Synthetic aperture GPS Signal Processing Concept and Feasibility Demonstration

m a y / j u n e 2 0 0 9 InsideGNSS 37 Synthetic aperture techniques combine data obtained from multiple sensors — or one sensor moving among multiple locations, or both — to construct a single image. These techniques have been widely researched, developed, and applied in the area of radar systems. This article discusses efforts to extend synthetic aperture concepts to GPS signal processing, exploiting the beam steering capabilities of synthetically generated phased array antennas. In it, we will describe the fast Fourier transform (FFT)–based method used to simultaneously steer a synthetic array’s beams in multiple directions. We will also discuss the results of simulator and flight tests to demonstrate the efficacy of synthetic beam steering techniques for GPS antennas. Development of GPS-based SARs will enable high-resolution imaging capabilities using passive receivers of GPS signals and allow 24-hour global availability of imaging technology. It represents a dual-use technology that could support military applications such as imaging of military ground fleet hidden under foliage, as well as humanitarian applications such as detection of unexploded ordnance.