HF radio direction finding operating on a heterogeneous array: Principles and experimental validation

Array processing usually operates on identical sensors. In this paper an investigation is made to apply the direction finding algorithm MUSIC to an antenna array with nonidentical elements (heterogeneous array). This original solution is polarization-sensitive though it resorts to only one sensor at each point of the spatial sampling. As a major consequence of its structure, the computation of the MUSIC algorithm is based on an expression of the steering vector that integrates the spatial response of each sensor. This concept is then validated in the special context of HF radio direction finding, for which a deterministic model of the polarization at the exit of the ionospheric channel is derived. A multichannel radio receiving system has been developed and experimented using transmitters located more than 1000 km from the receiving site.