Radar Terrain Return at Near-Vertical Incidence

Measurements have demonstrated that, with occasional exceptions, radar return from the ground is largely due to area scatter, even at angles of incidence near the vertical. An expression is derived here for a power superposition integral expressing the mean pulse envelope for the pulse returned from the ground to a radar. This integral is the convolution of the transmitted pulse form in power units with a function which includes effects of antenna pattern, ground properties, and distance. This function is generalized to include the effects of specular reflection and large isolated scatterers, as well as the more prevalent area scatter. While beam-width-limited illumination always results in inverse-square altitude variation for area scatter, it is shown that the variation with altitude for pulse-length-limited illumination varies from inverse-square to inverse-cube, and is a function of altitude as well as of ground properties and antenna pattern. Mean returned pulses are presented for various grounds and antenna orientations.