The Fourier Diffraction Theorem relates the data measured during electromagnetic, optical, or acoustic scattering
experiments to the spatial Fourier transform of the object under test. The theorem is well-known, but since it is
based on integral equations and complicated mathematical expansions, the typical derivation may be difficult for
the non-specialist. In this paper, the theorem is derived and presented using simple geometry, plus undergraduatelevel
physics and mathematics. For practitioners of synthetic aperture radar (SAR) imaging, the theorem is
important to understand because it leads to a simple geometric and graphical understanding of image resolution
and sampling requirements, and how they are affected by radar system parameters and experimental geometry.
Also, the theorem can be used as a starting point for imaging algorithms and motion compensation methods.
Several examples are given in this paper for realistic scenarios.