Study of a 60 GHz Quasi-Optical Resonator for the Measurement of Low-Loss Dielectrics’ Complex Permittivity

This paper presents the simulation, design, machining, and measurement of a millimeter wave quasi-optical resonator. The quasi-optical resonator is machined directly from the copper rather than the commonly used body material of K9 glass, which greatly reduces the cost and difficulty of machining. Measurement results indicate that the quasi-optical resonator operates in the Gaussian mode <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{TEM}_{00_{q}}$</tex>, demonstrating good electrical performance with a high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex>-factor exceeding 33000 over the frequency range of ~53.2-64.5 GHz. The designed millimeter wave quasi-optical resonator is well-suited for measuring the complex permittivity of low-loss dielectrics due to its significant advantage of high Q-factor.