Microwave is an kind of electromagnetic wave, it is between the radio waves and light waves, with frequency of f = 1 ~ 1000 GHZ, and wave length λ = 0.3 ~ 300 mm. The characteristics of microwave is strong directionality of emission, and is almost not affected by fire, dust, smoke and strong light during process of transmission. After it meets the obstacles, it will be absorbed, emitted and refracted. In the technologies of radar, navigation, communication and television, it is the reflection characteristics of microwave that is used for information transmission, processing and transformation.