55 research outputs found
Parameter estimation of models with many damped complex exponentials
Parameter estimation techniques for data modelled as a sum of damped complex
exponentials are proving to be a successful alternative to Fourier transform methods for spectral estimation
Target Recognition Using Late-Time Returns from Ultra-Wideband, Short-Pulse Radar
The goal of this research is to develop algorithms that recognize targets by exploiting properties in the late-time resonance induced by ultra-wide band radar signals. A new variant of the Matrix Pencil Method algorithm is developed that identifies complex resonant frequencies present in the scattered signal. Kalman filters are developed to represent the dynamics of the signals scattered from several target types. The Multiple Model Adaptive Estimation algorithm uses the Kalman filters to recognize targets. The target recognition algorithm is shown to be successful in the presence of noise. The performance of the new algorithms is compared to that of previously published algorithms
The use of late time response for stand off onbody concealed weapon detection
A new system for remote detection of onbody concealed weapons such as knives and
handheld guns at standoff distances presented in this thesis. The system was designed,
simulated, constructed and tested in the laboratory. The detection system uses an Ultrawide
Band (UWB) antenna to bombard the target with a UWB electromagnetic pulse.
This incident pulse induces electrical currents in the surface of an object such as a knife,
which given appropriate conditions these currents generate an electromagnetic
backscatter radiation. The radiated waves are detected using another UWB antenna to
obtain the Late Time Response (LTR) signature of the detected object. The LTR
signature was analysed using the Continuous Wavelet Transform (CWT) in order to
assess the nature and the geometry of the object.
The thesis presents the work which divided into two related areas. The first involved the
design, simulation, fabrication, and testing of an Ultra-wide Band (UWB) antenna with
operating bandwidth of 0.25 – 3.0 GHz and specific characteristics. Simulated and
measured results show that the designed antenna achieves the design objectives which
are, flat gain, a VSWR of around unity and distortion less transmitted narrow pulse. The
operating bandwidth was chosen to cover the fundamental Complex Natural Resonance
(CNR) modes of most firearms and to give a fine enough time resolution. The second
area covered by this thesis presents a new approach for extract target signature based on
the Continuous Wavelet Transform (CWT) applied to the scattering response of onbody
concealed weapons. A series of experiments were conducted to test the operation of the
detection system which involved onbody and offbody objects such as, knives, handheld
guns, and a number of metallic wires of various dimensions. Practical and simulation
results were in good agreement demonstrating the success of the approach of using the
CWT in analyzing the LTR signature which is used for the first time in this work.
Spectral response for every target could be seen as a distribution in which the energy
level and life-time depended on the target material and geometry. The spectral density
provides very powerful information concerning target unique signature
Bias Removal Approach in System Identification and Arma Spectral Estimation
Electrical Engineerin
The theory of linear prediction
Linear prediction theory has had a profound impact in the field of digital signal processing. Although the theory dates back to the early 1940s, its influence can still be seen in applications today. The theory is based on very elegant mathematics and leads to many beautiful insights into statistical signal processing. Although prediction is only a part of the more general topics of linear estimation, filtering, and smoothing, this book focuses on linear prediction. This has enabled detailed discussion of a number of issues that are normally not found in texts. For example, the theory of vector linear prediction is explained in considerable detail and so is the theory of line spectral processes. This focus and its small size make the book different from many excellent texts which cover the topic, including a few that are actually dedicated to linear prediction. There are several examples and computer-based demonstrations of the theory. Applications are mentioned wherever appropriate, but the focus is not on the detailed development of these applications.
The writing style is meant to be suitable for self-study as well as for classroom use at the senior and first-year graduate levels. The text is self-contained for readers with introductory exposure to signal processing, random processes, and the theory of matrices, and a historical perspective and detailed outline are given in the first chapter
Structural dynamics analysis in the presence of unmeasured excitations
Methods for comprehensive structural dynamic analysis generally employ input-output
modal analysis with a mathematical model of structural vibration using excitation and
response data. Recently operational modal analysis methods using only vibration
response data have been developed. In this thesis, both input-output and operational
modal analysis, in the presence of significant unmeasured excitations, is considered.
This situation arises when a test structure cannot be effectively isolated from ambient
excitations or where the operating environment imposes dynamically-important
boundary conditions.
The limitations of existing deterministic frequency-domain methods are assessed. A
novel time-domain estimation algorithm, based on the estimation of a discrete-time
autoregressive moving average with exogenous excitation (ARMAX) model, is
proposed. It includes a stochastic component to explicitly account for unmeasured
excitations and measurement noise. A criterion, based on the sign of modal damping, is
incorporated to distinguish vibration modes from spurious modes due to unmeasured
excitations and measurement noise, and to identify the most complete set of modal
parameters from a group of estimated models.
Numerical tests demonstrate that the proposed algorithm effectively identifies vibration
modes even with significant unmeasured random and periodic excitations. Random
noise is superimposed on response measurements in all tests. Simulated systems with
low modal damping, closely spaced modes and high modal damping are considered
independently. The accuracy of estimated modal parameters is good except for degreesof-
freedom with a low response level but this could be overcome by appropriate
placement of excitation and response measurement points.
These observations are reflected in experimental tests that include unmeasured periodic
excitations over 200% the level of measured excitations, unmeasured random
excitations at 90% the level of measured excitations, and the superposition of periodic
and random unmeasured excitations. Results indicate advantages of the proposed
algorithm over a deterministic frequency domain algorithm. Piezoceramic plates are
used for structural excitation in one experimental case and the limitations of distributed
excitation for broadband analysis are observed and characterised in terms of actuator
geometry and modal deformation.
The ARMAX algorithm is extended for use with response measurements exclusively.
Numerical and experimental tests demonstrate its performance using time series data
and correlation functions calculated from response measurements
Proširenje frekvencijskog opsega za eksperimentalno određivanje disperzione relacija talasa savijanja u štapovima primenom korelacione metode
The dispersion relation is the key for studies of wave propagation. The experimental determination of a dispersion relation by measurements of wave properties in different points in space meets the challenge of spatial aliasing, which is further augmented by numerical instability of calculations. This paper presents and discusses a concept aimed to overcome the spatial aliasing problem in measurements of dispersion relation of mechanical waves propagating through beams. The concept is based on the properties of the dispersion relationship and it may be extended to the case of all other waves with monotonous dispersion relationship.Publishe
Super-Resolution TOA Estimation with Diversity Techniques for Indoor Geolocation Applications
Recently, there are great interests in the location-based applications and the location-awareness of mobile wireless systems in indoor areas, which require accurate location estimation in indoor environments. The traditional geolocation systems such as the GPS are not designed for indoor applications, and cannot provide accurate location estimation in indoor environments. Therefore, there is a need for new location finding techniques and systems for indoor geolocation applications. In this thesis, a wide variety of technical aspects and challenging issues involved in the design and performance evaluation of indoor geolocation systems are presented first. Then the TOA estimation techniques are studied in details for use in indoor multipath channels, including the maximum-likelihood technique, the MUSIC super-resolution technique, and diversity techniques as well as various issues involved in the practical implementation. It is shown that due to the complexity of indoor radio propagation channels, dramatically large estimation errors may occur with the traditional techniques, and the super-resolution techniques can significantly improve the performance of the TOA estimation in indoor environments. Also, diversity techniques, especially the frequency-diversity with the CMDCS, can further improve the performance of the super-resolution techniques
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