On the Design of Vehicular Electrically Small Antennas for NVIS Communications

Design of low-profile vehicular on-the-move (OTM) wideband high-frequency (HF) antennas with 24-kHz instantaneous bandwidth for near-vertical communications is discussed. It is shown that multiarming significantly reduces the minimum antenna height, whereas the two-arm configuration is a tradeoff between antenna complexity and performance. A procedure for determining the minimum antenna height when the tuner loss is considered as a design parameter is introduced. The design evolves from a state-of-the-art magnetic dipole to a wire two-arm half-loop antenna (HLA). The profile for the amphibious assault vehicle (AAV) mounted antenna is 0.65 m (λ/230 at 2 MHz) for the parabolic shape and 0.50 m (λ/300) for the rectangular shape two-arm half-loop. The length of antenna base is 4.8 m (λ/31) and the width is 3.3 m (λ/45). A simple two-element tuner is considered in the scope of the results validation, along with the impedance and directivity patterns measurements on scaled 1/500 models.