We investigate the detection and localization properties of harmonic tags working at microwave frequencies. A\ntwo-tone interrogation signal and a dedicated signal processing scheme at the receiver are proposed to eliminate\nphase ambiguities caused by the short signal wavelength and to provide accurate distance/position estimation even\nin the presence of clutter and multipath. The theoretical limits on tag detection and localization accuracy are\ninvestigated starting from a concise characterization of harmonic backscattered signals. Numerical results show that\naccuracies in the order of centimeters are feasible within an operational range of a few meters in the RFID UHF band.
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