High-Accuracy Localization of Passive Tags With Multisine Excitations

This paper proposes an extensive study of multisine excitations to enable high-accuracy localization of battery-less tags, by harvesting the higher order harmonics, generated by the rectifier nonlinearity. Usually, these harmonics are either filtered out or terminated, to increase the conversion efficiency. A dual-mode rectifier with the output section splitted into two paths is designed. One dc path is the common one used to deliver the converted dc power to an optimum load and the second path is broadband and collects the higher harmonics obtaining an ultrawideband radiated signal to communicate with the receivers for tag localization. To this purpose, a variety of multisine excitation signals, with different tones, spacing among tones and bandwidth, is accurately evaluated to characterize the system-level localization performance. Both the modeled and experimental results are presented demonstrating the excellent performance of such a dual-mode rectifier, despite of the limited add-on circuitry if compared to those used in standard rectennas. For an average received power of -10 dBm, measurements show that the localization of a tag with centimeter-level accuracy can be achieved at more than 10 m distance from the receivers having a 4 dB noise figure.