Maximum Likelihood HF Direction Finding Estimator for High Latitude Distributed Signals

摘要

This report details the development and evaluation of a new direction finding estimator, the Spread Maximum Likelihood algorithm, targeted for high latitude HF propagation conditions. Of particular concern are patches of enhanced electronic density and associated instabilities in the ionosphere which drift across the polar cap during darkness causing scattering of the propagated signal over a range of azimuth and elevation directions (i.e., the signals are spatially spread). The new estimator incorporates a spatial spreading model allowing it to simultaneously deal with both patch scattered signals and signals propagated by more normal propagation mechanisms, as well as to distinguish between the two types. Evaluation of the new estimator using both simulation and collected data show it to be considerably superior to both conventional and modern superresolution approaches for high latitude propagation conditions.