Post-Doppler methods decompose the STAP problem from an formula_8 adaptive filtering problem to formula_3 individual adaptive filters of length formula_2 (an formula_30 adaptive filter problem). By performing fixed Doppler processing, the adaptive filters become spatial only. Since the target response is already steered to a specified angle-Doppler location, the dimensionality can be reduced by pre-processing multiple Doppler bins and angles surrounding this point. In addition to reducing the dimensionality of the adaptive processor, this in turn reduces the number of required training data frames when estimating the interference covariance matrix since this quantity is dimension dependent.