The fourth-order difference co-array construction by expanding and shift nested array: Revisited and improved

Abstract

The expanding and shift scheme with two nested arrays (EAS-NA-NA) is easy to construct and effective for achieving large number of degrees of freedom (DOFs), which is one of the representative sparse arrays exploiting the fourth-order difference co-array (FODC). In this letter, it is found that by suitably enlarging the sensor spacing of the expanded nested array in the original EAS-NA-NA, EAS-NA-NA with larger spacing (EAS-NA-NALS) can be built and the DOFs available for direction of arrival (DOA) estimation can be remarkably increased. The proposed EAS-NA-NALS can achieve the longest consecutive virtual array among the well-known FODC-based sparse arrays when the number of physical sensors is large. Simulation experiments are conducted to verify the DOA estimation performance of EAS-NA-NALS and several representative sparse arrays are taken for comparison. Experimental results show that EAS-NA-NALS can achieve more DOFs than other sparse arrays, thus acquiring the improved performance for DOA estimation.