The invention discloses a symmetric quasi-
optical cavity design method for
dielectric constant measurement, which belongs to the technical field of quasi-
optical cavity design and comprises a mirror design method and a
coupling design method. The design method of the mirror is as follows: the quasi-
optical cavity is composed of a transmission-type spherical mirror with a symmetrical structure, and parameters needing to be designed mainly comprise the curvature
radius of the spherical mirror, the aperture
radius of the spherical mirror, the distance between the two spherical mirrors and the material of the spherical mirror; factors considered during design comprise intrinsic
spectral line purity, stability of an
open cavity, an
open cavity Q value and a
girdling radius; the
coupling design method comprises the following step of feeding a
signal into and out of the symmetrical quasi-optical cavity by adopting a
coupling ring mode. According to the design method of the symmetric quasi-optical cavity, the coupling ring is innovatively placed between the two spherical mirrors for
signal feed-in / feed-out, a traditional fixed
small hole coupling mode is replaced, the
coupling strength of the coupling ring is flexibly adjusted through parameters such as the ring
diameter, the wire
diameter and the position, and the problems that after
small hole coupling
machining, adjustment cannot be conducted, and flexibility is poor are solved.