Fig. 5

Detection and separation of two objects with narrowband signals—more than an order of magnitude below standard limitations. a Photograph of the experimental layout where two square plates were placed at a separation of 32 cm away from each other. b–e Plots of cross-correlation as a function of the coherence length. Experimental data—blue points, piece-wise linear fit—red solid lines. Insets—uncertainty in target locations. b Free space scan—empty room. c, d Single targets without the presence of the other, in accordance with the theoretical plot in Fig. 3b. e Both targets present at the same locations as before. The measured distance between the targets is 35 cm, and it is close to the actual physical value (32 cm) . The correlation length in b–d includes the physical distance to targets (as seen in (a)) as well as added distance due to cables and delays in other electronic components