Design of platform-mounted HF/VHF antennas using the characteristic modes theory

In many HF/VHF communications applications, the antennas are mounted on vehicular platforms. As such, the combination of the antenna and the platform constitutes the main radiating structure. However, most HF/VHF antennas are generally not designed with the presence of the platform in mind. In this paper, we report the results of a preliminary study in which we investigate how the performance of a platform-mounted antenna can be improved by treating the platform as part of the antenna. Specifically, we examine a simple rectangular-box-shaped platform and examine how the mounted antenna can be used to excite the natural resonant modes of the platform. Since the platform has generally larger physical dimensions than the mounted antenna, efficient excitation of the platform´s natural resonance modes is expected to improve the radiating performances of such low-frequency HF/VHF antennas.