Wideband stopping two frequency selective surfaces design

In 1919 G. Marconi and C. S. Franklin made an invention that is known "Reflector for Wireless Telegraph and Telephone" which is called frequency selective surface (FSS) for the first time in history, contributed to our life with lots of help. When it comes to the 1960s, the success achieved with the use of frequency selective surfaces in military intelligence units has come to such an extent that it can not be ignored. Periodically applied to land, air and sea platforms, these structures exhibited low pass, high pass, band pass or band stop characteristics for certain frequencies and assumed the role of electromagnetic filters. Many successes have been achieved, especially through platforms that can not be detected by target detection systems. Thanks to the developing technology, these structures, which are used effectively in many areas such as wireless communication systems, radars, microwaves, by the geometry and arrangement of the unit cell, provides the reflection or transmission of the incoming electromagnetic wave. Millimeter wave, which is between 30 GHz and 300 GHz frequency band, can be used for high-speed broadband access. It has been increasingly important in the field of wireless communications, radar, remote sensing technology and radio astronomy. This study aims to propose a new single layered ultrawide-band (UWB) frequency selective surface (FSS) for U (40-60 GHz) and V (50-75 GHz) band milimeter-wave applications. Proposed FSS structure consists of a conventional square loop and four separate lines added each side of the square loop. It seems like lines rotated 90 degrees on face to obtain F-shape on single layered. Dielectric substrate is made by low-cost FR4 loss-free. For designing the FSS structure's transmission coefficient obtained by CST Microwave Studio commercial software. Transmission coefficients are obtained and it has been observed that the proposed design exhibits a broad stop-band of 42.21 GHz, from 39.59 to 81.80, The maximum rejection performance with normal incidence is measured as -61.10 dB at 60.90 GHz. Kesavan A. and colleagues designed a band of -10 dB rejection between 40-70 GHz frequency with a bandwidth of 30 GHz in the interval, but F-shaped UGB structure provides a bandwidth of 42.21 GHz between frequencies 39.59-81.80 GHz at -10 dB rejection performance, giving more frequency bandwidth reflection than the structure designed by Kesavan A. and colleagues. The single layered miniaturized geometry and wide stop band nature are the advantages of this FSS. The proposed FSS filter can be used in numerous mm-wave applications where system protection is required. In the second part, a new ultra wideband FSS design presents including C, X and Ku bands. The F shape is applied on one side and on the other side II shape inside of three square loop is applied of dielectric layer for analysing the effectiveness of the frequency selective surface. This FSS structure is aimed to band-stop at three band. The aims of the study is proposed a new single layered ultrawide-band frequency selective surface for C-band (4-8 GHz), X-band (8-12 GHz) and Ku-band (12-18 GHz) wave applications. Front side of FSS structure proposed consists of a three nested square loop with outside of the II shape and seems like lines rotated 90 degrees on face to obtain F-shape on single layered. A numerical analysis of transmission properties of the designed UWB FSS is performed through simulations using CST Microwave Studio commercial software. Transmission coefficients are obtained and it has been observed that the proposed design exhibits a broad stop-band of 16.92 GHz, from 3.05 to 19.80. The maximum rejection performance with normal incidence is measured as -71.33 dB at 16.35 GHz. At the aimed three band of -10 dB rejection performance for the Sarika and friends designed structure between 5.2-15.6 GHz with 10.4 GHz bandwidth. New F and II shape UGB structure, at -10 dB rejection performance, provides a bandwidth of 16.92 GHz between frequencies 3.05-19.97 GHz. So that new shape of F and II provides more frequency bandwidth reflection than the structure designed by Sarika and colleagues. The two sided layer miniaturized geometry and provide wide stop band nature so that this structure has an advantages of in FSS structure. The prototype of the structure designed as II and F was produced and measurement results were obtained in laboratory environment with 1-18 GHz frequency bandwidth. When the results are examined; It was observed that the reflection frequency bands formed by the simulation and the measurement results were very compatible with each other. When system needs protection or rejection at the three band; FSS filter can be used in numerous mm-wave applications where system.