Performance analysis of a velocity filter bank

The velocity filter follows naturally from the derivation of the 3D (spatio-temporal) matched filter. It assumes constant velocity targets and that the spatial distribution of the targets remains unchanged. Typically the target velocity is unknown and a bank of velocity filters is implemented which covers the range of possible target velocities. Classically it is assumed that the gain of the velocity filter is proportional to the square root of the number of image frames filtered. As the number of frames is increased to enhance the filter gain, the width of the filter response in velocity space decreases. Consequently, more gain requires more filters to cover the same range of velocities. Each of the filters produces a set of false alarms. To maintain a constant false alarm rate, the detection threshold must be increased. The higher detection threshold reduces the probability of detection and offsets some of the gain achieved by the velocity filters. This performance trade is quantitatively analyzed.