2D-DOA estimation with difference and sum coarray for L-shaped distributed array

This paper first constructs a novel L-shaped distributed array for two-dimensional (2-D) direction of arrival (DOA) estimation. Based on this, difference and sum coarrays (DSCAs) of the distributed nested array and the improved distributed array are obtained from the spatial and temporal information of the received data. And the closed-form expressions about the sensor locations, DSCA, and degree of freedom (DOF) are derived. The formed virtual array is composed of two orthogonal portions with identical distributed uniform linear arrays. While increasing DOF for the distributed nested array, the improved distributed array achieves a larger continuous aperture. Next, taking average of the repeat elements in the virtual array is equivalent to increasing the number of snapshots, which improves the estimation accuracy. Then, spatial smoothing is performed to restore the rank of each covariance matrix. Finally, the dual-size ESPRIT algorithm is applied to estimate the azimuth and elevation angles, respectively. Simulation results are conducted to demonstrated the effectivity of the proposed method and the high DOF of the improved distributed array.