What Is a Search Radar?
The main task of general search and alert radar is to find long-range military targets
- Chinese name
- Search radar
- Foreign name
- acquisition radar
- Nature
- radar
- Attributes
- search for
- Alert radar
- The main task is to find long-range military targets
- The main task of general search and alert radar is to find long-range military targets
Introduction to Search Radar
- The main task of general search and alert radar is to find long-range military targets, such as airplanes and ships, with a range of more than 400 kilometers and some up to 600 kilometers. The accuracy and resolution of the target coordinates are not required. high.
Search radar performance
- The mission of the search radar is to find targets as early as possible in the widest airspace. Therefore, search radar must meet two requirements: a long detection range and a large coverage airspace. Due to the long detection range required, search radars generally use lower frequency bands, usually L and S frequency bands, sometimes UHF, and in special cases VHF or even HF frequency bands. In these frequency bands, the atmospheric attenuation is not too large and the clutter reflectivity is low, such as radars that perform early warning tasks. Early warning radars include ground, airborne, and shipborne types. The ground is generally large-scale early warning radars, which are mainly targeted at long-range targets, such as intercontinental strategic ballistic missiles. The operating frequency is mostly below 100 MHz, and the detection range reaches thousands of kilometers. It can reach tens of meters, and the azimuth and elevation angles can reach 0.03 degrees. In order to achieve such accuracy, the antenna size of the ground warning radar is tens of meters. [1]
GPS GPS calibration method for search radar
- GPS measurement data has the characteristics of high measurement accuracy and good real-time performance, but GPS data is not a direct observation of the target from a ground radar station, and cannot be directly used for calibration of search radar. For GPS measurement data, coordinate conversion is required, and it is converted to the center polar coordinate system used by the ground search radar, and then the converted data is used as the measurement true value of the target to calibrate the radar.
In this method, a piloted aircraft is used as the target for calibration of the search radar, and the aircraft is equipped with a GPS positioning device and a GPS data recording device. This method uses universal time (UTC) time as the time series. Before calibrating the ground search radar using GPS as standard equipment, the following tasks should be completed:
a. GPS position measurement is performed on the radar site r 0, and the measurement accuracy is generally less than lm.
b. Level the radar station and measure the angle between the azimuth of the radar station and the north angle.
- c. Develop a detailed flight plan and specify the flight path of the target aircraft to facilitate the search radar to find the target.
- d. The agreed data recording format. The information recorded by the GPS data recording device of the target should include the longitude, latitude, altitude, and UTC time of the target. The information that the radar station terminal should record includes the measured azimuth, elevation, and distance of the target And UTC time information. [2]
Search radar applications
- The most widely used is the two-coordinate search radar, which is a fan beam in the vertical plane, so it does not have resolution at the elevation angle. Its beam on the horizontal plane is very narrow, so the resolution of the azimuth angle is high, reaching a few tenths to a few degrees. Therefore, the position of the target is represented by two measurements of distance and azimuth, and hence the name two-coordinate radar. This radar uses a mechanical scanning method to rotate the antenna or the reflector fed by the horn to scan the fan beam through 360 degrees in azimuth to obtain the azimuth and distance information of the target. Combining the two-coordinate radar with the nodular altimeter radar can obtain the three-dimensional coordinates of the target. However, the two-coordinate radar and the nodular height measurement radar are both mechanical scanning radars. The scanning speed is the highest, the number of targets that can be accommodated simultaneously is small, and the measurement accuracy is poor. Therefore, when air targets appear at high speed and high density, Looks weak. Beginning in the late 1950s, the electronically scanned three-coordinate radar appeared, which can quickly and accurately measure three coordinates of a large number of targets, namely distance, azimuth, and elevation. Phased array radar is a representative of three-coordinate radar. Because it also has the tracking function, we will introduce it later. [1] [3]