Two-Cascade Modal Filters Based on Modified Microstrip Lines with Grounded Conductors at the Ends

In this paper, two-cascade connections of three modal filters (MFs) were investigated based on modified microstrip lines (MSLs) with conductors grounded at the ends. It is an MSL with grounded conductors: one top, two symmetrical top, and two side conductors. The study included simulations in the TUSUR.EMC (TALGAT) software based on transmission line analysis and experimental validation using a P4M-18 MICRAN vector network analyzer. The results demonstrated that, due to a two-cascade connection, all three MFs can attenuate the ultrashort pulse (USP) impact by four times by decomposing it into four pulses with small amplitudes. By contrast, a one-cascade connection allows for the pulse attenuation by two times by decomposing the USP into two pulses. Meanwhile, the cross-section parameters and total length can be the same for both one-cascade and two-cascade MFs. Thus, modification by cascade connection can cost-effectively improve the protective properties of MFs against USPs. Index Terms— Modal filter, microstrip line (MSL), time response, ultrashort pulse (USP) © 2025 Istanbul University. All rights reserved.