## 3 Experimental Verification  
### Experimental Results of the Designed Antenna with the Standalone AMC  
Based on the design parameters, the proposed antenna with the AMC was fabricated for an experimental demonstration. Figure 5a,b present top-view and side-view images of the fabricated Spidron fractal dipole antenna with the AMC. To realize a size of \(500\times 400\times 10\) mm\({}^{3}\), four layers of \(500\times 400\times 2.5\) mm\({}^{3}\) ferrite in total were stacked and adhered using double-sided tape. The distance between the Spidron fractal dipole antenna and the AMC also included a layer of Styrofoam with a thickness of 1.5 mm.  
The simulated VSWR (voltage standing wave radios) and measured VSWR are shown in Figure 6. It can be confirmed that the VSWR characteristics \(<3.5\) are matched at the target frequency of 20-500 MHz, and that the simulation and measured results are similar. The difference between the simulation and measurement is due to errors which arose during the manufacturing and measurement processes. Considering the performance of the commercial antenna which is utilized in manpack application [24], the VSWR characteristics of the proposed antenna are acceptable for use in the manpack application.  
Figure 5: Photographs of the fabricated Spidron fractal dipole antenna with the AMC: (**a**) top-view; (**b**) side-view.  
Figure 6: Measured and simulated VSWRs of the Spidron fractal dipole antenna with the AMC.  
Figure 7 depicts the simulated radiation patterns on the \(yz\)-plane of the Spidron fractal dipole antenna with the AMC at 20 MHz, 260 MHz and 500 MHz. This figure shows that the AMC operates as a reflector and that the radiation pattern of the antenna is therefore directed onto the \(+z\)-axis. In addition, the AMC can be located at a distance of 0.0001 \(\lambda_{L}\) (\(\lambda_{L}\) is the wavelength at the lowest operating frequency), which is an extremely small value compared to the value of \(\lambda/4\) (\(\lambda\) is the wavelength at 20 MHz), which is the required distance between this type of antenna and a general PEC reflector. Consequently, low-profile characteristics are realized without sacrificing the performance of the antenna within a wide frequency band.  
Figure 8 illustrates the realized gain on the \(+z\)-axis of the Spidron fractal dipole antenna with the AMC. The gain of the proposed antenna with the AMC varies from \(-33\) dBi to \(-1.1\) dBi within the operating frequency. In the high-frequency band, the proposed antenna with the AMC has a flat gain characteristic due to the characteristics of the ferrite. The gain characteristic of the commercial antenna in [24] is approximately \(-36\) dBi at 20 MHz. Therefore, it can be confirmed that the gain characteristics of the proposed antenna are reasonable.  
Figure 7: Simulated radiation patterns of the Spidron fractal dipole antenna with the AMC on the \(yz\)-plane: (**a**) 20 MHz; (**b**) 260 MHz; (**c**) 500 MHz.  
To verify the performance, the proposed antenna is compared with previously designed antenna [2; 3; 7]. The operating bandwidths and sizes of the antennas are illustrated in Table 1. It is evident that the proposed antenna has a smaller size than previous antennas. In addition, the proposed antenna has the widest operating bandwidth compared to previous studies and especially operates in HF/VHF/UHF bands. From the comparison, the proposed antenna shows good performance in terms of the operating bandwidth and a small size.