# CubeSat-Based Observations of Lunar Ice Water Using a 183 GHz Horn Antenna: Design and Optimization
## 3 Simulation and Results  
After computing the parametric data for \(a_{j}\) and \(d_{j}\), we proceed to measure \((x,y)\) data, which allows us to plot the corrugated horn antenna on MATLAB. Subsequently, we export the 2D data from MATLAB to CST for antenna simulation. To accomplish this, we utilize the following code lines in MATLAB:  
\[For\ j=1:N-1,\]  
\[y_{n} =a_{j};\ x_{n} =(1-\delta)\text{P}+x_{n-1};\ y_{n+1} =a_{j}+d_{j};\ x_{n+1} =x_{n};\ y_{n+2} =a_{j}+d_{j};\ x_{n+2} =\delta\text{P}+x_{n};\]  
\[y_{n+3} =a_{j+1};\ x_{n+3} =x_{n+2};\]  
\[n=n+4;\]  
Figure 2: Corrugated horn antenna 2D geometry. By executing these code lines, we generate the necessary data for antenna simulation in CST, enabling us to analyze and optimize the antenna's performance, see Figure 3:  
We successfully exported the 2D data from MATLAB to CST software, enabling us to construct the 3D model of the corrugated horn antenna (refer to Figure 4a). The antenna's dimensions are observed to be 9.3 mm in length and 6.28 mm in aperture, making it compact and suitable for small satellites. These specifications make the antenna a viable candidate for various missions, taking advantage of its miniature size. Once the corrugated horn antenna is illustrated, we utilize smooth spline curve fitting tools with a smooth factor of 0.4 to transform the corrugated antenna into a smooth-walled horn antenna. Fabricating corrugated horn antennas at THz frequencies can indeed be a challenging and, at times, an unfeasible task. However, our proposed solution of transforming the antenna geometry into a smooth-walled design allows us to utilize straightforward 3D printing technology for its production. This transformation not only simplifies the manufacturing process but also makes it cost effective and time saving. By adopting the smooth-walled design, we overcome the complexities associated with traditional corrugated antennas, making it a viable option for various applications  
Figure 4: 3D model of (**a**) the corrugated horn antenna and transform to (**b**) smooth-walled antenna. Figure 3: Corrugated horn antenna on MATLAB plot. in the THz range. The utilization of 3D printing technology further enhances accessibility and affordability, making the smooth-walled antenna an attractive choice for research and experimental purposes. Our approach opens new possibilities for the development of advanced antennas in the THz domain, paving the way for more efficient and cost-effective solutions in the field of space exploration and beyond. The CAD model of the smooth-walled horn antenna on CST can be seen in Figure 4b. In Figure 4, we present the transformation of the corrugated antenna into a smooth-walled design while maintaining identical dimensions. Through this optimization process, we have successfully achieved a seamless transition from the original corrugated configuration to the smooth-walled counterpart, all while preserving the critical antenna parameters. This transformation not only simplifies the fabrication process but also enhances the antenna's performance, making it a promising candidate for various applications, especially in the THz frequency range. The following figures display the comparison results of the corrugated and smooth-walled antenna simulations in CST software. Through this simulation, we gain the antenna's performance characteristics, including \(S_{11}\), VSWR, gain, directivity, and radiation patterns. Figure 5 showcases the \(S_{11}\) simulations of both the 183 GHz corrugated horn antenna and the smooth-walled horn antenna. At the designated frequency of 183 GHz, the \(S_{11}\) parameter for the corrugated horn antenna remains below \(-15\) dB, which confirms its usability at the specified frequency. However, the \(S_{11}\) parameter of the smooth-walled antenna, also at the same frequency and size, stays under \(-25\) dB, indicating superior impedance match capability and lower insertion losses. This comparison reveals the improvements achieved through the transformation to a smooth-walled design.