# Design and Analysis of Dual-Band High-Gain THz Antenna Array for THz Space Applications
## 2 Proposed Antenna Structure  
Before designing the dual-band high-gainTHz array antenna, the design of the proposed dual-band THz single antenna is required. Polyimide is utilized as a substrate material, having a loss tangent of 0.0027, a low dielectric loss, and a relative permittivity of 3.5 [6]. The dielectric losses \(D_{l}\) per millimeter in polyimide substrate at a resonance frequency \(f_{r}\) of 0.7 THz can be calculated by using the following equation:  
\[D_{l}=\frac{2\pi f_{r}CV^{2}\tan\delta}{1000} \tag{1}\]  
where \(D_{l},C,V,\tan\left(\delta\right)\) represent the dielectric losses per millimeter, the capacitance of the antenna, the voltage applied to the antenna, and the tangent loss of polyimide material. According to Equation (1), the dielectric losses of polyimide substrate at 0.7 THz are negligible, while PEC is used as a conducting material due to its low requirements of very fine meshes, and it is an ideal and efficient conductor for simulations in THz frequency range. The simulated results would be similar for all conducting because the resonance frequency of the antenna depend upon the dimensions of antenna, the material of the substrate, and the thickness of the substrate. The general volume of the single-element antenna is 536 \(\upmu\)m \(\times\) 526 \(\upmu\)m \(\times\) 10 \(\upmu\)m. From now on, the following labels will be utilized to distinguish among multiple variations in the designed antennas that are talked about in this paper:  
1. A circular THz antenna upheld by polyimide substrate material, as displayed in Figure 2a. 2. The cut has been introduced in the upper portion of the circular shape to obtain, for example, the half-moon-shaped THz antenna, as displayed in Figure 2b. 3. A elliptical shape conductor is introduced in the upper portion of the half-moon-shaped THz antenna, as displayed in Figure 2c. 4. A novel-shaped THz antenna, as displayed in Figure 2d; this shape is utilized as the main antenna to analyze the operation of the other antennas. The parametric values of the above-mentioned Step 4 antenna are shown in Table 2. The Step 1 antenna in Figure 2a is a simple circular antenna. The Step 2 antenna is a THz antenna with an elliptical shape cut out of size 263 \(\upmu\)m \(\times\) 131.5 \(\upmu\)m \(\times\) 1 \(\upmu\)m, as displayed in Figure 2b. The Step 3 antenna is shown in Figure 2c; this is approaches the proposed \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Particular** & **Frequency** & **Return Loss** & **Band Width** & **VSWR** & **Gain (dB)** & **Directivity** & **Efficiency (\%)** \\
**References** & **(THz)** & **(dB)** & **(GHz)** & **VSWR** & **Gain (dB)** & **(diB)** & **Efficiency (\%)** \\ \hline In This Work & 0.714/0.7412 & \(-\)23.57/\(-\)20 & 4.71/3.13 & 1.14/1.18 & 12.5/11.23 & 12.532/11.625 & 99.76/ 96.6 \\
[25] & 0.3 & *** & *** & *** & 25 & *** & *** \\
[26] & 0.3 & \(-\)35 & 2 & *** & *** & 11.71 & 70.8 \\
[27] & 0.6 & \(-\)18.5 & 200 & *** & 16.88 & 17.19 & 89.72 \\
[28] & 0.65 & \(-\)53.66 & 13 & 1.34 & 11.60 & *** & 86.75 \\
[29] & 0.1169 & \(-\)30 & 21.9 & *** & 19.6 & 21.6 & 67 \\
[30] & 0.8883 & \(-\)40.2 & 39 & 1.01 & 14.6 & 15.5 & 83.67 \\
[31] & 0.3 & \(-\)20 & 40 & *** & 13.6 & *** & 89 \\
[32] & 1.04 & \(-\)17.59 & *** & *** & 7.99 & 8.24 & 91.11 \\
[33] & 0.69 & \(-\)34.9 & 24 & 1.04 & 6.88 & 7.01 & *** \\
[34] & 0.703 & \(-\)50.94 & 26.4 & 1.00 & 5.24 & 6.81 & *** \\
[35] & 0.6308 & \(-\)44.71 & 36.23 & 1.01 & 7.94 & 8.61 & 85.7 \\
[36] & 0.312 & \(-\)50 & 22.6 & *** & 5.6 & *** & *** \\
[37] & 0.1/0.635/0.835 & \(-\)30/\(-\)40/\(-\)40 & 1.8/17.3/24.3 & ***/***/*** & 15.82/16.52/16.37 & ***/***/*** & 52/52/58.4 \\ \hline \end{tabular} Note: “***” is representing not mentioned, and ITU has reserved a few bands from 0.1–1 THz for spectroscopy, radio astronomy, and space research [3; 4; 5], according to that proposed antenna is helpful in space research.  
\end{table} 
Table 1: Comparison of dual-band THz antenna array with past reported work.