Elene Chobanyan

Double-Higher-Order Large-Domain Volume/Surface Integral Equation Method for Analysis of Composite Wire-Plate-Dielectric Antennas and Scatterers

A novel double-higher-order large-domain Galerkin-type method of moments based on higher order geometrical modeling and higher order current modeling is proposed for analysis of composite dielectric and metallic radiation/scattering structures combining the volume integral equation (VIE) approach for dielectric parts and the surface integral equation (SIE) approach for metallic parts of the structure. The technique employs Lagrange-type interpolation generalized hexahedra and quadrilaterals of arbitrary geometrical-mapping orders for the approximation of geometry and hierarchical divergence-conforming polynomial vector basis functions of arbitrary expansion orders for the approximation of currents within the elements. The double-higher-order VSIE (VIE-SIE) method is extensively validated and evaluated against the analytical solutions and the numerical results obtained by alternative higher order methods.

Non-intrusive pseudo spectral approach for stochastic macromodeling of EM systems using deterministic full-wave solvers

In this paper, a novel stochastic macromodeling technique for the variability analysis of complex electromagnetic (EM) structures is proposed. This work combines a pseudo spectral approach with the Loewner matrix interpolation technique to generate the polynomial chaos macromodel from the stochastic S-parameters of the structure. The major benefit of the proposed strategy is that by exploiting the non-intrusive nature of the pseudo spectral approach, the stochastic macromodel can be generated directly from a small number of deterministic EM full-wave simulations. This enables the utilization of the robustness and versatility of conventional deterministic full-wave techniques without the need for the cumbersome stochastic Galerkin formulation.

Efficient and Accurate Computational Electromagnetics Approach to Precipitation Particle Scattering Analysis Based on Higher-Order Method of Moments Integral Equation Modeling

AbstractA new full-wave computational electromagnetics (CEM) approach to precipitation particle scattering analysis based primarily on a higher-order method of moments (MoM) for solving surface integral equations (SIEs) is proposed, as an alternative and addition to the conventionally used tools in this area. This is a well-established CEM approach that has not been applied, evaluated, discussed, or compared with other approaches in the scattering analysis of precipitation particles so far. Several characteristic examples of scattering from precipitation particles of various shapes demonstrate the capabilities and potential of the presented numerical methodology, and discuss its advantages over both discrete dipole approximation (DDA) and -matrix methods in cases considered. In particular, it is shown that the higher-order MoM-SIE approach is much faster, more accurate, and more robust than the DDA method, and much more general and versatile than the -matrix method. In addition, the paper illustrates prob...

Measurement and characterization of winter precipitation at MASCRAD Snow Field Site

We present our ongoing studies of winter precipitation using multi-angle snowflake camera (MASC), 2D-video disdrometer, computational electromagnetic scattering methods, and state-of-the-art polarimetric radars. The newly built and established MASCRAD (MASC + Radar) Snow Field Site is one of the currently best instrumented and most sophisticated field sites for winter precipitation measurements and analysis in the nation. We present and discuss MASCRAD measurements for the snow event on Nov 15, 2014 in La Salle, Colorado.

Visual hull method based shape reconstruction of snowflakes from MASC photographs

We present utilization of the visual hull geometrical method for reconstruction of 3D shapes of snowflakes and ice particles based on high-resolution photographs of an object from multiple angles and the corresponding 2D silhouettes, for the purpose of further scattering analysis. The images are obtained by a multi-angle snowflake camera (MASC). Preliminary results appear to be much more accurate than any other available snowflake shape reconstruction examples, and are indicative of a great potential of the proposed approach.

Electromagnetic scattering by oscillating rain drops of asymmetric shapes

Computational electromagnetic analysis of scatting by oscillating rain drops with asymmetric shapes is presented. Mixed-mode oscillations of drops are attributed to sustained drop collisions in events having a highly organized line convection embedded within a larger rain system. The scattering matrix and differential reflectivity of drops are dependent on the particular oscillation modes and different time instants within the oscillation cycle. The results also demonstrate the superiority of the higher order method of moments over the conventional discrete dipole approximation method in oscillating rain drop analysis.

Volume Integral Equation-Based Diakoptic Method for Electromagnetic Modeling

A novel diakoptic method based on volume integral equation (VIE) modeling of subsystems is proposed for 3-D electromagnetic analysis. The theoretical foundation of the method is the surface and volume equivalence principles, as it combines the VIE and surface integral equation (SIE) formulations, in conjunction with the method of moments (MoM). The method breaks the original structure into a number of nonoverlapping closed-region subsystems that contain inhomogeneous dielectric materials and an open-region subsystem. Each subsystem is analyzed completely independently applying the double higher order large-domain Galerkin generalized MoM-VIE-SIE (VSIE) or MoM-SIE solvers. The final solution is obtained from diakoptic matrices expressing linear relations between the electric and magnetic equivalent surface current coefficients on diakoptic surfaces. The proposed VSIE-diakoptic method is validated, evaluated, and discussed in several characteristic examples. The examples demonstrate that the diakoptic method substantially increases the efficiency of the conventional MoM-VIE approach. When compared with the pure MoM-VIE double higher order technique, the diakoptic approach enables very considerable accelerations and memory savings, while fully preserving the accuracy of the analysis.

Accurate electromagnetic modeling of melting hail

Analysis of electromagnetic scattering from hailstones has conventionally been done using the T-matrix method. This method, which reduces exactly to the Lorenz-Mie scattering theory when the scattering particle is a homogeneous or layered piecewise homogeneous sphere, worked well so far when we tried to understand the measurements. However the measurements have become fairly sophisticated with many decades of multiple polarization measurements and the current models are not able to explain many of the nuances in the measurements, because the current model is not well suited for analysis of arbitrarily shaped and non-layered particles.

Atmospheric particle scattering computation using higher order MoM-SIE method

Full-wave computational electromagnetics (CEM) approach based on the method of moments (MoM) for solving surface integral equations (SIEs) is proposed for atmospheric particle scattering analysis. The methodology is implemented as a higher order CEM technique. The paper demonstrates that the higher order MoM-SIE approach is much more efficient, accurate, general, and robust than the conventionally and almost exclusively used tools in atmospheric scattering analysis, namely, the T-matrix method and the discrete dipole approximation (DDA) method.

Combining diakoptic, VIE-MoM, and SIE-MoM approaches in analysis of dielectric scatterers

A method combining the diakoptic approach with both the volume integral equation (VIE) and the surface integral equation (SIE) approaches is proposed for analysis of dielectric scatterers. The diakoptic method breaks the original problem into smaller and simpler ones and solves them completely independently, using explicit linear relations between coefficients in expansions of equivalent surface currents on boundary surfaces of diakoptic subsystems. The numerical implementation is carried out using a higher order method of moments (MoM). In a numerical model, some diakoptic subsystems are analyzed by the SIE-MoM and some (considerably inhomogeneous) by the VIE-MoM. The VIE-SIE-diakoptics method is validated in an example of a 4×4×1 array of dielectric cubical scatterers.