Azimuth Multi-Antenna SAR
In synthetic aperture radar (SAR) remote sensing, a broad footprint implies that fewer missions are required to map the region of interest. More importantly, for general applications, this will also imply that a given region of the earth can be repeatedly mapped with a greater frequency. An efficient SAR should provide high-resolution over a wide area of surveillance, although there is a contradiction between azimuth resolution and swath width. A good azimuth resolution requires a short antenna to illuminate a long synthetic aperture which results in a wide Doppler bandwidth, but this calls for a high pulse repeated frequency to sample the Doppler spectrum. The displaced phase center antenna (DPCA) technique was proposed to improve the performance of moving target indication (MTI) radars mounted on moving platforms. Prior to the invention of the DPCA technique, airborne MTI radars suffered from the butterfly effect, a phenomenon associated with clutter leakage that causes wing-shaped patterns to appear on the position indicator.