Tuning the higher to lower order resonance frequency ratio and implementing the tunable THz MIMO/self-diplexing antenna

Abstract

The frequency ratio of higher to lower order mode can be electronically tuned in a terahertz (THz) antenna with metallic radiator using a graphene loop. Antenna is designed with slotted metallic radiator to obtain the dual-band response with fundamental and second order transverse magnetic mode providing the directional and bi-directional radiation pattern in the lower and upper band, respectively. The insertion of graphene loop and varying its chemical potential (${\mu }_c$) provides two resonances until $0.4\mathrm{eV}$ and four resonances for further greater values of ${\mu }_c$. The desired impedance matching can be achieved at the frequencies of any two resonances at a time by selecting an appropriate value of ${\mu }_c$. Antenna can operate with higher/lower order mode centred at frequency 3.77/3.02 THz and 4.39/2.86 THz for the values of ${\mu }_c$ as 0.9 and $0.3\mathrm{eV}$ , respectively. The frequency ratio of higher to lower order mode can be tuned within the range of 1.22–1.59 with the variation in ${\mu }_c$. Also, application of graphene loop confines the radiated power in a single direction at the frequency of higher order mode making the radiation pattern consistent. Antenna can be utilized in future THz wireless applications which require the utilization of adjacent channels with different frequencies in communication. Also, a two-port antenna is designed which can offer the tunable multi-input–multi-output (MIMO) and self-diplexing capability with pattern diversity. The MIMO parameters; envelope correlation coefficient (ECC) and diversity gain (DG) is evaluated and their values are found within acceptable limits as ECC$<0.06$ and DG$>9.9$ in the operating bands.