Graphics Programs Reference
In-Depth Information
Radar Cross Section
(RCS)
Chapter 11
In this chapter, the phenomenon of target scattering and methods of RCS
calculation are examined. Target RCS fluctuations due to aspect angle, fre-
quency, and polarization are presented. Radar cross section characteristics of
some simple and complex targets are also introduced.
11.1. RCS Definition
Electromagnetic waves, with any specified polarization, are normally dif-
fracted or scattered in all directions when incident on a target. These scattered
waves are broken down into two parts. The first part is made of waves that
have the same polarization as the receiving antenna. The other portion of the
scattered waves will have a different polarization to which the receiving
antenna does not respond. The two polarizations are orthogonal and are
referred to as the Principal Polarization (PP) and Orthogonal Polarization
(OP), respectively. The intensity of the
backscattered
energy that has the same
polarization as the radarÓs receiving antenna is used to define the target RCS.
When a target is illuminated by RF energy, it acts like an antenna, and will
have near and far fields. Waves reflected and measured in the near field are, in
general, spherical. Alternatively, in the far field the wavefronts are decom-
posed into a linear combination of plane waves.
Assume the power density of a wave incident on a target located at range
away from the radar is
R
P
Di
, as illustrated in
Fig. 11.1
. The amount of reflected
power from the target is
P
r
=
σ
P
Di
(11.1)
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