Resonators refer to electronic components that generate resonant frequencies, commonly divided into quartz crystal resonators and ceramic resonators. The function of generating frequency has the characteristics of stability and good anti-interference performance, and is widely used in various electronic products. The frequency accuracy of quartz crystal resonators is higher than that of ceramic resonators, but the cost is also higher than ceramic resonators. Resonators mainly play a role in frequency control, and all electronic products involving frequency transmission and reception require resonators. The types of resonators can be divided into two types according to their appearance: direct insertion and patch type. The most basic resonant device is a dielectric resonator. To understand the working principle of dielectric resonators, one must first understand metal waveguides and resonant cavities. The general characteristics of metal waveguides can be divided into two types: one is the propagation of electromagnetic waves in space or atmosphere, and the other is the propagation of electromagnetic waves along the waveguide system. The initial electromagnetic waveguide wave system used by humans was a dual line transmission line, which was mainly used in low frequency situations. As the frequency gradually increased, the transmission loss and radiation loss of the dual line transmission line increased sharply. In order to overcome radiation loss, a coaxial line structure was adopted. However, the mode used in the coaxial line is still TEM mode, and there must be two internal and external conductors. When the frequency is higher, the loss of the internal conductor becomes very serious. In the microwave frequency band, namely the decimeter and centimeter bands, it has been found that using a hollow metal tube to transmit electromagnetic waves is feasible and convenient. It is impossible to propagate TEM mode in an empty tube, so TE mode or TM mode are used, which is called a metal waveguide or waveguide tube. The cross-sectional area size of metal waveguides in the short millimeter wave band and submicron millimeter wave band is too small and difficult to process, so dielectric waveguides are used as the transmission system. The use of optical fibers and waveguides in the optical band is also a dielectric waveguide. Optical fibers, abbreviated as optical fibers, have become the main means of transmitting electromagnetic signals. In order to approximate the boundary conditions of short road surfaces, high conductivity conductors, such as metal interfaces, can be used to form metal waveguides or wave guides. A metal waveguide can be composed of one waveguide tube or multiple waveguide tubes. When omitting the surface loss of the conductor, the boundary can be considered as a short road surface. The characteristic of waveguide waves is the existence of a cutoff frequency. When the operating frequency is higher than the cutoff frequency, the longitudinal direction is a fast traveling wave, and the transverse direction is a standing wave. When the operating frequency is lower than the cutoff frequency, the longitudinal direction becomes a attenuation field or gradually dissipating field, while the transverse direction remains a standing wave. The propagation characteristics of metal waveguides are ω C=T/（ με) 1/2=cT/（ με) 1/2 or Fc=cT/2 π（ με) Under 1/2 critical state, the wavelength of electromagnetic waves in the medium is the transverse wavelength, i.e λ T=2 π/T=1/fc（ με) The wavelength in vacuum at 1/2 of the corresponding critical state is called the critical wavelength. When the angular frequency of an electromagnetic wave is greater than the critical angular frequency of the wavelength, the electromagnetic wave can propagate in the waveguide, whereas the waveguide is cut off. The critical angular wave number depends on the cross-sectional shape and size of the waveguide