The use of wireless personal communication networks (PCN) to increase the capacity of cellular radio systems is a topic currently receiving much attention. In addition to the increase in capacity one achieves by going...
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ISBN:
(纸本)081940943X
The use of wireless personal communication networks (PCN) to increase the capacity of cellular radio systems is a topic currently receiving much attention. In addition to the increase in capacity one achieves by going to a microcellular system, one can increase the spectral efficiency even further by allowing the PCN to overlay a frequency band which is already occupied with narrowband waveforms. Various signalprocessing techniques can be used advantageously in this regard, and such techniques are outlined below.
We review, recent work on defining the time-frequency moments of a signal. Expressions are given for moments dropt(m)drop(omega), and of all orders n, m, in terms of the amplitude and phase of the signal and spectrum....
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ISBN:
(纸本)0819441880
We review, recent work on defining the time-frequency moments of a signal. Expressions are given for moments dropt(m)drop(omega), and of all orders n, m, in terms of the amplitude and phase of the signal and spectrum. Knowing the time-frequency moments is of interest for a variety of reasons. including their potential utility as features for classification of nonstationary signals, and also because from the moments one call construct the time-varying spectral density, or approximate it using a few moments.
Gabriel, a second-generation digital signal-processing (DSP) design environment, is described. The Gabriel experimental signal-processing software performs non-real-time algorithm simulations and code synthesis for re...
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Gabriel, a second-generation digital signal-processing (DSP) design environment, is described. The Gabriel experimental signal-processing software performs non-real-time algorithm simulations and code synthesis for real-time hardware based on programmable DSPs. Gabriel eases code development for architectures that are not easy targets for conventional compilers. The model of compilation used by Gabriel is discussed at length. Modification of the model to run in real time, target architectures, and scheduling are examined.
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 is written to provide both a historical review of past work and an overview of recent advances in time-frequency signal analysis and time-varying higher-order spectra. The paper is organized as follows: Sec...
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ISBN:
(纸本)0819412767
This paper is written to provide both a historical review of past work and an overview of recent advances in time-frequency signal analysis and time-varying higher-order spectra. The paper is organized as follows: Section 1 discusses the need for time-frequency signal analysis (TFSA), as opposed to either time or frequency analysis. Section 2 covers the many faceted developments which occurred in TFSA in the 1980s and early 1990s. It covers bilinear or energetic time-frequency distributions (TFDs). Section 3 deals with a generalization of bilinear TFDs to multilinear Polynomial TFDs and their relationship to time-varying higher order spectra (TVHOS). Section 4 provides a coverage of the Wigner-Ville trispectrum, which is a particular TVHOS, used for analyzing signals affected by Gaussian multiplicative noise. Section 5 is devoted to conclusions.
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.
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