Electromagnetic characterization of dielectric pills in the microwave frequency range by resonance methods.

Piotr Czekała

supervisor: Bartłomiej Salski

In the proposed research we aim at constructing new measurement equipment dedicated to characterization of dielectric samples, which in microwave band have shape of small cylindrical discs (pills). Knowledge of the electromagnetic properties of these materials is of importance for industry and academia working on 5G/IoT technologies. The measurement set-up for characterization of these materials will be based on Fabry-Perot open resonator (FPOR), which offers high quality factor, easy access to the cavity and due to high spectral density of resonant states allows measurements at many frequencies in range 20-100 GHz. Measured resonance frequency shift caused be placing sample with unknown permittivity (ε) inside the FPOR is susequently compared with data based calculated using a mathematical model of FPOR and as a result of that comparation ε can be determined.

Proposed model divides resonator into three non-resonant sections (as shown in Figure 1) and describe each section by it’s scattering matrix. Scattering matrix of mirrors are calculated based on near-field scattering equations, while in order to calculated scattering matrix of sample’s section axial mode matching method has been used. Resonance frequencies of the structure may be found be searching for zeros of the characteristic equation:
`det⁡(|I -SM*SR|)=0`
where I - unit matrix, SM - scattering matrix of left mirror and SR - scattering matrix of right mirror and sample. SM and SR are calculated at left sample’s boundary.