Crosstalk in a two-conductor modal filter on a double-sided PCB excited by an ultra-short pulse in a circuit ground with different boundary conditions

Background. Intentional electromagnetic excitations in the circuit ground are investigated. A patented modal filter characterized by two signal strongly coupled conductors and two circuit ground conductors is considered. The conductive excitation of an ultra-short pulse (USP) in the circuit ground of this modal filter is modeled. Aim. Assessment of the levels of crosstalk at the near and far ends of the modal filter when it is excited by a USP in the circuit ground. Methods. Quasi-static modeling of the time response in the frequency domain by a modified nodal method using the method of moments to calculate the matrices of per-unit-length parameters of a multi-wire transmission line. Results. The voltage waveforms in the active and passive conductors of the modal filter with different boundary conditions at the ends of the active conductor demonstrate that without taking into account losses the crosstalk level reaches 34 % at the near end of the modal filter and minus 55 % at the far end, relative to half of the amplitude of the electromotive force of the USP excitation with duration of 3 ns. Conclusion. The results indicate that the USP excitation in one circuit ground conductor relative to another, produced by a generator with a low internal resistance, can double the levels of crosstalk in the modal filter signal conductors. These levels can reach quarter of the excitation electromotive force amplitude. Therefore, it is recommended to assess the threat of such interference to similar structures.