Design of a 140 GHz Quasi-optical Resonator for Measuring Low-loss Dielectric

The theoretical analysis and design of a quasi-optical resonator operating at 140 GHz is presented in this paper. The initial theorectial calculation shows that this resonator operates in the
$\mathbf{TEM}_{\mathbf{0},\mathbf{0},\boldsymbol{q}}$
mode and has obtained good electrical perforemance, including a quality factor of 128462, a mode interval of 1.4 GHz, and a beam waist radius of 3.17 mm. The designed quasi-optical resonator is suitable for measuring the low-loss dielectric operating in the sub-terahertz band.