The problem of the detection of radar targets with Gaussian statistics and with an assigned autocorrelation function is considered. The pertaining optimum detector is analysed and is found to be equivalent to a weighted sum of the squared moduli of the outputs of a bank of filters. A closed form expression for the false alarm and detection probabilities is used to compute the detection performance in various operating conditions, including mismatching with respect to the signal-to-interference ratio assumed in the design of the detector.