RCS Based Depolarizing Passive Tag with Improved Clutter Rejection for Potentiometric Gas Sensing

This paper presents a radar cross-section (RCS) based tag capable of detecting acidic/basic volatiles in the sensing environment. The sensor consists of two miniaturized annular slot antennas. One acts as the sensing element and the other as the reference. Both antennas are perturbed to provide a high cross-polarized scattering response. The cross-polarization-based interrogation technique provides robust detection against environmental scattering. A pH combination electrode coupled to a varactor diode provides the necessary transduction required for gas sensing. The concentration of the gas being monitored directly translates to the resonant frequency modulation of the sensing antenna.