A method of direction finding operating on an array of collocated antennas

This paper presents an original method of direction finding operating on an array of collocated antennas. At first, we derive the classical MUSIC algorithm for an heterogeneous array, i.e. made up of different sensors: their complex directional responses, which are supposed to be well known, are integrated in the normalized steering-vectors. We underline (the advantages induced by this technique in the field of radio direction finding, especially as two types of polarization are received (right or left circular polarization in the VHF range, ordinary or extraordinary polarization in the HF range). Then, we show that the diversity of the sensors can replace to some extent the space diversity usually provided by classical arrays. Actually, the array manifold does not only depend on the geometry but also on the directivity functions of the sensors. In these conditions, it becomes feasible to find the directions of arrival with a small array aperture, and possibly with collocated sensors. Finally, we present experimental validations in the HF (3-30 MHz) range.