Modal Filter Based on a Microstrip Line With Two Side Conductors Grounded at Both Ends

This article presents a modal filter (MF) based on a microstrip line with two side conductors grounded at both ends. New analytical expressions for calculating the time response in such a structure are given. For their validation, an MF prototype was made and the transmission coefficient was measured in the frequency range from 0 to 12 GHz. In addition, the full-wave electrodynamic simulation and the analysis based on the transmission line theory were carried out. The MF frequency responses were converted into time domain responses in the Advanced Design System. At the MF output, the responses to an ultra-wideband pulse, a high-frequency damped sinusoid, and a sinusoid with Gaussian modulation were analyzed. The results for the analytical model are in good agreement with the results of measurements and simulations by the two approaches. It was experimentally proven that the structure under study provides the protection of electrical circuits from different types of interference by separating them in time and decreasing their effect on the components. Finally, signal integrity was evaluated for two data rates. It was found that the MF under investigation may be used in signal circuits up to 1 Gb/s.