## 1 Introduction
Specifically, a custom lab-made material has been used for the prototype, while in [2; 3; 4; 5] commercial materials have been used; An unconventional design to enhance antenna performance, not easily realizable with traditional manufacturing techniques, has been adopted; moreover, the choice of using a DRA for the scope, allowed for the development of the main body of the antenna with a dielectric material, thus avoiding problems related with metallization faced in [5; 9; 10]. In Table 1, a simplified comparison between the proposed design and the state-of-the-art ones is represented. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Use of**} & \multicolumn{2}{c}{**Use of AM to**} & \\ \multirow{2}{*}{**Design**} & **Type of AM** & **Customizable** & **Realize** & **Need for** \\  & **Technology and** & **High-Dielectric-** & **Unconventional** & **Complex** \\  & **Costs (\$)** & **Constant** & **Shape Otherwise** & **Metallization** \\  & & **Material** & **Unrealizable** & **Procedures** \\ \hline Proposed in this & & & & \\ paper & & Yes & Yes & No \\ Proposed in [2] & & & No & Yes \\ Proposed in [3] & & & No & Yes \\ Proposed in [4] & & & No & Yes \\ Proposed in [5] & & & No & Yes \\ Proposed in [6] & & & No & Yes \\ Proposed in [6] & & & Yes & Yes \\ Proposed in [7] & & & No & Yes \\ Proposed in [8] & & & No & Yes \\ Proposed in [9] & & & No/Yes & Yes & Yes \\ Proposed in [10] & & & No & No \\ Proposed in [10] & & & No & Yes & No \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison among the proposed design and the state-of-the-art ones. Dielectric Resonator Antennas Working Principle and Possible Improvements Due to Additive Manufacturing  
DRAs are essentially dielectric resonators without metallic enclosures, placed in an open environment in which they can radiate energy when excited by a source. They offer interesting properties, which include:  
* Good gain. * The possibility to realize small-sized antennas because the DRA dimensions are proportional to \(\lambda_{0}/\sqrt{\varepsilon_{r}}\). * Excellent efficiency, especially at high frequencies, when compared with metal fabricated antennas, due to the lack of inherent conduction loss inside the dielectric resonators. * A simple coupling schema that allows users to match DRAs with barely any type of planar transmission line by varying the position of the radiator onto the line. * The possibility to realize both narrowband as well as wideband and ultrawideband antennas by varying some design parameters. * The possibility to obtain different radiation characteristics by exciting different modes of a DRA. These advantages are, however, counterbalanced by two main drawbacks, which are cost and complexity. As for the former, it is typically due to the types of materials and manufacturing processes that are needed to realize a DRA. Indeed, purely ceramic materials, which are traditionally used for the scope, are very difficult to be shaped in complex geometries. Besides, postprocessing, like cutting or drilling holes on them, is very expensive and difficult to realize. As for the latter, the computational complexity grows with the degrees of freedom that can be modified in the final designed structure (e.g., the ratio between the various dimensions of the resonator, the value of \(\varepsilon_{r}\), as well as the type and size of feed). For both these reasons, the most commonly used geometries in designing DRAs are the three most-known--hemispherical, cylindrical, and rectangular--for which a theoretical analysis has been proposed in [18], by [PERSON] and [PERSON], who gathered the theory of the propagating modes for each of those geometries, giving the equations to predict their resonant frequencies. Over the years, even more complex types of DRAs have been investigated, as reported in the review by [PERSON] and [PERSON] [19]. More specifically, low-profile (LP) DRAs have been intensively studied, as well as various methods to tune their working frequency.