Abstract
A single helicopter-based high frequency (HF) antenna is proposed for direction finding (DF) using rotor-blade modulation. Without integrating additional antenna structures, a landing gear is utilized as a coupling element to excite a combination of significant characteristic modes of the helicopter through characteristic mode (CM) analysis. Different from traditional DF systems where multiple antennas required, incoming signal receptions are achieved by a single radiator in this work. The diversity in antenna radiation patterns is realized by incorporating main rotor-blade rotations. The incident signals can be measured as the blade rotates from 0° to 75°, where the helicopter-mounted antenna with each rotation angle is equivalent to one antenna element in a conventional DF antenna array. Correlation coefficients of complex CM and excited radiation patterns between the antenna with different blade rotation angles are calculated to demonstrate pattern diversity. Both Cramer-Rao bound (CRB) and multiple signal classification (MUSIC) algorithm are investigated using the complex CM and excited radiation patterns to validate the azimuthal DF capability of the helicopter-integrated single antenna.
Published Version
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