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Antennas and Propagation, IEEE Transactions on

Issue 9 • Date Sept. 2006

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Displaying Results 1 - 25 of 43
  • Table of contents

    Publication Year: 2006 , Page(s): c1 - 2445
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  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2006 , Page(s): c2
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  • Analytically Derived Uplink/Downlink TOA and 2-D-DOA Distributions With Scatterers in a 3-D Hemispheroid Surrounding the Mobile

    Publication Year: 2006 , Page(s): 2446 - 2454
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    This paper presents the open literature's first closed-form explicit expressions of the trivariate joint and marginal distributions of a landmobile cellular wireless communication system's uplink and downlink multipaths' time of arrival and two-dimensional direction of arrival, rigorously derived via thorough mathematics based on a "geometrical" model of the three-dimensional (3-D) spatial relationships among the mobile station, the scatterers, and the base station. The scatterers are herein modeled to have a uniform 3-D spatial distribution in an aboveground hemisphere with a flat circular base (or alternatively, within a sphere) centered at the mobile View full abstract»

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  • Radar Target Recognition Based on Late Time Representation: Closed-Form Expression for Criterion

    Publication Year: 2006 , Page(s): 2455 - 2462
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    In the previous paper, we have defined the normalized estimation error and presented the radar target recognition scheme in frequency domain. A time-domain version of the previous paper is considered and a closed-form expression for the defined normalized estimation error in terms of Z-plane natural frequencies and transient response is derived. Evaluation of the closed-form expression of the normalized estimation error is shown in the numerical results, where it is shown that the performance of the radar target recognition scheme improves with an increase of the number of the natural frequencies and with an increase of signal-to-noise ratio. Furthermore, the mean and the variance of the square of the numerator of the normalized estimation error are obtained, and the validity of the statistics is shown using the numerical results View full abstract»

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  • Analytic Analysis of Transient Scattering From a Finite Second-Order Surface Illuminated by an Incident Plane Wave

    Publication Year: 2006 , Page(s): 2463 - 2471
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (479 KB) |  | HTML iconHTML  

    A closed-form analytic solution based on a time-domain (TD) physical optics (PO) approximation is developed for the scattering from a finite second-order surface when illuminated by a transient impulsive plane wave. This TD-PO solution can be applied via a convolution to derive the early time transient fields scattered from the same scatterer that is illuminated by a realistic astigmatic finite-energy pulse. The closed form TD-PO solution is obtained by inverting the corresponding frequency-domain PO solution into TD. This solution can be expressed in terms of reflection and diffraction components of the scattering mechanisms as in other conventional high-frequency asymptotic solutions. Numerical examples are presented to demonstrate its physical phenomenon of the scattering mechanisms View full abstract»

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  • Wiener-Hopf Solution for Impenetrable Wedges at Skew Incidence

    Publication Year: 2006 , Page(s): 2472 - 2485
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1242 KB) |  | HTML iconHTML  

    A new Wiener-Hopf approach for the solution of impenetrable wedges at skew incidence is presented. Mathematical aspects are described in a unified and consistent theory for angular region problems. Solutions are obtained using analytical and numerical-analytical approaches. Several numerical tests from the scientific literature validate the new technique, and new solutions for anisotropic surface impedance wedges are solved at skew incidence. The solutions are presented considering the geometrical and uniform theory of diffraction coefficients, total fields, and possible surface wave contributions View full abstract»

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  • Usability Studies on Approximate Corrugation Models in Scattering Analysis

    Publication Year: 2006 , Page(s): 2486 - 2496
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB) |  | HTML iconHTML  

    Often an actual scatterer geometry is replaced with a computationally more economical model. For example, if a major part of the scatterer surface is corrugated, one solution is to analyze scattering by replacing the corrugated areas with flat impedance surfaces. But then a question arises: what is actually the error in the scattered field phase and magnitude due to this approximation? In this paper, planewave scattering from partly corrugated structures is studied. The analysis is based on integral equations (IE) and method of moments (MoM). Two-dimensional geometry and fields are assumed. TMz and TEz cases are analyzed separately. It is investigated how the magnitude and phase of the scattered TMz and TEz fields depend on the used corrugation model: exact-geometry results are compared with the approximate results in a wide frequency band. Also the phases of the TMz and TEz fields must be predicted correctly, if studying the polarization state of the scattered field. The paper ends with an example where a corrugated corner reflector is investigated via an exact model and via different approximate models View full abstract»

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  • Shape Reconstruction of Three-Dimensional Conducting Curved Plates Using Physical Optics, NURBS Modeling, and Genetic Algorithm

    Publication Year: 2006 , Page(s): 2497 - 2507
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1508 KB) |  | HTML iconHTML  

    A microwave inverse scattering problem including a method for shape reconstruction of three-dimensional electrically large conducting patches with simple geometries using genetic algorithm is presented. Unknown shape reconstruction algorithm starts from the knowledge of the simulated radar cross-section (RCS) data through back-scattering far-field computation using physical optics approximation. The forward problem involves the computation of the multiple-frequency and multiple-direction RCS of three-dimensional large conducting patches modeled by nonuniform rational B-spline (NURBS) surfaces. The control points of NURBS are the geometrical parameters, which are optimized for the shape reconstruction procedure. The extended stationary phase method and critical cases, which occur in physical optics computations in the forward problem, are also discussed. Noise effect and the influence of increment in the number of control points of a NURBS over the inversion algorithm are investigated as well. Numerical results are presented to verify the operation of the proposed algorithm View full abstract»

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  • A Spectral Domain Integral Equation Method Utilizing Analytically Derived Characteristic Basis Functions for the Scattering From Large Faceted Objects

    Publication Year: 2006 , Page(s): 2508 - 2514
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    A novel technique, based on a spectral domain integral equation method with analytically derived characteristic basis functions, is introduced in this paper. It enables us to treat scattering problems from electrically large faceted bodies in a numerically rigorous and computationally efficient manner, in terms of both time and memory. The analytically derived characteristic basis functions include certain desirable features of the asymptotic schemes and are defined on subdomains that can be electrically large, not being bound to the typical discretization size of the conventional method of moments. By properly weighting through a Galerkin procedure the resulting electric field integral equation, the problem is reduced to a matrix equation having dimensions that do not depend on the size of the scatterer but only on its shape. Electrically large problems can be handled in a computationally efficient manner by using the proposed method since the associated matrix size is relatively small; moreover, all the reduced matrix elements are calculated in the spectral domain without evaluating any convolution products View full abstract»

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  • Generalization of the Finite-Difference-Based Time-Domain Methods Using the Method of Moments

    Publication Year: 2006 , Page(s): 2515 - 2524
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (421 KB) |  | HTML iconHTML  

    Many finite-difference-based time-domain methods have been developed in the past three decades. Typical among them are the finite-difference time-domain method of Yee's scheme, the transmission-line-matrix method, the multiresolution time-domain method, the pseudospectral time-domain method, and the unconditionally stable finite-difference time-domain methods. All these methods have become powerful tools in solving electromagnetic structure problems, yet their formulations appear to be unrelated. The concept of the method of moments (MoM) is applied in this paper to generalize all these different finite-difference-based methods. It is shown theoretically that differences among various finite-difference-based methods lie in different choices of basis functions used in solution expansions and weighting functions in error testing, in both time and space. The significance of this paper is twofold: 1) all the finite-difference time-domain-based methods can now be unified under the framework of MoM and 2) any other new finite-difference-based time-domain methods, including hybrid techniques, may now be developed with MoM procedure View full abstract»

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  • Stability and Numerical Dispersion Analysis of a Fourth-Order Accurate FDTD Method

    Publication Year: 2006 , Page(s): 2525 - 2530
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    In order to obtain high-order accuracy, a fourth-order accurate finite difference time-domain (FDTD) method is presented by Kyu-Pyung Hwang. Unlike conventional FDTD methods, a staggered backward differentiation scheme instead of the leapfrog scheme is used to approximate the temporal partial differential operator. However, the high order of its characteristic equation derived by the Von Neumann method makes the analysis of its numerical dispersion and stability very difficult. In automatic control theory, there are two effective methods for the stability analysis, i.e., the Routh-Hurwitz test and the Jury test. The combination of the Von Neumann method with each of the two can strictly derive the stability condition, which only makes use of the coefficients of its characteristic equation without numerically solving it. The method of analysis in this paper is also applicable in the stability and numerical analysis of other high-order accurate FDTD methods View full abstract»

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  • Analytic Field Propagation TFSF Boundary for FDTD Problems Involving Planar Interfaces: PECs, TE, and TM

    Publication Year: 2006 , Page(s): 2531 - 2542
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    A total-field scattered-field (TFSF) boundary can be used to introduce incident plane waves into finite-difference time-domain (FDTD) simulations. For fields which are traveling obliquely to the grid axes, there is no simple way to account fully for the effects of the inherent numerical artifacts associated with plane-wave propagation in the FDTD grid. Failure to account for these artifacts causes erroneous fields to leak across the TFSF boundary. Recent publications have proposed ways to use the dispersion relation to describe precisely plane-wave propagation in the FDTD grid thus permitting the realization of a nearly perfect TFSF boundary. However, these publications did not cover certain implementations details (such as the type of Fourier transform which is needed) or their scope was so broad as to mask the relative simplicity with which the approach can be applied to problems involving planar interfaces. This work considers the Fourier transforms needed in order for the implementation to be exact. Reflection and transmission coefficients for a planar interface are derived. Implementation for planar perfect electric conductors is also presented View full abstract»

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  • Maximin Algorithm With a Step-Length Estimation Technique

    Publication Year: 2006 , Page(s): 2543 - 2552
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (609 KB) |  | HTML iconHTML  

    We propose a technique that enhances the performance of Torrieri and Bakhru's maximin algorithm in the presence of frequency offsets and modulated interferences, a common scenario in multiple-access environments, where we observed that the Maximin algorithm suffers performance degradation in the aforesaid scenario. To combat modulated interferences and fading effects, we propose to update the step length during every smart antenna weight vector update. We found that our scheme improves the robustness of the maximin algorithm to a greater extent. Simulation results for a frequency-hopping system confirm the validity of the approach and demonstrate improvements in the performance of the maximin algorithm in the presence of frequency offsets and data modulated interferences in a fading channel environment View full abstract»

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  • Losses in the PEMC Boundary

    Publication Year: 2006 , Page(s): 2553 - 2558
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    Perfect electromagnetic conductor (PEMC) was recently introduced to generalize both the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC), which are used as boundary material. In this paper, an extension of PEMC boundary conditions is made to a more realistic model with small losses ("good electromagnetic conductor"). It is shown that the antisymmetric boundary impedance dyadic defining the ideal PEMC boundary cannot alone carry any losses and a symmetric component must be added that actually dominates the lossy behavior of the boundary. As an example, a slab of low-loss gyrotropic wave-guiding material is studied and shown to represent the lossy counterpart of the PEMC boundary. The effect of losses is demonstrated by considering plane-wave reflection from an imperfect PEMC plane View full abstract»

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  • Efficient Computation of Nonparaxial Surface Fields Excited on an Electrically Large Circular Cylinder With an Impedance Boundary Condition

    Publication Year: 2006 , Page(s): 2559 - 2567
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (701 KB) |  | HTML iconHTML  

    An alternative numerical approach is presented for the evaluation of the Fock-type integrals that exist in the uniform geometrical theory of diffraction (UTD)-based asymptotic solution for the nonparaxial surface fields excited by a magnetic or an electric source located on the surface of an electrically large circular cylinder with an impedance boundary condition (IBC). This alternative approach is based on performing numerical integration of the Fock-type integrals on a deformed path on which the integrands are nonoscillatory and rapidly decaying. Comparison of this approach with the previously developed one presented in , which is based on invoking the Cauchy's residue theorem by finding the pole singularities numerically, reveals that the alternative approach is considerably more efficient View full abstract»

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  • Exact Closed-Form Expression of a Sommerfeld Integral for the Impedance Plane Problem

    Publication Year: 2006 , Page(s): 2568 - 2576
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1333 KB) |  | HTML iconHTML  

    A Sommerfeld integral for an impedance half-plane is one of the classical problems in electromagnetic theory. In this paper, the integral is evaluated into two series representations, which are expressed in terms of the exponential integral and the Lommel function, respectively. It is shown that the series expansions absolutely converge for any parameters, such as distance or surface impedance. Then based on the Lommel function expansion, an exact closed-form expression of the integral is formulated. This expression is written in terms of incomplete Weber integrals, which are directly related to incomplete cylindrical functions such as incomplete Lipschitz-Hankel integrals. Additionally, a complete asymptotic series of the integral is obtained based on the exponential integral expansion. With conventional methods such as steepest descent method, it is cumbersome to derive the divergent series. The validity of all the formulations derived in this paper is demonstrated through a comparison with a numerical integration of the integral for various situations View full abstract»

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  • Simulations and Measurements of Wave Propagations in Curved Road Tunnels for Signals From GSM Base Stations

    Publication Year: 2006 , Page(s): 2577 - 2584
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1622 KB) |  | HTML iconHTML  

    This paper presents a ray-tube tracing method to simulate waves propagating in curved road tunnels from base stations for mobile communications. Ray tubes are traced by including multiple reflections in the curved tunnels and diffractions from wedges of the tunnel structures, together with the direct path. To verify this ray-tube tracing approach, field measurements of 900 MHz signals in two curved road tunnels from GSM base stations were performed for comparisons with the ray-tube tracing simulations. By tracing ray tubes reflected and diffracted from the curved structures of the tunnels, the effects of the curvature on wave propagations in large guiding structures can be evaluated. Good agreement between simulations and measurements has been obtained. A parametric study of the influence of the tunnel geometry and the signal frequency on the path loss is also presented by applying this ray-tube tracing method. Curved tunnels for different radii of curvature in the tunnel cross-section and horizontal plane and also lengths of the curved part are compared, together with rectangular tunnels. Simulations of the field distribution over the cross-section of the curved tunnel away from the transmitting antenna are demonstrated as well. The ray-tube tracing program can be applied to determine the deployment of the base-station antennas for improving signal coverage in tunnels, which may have curved structures View full abstract»

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  • A New Class of Miniature Embedded Inverted-F Antennas (IFAs) for 2.4 GHz WLAN Application

    Publication Year: 2006 , Page(s): 2585 - 2592
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (826 KB) |  | HTML iconHTML  

    A new class of miniature printed embedded inverted-F antennas are proposed for operation in the 2.4-2.485 GHz wireless local-area network band. One of the proposed antennas on FR4 substrate (dielectric constant = 4.4) measures 9.2 mm by 4.1 mm and has a bandwidth of 3.5%. The peak gain of this antenna is 1.4 dBi. An overall size reduction of 70% is achieved compared to a conventional inverted-F antenna. Effects of dielectric loss tangent and material conductivity on the bandwidth and efficiency of these antennas are also investigated. Finally, two embedded antenna elements are analyzed to demonstrate the feasibility for a decoupled antenna pair consisting of switched and combining diversity schemes View full abstract»

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  • Analysis and Optimization of Leaky-Wave Radiation at Broadside From a Class of 1-D Periodic Structures

    Publication Year: 2006 , Page(s): 2593 - 2604
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1330 KB) |  | HTML iconHTML  

    Radiation at broadside from leaky waves is studied for one-dimensional periodic structures modeled by means of a transmission line periodically loaded by series or shunt loads. Radiation at broadside occurs via an axially fast spatial harmonic in a neighborhood of the open-stopband frequency; operation in such a frequency range is studied here by means of an approximate asymptotic Bloch analysis of the adopted equivalent network and a simple array-factor calculation of the radiated far field. The condition of equal values for the phase and attenuation constants of the radiating spatial harmonic is shown to give rise to maximum radiation at broadside in the lossless case and to the splitting of a single peak of the radiation pattern at broadside into two distinct peaks in both the lossless and the lossy cases. The 3 dB frequency band for broadside radiation is characterized in terms of the leaky-pole locations in the complex plane and an approximate formula for the antenna bandwidth is provided. Numerical results illustrating these properties are provided, including full-wave simulations of a specific structure through the method of moments View full abstract»

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  • Aperture Coupling and Dipole Excitation in Planar Waveguide Partially Filled With Left-Handed Material

    Publication Year: 2006 , Page(s): 2605 - 2614
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1033 KB) |  | HTML iconHTML  

    We present physical concepts and formulations for a parallel-plate waveguide which is partially filled with stratified right-handed and left-handed media and fed by apertures. Based on an exact analysis, high power transmissions can be obtained if the medium parameters and layer thicknesses are properly chosen. Such a structure is called a super waveguide since the transmitted power is extremely larger than that in a conventional air-filled waveguide. The equivalence principle and stratified medium theory are used to set up the integral equation in terms of the magnetic currents on apertures. We have applied the method of moments to discretize the integral equation and solved it numerically. The impact of such magnetic currents to the high-power transmission and their interaction to the original dipole source are investigated. From numerical results, we notice that the transmission power is not as high as we anticipated if the source is outside the waveguide. If the source is placed inside the waveguide through apertures, however, the super waveguide will be realized View full abstract»

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  • Double-Sided Exponentially Tapered GPR Antenna and Its Transmission Line Feed Structure

    Publication Year: 2006 , Page(s): 2615 - 2623
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (662 KB) |  | HTML iconHTML  

    A double-sided broadband antenna for applications including ground-penetrating radar for detecting buried target is described. When compared with traditional coplanar-strip antennas, a better performance is achieved with a more practical design for construction. The steps in the design procedure are demonstrated herein. In addition, using incremental segments of current elements, a distributed dipole array model is derived and presented for determining S11 in the time domain and for determining the radiation pattern of this antenna. By comparing measured results and HFSS simulations, our straightforward dipole array model of the more complicated antenna structure is justified by the accuracy of the results obtained. Finally, an experimental example is presented to show that this antenna in a GPR system application is effective in detecting even small plastic targets View full abstract»

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  • MEMS-Switched Parasitic-Antenna Array for Radiation Pattern Diversity

    Publication Year: 2006 , Page(s): 2624 - 2631
    Cited by:  Papers (36)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1929 KB) |  | HTML iconHTML  

    A micro-electro-mechanical series (MEMS)-switched parasitic antenna array providing radiation pattern diversity is described. A new modeling method is introduced in order to allow a fast and accurate optimization of the antenna. This method is demonstrated with the design of both passive and active prototypes at 5.6 GHz. The active prototype makes use of stand-alone packaged MEMS switches. Measured return loss and radiation patterns are in good agreement with the design, demonstrating a beam-switching at plusmn25deg View full abstract»

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  • Dual-Band Platform Tolerant Antennas for Radio-Frequency Identification

    Publication Year: 2006 , Page(s): 2632 - 2637
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1149 KB) |  | HTML iconHTML  

    A technique for tuning a single-element planar inverted F-antenna (PIFA) to provide a dual-band operation is introduced. The tuning is possible due to the particular impedance level typical to radio-frequency identification microchips. As the desired impedance level resides near the outer rim of the Smith chart, a single impedance locus may be arranged to pass the input impedance twice resulting in dual-band operation. The tuning of the impedance locus is based on the feed inductance and capacitive coupling at the open end of the patch. In this paper, also a discussion about the principles of platform tolerance of small antennas is provided. A design, circuit model, simulations, and measurement results of dual-band platform tolerant PIFAs are reported and discussed View full abstract»

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  • Design and Testing of Frequency-Selective Surfaces on Silicon Substrates for Submillimeter-Wave Applications

    Publication Year: 2006 , Page(s): 2638 - 2645
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1637 KB) |  | HTML iconHTML  

    A new class of frequency-selective surfaces (FSSs), to be used as quasi-optical filters for harmonic suppression in submillimeter-wave frequency multipliers, is proposed and experimentally verified. The FSSs consist of two-dimensional aperture arrays and are made from microstructured aluminum on electrically thick, high-resistivity silicon substrates. This leads to a very good mechanical stability, reasonably low insertion loss, and permits manufacture of the structure by using standard processes available from the semiconductor industries. This paper presents the design, fabrication, and testing of two sets of prototypes, the former with a passband at 300 GHz and a stopband at 450 GHz and the latter with a passband at 600 GHz and a stopband at 750 GHz. For both frequency ranges, FSSs with rectangular slots and with dogbone-shaped holes have been designed by using the method of moments/boundary integral-resonant mode expansion method. The effect of ohmic and dielectric losses has been determined by using the commercial code HFSS. Several prototypes have been fabricated, and measured by terahertz time-domain spectroscopy and continuous wave measurements, showing high reproducibility of the machining process, insertion loss between 1.0 and 1.6 dB, and stopband attenuation larger than 30 dB. Finally, we demonstrate that the incidence angle can be used as a degree of freedom for fine tuning the stopband, without practically changing the frequency response in the passband View full abstract»

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  • Direct Measurement of Small Antenna Radiation Efficiency by Calorimetric Method

    Publication Year: 2006 , Page(s): 2646 - 2656
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1640 KB) |  | HTML iconHTML  

    A novel method for radiation efficiency measurement of small-size radiators such as mobile phones and other handheld wireless devices is presented. The method is based on the accurate determination of the power which is dissipated in the antenna under test using a calorimetric approach. The principle of the method, some of its variants, and the experimental setup are described. Application of the method is demonstrated for several test objects with different efficiencies. Accuracy is validated by comparison of calorimetric radiation efficiency against numerical estimates and independent measurements using the reflection efficiency method, a generalized variant of the Wheeler cap method, whose basic limitations are briefly discussed. Due to the calorimetric principle employed in the proposed new method, it qualifies equally well as a highly accurate reference method for radiation efficiency measurements and as a low-cost alternative to three-dimensional pattern integration and Wheeler cap type efficiency estimates 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