# Wideband Millimeter-Wave Perforated Hemispherical Dielectric Resonator Antenna
## 3 Measurements and Discussions
### An HDRA Prototype with a Perforated Coat Layer  
Figure 19 showcases a prototype of the proposed 3D-printed HDRA with a perforated coat. The antenna was built by a 3D mattress company in its final configuration, utilizing a material with a dielectric constant of 10. The same feeding network as previously described was employed. As depicted in Figure 20, measured and simulated results exhibit agreement with respective impedance bandwidths of 59.5% and 58% over frequency ranges of 18.4 to 34 GHz and 18.4 to 33.5 GHz, respectively.  
Figure 16: The simulated and measured axial ratio of a layered HDRA.  
Figure 15: The simulated and measured return losses of two-layer HDRA.  
Figure 17: Simulated and measured gain of a layered HDRA.  
Figure 18: Simulated and measured of the radiation patterns of a layered HDRA at 28 GHz; (**a**) \(\phi=0^{\circ}\), (**b**) \(\phi=90^{\circ}\).  
In Figure 21, the measured and simulated AR are presented with respective wide bandwidths of 17.7% and 18%, covering frequency ranges of 24.74 to 29.66 GHz and 24.7 to 29.5 GHz, respectively. As demonstrated in Figure 22, a maximum gain has been achieved at 28 GHz with simulated and measured values of 9.53 dBic and 8.6 dBic, respectively, illustrating the enhanced gain due to the excitation of the higher-order resonance mode of TE\({}_{511}\). Figure 23 illustrates a good agreement between simulated and measured H-plane and E-plane radiation patterns at 28 GHz.  
Table 1 illustrates a comparative analysis of the performance of the proposed 3D-printed HDRA and those reported in earlier studies. The analysis highlights the distinctive features of the presented 3D-printed HDRA, notably its utilization of a single material of modified alumina sectors, effectively emulating the performance of configurations employing two dielectric layers, which is a departure from the multi-layer approach adopted in previous designs. Key attributes of the proposed HDRA include its capability to generate wide-band circularly polarized radiation, achieving significantly higher gain while maintaining a more streamlined architectural design.  
Figure 19: The prototype of the proposed hemispherical DRA with a perforated dielectric coat.  
Figure 20: The simulated and measured reflection coefficient of an HDRA with a perforated coat.  
Compared to the references [6; 9; 11; 12; 13; 15; 16; 19], the proposed configuration presents a wider impedance bandwidth of 58%. This is slightly narrower than the bandwidths reported in [10; 14], which utilized probe feeding and three dielectric layers, potentially posing challenges for mmWave applications. Moreover, the proposed antenna offers superior gain and axial ratio bandwidth performance compared to its reported counterparts. Additionally, it simplifies both the fabrication and assembly processes, potentially reducing production costs and enhancing overall efficiency. These attributes collectively position the proposed design as promising for various wireless communication systems and applications.  
Figure 21: The simulated and measured axial ratio of an HDRA with a perforated coat.  
Figure 22: Simulated and measured the gain of an HDRA with a perforated coat.