We show that for purely frequency modulated signals one can always find a distribution which is infinitely concentrated along its instantaneous frequency. For signals that are both frequency and amplitude modulated we...
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ISBN:
(纸本)0819404098
We show that for purely frequency modulated signals one can always find a distribution which is infinitely concentrated along its instantaneous frequency. For signals that are both frequency and amplitude modulated we consider a class of distribution which are explicit functionals of the instantaneous frequency. lated
We consider dispersive propagation with damping in phase-space, and derive the Wigner distribution in terms of the initial wave and the dispersion relation. The case for no damping. that is. lossless propagation, has ...
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ISBN:
(纸本)0819454974
We consider dispersive propagation with damping in phase-space, and derive the Wigner distribution in terms of the initial wave and the dispersion relation. The case for no damping. that is. lossless propagation, has been previously considered by Cohen, and is a special case of the more general result presented here. Simple and physically revealing approximations of the Wigner distribution in terms of the initial Wigner distribution are presented. Also. exact low-order conditional moments are given and their interpretation is discussed.
Orthogonal matrix transformations form an important part of matrix-based signalprocessing applications. Systolic arrays for computing these algorithms have been developed and the size of these arrays usually depends ...
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ISBN:
(纸本)081940943X
Orthogonal matrix transformations form an important part of matrix-based signalprocessing applications. Systolic arrays for computing these algorithms have been developed and the size of these arrays usually depends directly on the size of the problem. For large matrix sizes, implementing large numbers of processors in hardware is not physically feasible. In this paper, we examine two popular orthogonal transformations, Givens rotations and householder transformations (HT), from the viewpoint of realizing a fixed-size parallel processor array that can handle large data matrices. An efficient scheduling procedure is used to compute the HT on a systolic type array, its performance is compared with that of an array designed for computing the Givens method. An important conclusion resulting from the comparison is that the performance of the HT array is superior to that for the Givens method when the matrices are larger compared to the array size.
Searching for wideband short duration chirps is an important issue in spectrum surveillance. We propose a method and apparatus, inspired by optical tomography, by which a one-dimensional signal is converted to a two-d...
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ISBN:
(纸本)0819429163
Searching for wideband short duration chirps is an important issue in spectrum surveillance. We propose a method and apparatus, inspired by optical tomography, by which a one-dimensional signal is converted to a two-dimensional image. This image has the remarkable property that it may disclose discernible structure. A chirp in additive white Gaussian noise, even undersampled, may be detected. The process is inherently linear and may be easily implemented by parallel processing or through the construction of an optoelectronic device.
This paper presents a review of some concepts associated with time-frequency distributions-- the instantaneous frequency, group delay, instantaneous bandwidth, and marginal properties-- and generalizes them in time-fr...
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ISBN:
(纸本)0819406945
This paper presents a review of some concepts associated with time-frequency distributions-- the instantaneous frequency, group delay, instantaneous bandwidth, and marginal properties-- and generalizes them in time-frequency via rotation of coordinates. This work emphasizes the need to examine time-frequency distributions in the general time-frequency plane, rather than restricting oneself to a time and/or frequency framework. This analysis leads to a generalized uncertainty principle, which has previously been introduced in radar theory. This uncertainty principle is invariant under rotation in the time-frequency plane, and should be used instead of the traditional definition of Gabor. It is desired to smooth a time-frequency distribution that is an energy density function into one that is an energy function. Most distributions are combinations of density and energy functions but the Wigner-Ville distribution is purely a density function. By using a local version of the generalized uncertainty principle, the Wigner- Ville distribution is smoothed into a signal dependent spectrogram using an iterative algorithm. It is believed that this procedure may represent, in some way an optimum removal of signal uncertainty in the time-frequency plane.
A hypothesis H is parametric if every distribution from the process defined by H belongs to a family of distributions characterized by a finite number of parameters; on the other hand, if the distribution can not be d...
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ISBN:
(纸本)0819422347
A hypothesis H is parametric if every distribution from the process defined by H belongs to a family of distributions characterized by a finite number of parameters; on the other hand, if the distribution can not be defined by a finite number of parameters, the hypothesis is nonparametric. In this paper, we analyze a detector based on the optimum permutation test, applied to nonparametric radar detection which provide good performances without a large computational work, and we compare it with the parametric test and rank test in the Neyman-Pearson sense. The computational complexity of the detector is high and its implementation in real time is difficult, due to the number of operations increase with the factorial of the number of samples. Also, we present an algorithm that reduces the computational work required. We also present the detectability characteristic of the optimum permutation test against rank test and parametric test under Gaussian noise environments and different types of target models (nonfluctuating, Swerling I and Swerling ii). The detection probability versus signal-to-noise ratio is estimated by Monte-Carlo simulations for different parameter values (N pulse, M reference samples and false alarm probability Pfa).
We describe a concept in which an array of coupled nonlinear oscillators is used for beamforming in phased array receivers. The signal that each sensing element receives, beam steered by time delays, is input to a non...
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ISBN:
(纸本)0819454974
We describe a concept in which an array of coupled nonlinear oscillators is used for beamforming in phased array receivers. The signal that each sensing element receives, beam steered by time delays, is input to a nonlinear oscillator. The nonlinear oscillators for each element are in turn coupled to each other. For incident signals sufficiently close to the steering angle. the oscillator array will synchronize to the forcing signal whereas more obliquely incident signals will not induce synchronization. The beam pattern that results can show a narrower mainlobe and lower sidelobes than the equivalent conventional linear beamformer. We present a theoretical analysis to explain the beam pattern of the nonlinear oscillator array.
This paper presents a robust algorithm for image processing using generalized reaction-diffusion equations. An edge enhancing functional is proposed for image enhancement. A number of super diffusion operators is intr...
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ISBN:
(纸本)0819432938
This paper presents a robust algorithm for image processing using generalized reaction-diffusion equations. An edge enhancing functional is proposed for image enhancement. A number of super diffusion operators is introduced for fast and effective smoothing. Statistical information is utilized for robust edge-stopping and diffusion rate estimation. A unification of computational methods is discussed. The unified computational method is employed for the numerical integration of the generalized reaction-diffusion equations. Computer experiments indicate that the present algorithm is very efficient for edge-detecting and noise-removing.
In this paper, we report on efforts to develop signalprocessing methods appropriate for the detection of man-made electromagnetic signals in the nonlinear and nonstationary underwater electromagnetic noise environmen...
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ISBN:
(纸本)0819454974
In this paper, we report on efforts to develop signalprocessing methods appropriate for the detection of man-made electromagnetic signals in the nonlinear and nonstationary underwater electromagnetic noise environment of the littoral. Using recent advances in time series analysis methods [Huang et al., 1998], we present new techniques for detection and compare their effectiveness with conventional signalprocessing methods, using experimental data from recent field experiments. These techniques are based on an empirical mode decomposition which is used to isolate signals to be detected from noise without a priori assumptions. The decomposition generates a physically motivated basis for the data.
The detection of small floating targets in an ocean environment is discussed in this paper. Because of the time-varying nature of the growler's radar returns, classical detection schemes do not work well. It is sh...
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ISBN:
(纸本)0819412767
The detection of small floating targets in an ocean environment is discussed in this paper. Because of the time-varying nature of the growler's radar returns, classical detection schemes do not work well. It is shown that these problems can be overcome if the detection is performed in the joint time-frequency plane. The effectiveness of the detection scheme is demonstrated by looking at two specific aspects of the problem: (1) detection of the target when the radar is scanning a certain sector, and (2) when the radar is dwelling in a certain azimuthal direction for a longer period of time.
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