## 5 Applications of DRA
### Vehicular Applications  
DRAs are also used in vehicular or unmanned aerial vehicles (UAVs) applications [52; 66; 104; 105; 106]. The UAVs are frequently called drones, flying cars, aerial vehicles, and other names. The UAVs can fly autonomously or can be operated by human pilots [107]. The tremendous growth of UAVs is due to their high aerial mobility, advanced battery technology, rotors, global positioning system (GPS), cameras, sensors, low cost, fuel efficiency, and a broad range of applications [108; 109]. The UAVs provide new potential for business in civil and non-civil applications such as agriculture, parcel delivery, aerial mapping, wildlife conservation, and surveillance [110; 111]. As the applications for the vehicles are growing rapidly day by day, lightweight, compact size, high-gain, wide bandwidth and high-efficiency antennas are in high demand to enhance the capacity of wireless systems, reduce the overall system loss, and save the energy [112; 113]. Moreover, a fine-range resolution and accurate navigation are also necessary to ensure efficient and safe operation even in strong multipath environments and intended interference [114]. To solve the above issues, DRAs are used as they offer wide bandwidth, high gain, high efficiency, and low losses that make them excellent candidates for vehicular applications. In [104], a multiband DRA is designed for LTE automotive application. The proposed DRA is mounted and measured on the vehicle rooftop, as shown in Figure 27. Two DRAs are placed within a small area to reconfigure their radiation patterns on each frequency \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Ref.** & **Geometry** & \(f_{r}\) **(GHz)** & **BW (\%)** & \(\epsilon_{r}\) & **Gain (dBi)** & **Polarization** & **Applications** \\ \hline
[100] & Hemispherical DR & 2.4–2.5 & 4.08 & 22 & \(-15\) & DP & WCE \\
[101] & Rectangular DR & 2.4–2.5 & 4.08 & 80 & \(-23.6\) & LP & Implantable medical \\
[102] & Rectangular DR & 7.47–8.25 & 9.92 & 10 & 5 & CP & WBAN \\
[103] & Cylindrical DR & 2.46–2.59 & 5.15 & 12.85 & NM & CP & Breast cancer detection \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparison between various DRAs for biomedical applications. Figure 25: Wearable DRA: (**a**) proposed configuration; (**b**) antenna on a human body [102]. band in order to improve both the quality and reliability of the wireless link. As the vehicle's body is curved, the antenna should be flexible to withstand various bending conditions while still maintaining its normal performance under these deformations. In [105], a low-frequency DRA integrated with a high-frequency dielectric lens antenna (DLA) is proposed for dual-frequency vehicle communication. Both of the antennas share a single dielectric body, thus making the structure compact. The DLA is fed by a second embedded cylindrical DRA which is intended to reduce the conduction loss in the high band while maintaining a compact dimension. The DRA is excited by a vertical conducting adhesive strip on its sidewall. The dual-frequency antenna can provide wide impedance bandwidths and features a high degree of flexibility without the limitation of the frequency ratio. Good impedance matching is observed in the two bands when a larger ground plane is used. However, increasing the size of the ground plane will reduce the boresight antenna gain as the low-band antenna 3-dB beamwidth is widened in the H-plane and introduces many ripples in the E-plane. Both of the antennas in [104; 105] operated in LP. A radiation pattern of an antenna is one of the important parameters because it demonstrates the direction of the radiated energy distributed by the antenna into space. In the past few years, several conical beam antennas have been proposed for various applications owing to their omnidirectional radiation in the azimuth plane and directional radiation in the elevation plane. Specifically, in drone and vehicular communications applications, the transmitter or receiver needs to operate at a specific elevation [106].