Programa del congreso

A software has been implemented that applies the spectral-domain Method of Moments (spectral MoM) to the analysis of periodic multilayered structures with a number of metallized interfaces alternating patches and apertures. The Non-Uniform Fast Fourier Transform (NUFFT) is used to obtain the Fourier transform of the basis functions in the case where the periodic grids are skewed, which makes it possible the analysis of non-rectangular periodic lattices with tightly packaged elements. The in-house software is used to design a fifth-order frequency selective surface (FSSs) made of hexagonal patches and apertures with 35% of bandwidth. Our design results are compared with CST results, and excellent agreement is found. The in-house software turns out to be around 13 times faster than CST, which makes it very convenient for full-wave electromagnetic optimization.

Here we analyze a periodic circular waveguide loaded with transversal holey metallic plates. Specifically, we study the effects of higher symmetries when the holes have an elliptical shape. It is shown that the position of the center as well as the orientation of the elliptical holes strongly determine the bandwidth and characteristics of the passbands. In general, it is observed that holes in a higher-symmetric configuration produce a wider bandwidth with less dispersion. We also studied the case of two different interleaved periodicities with different symmetries: conventional, single-glide, and double-glide. Single and double glide symmetries present a similar behavior as their conventional counterpart, namely, there appear two near passbands. Additionally, two 4-fold twist-symmetric structures are studied. When the minor semi-axis of the elliptical holes is directed along the waveguide radial direction, the mode propagates in a narrow band and shows both forward and backward characteristics. On the other hand, when the major ellipse's semi-axis is located along the radial direction, a low-dispersive mode propagates in a wide frequency band.

To design and characterize radio environments with metasurfaces, it is necessary to know the scattering properties of finite-size anomalously reflecting (phase-gradient) metasurfaces. Recently, different approaches have been proposed to tackle the problem.

In this presentation, we will present a comparison between alternative analytical models.

We will first derive a general formulation for the far-field scattering of reflective metasurfaces based on the Huygens principle. Then we will specify the assumptions of known models. The first model that we will study is based on the assumption that at each point of the metasurface the reflected field equals the incident field multiplied by a controllable reflection coefficient. Then we will analyze the same structure with an analytical model based on the use of macroscopic reflection coefficients following the theory of diffraction gratings. Finally, we will numerically analyze the structure and compare the results.

A novel technique to design Fabry-Pérot antennas with non-homogeneous PRS is described. It takes advantage of a transmission line circuit model to efficiently obtain all necessary unit cell designs that satisfy the cavity resonance condition. This approach allows an increase in directivity for a given footprint without decreasing the bandwidth. Some design examples are presented, showing the evolution from a simple single-layer PRS to a non-homogeneous two-layers one. Through electromagnetic simulations, the latter one achieves an increase of about 3 dB in directivity while maintaining the bandwidth. This way, the gain-bandwidth product is improved from a value of 5 to almost 9, effectively raising the antenna efficiency.

The concept of Gap Waveguides and suppression of modes propagating between a Perfect Electric and Perfect Magnetic Conducting is applied to Coplanar Waveguides to propose a new low-loss, low-dispersion transmission line. Three different versions of the line are proposed and compared among themselves and other typical CPW implementations. The main theory behind this concept and Finite Element simulations are provided to support and validate the idea. A prototype is currently being fabricated and experimental validation is expected in the forthcoming months