Investigation of polarizer design with grooves of arbitrary profile by the coordinate transformation method for the ECRH system

The coordinate transformation method is widely utilized in the design of polarizers. However, the numerical solution of polarizers with discontinuous structures, such as rectangular grooves, poses a challenge for the coordinate transformation method. To solve this problem, we expand the profile functions of the grooves with the Fourier series by considering the periodic groove structure. In this way, the discontinuous profile can be replaced by its truncated Fourier representation. A code based on the Fourier expansion of grooves of arbitrary profile is developed, and three sets of polarizers with different grooves are designed. The calculation results obtained from our code align well with those derived from the integral method and low -power test results of the designed polarizers. Therefore, it is indicated that our proposed method can provide an alternative option for polarizer design with arbitrary groove shapes.