Through-obstacle readout of chipless sub-terahertz frequency-coded indoor landmarks

A possibility to implement a sub-THz-based indoor self-localization system is to place chipless landmarks with known positions inside the rooms. They are considered to be freestanding, attached to the walls or roof. However, little to no attention has been given to the possibility of placing the landmarks above roof tiles or behind walls. In this paper, we evaluate the attenuation in received signal for two chipless landmarks, namely aperture-coded and cavity-coded landmarks, for polyvinyl chloride (PVC) samples with different thicknesses. The PVC presents an attenuation of 11.5 dB/cm at 300 GHz, close to common cement mortar. The losses in the received signal for both landmarks match the expected attenuation and their frequency-coded responses are successfully readout for different PVC thicknesses. It is also shown that the decrease in readout range due to the obstacles can be easily predicted by characterizing their absorption coefficient.