Biologically Inspired DOA Estimation Method for Small-Aperture Direction Finding HF Radar

A high-frequency (HF) surface-wave radar has been widely used in marine monitoring and vessel surveillance, among which compact ones, e.g., a crossed-loop/monopole antenna (CMA), are preferred in many scenarios for their low costs and easy maintenance. Relatively large error in the direction of arrival (DOA) estimation due to the small aperture involved is one major problem in such compact radars. To solve this problem, a biologically inspired DOA estimation method is proposed to improve the direction finding (DF) performance. The phase amplification mechanism of Ormia ochracea is imitated with a digital signal processor appended to the radar receiver. Then, the multiple signal classification (MUSIC) algorithm is used to estimate the DOA. For a two-element array with a small spacing, simulation results show that the proposed Bio-MUSIC method is superior to the conventional MUSIC in DOA estimation, and the combination of cosine and sine loops offers significant advantages over that by using two monopoles in terms of both accuracy and stability over different look angles. Also, compared with the CMA, the root-mean-square error (RMSE) is reduced by up to 56.99%. Experimental results demonstrate that, the total RMSEs of the ship coordinates obtained by Bio-MUSIC based on two cosine loops or one cosine loop plus one sine loop are reduced by up to 41.23% and are much less than the RMSEs obtained by MUSIC based on the CMA in most cases. Consequently, the biomimetic antenna array (BMAA) of loops with Bio-MUSIC can also be a good choice for marine applications.