# Metamaterial Based Ku-Band Antenna for Low Earth Orbit Nanosatellite Payload System
## 3 Results and Discussions  
The simulated antenna has been fabricated and measured to validate performances. The antenna's reflection coefficient is presented in Figure 3. The antenna achieves \(-10\) dB impedance bandwidth of 1.87 GHz (11.18 GHz to 13.05 GHz) in simulation and 2.275 GHz (10.85 to 13.125 GHz) in measurement. Both results seem identical. However, a little mismatch is observed due to fabrication and measurement tolerances.  
Figure 2: Metamaterial characteristics (**a**) permeability; (**b**) permittivity. (**c**) reflection phase, and (**d**) AMC wave interference.  
The simulated 3D radiation pattern of the projected antenna at 12.1 GHz is demonstrated in Figure 4a. The antenna shows 6.53 dBi of realized gain with very low back radiation. The substantial decrease in back radiation occurred due to the AMC metamaterial layer. Additionally, the 3 dB simulated axial ratio is also presented in Figure 4b. The antenna shows approximately 165\({}^{\circ}\) of 3 dB axial beamwidth with stable circular polarization.  
Figure 4: (**a**) 3D radiation pattern and (**b**) axial ratio at 12.1 GHz.  
Figure 3: Reflection coefficient results.  
The radiation characteristics have been measured in Satimo nearfield measurement system, shown in Figure 5. The antenna exhibits realized gain of 6.61 dB and 6.7 dB without nanosatellite (free space) and with nanosatellite structure, respectively. Besides, axial beamwidth at 12.1 GHz has also been measured, shown in Figure 6. The antenna attained 3 dB axial beamwidth of 162\({}^{\circ}\) and 158\({}^{\circ}\) for phi 0\({}^{\circ}\) and phi 90\({}^{\circ}\), correspondingly.  
The developed antenna has been integrated into the standard 1 U nanosatellite architecture to investigate the performance in the real environment. In both simulation and measurement, the antenna reveals well agreement in both measurements. The radiation pattern with 1 U nanosatellite structure at 12.1 GHz is depicted in Figure 7. In Figure 7a, only antenna (without metamaterial layer) has been integrated, and radiation performances have been observed where the antenna reveals realized gain of 4.7 dB. On the other hand, the antenna with a metamaterial layer has been integrated to observe radiation performances, where the antenna reveals realized gain of 6.69 dB. Therefore, the metamaterial significantly improves antenna gain and reduces the coupling effect with satellite structure.  
Figure 5: The radiation pattern of the antenna (**a**) measurement system and (**b**) measured radiation pattern.  
This article presents a compact Ku-band CP antenna for the nanosatellite communication system. The antenna's gain significantly increases by placing an AMC in the back side of the antenna, which also reduces the antenna's signal interference with other nanosatellite components. The antenna's performance has been investigated with a 1 U nanosatellite structure and found suitable to integrate with metallic and nonmetallic surfaces of any miniature nanosatellite structure. A details comparison table of the projected antenna with the existing antenna has been presented in Table 2. Where most of the shows liner polarization except [12], but the antenna size is larger than the projected antenna. Additionally, antenna performance does not investigate with satellite structure. The antenna presented in [28] and [11] shows higher gain, but the antenna size is very large compared to the nanosatellite structure; polarization is the liner. Finally, the compact size, high gain, circular polarization, and investigation with 1 U nanosatellite structure makes proposed antenna a potential candidate for Ku-band 1 U nanosatellite communication systems.  
Figure 6: Axial beamwidth of the proposed antenna.  
Figure 7: Antenna radiation pattern with 1 U nanosatellite structure at 12.1 GHz (**a**) without AMC metamaterial and (**b**) with metamaterial.