Additional Pulses in the Time Response of a Modal Filter with a Passive Conductor in the Reference Plane Cutout

The paper considers the technique for improving the protection against an ultrashort pulse with the help of a modal filter made by cutting a passive conductor in the reference plane of a microstrip line. The influence of the asymmetry of the cross section on the difference between the mode delays and the amplitudes of the decomposition pulses is studied. The decomposition of the first and second pulses, which merged at symmetry, is achieved. The appearance of additional pulses was revealed. It is shown that the delays of additional pulses are determined by a linear combination of the per-unit-length delays of the line multiplied by its length. The influence of boundary conditions at the ends of a passive conductor with an asymmetric structure is investigated. The appearance of additional pulses was detected, the amplitude of which is greater than the amplitude of the pulses of three main modes. The optimum value of separation between the conductors is obtained, which gives the attenuation by 10.4 times.