Showing papers by "Eva Rajo-Iglesias published in 2019"

Roadmap on metasurfaces

Abstract: Metasurfaces are thin two-dimensional metamaterial layers that allow or inhibit the propagation of electromagnetic waves in desired directions. For example, metasurfaces have been demonstrated to p ...

Parametric Study of 3D Additive Printing Parameters Using Conductive Filaments on Microwave Topologies

Abstract: This paper presents a parametric study of classical additive 3D-printing settings for use on conductive filaments in applications for high-frequency topologies. First, a wideband characterization was conducted, printing a microstrip transmission line using a conductive filament with variations of typical 3D-printing settings, such as layer height, infill percentage, and infill pattern. The measurement results show a dependence on the high-frequency transmission parameters with respect to the infill percentage and the infill pattern. Finally, two antennas were 3D-printed using conductive material, a microstrip patch, and a low-weight pyramidal horn antenna. The results for the patch agree with the losses found on the line measurements, while the low-weight pyramidal horn exhibits no major differences compared with its equivalent antenna, made using perfect conductors.

$Ka$ -Band Fully Metallic TE 40 Slot Array Antenna With Glide-Symmetric Gap Waveguide Technology

Abstract: Gap waveguide has recently been proposed as a low-loss and low-cost technology for millimeter-wave components. The main advantage of the gap waveguide technology is that the microwave components can be manufactured in two metallic pieces that are assembled together without electrical contact. The leakage through a thin air gap between the two pieces is prevented by a 2-D periodic structure offering an electromagnetic bandgap (EBG). This EBG is conventionally implemented with metallic pins. Here, we propose the usage of a holey glide-symmetric EBG structure to design a $4\times 4$ slot array antenna that is fed with a TE40 mode. The TE40 excitation is designed based on a TE10–TE20 mode converter whose performance is initially evaluated by radiation pattern measurements. The final antenna, the $4\times 4$ slot array antenna, was manufactured in aluminum by computer numerical control (CNC) milling. The antenna has a rotationally symmetric radiation pattern that could find application as a reference antenna as well as for 5G point-to-point communications.

Holey Metasurface Prism for the Reduction of the Dispersion of Gap Waveguide Leaky-Wave Antennas

Abstract: Leaky-wave antennas are dispersive, meaning that the direction of maximum radiation is a function of frequency. This behavior, called “beam squinting effect” can be reduced by introducing a dispersive metamaterial prism. In this letter, a holey metasurface prism is combined with a leaky-wave antenna in gap waveguide technology. The dispersion characteristics of the hole unit cell are studied in order to achieve the reduction of the main beam steering aiming to $\pm 1^{\circ }$ or less variation. A prototype designed at the Ka -band is measured and compared with the simulation results.

Radial Line Slot Antenna Design With Groove Gap Waveguide Feed for Monopulse Radar Systems

Abstract: Radial line slot arrays (RLSAs) are well suited to be used in monopulse radar systems. The excitation of the sum and difference patterns can be achieved by the design of simple feeds as shown in this paper. In this work, a feed system based on the use of a cavity made in groove gap waveguide technology (GGW) is presented. The design is made at 24 GHz but can be easily scaled to higher frequencies as the technology is contact-less and fully made in metal. A good isolation between the sum and difference ports together with a good matching of the two of them is obtained. The radiation patterns of the manufactured antenna are also in good agreement with the simulated ones.

Analysis of Periodic Structures Made of Pins Inside a Parallel Plate Waveguide

Abstract: In this work, we have analyzed different versions of periodic structures made with metallic pins located inside a parallel plate waveguide (PPWG), varying the symmetry and disposition of the pins. The analysis focuses on two main parameters related to wave propagation. On one hand, we have studied how the different proposed structures can create a stopband so that the parallel plate modes can be used in gap waveguide technology or filtering structures. On the other hand, we have analyzed the dispersion and equivalent refractive index of the first propagating transverse electromagnetic mode (TEM). The results show how the use of complex structures made with pins in the top and bottom plates of a PPWG have no advantages in terms of the achieved stopband size. However, for the case of the propagating mode, it is possible to find less dispersive modes and a higher range of equivalent refractive indices when using double-pin structures compared to a reference case with single pins.

Design of a Transverse Slot Array in Groove Gap Waveguide using Horns at 28 GHz Band

Abstract: We design an array of transverse slots cut out from the broad wall of a groove-gap waveguide, with periodic spacing between slots of a guided wavelength at 28 GHz that is centered about an important millimeter-wave band. External horns are brought upon to address the problem of grating lobes. The simulations have been carried out for operation in the designed frequency band from 27.676 to 28.652 GHz while preserving the conditions for port matching. This antenna solution lends itself to many applications within this millimeter-wave band.

Empirical Rates Characterization of Wearable Multi-Antenna Terminals for First-Responders

Abstract: Empirical characterization of the achievable rates for a wearable multi-antenna terminal shows the potential advantages of deploying a large number of antennas at the user end. We focus on the challenges and requirements of the broadband communication in future emergency communication systems, specifically addressing the outdoor–to–indoor propagation scenario, where the first responder is within an underground area such as a garage or basement. The measurement campaign undertaken characterizes the flat fading multiple-input multiple-output (MIMO) channel matrices at 3.5 GHz for a maximum of $M=30$ antennas deployed at the base station (BS), and $N=12$ wearable antennas at the user. The achievable rates are obtained for two transmission strategies that account for the different levels of channel knowledge. In both cases, all the MIMO processing is carried out at the BS.

Array of stacked leaky wave antennas based on gap waveguide technology

Abstract: An array of leaky wave antennas is presented. To create the array, leaky wave antennas in gap waveguide technology are stacked. The distance between the array elements, and the feeding network are studied to achieve maximum directivity and to avoid side effects that reduce the efficiency of the design. The aiming band is that of 92-96 GHz, and the directivity enhancement using an array of four stacked leaky wave antennas is 5 dB, reaching 25 dB, in comparison to the single antenna directivity of 19.9 dB.