Dusan Kocur

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.

TOA estimation and data association for through-wall tracking of moving targets

Through-wall tracking of moving targets is of great interest for rescue, surveillance, and security operations. For its realization, the handheld ultrawideband radars with small antenna array provide a practical solution. The radar signal processing, which is hidden behind the estimation of the final target tracks, represents a complex process with several processing phases. In this paper, all phases for through wall tracking are outlined whereas the attention is devoted to the estimation of the correct input data for the localization phase. This is done by applying a new approach that combines the time of arrival (TOA) estimation and the data-association into a single step. The properties of the proposed algorithm are illustrated by processing of real radar signals. Here, the obtained results confirm that the proposed algorithm has provided good, stable, and robust TOA estimation including deghosting task solution.

Efficient and Fast Method of Wall Parameter Estimation by Using UWB Radar System

Precise SAR imaging of objects or detection of moving a person behind a wall with UWB radar or nondestructive testing of walls in civil engineering requires the knowledge of wall parameters like thickness and permittivity. Their use in the data processing produces more precise and realistic results. The measurement of the wall parameters is challenge in a real environment especially when there is access only from one side of the wall. In this paper, an effective and fast algorithm for wall parameters estimation that can be used in practice is presented. For that purpose the magnitudes and the time positions of reflections from inner and outer interfaces of the wall are extracted from the data. A new scanning method reduces drastically the clutter caused by objects in the measurement environment such as reflections from other walls, the ceiling, the floor and antenna crosstalk. The algorithm was tested on 13 different types of walls with different permittivity and thickness. A handheld M-sequence UWB radar with horn and circular antennas was used for data gathering. The proposed method is very robust and the error of the thickness estimation was less than 10% for most of walls. The whole measurement can be handled by one person. The wall parameter estimation runs in real time and is fully automated.

Through-the-wall localization of a moving target by two independent ultra wideband (UWB) radar systems.

In the case of through-the-wall localization of moving targets by ultra wideband (UWB) radars, there are applications in which handheld sensors equipped only with one transmitting and two receiving antennas are applied. Sometimes, the radar using such a small antenna array is not able to localize the target with the required accuracy. With a view to improve through-the-wall target localization, cooperative positioning based on a fusion of data retrieved from two independent radar systems can be used. In this paper, the novel method of the cooperative localization referred to as joining intersections of the ellipses is introduced. This method is based on a geometrical interpretation of target localization where the target position is estimated using a properly created cluster of the ellipse intersections representing potential positions of the target. The performance of the proposed method is compared with the direct calculation method and two alternative methods of cooperative localization using data obtained by measurements with the M-sequence UWB radars. The direct calculation method is applied for the target localization by particular radar systems. As alternative methods of cooperative localization, the arithmetic average of the target coordinates estimated by two single independent UWB radars and the Taylor series method is considered.

Object localization using round trip propagation time measurements

The object localization belongs to the basic tasks solved within wireless sensor networks (WSN). It can be shown, that for WSN based on UWB radar systems, localization methods using round trip propagation times can be used with advantages [1]. In this paper we introduce three localization methods of that kind, i.e., a direct calculation, a conventional and weighted least-squares methods and a Taylor series method. It is expected, that these methods can be applied especially for UWB WSN. The properties of the proposed methods will be illustrated by using computer simulations. It will be shown, that Taylor series method can provide the best estimate of object location.

Through Wall Tracking of Moving Targets by M-Sequence UWB Radar

In this paper different CFAR detectors for detection of multiple targets for UWB radar system will be described. In this paper, the cell averaging CFAR (CA-CFAR) cell averaging with greatest of (CAGO-CFAR) and ordered statistics CFAR (OS-CFAR) will be represented. The detectors outputs will be illustrated and compared. The properties of all detectors will be illustrated by real radar signal processing obtained by the measurement with the 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.