Ultra-wideband Impulse-based Radar Signals for Through-the-wall Imaging

Ultra-wideband (UWB) is the promising technology for localization of the objects behind the walls. Recent terrorist activities and law-enforcement situations underscore the need for effective through-wall detection. The approval of UWB technology made by federal communications commission (FCC) in 2002 makes the researchers to have a look on this technology. UWB radar signals has extremely large frequency spectrum and since low frequencies has more penetration capabilities through dielectric materials it is best suitable for through-the-wall radar imaging (TWRI). Signal processing in TWRI has a greater impact in getting the information of the scanned area. This paper uses impulse signals in TWRI, examines the factors impacting in TWRI and obtains the two dimensional information of the scanned scene. Electromagnetic simulation software is used to generate the room like structure, and to obtain the raw radar data.Defence Science Journal, 2012, 62(1), pp.187-192, DOI:http://dx.doi.org/10.14429/dsj.62.84

Non-uniform transmission line ultra-wideband wilkinson power divider

We propose a technique with clear guidelines to design a compact planar Wilkinson power divider (WPD) for ultra-wideband (UWB) applications. The design procedure is accomplished by replacing the uniform transmission lines in each arm of the conventional power divider with varying-impedance profiles governed by a truncated Fourier series. Such non-uniform transmission lines (NTLs) are obtained through the even mode analysis, whereas three isolation resistors are optimized in the odd mode circuit to achieve proper isolation and output ports matching over the frequency range of interest. For verification purposes, an in-phase equal split WPD is designed, simulated, and measured. Simulation and measurement results show that the input and output ports matching as well as the isolation are below -10 dB, whereas the transmission parameters are in the range of (-3:2 dB, -4:2 dB) across the 3.1 GHz-10.6 GHz band

FMCW Signals for Radar Imaging and Channel Sounding

A linear / stepped frequency modulated continuous wave (FMCW) signal has for a long time been used in radar and channel sounding. A novel FMCW waveform known as “Gated FMCW” signal is proposed in this thesis for the suppression of strong undesired signals in microwave radar applications, such as: through-the-wall, ground penetrating, and medical imaging radar. In these applications the crosstalk signal between antennas and the reflections form the early interface (wall, ground surface, or skin respectively) are much stronger in magnitude compared to the backscattered signal from the target. Consequently, if not suppressed they overshadow the target’s return making detection a difficult task. Moreover, these strong unwanted reflections limit the radar’s dynamic range and might saturate or block the receiver causing the reflection from actual targets (especially targets with low radar cross section) to appear as noise. The effectiveness of the proposed waveform as a suppression technique was investigated in various radar scenarios, through numerical simulations and experiments. Comparisons of the radar images obtained for the radar system operating with the standard linear FMCW signal and with the proposed Gated FMCW waveform are also made. In addition to the radar work the application of FMCW signals to radio propagation measurements and channel characterisation in the 60 GHz and 2-6 GHz frequency bands in indoor and outdoor environments is described. The data are used to predict the bit error rate performance of the in-house built measurement based channel simulator and the results are compared with the theoretical multipath channel simulator available in Matlab

Ultra-Wideband Radar-Based Activity Recognition Using Deep Learning

With recent advances in the field of sensing, it has become possible to build better assistive technologies. This enables the strengthening of eldercare with regard to daily routines and the provision of personalised care to users. For instance, it is possible to detect a person’s behaviour based on wearable or ambient sensors; however, it is difficult for users to wear devices 24/7, as they would have to be recharged regularly because of their energy consumption. Similarly, although cameras have been widely used as ambient sensors, they carry the risk of breaching users’ privacy. This paper presents a novel sensing approach based on deep learning for human activity recognition using a non-wearable ultra-wideband (UWB) radar sensor. UWB sensors protect privacy better than RGB cameras because they do not collect visual data. In this study, UWB sensors were mounted on a mobile robot to monitor and observe subjects from a specific distance (namely, 1.5–2.0 m). Initially, data were collected in a lab environment for five different human activities. Subsequently, the data were used to train a model using the state-of-the-art deep learning approach, namely long short-term memory (LSTM). Conventional training approaches were also tested to validate the superiority of LSTM. As a UWB sensor collects many data points in a single frame, enhanced discriminant analysis was used to reduce the dimensions of the features through application of principal component analysis to the raw dataset, followed by linear discriminant analysis. The enhanced discriminant features were fed into the LSTMs. Finally, the trained model was tested using new inputs. The proposed LSTM-based activity recognition approach performed better than conventional approaches, with an accuracy of 99.6%. We applied 5-fold cross-validation to test our approach. We also validated our approach on publically available dataset. The proposed method can be applied in many prominent fields, including human–robot interaction for various practical applications, such as mobile robots for eldercare.publishedVersio

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

Antenna Bandwidth and Radiation Control by Topology and use of Non-Conductive Materials.

The demand for ultra-wideband (UWB) antennas have been on the rise in the last decade. There are many different systems and devices such as ground penetrating radars (GPRs) and wireless communications where such antennas find very unique applications. Many topologies and configurations have been studied and reported in designing UWB antennas. These topologies are corresponding to radiation pattern, polarization, and band of operation. In addition, in low frequencies, the size of the antenna becomes a major factor that must be taken into consideration. A portion of this thesis focuses on the design of novel UWB antennas. A new approach in design of a cavity-backed coupled sectorial loop antenna (CB-CSLA) with directional radiation pattern is presented. This antenna is backed by a short cylindrical cavity with a special modal suppressing septum to accomplish a unidirectional radiation pattern while maintaining a very wide bandwidth. Another approach, more applicable to ground penetrating radars, based on dielectric loaded multi-resonant slot antenna is also presented. Unidirectional radiation is achieved by a symmetrically loading the slot radiators. Since the slot length is reduced, radiation is preferentially aimed towards the dielectric superstrate. By gradually changing the index of refraction, the radiation from the dielectric back to the surrounding medium is facilitated. A prototype with dimension of 0.28λ by 0.2λ by 0.07λ is fabricated and shown to have a bandwidth of 35.5% and a front to back ratio of 12dB. For the new 700MHz band considered for wireless communication applications, a novel planar wideband slot antenna is designed. The slot antenna size is reduced from the traditional λ/2 slot to λ/4. Then parasitic coupling, using a number of λ/4 slot elements appropriately positioned around the driving element, and direct feeding are used to increase the bandwidth. For communication applications, a novel miniaturized impedance matched antenna with an omnidirectional horizontally polarized radiation pattern is presented. The antenna structure resembles a circular loop formed by a circular array of shunt miniaturized n-fold resonant dipole antennas which is referred to as a miniature composite wire-loop antenna (MCWLA). This antenna has a diameter of λ/9 and a height of less than λ/500.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120697/1/hbukhari_1.pd

Novel Approaches for Nondestructive Testing and Evaluation

Nondestructive testing and evaluation (NDT&E) is one of the most important techniques for determining the quality and safety of materials, components, devices, and structures. NDT&E technologies include ultrasonic testing (UT), magnetic particle testing (MT), magnetic flux leakage testing (MFLT), eddy current testing (ECT), radiation testing (RT), penetrant testing (PT), and visual testing (VT), and these are widely used throughout the modern industry. However, some NDT processes, such as those for cleaning specimens and removing paint, cause environmental pollution and must only be considered in limited environments (time, space, and sensor selection). Thus, NDT&E is classified as a typical 3D (dirty, dangerous, and difficult) job. In addition, NDT operators judge the presence of damage based on experience and subjective judgment, so in some cases, a flaw may not be detected during the test. Therefore, to obtain clearer test results, a means for the operator to determine flaws more easily should be provided. In addition, the test results should be organized systemically in order to identify the cause of the abnormality in the test specimen and to identify the progress of the damage quantitatively

Revisión del estado del arte deIR-Ultra-Wideband y simulación de la respuesta impulsiva del canal IEEE802.15.4a

This article reviews the state of the art of technology based on Ultra Wideband (UWB) channels, focusing on their regulation, standardization, basic applications, IEEE 802.15.4a channel model and simulation of the impulse response of This type of channel. It is also intended to introduce the reader in the technologies based on IR – UWB channels and in the parameters for modeling and simulation of the IEEE 802.15.4a UWB channel.Este artículo realiza una revisión del estado del arte de la tecnología basada en canales de Banda Ultra Ancha (UWB, Ultra–Wideband) enfocándose en su regulación, estandarización, aplicaciones básicas, modelo de canal IEEE 802.15.4a y simulación de la respuesta impulsiva de este tipo de canal. También se pretende introducir al lector en las tecnologías basadas en canales IR–UWB y en los parámetros para el modelamiento y simulación del canal UWB IEEE 802.15.4a

A Through-the-Wall Radar Imaging Method Based on a Realistic Model

An image focusing method based on a realistic model for a wall is proposed for through-the-wall radar imaging using a multiple-input multiple-output array. A technique to estimate the wall parameters (i.e., position, thickness, and permittivity) from the radar returns is developed and tested. The estimated wall properties are used in the developed penetrating image formation to form images. The penetrating image formation developed is computationally efficient to realize real-time imaging, which does not depend on refraction points. The through-the-wall imaging method is validated on simulated and real data. It is shown that the proposed method provides high localization accuracy of targets concealed behind walls