Wall Compensation for Ultra Wideband Applications

Due to their low frequency contents, ultra wideband (UWB) signals have the ability to penetrate walls and obstacles. As the signal propagates through these obstacles, it gets attenuated, slows down, and gets dispersed. This paper demonstrates wall compensation for through-wall imaging, localization and communication receiver design purposes by first characterizing wave propagation through various building materials in the UWB frequency range. Knowledge of the walls obtained from the wall characterization is used to estimate and correct the position accuracy of a target object located behind the walls using three proposed methods namely; constant amplitude and delay (CDL), frequency dependent data (FFD), and data fitting methods (FIT). The obtained results indicated relatively acceptable measure of wall compensation for the three methods. Results from such work provide insight on how to develop algorithms for effective target position estimation in imaging and localization applications. They are also useful for channel modelling and link budget analysis

Sensing task handover for indoor clustered wireless sensor network

This paper presents the proposal of implementing sensing task handover initiation control for wireless sensor network deployed in indoor environment. The structure of the wireless sensor network is based on indoor clustering so that sensor nodes are grouped in different clusters according to room partitions. For such a network, a simple and efficient multi-node handover initiation control method is proposed for the decision of handover initiation by comparing the combined received signal strengths and the number of effective nodes between two neighbouring clusters. Experiments were conducted to test the possibility and evaluate the performance of the proposed method. The results show that sensing task handover is possible to happen at accurate time while crossing boundary between two clusters by applying the proposed method

Investigation of ducts as a “radar pinhole” for detecting objects through a wall

There is a continuing interest in the through-the-wall capabilities of radar. It has been found that walls behave as a low-pass medium, and therefore through-the-wall radar has been restricted to frequencies in the low GHz range. Unfortunately at these lower frequencies the resolution of the radar system is sacrificed. This thesis investigates the possibility of using a duct as a means of detecting objects through a wall. Ducts have been extensively studied in the past; however there has been limited research of ducts with two open ends. In this thesis the difference between an open-ended duct and a duct with two open ends is investigated through measurement and simulation. For simulation an approximate method is used that treats the duct as a waveguide. It is found that a significant amount of power is transmitted through a duct with two open ends. It is then shown that an object can be detected through a wall by using a duct that has been inserted into the wall. Then the two-way insertion loss of a duct with two open ends is determined through measurement and simulation. It is shown that a duct behaves as a high-pass medium and can be used as a propagation channel through a wall. The insertion loss due to the duct and the insertion loss through a concrete wall are comparedElectrical and Computer Engineerin

Radio wave imaging using Ultra-Wide Band Spectrum Antennas for Near-Field Applications. Design, Development, and Measurements of Ultra-Wideband Antenna for Microwave Near-Field Imaging Applications by applying Optimisation Algorithms

The emergence of Ultra-wideband (UWB) technology application has yielded tremendous and vital impacts in the field of microwave wireless communications. These applications include military radar imaging, security screening, and tumour detection, especially for early detection of breast cancer. These indicators have stimulated and inspired many researchers to make the best use of this promising technology. UWB technology challenges such as antenna design, the problem of imaging reconstruction techniques, challenges of severe signal attenuation and dispersion in high loss material. Others are lengthy computational time demand and large computer memory requirements are prevalent constraints that need to be tackled especially in a large scale and complex computational electromagnetic analysis. In this regard, it is necessary to find out recently developed optimisation techniques that can provide solutions to these problems. In this thesis, designing, optimisation, development, measurement, and analysis of UWB antennas for near-field microwave imaging applications are considered. This technology emulates the same concept of surface penetrating radar operating in various forms of the UWB spectrum. The initial design of UWB monopole antennas, including T-slots, rectangular slots, and hexagonal slots on a circular radiating patch, was explicitly implemented for medical imaging applications to cover the UWB frequency ranging from 3.1 GHz to 10.6 GHz. Based on this concept, a new bow-tie and Vivaldi UWB antennas were designed for a through-the-wall imaging application. The new antennas were designed to cover a spectrum on a lower frequency ranging from 1 GHz - 4 GHz to ease the high wall losses that will be encountered when using a higher frequency range and to guarantee deeper penetration of the electromagnetic wave. Finally, both simulated and calculated results of the designed, optimised antennas indicate excellent agreement with improved performance in terms of return loss, gain, radiation pattern, and fidelity over the entire UWB frequency. These breakthroughs provided reduced computational time and computer memory requirement for useful, efficient, reliable, and compact sensors for imaging applications, including security and breast cancer detection, thereby saving more lives.Tertiary Education Trust Fund (TET Fund) Supported by the Nigerian Defence Academy (NDA

The analysis of UWB Radar System for Microwave Imaging Application.

PhDMany research groups have conducted the investigation into UWB imaging radar system for various applications over the last decade. Due to the demanding security requirements, it is desirable to devise a convenient and reliable imaging system for concealed weapon detection. Therefore, this thesis presents my research into a low cost and compact UWB imaging radar system for security purpose. This research consists of two major parts: building the UWB imaging system and testing the imaging algorithms. Firstly, the time-domain UWB imaging radar system is developed based on a modulating scheme, achieving a receiver sensitivity of -78dBm and a receiver dynamic range of 69dB. A rotary UWB antenna linear array, comprising one central transmitting antenna and four side-by-side receiving antennas, is adopted to form 2D array in order to achieve a better cross-range resolution of the target. In operation, the rotation of the antenna array is automatically controlled through the computerised modules in LabVIEW. Two imaging algorithms have been extensively tested in the developed UWB radar system for a number of scenarios. In simulation, the “Delay and Sum (DAS)” method has been shown to be effective at mapping out the metallic targets in free space, but prone to errors in more complicated environments. However, the “Time Reversal (TR)” method can produce better images in more complex scenarios, where traditionally unfavorable multi-path interference becomes a valuable asset. These observations were verified in experiment in different testing environments, such as penetration through wooden boards, clutters and a stuffed sport bag. The detectable size of a single target is 8×8×1 cm3 with 30cm distance in a stuffed bag, while DAS can achieve the estimation of 7cm cross-range resolution and 15cm down-range resolution for two targets with sizes of 8×8×1 cm3 and 10×10×1 cm3, which fits within the theoretical prediction. In contrast, TR can distinguish them with a superior 4cm cross range resolution

ReSCon '12, Research Student Conference: Book of Abstracts

The fifth SED Research Student Conference (ReSCon2012) was hosted over three days, 18-20 June 2012, in the Hamilton Centre at Brunel University. The conference consisted of 130 oral and 70 poster presentations, based on the high quality and diverse research being conducted within the School of Engineering and Design by postgraduate research students. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School