Filter cable design with defected conductor transmission structures

Abstract

This article introduces a filter cable design featuring an insulated cylinder that has been coated using a defected conductor transmission structure (DCTS). This unique feature enables the cable to possess distributed filter advantages throughout its length. The DCTS, featuring a well-designed etched pattern, serves as a boundary condition for transmitting specific frequency electromagnetic waves and effectively performs the same filtering function as a lumped filter circuit. To validate this concept, a lowpass filter cable is proposed, which incorporates six-slot-ring defected structures. The cable utilizes polytetrafluoroethylene (PTFE) as the inner dielectric, encased within a flexible printed circuit board (FPCB)-manufactured DCTS. With precise dimensions of a 2.4 mm diameter and a 340 mm length, the proposed filter cable demonstrates performance, indicated by a minimal insertion loss of under 0.38 dB below 6 GHz in the passband, and a rejection surpassing 43 dB at 7.7-25 GHz in the stopband. By comparison, traditional coaxial cables lack these filtering capabilities, making the filter cable with DCTS a viable choice for addressing electromagnetic compatibility (EMC) concerns.