A well-known fact that with the help of modern radars can detect the plane at a distance of several hundred kilometers. The question arises: is modern electronics does not allow to create a compact device that allows we are interested to detect objects at least within a few feet. The answer is the number of publications in which such devices are described.
Typical for them is the use of achievements of modern microelectronics microwave, computer processing of the received signal. The use of modern high technology virtually makes it impossible for independent production of these devices. In addition, large dimensions do not allow them widely to apply in the field.
The advantages of radar include fundamentally higher detection range - reflected signal into a coarse approximation can be considered obeying the laws of geometrical optics and its attenuation is not proportional to the sixth and even the third, and only the second power of the distance.
Author: A. I. Shchedrin