Abstract: Permittivity is an important basic physical parameter that describes the propagation characteristics of electromagnetic fields and electromagnetic waves in dielectric media. It is also a core parameter when studying the interaction between materials and electromagnetic waves. Electromagnetic fields and electromagnetic waves can penetrate the medium to achieve non-contact interaction with the dielectric target sensing object. Moreover, when its wavelength is compared with the physical size of the small dielectric disturbance in its near field area, high sensitivity detection of the dielectric properties of the near-field sensor can be realized. The influence of small external dielectric disturbance on the microwave electromagnetic system is manifested as the frequency shift and Q value change of the system in the macroscopic view, and the change in the electromagnetic energy of the system in the microscopic view. Therefore, microwave technology is used to generate induced electromagnetic fields in passive resonators, and the above-mentioned macroscopic characteristic parameters are used to achieve non-contact, high-sensitivity detection and real-time measurement of small dielectric disturbances in the near field area.
However, the limited Q value of traditional passive resonators makes it difficult to use in practical applications; in addition, the micro-change detection system is vulnerable to environmental temperature and humidity. Moreover, if it causes changes in macroscopic characteristic parameters higher than the changes from its own dielectric disturbance effect, the detection system will generate an error response. Therefore, the circuit compensation technology proposed is used to design an active resonator to enhance the Q value of the resonator, and the differential sensing structure is used to eliminate the impact of environmental parameters on the detect system to adapt to the actual application demand, such as high-sensitivity detection of trace dielectric objects or physical micro-change systems.