# Design and Analysis of Dual-Band High-Gain THz Antenna Array for THz Space Applications
## 4 Simulation
These parameters are represented by \(R_{1},L_{2},L_{4}\), and \(C_{2}\), respectively, as shown in Figure 6. While the equivalent circuit model of feed line is made of two inductors (\(L\)) and two capacitors (\(C\)), each of them are connected in series and parallel with each other; these parameters are represented by \(L_{1},L_{3},C_{1}\), and \(C_{3}\), respectively, as shown in Figure 6.  
The resonance frequencies \(f_{\rm c1}\) and \(f_{\rm c2}\) of the proposed RLC circuit is calculated by using a resonance circuit formula [42]. \[f_{\rm c1}=\frac{1}{2\pi\sqrt{L_{1}C_{1}}}=\frac{1}{2\pi\sqrt{L_{2}C_{2}}} \tag{11}\]  
\[f_{\rm c2}=\frac{1}{2\pi\sqrt{L_{3}C_{3}}}=\frac{1}{2\pi\sqrt{L_{6}C_{6}}}= \frac{1}{2\pi\sqrt{L_{4}C_{4}}} \tag{12}\]  
Figure 5: Evaluation of Type A/Step 4 antenna with the help of return loss vs. frequency graph. Figure 6: Equivalent circuit model of dual-band THz antenna. The calculated and equivalent circuit model (ECM) first and second resonance frequencies \(f_{c1}\) and \(f_{c2}\) are listed in Tables 4 and 5, respectively. Similarly, the bandwidths \(BW_{1}\) and \(BW_{2}\) of the proposed equivalent circuit model (ECM) are calculated by using the following equations:  
\[BW_{1}=\frac{f_{c1}}{Q_{1}}=\frac{\frac{1}{2\pi\sqrt{L_{1}C_{1}}}}{\frac{1}{R} \sqrt{\frac{L_{1}}{C_{1}}}}=\frac{R_{1}}{2\pi L_{1}} \tag{13}\]  
\[BW_{1}=\frac{f_{c1}}{Q_{1}}=\frac{\frac{1}{2\pi\sqrt{L_{2}C_{2}}}}{\frac{1}{R} \sqrt{\frac{L_{2}}{C_{2}}}}=\frac{R_{1}}{2\pi L_{2}} \tag{14}\]  
\[BW_{2}=\frac{f_{c2}}{Q_{2}}=\frac{\frac{1}{2\pi\sqrt{L_{3}C_{3}}}}{\frac{1}{R} \sqrt{\frac{L_{3}}{C_{3}}}}=\frac{R_{1}}{2\pi L_{3}} \tag{15}\]  
Figure 6.0  
The calculated and equivalent circuit model (ECM) bandwidths \(BW_{1}\) and \(BW_{2}\) of the first and second resonance frequency bands are listed in Tables 4 and 5. The reflection coefficient of the proposed dual-band novel shape THz antenna is tuned according to the resonance frequencies by changing the magnitudes of the capacitors and inductors. The mutual correlation between the reflection coefficients of the proposed dual-band Step 4 THz antenna and the equivalent RLC circuit model is compared in Figure 7, which presents strong agreement between the two reflection coefficients. The calculated and equivalent circuit model results shown in Tables 4 and 5 suggest that the first resonance frequency is associated with the values of \(L_{1},L_{2},C_{1},\) and \(C_{2}\), while the second resonance frequency is tuned with the values of \(L_{3},L_{4},C_{3},\) and \(C_{4}\), respectively. The first resonance frequencies, i.e., the calculated \(f_{c1}\) calculated version and equivalent circuit model \(f_{c1}\) ECM version, are 0.708314 and 0.7085 THz, respectively. Similarly, the second resonance frequencies, i.e., the \(f_{c2}\) calculated version and equivalent circuit model \(f_{c2}\) ECM version, are 0.753 and 0.7525 THz, respectively. The calculated and equivalent circuit model results show that the first bandwidth \(BW_{1}\) is associated with the values of \(R_{1},L_{1},\) and \(L_{2}\), while the second bandwidth is tuned with the values of \(R_{1},L_{3},\) and \(L_{4}\), respectively. The calculated \(BW_{1}\) and equivalent circuit model \(BW_{1}\) bandwidths are 10 and 10 GHz for the first resonance frequency at 0.708314 and 0.7085 THz, respectively. Similarly, the calculated \(BW_{2}\) and equivalent circuit model \(BW_{2}\) bandwidths are 10 and 10 GHz for the second resonance frequency at 0.753 and 0.7525 THz, respectively. Table 2 shows the parameters of Type C antenna array. It is clear from Figure 8 that the Type A antenna array operates at 0.7085 and 0.75225 THz, with \(-\)10 dB band widths of 9.12 and 6.4 GHz, respectively. The resonant frequencies \(f_{c1}\) and \(f_{c2}\) of the Type B