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Chapter 3 / Sensors / Radar
_ _
S
: =
I
S
⋅ σ
4 ⋅ π ⋅
RCS
2
Po,
t
3.8-9
: =
P
T
⋅ G
2
⋅ λ
2
T
⋅ σ
3 4
( 4 ⋅ π ) ⋅ P
o,
t
RCS
Equation 3.8-25
For a circular Gaussian radiation pattern the directive gain is a function of
the antenna beam width and the antenna efficiency (λE),
G : = λ ⋅ π ξ
E
2
2
BW
Equation 3.8-26
The noise power (N) available for a single pulse at the perfect receiving
antenna measured in (W/Hz),
N : = k ⋅ T
B
S
t
P
Equation 3.8-27
(kB) is Boltzmann's constant, and (tP) the uncompressed transmitted pulse
length which is a piecewise constant function of target range, a typical
approximation being,
t
P
: =
0.
0027
⋅ P
XT
o,
t
The system noise temperature (TS) is the sum of,
S
A
R
1 x 10
1 x 10
T = T + T + L ⋅T
R
−4
−6
E
Equation 3.8-28
Equation 3.8-29
(TA) is the antenna noise comprising atmospheric and ground components,
T
A
: =
9 ⋅ TTS
+ T
10 ⋅ L
O
O
TO
+
1 + L
O
Equation 3.8-30
(LO) is the antenna ohmic loss factor, and (TO) the ground temperature. The
sky noise temperature (TTS) is a function of beam elevation with respect to
the Alignment frame.
Θ
TB
A
<
30 ⋅ π
180
⇒
T
TS
: =
9.
3433
+
0.
03715
⋅
Θ
TB
A
Equation 3.8-31