography, physical oceanography, and synthetic aperture sonar 相似文献
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DVB-S 信号作为星基外辐射源信号,在机载、舰载等远离地面辐射源的接收平台中具有较高的应用价值。该文对DVB-S 外辐射源雷达的模糊函数和分辨特性与系统几何结构之间的关系进行了全面系统的分析。文中从DVB-S 信号的特点出发,结合其作为外辐射源信号的无源雷达系统的几何结构,对信号的模糊函数进行了深入的分析,在此基础上,进一步推导了系统的分辨性能与双基地几何位置之间的关系,并提供了其作为外辐射源雷达系统的性能量化结果。理论分析和仿真结果表明DVB-S 信号是一种比较理想的可以作为外辐射源的雷达信号。 相似文献
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The ambiguity function of Chinese standard Digital Television Terrestrial Broadcasting (DTTB) signals for passive radar contains one main peak and many side peaks. The side peaks may cause the false alarms. The relative positions and the reasons for the side peaks are analyzed and a new algorithm for side peaks suppression is proposed in this paper. The algorithm, in consideration of the characteristics of the structure of the frame, can eliminate the side peaks completely in the valid Doppler observation interval by setting the reference signals to zero at equal intervals. Both the simulative and experimental results show that this algorithm can improve the performance of target detection of the passive radar based on DTTB signal. 相似文献
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We study a class of nonstationary multicomponent signals, where each component has the form a(t) exp jφ(t), where a(t) is a random amplitude function, and φ(t) is a deterministic phase function. The amplitude function consists of a stationary Gaussian process and a time varying mean. The phase and the amplitude mean are characterized by a linear parametric model, while the covariance of the amplitude function is parameterized in some general manner. This model encompasses signals that are commonly used in communications, radar, sonar, and other engineering systems. We derive the Cramer-Rao bound (CRB) for the estimates of the amplitude and phase parameters, and of functions of these parameters, such as the instantaneous frequencies of the signal components 相似文献
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Trajectory ambiguity for an active sensor is discussed in the context of a linear time-varying channel. This type of ambiguity representation preserves details of target/channel behavior that are lost in a correlative ambiguity function representation. The trajectory diagram, which is a graphical view of radar and sonar, is used to motivate the discussion. Ambiguity manifests as sets of ambiguous target trajectories: different range versus time profiles for a target that produce identical received signal phase. These trajectories provide a "trajectory domain" picture of ambiguity that is useful for signal analysis and signal design. 相似文献
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The problem of constructing frequency hop codes for use in multiuser communication systems such as multiple-access spread-spectrum communications and multiuser radar and sonar systems is addressed. Previous frequency hopping techniques are reviewed. The construction of a new family of frequency hopping codes called hyperbolic frequency hop codes is given. The concepts of multiple-access spread-spectrum communication systems and multiuser radar and sonar systems are reviewed, and it is shown that the hyperbolic frequency hop codes possess nearly ideal characteristics for use in both types of system. Specifically, in multiple-access communications the codes achieve minimum error probability, while in radar and sonar systems the codes have at most two hits in their auto- and cross-ambiguity function. Examples of address assignment for multiple-access communications systems and radar and sonar auto- and cross-ambiguity functions are also given 相似文献