Using Reflection Symmetry to Improve the Protection of Radio-Electronic Equipment from Ultrashort Pulses

The paper considers the protection of critical radio-electronic equipment (REE) from ultrashort pulses (USP) by means of modal filters (MFs). A new approach to improve modal filtration by using reflection symmetry is analyzed. The results of a sophisticated research into protective devices based on reflection symmetric MFs are presented: improving the characteristics of four MFs through optimization both by one and simultaneously by several criteria; calculating the per-unit-length time delays matrix of a reflection symmetric MF using the obtained analytical expressions; calculating the time and frequency responses of an MF with and without losses in conductors and dielectric; developing the laboratory evaluation board; analyzing the effect of moisture protection on the characteristics; analyzing the features of reflection symmetry structures; comparing microstrip and reflection symmetric four-conductor MFs. The obtained results allow us to argue that the reflection symmetric MF protects REE from a USP due to its decomposition into a sequence of pulses with pairwise equalized voltage amplitudes and close time intervals between decomposition pulses with an attenuation coefficient of four times with a controlled bandwidth of a useful signal. This research helps take advantage of the possibilities of using the symmetry to improve modal filtering and opens the ways to create a large number of new MF designs, applying only the principles of the symmetry described in the work.