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Microstrip filter design using FDTD and neural networks

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2002年第3期34卷 219-224页

作者： Banciu, MG Ambikairajah, E Ramer, R Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia

A new design technique using the FDTD method and neural networks is applied to a microstrip filter. The total design time is reduced by two means. First, an iterative ARMA signal estimation technique is utilized to reduce the computation time for each FDTD run. Second, the number of FDTD simulations is decreased with the use of the device model provided by a neural network with the ARMA coefficients at the output. The trained network was then incorporated to an optimization procedure for a microstrip filter design. (C) 2002 Wiley Periodicals, Inc.

关键词： microstrip filters microwave design neural networks finite-difference time-domain method

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Optical waveguide analysis using a Yee-lattice-based modified finite-difference formula for an arbitrary dielectric interface

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS 2002年第12期85卷 1-9页

作者： Ando, T Nakayama, H Yamauchi, J Nakano, H Hosei Univ Fac Engn Koganei Tokyo 1848584 Japan

A modified finite-difference formula including the boundary condition of the field is applied to the eigenmode and propagation analysis of optical waveguides. First, in order to show the effectiveness of the modified finite-difference formula, the eigenmode solver is formulated using the imaginary axis method based on the Yee lattice. The fundamental mode of a two-dimensional step-index slab is computed. It is proved that the discontinuous field at the dielectric interface can be evaluated accurately. Further, a circular fiber is analyzed and its converged field is obtained with a lattice spacing larger than that in the conventional method. Finally, by using the finite-difference time-domain method, the propagating wave in a slanted waveguide is analyzed. It is pointed out that the quantization error caused by the staircase approximation can be reduced by the application of the modified finite-difference formula. (C) 2002 Wiley Periodicals, Inc.

关键词： Yee lattice modified finite-difference formula imaginary axis method finite-difference time-domain method eigenmode analysis propagating wave analysis quantization error

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Simulation of simultaneous tracking/data signal detection using novel aperture-mounted surface recording head

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 2002年第3B期41卷 1628-1631页

作者： Tanaka, K Ohkubo, T Oumi, M Mitsuoka, Y Nakajima, K Hosaka, H Itao, K Univ Tokyo Grad Sch Frontier Sci Bunkyo Ku Tokyo 1138656 Japan Seiko Instruments Inc Matsudo Chiba 2702222 Japan

Recently, near-field surface recording based on near-field optical principles has been vigorously studied for higher data storage density. In near-field optics which utilizes an aperture, in addition to the high spatial resolution property, there is another characteristic that the shape of the optical spot can be arbitrarily controlled by the aperture configuration, and its application to various technologies in the optical disk drive is possible. From this perspective, we propose a novel tracking method utilizing an asymmetric configured aperture head which could provide continuous signal of readout data and tracking error simultaneously, and analyze its data read-out and tracking detection performance through the three-dimensional finite-difference time-domain (3D-FDTD) method. Our simulations reveal that this novel tracking head has sufficient data readout performance and high tracking sensitivity, and has the potential to readout both a data signal and a tracking signal simultaneously.

关键词： near-field optics near-field optical head tracking method finite-difference time-domain method

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Light propagation through alignment-patterned liquid crystal gratings

MOLECULAR CRYSTALS AND LIQUID CRYSTALS

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MOLECULAR CRYSTALS AND LIQUID CRYSTALS 2002年 375卷 491-500页

作者： Scharf, T Bohley, C Univ Neuchatel Inst Microtechnol CH-2000 Neuchatel Switzerland

We analysed the light propagation through alignment-patterned liquid crystal films where the alignment is planar and homeotropic for different domains, respectively. Using elastic theory the nematic director field can be analytically calculated with the method of conformal mapping in the one elastic constant approximation. A smooth change of the nematic director field is found with defect points at the substrate surfaces. In order to investigate the propagation of light passing through such a liquid crystalline thin film with spatially varying birefringence, we use a rigorous method. The use of rigorous methods allows the simulation of the time-dependent electric and magnetic fields for a region that is two-dimensional and possibly anisotropic. Simulations are made by the finite-difference time-domain method (FDTD), which is a numerical approach for the rigorous solution of the Maxwell equations. This method, in contrast to methods of geometrical and matrix optics, delivers results which include diffraction and scattering.

关键词： liquid crystal gratings anisotropic gradient index media light propagation finite-difference time-domain method

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Mechanisms for enhancing power throughput from planar nano-apertures for near-field optical data storage

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 2002年第3B期41卷 1632-1635页

作者： Shi, XL Hesselink, L Stanford Univ Dept Elect Engn Palo Alto CA 94305 USA

Near-field optical data storage systems are important for ultrahigh density data storage. One type of near-field optical data Storage system uses a planar nano-aperture to define the data storage resolution. However, conventional nano-apertures have a tradeoff between resolution and power throughput. Recently, we reported a novel "C"-aperture design to overcome this problem. In this paper, we present our study on the mechanisms for power throughput enhancement, based on a detailed study of nano-slits using numerical simulations. We find that generating a propagation mode is essential for high power throughput, and by optimizing the design of the aperture thickness, resonant transmission can be achieved for even higher power throughput.

关键词： nano-aperture nano-slits near-field optics finite-difference time-domain method power throughput "C"-aperture mechanism

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FDTD and PSTD simulations for plasma applications

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2001年第2期29卷 341-348页

作者： Fan, GX Liu, QH Hutchinson, SA Duke Univ Dept Elect & Comp Engn Durham NC 27708 USA Sandia Natl Labs Albuquerque NM 87185 USA

Three-dimensional finite-difference time-domain (FDTD) and pseudospectral time-domain (PSTD) algorithms, with perfectly matched layer absorbing boundary condition, are presented for nonmagnetized plasma as a special case of general inhomogeneous, dispersive, conductive media. The algorithms are tested for three typical frequency bands, and an excellent agreement between the FDTD/PSTD numerical results and analytical solutions is obtained for all cases. Several applications, such as laser-pulse propagation in plasma hollow channels, surface-wave propagation along a plasma column of finite length, and energy deposition of electron cyclotron resonance plasma source, demonstrate the capability and effectiveness of these algorithms. The PSTD algorithm is more efficient and accurate than the FDTD algorithm, and is suitable for large-scale problems, while the FDTD algorithm is more suitable for fine details. The numerical results also show that plasma has complex transient responses, especially in the low-frequency and resonance regimes, Because of their flexibility and generality, the algorithms and computer programs can be used to simulate various electromagnetic waves-plasma interactions with complex geometry and medium properties, both in time and frequency domains.

关键词： finite-difference time-domain method perfectly matched layer plasma plasma applications plasma sources pseudospectral time-domain method

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A new 3-D FDTD multigrid technique with dielectric traverse capabilities

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2001年第3期49卷 422-430页

作者： White, MJ Yun, ZQ Iskander, MF Univ Utah Dept Elect Engn Salt Lake City UT 84112 USA

The finite-difference time-domain (FDTD) technique has become increasingly popular and is being used to model extremely complex and electrically large structures, These simulations are computationally demanding and often exceed available limits on computer resources, In this paper, we present an FDTD sub-gridding technique that allows for increased resolution in regions of interest without increasing the overall computational requirements beyond the available resources. Furthermore, the formulation presented here allows for traversing dielectric boundaries using any integer refinement factor and the maximum Courant number By allowing the coarse-/fine-grid boundary to traverse dielectric boundaries, numerical simulations that were previously either extremely difficult or impossible to perform are now possible. The technique presented here uses a weighted current value from the coarse region at the boundary between the fine- and coarse-grid regions to update the fine-region tangential fields on that boundary, The weighting function depends on the material properties and the relative position of the fine-region electric field within the current contour at the boundary. The complete formulation of this new technique is described and some results of simulation cases are presented to validate the accuracy and stability of the newly developed FDTD code. Simulations include simple cases where the analytical solution exists and more complex cases, which were impossible to model using a uniform-grid FDTD code, In some simulation examples, computer memory savings as high as 70 times what would have been necessary with a uniform-grid code were achieved, It is shown that errors of less than 2% are achievable with ratios of coarse-to-fine grid sizes exceeding ten, The new technique is expected to be used in simulating many electrically large and complex structures in the biomedical microwave processing of materials and the wireless communications areas.

关键词： complex structures dielectric traverse electrically large finite-difference time-domain method multigrid sub-gridding

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Integrated multibeam dual-polarised planar array

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IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION 2001年第3期148卷 174-178页

作者： Gao, SC Li, LW Leong, MS Yeo, TS Natl Univ Singapore Dept Elect & Comp Engn Singapore 119260 Singapore

A novel four-beam dual-polarised microstrip antenna array at the 10GHz band is presented. By using a multilayered structure and multiport slot-coupled microstrip lines, two Butler matrix microstrip circuits corresponding to two orthogonal polarisations can be located on different substrate lavers (above and below the ground plane) and integrated with a patch array. The antenna has eight input ports corresponding to two orthogonal polarisations and four beams. The theoretical design is based on the finite-difference time-domain (FDTD) method. The measured return loss and isolation characteristics exceed 10 and 23 dB, respectively, in the 9.7-10.3GHz band. The radiation pattern is close to an ideal Butler pattern and the cross-polarisation level is lower than -18dB in the beams. Details of the antenna and its characteristics are presented.

关键词： multiport networks microstrip antenna arrays finite difference time-domain analysis Antenna arrays FDTD method stacked microstrip patches planar antenna arrays Butler matrix microstrip circuits electromagnetic wave polarisation patch array orthogonal polarisations four-beam microstrip antenna array radiation pattern antenna radiation patterns finite-difference time-domain method 9.7 to 10.3 GHz return loss integrated multibeam dual-polarised planar array multilayered structure substrate layers multiport slot-coupled microstrip lines H-plane patterns cross-polarisation level ideal Butler pattern Other numerical methods isolation characteristics multibeam antennas

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finite-difference time-domain analysis on nonlinear Fabry-Perot resonator in optical waveguide geometry

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 2001年第4A期40卷 2259-2263页

作者： Fujii, M Okamoto, T Haraguchi, M Fukui, M Al-Bader, SJ Univ Tokushima Fac Engn Dept Opt Sci & Technol Tokushima 7708506 Japan King Fahd Univ Petr & Minerals Dept Elect Engn Dhahran 31261 Saudi Arabia

The finite-difference time-domain (FDTD) method is applied to investigate the characteristics of nonlinear Fabry-Perot (FP) resonators in optical waveguide geometries. Our treatment, which is the extension of Tran's method developed to analyse the characteristics of nonlinear photonic crystals, correctly reproduces analytical results on optical bistabilities of the FP resonator provided by Chen and Mills in 1987. It is found that the minimum power required for optical bistabilities is significantry decreased by adopting the optical waveguide geometry, compared with the case of Chen and Mills, i.e., a conventional nonlinear FP interferometer.

关键词： finite-difference time-domain method nonlinear Fabry-Perot resonator third-order nonlinear optical effect guided optics

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Low cost, dual linearly polarised microstrip patch array

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IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION 2001年第1期148卷 21-24页

作者： Gao, SC Li, LW Yeo, TS Leong, MS Natl Univ Singapore Dept Elect & Comp Engn Singapore 119260 Singapore

The design and experiments of a novel dual linearly polarised (LP) microstrip antenna array with a high isolation and low cross-polarisation levels are presented. The theoretical analysis is based on the finite-difference time-domain method and the multiport network model. The multifeed technique and the diagonal feeding are combined to realise the dual-polarised antenna elements. A single antenna element is designed and the experimental results show a good isolation between two polarisation ports. The dual LP elements are sequentially rotated to form the microstrip antenna array. A four-element dual LP array is also designed at 6.6GHz and measured. Both theoretical and experimental results are presented and compared. The proposed array uses a single-layer structure so it is easy to fabricate and the cost is very low. It is also easy to extend the principle of present array to large-scale dual LP arrays and those of multilayered structures.

关键词： multiport networks finite difference time-domain analysis microstrip antenna arrays multilayered structures Antenna arrays cross-polarisation levels polarisation ports electromagnetic wave polarisation diagonal feeding antenna element 6.6 GHz antenna radiation patterns finite-difference time-domain method multifeed technique Antenna accessories four-element dual LP array single-layer structure low cost dual linearly polarised microstrip patch array dual-polarised antenna Other numerical methods multiport network model antenna feeds

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