Scribd
Upload
38 views2 pages

Thf. Radar Equation 3yf: O 0 4 0 8 1.2 1.6 2.0 2.4 Diometef in Wavelengths

1) The nose-on radar cross section of a cone-sphere is small and decreases with the square of the wavelength. It remains small over a large angular region. 2) At frequencies above the Rayleigh region, the maximum nose-on cross section of a cone-sphere is approximately 0.4λ2 and the minimum is 0.01λ2, relatively insensitive to the cone half-angle. 3) Shaping objects like cone-spheres and using materials like carbon fiber composites can significantly reduce radar cross sections compared to spheres or corner reflectors of the same physical size.

Uploaded by

Suguna
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
38 views2 pages

Thf. Radar Equation 3yf: O 0 4 0 8 1.2 1.6 2.0 2.4 Diometef in Wavelengths

1) The nose-on radar cross section of a cone-sphere is small and decreases with the square of the wavelength. It remains small over a large angular region. 2) At frequencies above the Rayleigh region, the maximum nose-on cross section of a cone-sphere is approximately 0.4λ2 and the minimum is 0.01λ2, relatively insensitive to the cone half-angle. 3) Shaping objects like cone-spheres and using materials like carbon fiber composites can significantly reduce radar cross sections compared to spheres or corner reflectors of the same physical size.

Uploaded by

Suguna
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 2

THF.

RADAR EQUATION 3yf

wave" which travels around the base of the sphere. The nose-on radar cross section is small and
decreases as the square of the wavelength. The cross section is small over a relatively large
angular region. A large specular return is obtained when the cone-sphere is viewed at near
perpendicular incidence to the cone surface, i.e., when 0 = 90 — a, where a = cone half angle.
From the rear half of the cone-sphere, the radar cross section is approximately that of the
sphere.
The nose-on cross section of the cone-sphere varies, but its maximum value is approxi-
mately 0.4A2 and its minimum is 0.0IA2 for a wide range of half-angles for frequencies above the
Raylcigh region. The null spacing is also relatively insensitive to the cone half-angle. If a
"typical" value of cross section is taken as 0.1A 2, the cross section at S band (X = 0.1 m) is 10
' m2, and at X band (X = 3 cm), the cross section is approximately 10" 4 m2. Thus, in theory,
the cone-sphere can have very low backscatter energy. Suppose, for example, that the projected
area of the cone-sphere were 1 m2. The radar cross section of a sphere, with the same projected
area, at S band is about 30 dB greater. A corner reflector at S band, also of the same projected
area, has a radar cross section about 60 dB greater than the cone-sphere. Thus, objects with
the same physical projected area can have considerably different radar cross sections.
In order to realize in practice the very low theoretical values of the radar cross section for a
cone-sphere, the tip of the cone must be sharp and not rounded, the surface must be smooth
(roughness small compared to a wavelength), the join between the cone and the sphere must
have a continuous first derivative, and there must be no holes, windows, or protuberances on the
surface. A comparison of the nose-on cross section of several cone-shaped objects is given in
Fig. 2.13.
Shaping of the target, as with the cone-sphere, is a good method for reducing the radar
cross section. Materials such as carbon-fiber composites, which are sometimes used in aero-
space applications, can further reduce the radar cross section of targets as compared with that
produced by highly reflecting metallic materials. 62

Figure 2.13 Radar cross section of


a set of 40° cones, double-backed
cones, cone-spheres,
double-rounded cones, and circular
ogives as a function of diameter in
O 04 08 1.2 1.6 2.0 2.4 wavelengths. (From Blore, 11
Diometef in wavelengths IEEE Trans.)
Figure 2.12 Measured radar cross section (a/X1 given in dB) of a large cone-sphere with 12.5° half angle
and radius of base = WAX. (a) horizontal (perpendicular) polarization, (b) vertical (parallel) polarization.
(From Pannell et af.61)

You might also like