RESUMO
In this paper, we propose a new metallic cylindrical antenna at terahertz frequencies using the concept of low-frequency spoof surface plasmon polaritons (SPPs). The antenna is developed by introducing an open hollow ring (OHR) in each unit cell of the conventional periodic subwavelength corrugated metallic wire (PSCMW). The new structure is referred to as the PSCMW-OHR. The dispersion properties of PSCMWs and PSCMW-OHRs, the near-field and far-field distributions, as well as the radiation efficiencies are numerically evaluated and compared. By analyzing the numerical results, we find that there are extra new propagation modes that exist in the annular groove of the PSCMW-OHR, aside from the normal transmission modes in the PSCMW. Moreover, the dispersion line of the new SPP mode exhibits a negative slope. Surprisingly and interestingly, after passing through the light line, the propagation gets into the radiation zone, where it becomes a leaky mode with a complex-valued propagation constant. We have found that the far-field radiation of propagation in the leaky mode can lead to frequency scanning effects with a scanning angle of 22°, and the radiation efficiency can be increased to 90%, provided that the total number of the periodic unit cells is large enough.
