Superresolution direction finding at HF for signals of unknown polarization

For direction finding (DF) with signals having an arbitrary polarization within the HF band, and indeed any frequency band, standard single polarization direction-finding algorithms will produce gross errors unless the array elements are well calibrated for the required polarization mode and are situated on a good site without the presence of nearby conductors which can produce mode conversion. In contrast, for a single mode array on a poor site or a mixed mode array the inclusion of polarization in the processing is vital for accurate DF results to be obtained. It has been found that the performance of the PolMUSIC algorithm improves as the array exhibits increasing diversity in its response to different polarizations. Therefore, having elements which are not aligned and with non-identical radiation patterns actually seems to be useful. The reason is that the array will span polarization space so that, in general, signal vectors will lie further apart in the signal space, thus aiding signal discrimination