# 3D-printed super-Wideband Spidron Fractal Cube Antenna with Laminated Copper
## 3 Experimental Results and Discussion  
Based on design parameters in the pervious section, a prototype of the proposed antenna and balun were fabricated. The 3D frame of the proposed antenna was fabricated using a 3D printer (Cubicon Single Plus, Hyvision system) with acrylonitrile butadiene styrene. The thickness of the 3D frame was set to 2.5 mm in consideration of both the time required for printing as well as durability. The Spidron fractal patches--consisting of copper tape--were directly pasted onto the 3D frame and connected by soldering. To support the 3D frame, styrofoam was attached to the inner side of the Spidron fractal face. The interior of the Spidron fractal cube was empty except for the portion where the Styrofoam was located. Photographs of the fabricated balun and antenna are presented in Figures 5 and 6, respectively. Figure 4: Geometry of the proposed balun: (**a**) Top side; (**b**) Bottom side. Figure 3: Input impedance of the proposed antenna as simulated by a lumped port. An Agilent 8510C network analyzer was used to measure the reflection coefficients of the fabricated balun and antenna. Figure 7 depicts the simulated and measured reflection coefficients of the proposed balun. The reflection coefficient was measured by loading a 145-\(\Omega\) chip resistor at one side of the edge and an SMA connector at the opposite edge. As a result, it could be confirmed that the balun has wideband characteristics. The simulated and measured results of the reflection coefficients of the proposed antenna are illustrated in Figure 8. It was found that the simulated and measured \(-10\) dB reflection ratio bandwidths are 36.7:1 (0.46-16.61 GHz) and 34.9:1 (0.44-15.38 GHz), respectively. These results show that the \(-10\) dB reflection ratio bandwidth meets the SWB requirements. Figure 5: Photographs of the proposed balun: (**a**) Top side; (**b**) Bottom side. Figure 6: Photograph of the proposed antenna. Figure 7: Simulated and measured reflection coefficients of the proposed balun. To measure the radiation patterns and peak gain of the proposed antenna, a dual-polarized rectangular horn antenna in an RF anechoic chamber was utilized. The measured peak gain is illustrated in Figure 9. Note that the peak gain shown in the figure was extracted from the measured three-dimensional radiation pattern. At the operating frequency, the peak gain varies from 3.42 to 9.29 dBi. Figure 10 plots the measured radiation patterns of two cutting planes (\(xz\)- and \(yz\)-planes) at 0.5 GHz, 8 GHz and 15 GHz. The antenna has nearly omnidirectional radiation patterns at every operating frequency. All radiation patterns in Figure 10 were obtained from the power sum of the \(E_{\theta}\) and \(E_{\phi}\) patterns. As shown in Figures 9 and 10, the peak gain and radiation pattern of the proposed antenna exhibit spiky responses with an increase in the frequency. This is due to the effects of higher order currents when the frequency is increased. Figure 11 shows the simulated radiation efficiency of the proposed antenna. The radiation efficiency varies from 77% to 98%. As the frequency increases, the loss tangent of the 3D printer filament material increases, so the antenna efficiency decreases with increasing frequency. Figure 8: Simulated and measured reflection coefficients of the proposed antenna. Figure 10: Measured peak gain of the proposed antenna. To verify the performance, the proposed antenna was compared with previously proposed antennas [5; 6; 7; 9; 10; 12]. Their bandwidths and sizes are illustrated in Table 1. It is evident that the proposed antenna exhibits a wider operating bandwidth ratio and a smaller size compared to those of previous antennas [5; 6; 12]. The other antennas [7; 9; 10] are smaller than the proposed antenna as well. However, the \(-10\) dB reflection ratio bandwidths in the aforementioned studies [7; 9; 10] are narrower than the proposed antenna. Figure 3:0 Simulated radiation efficiency of the proposed antenna.