Design and Development of a Unique Two-Way Field Probe System Using a Shielded Octocopter

Andrew J. Knisely


Accurate Radar Cross Section (RCS) measurements are most reliable if the uncertainty of these measurements can be quantified. The particular contributor to uncertainty examined in this research occurs when an electromagnetic (EM) wave transmitted from the radar deviates from its planar form as it traverses towards a target. The cause of this deviation results from interference within the test volume or medium between the radar and target. The method to quantify this uncertainty involves using a shielded octocopter as a unique two-way field probe. A canonical shield is required to encapsulate the octocopter, as it provides a predictable RCS profile used to quantify the test volume's effect on an EM wave. The shield designs to consider are canonical shapes drafted in CUBIT and measured in SENTRi software to simulate and assess backscatter RCS. A squat-cylinder shield is fabricated as a result of these simulations. High frequency RCS measurements (2 - 18GHz) of the shield reveal that a frequency less than 2.8 GHz effectively shields the octocopter from radar. Position and pose measurements acquired from the octocopter's u-blox GPS, Piksi DGPS, and INS modules are characterized to determine the uncertainty of the drone's navigation scheme as this can affect the accuracy of magnitude and phase measurements acquired when probing a test volume. The most effective position solution is acquired from the Piksi DGPS, accurate to 2.8 cm. The shielded octocopter developed in this research demonstrates that it is possible to use this system as a two-way field probe.