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Antennas and Propagation, IEEE Transactions on

Issue 11 • Date Nov. 2011

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Displaying Results 1 - 25 of 61
  • Table of contents

    Page(s): C1 - 3949
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  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
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  • A Novel Dual-Antenna Structure for UHF RFID Tags

    Page(s): 3950 - 3960
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1157 KB) |  | HTML iconHTML  

    A novel dual-antenna tag structure for UHF radio-frequency identification (RFID) systems is proposed. It is formed by two linearly tapered meander dipole antennas that are perpendicular to each other and connected to the slightly modified tag chip. One of the antennas is for receiving, while the other is for backscattering. The input impedance of the receiving antenna is designed to be conjugate matched to the highly capacitive chip impedance for the maximum power transfer. Meanwhile, the backscattering antenna is alternatively terminated by an open or a short circuit to modulate the backscattered field. By making the input impedance of the backscattering antenna real-valued, the maximum differential RCS may be achieved leading to a longer read range and better reliability. With the aid of the design of experiments (DOE) technique, the proposed dual-antenna structure is designed to fit within a compact area of 32.8 × 32.8 mm2 while keeping relatively low mutual coupling between the two antennas. The impedance, receiving, and backscattering performances of the proposed dual-antenna structure are measured and simulated, and they agree very well. Also, it is demonstrated that the proposed dual-antenna structure outperforms the conventional single-antenna tag design in every respect. View full abstract»

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  • Embedded Singularity Chipless RFID Tags

    Page(s): 3961 - 3968
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    Every structure scatters an impulse plane wave in a unique fashion. The structural information of an object can be extracted by analyzing the late-time scattered field as the impulse-response of the structure. The late-time scattered field, which represents the source-free response of the structure, contains a summation of damped sinusoids. The frequency and damping factor of these damped sinusoids are uniquely associated with the structural information, and can be used to identify an unknown object. We propose to create uniquely identifiable scattered fields from an object by incorporating “notches” in the structure giving rise to specific damped sinusoids in the source-free scattered field of the structure. In this manner, data can be embedded into the structure of an object which is detectable using electromagnetic waves, allowing a metallic object to serve as a chipless radio-frequency identification tag (RFID). Data is encoded as complex natural resonant frequencies (referred to as poles) in the structure and is retrieved from the scattered field. Data retrieval is based on Singularity Expansion Method (SEM) analysis using target identification techniques. Each complex-frequency pole provides two-dimensional data (real and imaginary) which can be extracted from the late-time impulse response of the structure using a numerical technique such as the Matrix Pencil Method. We have designed and prototyped a 6-bit (3-pole) tag. The tag is analyzed using simulations and measurements. The tag is successfully read remotely via its scattered fields. The measured data are compared with simulation, and are in close agreement. View full abstract»

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  • External-Excitation Curl Antenna

    Page(s): 3969 - 3977
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    A strip curl antenna is investigated for obtaining a circularly-polarized (CP) tilted beam. This curl is excited through a strip line (called the excitation line) that connects the curl arm to a coaxial feed line. The antenna structure has the following features: a small circumference not exceeding two wavelengths and a small antenna height of less than 0.42 wavelength. The antenna arm is printed on a dielectric hollow cylinder, leading to a robust structure. The investigation reveals that an external excitation for the curl using a straight line (ST-line) is more effective for generating a tilted beam than an internal excitation. It is found that the axial ratio of the radiation field from the external-excitation curl is improved by transforming the ST-line into a wound line (WD-line). It is also found that a modification to the end area of the WD-line leads to an almost constant input impedance (50 ohms). Note that these results are demonstrated for the Ku-band (from 11.7 GHz to 12.75 GHz, 8.6% bandwidth). View full abstract»

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  • Investigation on the EM-Coupled Stacked Square Ring Antennas With Ultra-Thin Spacing

    Page(s): 3978 - 3990
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    Stacked electromagnetically coupled square ring antennas with extremely thin spacing are studied. The separation between rings is kept very small so that they do not increase the overall antenna height, yet can provide multiband operation. The coupling effects among these very closely placed rings are studied based on substrate parameters so that they can be practically implemented using commercially available microwave substrates. It is observed that with an asymmetric arrangement of the stacked rings, different polarizations can be obtained for different resonances. However, if a fixed polarization is desired, a concentric stacked rings configuration has to be used. Experimental investigations are conducted to confirm simulation results. View full abstract»

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  • Choosing Dielectric or Magnetic Material to Optimize the Bandwidth of Miniaturized Resonant Antennas

    Page(s): 3991 - 3998
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    We address the question of the optimal choice of loading material for antenna miniaturization. A new approach to identify the optimal loading material (dielectric or magnetic) for maximization of bandwidth of resonant antennas is introduced. Instead of equivalent resonant circuits or transmission-line resonators, we use the analysis of radiation mechanism to identify the fields contributing mostly to the stored energy and determine the beneficial material type. The formulated rule is qualitatively illustrated using a dipole and a patch antenna, as well as a planar inverted-L antenna where the conventional analysis of circuit or a transmission-line resonator leads to incorrect conclusions. Guidelines are presented for miniaturizing different antenna types. View full abstract»

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  • Rectilinear Leaky-Wave Antennas With Broad Beam Patterns Using Hybrid Printed-Circuit Waveguides

    Page(s): 3999 - 4007
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    A theoretical study on the design of broadbeam leaky-wave antennas (LWAs) of uniform type and rectilinear geometry is presented. A new broadbeam LWA structure based on the hybrid printed-circuit waveguide is proposed, which allows for the necessary flexible and independent control of the leaky-wave phase and leakage constants. The study shows that both the real and virtual focus LWAs can be synthesized in a simple manner by tapering the printed-slot along the LWA properly, but the real focus LWA is preferred in practice. Practical issues concerning the tapering of these LWA are investigated, including the tuning of the radiation pattern asymmetry level and beamwidth, the control of the ripple level inside the broad radiated main beam, and the frequency response of the broadbeam LWA. The paper provides new insight and guidance for the design of this type of LWAs. View full abstract»

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  • Vivaldi Antenna With Integrated Switchable Band Pass Resonator

    Page(s): 4008 - 4015
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    A novel reconfigurable wideband to narrowband Vivaldi antenna is presented. A single pair of ring slot resonators is located in the Vivaldi to realize frequency reconfiguration, maintaining the original size unchanged. The proposed antenna is capable of switching six different narrow pass bands within a wide operating band of 1-3 GHz, offering added prefiltering functionality. A fully functional prototype has been developed. PIN diode switches were employed at specific locations in the resonator to change its effective electrical length, hence forming different filter configurations. Antenna performance obtained from simulation and measurement results shows good agreement, which verifies the proposed design concepts. The antenna is potentially suitable for applications requiring dynamic band switching such as cognitive radio. View full abstract»

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  • A Seamless Integration of 3-D Vertical Filters With Highly Efficient Slot Antennas

    Page(s): 4016 - 4022
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    A seamless integration of 3-D vertical cavity filters with highly efficient slot antennas is presented herein. This integration technique enables low-loss filtering and reduces co-site interference within phased arrays. A vertical two-pole cavity filter integrated with a slot antenna is demonstrated at X band. The center frequency and fractional bandwidth of the filter/antenna system are 10.16 GHz and 3.0%, respectively. Due to the near-zero transition loss achieved by this seamless integration, the efficiency of the integrated slot antenna is shown to be as high as 97%. Equivalent circuit models are developed to identify the losses in the filter/antenna, which are verified by full-wave simulations. The measured impedance matching and radiation patterns closely agree with simulation results. This technique can be extended for higher-order filters seamlessly integrated with slot antennas. In addition, this technique can be applied in all microwave, millimeter-wave, and submillimeter-wave frequency regions. View full abstract»

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  • Rigorous MoM Analysis of Finite Conductivity Effects in RLSA Antennas

    Page(s): 4023 - 4032
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    Although slot antennas are usually modeled as perfectly electric conductors, for accurate antenna design and optimization, ohmic loss effects cannot be neglected. This is especially true in millimeter and submillimeter-wave applications, and in low-cost technology for mass production, where highly conductive surfaces are out of budget. This paper presents a rigorous but efficient method-of-moments (MoM) formulation for the analysis of radial line slot array (RLSA) antennas, which includes the finite conductivity of metals. First, by using equivalence and reciprocity theorems, effective magnetic currents are defined on each slot aperture, instead of standard electric and magnetic equivalent currents. This choice halves the number of unknowns of the MoM linear system, still preserving the rigor of the electromagnetic formulation. Next, proper Green's functions accounting for the finite conductivity of metals are derived analytically and used in the MoM admittance matrix expressions. A numerical check of self and mutual admittances for a couple of slots etched in a nonperfectly conducting structure is provided against results from a finite-element method. Finally, a few RLSA realizations are analyzed to investigate the effect of ohmic losses in a practical antenna design. View full abstract»

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  • A UWB Unidirectional Antenna With Dual-Polarization

    Page(s): 4033 - 4040
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1956 KB) |  | HTML iconHTML  

    A novel ±45° dual-polarized unidirectional antenna element is presented, consisting of two cross center-fed tapered mono-loops and two cross electric dipoles located against a reflector for ultrawideband applications. The operation principle of the antenna including the use of elliptically tapered transmission line for transiting the unbalanced energy to the balanced energy is described. Designs with different reflectors-planar or conical-are investigated. A measured overlapped impedance bandwidth of 126% (SWR <; 2) is demonstrated. Due to the complementary nature of the structure, the antenna has a relatively stable broadside radiation pattern with low cross polarization and low back lobe radiation over the operating band. The measured gain of the proposed antenna varies from 4 to 13 dBi and 7 to 14.5 dBi for port 1 and port 2, respectively, over the operating band, when mounted against a conical backed reflector. The measured coupling between the two ports is below -25 dB over the operating band. View full abstract»

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  • Flat-Shaped Dielectric Lens Antenna for 60-GHz Applications

    Page(s): 4041 - 4048
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1616 KB) |  | HTML iconHTML  

    We describe the performance of a flat shaped dielectric lens antenna designed to produce a flat-top beam in H-plane and a nearly omni-directional pattern in E-plane in the 60-GHz band. Such radiation characteristics may be useful for access points or user terminals in high data rate wireless local area networks. For the antenna design, a specific two-stage methodology combining 2-D and 3-D modeling has been implemented. First, the lens shape is optimized in 2-D using a 2-D FDTD kernel coupled to a genetic algorithm. Second, all building blocks of the final antenna (3-D lens with a finite thickness, antenna feed) are optimized using the solution of the 2-D problem as an initial guess. This strategy has been validated experimentally: a 2.5-mm-thick flat lens in Rexolite with a shaped profile in H-plane has been fabricated and measured. It is shielded by two 1-mm-thick half metallic disks. The radiation patterns are very stable from 57 to 63 GHz, and the total antenna efficiency is better than 50%. View full abstract»

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  • Spherical Near-Field Scanning With Higher-Order Probes

    Page(s): 4049 - 4059
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (579 KB) |  | HTML iconHTML  

    A general method for higher-order probe correction in spherical scanning is obtained from a renormalized least-squares approach. The renormalization causes the normal matrix of the least-squares problem to closely resemble the identity matrix when most of the energy of the probe pattern resides in the first-order modes. The normal equation can be solved either with a linear iterative solver (leading to an iterative scheme), or with a Neumann series (leading to a direct scheme). The computation scheme can handle non-symmetric probes, requires only the output of two independent ports of a dual-polarized probe, and works for both φ and θ scans. The probe can be characterized either by a complex dipole model or by a standard spherical-wave representation. The theory is validated with experimental data. View full abstract»

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  • The Banyan Tree Antenna Array

    Page(s): 4060 - 4070
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2352 KB) |  | HTML iconHTML  

    A new wideband, wide-scan array is introduced, called the Banyan Tree Antenna (BTA) array, that employs modular, low-profile, low-cost elements fed directly from standard unbalanced RF interfaces. The elements consist of vertically-integrated, flared metallic fins over a ground plane that are excited by a vertical two conductor unbalanced transmission line. The antenna resembles the bunny-ear or balanced antipodal Vivaldi antenna (BAVA) designs, but most importantly uses metallic shorting posts between the fins and the ground plane that suppress a mid-band catastrophic common-mode resonance that occurs in 2D arrays of balanced radiators fed with unbalanced feeds. This work introduces simple circuit models that describe key performance attributes of the BTA array, leading to unique physical insights and design guidelines. Simulations of infinite single- and dual-polarized BTA arrays have achieved approximately two octaves of bandwidth for VSWR <; 2.2 at broadside and VSWR <; 2.8 at scans out to θ = 45°, while maintaining better than 14 dB polarization purity at θ = 45° in the D-plane. View full abstract»

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  • Wide-Angle Scanning Phased Array With Pattern Reconfigurable Elements

    Page(s): 4071 - 4076
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    A novel phased array is presented to extend array scanning range by using pattern reconfigurable antenna elements and weighted thinned synthesis technology in this paper. The pattern reconfigurable microstrip Yagi antenna element is used as a basic element in array and it is capable of reconfiguring its patterns from broadside to quasi-endfire radiation by shifting states of the PIN diode switches integrated on parasitic strips. A weighted thinned linear array synthesis technique is analyzed and some interesting conclusions have been made. A linear array composed of eight pattern reconfigurable antenna elements is manufactured to demonstrate the excellent performance of the array. The active element pattern of each element is measured and pre-stored. Based on active element patterns and weighted thinned linear array synthesis technique, the pattern scanning performance of the novel array is synthesized. The results indicate that the array can scan its main beam from φ = -60° to φ = 60° in H-plane with gain fluctuation less than 3 dB while maintaining low side lobes, and the -3 dB beam width coverage is about from φ = -68° to φ = 68°. The performance is superior to the traditional phased array made of wide-beam elements. View full abstract»

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  • Microstrip Grid and Comb Array Antennas

    Page(s): 4077 - 4084
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    The design of a high-gain microstrip grid array antenna (MGAA) for 24-GHz automotive radar sensor applications is first presented. An amplitude tapering technique utilizing variable line width on the individual radiating element is then applied to lower sidelobe level. Next, the MGAA is simplified to a microstrip comb array antenna (MCAA). The MCAA shows broader impedance bandwidth and lower cross-polarization radiation as compared with those of the MGAA. The MCAA is designed not as a travelling-wave but a standing-wave antenna. As a result, the match load and the reflection-cancelling structure can be avoided, which is important, especially in the millimeter-wave frequencies. Finally, an emphasis is given to 45° linearly-polarized MCAA because the radiation with the orthogonal polarization from cars coming from the opposite direction does not affect the radar operation. View full abstract»

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  • A Novel Deterministic Synthesis Technique for Constrained Sparse Array Design Problems

    Page(s): 4085 - 4093
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1263 KB) |  | HTML iconHTML  

    A novel analytical approach to the synthesis of linear sparse arrays with non-uniform amplitude excitation is presented and thoroughly discussed in this paper. The proposed technique, based on the concept of auxiliary array factor, is aimed at the deterministic determination of the optimal array element density and excitation tapering distributions useful to mimic a desired radiation pattern. In particular, the developed antenna placement method does not require any iterative or stochastic optimization procedure, resulting in a dramatic reduction of antenna design times. Selected examples are included in order to assess the effectiveness and versatility of the proposed approach in the framework of aperiodic array synthesis problems. View full abstract»

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  • Evolutionary Design of Wide-Band Parasitic Dipole Arrays

    Page(s): 4094 - 4102
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    An innovative antenna design technique, based on evolutionary programming, has been devised and applied to the design of broadband parasitic wire arrays for VHF-UHF bands with a significant gain. The chosen fitness function includes far-field requirements, as well as wideband input matching specifications. The latter requirements, which must be present in every useful antenna design, allow to stabilize the algorithm, and to design both optimal and robust antennas. The designed antennas show significant improvements over existing solutions (Yagi and LPDA) for the same frequency bands. View full abstract»

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  • The Placement of Antenna Elements in Aperture Synthesis Microwave Radiometers for Optimum Radiometric Sensitivity

    Page(s): 4103 - 4114
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    Antenna array configurations have significant influence on the radiometric sensitivity of aperture synthesis microwave radiometers. In this paper, we propose a minimum degradation array (MDA) for optimum sensitivity. First, the degradation factor (DF) is defined to characterize the effect of redundant spatial frequency samples formed by an array on the sensitivity. Aiming at minimizing DF, a simulated annealing (SA) based method is proposed to search for an MDA, which, combining with a concept of augmented maximum baseline (CAMB), can effectively locate the true global minimum of DF. Numerical results validate the effectiveness of the proposed method as well as CAMB in optimizing DF. Further, the lower bound of DF is discussed. Finally, simulation and experiment results demonstrate that the proposed method as well as CAMB is of significance in achieving optimum sensitivity. View full abstract»

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  • Fast and Accurate Array Calibration Using a Synthetic Array Approach

    Page(s): 4115 - 4122
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    A new method for the calibration of arrays is presented that allows the simultaneous calibration of N array elements. It comprises the measurement of the array output signal at M phase settings applied to the N elements involved in the calibration. These M phase settings correspond to a linear phase taper that is unique for each of the involved elements and reveals therefore N different phase tapers. The complex M measurements of the array signal are thought to be the excitation coefficients of a synthetic M -element linear phased array. The array factor of this synthetic M-element array comprises a superposition of N+1 array factors all pointing with their main beam into different directions. By converting this superposition of N+1 array factors into a set of N+1 simultaneous linear equations, the signals of the N individual elements to be calibrated including the combined signal contribution of the static elements, can be solved by standard matrix inversion techniques. Computer simulations are presented to demonstrate the capabilities of the new calibration method. View full abstract»

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  • Application of Analytical Retarded-Time Potential Expressions to the Solution of Time Domain Integral Equations

    Page(s): 4123 - 4131
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    Recently, exact closed-form expressions of the electric and magnetic fields and potentials due to impulsively excited Rao-Wilton-Glisson basis functions have been presented. In this work, the application of these expressions in the solution of the combined field integral equation (CFIE) is presented. Solutions via analytical expressions of the electric and magnetic fields are verified and compared with the conventional marching-on-in time (MOT) algorithm solutions that employ numerical basis integrations. It is shown that the accuracy and stability of the solutions obtained with the proposed (analytical) approach are better when compared to those obtained with the conventional (numerical) method. In addition, a discussion section about the effect of the proposed approach in solving the electric field integral equation (EFIE) is added. In this section, it is demonstrated that the dependency of the solution via analytical expressions of the fields are less sensitive to the time step size in comparison to the conventional solution, and that the increase in accuracy is a necessary but not sufficient condition for stability. View full abstract»

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  • Hierarchical Matrix Techniques Based on Matrix Decomposition Algorithm for the Fast Analysis of Planar Layered Structures

    Page(s): 4132 - 4141
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (689 KB) |  | HTML iconHTML  

    The matrix decomposition algorithm (MDA) provides an efficient matrix-vector product for the iterative solution of the integral equation (IE) by a blockwise compression of the impedance matrix. The MDA with a singular value decomposition (SVD) recompression scheme, i.e., so-called MDA-SVD method, shows strong ability for the analysis of planar layered structures. However, iterative solution faces the problem of convergence rate. An efficient hierarchical (H-) LU decomposition algorithm based on the H-matrix techniques is proposed to handle this problem. Exploiting the data-sparse representation of the MDA-SVD compressed impedance matrix, H -LU decomposition can be efficiently implemented by H-matrix arithmetic. H-matrix techniques provide a flexible way to control the accuracy of the approximate H-LU-factors. H-LU decomposition with low accuracy can be used as an efficient preconditioner for the iterative solver due to its low computational cost, while H-LU decomposition with high accuracy can be used as a direct solver for dealing with multiple right-hand-side (RHS) vector problems particularly. Numerical examples demonstrate that the proposed method is very robust for the analysis of various planar layered structures. View full abstract»

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  • Fast Frequency Sweep of FEM Models via the Balanced Truncation Proper Orthogonal Decomposition

    Page(s): 4142 - 4154
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    A fast frequency sweep method for wideband antennas and infinite arrays based on a singular value decomposition (SVD)-Krylov model reduction method for frequency-domain tangential vector finite elements (TVFEMs) is presented. Reduced models are constructed using balanced congruence transformations constructed from the dominant invariant subspace of the system's Hankel matrix. Traditionally, forming such matrix requires the intensive computation of Gramians; the proposed method only forms their low-rank Cholesky factors via a novel adaptive proper orthogonal decomposition (POD) sampling strategy, leading to significant savings. Unlike some other model reduction methods, balanced truncation POD (BT-POD) is directly applicable to lossy and dispersive electromagnetic models. Numerical studies on large-scale wideband antennas and infinite arrays show that the method is stable, error controllable and, without memory overheads capable of up to two orders-of-magnitude speed-ups. View full abstract»

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  • Modeling of Nanophotonic Resonators With the Finite-Difference Frequency-Domain Method

    Page(s): 4155 - 4161
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    Finite-difference frequency-domain method with perfectly matched layers and free-space squeezing is applied to model open photonic resonators of arbitrary morphology in three dimensions. Treating each spatial dimension independently, nonuniform mesh of continuously varying density can be built easily to better resolve mode features. We explore the convergence of the eigenmode wavelength λ and quality factor Q of an open dielectric sphere and of a very-high- Q photonic crystal cavity calculated with different mesh density distributions. On a grid having, for example, 10 nodes per lattice constant in the region of high field intensity, we are able to find the eigenwavelength λ with a half-percent precision and the Q-factor with an order-of-magnitude accuracy. We also suggest the λ/n rule (where n is the cavity refractive index) for the optimal cavity-to-PML distance. View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung