Open-end discontinuity model of graphene nanoribbon transmission line in the terahertz band

Recently, attention has been focused on the design of GNR (Graphene Nanoribbon) based devices in the Terahertz band. Considering the effects of discontinuity in the structure of these devices is necessary as an inevitable factor in order to adjust the device response in the desired specifications. In this paper, open-end GNR transmission line, as one of the most important discontinuities in waveguide structures, is studied and modeled in detailed for the first time. This discontinuity effect is analysed using fullwave simulation in the form of an additional length added to the end of the line. Then it is expressed by simple mathematical expressions for a broad parameter range and its lumped element model is extracted. The obtained formula with a relative error of less than 10% is consistent with the results of fullwave simulation and it is also consistent with behavioral analysis of the structure.Finally, a bandstop filter is designed and simulated using quarter-wavelength open-end resonators. Then, discontinuity effect of the filter open-end lines is considered and completely confirmed. The frequency response of filter in the absence of discontinuity effect shows the cutoff frequency of 4.55 THz while by applying it, cutoff frequency is shifted to 5THz.