The microwave emitted by the transmitting antenna will be absorbed or reflected when it meets the measured object, thus changing the power. If the microwave passing through or reflected by the measured object is received by the receiving antenna and converted into an electrical signal, and then processed by the measuring circuit, microwave detection is realized.

Microwave sensor is mainly composed of microwave generator and microwave antenna. A microwave generator is a device for generating microwaves. The microwave generator consists of klystron, magnetron or some solid components. The oscillation signal generated by microwave generator needs to be transmitted through waveguide and emitted by antenna. In order to make the emitted microwave have consistent directivity, the antenna should have special structure and shape.