# A Low-Profile Ferrite Dipole VHF Antenna for Integrated Mast Applications
## 3 Experimental Verification
To examine the performance of the proposed antenna mounted on the integrated mast in this case, the shape of the OPV is modeled simply (see Figure 8b). The length and beam of the OPV are 108.4 m and 16 m, respectively, and all surfaces are implemented as conductors. The proposed antenna is mounted on the integrated mast of the OPV with vertical (in \(x\)-axis) and horizontal (in \(y\)-axis) arrangements, as shown in Figure 8c,d, respectively. \begin{table}
\begin{tabular}{c c c c} \hline
**Ref.** & **Peak Gain (dBi)** & **Overall Dimensions L\(\times\)W\(\times\)H (\(\lambda_{L}^{3}\))** & **Weight (kg)** \\ \hline
[18] & \(-9\) & \(0.04318\times 0.06096\times 0.00508\) & 9.07 \\
[19] & Approx. \(-0.5\) & \(0.1016\times 0.01016\times 0.00381\) & - \\
[20] & Approx. \(-6\) & \(0.0381\times 0.0381\times 0.01524\) & - \\ This work & \(-2.44\) & \(0.0636\times 0.0112\times 0.0008\) & 1.45 \\ \hline \end{tabular} \(\lambda_{L}\) is the free-space wavelength at the lowest operating frequency of 30 MHz.  
\end{table} 
Table 2: Performance comparison with a previous VHF antenna. Figure 7: Simulated and measured radiation patterns of the proposed antenna at 30, 100, and 300 MHz: (**a**) \(xz\)-plane and (**b**) \(yz\)-plane. Figure 9 presents the simulated realized gains of the proposed antenna when mounted on the integrated mast of an OPV. The simulated realized gains of the ferrite dipole antenna on the finite flat ground plane (as shown in Figure 6) is also illustrated here as a reference. By mounting the proposed antenna on the integrated mast, the overall structure of the OPV becomes the ground of the antenna. With an integrated mast, the realized gains at low frequencies are higher than that of the proposed antenna due to a significant increase in the size of the ground plane. However, at high frequencies, the realized gains are reduced as compared to that of the proposed antenna. This is mainly due to the electromagnetic waves scattered by the structure of the OPV. The realized gains of the proposed antenna on the integrated mast on the \(x\)-axis and \(y\)-axis vary from \(-19.13\) to \(-5.39\) dBi and from \(-17.69\) to \(-4.82\) dBi, respectively. Simulated far-field radiation patterns of the proposed antenna mounted on the integrated mast of an OPV on two cutting planes (\(xz\)-plane, \(yz\)-plane) are depicted in Figure 10. It can be seen that the radiation patterns are influenced less by the OPV structure at 30 MHz due to the long wavelength; however, when the frequency is increased, the radiation patterns are influenced more by the OPV structure. The \(xz\)-plane and \(yz\)-plane patterns are directional and omnidirectional patterns, respectively. The proposed antenna is mounted on the front of the integrated mast, and the radiated directional wave is realized in the \(+z\)-direction. Due to the influence of the bow of the OPV, the directional pattern is tilted toward the \(-x\)-direction. Figure 8: Proposed antenna mounted on the integrated mast of an offshore patrol vessel (OPV): (**a**) Photograph of a Holland-class OPV. (**b**) 3-D modeling of an OPV with the integrated mast. The proposed antenna mounted on the integrated mast of the OPV on the (**c**) \(x\)-axis and (**d**) \(y\)-axis. Figure 10: Simulated radiation patterns of the proposed antenna mounted on the integrated mast of an OPV at 30, 100, and 300 MHz: (**a**) \(x\)-axis; (**b**) \(y\)-axis. Figure 9: Simulated realized peak gains of the proposed antenna mounted on the integrated mast of an OPV and flat ground conditions.