Harmonic Response Characterization of Mobile Devices for Application in Avalanche Rescue

A harmonic radar approach is capable of detecting electronic devices by exploiting nonlinearities, particularly those present in RF frontends. We outline a novel approach to characterize harmonic responses, compensating for the measurement setup. Results are, for the first time, comparable by maintaining a constant power density at the DUT and normalizing the harmonic response to reflected effective isotropic radiated power (EIRP) over frequency. These setup-independent results pave the way to a dataset of harmonic response patterns, enabling the development of an avalanche search-and-rescue radar for locating mobile devices of victims. The harmonic response pattern in two frequency ranges of several recent smartphones, wearables and UHF RFID tags is presented. Notably, UHF RFID tags exhibit a promising, broad response, exceeding - 60 dBm EIRP when illuminated with a 0.6-1 GHz, 0.1 W/m² signal.