High-Resolution Drone-Borne SAR using Off-the-Shelf High-Frequency Radars

This paper examines real-world, drone-borne SAR imaging using off-the-shelf radars transmitting at frequencies of 24 and 77 GHz. Drone-borne systems have the potential to make SAR imaging affordable as well offering access to otherwise difficult locations. Transmit powers and sensor sizes, in general, are restricted due to the limited payload capacities of small drone platforms. Hence, they are better suited to short-range applications of up to a few hundred meters in range. At high frequencies, the radar form factor is reduced and the potential for obtaining very fine resolution imagery is improved. However, wind turbulence may cause fluctuations in the drone's trajectory due to its lightweight. This instability, combined with the low accuracy of current on-board GPS/INSs, makes image formation more challenging. Further, short-range operation leads to significant space-variant errors, limiting the number of prominent targets observable within the beam. We are investigating the SAR imaging performance for conventional, compact high-frequency radars, we are presenting the concept of an algorithm capable of handling spatially variant motion errors, and we test the validity of our approach using a technology demonstrator built at the University of Birmingham. For the first time, we present short-range, fine resolution imagery (6cm x 32cm) of an extended target area using drones at 24 and 77 GHz using this approach.