Graphics Programs Reference
In-Depth Information
Example:
0.1
m
2
A certain radar has target RCS
σ
t
=
, pulsewidth
τ
=
0.2µ
s
,
antenna beamwidth
θ
a
==
θ
e
0.02
radians
. Assume the detection range to
8
m
2
m
3
∑
be
R
=
50
Km
, and compute the SCR if
σ
i
=
1.6
×
10
(
⁄
)
.
Solution:
From Eq. (6.42) we have
8σ
t
(
SCR
)
V
=
-----------------------------------------
N
∑
πθ
a
θ
e
c
τ
R
2
σ
i
i
=
1
Substituting the proper values we get
()0.1
(
)
(
SCR
)
V
=
--------------------------------------------------------------------------------------------------------------------------------- -
=
0.265
)
2
)
2
3 0
8
6
10
3
8
π 0.02
(
(
×
) 0.2
(
×
10
) 50
(
×
(
1.6
×
10
)
.
(
SCR
)
V
=
5.76
dB
6.4. Clutter Statistical Models
Since clutter within a resolution cell or volume is composed of a large num-
ber of scatterers with random phases and amplitudes, it is statistically
described by a probability distribution function. The type of distribution
depends on the nature of clutter itself (sea, land, volume), the radar operating
frequency, and the grazing angle.
If sea or land clutter is composed of many small scatterers when the proba-
bility of receiving an echo from one scatterer is statistically independent of the
echo received from another scatterer, then the clutter may be modeled using a
Rayleigh distribution,
x
2
2
x
x
0
x
0
x
------
-------
f
()
=
exp
;
≥
0
(6.43)
where
x
0
is the mean squared value of
x
.
The log-normal distribution best describes land clutter at low grazing angles.
It also fits sea clutter in the plateau region. It is given by
)
2
(
ln
x
ln
x
m
1
σ 2π
x
--------------
--
-----
---------------------------------
f
()
=
exp
;
x
>
0
(6.44)
2σ
2
Search WWH ::
Custom Search