The Simulation And Design Of Frequency Selective Surface With Fractal Pattern

Frequency selective surface(Frequency Selective Surface, referred FSS) has been widely used in the fields of the antenna, radome and stealth technology. The fractal pattern has self-similar characteristic, so we use fractal pattern as a unit cell to design the frequency selective surface. It has a characteristic of multi-frequency resonance. This paper focuses on broadening the absorbing bandwidth of frequency selective surface, improving and optimizing absorbing bandwidth of frequency selective surfaces in the low-frequency region(2 GHz-6 GHz). With this idea, the simulation and design of frequency selective surface with fractal pattern has been studied.In this paper, the electromagnetic properties of frequency selective surfaces with single fractal pattern have been studied. In the study of single-layer frequency selective surface with single fractal pattern, the brass frequency selective surfaces with cross fractal exhibit multi-frequency characteristic, however its bandwidth isn't well. The use of sheet resistance expands the absorbing bandwidth at high-frequency band. Compared the absorption bandwidth of second-order cross fractal FSS with sheet resistance to brass cross fractal FSS at-10 dB, its bandwidth extends from 4 GHz-4.5 GHz to 7.5 GHz-17.4 GHz. The standard Minkowski fractal FSS with sheet resistance has good absorbing bandwidth in the high frequency region, but absorbing properties in the low frequency region is not ideal, so based on the standard Minkowski fractal,I have made improvements on the basis to propose a nonstandard Minkowski fractal. In order to broaden absorption bandwidth at 2 GHz-6 GHz, I carry on doing the research on multi-layer FSS.The design of multi-layer FSS with single fractal pattern makes absorption peaks moving to low frequency, broadening the absorbing bandwidth in low-frequency region, however it does not cover 2 GHz-6 GHz.Due to the complex of FSS with a variety of patterns has the effect to improve absorbing bandwidth, so this paper studies complex of FSS with a variety of patterns in order to achieve the design goal:-6 dB absorption in 2 GHz-6 GHz. First complex of nonstandard Minkowski fractal and cross fractal or Jerusalem cross cross-type fractal with FR4 in multi-layer fractal FSS have been researched. Complex of a variety of fractal patterns optimizes absorbing bandwidth in low-frequency region, by adding unit cell of sheet resistance, further I obtain-6 dB broadband absorption from 2.2 GHz to 7.9 GHz. Between the air layer and FSS, the dielectric plate acts as a matching layer, the use of a relatively smaller dielectric constant medium can achieve better impedance matching, and thus it can optimize absorbing bandwidth. Then, this paper discusses complex of nonstandard Minkowski fractal and Jerusalem cross type fractal FSS with F4 B. Its-6 d B absorption band covers 2.1 GHz-8.9 GHz, and it reaches expected goal. This shows that as the dielectric layer, F4 B optimizes the absorption bands. Fractal FSS has small size cells and well symmetry, so it is not sensitive to the angle of oblique incidence and polarization.Baesd on fractal and complex fractal pattern as a unit in FSS, it is good to improve broadband absorption properties of frequency selective surface in the low-frequency region, and it is not sensitive to the angle of oblique incidence and polarization. Frequency selective surface with fractal patterns is valuable in project.