The basis for processing synthetic aperture radar signals is derived and the limitations imposed by unwanted platform motion discussed. The hardware realization of both unfocused and focused SAR processing is briefly described in terms of a block diagram and of the required complex multiplication time and storage capacity. Some additional processes are also briefly outlined.It is not possible to describe in great detail the full processing required to produce SAR images. Each application has its own priorities and problems. Instead an attempt has been made to present an overview of the requirements and the likely limitations affecting the processed image.