Publication:

Diseño de una estructura plana reductora de la sección recta radar (RCS) basada en metamateriales

La aparicion del primer sistema radar hasta su posterior despliegue en la segunda guerra mundial (1939 - 1945) tuvo como consecuencia la necesidad de desarrollar los primeros sistemas antiradar, con la finalidad de evitar ser detectados por el frente enemigo. Tras la finalizacion de la sea guerra mundial hasta el dia de hoy, ambas tecnologias han continuado desarrollandose, denotando la gran importancia que tienen para el ambito militar. El objetivo de este proyecto se centra en el estudio de la reduccion RCS (Radar cross-section) a traves de dos estructuras basadas en Metasuperficies. [1]. Las Metasuperficies se pueden definir como metamateriales 2D, permitiendo controlar de manera flexible las amplitudes y las fases de las ondas reflejadas ya sea individualmente o simultaneamente. [2] En primer lugar, la primera estructura reductora de la RCS bajo estudio se ha analizado para incidencia de una onda plana en direccion normal y dos polarizaciones lineales en las direcciones Ix, Iy. Esta presenta una configuracion tipo Chessboard compuesta por elementos de codificacion “0” y “1” a traves de la rotacion de una figura S de 10º y 100º respectivamente, con la que se consigue rotacion de la polarizacion lineal y una diferencia de fase de 180º (mecanismo de difusion) de manera simultanea. Para la ampliacion de la banda de funcionamiento en la banda de ondas mmw a traves del mecanismo de absorcion, esta se ha combinado en conjunto con elementos tipo RFSS Square de dos capas con valor de impedancia 100 Ω/m y valores de tamaño RFSS (1 mm y 1.5 mm), en este caso no se ha obtenido el resultado esperado, obteniendo un FWB del 114.3 %. De esto modo se ha decidido realizar una optimizacion de los valores de RFSS de partida, dando con unos valores de tamano 1.3 mm y 3 mm, con los que se ha obtenido un FWB del 147% y con la que se consigue la ampliacion de la capacidad reductora RCS en la banda mmw. Por otra parte, se ha comprobado su buen funcionamiento para incidencia oblicua hasta θ =20º, obteniendo un FWB del 108.1 %. La segunda estructura reductora de la RCS bajo estudio se ha analizado para incidencia de una onda plana en direccion normal y dos polarizaciones lineales en las direcciones Ix, Iy. Esta presenta una configuracion tipo Array aleatoria compuesta por rotaciones de -135º, -90º, -45º y 135º de un anillo resonante dividido en forma de C, con la que se consigue rotacion de la polarizacion lineal y una diferencia de fase 180º (mecanismo de cancelacion de fase) de manera simultanea. Sobre esta se ha combinado un elemento absorbente tipo RFSS Square Ring, permitiendo ampliar la reduccion RCS en la banda K, aunque en el articulo se amplia hasta comienzos de la banda Ka, finalmente se ha obtenido

The appearance of the first radar system until its poster deployment in the Second World War (1939 - 1945) had as a consequence the need to develop the first anti-radar systems, in order to avoid being detected by the opposing front. After the end of the Second World War until today, both technologies have continued to develop, denoting the great importance they have for the military field. The objective of this project is focused on the study of RCS (RCS cross-section) reduction through two structures based on Metasurfaces. [1]. Metasurfaces which can be defined as 2D metamaterials flexibly control the amplitudes and phases of the reflected waves either individually or simultaneously. [2] In the first place, the first reducing structure of the RCS under study has been analyzed for the incidence of a plane wave in the normal direction and two lineal polarizations in the Ix, Iy directions. This presents a Chessboard type configuration composed of coding elements “0” and “1” through the rotation of a figure S of 10º and 100º respectively, with which lineal polarization rotation and 180º phase difference are obtained (diffusion mechanism) simultaneously. To extend the operating band in the mmw waveband through the absorption mechanism, it has been combined with elements of the RFSS Square type with two layers with impedance value of 100 Ω/m and RFSS size values of (1 mm and 1.5 mm), in this case the expected result has not been obtaining an FWB of 114.3 %. In this way, it has been decided to optimize the initial RFSS values, giving values of size 1.3 mm and 3 mm, with which an FWB of 147% has been obtained and with which the enlargement of the RCS reducing capacity in the mmw band. On the other hand, its good performance for oblique incidence up to θ = 20o has been verified, obtaining a FWB of 108.1%. The second reducing structure of the RCS under study has been analyzed for the incidence of a plane wave in the normal direction and two linear polarizations in the Ix, Iy directions. This presents a random array type configuration composed of -135º, -90º, -45º and 135º rotations of a resonant ring divided into a C-shape, with which the rotation of the linear polarization and a 180o phase difference is achieved (mechanism phase cancellation) simultaneously. On this, an absorbent element type RFSS Square Ring has been combined, allowing to extend the RCS reduction in the K band, although in the article it is extended until the beginning of the Ka band, finally an FWB of 41.75% has been obtained. From the second structure under study, another Chessboard type structure has been derived based on a reconfiguration of the resonant rings divided into a C-shape, composed of 0º and 90º rotations. This structure also allows the rotation of the linear polarization and the obtaining of a phase difference of 180º. The RFSS Square Ring element has been combined on top of this, allowing the reduction band to be extended mainly in the K band, obtaining an FWB of 74.7%, The manufacturing process of the Square and Square Ring type RFSS elements has been detailed, using carbon composite resistive inks, using the Silk Printing method. An improvement proposal has been made by applying the new absorption mechanism through the Square type RFSS elements, with a size of 1 mm and an impedance value of 100 Ω/m’, on a Chessboard type RCS structure made by the group of antennas and microwave, which is based on the use of AMC elements to obtain a 180º phase difference (phase cancellation) through their corresponding frequency slopes. In this case, due to the overlapping of operating bands of the phase cancellation and absorption mechanisms, the performance of the structure is affected, so that this expected improvement has not been obtained.