Improved Amplitude-Phase Calibration Method of Nonlinear Array for Wide-Beam High-Frequency Surface Wave Radar

Abstract

The amplitude and phase errors in array elements lead to uncertainties in the estimation of arrival angles (DOA), which, in turn, affect the accuracy of current measurements for high-frequency surface wave radar (HFSWR). To address this issue, this paper proposes a passive amplitude-phase self-calibration method for a wide-beam HFSWR system with a nonlinear array. This method utilizes the aggregation of the amplitude ratio among array elements to screen reception matrices of single DOA sources. Based on the differences in reception matrices, the amplitude error is calibrated. Moreover, the cost function is calculated using the multiple signal classification (MUSIC) algorithm, and the initial phase error is first obtained after triangular array dimensionality reduction. Then, the phase error is further calibrated through quadratic-form iterative optimization. This method has been validated through simulations and real measurements. An approximately 4-day dataset obtained via HFSWR is reanalyzed in this paper. After data calibration, the radar-estimated currents were in good agreement with the buoy-measured results, with a root mean square error (RMSE) as low as 0.06 m/s and a correlation coefficient (CC) of up to 0.88. The results indicate that this method is suitable for the amplitude and phase error calibration of nonlinear arrays in wide-beam HFSWR systems.