Explicit Joint Resolution Limit for Range and Direction-of-Arrival Estimation in MIMO Radar

Resolution capability is an important metric for radar parameter estimation. However, the resolution limit for multiparameter estimation has not been adequately studied. In this article, we exploit results from Shannon's information theory to derive a joint resolution limit (JRL) for range and direction-of-arrival (DOA) estimation in multiple-input multiple-output radar. Based on the general model, the closed-form expression of scattering information is obtained for two targets with complex Gaussian scattering properties. A critical state is considered where the quadrature component of the scattering information is 1 bit, and corresponding intervals of range and DOA are defined as the JRL. Under the assumption of closely spaced targets, the approximated explicit JRL is derived by a second-order Taylor series, which indicates that the JRL is inversely proportional to the number of array elements, the square root of the signal-to-noise ratio, and the signal bandwidth to the carrier frequency ratio. In addition, closed-form approximations for a range resolution limit and a DOA resolution limit are obtained as special cases. It is indicated that these resolution limits are general and not based on any specific resolution method. The accuracy and the validity of the proposed resolution limits are verified by numerical simulations.