# Design and Analysis of Dual-Band High-Gain THz Antenna Array for THz Space Applications
## 4 Simulation
The 2D polar plots and 3D radiation patterns of Type A antenna, Type B antenna, and Type C antenna are shown in Figures 13 and 14, respectively. The simulation results show that the dual-band type A antenna directs the THz signals at 5.38\({}^{\circ}\) and 39.0\({}^{\circ}\) with the half power beam widths (HPBW) of 54.3\({}^{\circ}\) and 64.5\({}^{\circ}\), the side lobe of \(-\)2.2 and \(-\)1.8 dB, while operating at frequencies of 0.708 and 0.75225 THz with main lobe magnitudes of 5.51 and 6.25 dB and a radiation efficiency of 91.66 and 90.35%, respectively. Similarly, the Type B antenna array directs the THz signals at 56\({}^{\circ}\) and \(-\)8\({}^{\circ}\) with the half-power beam widths (HPBW) of 43.1\({}^{\circ}\) and 68\({}^{\circ}\), with side lobes of \(-\)4.5 and \(-\)2.7 dB while operating at frequencies of 0.689 and 0.758 THz with main lobe magnitudes of 9.95 and 7.75 dB and radiation efficiencies of 96.09 and 95.45%, respectively. Additionally, the Type C antenna array directs the THz signals at 58\({}^{\circ}\) and \(-\)25\({}^{\circ}\) with the half-power beam width (HPBW) of 49.8\({}^{\circ}\) and 27.8\({}^{\circ}\), with side lobes of \(-\)2.2 and \(-\)2.7 dB while operating at frequencies of 0.714 and 0.7412 THz with main lobe magnitudes of 12.5 and 11.23 dB and radiation efficiencies of 99.76 and 96.6%, respectively. From these values, it is concluded that as the number of transmitting elements increases in the array, the dual-band THz antenna array becomes more directive.The THz antenna is reasonably matched with feed lines, which is why the side lobes are negligible and the array antennas are more than 90 % efficient. Figure 11: The insertion losses of Type A, Type B, and Type C antennas. Figure 12: The dielectric loss per millimeter of Type A, Type B, and Type C antennas. Figure 13: A comparison of the Type A, Type B, and Type C antenna arrays on the bases of polar plots: (**a**) Type A at 0.708 THz, (**b**) Type A at 0.75225 THz, (**c**) Type B at 0.698 THz, (**d**) Type B at 0.758 THz, (**e**) Type C at 0.714 THz, and (**f**) Type C at 0.7412 THz. Figure 8.0 Far field radiation pattern: (**a**) Type A at 0.708 THz, (**b**) Type A at 0.75225 THz, (**c**) Type B at 0.698 THz, (**d**) Type B at 0.758 THz, (**e**) Type C at 0.714 THz, and (**f**) Type C at 0.7412 THz. The main purpose of designing of an antenna array from a single-element antenna is achieving a better results in antenna performance in terms of gain and directivity. Figure 15 suggests that as the numbers of radiating elements are increased in an antenna array, it results in a higher gain. From Figure 15, it can be seen that the gain of the Type C antenna for the 0.714 THz frequency band fluctuates in the range of 11.23-12.72 dB, while for the 0.741 THz frequency band, it varies from 9.65 dB to 11.64 dB. In addition, the efficiency of the Type C antenna for the 0.714 THz frequency band fluctuates in the range of 98.5-98.7% with a peak value of 99.7% at resonance frequency, while for the 0.741 THz frequency band, it varies from 98.9% to 95.57% with 96.6% at the resonance frequency; these efficiency ranges are greater than 95% for both bands, as shown in Figure 8.1  
As mentioned in the introduction section, the space communication demands a high directive antenna of at least 24 dBi. For the purpose of achieving the recommended gain and directivity, the CST microwave studio built-in array tool kit is used to calculate the array 3D pattern and the required gain and directivity from a single element with the help of an array factor (\(AF\)). For simplification purposes, the following labeling is adopted: Type D: dual-band 64 \(\times\) 1 THz antenna array; Type E: dual-band 128 \(\times\) 1 THz antenna array. The polar plot and 3D radiation pattern of the 64 \(\times\) 1 and 128 \(\times\) 1 element arrays are depicted in Figures 16 and 17, respectively, which show that the beam width becomes narrower and a peak gain of 23.8 and 24.1 dB, and 26.8 and 27.2 dB, can be achieved, respectively.