Field Synthesis with Azimuthally-Varying, Cascaded, Cylindrical Metasurfaces using a Wave Matrix Approach

In recent years, there has been extensive research on planar metasurfaces capable of arbitrarily controlling scattered fields. However, rigorous studies on conformal metasurfaces, such as those that are cylindrical, have been few in number likely due to their more complex geometry. Here, wave propagation in cascaded cylindrical structures consisting of layers of dielectric spacers and azimuthally-varying metasurfaces (subwavelength patterned metallic claddings) is investigated. A wave matrix approach, which incorporates the advantages of both ABCD matrices and scattering matrices (S matrices), is adopted. Wave matrices are used to model the higher order coupling between metasurface layers, overcoming fabrication difficulties associated with previous works. The proposed framework provides an efficient approach to synthesize the inhomogeneous sheet admittances that realize a desired cylindrical field transformation. Design examples are reported to illustrate the power and potential applications of the proposed method in antenna design and stealth technology.Comment: 13 pages, 14 figures. This work has been submitted to the IEEE for possible publicatio

A Realistic Coaxial Feed for Cascaded Cylindrical Metasurfaces

In this letter, a realistic coaxial feed is integrated into the design of cascaded cylindrical metasurfaces. This is in contrast to the fictitious current source that is often reported in literature. The S-matrix of the coaxial feed is obtained by way of the mode-matching technique, which is subsequently combined with the S-matrix of the cascaded cylindrical metasurfaces to account for the interaction between the feed and metasurfaces. The integration of a realistic feed into the design process enables practical cylindrical-metasurface-based devices.Comment: 5 pages, 4 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Power link budget for propagating Bessel beams

International audienceThe power link budget for a system that transmits and receives propagating Bessel beams is studied. The transmitter and receiver are separated by a distance D and consist of leaky radial waveguides. Full-wave simulations are used to compute the admittance-matrix representation of the system. The resonances of the coupled transmitter and receiver are then derived using classical network theory. For comparison purposes, a second configuration with its transmitter and receiver connected by a circular waveguide is considered. In contrast to the open system, such a configuration is closed and does not radiate. It is found that within the non-diffractive range of the Bessel beam, both closed and open systems exhibit the same resonances within an error of 0.6%. Calculations show that the power efficiency of the open system can exceed 85% within the non-diffractive range. The proposed system may find application in areas such as wireless power transfer, near-field communication and non-destructive evaluation

Inverse Design of Multi-input Multi-output 2D Metastructured Devices

In this work, an optimization-based inverse design method is provided for multi-input multi-output (MIMO) metastructured devices. Typically, optimization-based methods use a full-wave solver in conjunction with an optimization routine to design devices. Due to the computational cost this approach is not practical for designing electrically-large aperiodic metastructured devices. To address this issue, a 2-D circuit network solver using reduced order models of the metastructure's unit cells is introduced. The circuit network solver is used in conjunction with a gradient-based optimization routine that uses the adjoint variable method to solve large-scale optimization problems like those posed by metastructured devices. To validate the inverse design method, a planar beamformer and an analog signal processor for aperture field reconstruction are designed and validated with full-wave simulations.Comment: 11 pages, 12 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Modelling cascaded cylindrical metasurfaces using sheet impedances and a transmission matrix formulation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163795/1/mia2bf00746.pd

Unit Cell Design for Aperiodic Metasurfaces

A technique is presented for the design of printed unit cells in aperiodic metasurface environments. The method begins with a solved matrix equation governing electromagnetic scattering from a homogenized metasurface design. The matrix equation is used to find the local, inhomogeneous electric field exciting a printed-circuit unit cell geometry. The local field is then impressed onto the printed circuit geometry and the induced surface current numerically computed. The computed surface current is sampled at the matrix equation discretization. The matrix equation is then used to compute the electric field scattered by the printed-circuit unit cell onto its neighbors using the sampled current in place of the current of the original homogenized unit cell. The printed circuit geometry is optimized to scatter the same field as the homogenized unit cell when excited with the local electric field computed. Two design examples are provided. Both a finite-sized, wide-angle reflecting metasurface, and a metasurface reflectarray designed to scan and collimate an incident cylindrical wave, are realized with printed-circuit unit cells using the proposed approach. It is shown that the local periodicity approximation cannot be used to accurately design the unit cells of either finite-sized metasurface