High-Sensitivity Microwave Displacement Sensor Based on a Cylindrical Dielectric Resonator With Split-Frequency Response

This letter presents, for the first time, a highly sensitive microwave sensor for linear displacement detection based on the split-in-frequency principle using a cylindrical dielectric resonator (CDR). The sensor consists of a stator (substrate with a rectangular slot) and a mover (CDR), where displacement is measured by tracking resonant frequency splitting induced by symmetry breaking. When the CDR is centered over the slot, the system exhibits a single transmission zero (f₀); any displacement breaks the symmetry, generating two distinct transmission zeros (Δf), which linearly correlate with displacement. Leveraging this mechanism, the sensor achieves an unprecedented sensitivity of 375 MHz/mm over a 0-3 mm range, the highest reported for split-in-frequency microwave resonator-based displacement sensors, while maintaining excellent linearity. A prototype is fabricated and experimentally validated using a VNA, confirming full-wave simulation (Ansys HFSS) results. Furthermore, real-time displacement estimation is implemented through an inverse regression model operating directly on frequency measurements, with provided regression matrices enabling immediate deployment in practical sensing applications.