Experimental Study of the Reflection Symmetric Devices Based on Modal Distortion

This letter presents the study of a reflection symmetric modal filter (MF) and meander lines (MLs) based on a four-layer printed-circuit board. The design goal is to experimentally investigate reflection symmetric MLs and MF to analyze their characteristics and to comparatively evaluate their effectiveness in protecting electronic equipment from ultrawideband (UWB) interference. The intuition behind this letter lies in leveraging modal distortions to decompose UWB pulses into smaller, less harmful components. A meander routing scheme is employed to increase the differences in mode per-unit-length delays, thereby improving interference attenuation while maintaining a compact design. The novelty of this letter includes the first experimental analysis of time responses for one-turn and two-turn MLs, providing significant insights into their behavior and performance. Experimental results, corroborated by electrodynamic simulations, demonstrate that MLs achieve superior attenuation of UWB pulses compared to MFs of equivalent size. Specifically, meander routing enhances UWB interference suppression of the initial MF by at least 2 times in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N} _{1}$ </tex-math></inline-formula>, 1.63 times in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N} _{2}$ </tex-math></inline-formula>, and 1.36 times in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N} _{5}$ </tex-math></inline-formula> norms. In addition, a novel postprocessing technique is introduced to identify combinational pulses in the time response of the one-turn ML, advancing the understanding of pulse decomposition mechanisms. This method successfully demonstrated the presence of combinational pulses. This letter represents a notable advancement electromagnetic compatibility (EMC) by offering efficient and compact solutions for safeguarding electronic systems against UWB interference.