Graphics Programs Reference
In-Depth Information
In general a jammer can be identified by its effective operating bandwidth
and by its Effective Radiated Power (ERP), which is proportional to the
jammer transmitter power
B J
P J
. More precisely,
P J G J
L J
ERP
=
------------
(10.1)
where is the jammer antenna gain and is the total jammer losses. The
effect of a jammer on a radar is measured by the Signal-to-Jammer ratio (S/J).
G J
L J
10.2.1. Self-Screening Jammers (SSJ)
Self-screening jammers, also known as self-protecting jammers and as main
beam jammers, are a class of ECM systems carried on the vehicle they are pro-
tecting. Escort jammers (carried on vehicles that accompany the attacking
vehicles) can also be treated as SSJs if they appear at the same range as that of
the target(s).
Assume a radar with an antenna gain
G
, wavelength
λ
, aperture
A r
, band-
width
B r
, receiver losses
L
, and peak power
P t
. The single pulse power
received by the radar from a target of RCS
σ
, at range
R
, is
P t G 2 λ 2 στ
4( 3 R 4 L
S
=
-------------------------
(10.2)
is the radar pulsewidth. The power received by the radar from an SSJ jam-
mer at the same range is
τ
P J G J
R 2
A r
B J L J
-------------
-----------
J
=
(10.3)
where are, respectively, the jammerÓs peak power, antenna gain,
operating bandwidth, and losses. Using the relation
P J
,
G J
,
B J
,
L J
λ 2 G
A r
=
----------
(10.4)
then Eq. (10.3) can be written as
λ 2 G
P J G J
R 2
1
B J L J
-------------
----------
-----------
J
=
(10.5)
Note that . This is needed in order to compensate for the fact that the
jammer bandwidth is usually larger than the operating bandwidth of the radar.
Jammers are normally designed to operate against a wide variety of radar sys-
tems with different bandwidths.
B J
>
B r
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