Radar Cross Section (RCS) - MATLAB Simulations for Radar Systems Design - page 514

The backscattered RCS for a perfectly conducting sphere is constant in the
optical region. For this reason, radar designers typically use spheres of known
cross sections to experimentally calibrate radar systems. For this purpose,
spheres are flown attached to balloons. In order to obtain Doppler shift,
spheres of known RCS are dropped out of an airplane and towed behind the
airplane whose velocity is known to the radar.

11.5.2. Ellipsoid

An ellipsoid centered at (0,0,0) is shown in Fig. 11.17 . It is defined by the
following equation:

 2  2  2

x
-- 

y
-- 

z
- 

+ + = 1

(11.31)

One widely accepted approximation for the ellipsoid backscattered RCS is
given by

π a 2 b 2 c 2

σ = -----------------------------------------------------------------------------------------------------------------------------------

(11.32)

) 2

a 2 ) 2 ) 2 b 2 ) 2 ) 2 c 2 ) 2

( ( sin θ ( cos ϕ + ( sin θ ( sin ϕ + ( cos θ

When ab = , the ellipsoid becomes roll symmetric. Thus, the RCS is inde-

pendent of ϕ , and Eq. (11.32) is reduced to

Direction to
receiving radar Z

θ

c

b

Y

a

X

ϕ

Figure 11.17. Ellipsoid.