SSPP-SIW Integrated Microwave Bandpass Filtering Sensor for 3-D Printed Material Real-Permittivity Characterization

This work presents a novel microwave sensor device for selec- tive quantification of material permittivity (ϵ_r′) through spoof surface plasmon polariton (SSPP)-substrate integrated waveguide (SIW) integration. The proposed sensor innovatively converts dielectric property variations into measurable microwave signals via a unique transduction mechanism: passband bandwidth modulation directly controlled by ϵ_r′. Specifically, the upper cutoff frequency shift in the SSPP-SIW sensor device serves as the sensing parameter, establishing a direct correspondence (399.3 MHz/unit ϵ_r′) between electrical response and material dielectric properties. Compared to conventional permittivity measurement techniques, this design achieves enhanced sensitivity through SSPP field confinement while maintaining compatibility with standard microwave systems. Experimental validation demonstrates dual-functional operation as both sensor and filter, with particular effectiveness in real-time dielectric characterization of 3D-printed microwave components.