Showing papers in "Microwave and Optical Technology Letters in 1998"
TL;DR: In this paper, an analytical derivation of a 3D conformal perfectly matched layer (PML) for mesh termination in general orthogonal curvilinear coordinates is presented.
Abstract: We present an analytical derivation of a 3-D conformal perfectly matched layer (PML) for mesh termination in general orthogonal curvilinear coordinates. The derivation is based on the analytic continuation to complex space of the normal coordinate to the mesh termination. The resultant fields in the complex space do not obey Maxwell's equations. However, it is demonstrated that, through simple field transformations, a new set of fields can be introduced so that they obey Maxwell's equations for an anisotropic medium with properly chosen constitutive parameters depending on the local radii of curvature. The formulation presented here recovers, as particular cases, the previously proposed Cartesian, cylindrical, and spherical PMLs. A previously employed anisotropic (quasi-) PML for conformal terminations is shown to be the large radius of curvature approximation of the anisotropic conformal PML derived herein. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 231–236, 1998.
152 citations
TL;DR: The concept of fractional curl operator is introduced in this paper, and as one of its roles, it is briefly shown that the duality principle in electromagnetism for the source-free case can be fractionalized.
Abstract: The concept of fractional curl operator is introduced, and as one of its roles, it is briefly shown that the duality principle in electromagnetism for the source-free case can be fractionalized. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 86–91, 1998.
152 citations
TL;DR: In this article, the authors describe the design and the high performance of a new balanced antipodal Vivaldi antenna for ultra-wideband applications and present the return loss, radiation pattern, antenna gain, and level of cross polarization of this antenna for both simulated and experimental results.
Abstract: This paper describes the design and the high performance of a new balanced antipodal Vivaldi antenna for ultra-wideband applications. The return loss, radiation pattern, antenna gain, and level of cross polarization of this antenna are presented for both simulated and experimental results. The antenna is demonstrated to have greater than decade bandwidth (impedance within 10 dB over 1.3–20 GHz) and low cross polarization (<−17 dB in the broadside direction) over the band. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 286–289, 1998.
117 citations
TL;DR: The slit cut on a microstrip antenna is studied, and a multiport series inductance network is established for analysis, and two slit applications are proposed: to adjust the resonant frequency, and to make a small micro Strip antenna.
Abstract: The slit cut on a microstrip antenna is studied in this paper, and a multiport series inductance network is established for analysis. Based on this study, two slit applications are proposed: to adjust the resonant frequency, and to make a small microstrip antenna. Experiments agree well with the theoretical analysis. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 297–300, 1998.
104 citations
TL;DR: In this paper, a double slot-line-microstrip transition employing a 90° cross over them is presented, where radial stubs at the crossover between the transmission lines, an insertion loss of less than 1.3 dB was measured.
Abstract: This paper presents a double slot-line–microstrip transition employing a 90° cross over them. Using radial stubs at the crossover between the transmission lines, an insertion loss of less than 1.3 dB was measured (0.65 dB per transition) over the 3–15 GHz range. The transition is simulated using a commercial electromagnetic finite-element simulator. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 339–342, 1998.
91 citations
86 citations
TL;DR: In this paper, a 3.4:1 tuning range over a 1-40 V bias range was shown to be achievable with a relative dielectric constant tuning of 3.8:1.
Abstract: Interdigitated capacitors have been fabricated on ferroelectric thin films of Sr0.5Ba0.5TiO3. These devices have been characterized at microwave frequencies from 50 MHz to 20 GHz, and have a 3.4:1 tuning range over a 1–40 V bias range. This is shown to originate from a relative dielectric constant tuning of 3.8:1. The microwave losses exhibited by these capacitors are comparable to those of commercially available semiconductor varactors for frequencies greater than 1 GHz, and should be useful for tunable microwave circuits in some 300 K applications. Published 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 168–171, 1998.
78 citations
TL;DR: In this paper, the adaptive integral method (AIM) is applied to the solution of the combined field integral equation (CFIE) of scattering by a 3D perfect electric conductor (PEC).
Abstract: The adaptive integral method (AIM) is applied to the solution of the combined field integral equation (CFIE) of scattering by a three-dimensional (3-D) perfect electric conductor (PEC). The employment of CFIE eliminates the interior resonance problem suffered by both the electric field integral equation (EFIE) and the magnetic field integral equation (MFIE). Furthermore, it significantly improves the efficiency of AIM by reducing the number of iterations for convergence. It is shown that the memory requirement and computational complexity per iteration of the AIM solution of CFIE are O(N1.5) and O(N1.5log N), respectively, for 3-D PEC surface scattering problems. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 321–328, 1998.
67 citations
TL;DR: In this article, an analytical expression for the electric field intensity in the near region of a vibrating metallic conical probe situated above the surface of a semi-infinite dielectric medium was proposed.
Abstract: A vibrating metallic conical probe has been used in near-field microscopic measurements to obtain optical resolutions much smaller than the wavelength. Numerical simulations of these complex problems have drawn most of the attention in the past. We propose here an analytical expression for the electric field intensity in the near region of a probe situated above the surface of a semi-infinite dielectric medium. It is given as a function of the observation point location, with the cone aperture, the dielectric medium permittivity, and the characteristics of the incident plane wave as parameters. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 120–124, 1998.
51 citations
TL;DR: In this article, a CPW-fed bow-tie slot antenna is presented, and the wide bandwidth can be adjusted by the slot width when the extended angle is zero, while the far field is in the broadside direction and the cross polarization is kept at a low level.
Abstract: A CPW-fed bow-tie slot antenna is presented. Experimental results show that the widest bandwidth can be adjusted by the slot width when the extended angle is zero, while the far field is in the broadside direction and the cross polarization is kept at a low level. The bow-tie slot antenna can obtain at least 36% bandwidth (VSWR<2) with a 20° extended angle. A smaller slot width needs a larger extended angle to reach the widest bandwidth; meanwhile, the far field has a wider 3 dB beamwidth in the H-plane than that using a larger slot width. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 358–360, 1998.
49 citations
TL;DR: The current 2.0.2-IView record in Web of Science Record created on 2006-11-30, modified on 2016-08-08 as discussed by the authors, is the longest existing record.
Abstract: Reference LEMA-ARTICLE-1998-001doi:10.1002/(SICI)1098-2760(19980220)17:3 3.0.CO;2-IView record in Web of Science Record created on 2006-11-30, modified on 2016-08-08
TL;DR: A stable conformal finite-difference time-domain algorithm, that incorporates the backward-weighted averaging scheme to accurately model curved metallic structures, is presented, and the advantage of using the present scheme over the previous one is illustrated.
Abstract: A stable conformal finite-difference time-domain algorithm, that incorporates the backward-weighted averaging scheme to accurately model curved metallic structures, is presented in this paper. The modified approach overcomes the size and shape limitations of the scheme that was proposed previously by the authors, and this improvement is achieved with a little increase in the complexity of the algorithm. The advantage of using the present scheme over the previous one is illustrated by carrying out a comparative study of the canonical problem of a spherical cavity resonator. Further usefulness of the method is exemplified by modeling a gap-coupled circular microstrip patch antenna. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 349–352, 1998.
TL;DR: In this article, the authors present a new and efficient numerical method to calculate the electromagnetic scattering from arbitrarily shaped conducting bodies directly in the time domain, which involves the triangular patch modeling of the arbitrary body in conjunction with the patch basis functions.
Abstract: In this work, we present a new and efficient numerical method to calculate the electromagnetic scattering from arbitrarily shaped conducting bodies directly in the time domain. The solution method is based on the method of moments, and involves the triangular patch modeling of the arbitrary body in conjunction with the patch basis functions. Detailed mathematical steps along with several numerical results are presented to illustrate the efficacy of this approach. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 321–325, 1998.
TL;DR: In this paper, a cavity perturbation technique suitable for measuring magnetic parameters of ferrite materials is discussed, where rod-shaped samples or a ferrite-powder-filled capillary tube are placed at the position of maximum magnetic field in a rectangular waveguide cavity.
Abstract: A cavity perturbation technique suitable for measuring magnetic parameters of ferrite materials is discussed. Rod-shaped samples or a ferrite-powder-filled capillary tube are placed at the position of maximum magnetic field in a rectangular waveguide cavity. From the shift in the resonant frequency and the Q-value, the complex permeability of the material can be evaluated. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 241–243, 1998.
TL;DR: In this paper, the authors applied the finite element analysis of electromagnetic scattering problems to the radar cross section (RCS) problem and showed that the FEM in conjunction with waveform evaluation (AWE) can predict the RCS over a frequency band whose bandwidth is highly dependent on the size of the scatterer, and a simple binary search algorithm was described to apply AWE at multiple frequency points to generate an accurate solution.
Abstract: The method of asymptotic waveform evaluation (AWE) is applied to the finite-element analysis of electromagnetic scattering problems. The finite-element mesh is terminated using a perfectly matched layer (PML), an absorbing boundary condition (ABC), or their combination. It is shown that the finite-element method (FEM) in conjunction with AWE can predict the radar cross section (RCS) over a frequency band whose bandwidth is highly dependent on the size of the scatterer. For a given order of AWE, the bandwidth decreases when the size of the scatterer increases. A simple binary search algorithm is described to apply AWE at multiple frequency points to generate an accurate solution over a specified frequency band. Numerical examples are given to demonstrate the performance of AWE in the RCS calculation by the FEM. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 7–12, 1998.
TL;DR: An implicit version of the time-domain integral equation is presented for the analysis of electromagnetic scattering from wire structures that is unconditionally stable over the explicit version.
Abstract: An implicit version of the time-domain integral equation is presented for the analysis of electromagnetic scattering from wire structures. The advantage of the implicit form is that for large values of the time step, the method is unconditionally stable over the explicit version. Numerical results are presented to illustrate the efficacy of this approach. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 66–69, 1998.
TL;DR: In this paper, an incremental Maxwell Garnett (IMG) formalism is developed for homogenizing particulate composite media, which is phenomenologically valid even for dense composite media because it homogenizes incrementally over a succession of several intermediate dilute composite media.
Abstract: Based on the Maxwell Garnett (MG) formalism for homogenizing particulate composite media, an incremental MG (IMG) formalism is developed. Whereas the MG formalism is suitable for dilute composite media, the IMG formalism is phenomenologically valid even for dense composite media because it homogenizes incrementally over a succession of several intermediate dilute composite media. IMG algorithms are presented for the simple dielectric-in-dielectric, as well as the complicated bianisotropic-in-bianisotropic composite media. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 276–279, 1998.
TL;DR: In this paper, an alternatie method of determining the wire resistance is presented, which is significantly simpler than the Bessel function approach, easier toisualize, and not reliant on approximations when determining the solution.
Abstract: At high frequencies, the current distribution across a circular wire is modified by the skin effect, causing the greatest current density to be near the surface of the wire. One common method of calculating the wire resistance inoles determining complex Bessel func- tions, the solution of which is prone to approximations as the skin depth becomes less than about one tenth the wire radius. An alternatie method of determining this resistance is presented which is significantly simpler than the Bessel function approach, easier toisualize, and not reliant on approximations when determining the solution. This approach is based on determining the width of an annulus which carriers the equialent current to the full wire. Results are presented which confirm the accuracy of the equialent annulus method. Q 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 84)87, 1998.
TL;DR: In this paper, a simple technique for obtaining circular polarization (CP) radiation of a single-feed microstrip antenna is demonstrated, which is achieved by insetting a single slit to the boundary of the microstrip patch, and placing a single feed along an axis 45° to the one containing the slit.
Abstract: A new and simple technique for obtaining circular polarization (CP) radiation of a single-feed microstrip antenna is demonstrated. This CP design is achieved by insetting a single slit to the boundary of the microstrip patch, and placing a single feed along an axis 45° to the one containing the slit. Applications of this CP design method to square and circular microstrip antennas have been implemented. Typical experimental results are presented and discussed. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 306–308, 1998.
TL;DR: This poster presents a probabilistic procedure to characterize the response of the immune system to chemotherapy-like injuries to treat central giant cell granuloma.
Abstract: Reference LEMA-ARTICLE-1998-006View record in Web of Science Record created on 2006-11-30, modified on 2016-08-08
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TL;DR: In this paper, a comparison of the calculated pure bend loss of S-bends for a typical silica-based waveguide operating at a wavelength of 1550 nm is presented.
Abstract: The performance of S-bends, which are used for connecting waveguides offset with respect to each other, is very important in integrated-optic waveguide circuits. Several approaches for the design of S-bends have been reported in the literature. These include, in particular, designs based on simple sinusoidal curves as well as relatively complicated, but more general, polynomial curves. This paper reports a comparison of the calculated pure bend loss of such S-bends for a typical silica-based waveguide operating at a wavelength of 1550 nm. It is shown that the simple cosine S-bands yield a performance which is close to that obtained from the general polynomial curve-based S-bends. Design curves are also presented for these two types of S-bends. The calculations are based on the analytical expression for bend loss proposed by Marcuse. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 289–292, 1998.
TL;DR: In this article, a unified dielectric loss model based upon the single-layer reduction (SLR) formulation is presented for the determination of dielectral loss of a multilayer lossy microstrip line with and without the top shield.
Abstract: A unified dielectric loss model based upon the single-layer reduction (SLR) formulation is presented for the determination of dielectric loss of a multilayer lossy microstrip line with and without the top shield. The model has accuracy within 0.05 dB/cm or 3% against the field-theoretic results from several sources. The computational efficiency of this model does not depend on the number of dielectric layers, and the model is valid up to the millimeter-wave range. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 368–370, 1998.
TL;DR: In this paper, a vortex shedding flowmeter with a fiber-optic Fabry-Perot interferometer (FFPI) was used to measure the liquid flow velocity in a pipe.
Abstract: A new design of a vortex-shedding flowmeter with a fiber-optic Fabry–Perot interferometer (FFPI) as the sensing element is described here to measure the liquid flow velocity in a pipe. The flow velocity is determined by measuring the frequency at which the reflected optical power from the FFPI is modulated. Experimentally, a linear dependence of optical modulation frequency on flow velocity is observed over the range from 0.14 to 3.0 m/s, in good agreement with theoretical prediction. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 209–211, 1998.