A System for Remote Parametric Detection, Localization, and Identification of Passive Tags using Radio Frequency and Ultrasound Waves

Researchers in the Arbabian Lab have developed a system that uses a combination of radio frequency (RF) electromagnetic and ultrasound (US) waves to detect, localize, and identify multiple battery-free tags. The system consists of any number of small (centimeter- or millimeter-sized) battery-free tags to be localized, as well as one or several readers capable of providing tag location and velocity estimates at high frame rate for tags up to several meters away from the reader(s). Each reader transmits continuous-wave (CW) RF and pulsed US to regions of interest; a tag in that region reradiates RF waves that are modulated by the pulsed US incident on the tag. The reader detects this modulation in the returning RF waves and uses it to detect, localize, and identify that tag. Each tag consists at least of an RF antenna connected to an US transducer by a passive electrical network, which ideally is a network that matches the impedance of the transducer to that of the antenna at the RF frequency of operation. Each reader consists at least of an US transmitter combined with an RF transceiver, and may include any or all of the following parts: a pulsed US transmitter, an array of US transducers, a CW RF transmitter, an array of RF antennas, an RF self-interference cancellation system, an RF demodulation system, and firmware/software to stitch together location and velocity estimates of tags into continuous tag paths through space.

Stage of Research