Research On The Processing Method Of Non-developable Frequency Selective Surface

Frequency Selective Surface (FSS) is a two-dimensional periodic structure with the features of frequency filtering, which's physical structure is dominated by the supporting substrate and an array of thin metal film. Due to its electromagnetic transmission characteristics, FSS is widely used in aviation and aerospace fields, which makes it possible for target carrier to get hidden or filered in electromagnetic field. However, the manufacturing of FSS is remaining in the research level, the engineering application will need more further study. In this paper, "Jerusalem" cross-unit FSS is the main object of study, in which studys its electromagnetic simulation and analyzes the rule of transmission characteristics with its shape parameter variation; Via the mapping relations between the surface and the plane FSS, hemispherical surface and approximate tapered surface FSS is modeled in CAD three-dimensional software; After the analysis of the pros and cons of different surface processing methods, laser etching method is used to get hemispherical surface FSS with analysis of error factors.Firstly, according to the shape characteristics of "Jerusalem" FSS, this paper take advantage of electromagnetic simulation software HFSS to get planar structure FSS simulated and analysize the variation rlue of electromagnetic properties with the change of shape parameters. Based on the literature, the cell edge length a, the cross length b as well as slit width w are chosed to change along 2% of its design value with electromagnetic simulation and then get these result data graphed in Origin.Secondly, according to the FSS's electromagnetic properties about shape parameter, the mapping relations between non-developable surfaces and FSS are determined which makes it tangent between the FSS and surfaces. With that form, this paper completes the hemispherical and Approximate tapered surface FSS three-dimensional model.Thirdly, this article analysizes the shape error of different processing method, that is CNC machining, approximate expanding and laser etching. And then based on principle ofl aser etching, the experiment uses the laser to etch surface by the way of layer by layer scanning, and observes the processing structure of two projection methods.Finally, this paper deeply analysizes the error and variation of hemispherical FSS in laser etching. With the rule between transmission characteristics and its shape parameter variation, the laser ecthing processing method is further optimized to make the shape error fluctuate in the standard value's both sides which makes the FSS more accurate. In addition, this paper analyzes the relationship between projection beam path of dimensional trajectory and processing shape parameter error and calculate the matrix perspective projection of dimensional trajectory in theory. In this way, the mathematical model between surface FSS structure and FSS dimensional trajectory is completed.