Development of modal filter prototype for spacecraft busbar protection against ultrashort pulses

The protection of the onboard equipment of the spacecraft from an ultrashort pulse (USP) based on modal filtering is proposed. The paper presents the results of the development of a modal filter (MF) prototype with a broad-side coupling. When choosing a structure, the maximum bus current, insulation breakdown voltage, wave impedance of line and the duration of the interfering USP are taken into account. To substantiate the choice of structure, quasi-static and electrodynamic simulations are performed. The simulation showed that the MF with resistance of 50 Ω at both ends of the passive conductor effectively weakens the 0.45-ns USP by 4 and with non-resistance connection on the passive conductor by 7. The MF prototype without resistors is made. Frequency dependence of |S21| is measured. An experiment showed that the MF weakens the USP by 5.61. The bandwidth of the MF is 60 MHz.