Based on the humidity sensing mechanism of graphene nanomaterials and the principle of LC wireless coupling

a wireless passive humidity sensor is designed and fabricated. The sensor is made from a low temperature co-fired ceramic（ LTCC） process

including a planar spiral inductor and a sensitive element composed of graphene and interdigital electrodes. When the graphene film adsorbs water molecules

its dielectric constant changes

resulting in the change of the resonant frequency of the sensor and acquired by the reading antenna. The experimental results show that the resonant frequency of the sensor changes linearly with the change of relative humidity

while the relative humidity changes from 50 % RH to 90 % RH

the sensitivity of sensing humidity reaches 0. 16 MHz/% RH

and the esponsibility is very good.