Acceleration of Range Points Migration-Based Microwave Imaging for Nondestructive Testing

We report on an experimental investigation of the properties of volume holographic recording in photopolymerizable nanoparticle?polymer composites (NPCs) doped with chain transferring multifunctional di- and tri-thiols as chain transfer agents. It is shown that the incorporation of the multifunctional thiols into NPCs more strongly influences on volume holographic recording than that doped with mono-thiol since more chemical reactions involve in the polymer network formation. It is found that, as similar to the case of mono-thiol doping, there exist optimum concentrations of di- and tri-thiols for maximizing the saturated refractive index modulation. It is also seen that recording sensitivity monotonically decreases with an increase in multifunctional thiol concentration due to the partial inhibition of the photopolymerization event by excessive thiols

非侵襲内部UWBレーダのためのRPM法とFDTD法を併用した誘電率分布推定法

本論文はUWB(Ultra-Wideband)レーダを用いて，非破壊検査や非侵襲生体内部計測を可能とする内部画像化技術の研究成果をまとめたものである．従来，道路内部の劣化状況を調査する非破壊検査や乳癌細胞検知等の非侵襲による生体内部の画像化技術として，X線マンモグラフィ，超音波診断等がある．しかし，X線マンモグラフィは放射線を用いるため被験者の被爆の危険性，超音波診断は反射エコー強度のみの情報しか得られないため，癌細胞等の検知が難しいことが問題となっている．低周波領域のマイクロ波UWB信号は，は高い距離分解能と誘電体透過性に優れており，対象の誘電率や導電率の電磁気的特性を定量的に抽出できることから，同信号を用いた内部画像化技術は既存技術の問題を解決する新たな手法として注目されている．同レーダを用いた誘電体内部画像化手法にはRPM(Range Points Migration)法の原理を拡張した高精度内部目標画像化手法が提案されている．同手法はRPM法による誘電体境界推定点と同法線ベクトルから幾何光学近似により誘電体内部の伝搬経路を決定することで，波長限界を超えた精度を保持する．しかし，同手法は画像化精度が誘電率依存性を有するため誘電率推定法と併用する必要がある．一般的な誘電率推定法には領域積分方程式を用いた数値解析による手法がある．しかし，同手法はBorn近似により誘電率と真空のコントラストが大きい場合には，収束が困難になり，計算時間も膨大となる問題もある．上記問題を改善するため，本稿では，RPM法の誘電体境界推定点群とレイトレーシング及びFDTD(Finite Difference Time Domain)法を用いた誘電率分布推定法を提案する．本手法では，均質誘電媒質に対する高精度誘電率推定法を初期値に設定し，誘電率分布を基底関数の線形混合で表現することで次元数を減らし，収束速度を速める．多次元最適化問題に対して効率的に最適解に到達可能な粒子群最適化(PSO:Particle Swarm Optimization)法を導入する．順問題解析には，始めにレイトレーシングを導入し，最適解に近付けた後，FDTD法に切り替えることで，効率的かつ高精度な誘電率推定を目指す．本手法の有効性を数値計算により評価する．電気通信大学201

ＵＷＢ内部画像レーダのための拡張Envelope法を用いた二層誘電体境界推定法

近年，誘電体内部計測技術としてUWB(Ultra wide-band) レーダが注目されている．従来の技術では，コンクリート中に埋設する物体や亀裂等の異常を感知する非破壊検査や，乳癌等の非侵襲生体計測といった誘電体内部計測として，X線や超音波を用いた手法が利用されていた．しかし，X線では，放射線被爆，超音波では接触計測が必要であるという各種の制限があった．そこで，高分解能と高い誘電体内部透過性といった特徴を持つUWBパルスレーダを用いた内部画像化技術への応用が期待される．既に，高精度内部画像化手法として，RPM(Range Points Migration)法の原理を拡張した画像化手法が提案されている．同手法は，誘電体境界推定点及び同法線ベクトルによる幾何光学近似に基づいた伝搬経路決定を用いた手法である．しかし，同手法の再現精度は対象の誘電率に依存する．実際の測定においては，誘電率は不均質かつ未知であるため，高精度の内部画像化には正確に誘電率を同時推定する必要がある．このため，従来の内部画像化手法には誘電率推定法との併用が必須となる．従来の誘電率推定法には，領域積分法手式に基づく手法や壁透過レーダを想定した手法が各種提案されている．しかし，前者は層構造を持つ誘電体に対して精度が劣化し，かつ膨大な計算量を有すること，後者は直方体等の単純な形状に限定される等の問題点を有する．これらの問題を解決するため，任意境界に対応した，高速高精度の誘電率推定法が提案された．同手法は，RPM法による高精度誘電体境界推定及び透過は伝搬距離と幾何光学近似に基づく手法である．しかし，同手法は単一誘電層を想定した手法のため，人体の皮膚や脂肪等の層構造を持つ誘電体に対して誘電率を推定することが出来ないため，内部画像化を行うことが困難である．上記問題点を解決するために，本論文では，二層誘電層媒質を想定した，幾何光学近似と拡張Envelope法を用いる誘電率推定法を提案する．外部境界に対してRPM法及びEnvelope法，内部境界に対しEnvelope法を拡張した手法により各層境界を推定する．各層を透過する幾何光学近似に基づく伝搬遅延量の最適化によって，各誘電層の誘電率を同時に推定することを可能にする．数値計算及び実験による性能評価により評価し，提案法の有効性を示す．電気通信大学201

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design

Behind-wall target detection using micro-doppler effects

Abstract: During the last decade technology for seeing through walls and through dense vegetation has interested many researchers. This technology offers excellent opportunities for military and police applications, though applications are not limited to the military and police; they go beyond those applications to where detecting a target behind an obstacle is needed. To be able to disclose the location and velocity of obscured targets, scientists’ resort to electromagnetic wave propagation. Thus, through-the-wall radar (TWR) is technology used to propagate electromagnetic waves towards a target through a wall. Though TWR is a promising technology, it has been reported that TWR imaging (TWRI) poses a range of ambiguities in target characterisation and detection. These ambiguities are related to the thickness and electric properties of walls. It has been reported that the mechanical and electric properties of the wall defocus the target image rendered by the radar. The defocusing problem is the phenomenon of displacing the target away from its true location when the image is rendered. Thus, the operator of the TWR will have a wrong position, not the real position of the target. Defocusing is not the only problem observed while the signal is travelling through the wall. Target classification, wall modelling and others are areas that need investigation...D.Ing. (Electrical and Electronic Engineering

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Advanced Sensors for Real-Time Monitoring Applications

It is impossible to imagine the modern world without sensors, or without real-time information about almost everything—from local temperature to material composition and health parameters. We sense, measure, and process data and act accordingly all the time. In fact, real-time monitoring and information is key to a successful business, an assistant in life-saving decisions that healthcare professionals make, and a tool in research that could revolutionize the future. To ensure that sensors address the rapidly developing needs of various areas of our lives and activities, scientists, researchers, manufacturers, and end-users have established an efficient dialogue so that the newest technological achievements in all aspects of real-time sensing can be implemented for the benefit of the wider community. This book documents some of the results of such a dialogue and reports on advances in sensors and sensor systems for existing and emerging real-time monitoring applications

Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication

Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future

Radar Detection, Tracking and Identification for UAV Sense and Avoid Applications

Advances in Unmanned Aerial Vehicle (UAV) technology have enabled wider access for the general public leading to more stringent flight regulations, such as the line of sight restriction, for hobbyists and commercial applications. Improving sensor technology for Sense And Avoid (SAA) systems is currently a major research area in the unmanned vehicle community. This thesis overviews efforts made to advance intelligent algorithms used to detect, track, and identify commercial UAV targets by enabling rapid prototyping of novel radar techniques such as micro-Doppler radar target identification or cognitive radar. To enable empirical radar signal processing evaluations, an S-Band and X-Band frequency modulated, software-defined radar testbed is designed, implemented, and evaluated with field measurements. The final evaluations provide proof of functionality, performance measurements, and limitations of this testbed and future software-defined radars. The testbed is comprised of open-source software and hardware meant to accelerate the development of a reliable, repeatable, and scalable SAA system for the wide range of new and existing UAVs