Phase-Variation Microwave Resonator for Highly Sensitive Dynamic Sensing

High-precision dynamic sensing is critical in fields, such as industrial automation, structural health monitoring, and environmental sensing, where real-time responses to minuscule changes can prevent system failures or optimize performance. In this work, we introduce and demonstrate a phase-variation coaxial cable resonator (CCR) as a highly sensitive sensor for dynamic sensing applications. As a proof of concept, a prototype device based on a custom-designed CCR is thoroughly investigated for dynamic displacement measurements, as displacement is a fundamental quantity essential to numerous applications. The sensor consists of two components: a static CCR device and a movable conducting plate. As the conducting plate is positioned closer to the open end of the CCR, the phase of the reflection coefficient varies due to changes in the fringing electric field, which is dependent on the distance between the plate and the CCR’s open end. Crucially, compared to conventional open-ended probes, the phase sensitivity of the CCR is significantly enhanced and can be finely tuned, owing to the resonant structure integrated into the coaxial line. Theoretical analysis and numerical simulations predict amplified phase sensitivity when the sensor operates at its resonance frequency. The amplification factor, determined by the resonance depth, indicates that deeper resonances yield higher phase sensitivity. A prototype sensor is fabricated and tested for static displacement detection based on phase measurements, confirming the theoretical predictions. Additionally, dynamic displacement measurements further demonstrate the CCR’s capacity for ultrasensitive dynamic sensing. The sensor’s potential application is extended to monitor variations in the dielectric constant of analytes, enabling high-precision analysis in chemical and environmental monitoring. The successful development of dynamic sensing with the CCR opens pathways to create various physical and chemical sensors, enhancing applications in fields requiring precise, real-time measurements.