Wireless interrogation of antenna sensors for strain monitoring

Abstract

This paper presents a wireless interrogation system using impedance switching and amplitude modulation to detect the resonant frequency shift of antenna sensors under external load. The wireless antenna sensor, constructed by a few microwave components, is able to detect small strain changes without requiring any local power source. First, the principle of operation of the unpowered wireless interrogation system is discussed, followed by the characterization of the effect of applied strains on the resonant frequency of the antenna sensor. The shifts of the resonant frequency under different loads were correlated to the strains experienced by the antenna sensor. The experimental results agreed well with the analytical prediction.