A Tunable Bandstop Filtering Cable for Wide-Bandwidth Interference Suppression

This paper proposes a tunable band-stop filtering cable for wide-bandwidth interference suppression while the signal is in transit in it. A seminal cable modal that wrapping an insulated core wire in a defected conductor transmission structure (DCTS) is introduced. The band-stop filtering cable proposed consists of a polytetrafluoroethylene (PTFE) core wrapped in a defected conductor layer, a transmission dielectric PTFE layer, and the outermost shielding layer to strengthen shielding performance. The single-frequency band-stop filtering cable loaded with one rectangular spiral resonator can be equivalent to a parallel LC resonant circuit, and the resonant frequency can be modulated by tuning up the parameters of defected structure. We provide an elaborate analysis about the impact of variation in each parameter of defected structure on resonance frequency. The simulation results indicate that the resonant frequency is 3 GHz, the insertion loss is 25 dB and the return loss is 0.1dB. In addition, a wide-bandwidth filtering cable cascaded with twenty-one resonator units was fabricated and tested. Its radius is 2.413 mm and its length is 175 mm. The EM simulation results indicated a wide stopband from 3GHz to 5 GHz, and suppression of up to 60dB and a very narrow transition band. Compared with traditional communication cables, filtering cable can greatly improve the integration of microwave circuits by distributed suppressing unwanted harmonic components while providing transmission and shielding performance.