Scripps Institution of Oceanography

Detailed analysis of the compact antenna array patterns and the internal signal processing within the MUSIC algorithm leads to a goodness-of-fit quality metric for the output radial current velocities and bearings produced by the HF RADAR system. To achieve this, some theory behind the MUSIC direction finding algorithm, describing its Direction of Arrival (DOA) metric, is first presented. MATLAB simulations are conducted and statistics are collected on the DOA metrics. The magnitudes of these metrics are directly related to the quality of the bearings produced by the MUSIC algorithm. This research provides HF RADAR users with a practical quality metric for the radial current velocities and their associated bearings produced by the HF RADAR system. Eliminating data with low DOA metrics can decrease the RMS error (by an average of 2.33 cm/s) in up to 70% of the spatial RADAR grid, however comes at a cost of an increase the RMS error(by an average 1.08 cm/s) in 20% of the same grid.

Quality of measured antenna patterns is paramount to the accuracy of the MUSIC algorithm bearing output. Ambiguities, as well as other aspects of the measured antenna patterns that are detrimental to quality, are discussed. MUSIC results over land bearings are explained, as well as the clustering of radials along the edges of the antenna patterns near land. Best practices are presented to eliminate all of these effects.

Criteria (“MUSIC parameters”) for deciding whether a given MUSIC radial velocity originates from one or two bearings are defined and discussed. Varying the MUSIC parameters can decrease error depending on the expected current being measured. A current that generates a majority of radial velocities from only one bearing should have the MUSIC parameters set to favor single bearing solutions, and vice-versa. Simulation results are provided in the Appendices.