Adopting boundary integral-resonant mode expansion（ BI—RME） method combined with Floquet theorem

design structure of substrate integrated waveguides（ SIW）

and the sensitive region is constructed utilizing electromagnetic band gap structure

and cavity perturbation method is used to analyze. According to the principle of the frequency shift due to the effect of humidity on dielectric constant

the resonator frequency and the signal amplitude of resonator are measured. The test results show that the humidity range of resonator designed by SIW is11 %

97 % RH and the sensitivy characteristics is 13. 37

46. 52 k Hz/RH. The new microwave component has good research significance and measurement result.