Cramer-Rao Bound for angle estimation with passive synthetic array

In this paper, synthetic aperture techniques are proposed to improve the accuracy of direction-of-arrival (DOA) estimator in passive synthetic array (PASA). First, we establish signal model for PASA, and then we derive the Cramer-Rao Bound (CRB) of DOA estimator under different statistical assumptions for the incident signals. In addition, several factors that would affect the DOA estimation accuracy are discussed. Results state that the size of synthetic aperture depends on the platform velocity and the sample rate. Therefore, besides signal-to-noise ratio (SNR) and the number of independent snapshots, the platform velocity and sample rate have important impact on the angle estimation accuracy. Finally, the theoretical analysis is verified by numerical simulations.