Feasibility Study on a Noncontact Remote-Sensing Vibration Transducer Using RF Polarimetry

Abstract

This paper presents a novel, noncontact vibration transducer system using radio frequency (RF) polarimetry, which allows for vibration measurements to be collected remotely and nonintrusively at a distance. Movement or vibration of an object within the RF propagation channel can alter the combined direct, reflected, and multipath RF signals, thereby changing the received signal's polarization. This paper presents the theory to analyze a RF signal's polarization for used as a vibration transducer. The proposed transducer leverages the entire bandwidth of the RF signal using the frequency-dependent polarization mode dispersion phenomenon that occurs in multipath channels. To analyze the approach, a software model has been constructed and used to simulate and characterize the transducer's performance. A feasibility comparison of this RF polarimetry technique to similar vibration transducers, including laser Doppler vibrometry, shows this new transducer to be easier and less expensive to implement without significant tradeoffs in performance. Finally, laboratory experiments verify the software model and demonstrate a real-world prototype implementation. The pure-tone vibration of tuning forks, the forced and free vibrations of a ringing telephone, and the rotational motion of a desktop fan have been measured and are presented as an evidence of this RF polarimetry transducer's diverse capabilities in vibrometry.