JED - November 2017 - 68

E W101

Range at which
there is no longer
adequate J/S

RADAR

Jam

mer

Rcvd Pwr

The Journal of Electronic Defense | November 2017

68

strike groups against multiple
radars. The radar will have its
antenna main beam boresight
Radar Skin-return Signal
aimed at the target, so the
jammer (which is somewhere
else) will be broadcasting into
RADAR
Jamme
the side lobes of the radar's
r Signal
antenna.
Since the jammer must
J
Lethal
broadcast into the side lobes
Range
of the radar, it is a safe aso
f Weapon
sumption that it will not dependably produce adequate
J/S to break a radar's lock on
its target. Therefore, stand-off
Figure 3: Stand-off jamming is performed from beyond the lethal range of the weapon associated with the
jammed radar, and the jamming is received in the side lobes of the radar's antenna.
jamming is usually assumed to
be targeted against acquisition radars or acquisition modes.
Note that from
the J/S
produced
in stand-off
increases
Figure 3: Stand-off jamming is performed
beyond
the lethal
range ofjamming
the weapon
the jammed
is received
the side
of to the
The formula for the jamming to associated
signal ratiowith
achieved
in radar,
with and
the the
ERPjamming
of the jammer
and in
range
fromlobes
the radar
the radar's antenna.
stand-off jamming is:
target. It decreases with the radar ERP, the range to the jammer from the radar target RCS, and amount that the side lobe
J/S = ERPJ - ERPS + 71 + GS - GM - 20 log R J + 40 log RT
gain is down from the main lobe boresight gain of the radar
- 10 log RCS
antenna.
Where: J/S is the jamming to signal noise in dB
ERPJ is the effective radiated power of the jammer
STAND-OFF BURN-THROUGH
in dBm
Since the range from the stand-off jammer to the radar
ERPS is the effective radiated power of the jammed
is assumed to remain constant through the engagement, the
burn-through range is only a function of the range from the
radar in dBm
radar to the target. The formula for the range to the target
GS is the side lobe gain of the radar antenna
term (at burn-through) is:
GM is the main lobe bore-sight gain of the radar
antenna
40 log R BT = ERPS - ERPJ - 71 - GS + GM + 20 log R J + 10 log
R J is the range from the radar to the jammer in km
RCS + J/S Req
RT is the range from the radar to the target in km
RCS is the radar cross section of the target in m2
Where: R BT is the range from the radar to the target at burnthrough in km
J/S Req is the J/S value at
which the jammer can no
longer effectively jam the
radar.
Radar Signal [Reduces by 4] d

Jammer
Skin Return

Ran

ge C

ons

Target
Approaching
Radar

tant

The formula for the burn
through range solves the range
term for the actual range:
R BT = |Anti-log {[40 log R BT[
/ 40}

WHAT'S NEXT

J

Range

Figure 4: Burn through for stand-off jamming occurs when the target is close enough to the jammed radar
that the radar can reacquire the target in the presence of the stand-off jamming. The jammer is treated as
for stand-off
jamming occurs when the target is close
though Figure
it does 4:
notBurn
movethrough
during the
engagement.
enough to the jammed radar that the radar can reacquire the target in the presence
of the stand-off jamming. The jammer is treated as though it does not move during
the engagement.

Next month, we will continue our discussion of legacy EW
threats and countermeasures.
For your comments and suggestions, Dave Adamy can be
reached at www.lynxpub.com. a


http://www.lynxpub.com

JED - November 2017

Table of Contents for the Digital Edition of JED - November 2017

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Forecast: Future of DIRCM
Sensor Fusion for 4th Gen Fighters
Technology Survey: ELINT Receivers
54th Annual AOC International Symposium and Convention Guide
EW 101
AOC News
Index of Advertisers
JED Quick Look
JED - November 2017 - intro
JED - November 2017 - cover1
JED - November 2017 - cover2
JED - November 2017 - 3
JED - November 2017 - 4
JED - November 2017 - 5
JED - November 2017 - The View From Here
JED - November 2017 - 7
JED - November 2017 - Conferences Calendar
JED - November 2017 - 9
JED - November 2017 - Courses Calendar
JED - November 2017 - 11
JED - November 2017 - From the President
JED - November 2017 - 13
JED - November 2017 - 14
JED - November 2017 - insert1
JED - November 2017 - insert2
JED - November 2017 - The Monitor
JED - November 2017 - 16
JED - November 2017 - 17
JED - November 2017 - 18
JED - November 2017 - 19
JED - November 2017 - 20
JED - November 2017 - 21
JED - November 2017 - 22
JED - November 2017 - 23
JED - November 2017 - World Report
JED - November 2017 - 25
JED - November 2017 - Forecast: Future of DIRCM
JED - November 2017 - 27
JED - November 2017 - 28
JED - November 2017 - 29
JED - November 2017 - 30
JED - November 2017 - 31
JED - November 2017 - 32
JED - November 2017 - 33
JED - November 2017 - 34
JED - November 2017 - Sensor Fusion for 4th Gen Fighters
JED - November 2017 - 36
JED - November 2017 - 37
JED - November 2017 - 38
JED - November 2017 - Technology Survey: ELINT Receivers
JED - November 2017 - 40
JED - November 2017 - 41
JED - November 2017 - 42
JED - November 2017 - 43
JED - November 2017 - 44
JED - November 2017 - 45
JED - November 2017 - 46
JED - November 2017 - 47
JED - November 2017 - 48
JED - November 2017 - 54th Annual AOC International Symposium and Convention Guide
JED - November 2017 - 50
JED - November 2017 - 51
JED - November 2017 - 52
JED - November 2017 - 53
JED - November 2017 - 54
JED - November 2017 - 55
JED - November 2017 - 56
JED - November 2017 - 57
JED - November 2017 - 58
JED - November 2017 - 59
JED - November 2017 - 60
JED - November 2017 - 61
JED - November 2017 - 62
JED - November 2017 - 63
JED - November 2017 - 64
JED - November 2017 - 65
JED - November 2017 - EW 101
JED - November 2017 - 67
JED - November 2017 - 68
JED - November 2017 - AOC News
JED - November 2017 - 70
JED - November 2017 - 71
JED - November 2017 - 72
JED - November 2017 - Index of Advertisers
JED - November 2017 - JED Quick Look
JED - November 2017 - cover3
JED - November 2017 - cover4
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