The electromagnetic wave of radar has a certain penetration ability, has the characteristics of all-weather and all-day, and has large transmission power, long detection distance, high measurement accuracy, and can automatically search and track targets, which makes it widely used in many fields.
1) Classification by application field
According to the use, radar can be divided into two categories: military and civilian.
Early developments in radar came primarily from military needs. With the improvement of radar performance and the development of radar basic science, especially the rapid progress of high-power transmitting devices, computers and high-speed signal processing technology, the application range of radar in the national economy has also been expanding, and various high-performance civilian radars have achieved rapid development.
(1) Military radar
Military radar is the most important means of obtaining all-weather and full-range tactical intelligence in land, sea, air and space battlefields, and is a necessary means to achieve long-range strikes and precision strikes, and has an extremely important strategic position in the field of national defense and military affairs, and is widely used in the fields of vigilance, guidance, weapon control, reconnaissance and navigation support.
(2) Civil radar
With the continuous improvement of radar technology, the application scope of radar in the civilian field continues to expand, covering many fields such as natural disaster prevention, aircraft navigation, meteorological support and meteorological research, and plays an important role in meteorology, water conservancy, air traffic control and other fields, and the application direction is constantly becoming segmented and accurate.
2) Classification by antenna scanning method
According to the antenna scanning method, radar products can be divided into mechanical scanning radar and phased array radar.
A schematic comparison of mechanical radar and phased array radar is as follows:
At the beginning of the 21st century, the mainland radar industry is mainly based on mechanical scanning radar, mechanical scanning radar concentrates a position to transmit signal waves, through the mechanical turntable rotation, so that the signal waves are transmitted to different directions, detect different targets, but its mechanical rotation efficiency is low, the detection area and detection targets are limited, and it is no longer adapted to the increasingly complex direction of electromagnetic field development.
In recent years, phased array technology has gradually expanded in the field of radar, and mechanical scanning radar through the rotation of the antenna to rotate the radar beam, phased array radar uses "electronic phase shifter" to achieve scanning, so phased array radar response speed, update rate, multi-target tracking ability, resolution have been greatly improved, has become the main direction of the current development of the radar industry.
Although phased array radar has excellent performance, its technical implementation is complex and costly, so it has been mainly used for military purposes for a long time, and its high price is the main obstacle limiting its large-scale application in the civilian field.
3) Classification by band
According to the band, it can be mainly divided into S/C/X and other bands radar (or divided into over-the-horizon, microwave, millimeter wave, lidar). The longer the band, the greater the search range of the radar, but the accuracy is also relatively low.
The corresponding frequencies and application areas of each band are shown in the following table:
The "Special Plan for the Development of Meteorological Radar (2017-2020)" issued by the China Meteorological Administration pointed out that the mainland has basically completed a new generation of weather radar network in China, and by the end of 2016, the construction of 233 new generation weather radars has been completed, of which they basically belong to S- and C-band weather radars.
In the early stage of polarization radar meteorological application research, scientists mainly focused on S, C band dual-polarization radar with long wavelength, with the deepening of research, the advantages of X-band dual-polarization radar gradually emerged, especially in the past ten years on the X-band polarization radar meteorological application research is also increasing. Compared with polarization radar with longer wavelength, X-band dual-polarization radar not only has lower cost, small antenna size, easy to control and move, but also has high spatiotemporal resolution, finer phase recognition of water condensate particles in the cloud, and can provide more detailed microphysical and dynamic structure information in the cloud, providing more detailed observation data for the study of the occurrence and development mechanism of cloud and precipitation.
Compared with the new generation of weather radar network observation in the S-band and C-band, the X-band dual-polarization weather radar plays the role of filling the blind zone and refined detection, which has the following characteristics:
(1) The wavelength is short, the detection ability of small particles is good, and the development of early convective clouds can be monitored;
(2) Small size, easy installation, can solve the early warning problem that some S- and C-band radars cannot observe areas due to ground object obstruction and earth curvature factors.
Since the size of the radar antenna is proportional to the wavelength under the same beam width, the diameter of the S and C band antennas is often as high as 5~8 meters, while the size of the X-band weather radar antenna is relatively small, and the site construction and radar erection are more convenient. For X-band phased array weather radar, its fast scanning characteristics are more conducive to the detection and early warning of small-scale, rapid changes in life and consumption, catastrophic and catastrophic strong convective weather, and its beam conversion is more flexible, which improves the scanning speed, and at the same time, it can also obtain scanning data with more intensive spatial resolution in unit time. At present, X-band radar can make up for the detection blind zone of S-band and C-band weather radar near the ground.
In summary, according to different classification standards, radar classification is rich and complex. Target diversification, environmental complexity and mission diversification determine the diversity of radar types, and also promote the continuous development and evolution of radar system, frequency band, theory and technology.