layered graphene transmission line as a tunable band stop filter and amplitude modulator at terahertz frequencies

In this paper, the effects of loading the substrate of a series of graphene transmission lines, in a terahertz frequency band, by longitudinal graphene strips, are investigated and numerically simulated. two applications of a tunable band-stop filter and amplitude modulator are designed. at first, a single graphene strip is inserted in the substrate of a series transmission. it is shown that by changing the chemical potential of the inserted graphene strip, in the range of 0-0.6 ev with step of 0.2 ev, a tunable band-stop filter which supports four cases of all-pass response and 10-db rejection bands of 1.77-2.55 thz (36.1%), 2.55-3.47 thz (30.5%) and 3.13-4.1 thz (26.8%) in the frequency range of 1-5 thz is obtained. then, to generalize the structure to obtain more flexibility and cover a wider range of applications, three parallel longitudinal strips are placed in the substrate, and the transmission response with varying chemical potential of all the graphene strips is calculated. it is observed that, with changing chemical potential of graphene elements in the range 0-1.4 ev, a tunable band-stop filter with lower bandwidths of 1.94-2.49thz (24.8%), 3.52-3.68thz (4.4%), 4.25-4.82thz (12.56%), which is applicable for high quality systems, as well as an amplitude modulator with more than 10 cases of modulation depths ranging from 0 to 100%, in the frequency range of 3.4-3.8 thz, and with optimum performance at the frequency of 3.6 thz, are obtained.