Graphics Programs Reference
In-Depth Information
P
c
2πσ
t
f
2
2σ
t
2
W
()
=
-------------------
exp
(
⁄
)
(7.33)
where is the clutter power (constant), and is the clutter rms frequency
(which describes the clutter spectrum spread in the frequency domain). It is
given by
P
c
σ
t
σ
2
σ
2
σ
2
σ
t
=
++
(7.34)
is the standard deviation for the clutter spectrum spread due to wind veloc-
ity; is the standard deviation for the clutter spectrum spread due to antenna
scanning; and is the standard deviation for the clutter spectrum spread due
to the radar platform motion (if applicable). It can be shown that
1
σ
v
σ
s
σ
v
2σ
w
λ
σ
v
=
----------
(7.35)
2π
Θ
a
T
scan
σ
s
=
0.265
-------------------
(7.36)
v
---
σ
s
≈
sin
θ
(7.37)
where
λ
is the wavelength and
σ
w
is the wind rms velocity;
Θ
a
is the antenna
3-db azimuth beamwidth (in radians);
T
scan
is the antenna scan time;
v
is the
platform velocity; and
θ
is the azimuth angle (in radians) relative to the direc-
tion of motion.
The clutter power at the input of an MTI filter is
∞
∫
f
2
2σ
t
2
P
c
2πσ
t
C
i
=
-------------------
exp
---------
d
(7.38)
∞
Factoring out the constant
P
c
yields
∞
∫
f
2
2σ
t
2
1
2πσ
t
C
i
=
P
c
----------
-
-----
exp
---------
d
(7.39)
∞
It follows that
1. Berkowtiz, R. S.,
Modern Radar, Analysis, Evaluation, and System Deign
, John
Wiley & Sons, New York, 1965.
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