The presentation of multi-antenna synthetic aperture radar (SAR) systems and signal processing relies on some basic concepts, particularly from signal analysis and processing. The correlation function is closely related to the convolution integral, and it also turns out to be useful in SAR imaging. In SAR systems, the signals are often transmitted over analog transmission facilities and are also processed digitally. To make the analog signals suitable for digital processing, make use of two operations: sampling and quantization. The sampling operation is used to convert a continuous-time signal to a discrete sequence. The quantizing operation converts a continuous-amplitude signal to a discrete-amplitude signal. The term aliasing refers to the distortion that occurs when a continuous time signal has frequencies larger than half of the sampling rate. The process of aliasing describes the phenomenon in which components of the signal at high frequencies are mistaken for components at lower frequencies.