Interdigitated capacitor sensor for complex dielectric constant sensing
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The objective of this thesis is to develop a complex dielectric properties sensor using interdigitated capacitor (IDC) structure. IDCs are easy to fabricate and because of its planar structure, it can be easily integrated with other sensing components and signal processing electronics. The design, fabrication, modeling, and testing of IDC sensors are presented in this thesis. Design parameters and their influence on sensor's output signals are discussed. Previous IDC models are reviewed and the limitations are studied. A new equivalent circuit model based on the fringing electric field distribution and a novel iterative data extraction algorithm combining Finite-Element Method (FEM) and the equivalent circuit model is studied. Results suggest that the algorithm can accurately extract relatively low dielectric constant and conductivity of material under test (MUT) from measured impedance data.