Patent US 4,074,264

A time sampling adaptive clutter processor that samples on a scan to scan basis rather than on an area basis and in response to signals received from the object being interrogated develops a mean level value and a standard deviation value. The mean value and the standard deviation value may be provided by recursive type filters operating with scan to scan memories. The mean level value is then combined with the standard deviation value to provide a threshold that provides improved clutter detection especially with a condition in which a clutter variation from scan to scan is less than the clutter variation between areas in any one scan. The system may also include a valid target control to eliminate the detrimental effects on the threshold that may be caused by targets being tracked.