Performance Metric Issues for Space Time Adaptive Processing Methods

Space time adaptive processing was introduced to the radar community in the 1970´s as a multi-dimensional filtering method to discriminate moving targets from clutter when observed from an air-borne/space-borne multi-channel phased array radar. Numerous variants of this filtering technique have been developed and are often compared to some baseline performance with respect to output signal to interference plus noise ratio or minimum mean square error. Under clairvoyant conditions these metrics have a direct relation to probability of detection. However under non-clairvoyant conditions, such as with recorded data, probability of detection is not measured directly and secondary metrics, such as signal to interference plus noise ratio and minimum mean square error, are used to measure performance. This paper attempts to show a case where using a metric such as minimum mean square error can indicate erroneous favorable performance.