Full-wave Finite Difference Research Articles

A Two-dimensional Full-wave Finite-difference Frequency-domain Analysis of Ferrite Loaded Structures

A two-dimensional (2-D) full-wave finite-difference frequency-domain (FDFD) method is presented for analyzing the dispersion characteristics of transversely magnetized ferrite loaded structures. Results for a number of different ferrite loaded structures are presented. The accuracy of the FDFD formulation is verified by comparing the numerical results with analytical results and those obtained using the FDTD method, and very good agreement is obtained.

Physical configuration and performance modeling of all-dielectric metamaterials

In this paper, physical concept and performance analysis of all-dielectric metamaterials are presented. Metamaterials with desired material parameters $(\ifmmode\pm\else\textpm\fi{}\ensuremath{\epsilon},\ifmmode\pm\else\textpm\fi{}\ensuremath{\mu})$ are developed by creating electric and magnetic resonant modes. Dielectric disk and spherical particle resonators are considered as the great candidates for establishing the dipole moments (metamaterial alphabet). A full wave finite difference time domain technique is applied to comprehensively obtain the physical insights of dielectric resonators. Near-field patterns are plotted to illustrate the development of electric and magnetic dipole fields. Geometric-polarization control of the dipole moments allows $\ensuremath{\epsilon}$ and $\ensuremath{\mu}$ to be tailored to the application of interest. All-dielectric double negative metamaterials are designed. Engineering concerns, such as loss reduction and bandwidth enhancement are investigated.

Development of Chiral Negative Refractive Index Metamaterials for the Terahertz Frequency Regime

A novel negative refractive index (NRI) chiral meta-material (MTM), based on the Y structure, has been designed and tested in the microwave and terahertz frequencies. In addition to providing magnetoelectric coupling, this MTM has a negative index of refraction passband that can be tuned in both the frequency of operation and bandwidth with lower losses compared to other known chiral structures. Group theory was used to analyze the magnetoelectric coupling of the Y-shaped structure and circuit analysis was used to aid in the design of the NRI material and full-wave finite difference time domain (FDTD) simulations were conducted to determine the transmission characteristics of the material. Wedge-and prism-shaped models comprised of the designed structures were simulated to validate the NRI behavior and were then compared to experimental results in the microwave regime. Furthermore, the Y-shaped design was fabricated in the THz regime and the co-and cross-polarized transmission coefficients were determined from experiments and were compared to numerical results.

A Coupled Efficient and Systematic Full-Wave Time-Domain Macromodeling and Circuit Simulation Method for Signal Integrity Analysis of High-Speed Interconnects

This paper presents an accurate and systematic approach for analysis of the signal integrity of the high-speed interconnects, which couples the full-wave finite difference time domain (FDTD) method with scattering (S) parameter based macromodeling by using rational function approximation and the circuit simulator. Firstly, the full-wave FDTD method is applied to characterize the interconnect subsystems, which is dedicated to extract the S parameters of the subnetwork consisting of interconnects with fairly complex geometry. Once the frequency-domain discrete data of the S parameters of the interconnect subnetwork is constructed, the rational function approximation is carried out to establish the macromodel of the interconnect subnetwork by employing the vector fitting method, which provides a more robust and accurate solution for the overall problem. Finally, the analysis of the signal integrity of the hybrid circuit can be fulfilled by using the S parameters based macromodel synthesis and simulation program with integrated circuits emphasis (SPICE) circuit simulator. Numerical experiments demonstrate that the proposed approach is accurate and efficient to address the hybrid electromagnetic (interconnect part) and circuit problems, in which the electromagnetic field effects are fully considered and the strength of SPICE circuit simulator is also exploited.

Neural network with knowledge‐based neurons for the modeling of crossover discontinuities in stripline circuits

AbstractA novel three‐layer neural network with knowledge‐based neurons in hidden layer (NNKBN) has been applied to model the crossover discontinuities in stripline circuits. The NNKBN model is electromagnetically developed with a set of data that are produced by the full‐wave finite‐difference–time‐domain method. Numerical experiments show that the NNKBN model has many advantages over the conventional multilayer perceptron model. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 107–109, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10387

Dielectric resonances and B1 field inhomogeneity in UHFMRI: computational analysis and experimental findings

B1 Field inhomogeneity and the relative effects of dielectric resonances are analyzed within the context of ultra high field MRI. This is accomplished by calculating the electromagnetic fields inside spherical phantoms and within a human head model in the presence and absence of an RF coil. These calculations are then compared to gradient echo and RARE images, respectively. For the spherical phantoms, plane incident wave analyses are initially presented followed by full wave finite difference time domain (FDTD) calculations. The FDTD methods are then utilized to examine the electromagnetic interactions between the TEM resonator and an anatomically detailed human head model. The results at 340 MHz reveal that dielectric resonances are most strongly excited in objects similar in size to the human head when the conducting medium has a high dielectric constant and a low conductivity. It is concluded that in clinical UFHMRI, the most important determinants of B1 field homogeneity consist of 1) the RF coil design, 2) the interaction between the RF coil, the excitation source and the sample, and finally 3) the geometry and electrical properties of the sample.

Seismic Wave Propagation and Scattering in Heterogeneous Crustal Waveguides Using Screen Propagators: I SH Waves

The great advantages of one-way propagation methods, such as the gen- eralized screen propagators (GSP) method, are the fast speed of computation, often several orders of magnitude faster than the full-wave finite difference and finite element methods, and the huge savings in internal memory. In this article, a half- space GSP is formulated for the SH half-space problem. Two versions of the half- space GSP are derived: the wide-angle pseudo-screen and the phase-screen. The Moho discontinuity is treated as parameter perturbations from the crustal back- ground. The validity and limitations of this treatment are discussed. It is shown that half-space screen propagators can accurately propagate guided crustal waves that are composed of small-angle waves with respect to the horizontal direction. Comparisons of numerical results with a wavenumber integration method for flat crustal models and a finite difference algorithm for heterogeneous models show excellent agree- ments. For a model with propagation distance of 250 km, dominant frequency at 0.5 Hz, the GSP method is about 300 times faster than a finite difference algorithm with a similar accuracy. These comparisons demonstrate the accuracy and efficiency of the method. We apply our method to simulate regional wave propagation in different types of complex crustal waveguides including those with small-scale random het- erogeneities. The influence of these heterogeneities on Lg amplitude attenuation and Lg coda formation is significant.

Electromagnetic simulation of bonding wires and comparison with wide band measurements

Several typical bonding wire configurations have been measured in a frequency range up to 20 GHz using a vector network analyzer. Based on scanning electron microscope (SEM) pictures all bonding wires have been discretized and orthogonal grids suitable for electromagnetic simulation have been generated. Full wave finite difference time domain (FDTD) simulations as well as static and quasi static inductance extraction using a new Monte Carlo technique and FastHenry as well as capacitance extraction with a finite element method have been carried out. Numerical results are compared to measured scattering parameters and their quality and frequency dependence is discussed. All simulation techniques are evaluated with respect to their computational effort.