An approach to control MTI filter order selections during search

Mobile, surface-based search radars contend with a variety of clutter conditions. Clutter spectral diversity is often chief among such variations. To address a range of possible clutter conditions, radars have employed a suite of selectable moving target indicator (MTI) waveforms. Among the useful waveform options is the order of the MTI filter. Low order MTI filters can be supported by just a few coherent pulses, and have nominal clutter rejection bands. High order MTI filters require more coherent pulses, but generally reject a broader clutter band by design. Some advantage can be realized from adaptively assigning MTI order to the various beam positions of a search volume, especially when that volume is comprised of a large number of such positions. If, in doing so, the radar assigns more pulses to beams in broad-band clutter subvolumes than to the remaining benign-clutter angles, then the average number of applied pulses-effectively the average dwell length-across the entire volume can be substantially less than that employed within those adverse angles. Controlled, angle-specific MTI filter order selections that adapt to the clutter at hand offer the potential of effectively managing clutter while minimizing the time required to search the entire volume. Appropriate control requires real-time, ongoing measurements of the clutter power spectral densities across the search volume. This paper introduces a control approach that includes no special measurements (i.e., it relies only on the normal search return), is very tolerant of multiple simultaneous clutter sources, but requires some additional signal processing using a special, three-channel architecture