A multi-beam rectifying metasurface (RMS) with polarization insensitivity and wide input power capability is presented. The proposed RMS consists of periodic dual-port energy harvesting units, a power-combining network, and a wide-input-power rectifier circuit. Orthogonal microstrip lines are integrated onto a regular dodecagonal metallic patch, enabling the dual-port design to capture incident waves at various polarization angles. Metallic vias transfer the harvested energy to a multi-beam power-combining network located on the underlying layer. By configuring specific amplitude and phase distributions, multiple beam directions can be synthesized, extending the angular coverage of incident waves. A wide-input-power rectifier circuit featuring impedance compression and harmonic suppression is also designed and connected to the power-combining network, enabling efficient DC power conversion across varying input power levels. A 6×6 RMS array integrated with a rectifier circuit operating at 5.8 GHz was fabricated and measured. Results demonstrate equivalent beam patterns at -45°, 0°, and 45° polarizations. The rectifier achieves over 50% efficiency across an input power range of 5–20 dBm, while the RF-DC peak efficiency of the RMS exceeds 70% at all three evaluated angles. The proposed RMS facilitates multi-directional energy harvesting for Internet of Things (IoT) sensor devices.

While many techniques have been developed for the design of different types of antennas, such as wire antenna, patch antenna, lenses, and reflectors, these cannot be said general-purpose strategies for the synthesis and design of antennas to achieve the performance characteristics specified by users. Recently, there has been an increasing need for the development of antenna design techniques because of the advent of 5G and a variety of space, defense, biological, and similar applications, for which a robust and general-purpose design tool is not to be developed. The main objective of this study is to take a look at antenna design from the field manipulation point of view, which has the potential to partially fulfill this need. We review the existing field manipulation techniques, including field transformation methods based on Maxwell’s and wave equations, point out some limitations of these techniques, and then present ways to improve the performance of these methods. Next, we introduce an alternative approach for field manipulation based on two-dimensional (2D) metasurfaces, and present laws of the generalized reflection and refraction that are based on 2D surface electromagnetics. Then, we explore how to overcome the limitations of conventional reflection and refraction processes that are strictly bounded by the critical angle. Finally, we provide some application examples of field manipulation methods in the antenna design, with a view on developing a general-purpose strategy for antenna design for future communication.

This paper presents an efficient algorithm to analyze the electromagnetic scattering from a 3-D object buried under a 2-D rough surface. The Poggio-Miller-Chang-Harrington-Wu-Tsai integral equation is implemented in the framework of the characteristic basis function method (CBFM). To expedite the solution, a new approach which utilizes a current-based physical optics (PO) method called the modified equivalent current approximation (MECA) is used for efficient calculation of the characteristic basis functions for the dielectric rough surface. Moreover, the adaptive cross approximation (ACA) is used to accelerate the generation of the reduced matrix during which the interaction between the rough surface and the object is rigorously taken into account. The proposed approach, referred to as CBFM-MECA-ACA, is shown to be particularly efficient when deriving statistical results using the azimuthal angular averaging method. In addition, the range of validity of the proposed algorithm is investigated to demonstrate that both far- and near-field quantities can be accurately derived under appropriate constraints. Finally, the numerical results are presented to show the performance and the versatility of the CBFM-MECA-ACA algorithm.

An accurate representation of the electromagnetic (EM) behavior of precipitation particles requires modeling of realistic complex geometry and a numerically efficient technique to calculate averaged scattering properties over multiple random target orientations. The discrete dipole approximation is commonly used to compute scattering and absorption by snow particles, because of its geometry flexibility and numerical low cost. However, this method becomes inefficient when the scattering quantities need to be calculated for a large number of orientations. To overcome this limitation, we apply, in this paper, a direct solver-based method, known as the characteristic basis function method (CBFM), to the modeling of scattering by randomly oriented and complex-shaped snow particles. This domain decomposition technique is based on the generation of a new set of basis functions adapted to the geometry of the scatterer in order to significantly reduce the numerical size of the EM problem. This enables us to use a direct solver for the resolution of the final compressed system of linear equations, which is better adapted for multiple excitation problems. When applied to numerically large snow particles, our CBFM-based model, named Numerically Efficient Scattering by Complex Particles, has been shown to yield good results, which compare well with those obtained with discrete dipole scattering, while providing a dramatic reduction in the CPU time.

An efficient electromagnetic model for the scattering analysis of targets placed in large natural environments is presented. A hybrid formulation combining volume and surface integral equations is used to describe forest environment (dielectric objects) in which metallic structures are present. A large part of the forest can be analyzed electromagnetically by using the characteristic basis function method, whose use enables us to simulate the problem at hand and significantly reduce the dimension of the linear system that needs to be solved.

A direct-solver based domain decomposition method is applied to efficiently compute orientationally averaged scattering efficiencies from complex-shaped ice pristine and aggregation. This numerically powerful method, known as the characteristic basis function method (CBFM), is based on the generation of a new set of basis function adapted to the geometry of the scatterer, in order to significantly reduce the numerical size of the EM problem. Being better adapted to multiple excitation problems, the CBFM enables us to achieve a significant reduction in CPU time in comparison to DDScat, a widely used implementation of the discrete dipole approximation (DDA), while maintaining a satisfactory level of accuracy.

In this paper, we present a novel procedure for an efficient and accurate electromagnetic simulation of microstrip circuits and printed antennas etched in layered media. The proposed approach, based on a new algorithm referred to herein as the equivalent medium approach (EMA), is applied for a rapid design of the preliminary desired circuit prototype. The illustrated technique yields reliable results and reduces the computational time in comparison with the conventional method of moments (MoM). Some examples that demonstrate the accuracy and the efficiency of the described procedure are included.

The paper by D. V. Thiel and R. Mittra, IEEE Trans. Geosci. Remote Sensing, vol.35, p.1357-62 (1997) is commented upon. They take part in the controversy of staked versus unstaked sensors to measure the horizontal electric fields above the Earth's surface. Their idealized computer model is most ingenious and the results are not disputed. Nevertheless, the present author raises a few issues, in which correction and clarification may be needed.

The paper by D.V. Thiel and R. Mittra, IEEE Trans. Geosci. Remote Sensing, vol.35, p.1357-62 (1997) is commented upon. The present author deals with the basis of the expression for the effective complex area of a horizontal electric dipole (HED) over a layered conductive half-space. The second related item deals with a basic flaw in an estimate of the error when the HED is lifted relative to the air/earth interface. The present author provides an additional analysis. In both cases the HED is oriented to have a maximum response.

The finite-difference time-domain (FDTD) technique has been used to model the one-dimensional (1D) surface impedance of a lossy Earth plane having discontinuities in two and three dimensions. Using a horizontal magnetic field aperture source located five cells from an absorbing boundary and 35 cells above the lossy Earth plane, the surface impedance was accurately modeled at a distance of /spl lambda//sub 0//5000 from the source using both grazing and normal incidence. The technique was validated by comparison with a number of two-dimensional (2D) analytical models. The surface impedance profile in the vicinity of a vertical conductive water filled shaft that extends from the Earth's surface to a conductive basement is presented. Unlike modeling in the frequency domain, a single FDTD solution yields accurate multi frequency surface impedance data providing a number of standard cell size constraints are met. For common Earth electrical constants, the FDTD approach is limited to frequencies above 500 Hz.

Using the finite-difference time-domain (FDTD) method, an electrically short, staked, grounded horizontal probe is shown to have an open circuit voltage directly related to the horizontal electric field at the Earth's surface providing the surface coupling is subtracted from the output. This result is valid not only for an infinitely deep Earth plane but also for one which is horizontally layered. The effective length of a staked probe is found to be dependent on the conductivity of the upper layer of the Earth, its depth, the length of the stakes, and also the frequency of measurement. The effect is significant at very low frequency (VLF) for ice, permafrost and dry sand-covered regions.

Asymptotic and hybrid methods are widely used to compute the Radar Cross Section (RCS) of objects that are large compared to the wavelength of the incident wave, and the objective of this paper is to present an overview of a number of these methods. The cornerstone of the asymptotic methods is the Geometrical Theory of Diffraction (GTD), which was originally introduced by J. B. Keller, and which represents a generalization of the classical Geometrical Optics (GO) by virtue of the inclusion of diffraction phenomena. After a presentation of the physical principles of GTD, we provide a description of its mathematical foundations. In the process of doing this we point out that GTD gives inaccurate results at caustics and light-shadow boundaries, and subsequently present a number of alternate approaches to dealing with these problems, viz., Uniform theories; Methods for caustics curves; Physical Theory of Diffraction; and Spectral Theory of Diffraction. The effect of coating perfectly conducting bodies with dielectric materials is discussed and hybrid methods, that combine the Method of Moments (MoM) with asymptotic techniques, are briefly reviewed. Finally, the application of GTD and related techniques is illustrated by considering some representative radar targets of practical interest.>

The results of using a general-purpose Maxwell solver to derive equivalent circuits for various components of an electronic package are illustrated. The package can be inserted in a SPICE-type circuit simulation program to investigate the electrical performance of the package. The finite-difference-time-domain (FDTD) algorithm is found to be best suited for this purpose, and is used exclusively to derive the results presented.>

A method for the time-domain simulation of multiconductor transmission lines with frequency-dependent conductor (skin effect) and dielectric losses is presented. The method is based on a traveling-wave solution of the transmission line equations in the frequency domain, which reduces to the conventional modal solution for lossless lines when no losses are present. Time-domain simulation for the lossy care is achieved by convolving the transmission line terminal voltage with describing time-domain input and transfer impulse responses for the multiconductor line. Careful formulation of the frequency-dependent conductor and dielectric losses assures causality in the transmission line responses. The numerical burden of discrete-time convolution is avoided by approximating the transmission line responses with exponential series. An implementation of the solution algorithm in SPICE is described. Examples are included for coupled lossy stripline and microstrip configurations.>

The authors discuss two partial differential equation (PDE) techniques, namely the finite difference (FD) method and the finite element method (FEM), for solving the problem of radar scattering by a body of revolution (BOR). The formulation of the BOR problem is based upon the use of the coupled azimuthal potentials (CAPs), introduced by M.A. Morgan et al. (1977), that allow one to reduce the vector field problem to the solution of two coupled scalar wave equations. An approach to FD/FEM mesh truncation is developed on the basis of a multipole representation for the CAPs in the asymptotic region. Numerical results are presented for some representative geometries to illustrate the application of the PDE methods and some observations regarding the comparative performance of the two methods are included.>

A number of representative techniques for analyzing frequency-selective surfaces (FSSs), which comprise periodic arrays of patches or apertures in a conducting screen and find important applications as filters in microwaves and optics, are discussed. The basic properties of the FSSs are reviewed and several different approaches to predicting their frequency-response characteristics are described. Some recent developments in the treatment of truncated, curved, and doubly periodic screens are mentioned and representative experimental results are included.>