Electromagnetic Modeling of a Millimeter-Wavelength Resonant Cavity

J. C. Weatherall [1], J. Barber [1], B. T. Smith [2], J. Greca [1],
[1] Battelle Memorial Institute, Norwell, MA, USA
[2] U.S. Department of Homeland Security, Science and Technology Directorate, Washington, DC, USA
Published in 2016

The measurement of dielectric constant at frequencies of 20 GHz or greater is important for specifying the optical properties of materials at millimeter wavelength. One method of measurement uses a resonant cavity containing a sample of the material, and relates the resonant frequency and quality factor of the resonance to the complex dielectric constant through electromagnetic simulation. Because the actual measurement requires a detector and coupling elements, the electromagnetic simulation must include the effects of these components. In the engineering literature, the external loading on the cavity is modeled by an equivalent circuit representation. In this paper, the effects of the measurement system are treated by calculating the input impedance directly from the field solutions in the cavity.