Babak Alavikia

Electromagnetic energy harvesting using complementary split-ring resonators

The current invention provides Ground-backed Complementary Split Ring Resonators (G-CSRR) as a new class of energy collectors and transmitters for electromagnetic energy harvesting in general and wireless power transfer applications in particular. The G-CSRR structure has low profile, low fabrication cost, efficient for wide range of illumination angles and can be placed on metallic surfaces.

Finite-element solution of the problem of scattering from cavities in metallic screens using the surface integral equation as a boundary constraint

This work presents a novel finite-element solution to the problem of scattering from multiple two-dimensional cavities in infinite metallic walls. The technique presented here is highly efficient in terms of computing resources and is versatile and accurate in comparison with previously published methods. The formulation is based on using the surface integral equation with the free-space Greens function as the boundary constraint. The solution space is divided into local bounded frames containing each cavity. The finite-element formulation is applied inside each frame to derive a linear system of equations associated with nodal field values. The surface integral equation is then applied at the opening of the cavities to truncate the computational domain and to connect the matrix subsystem generated from each cavity. The near and far fields are generated for different single and multiple cavity examples. The results are in close agreement with methods published earlier.

Complementary split ring resonator arrays for electromagnetic energy harvesting

This work demonstrates the viability of Ground-backed Complementary Split-Ring Resonator (G-CSRR) arrays with significant power conversion efficiency and bandwidth enhancement in comparison to the technology used in current electromagnetic energy harvesting systems. Through numerical full-wave analysis, we demonstrated correlation between either the resonance frequency or the input impedance of G-CSRR cells with the periodicity of the array. A comparative study of power harvesting efficiency through numerical analysis and laboratory measurement was presented where an array of G-CSRRs is compared to an array of microstrip patch antennas. We demonstrated that a G-CSRR array yields power conversion efficiency of 92%, which represents a significant improvement in comparison to the single G-CSRR reported in our earlier work.

Wideband resonator arrays for electromagnetic energy harvesting and wireless power transfer

This work demonstrates the viability of wideband Ground-backed Complementary Split-Ring Resonator (WG-CSRR) arrays with significant power conversion efficiency and bandwidth enhancement in comparison to the technology used in current electromagnetic energy harvesting systems. Through numerical full-wave analysis, we demonstrated the correlation between the topology of the WG-CSRR patch and the electric current distribution over the patch at different frequencies. A comparative study of power harvesting efficiency and frequency bandwidth through numerical analysis was presented where an array of WG-CSRRs is compared to an array of G-CSRRs and an array of microstrip patch antennas. A significant improvement in bandwidth is achieved in comparison to the G-CSRR array reported in earlier work.

Electromagnetic scattering from cylindrical objects above a conductive surface using a hybrid finite-element–surface integral equation method

This work presents a novel finite-element solution to the problem of scattering from a finite and an infinite array of cylindrical objects with arbitrary shapes and materials over perfectly conducting ground planes. The formulation is based on using the surface integral equation with Greens function of the first or second kind as a boundary constraint. The solution region is divided into interior regions containing the cylindrical objects and the region exterior to all the objects. The finite-element formulation is applied inside the interior regions to derive a linear system of equations associated with nodal field values. Using two-boundary formulation, the surface integral equation is then applied at the truncation boundary as a boundary constraint to connect nodes on the boundaries to interior nodes. The technique presented here is highly efficient in terms of computing resources, versatile, and accurate in comparison with previously published methods. The near and far fields are generated for a finite and an infinite array of objects. While the surface integral equation in combination with the finite-element method was applied before to the problem of scattering from objects in free space, the application of the method to the important problem of scattering from objects above infinite flat ground planes is presented here for the first time, to our knowledge.

Reduction of Electromagnetic Radiation from Apertures and Enclosures Using Electromagnetic Bandgap Structures

Comprehensive study on the source of electromagnetic radiation from apertures placed in conducting screens and enclosure is presented. Novel technique comprising placement of electromagnetic bandgap (EBG) structures immediately around the apertures openings is presented to suppress the surface currents and consequently to reduce the radiation from the apertures. The effectiveness of the proposed technique is demonstrated through several detailed parametric studies and numerical full-wave simulations quantifying the strength of electromagnetic fields in near and far regions from the aperture. In fact, using the EBG structures, more than 20-dB reduction is achieved in the near- and far-field radiation without affecting the aperture size. Finally, a detailed experimental case study from real-world environment is presented to validate the proposed concept.

Hybrid finite-element-boundary integral algorithm to solve the problem of scattering from a finite and infinite array of cavities with stratified dielectric coating

This work presents a hybrid finite-element-boundary integral algorithm to solve the problem of scattering from a finite and infinite array of two-dimensional cavities engraved in a perfectly electric conducting screen covered with a stratified dielectric layer. The solution region is divided into interior regions containing the cavities and the region exterior to the cavities. The finite-element formulation is applied only inside the interior regions to derive a linear system of equations associated with unknown field values. Using a two-boundary formulation, the surface integral equation employing the grounded dielectric slab Greens function in the spatial domain is applied at the opening of the cavities as a boundary constraint to truncate the solution region. Placing the truncation boundary at the opening of the cavities and inside the dielectric layer results in a highly efficient solution in terms of computational resources, which makes the algorithm well suited for the optimization problems involving scattering from grating surfaces. The near fields are generated for an array of cavities with different dimensions and inhomogeneous fillings covered with dielectric layers.

Efficient 2-D Finite-Difference Frequency-Domain Method for Switching Noise Analysis in Multilayer Boards

A new numerical algorithm is presented to solve the problem of switching noise in multilayer circuit boards and packages. The algorithm is based on domain decomposition using the finite-difference frequency-domain (FDFD) method. Each layer of the multilayer board or package is modeled using a standard 2-D FDFD scheme and linked to other layers through a multiport network that effectively incorporates the via circuit models between the layers. It is shown that the algorithm is simple to implement and is highly efficient for multilayer boards or packages as the overall FDFD system matrix is highly sparse, thus can be solved very efficiently using advanced sparse matrix solvers. Furthermore, successive solution of the system matrix for different source and victim locations does not call for new fill of the system matrix, thus allowing efficient analysis of different source and victim locations. To validate the new algorithm, we manufacture a three-layer board, measure the scattering parameters between two specific locations, and obtain strong agreement with the solution obtained using the FDFD scheme introduced here.

Hybrid finite element-boundary integral algorithm to solve the problem of scattering from a finite array of cavities with multilayer stratified dielectric coating

This work presents a hybrid finite element-boundary integral algorithm to solve the problem of scattering from a finite array of two-dimensional cavities engraved in a perfectly electric conducting screen covered with multilayer stratified dielectric coating. The solution region is divided into interior regions containing the cavities and the region exterior to the cavities. The finite element formulation is applied only inside the interior regions to derive a linear system of equations associated with unknown field values. Using a two-boundary formulation, the surface integral equation employing a closed-form multilayer Greens function in the spatial domain is applied at the opening of the cavities as a boundary constraint to truncate the solution region. The closed-form Greens function in the spatial domain for multilayer planar coating is expressed in terms of complex images using the generalized pencil-of-function method in conjunction with a two-level sampling approach. Placing the truncation boundary at the opening of the cavities and inside the dielectric coating results in a highly efficient solution in terms of computational resources, which makes the algorithm well suited for optimization problems involving scattering from grating surfaces. The near fields are generated for array of cavities with different dimensions and inhomogeneous fillings covered with dielectric layers.

Limitation of using absorbing boundary condition to solve the problem of scattering from a cavity in metallic screens

Interest in accurate modeling of electromagnetic wave scattering from grating surfaces has been renewed due to the emergence of novel application of plasmonic resonance such as near-field microscopy, sub-wavelength lithography, surface defect detection, and developing tunable optical filters. Several methods were reported in the literature to solve the problem of scattering from cavities engraved in a metallic screen [1–4]. Although these methods are powerful they are not general enough to address cavities with general shapes or inhomogeneous and anisotropic fillings. In contrast, the methods based on finite mathematics such as finite element method (FEM) are highly suited when the gratings have arbitrary shapes and fillings [5–7]. This work briefly reviews the methods used to truncate the solution region of infinite structures while using FEM and highlights the inherent limitation in truncation the infinite structure using local boundary operators such as absorbing boundary condition (ABC) or perfectly matched layer (PML) in the context of the problem of scattering from infinite gratings. In fact we show that significant errors can be generated in the solution when using ABC or PML for grazing incidence even if the truncation boundary is receded appreciably. The error in field computation due to mesh truncation using ABC or PML in problem of scattering from a single cavity engraved in an infinite metallic screen is calculated by an accurate recently published finite-element based method and the mode matching technique.