Digital Signal Processing Reference
In-Depth Information
2.4.3
Surface Reflection Characteristics
When the signal travels from a dense space into a less dense one, the value is
more than the incidence angle known as the critical angles while thus entire signal
is reflected with Rs
D
Rp
D
1. This phenomenon is defined as the total internal
reflection (Lakhtakia
1992
). It is well-known that the reflection coefficients for
horizontal and vertical polarization are simply given in the following by considering
"
D
"
r
j
!"
0
in Eqs. (
2.37
) and (
2.38
), respectively (van Nee
1992
):
q
"
.cos /
2
sin
RC
H
D
q
"
.cos /
2
(2.37)
sin
C
q
"
.cos /
2
" sin
RC
V
D
q
"
.cos /
2
(2.38)
" sin
C
where is the grazing angle. According to GNSS receiver antenna property that
can receive RHCP signals, it is necessary to assess these selected surfaces in cross-
polarized and co-polarized cases (Vickerman and Gilmore
2009
). According to
Leroux et al. (
1998
), the co-polarization equation can be written as:
RC
H
C
RC
V
2
O
D
(2.39)
Similarly for cross-polarization:
RC
H
RC
V
2
X
D
(2.40)
where
O
and
X
is reflection coefficient for co-polarization and cross-polarization
and
RC
H
and
RC
V
is reflection coefficient for horizontal and vertical linear
polarization, respectively in Eqs. (
2.37
) and (
2.38
). By using GNSS scatter signals
to selected surfaces, reflection coefficients for GNSS signals versus grazing angles
can be computed.
Therefore, the multipath characterization of GNSS reflected signals are very
complex, depending on GNSS antenna height, satellite elevation angle and ratio of
the reflected wave amplitude relative to the direct wave as well as the polarization
of the targeted surface in different propagation angles.
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