Analysis of ISAR images of a helicopter by a facet model

A triangular facet model of targets is proposed to generate ISAR images. Targets are composed of solid objects which are modeled by triangular facets. It is shown that the facets have an equivalent point-scatterer whose radar cross section and position depend on the shape of the triangle, the frequency and the angle of incidence. It is developed a shadowing algorithm to detect the facets which actually have influence on the signal received by the radar. This model is applied to study the ISAR images of a helicopter with two different transmitted signals, a rectangular pulse waveform and a linear frequency modulated waveform to identify the main features of the ISAR images for future classification purposes.