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Title: ACES Journal March 2006 Full Issue
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 4075 KB

Title: ACES Journal March 2006 Front/Back Matter
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 422 KB

Title: Numerical Modeling of Reconfigurable RF MEMS-based Structures Involving the Combination of Electrical and Mechanical Force
Abstract: MEMS are minimized electromechanical devices and systems that are realized using integrated micro fabrication methods. And the technology is growing rapidly in RF field, because of the advantages over p-i-n diode or FET switches. The main application areas of MEMS devices in the future are Information Technology, Bioelectromagnetic, Medical Science. For the accurate design of RF MEMS structures, effective computationally modeling of their transient and steady state behaviors including the accurate analysis of their time-dependent moving boundaries is essential. This is because an accurate knowledge of the electromagnetic field (EM) evolution around a moving or rotating body is very important for the realization of new optical devices or microwave devices, such as the RF-MEMS structures used in phase-shifters, couplers, filters, tuners or antennas. The technique proposed in this paper to model MEMS structures is based on the finite-difference time-domain (FDTD) method with an adaptive implementation of grid generation. Here, this simulation method is applied to the analysis of a two-dimensional MEMS variable capacitor with non-uniform motions, such as accelerated motions. The acceleration of the MEMS capacitor is derived under the equilibrium between the spring force and electrical force. Using this acceleration, the motion characteristic for each time step is derived. The numerical results that express the relationship between the acceleration of the plates and the spring constant and the mass of the plates are shown and the transient effect is accurately modeled.
Author(s): Kohei Kawano , Shafrida Sahrani , Takashi Mori , Michiko Kuroda
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 325 KB

Title: Comparative Study of Analytical and Simulated Doubly-Supported RF MEMS Switches for Mechanical and Electrical Performance
Abstract: Radio Frequency Microeletromechanical System (RF MEMS) switches are useful for providing lowloss switching elements in high frequency devices. Since these devices contain a mechanical and an electrical component to their operation, predicting their performance is not trivial. Computational analysis can be extremely complicated due to the large number of variables that need to be incorporated. Using a multi-physics simulation tool seems like the only solution, but most simulators are optimized for only one engineering realm (i.e. mechanics or electronics). Combining different engineering realms into one simulated model will usually compromise the accuracy of the results. Often simulators cannot model a multi-realm device at all. This paper offers a solution to this problem by proposing a technique for combining computational analysis with simulation to determine the pull-down voltage and RF characteristics of an RF MEMS switch. Measurement results agree closely with the simulated results using this technique.
Author(s): Nickolas Kingsley, Guoan Wang, John Papapolymerou
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 570 KB

Title: Equivalent Network Approach for the Simulation of MEMS Devices
Abstract: In this paper a numerical approach for the analysis of the behaviour of micro electro mechanical systems (MEMS) is presented. The method is applied to the simulation of movable plate MEMS variable capacitors that are of common use in the CMOS voltage controlled oscillators (VCOs). An accurate study of MEMS devices requires a coupled electro-mechanical analysis. The mechanical analysis has to take into account the deformation of the plates of the capacitor and the electromagnetic one has to consider the distribution of charges and currents and the presence of dielectric materials. We first perform a coupled elastic-electrostatic analysis in order to obtain the tuning characteristic of the system; subsequently, once the positions of the plates have been determined, an electromagnetic analysis of the system is performed via an integral formulation based on an electric equivalent circuit. The proposed method has been validated by analysing two and three plate tuneable parallel-plate capacitors.
Author(s): S. Barmada, A. Musolino, R. Rizzo
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 454 KB

Title: TWO-DIMENSIONAL COUPLED ELECTROSTATIC-MECHANICAL MODEL FOR RF MEMS SWITCHES
Abstract: Two-dimensional (2-D) coupled electrostatic-mechanical model of RF MEMS switches has been developed, in which the effect of residual stress due to the fabrication process and axial force resulting from the beam stretching have been taken into account. The electrostatic model is based on the application of the finite difference (FD) technique to quasi-static solution of a 2-D plane cut of the MEMS switch structure. The electrostatic model calculates the induced electrostatic force on the membrane due to the applied dc bias voltage. From the resulting electrostatic potential, the force distribution, the switch capacitance, and the beam deformation have been calculated. The computed pull down voltage for different structures agrees well with published data. The developed simulation program combines the electrostatic and mechanical analyses together and gives accurate results in short running time.
Author(s): Ehab K. I. Hamad, Atef Z. Elsherbeni, Amr M. E. Safwat, Abbas S. Omar
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 370 KB

Title: FDTD Analysis of a Probe-Fed Dielectric Resonator Antenna in Rectangular Waveguide
Abstract: Dielectric resonator antennas (DRA) are characterized for operation in a guided-wave environment with the ultimate goal of their use in modeling of waveguide-based DRA amplifier arrays for spatial power combining. Performance of a single probe-fed DRA element in rectangular waveguide is analyzed by varying design parameters of the DRA and the feeding probe to optimize the structure for the scattering characteristics (port matching and coupling). The effect of hard walls on the DRA behavior is also studied. The numerical analysis of waveguide-based DRA elements is based on the Finite-Difference Time-Domain (FDTD) method and a coaxial probe is modeled by a thin wire approximation implemented in the FDTD algorithm. The numerical results are compared with those generated by using commercial software and exhibit a very good agreement.
Author(s): Yizhe Zhang, Ahmed A. Kishk, Alexander B. Yakovlev, Allen W. Glisson
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 347 KB

Title: Introducing a Sub-cell Tensor Technique into a (2, 4) FDTD Method
Abstract: A sub-cell tensor based technique for modeling dielectric interfaces is introduced into a (2,4) FDTD method. For each cell containing an interface, a tensor based method that enforces continuity conditions is used to determine the fields on both sides the sloped interface. These fields are then volumetrically averaged. The approach is used to calculate a corrected field value at each grid point of the large fourth-order stencil. The combined algorithm is computationally homogeneous, unlike most previous algorithms of this type, and thus lends itself to parallel processing. Additionally, the method may be used with other higher-order stencils. The accuracy is tested using the exact Mie series solution for scattering from a dielectric sphere. It is shown that using the (2,4) tensor method results in ~50-70% less error than the (2,4) standard Yee method in the vicinity of a dielectric sphere.
Author(s): R.S. Schechter, S.T. Chun, M.S. Kluskens, M. Kragalott, D. A. Zolnick
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 307 KB

Title: MIXED ELEMENT FORMULATION FOR THE FINITE ELEMENT-BOUNDARY INTEGRAL METHOD
Abstract: A mixed element approach using right hexahedral elements and right prism elements for the finite element-boundary integral method is presented and discussed for the study of planar cavity-backed antennas. The mixed element method is shown to decrease the required computation time for geometrically constrained geometries by reducing the unknown count on the open aperture on the cavity. By reducing the unknown count on the surface, the memory and computational cost associated with the boundary integral portion of the solution is decreased versus solutions using only prism elements. The accuracy of the mixed element approach is shown to be comparable with that of a single element approach, especially for far field parameters such as radiation pattern and radar cross section.
Author(s): S.W. Schneider, J. Meese, L. C. Kempel
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 329 KB

Title: Investigation of an Explicit, Residual-Based, a Posteriori Error Indicator for the Adaptive Finite Element Analysis of Waveguide Structures
Abstract: The performance of an explicit, residual-based, a posteriori error indicator for directing a single level p-refinement of the finite element method, electromagnetic analysis of multiport waveguide structures is evaluated experimentally by considering three different structures. The error indicator consists of a linear combination of element volume and element face residuals. It is found that the indicator is generally very effective in identifying elements that need to be refined. It is also found that the relative weighting of the volume and face residual contributions to the error indicator plays an important role in its performance.
Author(s): Matthys M. Botha, David B. Davidson
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 251 KB

Title: Multiscale Analysis of Panel Gaps in a Large Parabolic Reflector
Abstract: The effect of the gaps between the panels of a reflector, used as a radio-telescope, is analyzed in this paper via the multiscale and array factor approach. Initially, the simulation is carried out by numerical integration as well as the Finite Difference Time Domain (FDTD) Method for a reflector with a moderately large diameter, and the results are then scaled for the actual size, which is thousands of wavelengths in diameter in the frequency range of interest. The array factor concept is employed to demonstrate the fact that the grating lobe cannot arise for the typical gap size of the reflector.
Author(s): Nader Farahat, Raj Mittra
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 220 KB

Title: Equalization of Numerically Calculated Element Patterns for Root-Based Direction Finding Algorithms
Abstract: Root-based direction finding algorithms (DF) have several advantages over search-based DF algorithms. A key advantage is the fact that they do not require the array steering vector; this is because these algorithms presume equalized element radiation patterns. In this paper, the WIPL-D code is used in designing an array of rectangular probe-fed patch antennas with equalized radiation patterns for measuring the range and bearing of RF emitters in the PCS band (1900-1920 MHz). Direction of arrival (DoA) estimation results based on simulations and measured data are presented and used as a measure of element patterns deviation from equality
Author(s): Hossam A. Abdallah, Wasyl Wasylkiwskyj, Ivica Kopriva
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 322 KB

Title: A STOCHASTIC ALGORITHM FOR THE EXTRACTION OF PARTIAL INDUCTANCES IN IC INTERCONNECT STRUCTURES
Abstract: With recent increases in operating frequencies, the modeling and extraction of on-chip inductance is becoming an increasingly significant consideration. The inductance models include the “loop inductance” models and the “partial inductance” models. In this paper, we develop a stochastic solution methodology for the extraction of partial inductances in IC interconnect structures. An important advantage of this approach is that it requires no discretization meshing of either the volume or the surface of the problem domain. As a result, it has very low memory requirements compared to the more conventional deterministic techniques. Another advantage of this approach is that it is inherently parallelizable and a linear increase in speed is expected with the increase in the number of processors. Excellent agreement has been obtained with analytical benchmark solutions.
Author(s): K. Chatterjee
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 272 KB

Title: An Extrapolation Method Based on Current for Rapid Frequency and Angle Sweeps in Far-Field Calculation in an Integral Equation Algorithm
Abstract: An extrapolation method based on the solution of induce current is introduced to rapidly perform angle and frequency sweep in the farfield calculation using the sparsely sampled solutions. This method is based on the observation of the characteristics of the current distribution as a function of incident angles and frequency. It is easy to be implemented for in core processing, and needs a small extra memory. In addition, the extrapolation applies to both angle and frequency sweeps. Numerical examples for conducting and material scatterers show that the far-field scattering results generated by the extrapolation method agree to that provided by the direct solution, but the extrapolation method uses about the same amount of memory, and much less CPU time than that of the brute-force approach.
Author(s): C. C. Lu
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 337 KB

Title: Asymptotic Waveform Evaluation Technique Based on Fast Lifting Wavelet Transform
Abstract: The asymptotic waveform evaluation (AWE) technique based on fast lifting wavelet transform (LWT) is applied to the method of moments to solve the combined-field integral equation (CFIE). The wide-band radar cross section of an arbitrarily shaped two-dimensional perfectly electric conduct object is calculated. The employment of CFIE eliminates the interior resonance problems. Numerical results presented in this paper are compared with the results obtained by the method of moments. It is shown that the computational efficiency is improved greatly.
Author(s): Chen Ming-Sheng , Wu Xian-liang , Sha Wei
File Type: Journal Paper
Issue:Volume: 21      Number: 1      Year: 2006
Download Link:Click here to download PDF     File Size: 280 KB