DOI: 10.1109/TMTT.2026.3703958

IEEE Xplore: https://ieeexplore.ieee.org/document/11575256

Phrase Summary:

Retrodirective RFID backscattering-based microwave permittivity sensor.

Sentence Summary:

This article presents a portable retrodirective microwave permittivity sensor based on RFID backscattering with a CMOS readout that overcomes nonlinear sensor response, dependence on bulky laboratory instrumentation, and sensitivity to reader–tag misalignment.

Paragraph Summary:

This article presents a portable retrodirective microwave permittivity sensor based on radio frequency identification (RFID) backscattering that overcomes nonlinear sensor response, dependence on bulky laboratory instrumentation, and sensitivity to reader–tag misalignment.  The proposed architecture monitors amplitude in the ISM band at 2.45 GHz and translates permittivity-induced resonance shifts into a direct voltage readout.  A dual-layer high-gain antenna extends the wireless interrogation range to 10 cm, a Koch-fractal complementary split-ring resonator (CSSR) converts dielectric loading into amplitude modulation, a custom CMOS rectifier’s nonlinearity compensates for the compressive response of the resonator tag for a linear voltage-permittivity relationship, and a retrodirective Van Atta (VA) array re-radiates the backscattered energy in cross-polarization toward the interrogating source regardless of the incidence angle.