Gain enhancement of dual-band terahertz antenna using reflection-based frequency selective surfaces

In this article, a technique for gain enhancement of metallic radiator based dual-band THz antenna has been implemented. The antenna operates in fundamental and second order modes, thus providing conical and biconical radiation. The different reflective frequency selective surfaces (FSS) have been designed and integrated with antenna for its gain enhancement. The study of FSSs has also been carried out using the circuit theory approach and electrical equivalent circuits have been designed to verify their operation. The FSS-1 designed to operate at the frequency of fundamental mode enhances the gain by 1.15 and 0.62 dBi in lower and upper band respectively. The FSS-2 designed for operation at frequency of second order mode enhances gain by 2.01 and 1.45 dBi in lower and upper band, respectively. Here, the radiation behaviour of antenna is not preserved at the frequency of the fundamental mode. A broadband FSS is realized by the stacking of FSS-1 and FSS-2. The integration of stacked FSS with the antenna enhances its gain by 2.39 and 1.19 dBi in the lower and upper band, respectively. The radiation behaviour of antenna is preserved in case of stacking but this may offer structural complexity by increasing the profile dimensions. It can be inferred that the usage of a broadband FSS is optimum and hence a broadband FSS-3 is implemented and integrated with the antenna for improving the gain by 1.89 and 2.37 dBi in the lower and upper band, respectively in this article. A comparative study proves that the proposed technique is superior over others available in the literature.