Effects of obscurant materials on millimeter wave seekers

Millimeter-wave radar seeker functions for detecting, classifying, identifying, and tracking ground targets are described. The adverse effects of both naturally occurring and man-made obscurant material are discussed. Obscurants considered include clear air components, fog, rain, frozen hydrometeors, and specially designed smokes. The phenomenological characteristics that affect radar performance are discussed in terms of signal absorption, signal backscatter, signal depolarization, and signal scintillation. It is noted that signal attenuation, via absorption, remains the major justification for creating man-made obscurant materials for protecting targets from millimeter-wave radars. While a minimal obscurant backscatter has the advantage of not giving away target area positions, a higher obscurant backscatter can itself degrade radar target detection by creating false targets and by decreasing the target-to-interference power ratio. The effects of conducting obscurant materials which remain spatially aligned in a wind field and the actual inhomogeneities in an obscurant cloud are discussed