Enhanced CACIS configuration for direction of arrival estimation

In this letter, an enhanced coprime array with compressed inter-element spacing is designed for direction of arrival estimation. First, we analyse and conclude that the 0th sensor of coprime array with compressed inter-element spacing is redundant for the consecutive lags, thus it is rearranged to the negative part to obtain enhanced coprime array with compressed inter-element spacing. Then, on the basis of discussing the effect of the shift sensor on the difference co-array, the number of unique lags and the range of consecutive lags are derived. Theoretical properties show that the closed-form expressions of coprime array with compressed inter-element spacing and enhanced coprime array with compressed inter-element spacing are similar, while more difference lags can be generated from the latter. Moreover, larger inter-element spacing can slightly alleviate the mutual coupling. Numerical examples verify the advantages of enhanced coprime array with compressed inter-element spacing in direction of arrival estimation over coprime array with compressed inter-element spacing configuration and other coprime arrays.