Multiple-input multiple-output (MIMO) techniques have brought significant advances to wireless communications. In recent years, researchers have sought to bring similar advances to radar using MIMO. One specific area that has received relatively little attention is MIMO synthetic aperture radar (SAR). The advantages that MIMO might provide to SAR are not well represented in literature. This paper discusses the motivation for MIMO SAR and derives MIMO signal correlation in order to determine what imaging geometries are required for MIMO SAR