40
3 Radar Targets and Its Reflecting Properties
which gives a good compliance with an experiment at ρ > 2λ and θ 0 < 90
◦ condition.
At sliding angles (θ 0 , 90
◦ ), the following formula gives good results:
A =
4ρ
k
cos
2
(2kρ − 3π/4),
(3.47)
that leads to that in area of sliding angles, the RCS dependency from kρ has an
oscillating character.
In area of small radii of disk RCS when ρ is considerably less than wavelength,
RCS can be calculated as follows:
• for horizontal polarization:
A =
4π
λ 2
πρ
2
2
8kρ
3π
cos
4
θ 0
2
,
(3.48)
• for vertical polarization:
A =
4π
λ 2
πρ
2
2
4kρ
3π
2 + sin
2
θ 0
2
.
(3.49)
At normal incidence, the following formula is correct:
A =
1024
9
π
3
ρ
6
λ 4 .
(3.50)
Figure 3.18 shows a dependence of A/
4πλ
−2
πρ
2
2
relation from 2ρ/λ.
Maximum relative value of RCS, equals to 3.8
4π
λ 2
πρ
2
2 , is achieved at 2ρ ∼ =
0.48λ that is very close to ρ = λ/4 condition.
Triangular plate RCS Let us examine a finite thin identically conducted plate
having a shape of right isosceles triangle with base of 2a and b height at intrinsic
admission a, b λ and find its RCS in direction defined by (γ 0 , θ 0 ) angles.
Fig. 3.18 Energy scattering
function of fine wire