In this paper, a double V-shaped metasurface that can efficiently convert linear polarizations of electromagnetic (EM) waves in wideband is proposed. Based on the electric and magnetic resonant features of a single V-shaped particle, four EM resonances are generated in a V-shaped pair, leading to significant bandwidth expansion of cross-polarized reflections. The simulation results show that the proposed metasurface is able to convert linearly polarized waves into cross-polarized waves in ultrawideband from 12.4 to 27.96 GHz, with an average polarization conversion ratio (PCR) of 90%. The experimental results are in good agreement with the numerical simulations. Compared to published designs, the proposed polarization converter has a simple geometry but an ultrawideband and hence can be used in many applications, such as reflector antennas, imaging systems, remote sensors, and radiometers. The method can also be extended to the terahertz band.

Ultrawideband and High-Efficiency Linear Polarization Converter Based on Double V-Shaped Metasurface

The finite-difference time-domain (FDTD) method is arguably the most popular numerical method for the solution of problems in electromagnetics. Although the FDTD method has existed for nearly 30 years, its popularity continues to grow as computing costs continue to decline. Furthermore, extensions and enhancements to the method are continually being published, which further broaden its appeal. Because of the tremendous amount of FDTD-related research activity, tracking the FDTD literature can be a daunting task. We present a selective survey of FDTD publications. This survey presents some of the significant works that made the FDTD method so popular, and tracks its development up to the present-day state-of-the-art in several areas. An "on-line" BibT/sub E/X database, which contains bibliographic information about many FDTD publications, is also presented. >

A selective survey of the finite-difference time-domain literature

A 1-18-GHz broadband double-ridged horn antenna with coaxial input feed section is investigated. For the ridged horn antenna it is found that the radiation pattern, contrary to common belief, does not maintain a single main lobe in the direction of the horn axis over the full frequency range. Instead, at frequencies above 12 GHz, the main lobe in the radiation pattern starts to split into four large side lobes pointing in off-axis directions with a dip of up to 6 dB between them along the main axis. Although this type of horn is the preferred test antenna, which is in common use for over four decades, no explanation for this unwanted behavior was found in the open literature. To investigate this phenomenon in detail, a method of moments approach has been adopted to simulate the complete antenna system. The simulations are in good agreement with the measurements over the 1-18-GHz operational bandwidth and indicate that the use of this type of horn antenna in EMC applications remains questionable.

Analysis and Simulation of a 1-18-GHz broadband double-ridged horn antenna

The wave concept iterative process method (WCIP) is presented for full wave investigation of a microwave structure on inhomogeneous substrate. These structures can be exploited to achieve a high performance due to their versatility, which can reduce manufacturing cost, size, and weight. Using the spectral operator in the WCIP method permits to resolve this inhomogeneous problem. The use of the spectral operator keeps the advantages of the 2D mesh of the circuit plan. Two different examples are studied; the dispersion characteristics of a microstrip transmission line on inhomogeneous substrate and a microstrip T-resonator on a low temperature Co-fired ceramic (LTCC) with embedded vertical air cavities. Compared with measurement and the finite different method, the present technique is found to be efficient with 2D analysis and a required low memory. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.

A 2D design and modeling of micro strip structures on inhomogeneous substrate

This letter describes a new design of dual-polarized broadband horn antennas. The bandwidth of the designed horn antenna is from 2 to 26.5 GHz. A novel coaxial line to quadruple-ridged waveguide transition is introduced to improve the return loss performance of the horn antenna. Measured results for VSWR, isolation, gain, and radiation pattern of the designed horn antenna are presented.

A new dual-polarized broadband horn antenna

An extension of the finite difference time domain is applied to solve the Schrodinger equation. A systematic analysis of stability and convergence of this technique is carried out in this article. The numerical scheme used to solve the Schrodinger equation differs from the scheme found in electromagnetics. Also, the unit cell employed to model quantum devices is different from the Yee cell used by the electrical engineering community. A bound for the time step is derived to ensure stability. Several numerical experiments in quantum structures demonstrate the accuracy of a second order, comparable to the analysis of electromagnetic devices with the Yee cell.

/pdf/analysis-of-the-finite-difference-time-domain-technique-to-2mrp39u1xe.pdf

Analysis of the finite difference time domain technique to solve the Schrödinger equation for quantum devices

The finite-difference time-domain (FDTD) method is applied to study the performance of E-plane sectoral horn antennas designed for broad-band applications. These antennas (proposed for 6-18 GHz phased arrays) have a large bandwidth, and they are easily array integrated. These antennas have a highly complicated geometry that is modeled using a polygonal approximation in the curved boundaries. Perfect matched layers (PMLs) combined with first-order absorbing boundaries are employed to simulate the free-space environment in the FDTD mesh.

FDTD analysis of E-sectoral horn antennas for broad-band applications

The frequency dependence of the characteristic impedance of microstrip lines has been investigated by many authors using 3D-FDTD formulations. In the present letter, a two-dimensional FDTD scheme is used to calculate both the propagation constant and the characteristic impedance of the fundamental quasi-TEM mode in a microstrip which, in fact, is a hybrid mode. Because of the substantial reduction of computer resources required for the calculations, this method can be used as a design tool. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 58–60, 1997.

Calculation of the characteristic impedance of microstrips using a full‐wave 2‐D FDTD scheme

The finite-difference time-domain method in general curvilinear coordinates (FDTD-GCC), or nonorthogonal FDTD, permits the analysis of arbitrary curved structures with the use of a conformal mesh. The analysis of near fields in the proximity of a thin curved dielectric sheet is a difficult task; then, ray tracing techniques and spectral numerical techniques are usually employed in the analysis of radomes. In this paper, the FDTD-GCC is modified to account for the analysis of thin curved dielectric sheets. The contravariant electric field normal to the sheet is split in two subcomponents, and new nodes are introduced where the thin sheet is located. New updating equations are inserted in the calculation of contravariant field components. The utility of the proposed technique is demonstrated in the analysis of two cylindrical radomes, the first having four not centered dipoles and the second with a centered dipole. The thickness of the radomes was 0.035-0.026 wavelengths at the central operating frequency.

Modeling of thin curved sheets with the curvilinear FDTD

A finite-difference time domain scheme for the analysis of H-plane waveguide discontinuities is described. The two-dimensional treatment of this kind of discontinuities and the use of a non-monochromatic excitation allow us to develop an efficient algorithm with a low demand of computer resources. The method is tested by comparing the numerical results for a right corner bend and a T-junction, the choice of the absorbing boundary conditions is discussed for each case.

Analysis of H-plane waveguide discontinuities with an improved finite-difference time domain algorithm

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