What is millimeter wave radar?

Usually, the electromagnetic wave with the wavelength of 1-10 mm is called millimeter wave. It is located in the wavelength range where microwave and far-infrared wave overlap. It has the following four characteristics:
Extremely wide bandwidth: It is generally believed that the frequency range of millimeter wave is 26.5-300 GHz, and the bandwidth is as high as 273.5 GHz. More than 10 times the total bandwidth from DC to microwave. Even considering the atmospheric absorption, only four main windows can be used to propagate in the atmosphere, but the total bandwidth of these four windows can reach 135 GHz, which is five times the sum of the bandwidth of the bands below microwave. This is undoubtedly very attractive in today's frequency resource constraints.
Narrow beams: Millimeter-wave beams are much narrower than microwave beams at the same antenna size. For example, a 12 cm antenna has a beam width of 18 degrees at 9.4 GHz and a wave velocity width of 1.8 degrees at 94 GHz. Therefore, it is possible to distinguish small targets closer to each other or to observe the details of the targets more clearly.
Compared with lasers, millimeter wave propagation is much less affected by climate and can be considered to have all-weather characteristics.
Millimeter-wave components are much smaller than microwave components. Therefore, millimeter-wave systems are easier to miniaturize.
Compared with centimeter-wave radar, millimeter-wave radar has the characteristics of small size, easy integration and high spatial resolution. In the early days, it was used in military field. With the development and progress of radar technology, millimeter wave radar sensors have been applied in many fields, such as automotive electronics, UAV, intelligent transportation and so on. Vehicle-borne millimeter wave radar operates at 244Hz and 77GHz, and a few countries (such as Japan) use 60GHz.