Frequency Coded Retroreflective Landmark for 230 GHz Indoor Self-Localization Systems

This paper presents a planar Luneburg lens frequency-coded retroreflector based on a high-resistive silicon (HR-Si) photonic-crystal (PhC) high-Q tag with two resonators working at 237 GHz and 243 GHz. A characterization of the retroreflector, including the readout of the resonance frequency of the resonators, is performed at 30 cm over 130-degree angular range in azimuthal plane. The measured gain of the lens antenna is 15.9 dBi at a frequency of 240 GHz and the radar-cross section (RCS) of the frequency-coded tag landmark achieves -30 dBsm at 237 GHz.