Highly Sensitive Microwave Pressure Sensor Based on Coupled Transmission Lines Integrating Cantilever Structure

This article proposes a novel microwave pressure sensor based on a coupled transmission line integrating a cantilever (CTLIC). The proposed CTLIC structure is implemented by embedding a serpentine-spring modified cantilever into the central microstrip line of a three-line coupled microstrip configuration. Under applied pressure, mechanical deformation of the central transmission line within the CTLIC induces an asymmetric disturbance in the electromagnetic coupling coefficient between adjacent resonators. This asymmetric coupling modulates the response characteristics, specifically causing relative shifts in the resonance frequencies (ƒ_TP1, ƒ_TP3) and an amplitude variation at ƒ_TP2. Consequently, two distinct sensing parameters are generated: the frequency change (∆ƒ_TP = ƒ_TP3 −ƒ_TP1) and the amplitude change (|S₁₁|). Both parameters exhibit relatively good linearity and high sensitivity. To validate the sensing mechanism experimentally, a prototype was simulated, fabricated (on a rigid PCB substrate RO4003C), and measured. Measured results demonstrate that the sensor achieves precise pressure measurement across a 0–10 kPa range, exhibiting an average sensitivity of 104 MHz/kPa (∆ƒ_TP) and 1.34 dB/kPa (|S₁₁| at ƒ_TP2). © 2026 IEEE.