2.1 ELECTROMAGNETIC (EM) SCATTERING
Scattering is the physical phenomenon that occurs when an EM wave hits a discontinuity/nonuniformity or an object. The deviation of the wave trajectory or path is generally known as scattering.
The classification of scattering phenomena can be made according to the size of the scattering object (or the scatterer) with respect to the wavelength of the EM wave. Radar signals reflect or scatter in different ways depending on the wavelength of the EM wave and the shape of the object (scatterer). If the wavelength of the EM wave is much smaller than the size of the scatterer, the EM wave bounces back in a similar way to how light reflects from a large surface. This type of scattering is often called scattering in the optical region . If the EM wave’s wavelength is of comparable size of the scatterer, such as within a few wavelengths, some resonances may occur, and the scattering intensity may fluctuate considerably for different frequencies. The scattering direction is mainly affected by the incident wave direction in this region that is usually called Mie region (or resonant region) [2, 3]. This particular scattering type is therefore called Mie scattering. If the wavelength of the EM wave is much longer than the size of the scatterer, the wave is dispersed around the scatterer. This type of reflection is named as Rayleigh scattering [2, 3].
Scattering types can also be classified according to the wave’s trajectory ...