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

ANALYSIS AND DESIGN OF PLANAR ACTIVE AND PASSIVE QUASI-OPTICAL COMPONENTS USING NEW FDTD TECHNIQUES

PhDNew Quasi-optical sensor technology, based on the millimetre and submillimetre band of the electromagnetic spectrum, is actually being implemented for many commercial and scientific applications such as remote sensing, astronomy, collision avoidance radar, etc. These novel devices make use of integrated active and passive structures usually as planar arrays. The electromagnetic design and computer simulation of these new structures requires novel numerical techniques. The Finite Difference Time Domain method (FDTD) is well suited for the electromagnetic analysis of integrated devices using active non-linear elements, but is difficult to use for large and/or periodic structures. A rigorous revision of this popular numerical technique is performed in order to permit FDTD to model practical quasi-optical devices. The system impulse response or discrete Green's function (DGF) for FDTD is determined as a polynomial then the FDTD technique is reformulated as a convolution sum. This new alternative algorithm avoids Absorbing Boundary Conditions (ABC's) and can save large amounts of memory to model wire or slot structures. Many applications for the DGF can be foreseen, going beyond quasi-optical components. As an example, the exact ABC based on the DGF for FDTD is implemented for a single grid wall is presented. The problem of time domain analysis of planar periodic structures modelling only one periodic cell is also investigated. Simple Periodic Boundary Conditions (PBC) can be implemented for FDTD, but they can not handle periodic devices (such as phased shift arrays or dichroic screens) which produce fields periodic in a 4D basis (three spatial dimensions plus time). An extended FDTD scheme is presented which uses Lorentz type coordinate transformations to reduce the problem to 3D. The analysis of non-linear devices using FDTD is also considered in the thesis. In this case, the non linear devices are always model using an equivalent lumped element circuit. These circuits are introduced into the FDTD grid by means of the current density following an iterative implicit algorithm. As a demonstration of the technique a quasi-optically feed slot ring mixer with integral lens is designed for operation at 650 GHz

Coupling into Waveguide Evanescent Modes with Applications in Electron Paramagnetic Resonance

The use of analytical and numerical techniques in solving the coupling of evanescent modes in a microwave waveguide through slots can be optimized to create a uniform magnetic field excitation on axis within a waveguide. This work has direct applications in Electron Paramagnetic Resonance (EPR) where a 100~kHz time-varying magnetic field is incident on a sample contained in a microwave cavity. Typical cavity designs do not take into consideration the uniformity of the 100~kHz field modulation and assume it to be uniform enough over the sample region from quasi-static principles. This work shows otherwise and uses Ansoft (Pittsburgh, PA) High Frequency Structure Simulator (HFSS; version 12.0) and analytical dyadic Green\u27s functions to understand the coupling mechanisms. The techniques described in this work have shown that electromagnetic modes form in a rectangular and cylindrical waveguide domain even at frequencies a number of orders of magnitude below the waveguide cut-off frequencies. With slot thicknesses very small compared to a wavelength, Born\u27s first approximation must be modified to account for a near field secondary wave. Additionally, mutual coupling between multiple slots has been shown to influence the overall magnetic field profile down the axis of the waveguide and in certain circumstances becomes more complex from interactions outside of the domain of the dyadic Green\u27s functions. A cylindrical TE01U cavity resonant at W-band (94~GHz) is proposed where both the microwave magnetic field and, from this work, the 100~kHz time-varying magnetic field incident on the sample are uniform. This type of resonator is highly desirable in EPR experiments where inhomogeneity of magnetic fields affect signal purity. With the technology outlined in this work, experiments where a uniform field modulation amplitude is swept over the entire spectra to obtain pure absorption is feasible. This work advances the cutting edge of resonator design and enables new experiments to be performed at high field EPR

13th Annual Review of Progress in Applied Computational Electromagnetics at the Naval Postgraduate School, Monterey, CA, March 17-21, 1997, Conference Proceedings Volumes I & II

Includes Volumes 1 &

Phase-reversal travelling-wave optical modulators for broadband and bandpass applications

This thesis is concerned with the analysis, fabrication, and characterisation of phase-reversal optical modulators for both broadband and bandpass applications. The operation of modulation is described together with the parameters by which optical modulators are characterised. Direct and indirect modulation are discussed. Particular attention is given to optical modulators constructed using titanium-indiffused lithium niobate technology. For these devices, the most important characteristics determining the frequency response and efficiency are studied. The technique of phase-reversal is examined as a means of artificial phase-matching. Systematic procedures for the design of phase-reversal electrode patterns are proposed. A novel class of equalising modulator is presented. A simulation of a digital lightwave system based on an equalising phase-reversal device is constructed. Transmission lines on anisotropic substrates are examined. The limitations of a quasi-static analysis are highlighted. A full-wave treatment utilising the method of lines is presented for the study of electrooptic modulators. Full-wave analysis is employed to study conventional coplanar waveguide electrooptic modulators. A new modulator structure, based on a fin line, is presented for high frequency operation. A comprehensive analysis of this structure is undertaken, including a modal analysis of a dielectric discontinuity. Designs are developed toward the demonstration of a device operating above 30GHz. A novel phase-matching technique, particularly suited to the fin line configuration, is discussed. The major processes involved in the fabrication of titanium- indiffused lithium niobate devices are briefly described. The techniques by which high speed modulators are measured are discussed, including a novel method by optical down-conversion. Experimental measurements are presented for devices operating in the frequency range 0 to 40GHz. The thesis is concluded, with suggestions for future avenues of research

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Electromagnetic Wave Theory and Applications

Contains table of contents for Section 3 and reports on seven research projects.Joint Services Electronics Program Contract DAAL03-89-C-0001National Science Foundation Contract ECS 86-20029Schlumberger- Doll ResearchU.S. Army Research Office Contract DAAL03 88-K-0057National Aeronautics and Space Administration Contract NAGW-1617U.S. Navy - Office of Naval Research Contract N00014-89-J-1107National Aeronautics and Space Administration Contract NAGW-1272National Aeronautics and Space Administration Contract 958461Simulation Technologies Contract DAAH01-87-C-0679U.S. Army Corp of Engineers Contract DACA39-87-K-0022WaveTracer, Inc.U.S. Navy - Office of Naval Research Contract N00014-89-J-1019U.S. Air Force Systems - Electronic Systems Division Contract F19628-88-K-0013Digital Equipment CorporationInternational Business Machines CorporationU.S. Department of Transportation Contract DTRS-57-88-C-0007

Advanced Electromagnetic Waves

This book endeavors to give the reader a strong base in the advanced theory of electromagnetic waves and its applications, while keeping pace with research in various other disciplines that apply electrostatics/electrodynamics theory. The treatment is highly mathematical, which tends to obscure the principles involved

A quasi-real-time inertialess microwave holographic imaging system

This thesis records the theoretical analysis and hardware development of a laboratory microwave imaging system which uses holographic principles. The application of an aperture synthesis technique and the electronic commutation of all antennae has resulted in a compact and economic assembly - which requires no moving parts and which, consequently, has a high field mapping speed potential. The relationship of this microwave holographic system to other established techniques is examined theoretically and the performance of the imaging system is demonstrated using conventional optically- and numerically-based reconstruction of the measured holograms. The high mapping speed potential of this system has allowed the exploitation of an imaging mode not usually associated with microwave holography. In particular, a certain antenna array specification leads to a versatile imaging system which corresponds closely in the laboratory scale to the widely used synthetic aperture radar principle. It is envisaged that the microwave holographic implementation of this latter principle be used as laboratory instrumentation in the elucidation of the interaction of hydrodynamic and electromagnetic waves. Some simple demonstrations of this application have been presented, and the concluding chapter also describes a suitable hardware specification. This thesis has also emphasised the hardware details of the imaging system since the development of the microwave and other electronic components represented a substantial part of this research and because the potential applications of the imaging principle have been found to be intimately linked to the tolerances of the various microwave components. Bibliography: pages 122-132