Source separation in the HF band using a compact system of direction finding

A compact direction finding system has been developed which operates using a set of seven collocated HF active antennas. It is described in Marie et al. (2000). It has been shown that the estimation of the direction of arrival can be efficient as the diversity of their spatial responses replaces the space diversity of a classical array. That technique implies however a particular computation of the MUSIC algorithm, noting that such an array is heterogeneous. A significant number of experiments, which involved broadcast transmitters more than 700 km from the receiving site, validated this concept. Later source separation of HF multipaths was investigated, aiming to reduce the fading amplitude and to improve the bit error rate in a digital transmission. The paper propose a comparison of two possible techniques : a classical spatial filtering (least mean squares filter) and a blind algorithm resorting to second order statistics.