Methods and Algorithms of Signal Processing for Rescuer’s Radar
Abstract
The problem of prompt detection of people affected during various kinds of catastrophes in ruined buildings, accidents in mines, quarries, accidents caused by snow avalanches, mudflows and landslides has discussed. The problems of creating portable remote sensing devices for people behind optically opaque barriers has detalied illuminated in theoretical and practical aspects. Main attantion paied to class of short-range doppler radar with continuous pseudo-noise phase-code modulation of the probing signal. Presented and discussed the different methods how to isolate the information signal against the background of interference caused by reflections of the sounding signal from local objects, obstacles on the propagation path, and subsequent decision making about the presence or absence of the target in the interest area. The book summarizes the author's experience in developing the theory and technique of digital processing of information signals of radar systems for the detection of living people hidden by optically opaque obstacles. A mathematical apparatus and results of simulation of signal processing algorithms are described. The results of experiments are presented.
... Stochastic modeling methods are widely used in the study of complex radio systems, the assessment of their functioning and effectiveness. The radars for rescuers [1][2][3] are the kind of systems which detect live humans behind optically opaque barriers. The processes of human breathing and heartbeat cause phase fluctuations in the radar's reflected signals [4], according to Doppler effect. ...
Subject and Purpose. The subject of the research is a system of coherent digital processing of radar signals such that includes a number of spatially spaced receiving points and is designed to detect moving objects hidden behind optically opaque obstacles. The aim of the work is to synthesize an optimal, in the sense of a minimum Bayesian risk average, signal structure in the processing system. The system performance is evaluated and recommendations as to the choice of signal preprocessing system parameters are developed.
Methods and Methodology of the work are based on the analysis of probabilistic characteristics of the useful and interference signals and seek to synthesize an algorithm for processing observed signal implementations according to a single quality criterion of a minimum average loss from incorrect decisions. The task of detection and estimation of moving objects in terms of their number and angular coordinates is formulated as a statistical problem. The angular resolution algorithm for point targets is built on the principle of statistical hypothesis testing. The a priori information about the characteristics of useful and interference signals during the target movement and, also, about the target probabilistic properties allows a procedure of signal processing to be built through the spatial synthesis of the observation system aperture, offering a resolution exceeding the energy limiting resolution.
Results. Analytical relations have been obtained for the joint procedure of signal detection and arrival angle measurement. The estimated angular positions of the targets are used in the aperture synthesis algorithm. It has been shown that the real-time aperture synthesis is possible in the case of relatively high signal-to-noise ratios and linear and unidirectional movement of targets.
Conclusions. A two-channel algorithm for monitoring moving targets has been developed. Based on the a priori information about the nature of target movement and on the estimates of angular positions and numbers of the targets, a passive synthesis procedure for the observation system aperture has been constructed. Recommendations have been developed for algorithm implementations in real time.
This paper describes the results from experimental studies on the coherent Doppler radar signals echoed from a human being. Spectral and temporal realizations of informational processes and their statistical characteristics are presented. It is shown that in the microwave-band sounding signal the process generated by the echo-signal phase modulation caused by human breathing has the properties of periodically correlated random process. The statistical characteristics of this process are calculated on an equidistant grating, the period of which is equal to that of process correlation. A stochastic criterion is proposed to estimate the correlation period. The ergodicity property of the process on an equidistant grating has been theoretically proved and experimentally confirmed.
The results of experimental researches of losses of electromagnetic energy in the decimeter bandwidth after the waves propagation through the elements of building structures are examined from the point of view of the basic requirements set to the radar characteristics in terms of detection of people behind the optically non-transparent obstacles. The samples of building structures and construction materials representing the most probable options of obstacles during the man-caused disasters are selected as objects of research. Dependences of radio waves attenuation upon the frequency and polarization are investigated. Possibility of reception of the reflected electromagnetic signals in the decimeter bandwidth from moving living beings behind the concrete and armored concrete ceilings and walls is considered. The requirements set to the conditions of experiments and methodology of their performing are discussed. Authenticity of results is substantiated.
The new approach to the solution of a problem of the microwave image reconstruction of the subsurface objects is offered in the present work. Necessity of the complex amplitude measurement of electromagnetic field is excluded in a point on a direct line above surface in the considered further method. Calculation of the direct Fourier transformation of the measured field is also excluded. In the experiment, data on complex electromagnetic field (data of the transmission coefficients) at 32 frequencies in the operating band with a constant frequency step was used. Experiments were carried out at frequencies from 3 to 4 GHz. The images of the irradiating dipoles, considered as models of the scattering centers of an object, were reconstructed from the measured data.
The main problems arising to design continuous-signal rescue-radars are discussed. The block-diagram of a rescue-radar, signal processing and specific radars design are presented. In signal processing it is propoused to employ the multiplicative unstationarity processes model with shared variables. When synthesizing the algorithms for detecting recognizing and identifying objects it is necessary to make use of periodically correlated processes model. The experimental datas to detecting human heartbeat and breathing are presented.
In this paper we describe a method of minefield reconnaissance with the use of the multi-frequency ground-penetrating radar (GPR) combined with a metal detector. This method allows the mine images in the soil to be obtained in the band of the mine detector sensors. An experimental installation with remote control and scanning sensors has been designed and built. A mine detector of this kind can be used in peacekeeping and humanitarian operations.
We describe a new method of minefield reconnaissance with use of
the broad size detector. The method allows terrain radio images to be
obtained in the band of the mine detector sensors. The experimental
installation was created with a set of radio ground probing sensors. To
treat the radio images and to reduce the number of false alarms, spatial
algorithms were proposed. A mine detector of this kind can be used in
peacekeeping and humanitarian operations
During the course of this contract, there have been several major task
areas: the development of homomorphic signal processing techniques and
their application to the development of a homomorphic vocoder and other
signal processing applications; the development and implementation of
techniques for enhancement and bandwidth compression of degraded speech;
the development and evaluation of techniques for processing of
multidimensional signals and the application of these techniques to
image processing, and the processing of other multidimensional data
sets; and the development of techniques and the implementation and
evaluation of systems for speed transformations of speech.
In the present paper new results of modeling and experimental investigation on millimeter wave subsurface tomography are submitted. Tomographic algorithm is employed for imaging of subsurface objects in the case when conductivity of probed medium is not equal to zero. The possibilities and restrictions of this algorithm for image processing are shown both as a result of modeling and as a result of experiments. A new tomography setup allowing obtaining images of different inhomogeneities in dielectric media is considered.
An optimal algorithm (which is optimal in terms of a likelihood maximum) for calculating nonparametric spectral estimates of a target-reflected information signal is proposed. The algorithm in question is based on the principle of data acquisition as the data are coming during signal processing.
The possibility of UWB radar use in medicine for remote measuring of patient's heart activity and respiration is considered. The measuring method is described and practical results of tests are cited. The probability of radar implementation in the other fields is shown.
Targets selection method based on the attribute of Doppler painting of the echo-signal phase structure is considered in the paper. The concept of orthogonal decomposition of the signal and precise representation of the function upon a discrete set of points using the full system of basis functions forms up the base of the method. The algorithm for calculation of the spectral estimates upon a limited in time selection of the signal is developed. The algorithm allows calculate spectral estimates of quasi-periodic processes with typical frequencies from 0.1 to 10 Hz. Stability and noise immunity of the algorithm are investigated. It is demonstrated that unlike the known methods of spectral super-resolution the suggested method does not provide for false spectral responses at decreasing of the signal-to-noise ratio.
Surface-penetrating radar is a nondestructive testing technique
which uses electromagnetic waves to investigate the composition of
nonconducting materials either when searching for buried objects or when
measuring their internal structure. A typical surface-penetrating radar
transmits a short pulse of electromagnetic energy of 1 ns (10<sup>-9
</sup> s) time duration from a transmit antenna into the material.
Energy reflected from discontinuities in impedance is received by means
of a receive antenna and is then suitably processed and displayed by a
radar receiver and display unit. If the transmit and receive antennas
are moved at a constant velocity along a linear path, a cross-sectional
image of the material can be generated. Alternatively, if the antennas
are scanned in a regular grid pattern, a three-dimensional image of the
target can be derived. This paper provides a review of the principles of
the technique, discusses the technical requirements for the individual
subsystems comprising a surface-penetrating radar and provides examples
of typical applications for the method. Continued technical improvements
in system performance enable clearer radar images of the internal
structure of materials to be obtained, thus advancing the application of
the technique
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