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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Find the most up-to-date and comprehensive treatment of classical and modern antennas and their related technologies in Modern Antenna Handbook. Have access to current theories and practices in the field of antennas, with topics like metamaterials, microelectromechanical systems (MEMS), frequency selective surfaces (FSS), radar cross sections (RCS), and advanced numerical and computational methods targeted primarily for the analysis and design of antennas. Written by leading international experts, this book will help you understand recent developments in antenna-related technology and the future direction of this fast-paced field.

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Modern Antenna Handbook

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

An overview is given over some of the most widely used numerical techniques for solving the electromagnetic scattering problem that start from rigorous electromagnetic theory. In particular, the theoretical foundations of the separation of variables method, the finite-difference time-domain method, the finite-element method, the method of lines, the point matching method, the method of moments, the discrete dipole approximation, and the null-field method (or extended boundary condition method) are reviewed, and the advantages and disadvantages of the different methods are discussed. Aspects concerning the T matrix formulation and the surface Green's function formulation of the electromagnetic scattering problem are addressed.

Numerical methods in electromagnetic scattering theory

This is a book review of 'The Micro-Doppler Effect in Radar' by V. C. Chen. Artech House, 16 Sussex Street, London, SW1V 4RW, UK. 2011. 290pp + diskette. Illustrated. £90. ISBN 978-1-60807-057-2.

'The Micro-Doppler Effect in Radar' by V.C. Chen

Electromagnetic band-gap (EBG) structures have noteworthy electromagnetic characteristics that include their reflection phase variations with frequency. This paper applies this unique reflection phase property to alter the direction of the fields scattered by a radar target to reduce its radar cross section (RCS). This redirecting of the scattered fields occurs when a surface is covered with a checkerboard of alternating EBG structures, and results in a wider frequency band RCS reduction. RCS reduction compared to a PEC surface of 10 dB can be realized over 60% frequency bandwidth. Simulations of monostatic and bistatic RCSs of two dual EBG checkerboard surfaces, square and hexagonal, are compared with those of equal-sized PEC ground planes. The simulated monostatic RCS is also compared with measurements. Both $\bf{TE}^{\bf{z}}$ and $\bf{TM}^{\bf{z}}$ polarizations for oblique incidence are considered. Excellent agreement is obtained between simulated and measured patterns, for both the square and the hexagonal EBG checkerboard surfaces. An approximate analytical expression is provided as a guideline for a 10-dB RCS reduction of a dual EBG checkerboard surface compared to that of a PEC.

Checkerboard EBG Surfaces for Wideband Radar Cross Section Reduction

A novel technique for designing ultrabroadband radar cross section (RCS) reduction surfaces using artificial magnetic conductors (AMCs) is proposed in this paper. This technique overcomes the fundamental limitation of the conventional checkerboard design where the reflection phase difference of (180±37)° is required to achieve 10-dB RCS reduction. Initially, a planar surface for broadband RCS reduction is designed with two properly selected AMCs in a blended checkerboard architecture. A 10-dB RCS reduction is observed for more than 83% of the bandwidth (3.9–9.45 GHz) with this blended checkerboard design. After modifying the blended checkerboard design using the proposed novel technique, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth (3.75–10 GHz) as the criteria of (180 ± 37)° reflection phase difference is no longer required. Measured data show an excellent agreement between the predicted, simulated, and measured data. Bistatic performance of the surface at various frequencies is also presented. Key steps for designing ultrabroadband RCS reduction checkerboard surface are summarized.

Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces Using Artificial Magnetic Conductors

This letter presents a wearable flexible reconfigurable folded slot antenna. The antenna is composed of a folded slot and a stub where the reconfigurability is achieved by turning a p-i-n diode on and off , which alters the radiation characteristics of the stub. The operating frequency and polarization of the slot and stub are different. Hence, a polarization-dependent dual-band artificial magnetic conductor (AMC) surface is integrated with the antenna to improve its radiation performance and to reduce the specific absorption rate (SAR). The antenna is designed and fabricated on a flexible substrate, and its performance is measured for both flat and curved configurations. The measurements show an excellent agreement with the simulations. To examine its performance as a wearable antenna, it is measured on a human body. Simulations show that the SAR level is reduced when the AMC surface is used as an isolator. The proposed wearable antenna structure can be used for wireless body area network (WBAN) and Worldwide Interoperability for Microwave Access (WiMAX) body-worn wireless devices.

Wearable Flexible Reconfigurable Antenna Integrated With Artificial Magnetic Conductor

This paper presents the design of a novel planar scalar impedance holographic metasurface, which is capable of beam forming with a desired electric field polarization and high gain. It is demonstrated that the surface can be constructed with patches of simple geometry and design. A detailed analysis of the mechanism of scalar impedance holographic metasurfaces is discussed. The scalar impedance holographic metasurface is designed at a dominant TM surface wave mode frequency. It is observed that the TM surface wave mode has an impurity of TE polarized electric fields of small magnitude. The presence of this impurity is exploited to design a holographic metasurface for beam forming with a desired polarization. This modified-HAIS is capable of forming a beam at a nonphase crossover frequency, unlike the conventional HAIS. The design procedure of the surface, with simulation and measurement results, is presented.

Design of Scalar Impedance Holographic Metasurfaces for Antenna Beam Formation With Desired Polarization

Design, simulation, fabrication and measurement of two different novel flexible bow-tie antennas, a conventional and a modified bow-tie antenna with reduced metallization, are reported in this paper. The antennas are mounted on a flexible substrate fabricated at the Flexible Display Center (FDC) of Arizona State University (ASU). The substrate is heat stabilized polyethylene naphthalate (PEN) which allows the antennas to be flexible. The antennas are fed by a microstrip-to-coplanar feed network balun. The reduction of the metallization is based on the observation that the majority of the current density is confined towards the edges of the regular bow-tie antenna. Hence, the centers of the triangular parts of the conventional bow-tie antenna are removed without compromising significantly its performance. The return losses and radiation patterns of the antennas are simulated with HFSS and the results are compared with measurements, for bow-tie elements mounted on flat and curved surfaces. The comparisons show that there is an excellent agreement between the simulations and measurements for both cases. Furthermore, the radiation performance of the modified bow-tie antenna is verified, by simulations and measurements, to be very close to the conventional bow-tie.

Craig R. Birtcher

Papers

Checkerboard EBG Surfaces for Wideband Radar Cross Section Reduction

Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces Using Artificial Magnetic Conductors

Wearable Flexible Reconfigurable Antenna Integrated With Artificial Magnetic Conductor

Design of Scalar Impedance Holographic Metasurfaces for Antenna Beam Formation With Desired Polarization

Design, Simulation, Fabrication and Testing of Flexible Bow-Tie Antennas