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Finite-difference Time-domain (finite-difference + time-domain)

Distribution by Scientific Domains
Engineering91%
Medical Sciences8%

Terms modified by Finite-difference Time-domain

  • finite-difference time-domain method
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    Selected Abstracts

    Fabrication of a novel micron scale Y-structure-based chiral metamaterial: Simulation and experimental analysis of its chiral and negative index properties in the terahertz and microwave regimes

    MICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2007
    Nantakan Wongkasem
    Abstract In this report, we describe the fabrication of a chiral metamaterial based on a periodic array of Y-shaped Al structures on a dielectric Mylar substrate. The unit cell dimensions of the Y-structure are ,100 ,m on a side with 8 ,m linewidths. The fabricated Y-structure elements are characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative elemental analyses were carried out on both the Y-structure, comprised of Al and its oxide, as well as adjacent regions of the underlying mylar substrate using the energy dispersive X-ray spectroscopy (EDS) capability of the SEM. Finite-Difference Time-Domain (FDTD) calculations of the negative index of refraction for a 3D wedge of multiple layers of the 2D metamaterials showed that these metamaterials possess double negative (,,,,,) electromagnetic bulk properties at THz frequencies. The same negative index of refraction was determined for a wedge comprised of appropriately scaled larger Y-structures simulated in the microwave region. This double negative property was confirmed experimentally by microwave measurements on a 3D wedge comprised of stacked and registered Y-structure sheets. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source]

    On the development of efficient FDTD-PML formulations for general dispersive media

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2008
    Konstantinos P. Prokopidis
    Abstract A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to terminate the finite-difference time-domain (FDTD) algorithm for general dispersive and negative index materials is presented. The proposed formulation also adopts the complex frequency-shifted (CFS) approach, involves simple FDTD expressions and avoids complex arithmetic. Several FDTD-PML simulations with different parameters are conducted for the termination of various dispersive media validating the stability, accuracy and effectiveness of the schemes and indicating the advantage of the CFS-PML. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Multi-region ADI DD-FDTD algorithm for the analysis of three-dimensional sparse multi-objects scattering problem

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1-2 2008
    Feng Xu
    In this paper, a multi-region domain decomposition finite-difference time-domain (DD-FDTD) algorithm is proposed and developed for the analysis of multiple-objects electromagnetic (EM) problems. A significant number of mesh nodes between objects are removed since only local meshes are generated for each object. All the separated sub-domains are interconnected by the use of a 3-D time-domain Green's function. The coupling between objects can be regarded as the equivalent spherical wave irradiations. Incident signals of the equivalent spherical waves are expressed as a spherical wave input field array according to the Huygens principle. The near-field to far-field transformation is introduced to obtain the equivalent spherical wave. Moreover, the alternating direction implicit FDTD (ADI-FDTD) scheme is applied to overcome the limit of the stability condition and increase the speed of the simulation. The new algorithm has been demonstrated and applied to solve typical 3-D multi-objects EM scattering problems. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Probe-fed microstrip antennas loaded with very high-permittivity ceramics

    INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2006
    Y. Hwang
    Abstract This article reports the feasibility study of miniaturizing probe-fed microstrip patch antennas by dielectric loading. The loading materials are barium tetratitanate ceramics of very high dielectric constant (,r = 38, 80). It is shown that, simply through loading, the antenna sizes are greatly reduced; however, the antenna performances are deteriorated. For instance, the antenna gain becomes lower. Then enhancement of the antenna performances follows. A substrate,superstrate structure is used to recover the gain. Both the experiments and the finite-difference time-domain (FDTD) simulations demonstrate that the gain and impedance bandwidth can be retrieved such that they are comparable to those of conventional microstrip antennas loaded with low permittivity materials (,r < 3). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source]

    Flow cytometry with gold nanoparticles and their clusters as scattering contrast agents: FDTD simulation of light,cell interaction

    JOURNAL OF BIOPHOTONICS, Issue 8-9 2009
    Stoyan Tanev
    Abstract The formulation of the finite-difference time-domain (FDTD) approach is presented in the framework of its potential applications to in-vivo flow cytometry based on light scattering. The consideration is focused on comparison of light scattering by a single biological cell alone in controlled refractive-index matching conditions and by cells labeled by gold nanoparticles. The optical schematics including phase contrast (OPCM) microscopy as a prospective modality for in-vivo flow cytometry is also analyzed. The validation of the FDTD approach for the simulation of flow cytometry may open up a new avenue in the development of advanced cytometric techniques based on scattering effects from nanoscale targets. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    An improved formalism for the Crank-Nicolson finite-difference time-domain by conformal mapping method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009
    Yang Yang
    Abstract In this article, a three-dimensional (3-D) Crank-Nicolson finite-difference time-domain (CN-FDTD) method combined with conformal mapping method is used to analyze the cavities with curved surface. The improved formalism in the CN-FDTD is described and both time-domain waveforms and resonant frequencies are presented. The numerical simulations of the typical examples show that the time step with this CN-FDTD method is 10 times larger than the Courant-Friedrich-Levy condition without the large loss of accuracy. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2378,2382, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24613 [source]

    Analysis of planar microwave circuits with lumped-elements by CN-FDTD

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009
    Wanchun Tang
    Abstract A three-dimensional implementation of the lumped-element by Crank-Nicolson finite-difference time-domain (CN-FDTD) algorithm has been presented in this article. Several examples of planar microwave circuits with lumped resistor, capacitor, and/or inductor are simulated and compared with traditional finite-difference time-domain method and measurements. The accuracy of CN-FDTD implementation for lumped elements in this article has been verified. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 113,116, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23969 [source]

    Application of the preconditioned GMRES to the Crank-Nicolson finite-difference time-domain algorithm for 3D full-wave analysis of planar circuits

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2008
    Y. Yang
    Abstract The increase of the time step size significantly deteriorates the property of the coefficient matrix generated from the Crank-Nicolson finite-difference time-domain (CN-FDTD) method. As a result, the convergence of classical iterative methods, such as generalized minimal residual method (GMRES) would be substantially slowed down. To address this issue, this article mainly concerns efficient computation of this large sparse linear equations using preconditioned generalized minimal residual (PGMRES) method. Some typical preconditioning techniques, such as the Jacobi preconditioner, the sparse approximate inverse (SAI) preconditioner, and the symmetric successive over-relaxation (SSOR) preconditioner, are introduced to accelerate the convergence of the GMRES iterative method. Numerical simulation shows that the SSOR preconditioned GMRES method can reach convergence five times faster than GMRES for some typical structures. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1458,1463, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23396 [source]

    Analysis of frequency division in microstrip circuits by using the FDTD method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008
    Oscar González
    Abstract The accurate time-domain simulation of the nonlinear dynamics of circuits containing distributed elements is of great interest. Specially at high frequencies, it is essential to consider phenomena, such as crosstalk, packaging effects, and electromagnetic interaction between active and passive elements. These effects are mainly due to the distribute components of the circuit. Therefore, the accuracy in the instability or oscillation analysis of nonlinear circuits is often limited by the models used for such elements. Commercial simulators based on the equivalent-circuit approach hardly take into account the mentioned effects. In this work, the finite-difference time-domain (FDTD) method is applied to the nonlinear simulation of a diode-based microstrip circuit exhibiting a parametric frequency division by two. The FDTD method rigorously solves Maxwell's curl equations in the time domain providing a full-wave characterization of the distributed elements of the circuit. In the example considered, a relatively low operating frequency has been selected to allow a reliable comparison between the results obtained by the proposed technique and those provided by a circuit-based commercial simulator. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1300,1302, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23352 [source]

    Analysis of electromagnetic band-gap waveguide structures using body-of-revolution finite-difference time-domain method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007
    Ming-Sze Tong
    Abstract Study of electromagnetic band-gap (EBG) structures has become a hot topic in computational electromagnetics. In this article, some EBG structures integrated inside a circular waveguide are studied. They are formed by a series of air-gaps within a circular dielectric-filled waveguide. A body-of-revolution finite-difference time-domain (BOR-FDTD) method is adopted for analysis of such waveguide structures, due to their axial symmetric properties. The opening ends of the waveguide are treated as a matched load using an unsplit perfectly matched layer technique. Excitations on a waveguide in BOR-FDTD are demonstrated. Numerical results of various air-gap lengths with respect to the period of separation are given, showing an interesting tendency of EBG behavior. A chirping-and-tapering technique is applied on the EBG pattern to improve the overall performance. The proposed EBG structures may be applied into antenna structures or other system for unwanted signal suppression. Results show that the BOR-FDTD offers a good alternative in analyzing axial symmetric configurations, as it offers enormous savings in computational time and memory comparing with a general 3D-FDTD algorithm. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2201,2206, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22668 [source]

    Calculations of return loss of bonding wires fabricated on a test board by FDTD method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2007
    Hsing-Yi Chen
    Abstract Return losses of bonding wires fabricated on a test board for RF and microwave circuit applications are studied by the finite-difference time-domain (FDTD) method. Simulation results of return losses obtained by the FDTD method are presented and compared with those obtained by the HFSS software and measurements at frequencies of 0.04,6 GHz. It is found that simulation results calculated by the FDTD method make a good agreement with those obtained by the HFSS software. Results of the FDTD method are also further validated by the measurement data. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1603,1606, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22546 [source]

    Application of the high-order symplectic FDTD scheme to the curved three-dimensional perfectly conducting objects

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007
    Wei Sha
    Abstract A high-order symplectic finite-difference time-domain (SFDTD) scheme using the diagonal split-cell model is presented to analyze electromagnetic scattering of the curved three-dimensional perfectly conducting objects. On the one hand, for the undistorted cells, the fourth-order accurate spatial difference is employed. On the other hand, for the completely distorted cells, the treatment of the curved surfaces is based on the diagonal split-cell model. Finally, for the partially distorted cells, the interpolation strategy is proposed to keep the field components continuous. The numerical experiments suggest that the diagonal SFDTD scheme can obtain more accurate results than both the staircased SFDTD scheme and the traditional diagonal FDTD method. Furthermore, in view of the high numerical stability, the improved symplectic scheme does not need to decrease time increment to comply with the stability criterion. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 931,934, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22306 [source]

    Calculation of antenna array far field impulse response using the finite-difference time-domain method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006
    Chen Wu
    Abstract The waveform in the radiation field of a radar antenna can be obtained by using the convolution of the transmitted signal and the antenna far-field impulse response (AFFIR). In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the AFFIR of an X-band 54-element waveguide slot array at different radiation angles using the excitation of a wideband Gaussian pulse. To demonstrate the usage of the far-field impulse response, the waveforms in the radiation field of a narrowband Gaussian pulse are calculated at three different radiation angles by the convolution of the pulse and the waveguide slot-array AFFIR. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 424,430, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21370 [source]

    Planar inverted-F antennas on implantable medical devices: Meandered type versus spiral type

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006
    Jaehoon Kim
    Abstract Based on a planar inverted-F antenna (PIFA) configuration, two different shaped (meandered and spiral) antennas are designed using finite-difference time-domain (FDTD) simulations and measurement results. The antennas are installed on an implantable medical device in a biological-tissue simulating model. The impedance-matching and radiation characteristics of two PIFAs are compared in order to observe which shape is more appropriate for wireless communication links of implantable medical devices. Additionally, the effects of the human skin's thickness on the antennas are studied in order to consider medical devices which are implanted in various subcutaneous tissues. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 567,572, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21409 [source]

    Modification to convolution CFS-PML for the ADI-FDTD method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2006
    Linnian Wang
    Abstract A new implementation of perfectly matched layer (PML) using the recursive-convolution technique is introduced for an alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method. Based on a "complex frequency-shifted (CFS)" scaling function, this PML boundary condition is highly effective at absorbing low-frequency evanescent waves. The numerical results show that, compared with its previously suggested analogue, the new method improves the reflection error by 30 dB for large time-step sizes. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 261,265, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21322 [source]

    A pulsed confocal microwave technique for the detection of dielectric contrast of breast tissue

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2005
    G. Bindu
    Abstract Confocal microwave technology is explored as a screening tool to detect regions of dielectric contrast in breast tissue. When exposed to microwaves, malignant breast tissue exhibits electrical properties that are significantly different from that of healthy breast tissue. In vitro studies of normal and cancerous samples of breast tissue are performed using a prototype of confocal microwave imaging. Experimentally obtained time-domain results are substantiated by finite-difference time-domain (FDTD) analysis. Dielectric permittivities of the samples are estimated from the experimentally obtained time-domain results and are validated by subjecting the samples to dielectric studies using a cavity-perturbation technique. The results are compared with the dielectric parameters of in vitro breast tissue data available in literature. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 209,212, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21125 [source]

    Implicit nonstaggered finite-difference time-domain method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005
    Shumin Wang
    Abstract A new, unconditionally stable, implicit nonstaggered finite-difference time-domain (INS-FDTD) method is introduced. This method is more efficient than the (unconditionally stable) finite-element time-domain (FETD) method with brick elements because the number of nonzero elements in the system matrix is reduced. A numerical-dispersion analysis is provided as well. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 317,319, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20809 [source]

    A K-band inverted microstripline-fed linear tapered slot antenna and its 16-element E-plane array

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2005
    Chen Wu
    Abstract An inverted microstripline-fed linear tapered slot antenna element and a design of its 16-element E-plane array are presented in this paper. The element is designed using the finite-difference time-domain (FDTD) method. The calculated results show that it has a wide-impedance bandwidth in the K-band. To investigate the E-plane array, the return loss at each element input port, the couplings among elements, and the array's radiation patterns are obtained using the FDTD method. Using a unique three-piece assembled structure, the array is fabricated and tested experimentally. The measured results show that it has a wide bandwidth and antenna efficiency. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 241,246, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20784 [source]

    Full-wave FDTD design and analysis of wideband microstrip-to-waveguide transitions

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2003
    Cŕndid Reig
    Abstract Wideband transitions are designed and analysed by using two different approaches of the finite-difference time-domain (FDTD) method, in combination with the theory of nonuniform transmission lines. These transitions consist of a ridged waveguide-based taper between a shielded microstrip and a standard X-band rectangular waveguide. In the first step, a full-wave 2D-FDTD scheme is used to calculate the dispersion characteristics, as well as the geometry dependence of the impedance in the double ridged waveguide. Once these design curves have been obtained, the stepped transmission line transformer theory is used to design the tapers. In a former step, the nonuniform 3D-FDTD technique is applied, the transitions are simulated and the method is validated. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 317,320, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11048 [source]

    Wideband finite-difference,time-domain beam propagation method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2002
    J. J. Lim
    Abstract A wide-band finite-difference,time-domain beam propagation method (FD TD-BPM) based on Padé approximants is introduced to improve the bandwidth of the conventional TD-BPM. Numerical dispersion relations for the TD-BPM are derived to demonstrate the increase in bandwidth of the wide-band TD-BPM. The effects of the spatial and time step sizes on the numerical dispersion are also investigated. It is shown that the wide-band TD-BPM is less sensitive to the choice of spatial step size and allows a larger time step size to be used compared to the finite-difference time-domain (FD-TD) method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 243,247, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10428 [source]

    Analysis of interconnect lines using the finite-difference time-domain (FDTD) method

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2002
    Nader Farahat
    Abstract In this Letter the coupling effect (cross talk) in parallel microstrip interconnects is analyzed with the use of the finite-difference,time-domain (FDTD) method. The interconnects are terminated either by lumped elements or by a perfectly matched layer (PML), and the results obtained from these two methods are compared. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 6,9, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10356 [source]

    Infrared microstrip dipole antennas,FDTD predictions versus experiment

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2001
    Iulian Codreanu
    Abstract We report on the successful use of niobium microbolometers coupled to microstrip dipole antennas for the detection of midinfrared radiation. Measurements of the detector response versus antenna length performed at the 10.6 ,m wavelength allowed us to identify the first three current-wave resonances along the antenna arms. The detector response was also measured as a function of the radiation wavelength in the 9,11 ,m spectral domain. Excellent agreement between the experimental results and finite-difference time-domain (FDTD) predictions was obtained. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 381,383, 2001. [source]