Study of the characteristics of a modal filter with different periodic profiles of the coupling region

Improvement of protection against ultrashort pulse using modal filters (MF) is considered. A method for calculating the difference of the modes delays through the frequency characteristics without finding the time response at the MF output is proposed. On example of the interdigital, L-shaped and spiral structures simulation, the possibility of increasing the difference of the modes delay due to the application of the periodic profile of the coupling region is considered. The influence of a covering layer with a high dielectric constant in MF on the behavior of the frequency characteristics and the value of the difference of the modes delays is shown. The results showed the expediency of using the periodic profile of the MF coupling region in combination with inhomogeneous dielectric filling.