Jana Rovnakova

Efficient method of TOA estimation for through wall imaging by UWB radar

Precise Time Of Arrival (TOA) estimation is a basic step of standard migration methods for object imaging from SAR measurements. In this paper, an effective computation method of the TOA for through wall model of object recognition is presented. The conventional method that uses constant velocity model produces errors in object shape and position estimations. Computation of the TOA (corresponding to true flight distance) for three layer model requires the complex minimization algorithm. Proposed method transforms three layer (air-wall-air) model to equivalent two layer (air-wall) model with lower computation complexity. It uses iterative solution of well defined minimization problem. Moreover, conveniently selected initial conditions of iteration process can further decrease computational complexity of the method. The proposed method provides more precise TOA estimation than conventional one and is less complex than three layer methods. Therefore, it is suitable for implementation on realtime hardware. The method performance is demonstrated by processing of real 2-dimensional SAR data acquired by through wall M-sequence UWB radar system.

Signal processing for through wall moving target tracking by M-sequence UWB radar

In this paper, through wall moving target tracking by UWB radar is described as a complex process with all required phases of radar signal processing. For particular phases of that process, i.e. for raw radar data preprocessing, background subtraction, detection, trace estimation, localization and tracking itself, the phase significance and its corresponding representative methods are outlined. The complete process is illustrated by the results of processing of real data acquired by M-sequence UWB radar.

Weak signal enhancement in radar signal processing

In through wall tracking of multiple targets it is able to detect many times only a target moving closest to the radar antenna system. It results from the fact that the reflections from targets located further from the radar antennas are very week in comparison to that target. The methods for weak signal enhancement can solve the outlined problem. In the paper, three such potential methods are described and tested on real radar signals. The achieved results confirm their ability to enhance the weak signal components with low computational complexity.

Target localization by a multistatic UWB radar

Moving target localization and tracking are of great interest for rescue, surveillance and security operations. The radar signal processing procedure providing the target position estimation consists of such phases of signal processing as raw radar data pre-processing, background subtraction, detection, time of arrival estimation, localization and tracking. In this paper, we will focus on the localization phase where we assume that for the target localization UWB radar equipped by one transmitting and N receiving antennas is used. Following this intention, the accuracy of the target localization provided by the least-squares method, the spherical-interpolation method and the Taylor series method applied within localization phase will be compared based on processing of radar signals obtained from real target tracking by UWB radar. The acquired results confirm that the Taylor series method can provide the best accuracy of the target positioning.

An Analysis of 2D Target Positioning Accuracy for M-sequence UWB Radar System under Ideal Conditions

This paper describes analysis of target positioning accuracy for ultra wideband (UWB) maximum length binary sequence (M-sequence) radar system under ideal conditions in two dimensional space. In this case, it is shown that the target position estimation error is cased by quantization of time of arrival (TOA) measured by the radar system. The appropriate statistical quantities are suggested for describing these errors. The properties of M-sequence UWB radar systems performing under ideal conditions are illustrated by a set of simulations. The results obtained in this paper can be applied as a base for the design of positioning system based on M-sequence UWB radar.

Imaging method: A strong tool for moving target tracking by a multistatic UWB radar system

In this paper, imaging method for moving target tracking by a multistatic ultra-wideband radar system is described. The task of moving target tracking consists in estimation of a target trajectory based on processing of raw radar data obtained from all receiving channels of a radar system. Then, the imaging method applied for target tracking consists of such signal processing phases as raw radar data pre-processing, background subtraction, fusion of the data obtained by receiving antennas of a radar, detection, localization and tracking itself. The performance of the imaging method described in this paper is demonstrated by signal processing obtained by M-sequence UWB radar for a scenario represented by through wall tracking of a single moving target. The obtained results confirm the excellent performance of the discussed method.

Data fusion from UWB radar network: Preliminary experimental results

In this paper, we present the data fusion procedure for ultra wideband (UWB) radar-based tracking of moving persons. It extends a previously proposed complex radar signal processing procedure for multiple target scenarios designed for single through wall UWB radar with small antenna array. The performance of introduced approach is illustrated and validated by the scenario in which two moving persons are detected and tracked by a UWB radar network consisting of two independent radar systems. These preliminary experimental results confirm improvement of target observability whereby the low complexity of the original procedure is preserved.

Moving person tracking by UWB radar system in complex environment

Ultra-wideband radar system allows detect, localize and track moving persons in critical situations and environments. Therefore, the issue of the short-range ultra-wideband radars dedicated to the support of the emergency event solving is really up-to-date. The publications devoted to the mention problem in last decade have dealt with the basic methods of ultra-wideband radar signal processing intent mostly on detection, localization and tracking of moving persons under simple scenarios. In this paper, we will deal with detection, localization and tracking of persons moving through an area where strong and large reflectors of electromagnetic waves are situated. We will show that this complex environment leads to so-called defective localization of target when the number of the targets and the target positions are wrongly estimated. In this paper, we will explain the origin of this effect and propose a new extended method of background subtraction capable to suppress markedly the impact of the mentioned reflectors on reliability and accuracy of a standard procedure of radar signal processing applied for detection, localization, and tracking of moving persons.

Detection of multiple targets with enhancement of weak UWB radar signals for the purposes of through wall surveillance

The radar system utilized for through wall detection and tracking of multiple targets often cannot detect all of them. It results from the fact that the targets which are moving close to the radar antenna system absorb the large amount of energy and the electromagnetic waves reflected from the other targets have small magnitude. This problem can be redeemed by use of the weak signal enhancement methods in combination with proper target detectors. In this paper, six methods which three new are described and tested with the combination of different CFAR detectors. The achieved results confirm the ability of weak signal enhancement methods to improve the result of radar detection.

Mutual shadowing effect of people tracked by the short-range UWB radar

Ultra wideband (UWB) radars belong to the most suitable technologies for short-range detection and tracking of multiple moving persons in critical situations and environments. The results of applications of a single UWB radar for such scenarios have shown that the target located nearby the radar antennas is very often visible only. The other targets can be also detected but with less reliability than that of the target located the most closely to the radar antennas. This is the crucial problem of UWB radar applications for short-range detection and tracking of multiple moving persons. In this paper, we will outline the origin of this effect as the impact of the mutual shadowing of targets within multiple person tracking scenario. This explanation will be verified by the experimental analyses.