Digital Signal Processing Reference
In-Depth Information
Fig. 8.7
Sketch of specular (panels
a
and
b
) and diffuse (panels
c
and
d
) scattering concepts,
as pictured by the geometrical optics approach (panels
a
and
c
) and wave-optics or by Huygens-
Fresnel principles (panels
b
and
d
)
The diffuse scattering can also be pictured as a Geometric Optics phenomena,
or more accurately under wave-optics models. The former approach requires the
concept of surface
facets
, surface patches of size and curvature of the order of or
higher than a few electromagnetic wavelengths. Because of the roughness, different
facets are oriented towards different directions. Incident rays reflect off the facets,
each facet producing a mirror-like reflection, which forwards the reflected rays
towards a direction determined by the facet's normal vector and the incident ray
direction. In bi-static geometric conditions, the receiver only collects those rays
reflected off facets with the appropriate tilt (panel c in Fig.
8.7
). An appropriate
tilt will occur at the surface coordinates x, y when the facet at x, y has its normal
vector pointing towards the bisector of the angle formed by the incident ray at x,
y and the vector connecting the surface point x, y and the receiver. The
glistening
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