High sensitivity differential microwave sensor based on SIW technology for measuring the permittivity and thickness...

Area of Science:

• Electromagnetic sensing
• Microwave engineering
• Materials characterization

Background:

• Non-destructive evaluation of material permittivity and thickness is crucial across various industries.
• Existing methods may lack sensitivity, spatial resolution, or are susceptible to environmental interference.

Purpose of the Study:

• To present a simple, highly efficient method for characterizing permittivity and thickness of solid materials.
• To enhance measurement sensitivity and spatial resolution using a novel sensor configuration.

Main Methods:

• Utilizing symmetrical Split Square Resonators (SSRs) with a central via integrated into a Substrate Integrated Waveguide (SIW) structure.
• Operating based on a combined band-pass and band-stop response with distinct transmission pole (TP) and transmission zero (TZ) frequencies.
• Analyzing the linear relationship between the TZ frequency shift and material under test (MUT) permittivity and thickness.

Main Results:

• The TZ frequency exhibits a linear shift with increasing MUT permittivity and thickness, while TP remains stable.
• Achieved high measurement sensitivities: 3.27% for permittivity and 30.63% for thickness.
• Demonstrated competitive performance compared to existing techniques.

Conclusions:

• The proposed SSR-based sensor provides an accurate and sensitive method for non-destructive material characterization.
• The differential frequency response minimizes environmental interference, enhancing measurement reliability.
• The sensor's design is compatible with standard PCB fabrication, enabling practical implementation.