Sensing Depth Analysis of Different Permittivity Materials Based on Open-Ended Coaxial Probes at Different Input Powers

Existing studies have only qualitatively analyzed the relationship between input power and depth of induction of open-ended coaxial probe. Along with the development of science and technology, the measurement of permittivity requires the quantification of the relationship between the input power and the sensing depth of an open-ended coaxial probe. In this article, for the first time, the effect of different power and materials with different permittivity on the sensing depth of the probe is quantitatively analyzed and the maximum sensing depth of 2.2-mm aperture probe is derived. More importantly, to better handle small amounts of sample materials, thin and multilayer materials, and ensure measurement accuracy, we have also established a sensing depth calculation model. The calculation formula of the model can be used to quickly and accurately calculate the sensing depth of the probe for different permittivity materials under different input powers. This is the industry’s first computational model for the sensing depth of open-end coaxial probes, which provides a strong guarantee of the method’s accurate measurement. Finally, this article validates the model formulation for sensing depth calculation by experimental means. Results show that in the range of −20 to 20 dBm (5.8-GHz frequency) for materials with permittivity between 1 and 80, the computational model is accurately valid and that the maximum depth of sensing for a 2.2-mm aperture probe is 2.8 mm.