Graphics Programs Reference
In-Depth Information
Again if the jamming is employed in the form of Gaussian noise, then the
radar receiver has to deal with the jamming signal the same way it deals with
noise power in the radar. In this case, the S/(J+N) is
P
t
G
σ
A
r
τ
4(
2
R
4
L
-----------------------
S
JN
-------------
=
-------------------------------------------------
(10.16)
+
(
ERP
)
A
r
G
'
4π
R
2
B
J
----------------------------
+
kT
0
10.3. Range Reduction Factor
Consider a radar system whose detection range
R
in the absence of jamming
is governed by
P
t
G
2
λ
2
σ
4(
3
kT
e
B
r
FLR
4
(
SNR
)
o
=
------------------------------------------
(10.17)
The term Range Reduction Factor (RRF) refers to the reduction in the radar
detection range due to jamming. More precisely, in the presence of jamming
the effective radar detection range is
R
dj
=
R
×
RRF
(10.18)
In order to compute RRF, consider a radar characterized by Eq. (10.17), and
a barrage jammer whose output power spectral density is (i.e., Gaussian-
like). Then the amount of jammer power in the radar receiver is
J
o
J
=
J
B
r
(10.19)
where is the jammer effective temperature. It follows that the total jammer
plus noise power in the radar receiver is given by
T
J
N
i
+
J
=
kT
e
B
r
+
kT
J
B
r
(10.20)
In this case, the radar detection range is now limited by the receiver signal-to-
noise plus interference ratio rather than SNR. More precisely,
P
t
G
2
λ
2
σ
4(
3
kT
e
S
JN
-------------
=
-----------------------------------------------------------
(10.21)
+
)
B
r
FLR
4
(
+
T
J
The amount of reduction in the signal-to-noise plus interference ratio because
of the jammer effect can be computed from the difference between Eqs.
(10.17) and (10.21). It is expressed (in dB) by
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