Filtering Power Transmission Lines Using Defected Conductor Layer With Surface-Mounted Capacitors

This paper presents a pioneering design of a distributed multiband bandstop filtering power transmission line with the primary objective of suppressing interference. The proposed design integrates sawtooth dumbbell-shaped defected structures and surface-mounted capacitors on the outer conductor, providing an efficient emulation of a noncontact method for a filtering circuit model. To achieve flexibility in performance adjustments, the design is based on simulated current distribution paths and an equivalent circuit model comprising multiple inductors and capacitors, enabling parameter modifications. The fabrication process entails encasing a core wire within a dielectric layer of polyethylene foam (PE) and a polyimide defected conductor layer (DCL) featuring the sawtooth dumbbell-shaped structures and capacitors. Two filtering lines, each measuring 8 mm in diameter and 1500 mm in length, are simulated, fabricated, and measured. Experimental findings indicate that the first filtering line, equipped with a surface-mounted capacitor of 680 pF, achieves suppression exceeding 20 dB at 42.6 MHz and 48.2 MHz. In comparison, the second line, featuring a surface-mounted capacitor of 22 nF, demonstrates a suppression of −5.62 dB at 8.13 MHz. These results affirm the effectiveness of the proposed filtering line in achieving the desired bandstop filtering characteristics across various frequency bands.