Frequency Selective Surface Design Based On Fractal Structure

FSS is used in many fields such as stealth technology,radomes,antennas,etc.Combined with the self-similarity possessed by the fractal pattern,it is used as a periodic unit in FSS design,allowing it to form multi-frequency resonance.The focus of this paper is to improve and enhance the bandwidth absorption of FSS in the low frequency range in high temperature environment as well as to extend its absorption bandwidth,and to simulate and analyze the electromagnetic characteristics of FSS in the case of a single fractal pattern.The main topic of this paper is the practical application of fractal patterns in the design of frequency selective surfaces(FSS),with the aim of enhancing the bandwidth absorption level and expanding the absorption bandwidth of FSS in the low frequency range in a high temperature environment.Based on the consideration of high-temperature environment,the material used needs to meet its requirements as well.The first task is to simulate and analyze a single-layer FSS with a single fractal pattern,and the results show that the cross-fractal FSS made of copper reflects the multifrequency characteristics,but the bandwidth of each channel is small.The absorption bandwidth of the classical Minkowski fractal FSS in the high-frequency range is more outstanding,however,its absorption level in the low-frequency band is not considerable.Based on this situation,the Minkowski reference fractal FSS has been optimized and improved.The Minkoffs reference fractal FSS made of copper exhibits better absorption performance in all frequency bands and is insensitive to the incident angle and polarization.These findings provide new ideas and methods for the design and application of FSSs.This paper also investigates the different performances of Minkowski and triangular fractals made of copper and Minkowski and triangular fractals made of square resistance materials corresponding to frequency selective surfaces,even though they have a promising absorption bandwidth performance in the high frequency band domain,however,they have a lot of room for improvement in the low frequency band domain,so this paper proceeds to analyze an improved version of the Minkowski reference fractal.The analysis results show that the copper Minkoffs reference fractal FSS has better frequency characteristics than the cross fractal,and the absorption effect of FSS is significantly improved by using square resistance material.Finally,the paper points out that the fractal pattern has good symmetry,small cell size,and passivity for polarization and incident angle,all of which make it more promising for future use in FSS design.