JED - August 2013 - 49

E W101

“Hot Brick” Jammers

Target

Effect of Jammer on Tracker
Figure 4 shows some of the reticle
types described in earlier “EW 101” columns along with the IR energy patterns
they output to their sensing cells. The
processor uses the timing or width of
the video pulses from the sensing cell
to determine the direction in which the
missile must be steered to home on the
target aircraft. In some missiles, the
amplitude of the pulses, or the number
of pulses in each burst, determines the
magnitude of the angular offset of the
tracker’s optical axis from the target
direction.
Figure 5 shows the video generated
from the target’s IR energy (after pass-

Signal fromTarget
Signal from Jammer
Figure 5: The processor in the attacking missile receives superimposed video waveforms from the
target’s IR energy and from the jammer energy. The presence of the jammer video prevents the
tracker from determining the relative location of the target aircraft.

The Journal of Electronic Defense | August 2013

The earliest IR jammers had heated
Silicon/Carbide blocks that emitted
Modulated
a high level of IR energy. As shown in
IR
Figure 3, these blocks are mounted in
Energy
Missile
cylindrical housings with lenses over
IR
Hot
their vertical surfaces. Each lens has a
Sensor
s
Mass
mechanical shutter, which is opened and
closed to create an energy waveform like
that which is created by the operation of
the reticle in the missile’s tracker. Thus,
Shutters
the jamming signal is accepted by the
Jamming
missile tracker’s processor as a valid IR
Waveform
target. This type of jammer, sometimes
called a “hot brick” jammer, outputs
Figure 3: An early IR jammer had a heated mass inside a housing with mechanical shutters around
360 degrees. It emitted bursts of IR energy that look like the pulses reaching the tracker’s sensor
jamming signals over a wide angular
through a reticle.
area, so it does not require accurate information about the location of the attacking missile, and can
ing through the reticle) for one type of missile. Also shown is a
jam multiple attacking missiles.
jamming signal. Both IR energy patterns enter the sensing cell,
and their combined energy
patterns cause a complex
video signal pattern to enter into the processor. Note
how this combined pattern prevents the processor
from accurately determining the number of pulses in
Target
a burst, the timing of the
bursts, or the amplitude of
the video pulses. Also note
that the video signals from
the jammer are much larger
than those from the target.
This is from the jamming
to signal ratio (J/S) – in
this case, the ratio of the
received jamming energy
to the received target sigFigure 4: Each type of reticle causes the tracker sensor to see a different modulation waveform on the received IR
nal energy.
energy.

49


http://www.naylornetwork.com/jed-nxt/index.asp

JED - August 2013

Table of Contents for the Digital Edition of JED - August 2013

The View From Here
Conferences Calendar
Courses Calendar
From The President
Letters
The Monitor
Washington Report
World Report
The Spectrum Management Challenge: Creating Order From Chaos
Technology Survey: ELINT Receivers
EW 101
AOC News
Index of Advertisers
JED Quick Look
JED - August 2013 - cover1
JED - August 2013 - cover2
JED - August 2013 - 3
JED - August 2013 - 4
JED - August 2013 - 5
JED - August 2013 - The View From Here
JED - August 2013 - 7
JED - August 2013 - Conferences Calendar
JED - August 2013 - 9
JED - August 2013 - Courses Calendar
JED - August 2013 - 11
JED - August 2013 - From The President
JED - August 2013 - 13
JED - August 2013 - Letters
JED - August 2013 - The Monitor
JED - August 2013 - 16
JED - August 2013 - 17
JED - August 2013 - 18
JED - August 2013 - 19
JED - August 2013 - 20
JED - August 2013 - 21
JED - August 2013 - Washington Report
JED - August 2013 - 23
JED - August 2013 - World Report
JED - August 2013 - 25
JED - August 2013 - 26
JED - August 2013 - 27
JED - August 2013 - The Spectrum Management Challenge: Creating Order From Chaos
JED - August 2013 - 29
JED - August 2013 - 30
JED - August 2013 - 31
JED - August 2013 - 32
JED - August 2013 - 33
JED - August 2013 - 34
JED - August 2013 - 35
JED - August 2013 - 36
JED - August 2013 - Technology Survey: ELINT Receivers
JED - August 2013 - 38
JED - August 2013 - 39
JED - August 2013 - 40
JED - August 2013 - 41
JED - August 2013 - 42
JED - August 2013 - 43
JED - August 2013 - 44
JED - August 2013 - 45
JED - August 2013 - 46
JED - August 2013 - 47
JED - August 2013 - EW 101
JED - August 2013 - 49
JED - August 2013 - 50
JED - August 2013 - AOC News
JED - August 2013 - 52
JED - August 2013 - Index of Advertisers
JED - August 2013 - JED Quick Look
JED - August 2013 - cover3
JED - August 2013 - cover4
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