Radar (RAdio Detection And Ranging or RAdio Direction And Ranging) is a system that uses radio waves to detect and determine the velocity, angle or range of objects. It is used to detect aircraft, ships, guided missiles and weather formations. A radar system consists of a transmitter that emits high-frequency electromagnetic waves. The transmitting and receiving antenna are used for transmitting the radar waves and receiving the backscattered information. The receiving antenna and processor determines the characteristics of the objects.
Radar
is categorized into two types:
·
Active radar, and
·
Passive radar.
In active radar, an antenna emits high-frequency radio waves on the objects of
the earth surface and echoes back the backscattered information of the object.
This type of radar is called as mono-static. In Figure
1, the variable T denotes the time delay that is equal to the total time
taken by the signal to be transmitted to the object and reflected back i.e. ttransmitted + techo. Here the location of the
transmitter and receptor is same.
Figure 1 Basic mechanism of an active radar system
In
a passive radar system, the location of
the transmitter and receptor is different. A passive radar system depends on
the signal spread from a dissimilar location. This type of radar system is
called bi-static. In the Figure 2, t1+t2 = t3+t4. This condition is true for every
object that is positioned on the ellipse of Figure 2. For both of the objects in Figure 2, from the receptor point of view,
the time delay between the original signal and the reflected signal is exactly
the same. The performance of the passive radar system is highly dependent on
the number of transmitters and receptors and their geometry.
Figure 2 Basic mechanism of a passive radar system
Note: If you are taking help from the above work and also incorporating the above content in your research work, Kindly make sure you are citing the below papers.
- https://www.sciencedirect.com/science/article/pii/S2215098617314003
- https://www.sciencedirect.com/science/article/pii/S1319157817301106
- https://www.sciencedirect.com/science/article/pii/S1319157817303865
- https://link.springer.com/article/10.1007/s11831-021-09548-z
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