Rudolf Zetik

Liquid and moisture sensing by ultra-wideband pseudo-noise sequence signals

The use of ultra-wideband signals for moisture sensing by electromagnetic wave interaction provides more information on the material under test compared to single tone or narrowband approaches, regarding spatial and frequency dependent phenomena. Current activities to regulate the emission of electromagnetic waves in the spectral band up to 10 GHz for sensor applications open new perspectives for microwave moisture sensing. Therefore, improved and cost effective ultra-wideband measurement principles will become more and more interesting. The use of short pulses or swept sine waves are classic approaches to cover a large spectral band. However, this paper deals with some variants of an alternative method, which applies pseudo-random codes, namely M-sequences, to stimulate the test objects. The method permits monolithic integration of the RF-electronics in SiGe technology. The signal generation and data capturing are referred to a common stable single tone clock and they are controlled by steep trigger signals. This provides for very stable operation, which allows for measurements in both time and frequency domain. Two versions of an M-sequence approach will be considered and their functioning will be demonstrated by means of simple measurement examples.

Detection and localization of persons behind obstacles using M-sequence through-the-wall radar

We describe the architecture and design of a through-the-wall radar. The radar is applied for the detection and localization of people hidden behind obstacles. It implements a new adaptive processing technique for people detection, which is introduced in this article. This processing technique is based on exponential averaging with adopted weighting coefficients. Through-the-wall detection and localization of a moving person is demonstrated by a measurement example. The localization relies on the time-of-flight approach.

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.

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.

Real-Time MIMO Channel Sounder for Emulation of Distributed Ultrawideband Systems

This paper introduces an ultrawideband (UWB) channel sounding system. Its novel architecture allows real-time measurements of multiple time-variant radio propagation channels in different ultrawide frequency bands. Its architecture allows emulation of multiuser systems, sensor networks, localization systems, and distributed MIMO radar systems. The sounder uses a maximum length binary sequence (MLBS) excitation signal and correlation processing in the receiver. Its synchronous multichannel operation is supported by excellent timing stability and low power consumption of miniature size modules based upon custom integrated SiGe circuits. The paper describes the architecture, design, calibration, basic parameters, and application examples of the sounding system.

Evaluation of requirements for UWB localization systems in home-entertainment applications

This paper discusses basic requirements for passive ultra-wideband (UWB) localization systems that aim at home-entertainment applications such as smart audio systems, which can adapt the sound according to the user location, providing an optimum listening experience to the user. We have analyzed over hundred thousand channel impulse responses measured by a real-time UWB channel sounder in different scenarios. Our analyses show that passive localization systems must possess a large real-time dynamic range in order to be capable of detecting a listener. We assume that the listener does not carry any tag and is detected and localized just by electro-magnetic (EM) waves reflected from his body. Such passive localization is demonstrated by a measurement example.

Short-range UWB radar: Surveillance robot equipment of the future

Autonomous robots are intelligent machines capable of performing tasks by themselves, without explicit human control. They can find quit a number of unique applications. Here, their utilisation for surveillance, monitoring and reconnaissance in hostile and dangerous to life environment intent on human being detection and/or static object imaging is up-to-date, promising and challenging as well. The fruitfulness of this application of robot systems is determined by many factors. The effective and reliable sensor system for human being detection and localization and static object imaging under wide variety of scenarios can be rated among them. In the last decade, it has been shown that ultra-wideband (UWB) radars (sensors) can be used with advantage as day and night, and under all-weather conditions sensors for person localization and static object imaging. Taking into account this fact, this paper will be intent on the analyses of UWB sensor applicability as the part of the smart sensor systems of robots to be used at emergency situation solutions. Summarizing the results of theoretical analyses and experiments with UWB sensors presented in the paper, it will be concluded that the short-range UWB radars have the great potential to be used as a standard equipment of surveillance and reconnaissance robot systems of future.

Through-Wall Imaging by Means of UWB Radar

The aim of this article is to demonstrate ability of multi-channel UWB radar to detect and localize people behind walls. The article describes the architecture of the UWB radar used for the real-time measurements and demonstrates its application for the through-wall imaging by measurement experiments.

Imaging in UWB Sensor Networks

Sensor networks consist of a number of spatially distributed nodes. These nodes perform measurements and collect information about their surrounding. They transfer data to neighboring nodes or to a data fusion center. Often measurements are performed in cooperation of several nodes. If the network consists of Ultra-Wideband (UWB) radar sensors, the network infrastructure can be used for a rough imaging of the surrounding. In this way bigger objects (walls, pillars, machines, furniture) can be detected and their position and shape can be estimated. These are valuable information for the autonomous orientation of robots and for the inspection of buildings, especially in case of dangerous environments (fire, smoke, dust, dangerous gases). Applications of UWB sensor networks are summarized in Thoma (2007). In this article basic aspects of imaging in UWB sensor networks are discussed. We start with a brief description of two types of UWB radar devices: impulse radar and Noise/M-sequence radar. Network imaging is based on principles of Synthetic Aperture Radar (SAR). Starting from SAR some special aspects of imaging in networks are explained in section 3. Sections 4 and 5 form the main part of the article. Here two different imaging approaches are described inmore detail. The firstmethod ismultistatic imaging, i.e. the measurements are performed in cooperation of several sensor nodes at fixed places and onemobile node. The second approach is imaging by an autonomous mobile sensor, equipped with one Tx and two Rx units. This sensor uses a network of fixed nodes for its own orientation. Part of the described methods have been practically realized in a laboratory environment. Hence, practical examples support the presentation. Conclusions and references complete the article.