# A Low-Profile Ferrite Dipole VHF Antenna for Integrated Mast Applications
## 3 Experimental Verification  
Based on the optimized design parameters, the proposed antenna was fabricated for an experimental demonstration. Figure 5a shows a photograph of the fabricated antenna. The antenna has a total weight of 1.45 kg and electrical dimensions of approximately \(0.0636\times 0.0112\times 0.0008\lambda_{L}^{3}\) at the lowest operating frequency of 30 MHz. The antenna is mounted at the center of a finite ground plane with a size of 900 mm \(\times\) 900 mm. The ferrite cells are attached to the ground plane using double-sided tape (see Figure 5b). To simplify the fabrication, the conductor of the loop feeding structure is made of copper tape and is directly attached onto the Styrofoam covering the ferrite dipole structure. The loop feeding structures are connected to the ground plane by silver conductive epoxy (CW2400, Chemtronics). The inner and outer conductors of the coaxial cable are correspondingly connected to the upper and lower arms of the one-quarter rectangular loop, which is placed at the center by soldering. Figure 5c presents a picture of the antenna measurement set-up. Radiation patterns were measured at the outdoor measuring station of the Korea Research Institute of Standards and Science. The proposed antenna was used as a receiving antenna (Rx), and both the transmitting (Tx) and receiving (Rx) antennas are positioned 6 m above the ground. Figure 6 presents the simulated and measured results of the Voltage Standing Wave Ratio (VSWR) and the realized gains of the proposed antenna. The measurement of the VSWR was done using an Agilent 8510C vector network analyzer. As observed in Figure 6, the simulated and measured results of the VSWR are in good agreement in the entire operating frequency band. The simulated and measured realized gains in the broadside direction (\(\theta=0^{\circ}\)) range from \(-29.26\) to \(-0.83\) dBi and from \(-31.48\) to \(-2.44\) dBi, respectively. The slight discrepancies between the simulated and measured results are mostly caused by fabrication imperfections and/or experimental tolerances due to calibration and reflected and scattered waves from the ground. Figure 4: Simulated realized vertical-polarization gains at the main beam direction (\(+z\)) of the ferrite dipole antenna with different numbers of loop feeds. Table 2 shows a comparison of certain key features between the proposed ferrite dipole antenna and a previous VHF antenna described in the literature [18, 19, 20]. Clearly, the antenna presented here has a much lower height and a lighter weight as compared to the antennas reported in earlier studies. Figure 5: (**a**) Top view of the fabricated proposed antenna. (**b**) Top view of the fabricated ferrite. (**c**) Antenna measurement set-up. Figure 6: Simulated and measured Voltage Standing Wave Ratios (VSWRs) and realized gains of the proposed antenna. Compared to other designs [18; 20], the proposed antenna provides a much higher gain. Although one earlier design [19] has a higher gain, the proposed antenna is smaller and has a much lower height. This makes the proposed antenna an extremely low-profile, lightweight, and high-gain VHF antenna that is very suitable for integrated mast applications. Figure 7 shows the simulated and measured radiation patterns at three different frequencies of 30, 100, and 300 MHz on the \(xz\)-(\(\phi\) = 0\({}^{\circ}\)) and \(yz\)-(\(\phi\) = 90\({}^{\circ}\)) planes. The dashed and solid lines represent the results of the simulation and the measurement, respectively. The values of the radiation patterns indicate the vertical-polarization gains of the proposed antenna. It can be observed that the proposed antenna radiates omnidirectional and directional waves in the low and high frequency bands, respectively. In addition, the simulated and measured results of the radiation patterns are in good agreement. Figure 8a shows a photograph of a Holland-class OPV of the Royal Netherland Navy with an integrated mast.