Design of a dual mode HF log-periodic antenna

In order to adapt to the propagation characteristics of the ionosphere and make HF antenna better match the ionospheric environment, an HF log-periodic antenna working on dual-mode propagation is designed. The antenna is composed of two log-periodic antennas in the vertical direction. The low elevation mode and high elevation mode are produced in the proposed antenna by in-phase excitation and inverse excitation respectively. The simulation and test show that the voltage standing wave ratio(VSWR) of the proposed antenna is less than 2.5 in the range of 6−30 MHz. The elevation of the antenna is of 20° and the gain is of 12 dBi for low elevation mode; for another mode, the elevation varying from 44° to 60° and the gain of 10 dBi are obtained. The proposed antenna works on two modes, which effectively improves the coverage ability of the conventional HF log-periodic antenna. The design lays a foundation for the further research of multipath separation of high frequency signals.