New fan filters for multiple-frame track-before-detect applications

Clutter and noise can preclude single-frame detection of moving targets in image sequences, necessitating the application of multiple frame (3-D) filters. Two new types of 3-D fan filter show considerable promise in this application. The first type of fan filter suppresses all clutter and other objects whose velocity is contained in a user-specified velocity set. The ability to reject clutter over a continuous range of velocity is a great advantage of this class of filter with respect to velocity-notch filters such as the frame-to-frame subtracter. The second type of fan filter passes without attenuation all objects whose velocity is contained in a user-specified velocity set while providing the maximum possible suppression of broad-band noise. For detecting a target of unknown velocity in broad-band noise a bank of this type of fan filter can replace a band of 3-D matched filters, with the advantage of avoiding the velocity mismatch losses of the 3-D matched filter.