Quantifying and Reducing the DOA Estimation Error Resulting from Antenna Pattern Deviation for Direction-Finding HF Radar

Abstract

High-frequency (HF) radars are routinely used for remotely sensing ocean surface currents. However, the performance of the most widely used direction-finding HF radar is degraded due to the effect of the inevitable deviations of actual antenna pattern on the direction of arrival (DOA) estimation. In this paper, we quantify the DOA estimation error resulting from the deviation of the actual antenna pattern from the ideal one. Theoretical analysis and field experiment results suggest that the ratio of the deviations for the two loops dominates the DOA estimation error. Thus, eliminating the effect of the antenna pattern deviations on DOA estimation error is transformed into eliminating the effect of this ratio. From this, a calibration method based on the time-averaged local spatial coverage rate (TLSCR) is proposed to reduce the effect of the antenna pattern deviations on current extraction, which uses the ideal antenna pattern to estimate the DOA of the echoes. To validate this proposed calibration method, we assess the radar-derived radial velocities by comparing with in situ observations. The comparison results indicate that the proposed TLSCR calibration method can effectively reduce the DOA estimation error and improve the performance of the direction-finding HF radar in current observation.

Estimation of Coastal Currents Using a Soft Computing Method: A Case Study in Galway Bay, Ireland

“…There are two commonly used types of HFR observation systems: Beam-forming (e.g., CODAR and ocean state measuring and analyzing radar (OSMAR) system) and direction-finding (e.g., WERA HFR system) [26][27][28]. The former HFR system uses a distributed array of elements to electronically scan ocean surface with a relatively narrow beam; while the latter HFR system uses a small-aperture antenna to from a quite broad beam for obtaining sea echoes [29]. A land-based CODAR HFR observation system consisting of two radars has been deployed in the Galway Bay area since 2011, as shown in Figure 1.…”

Array‐based target localisation in ATSC DTV passive radar

“…The derivation above assumes that the complex scaling is fixed for each element . However, it has been noted in the literature that array element pattern changes due to mutual coupling are dependent on the bearing of the impinging signal [32, 33]. Therefore, it is likely that the complex scaling and the calculated correction factors have a bearing‐dependence as well.…”

Editorial for Special Issue “Ocean Radar”

“…The direction of arrival (DOA) estimation is a key measure of HF radar performance. Through both theoretical and experimental analysis, Lai et al [6] found that the DOA error significantly depends on the ratio of the antenna pattern deviations of two loops for a cross-loop system. Based on this finding, the authors proposed a new method which takes advantage of time-averaged local spatial coverage rate (TLSCR) for mitigating the DOA estimation error.…”