Fig. 4: Measured results of the qHT when localizing a drone.

a Schematic view of the experimental setup we used to assess the azimuthal distance of a drone at different distances from our interrogation node. The qHT is mounted on top of the drone and a signal generator connected to a power amplifier is used to remotely interrogate the qHT. The qHT responds with a frequency comb that is received by a spectrum analyzer. Measured frequencies for the strongest tones of the generated frequency comb vs. the corresponding extracted \({P}_{r}\) values when the distance is spanned by the drone while flying (b) or when the drone is manually moved (d). c, e The extracted drone’s distance from the interrogating node vs. the distance measured with the ruler. The extracted distance is found by: (i) extracting \(\Delta f\); (ii) using the extracted \(\Delta f\) value to find \({P}_{r}\); (iii) using the found \({P}_{r}\) value and the Friis space propagation model to determine \(d\). The reported values of \(d\) have been extracted from \(\Delta f\) for both the case in which the drone is flying (c) and the case in which it is manually moved (e).