Desenvolvimento de um absorvedor inspirado na forma de Oxalis tetraphylla utilizando metassuperfície e superfície seletiva em frequência.

Abstract

This work presents a novel absorber structure of the absorb/transmit type, inspired by the geometry of the Oxalis tetraphylla plant. The absorber is composed of an effective medium metasurface combined with a patch-type Frequency Selective Surface (FSS), which replaces the traditional ground plane used in conventional metasurface absorber designs. The first phase of the project involves the development of an FSS designed to operate at 1.6 GHz, 2.5 GHz, and 3.5 GHz. Experimental results indicate resonance frequencies at 1.62 GHz, 2.47 GHz, and 3.43 GHz. The FSS demonstrates polarization independence, angular stability for incident angles up to 30°, and spaced frequency bands with frequency ratios of 1.52 and 1.39, both below 2. In the second phase, diagonal slots are added to the geometry to enhance electromagnetic absorption and optimize impedance matching. This design offers greater flexibility, improved utilization of the unit cell area, and a more precise tuning of the multiband response at closely spaced frequencies. A prototype of the absorber, fabricated as a 5 × 5 array of unit cells with total dimensions of 260 mm × 260 mm, was tested in the 1 GHz to 4 GHz range at the GTEMA/IFPB laboratory. Measurements were carried out using a vector network analyzer and ultra-wideband horn antennas. The absorber achieved peak absorption levels of 98.66%, 99.67%, and 98.62% at 1.65 GHz, 2.4 GHz, and 3.51 GHz, respectively. The frequency absorption ratios were 1.45 (between the second and the first) and 1.46 (between the third and the second), remaining below 2, thereby confirming the achievement of closely spaced absorption bands. The proposed structure exhibits polarization independence, angular stability for oblique incidences up to 30°, and efficient operation in both the S and C bands. In the S band (e.g., 1.65 GHz), it is suitable for satellite communications, GPS, and military applications, while in the C band, it is ideal for Wi-Fi networks (2.4 GHz) and 5G systems (3.51 GHz).