Concept for a Spaceborne Synthetic Aperture Radar (SAR) Sensor Based on Active Phased Array Technology,

For surveillance with spaceborne remote sensing systems quite often a spatial resolution of 1 m or less is requested. In the paper a SAR concept is presented for a low flying satellite. Assuming a peak power of 5 kW and using active phased array technology a swath width of about 30 km at an off nadir angle of 35 deg is considered to be reasonable. A wide swath width combined with a high resolution can only be achieved if we use a fixed antenna beam for transmitting which illuminates the whole swath width, while a very narrow antenna beam scans the swath in the manner as the reflected pulse travels from the near range to the far range across the swath width. For the active antenna system a high efficiency of the transmitreceive-moduls, low losses in the feeding network and doubly polarized radiating elements with high polarization purity are considered of utmost importance.