## 4 Conclusions  
As LEO satellites are a promising solution that can offer higher data rates at very low latencies, they can be used to complement TN and assure seamless connectivity. In order to design an antenna for this application in a passenger car, a link budget analysis was performed. To obtain downlink data rates of 25 Mbps from the link budget, it was concluded that the antenna requires a realized gain of 27 dBi. This means that if each antenna element had a gain of 6 dBi, an array of 12 \(\times\) 12 elements would be needed to achieve 27 dBi. This implies a footprint of 6\(\lambda\)\(\times\) 6\(\lambda\) with respect to a frequency of 10 GHz or 18 \(\times\) 18 cm. Since size is a major constraint for integrating an antenna into the roof of a car, the aim was to design an antenna element that could provide a gain higher than the conventional design. Therefore, a design based on superstrate loading was used to enhance the gain. The antenna was manufactured, assembled, and tested in a shielded anechoic chamber. In the DL-band, measurements showed that there was a 500 MHz shift to a lower frequency in the S11 matching from the simulations. This was due to the difference in the measurement environment and variations in the substrate's properties. The presented antenna design and results show that the inclusion of a superstrate in the single element enhances its realized gain by 3 \(\ldots\) 6 dB. Therefore, this approach looks promising for the miniaturization of a Ku-band antenna array as we could potentially use half of the number of elements using superstrate loading. This could drastically reduce the array size, making it suitable for automotive applications. The reduced number of elements leads to fewer front ends or beamforming integrated circuits which, in turn, reduces cost and manufacturing complexity. Contrary to the size reduction and high gain, the superstrate poses the challenges of scanning range, side-lobe levels, and bandwidth in particular. For applications in which a full-hemisphere beam steering is required, this approach may not be feasible. Similarly, for large fractional bandwidth requirements, the superstrate-based antenna design presents challenges in implementation. These characteristics require further study to define the boundary conditions and constraints for the use of a superstrate in high-gain-antenna array designs.  
The following topics are considered for further investigation:  
* The behavior of a superstrate integrated into a 2 \(\times\) 2 phased array, especially with respect to an analysis of its impact on beam steering. In the measurements, a null was observed in the UL-band for an elevation cut of \(\Phi=0^{\circ}\). It needs to be determined whether this is caused by the superstrate itself or from measurement artifacts. In order to steer the beam to \(\pm\) 50\({}^{\circ}\) for satellite tracking, such a null would be detrimental to receiving or transmitting the signal as it can cause interferences.
* The dimension of the superstrate is critical for achieving the maximum gain and for achieving a consistent radiation pattern over the frequency range of interest. Properties such as the dielectric constant, thickness, size, and height of superstrate also play a role in gain enhancement. Therefore, they need to be carefully chosen to attain the best advantage in automotive applications. In the antenna, an increased height and multiple layers lead to additional costs which also need to be studied to reach a compromise between performance, size, and cost.  
Conceptualization, R.F. and S.I.B.; formal analysis, R.F.; resources, P.G. and R.E.; writing - original draft, R.F.; writing -review & editing, S.I.B., J.S. and M.H; Supervision, M.A.H. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.