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Koziel S.,Engineering Optimization and Modeling Center | Jacobs J.P.,Electronic and Computer Engineering
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

We present a computationally efficient method for detecting faulty elements in a small linear microstrip patch array from samples of the array's far-field magnitude radiation pattern (here represented by realistic EM simulations). Regardless of the array size, our method requires only one expensive full-wave entire-array simulation-compared to, e.g., the 696 required by the previous best method (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777) for a 16-element array. This one simulation gives the accurate far-field magnitude pattern of the original defect-free array, and is used in conjunction with the defect-free array's analytical array factor to formulate a response correction function, which can then be used to construct an accurate approximation of the EM-simulated pattern of any arbitrary faulty array at very low cost. The low cost and high accuracy of these approximations make possible an enumeration strategy for identifying the faulty elements, which would have been computationally prohibitive were EM-simulated patterns to be used. Our method was robust in handling arrays of double the size considered in Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777, while expanding on (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775-777) by also addressing partial faults and measurement noise. Accuracies in detecting up to three faults (including partial ones) in arrays of 16 and 32 elements exceeded 97% under noise-free conditions, and were above 93% in the presence of 2 dB measurement noise. © 2016 Wiley Periodicals, Inc. Source


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

Geometry scaling of compact microwave structures is a challenging problem because of complex relationships between the physical dimensions of the circuit and its electrical characteristics, which is mostly caused by considerable cross-couplings in densely arranged layouts. Yet, possibility of rapid redesign of a structure for various sets of design specification is important from practical point of view. In this article, we develop a procedure for expedited dimension scaling of compact microwave couplers with respect to two independent criteria. Our approach exploits inverse surrogates constructed at the level of equivalent circuit model and correction techniques that permits low-cost re-design of the coupler structure (at the level of EM-simulation model) for a required operating frequency and power split ratio. The procedure is demonstrated using a folded microstrip rat-race coupler. The scaling range for the considered example is from 0.5 to 2.0 GHz for the operating frequency, and from -6 dB to 0 dB for the power split ratio. © 2016 Wiley Periodicals, Inc. Source


Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Engineering Optimization and Modeling Center
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2016

In this article, we describe a procedure for reliable and computationally efficient design optimization of miniaturized impedance matching transformers. Our approach exploits a concept of feature-based optimization (FBO). According to FBO, considerable reduction of the computational cost of the simulation-driven design process can be achieved-compared to conventional methods-by reformulating given performance requirements (typically, minimization of reflection over a frequency range of interest) in terms of suitably defined response features. For impedance transformer circuits, the feature points are defined as local maxima of the reflection characteristic, as well as the points defining the -20 dB bandwidth. As the feature point coordinates (i.e., their frequencies and levels) depend on the geometry parameters of the structure in less nonlinear manner than the original responses (S-parameters versus frequency), the optimization algorithm exhibits faster convergence. Further reduction of the optimization cost is obtained by utilization of variable-fidelity electromagnetic simulations. Our technique is demonstrated using two design cases of an example miniaturized three-section 50-to-100 ohm microstrip transformer. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016. © 2016 Wiley Periodicals, Inc. Source


Koziel S.,Reykjavik University | Koziel S.,Engineering Optimization and Modeling Center | Bekasiewicz A.,Reykjavik University | Bekasiewicz A.,Engineering Optimization and Modeling Center | Leifsson L.,Iowa State University
Procedia Computer Science | Year: 2015

A procedure for low-cost multi-objective design optimization of antenna structures is discussed. The major stages of the optimization process include: (i) an initial reduction of the search space aimed at identifying its relevant subset containing the Pareto-optimal design space, (ii) construction-using sampled coarse-discretization electromagnetic (EM) simulation data-of the response surface approximation surrogate, (iii) surrogate optimization using a multi-objective evolutionary algorithm, and (iv) the Pareto front refinement. Our optimization procedure is demonstrated through the design of a planar quasi Yagi-Uda antenna. The final set of designs representing the best available trade-offs between conflicting objectives is obtained at a computational cost corresponding to about 172 evaluations of the high-fidelity EM antenna model. © The Authors. Published by Elsevier B.V. Source


Bekasiewicz A.,Reykjavik University | Bekasiewicz A.,Engineering Optimization and Modeling Center | Koziel S.,Reykjavik University | Koziel S.,Engineering Optimization and Modeling Center | Leifsson L.,Iowa State University
Procedia Computer Science | Year: 2015

A methodology for a rapid design optimization of integrated photonic couplers is presented. The proposed technique exploits variable-fidelity electromagnetic (EM) simulation models, additive response correction for accommodating the discrepancies between the EM models of various fidelities, and local response surface approximations for a fine tuning of the final design. A specific example of a 1,555 nm coupler is considered with an optimum design obtained at a computational cost corresponding to about 24 high-fidelity EM simulations of the structure. © The Authors. Published by Elsevier B.V. Source

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