## 3 Results and Discussion  
### Effect of Organic Solar Cell on the Proposed Antenna Performance  
In order to understand the impact of OSC integration on the antenna performance of the proposed design, modeling was performed using the CST microwave studio. Figure 4 shows a comparison between the simulated return loss of the proposed antenna with and without the presence of OSC. It can be seen from the figure that when OSC was included in the proposed CPW-fed monopole antenna, the reflection response (S11) was significantly enhanced. In the case of the OSC absence, the downlink resonance frequency was 14 GHz with minimum return loss of \(-22\) dB, while in the presence of OSC, the return loss was improved to \(-38\) dB and the resonance frequency was shifted by 3 GHz towards the preferable resonance frequency at 11 GHz. This is considered to be an interesting frequency for satellite applications, which is in compliance with that assigned by the International Telecommunication Union (ITU).  
Figure 4: Simulated S11 for the proposed CPW-fed monopole antenna with and without the presence of organic solar cell.  
Figure 3: Photograph of the fabricated CPW-fed monopole antenna; (**A**) front view; (**B**) connecting to VNA; and (**C**) experimental set up to measure return loss.  
Figure 5 shows the simulated and measured results of the antenna gain versus the frequency with and without the incorporation of OSC. One can notice that, at the resonance frequency of 11 GHz, the peak gain without OSC is about 3.76 dB, while that for the OSC incorporated antenna was increased to 5.90 dB. Considering the measured gain without the OSC, it was seen that the antenna gain at the resonance frequency of 11 GHz reached 6.0 dB. The simulation and measured results were found to be in good agreement. It is concluded that, by means of OSC incorporation, the realized gain can be greatly enhanced. In the case of OCS absence, the radiation pattern of the antenna relatively consisted of two symmetrical lobes on both the front and back of the antenna structure. The OSC can act as a reflector to reflect the propagated wave from the back to front of the antenna, which ultimately led to the increase in the antenna directivity (D) and radiation efficiency. Hence, the antenna gain linearly increased with the increase radiation efficiency as follows: \(G=\ \eta D\), where \(\eta\) is the radiation efficiency [30].  
The simulated and measured antenna radiation patterns for both E-and H-planes with and without OSC are shown in Figure 6. The antenna without OSC has an Omni-directional radiation pattern in both E and H planes. When the OSC was integrated, the antenna produced a directional radiation pattern in both planes (E-plane and H-plane) with more power confined in the main lobes and less power in the back lobes, which ultimately resulted in the increment of the antenna's directivity. This property makes use of the antenna in being more interested in directional telecommunication applications such as satellite application. All the radiation patterns were monitored at 11 GHz.  
Figure 5: Simulated and measured realized gain of the proposed CPW-fed monopole antenna with and without the presence of organic solar cell.  
Figure 6: _Cont._