Radar Cross Section (RCS) - MATLAB Simulations for Radar Systems Design - page 496

R R

scattering object

radar

Radar Radar

R Figure 11.1. Scattering object located at range .

denotes the target cross section. Define as the power density of the
scattered waves at the receiving antenna. It follows that

σ P Dr

4π R 2

P Dr = P r ⁄ ( )

(11.2)

Equating Eqs. (11.1) and (11.2) yields

4π R 2 P Dr
P Di

 

σ = --------

(11.3)

 

and in order to ensure that the radar receiving antenna is in the far field (i.e.,
scattered waves received by the antenna are planar), Eq. (11.3) is modified

P Dr
P Di

 

4π R 2 σ = lim -------- (11.4)

 

R → ∞

The RCS defined by Eq. (11.4) is often referred to as either the monostatic
RCS, the backscattered RCS, or simply target RCS.

The backscattered RCS is measured from all waves scattered in the direction
of the radar and has the same polarization as the receiving antenna. It repre-
sents a portion of the total scattered target RCS , where . Assuming a
spherical coordinate system defined by ( ), then at range the target
scattered cross section is a function of ( ). Let the angles ( ) define the
direction of propagation of the incident waves. Also, let the angles ( )
define the direction of propagation of the scattered waves. The special case,

σ t σ t > σ

ρθϕ ,, ρ

θϕ , θ i ϕ i ,

θ s ϕ s ,