Our main goal is a closed-form expression for the steady-state output signal-to-noise ratio (SNR) of an

-element adaptive array excited by one desired narrow-band signal and

narrowband jammers. This is facilitated by representing each excitation by a complex

-dimensional vector-the excitation vector. We show that the important system parameters are functions of scalar products of pairs of these exctiation vectors. In particular, the normalized output SNR of the array is shown to be the ratio of determinants whose elements involve these scaler products. Such determinants are also shown to be involved in the expressions for the optimal array weights.