# Bio-Inspired Dielectric Resonator Antenna for Wideband Sub-6 GHz Range
DRAs are successfully exploited for the design of dielectric metasurfaces, which are of paramount importance at very high frequencies, i.e., in the optical domain. Indeed, they can be used for polarization manipulation to design polarization converters [23], beam splitters [24], and polarization-based functional metalenses [25]. Another possibility is to use them for polarization detection [26] or polarization-based nano-printing [27]. As for their relevant inclination for high-frequency purposes, DRAs are currently recommended by the research community for 5G and mm-wave applications: indeed, as these structures are made of dielectric materials, they are free of conduction losses and, as such, capable of fulfilling bandwidth and radiation efficiency requirements. Additionally, as DRAs can be also made of polymers, they can be easily fabricated by means of Additive Manufacturing (AM) technologies. Very recently, optimized DRAs made of low permittivity materials providing wider bandwidth were proposed. An evaluation of dielectric materials suitable for microwave range applications was reported by [PERSON] and [PERSON] [28], who focused mainly on types of Rogers and FR4. Nonetheless, also polymers, such as polyactic Acid (PLA), were considered for the design and manufacturing of DRAs featuring simple 3D geometries [29; 30]. However, although very promising for wideband specification, low permittivity--DRAs are often characterized by low radiation efficiency. Therefore, the scientific community recently focused on the use of more intricate and complex 3D geometries, such as 3D quadrupole-shaped [31; 32], for WLAN (8 GHz) and 5G applications (3.5 GHz). An attempt of using bio-inspired geometry was presented by [PERSON] et al. [33]: in this work, snow-flake fractal and half split fractal rings were implemented on the classic cylindrical DRAs, thus achieving 90% of fractional bandwidth and gain enhancement in the frequency range between 4.7 and 12.4 GHz. Fractal segmented patterns were also employed by [PERSON] et al. [34] to design FR4-based DRAs with ultra-wideband performance (122.5% and 94.89%) from 4.8 GHz to 20 GHz and characterized by high compactness and gain at 8.5 GHz (8.75 and 15.65 dBi, respectively). Actual 3D star-super-shaped DRAs (S-DRAs) based on [PERSON] superformula were reported by [PERSON] et al. [35], [PERSON] et al. [36] and [PERSON] et al. [37]. In [35], the super-shaped DRAs (S-DRA) were designed to operate at 7.65 GHz and realized by considering polyvinyl chloride (PVC), a thermoplastic material having low permittivity (\(\varepsilon_{\mathrm{r}}\)-2.8) and negligible tangent loss. The results showed that in the single feed case study, a fractional bandwidth of 74% and gain of \(\sim\)8 dBi were accomplished between 6 and 13 GHz. Conversely, in [36; 37], twisted star-based S-DRAs were designed to operate in the sub-6 GHz range, at 3.5 GHz. The S-DRAs were realized by means of a photopolymer resin material having \(\varepsilon_{\mathrm{r}}\) = 2.7 and low tangent loss, suitable for stereolithography. The experimental results showed that this kind of DRAs was able to provide high gain (around 3 dBi) and radiation efficiency (\(\sim\)90%) at 3.5 GHz, while keeping their volume significantly small. However, although the use of bio-inspired geometry and DRAs proved to lead to an overall improvement of the antenna performance, especially in terms of bandwidth enhancement, works about the actual combination of these two strategies for a further boost in the antenna development are still at their beginning. Indeed, very few Authors attempted to design and realize bio-inspired DRAs and, in particular, none of them considers complex and thin 3D shapes, like Button snail Modulus modulus (spiral seashell) for the DRA applications. Therefore, in this research, the design and optimization of a bio-inspired super-shaped DRA, resembling a Spiral shell of a sea mollusk, generated by means of Gielis' superformula and suitable for sub-6 GHz applications, is presented.