Establishing antenna and receiver characteristics for addressing multipath interference for unmanned aerial vehicle (UAV) navigating urban canyons

Unmanned aerial vehicles (UAVs) flying through urban canyons are subject to multipath signals as a result of reflection, refraction, and diffraction of satellite signals travelling to the receiver; this can lead to positional inaccuracies in this time-critical operation that can lead to crashes. Indeed, analytical models show that for a GPS L1-C/A (coarse or clear signal/acquisition), the time to detect a satellite signal increases considerably under conditions of multipath interference. Traditionally, two different approaches have been taken to dealing with the multipath problem. One approach involves signal processing and the other involves designing an antenna (spatial processing) capable of rejecting multipath signals. While several signal processing solutions for dealing with multipath impact exist, they require advanced receiver architectures that either mitigate the effect of multipath signals or use signals identified as multipath to enhance location accuracy. A question that remains to be answered is whether or not acquisition time for satellite signals can be optimized by carefully matching antenna and receiver.