A New System Synchronization Technique for the Switching Satellite

A new technique for achieving system synchronization to the switching satellite is described; this technique requires only three earth stations, designated as control stations, to transmit synchronization signals. The three signals are used to measure the three space delays from the control stations to the satellite. The control stations broadcast the space delays to all other stations in the system. Thus, any other earth station can obtain synchronization passively by calculating its own space delay.     

Simple and robust methods for support vector expansions

Most support vector (SV) methods proposed in the recent literature can be viewed in a unified framework with great flexibility in terms of the choice of the kernel functions and their constraints. We show that all these problems can be solved within a unique approach if we are equipped with a robust method for finding a sparse solution of a linear system. Moreover, for such a purpose, we propose an iterative algorithm that can be simply implemented. Finally, we compare the classical SV approach with other, recently proposed, cross-correlation based, alternative methods. The simplicity of their implementation and the possibility of exactly calculating their computational complexity constitute important advantages in a real-time signal processing scenario     

Image Compression Using KLT, Wavelets and an Adaptive Mixture of Principal Components Model

In this paper, we present preliminary results comparing the nature of the errors introduced by the mixture of principal components (MPC) model with a wavelet transform and the Karhunen Loève transform (KLT) for the lossy compression of brain magnetic resonance (MR) images. MPC, wavelets and KLT were applied to image blocks in a block transform coding scheme. The MPC model partitions the space of image blocks into a set of disjoint classes and computes a separate KLT for each class. In our experiments, though both the wavelet transform and KLT obtained a higher peak signal to noise ratio (PSNR) than MPC, according to radiologists, MPC preserved the texture and boundaries of gray and white matter better than the wavelet transform or KLT.     

Detection of signals in chaos

In this paper, we present a new method for the detection of signals in “noise”, which is based on the premise that the “noise” is chaotic with at least one positive Lyapunov exponent. The method is naturally rooted in nonlinear dynamical systems and relies on neural networks for its implementation. We first present an introductory review of chaos. The subject matter selected for this part of the paper is written with emphasis on experimental studies of chaos using a time series. Specifically, we discuss the issues involved in the reconstruction of chaotic dynamics, attractor dimensions, and Lyapunov exponents. We describe procedures for the estimation of the correlation dimension and the largest Lyapunov exponent. The need for an adequate data length is stressed. In the second part of the paper we apply the chaos-based method to a difficult task: the radar detection of a small target in sea clutter     

Classification of radar clutter in an air traffic controlenvironment

The results of an experimental study aimed at the classification of radar clutter encountered on ground-based coherent scanning radar systems used for air traffic control are presented. The clutter signals of interest are primarily those due to birds and to clouds and weather systems. A historical perspective on the radar clutter classification problem is given, and related issues are discussed. The important features of radar as a sensor in an air traffic control environment are described, and physical phenomena in radar clutter and targets, which provide the physical basis for the discrimination between the different radar clutter classes, are discussed. The feature of selection/extraction procedure, which is based on the multisegment Burg algorithm, is described. The experimental evaluation of a parametric Bayes classifier and a neural network classifier is reported     

Relation between the radiation pattern of an array and the two-dimensional discrete Fourier transform

A linear wideband array with each element followed by a tapped-delay line may be considered as a two-dimensional distal filter. Accordingly, the radiation pattern of the processor may be expressed as the product of a pair of two-dimensional discrete Fourier transforms (DFT's).     

Gain-phase analysis of digital filters with applications

The article includes two fundamental sets of relations for minimum phase digital filters; the one set defines the relations between the gain and phase components, and the other set defines the relations between the group delay and gain slope components of the pulse transfer function of the filter. Two applications of these relations are considered: (i) Graphical computation of the phase characteristic of a digital filter with a prescribed gain characteristic. (ii) Computation of the gain characteristic of a linear phase digital filter.     

Fast synchronisation of an Earth station to a switching satellite

A coarse-search-synchronisation technique is described for switched time-division multiple-access systems that uses a coded search signal. It is shown that this method achieves coarse search synchronisation much faster than the burst-synchronisation method described by Rapuano and Shimasaki.