Grating Lobe Suppression and Angle Estimation Based on Virtual Antennas Filling in Sparse Array

When the radar antenna spacing is larger than half wavelength, grating lobes appear in its antenna beam pattern. They could cause the ambiguity in the angle estimation of radar targets due to the similarity of amplitudes between grating lobes and the main lobe. To address such issue, this letter proposes a grating lobe suppression and angle estimation approach for sparse arrays by use of virtual antennas filling. It takes advantage of the distribution characteristics of grating lobes, and first obtains rough estimates of target angles. The least squares method is then employed to generate signals received by virtual antenna elements. Accordingly, the gaps between antenna elements of sparse array could be filled with those virtual ones to form an equivalent uniform full array. Hence, it achieves the grating lobe suppression as well as accurate estimation of target angles. Both simulations and experiments are carried out to verify its effectiveness in different types of sparse arrays.