Analysis of STAP algorithms for cases with mismatched steering and clutterstatistics

In the majority of adaptive radar detection algorithms, the covariance matr ix for the clutter-plus-noise is estimated using samples taken from range c ells surrounding the test cell. In a nonhomogeneous environment, this can l ead to a mismatch between the mean of the estimated covariance matrix and t he true covariance matrix for the test cell, Further, an inaccurate target steering vector may also be employed. Closed-form expressions are provided, which give the performance for such cases when any of a set of popular spa ce-time adaptive processing (STAP) algorithms are used. The expressions are exact for some interesting cases. For some other cases, it is demonstrated that the expressions provide good approximations to the exact performance. To simplify the analysis, the samples from the surrounding range cells are assumed to be independent and identically distributed, and these samples a re assumed to be independent from the sample taken from the test cell, A sm all number of important parameters describe which types of mismatches are i mportant and which are not. Monte Carlo simulations, which closely match th e predictions of our equations, are included.