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Antennas and Propagation Society International Symposium, 1998. IEEE

Date 21-26 June 1998

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  • IEEE Antennas and Propagation Society International Symposium 1998 [front matter]

    Page(s): i - 1791
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    Freely Available from IEEE
  • Application of the recursive convolution technique to modeling lumped circuit elements in FDTD simulations

    Page(s): 1792 - 1795 vol.4
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    This paper presents a simple approach for extending the basic Yee FDTD algorithm to allow for modeling combinations of resistors, capacitors and inductors as lumped elements. This approach uses the recursive convolution (RC) technique previously applied in FDTD for simulating pulse propagation in frequency dependent dielectric media. In the application presented, the potential across the lumped load is updated by a recursive evaluation of the convolution of the current with the inverse Fourier transform of the impedance. This approach can be used whenever the impedance can be approximated over the frequency range of interest with functions which have inverse Fourier transforms containing the exponential time dependence required by the RC method. A parallel LCR satisfies this requirement, and any number of parallel LCR circuits in series can be modeled as a lumped load located at a single FDTD cell location. The formulation in this paper also permits a voltage or current source to be included within the lumped element. View full abstract»

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  • Application of multigrid FDTD to the simulation and design of microwave processing system

    Page(s): 1796 - 1799 vol.4
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    The multigrid finite-difference time-domain (FDTD) method is more efficient and accurate in characterizing electrically large and complex electromagnetic devices and structures. Detailed results of electromagnetic fields distribution in critical areas of interest can be obtained, thus accurately identifying hot spots and potential design faults. We present results illustrating the use of multigrid FDTD for the simulation and design of microwave processing systems. A realistic microwave dryer is simulated. New designs to improve the uniformity of the power distribution pattern in the ware samples are presented. It is shown that by using a slotted waveguide with slots varying in size along the waveguide, the absorption and the power uniformity can be significantly improved. The dependence of the power distribution pattern on the number of samples and a comparison between the slotted waveguide feed and the mode stirrer design is presented. View full abstract»

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  • 3-D FDTD image analysis in transmission illumination mode of scanning near-field optical microscopy

    Page(s): 1800 - 1803 vol.4
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    Tunnel scanning near-field optical microscopy (tunnel SNOM or TNOM) detects not only the regularly transmitted waves but also radiation coupled via evanescent waves to the classically forbidden directions (angles larger than the angle of total internal reflection). Forbidden light can, in general, provide images with higher contrast and resolution than those of allowed-light images. However, the full use of the forbidden-light information requires better understanding of the SNOM imaging process. While the multiple multipole method (MMP) has been proven to be useful for 2-D modeling of SNOM, it seems to be unsuitable for more realistic 3-D simulations due to difficulties in dealing with complicated inhomogeneous material geometries. View full abstract»

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  • General PML constitutive tensors to match arbitrary bianisotropic and dispersive linear media

    Page(s): 1804 - 1807 vol.4
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    A formulation is presented to extend the perfectly matched layer (PML) to arbitrary linear media presenting bianisotropy and/or dispersion. It is shown that, in these cases, a Maxwellian PML formulation is possible such that the PML can be realized as a medium with suitable defined bianisotropic constitutive tensors. A limitation of this approach is that it does not apply to nonlinear media. View full abstract»

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  • Modelling radiation from complex structures using a hybrid FDTD-BIE technique

    Page(s): 1808 - 1811 vol.4
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    A new hybrid finite-difference time-domain-boundary integral equation technique is proposed to model the radiation of complex three-dimensional structures involving current sources in the presence of metallic and dielectric objects. The simulation geometry is decomposed into several subregions. For homogeneous bounded and unbounded regions the 3D boundary integral technique is used. For each inhomogeneous subregion an interaction matrix is calculated at multiple frequencies using FDTD. Finally the different interaction matrices and source vectors are assembled into one global matrix equation by invoking continuity of the tangential electric and magnetic fields at all the interfaces between the subregions. An example is given to validate the new method. View full abstract»

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  • An efficient FDTD algorithm with isotropic numerical dispersion on an overlapped lattice

    Page(s): 1812 - 1815 vol.4
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    We develop a second order algorithm for electromagnetics on an overlapped discrete lattice and compare the results with the standard Yee algorithm (1966). The algorithm maintains the locality and simplicity of the Yee algorithm while improving on errors introduced by numerical dispersion. In addition, the algorithm is stable for time steps larger than those required for the Yee algorithm. For a given physical problem and a given error bound, the algorithm is shown to require approximately half the memory of the Yee algorithm and only one half to one third the computation time due to its improved isotropic numerical dispersion and increased time step. View full abstract»

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  • Analytic analysis of the CP-FDTD and C-FDTD methods for offset planar boundaries

    Page(s): 1816 - 1819 vol.4
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    A locally-conformal FDTD scheme, known as the conformal FDTD (C-FDTD) method, has been introduced previously to model perfect electric conductors (PECs) that do not align with the grill. This scheme is arguably the simplest conformal scheme to date since the electric field update equations are unchanged and there are only minor changes made to the update equations for magnetic field nodes adjacent to the PEC boundary. Unlike for the contour path FDTD (CP-FDTD) method, no nearest-neighbour approximation is used. We derive the reflection coefficient for the C-FDTD and CP-FDTD methods for TM/sub x/, illumination of planar boundaries that are aligned with, but offset from, the grid. A similar analysis holds for TE/sub x/, illumination. View full abstract»

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  • Modeling interface discontinuities and boundary conditions for a dispersion-optimized finite-difference time-domain method

    Page(s): 1820 - 1823 vol.4
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    This article describes extensions to a dispersion-optimized finite-difference time-domain (FDTD) method for analysing long-range propagation problems. We examine the handling of boundary condition problems produced by inhomogeneous materials and FDTD grid truncation. Truncation of the simulation grid is accomplished by using a uniaxial perfectly matched layer absorber coupled with the dispersion-optimized fourth order differences. Material discontinuities require a modification of the higher order FDTD updates at the material interfaces; the exact modifications can be derived by enforcing continuity of multiple derivatives at the material interface. View full abstract»

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  • Fast evaluation of the Sommerfeld integrals for Green's functions of open microstrip structures

    Page(s): 1826 - 1829 vol.4
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    A very fast and accurate method, called the fast Hankel transform (FHT), is employed to evaluate the Sommerfeld integrals for calculating spatial-domain Green's functions of open microstrip structures. The robustness of this method is demonstrated by comparing the results with those obtained by direct numerical integration for distances up to ten free space wavelengths over a broad frequency band. View full abstract»

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  • Scattering from arbitrarily shaped microstrip patch antennas using the theory of characteristic modes

    Page(s): 1830 - 1833 vol.4
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    A full-wave MoM solution to the problem of plane wave scattering by an arbitrarily shaped patch printed on a dielectric slab, using the theory of characteristic modes, is presented. Computed current distributions for the microstrip patch are presented. The method proposed seems promising for the exact analysis of arrays of microstrip antennas reducing the number of unknowns and the corresponding computational effort. View full abstract»

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  • Use of dynamic modes in the analysis of printed antennas and arrays

    Page(s): 1834 - 1837 vol.4
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    A new class of entire-domain basis functions, particularly suitable for the full-wave analysis of printed arrays with elements of general shape is presented. These functions, called "dynamic modes", are obtained from the response of a single antenna and include the effect of the coupling to the feed network. Application to the analysis of a three element array shows that they lead to a numerically efficient compression of the impedance matrix. View full abstract»

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  • Network parameters of printed antennas from the MoM solution

    Page(s): 1838 - 1841 vol.4
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    A technique for the determination of the S-parameters of a printed multi-port structure is presented. The first step is a least-squares extraction of the dominant TEM current on a microstrip line, and its separation into forward and reflected waves. This is then used to incorporate lumped, arbitrary-load conditions into the full-wave solution. By the application of this method at the different ports, the entries of the scattering matrix are obtained, with respect to matched-port conditions that are imposed numerically. Results are presented for a two-port structure. View full abstract»

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  • Fast noniterative steepest descent path algorithm for planar and quasi-planar patch geometries

    Page(s): 1842 - 1845 vol.4
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    The motivation in developing fast direct noniterative algorithms is first considered. The combination of the recursive T-matrix algorithms and the steepest descent path formulation is then discussed. View full abstract»

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  • Development of wide-band push-pull amplifiers using coplanar waveguide and slot line

    Page(s): 1846 - 1849 vol.4
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    We report the development of completely uniplanar wide-band balanced push-pull FET amplifiers using slot line and coplanar waveguide. The amplifiers employ broadband uniplanar baluns to achieve the push-pull function over a wide bandwidth. One amplifier, designed in the unconditionally stable region, exhibits a gain of 3.5 to 5 dB over the frequency range of 5.4 to 10 GHz. The other amplifier was designed in the potentially unstable range and achieved a high gain between 10 and 11 dB from 2 to 4 GHz. These results show the feasibility of the push-pull FET amplifier configuration using uniplanar technology for microwave and millimeter-wave integrated circuits and systems. View full abstract»

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  • Distortion of pulses on a terminated microstrip line of finite length

    Page(s): 1850 - 1853 vol.4
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    This paper reports an investigation of the distortion of pulses propagating on a terminated microstrip line of finite length due to the line's dispersion. The Fourier transform and its inverse are used to compute the transient signals. The dispersion of the microstrip line, needed in the analysis, is calculated using the spectral-domain method. Results are presented for finite-length microstrip lines terminated by a resistor, an open circuit, and an inductor, showing clear distortions of the propagating signals. View full abstract»

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  • Voltage, efficiency calculation and measurement of low power rectenna rectifying circuit

    Page(s): 1854 - 1857 vol.4
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    In this paper, we present zero-bias Schottky diode and rectifier circuit models for a low power (/spl les/ 0 dBm) rectenna rectifying circuit. These models rely primarily on data obtained from the diode characteristic curve measurement. The zero-bias Schottky diode model provides diode parameters at the desired output DC current level to be matched with the antenna so that optimum power transfer from the antenna to the diode takes place. The rectifier circuit model provides an equivalent circuit model for the rectenna rectifying circuit to calculate RF to DC conversion efficiency at the desired output DC current level. View full abstract»

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  • Asymmetric microstrip gaps mounted inside a ground cylindrical surface

    Page(s): 1858 - 1861 vol.4
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    Accurate characterization of cylindrical microstrip gap discontinuities is crucial for the design of the circuits including them. In the past, considerable work has been done analyzing a variety of microstrip gap discontinuities on planar and curved substrates. However, the related studies on the asymmetric gap discontinuities mounted inside a grounded cylindrical substrate are still scant in the open literature. In this paper, a full-wave spectral-domain approach is used to analyze such asymmetric gap structures. To obtain a numerical solution, the entire-domain sinusoidal functions are used to represent the traveling-wave mode of the strip current and piecewise sinusoidal (PWS) functions are added in the vicinity of the gap to model the current disturbance due to the structure discontinuity. The dispersion characteristics of the frequency-dependent S-parameters and the gap equivalent capacitances for various microstrip width ratios are presented and discussed. View full abstract»

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  • Full-wave analysis of screened cylindrical microstrip and slot lines-a Riemann-Hilbert method model

    Page(s): 1862 - 1865 vol.4
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    The present paper is focused on the wave characteristics of screened cylindrical strip and slot lines (SCMSL and SCSIL) analyzed with the rigorous electrodynamical Riemann-Hilbert method. The latter provides an adequate numerical-analytical approach whose solution involves no limitation on the structure geometrical parameters. The present work is addressed to the dispersion characteristics of SCMSL, with various dielectric fillings and the effect of the transformation of the SCSIL waves into SCMSL ones as the slot is widened. An approximate analytical formula evaluating the phase constant coefficient of the principal wave of the SCMSL has been specially obtained. View full abstract»

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  • Electromagnetic ground-wave field of vertical antennas

    Page(s): 1868 - 1871 vol.4
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    Communication between the shore and a ship and between ships makes use of frequencies from 1 to 30 MHz. Distances up to 10000 km are involved. The analysis presented in this paper provides new simple formulas for the ground wave along the surface of the sea. These include not only the range in which the surface of the sea is well approximated by a plane but also the range where accurate account must be taken of the curvature of the spherical earth. Of practical significance is the fact that when f/spl ges/10 MHz, the amplitude of an outgoing wave decreases much more rapidly than when f<10 MHz. View full abstract»

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  • Analysis of dual polarisation propagation data for tropospheric channel study

    Page(s): 1872 - 1875 vol.4
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    The measurement of the tropospheric Ku-band transmission matrix is a very sensitive method to study the anisotropic behaviour of the propagation medium. Measured parameters are, alike radar measurements, integrated quantities of difficult interpretation due to the wave interaction with a quite variable propagation conditions. The main techniques used to infer channel structure from measured time series data is described. Examples using real data events are given. View full abstract»

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  • Wave propagation in curved road tunnels

    Page(s): 1876 - 1879 vol.4
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    In the early seventies much work was done in order to understand the propagation loss of UHF waves in rectangular mine tunnels, using either waveguide methods or image techniques based on geometrical optics (GO). A simple and accurate model is needed for planning the deployment of mobile phone networks. The method presented a simple GO extension to the standard hybrid waveguide solution. View full abstract»

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  • An automated UTD approach for modeling wave propagation over hilly terrain based on digital maps

    Page(s): 1880 - 1883 vol.4
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    Simulation methods for predicting wave propagation over irregular terrain in the frequency ranges of VHF, UHF, and microwaves have been studied by many investigators. Those methods were applied to evaluate propagation path losses, coverage predictions, spectrum management, low altitude radar performance, microwave landing systems, etc. UTD ray models with digital terrain data simplified to two-dimensional (2-D) piecewise-linear profiles of wedges have been employed successfully to site-specifically determine terrain wave propagation. This article presents an automated method to simplify raw digital hilly terrain profiles into 2-D straight wedges and trapezoids (two consecutive wedges) based directly on the variations of the terrain elevations along a given vertical Tx-Rx profile. Also, a UTD ray approach for calculating all the forward diffraction from those piecewise-linear 2-D structures is proposed. View full abstract»

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  • Characterization of the wave propagation in the ionospheric channel by the scattering function

    Page(s): 1884 - 1887 vol.4
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    We present a new method of calculating the effect of non-stationarities on ionospheric propagation. By adding one extra equation to Haselgrove's (1955) system, the delay-Doppler function can be readily calculated, and the dynamic behaviour of the ionosphere can be taken into account in a very simple way. These equations have been applied to an ionospheric electron density model, in order to compute the deterministic part of the scattering function, in the presence or in the absence of the horizontal gradients (skeletal part). View full abstract»

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  • Comparison of the current methods for coverage area prediction for communication in the HF band

    Page(s): 1888 - 1891 vol.4
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    A comparative study of the commonly used methods for the prediction of the coverage area due to a transmitter operating at the HF hand is presented. Those statistical model-based tools are Ionospheric Communication analysis and Prediction Program; IONCAP, Ionospheric Communication Enhanced Profile Analysis and Circuit Prediction Program; ICEPAC, Voice of America's VOACAP and ITU's REC 533, and those are illustrated by computing the coverage area of a typical transmitter located at Oxford, England operating at 13.399 MHz (HF band I). Those results are compared with the experimental data measured at Istanbul, Turkey for a transmitter located at Oxford, England. Finally, the same problem is analyzed by the ray-tracing technique using the experimental data. The advantages and the disadvantages of the methods are discussed. View full abstract»

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