Relationship Between DOA Estimation Error and Antenna Pattern Distortion in Direction-Finding High-Frequency Radar

The direction-finding high-frequency radars (HFRs) are widely used for remotely sensing the ocean surface currents. However, the performance of the direction-finding HFR is limited by the inevitable distortion of the actual antenna pattern of the compact monopole-cross-loop antenna, because the distortion of the antenna pattern leads to errors on the direction-of-arrival (DOA) estimation, which results in correctly determined radial velocities being placed into the incorrect bearing sectors. In this letter, a model determining the DOA estimation error (DOAEE) stemming from the antenna pattern distortion (APD) is presented with a detailed analytical derivation. This model suggests that the DOAEE only depends on the relative distortion of the two orthogonal loops. To validate the correctness of the proposed model, simulations are carried out. In addition, the simulation results show that the model well captures the actual relationship between the APD and the DOAEE. Moreover, a data set collected by a direction-finding HFR system and a synchronized automatic identification system receiver is used to further validate the proposed model. The precessing result of this data set demonstrates that the model-calculated DOAEE and the actual DOAEE are in good agreement with a correlation coefficient of 0.92 and a root-mean-square error of 9°, which provides solid evidence to verify the validity of the proposed model in determining the relationship between the DOAEE and the APD.