JED - August 2014 - 46

EW 101

Saturation Decoys

Radar Decoys - Part 2
By Dave Adamy

S

SATURATION DECOYS
In order to be useful, saturation decoys create credible false
targets. Consider how a radar can differentiate a real target
from a decoy. First, there is the size and shape of the target
platform. A decoy is typically much smaller than the aircraft
or ship it simulates, therefore its RCS must be enhanced. This
can be done mechanically by the addition of corner reflectors
or some other highly reflective shape features. However, it is
normally most practical to enhance the radar cross section
electronically by providing gain to increase the signal propagated back to the illuminating radar. The RCS perceived by the
hostile radar is given by the formula (in algebraic form):
s = λ2 G / 4π
Where: s is the RCS produced by the decoy in square meters
λ is the wavelength of the radar signal in square
meters
G is the combined gain ratios of the decoy's receiving
and transmitting antennas and its internal electronics as shown in Figure 1.
The following is the same formula, but in dB form
s = 38.6 - 20 log10(F) + G
Where: s is the RCS in dBsm

Frequency Cells

Range Cells

The Journal of Electronic Defense | August 2014

46

aturation
decoys
protect
TOTAL "GAIN" OF DECOY
friendly assets by providing
false targets to hostile weapons. These decoys can be airborne, sea- or ground-based. In
SIMULATED
each case, the decoy must be
SIGNAL
SKIN
perceived by the enemy weapon system's
FROM
RETURN
RADAR
sensors as a credible target. If the hostile
Receiver &
sensors are not sophisticated, the decoy
Transmitter
may only have to create a radar cross secOr Amplifier
tion (RCS) of the same order of magnitude
as that of the protected asset. However,
Figure 1: The sum of receiving antenna gain, transmitting antenna gain and processing gain of
many modern weapon sensors have become
an active decoy determines the radar cross section (RCS) it will simulate.
more sophisticated, and it appears that
the level of sophistication will continue to increase for the
F is the radar frequency in MHz
Figure 1: The sum of receiving antenna gain, transmitting antenna gain and
foreseeable future.
G decoy combined gains cross section (RCS) it
processing gain of an active is thedetermines the radar in the decoy in dBwill
simulate.
In this series of articles, we will not limit our discussion to
For Example: If the radar signal is at 8 GHz, the decoy's
existing systems, but will consider all of the weapon and decoy
receiving and transmitting antennas each have 0 dB gain and
techniques that seem practical within the predicted state of
its internal electronics gain is 70 dB, the decoy will simulate a
the art. The philosophy here is: "If it hasn't yet been devel1148.2 square meter RCS.
oped, it will be - pretty soon." Therefore, we should be thinks (dBsm) = 38.6 dB - 20 log (8,000) + 70 dB = 38.6 - 78 + 70 =
ing about what we will do about it.
30.6 dBsm
Anti-log (30.6/10) = 1148.2 square meters.

TARGETS

Figure 2: Pulse-Doppler radar processing includes a matrix of range vs.
frequency cells that allows the determination of the frequency of each
received return signal.

Figure 2: Pulse-Doppler radar processing includes a matrix of range vs.
frequency cells that allows the determination of the frequency of each received
return signal.



JED - August 2014

Table of Contents for the Digital Edition of JED - August 2014

The View From Here
Conferences Calendar
Courses Calendar
From the President
Letters
The Monitor
Washington Report
World Report
Back to the Future With HF SIGIHT
HF SIGIHT Battles the Ionosphere
Technology Survey: Solid-State Power Amplifiers
Book Reviews
EW 101
Index of Advertisers
JED Quick Look
JED - August 2014 - cover1
JED - August 2014 - cover2
JED - August 2014 - 3
JED - August 2014 - 4
JED - August 2014 - 5
JED - August 2014 - The View From Here
JED - August 2014 - 7
JED - August 2014 - Conferences Calendar
JED - August 2014 - 9
JED - August 2014 - Courses Calendar
JED - August 2014 - 11
JED - August 2014 - From the President
JED - August 2014 - 13
JED - August 2014 - Letters
JED - August 2014 - The Monitor
JED - August 2014 - 16
JED - August 2014 - 17
JED - August 2014 - 18
JED - August 2014 - 19
JED - August 2014 - 20
JED - August 2014 - 21
JED - August 2014 - Washington Report
JED - August 2014 - 23
JED - August 2014 - World Report
JED - August 2014 - 25
JED - August 2014 - 26
JED - August 2014 - 27
JED - August 2014 - Back to the Future With HF SIGIHT
JED - August 2014 - 29
JED - August 2014 - 30
JED - August 2014 - 31
JED - August 2014 - HF SIGIHT Battles the Ionosphere
JED - August 2014 - 33
JED - August 2014 - 34
JED - August 2014 - 35
JED - August 2014 - 36
JED - August 2014 - Technology Survey: Solid-State Power Amplifiers
JED - August 2014 - 38
JED - August 2014 - 39
JED - August 2014 - 40
JED - August 2014 - 41
JED - August 2014 - 42
JED - August 2014 - 43
JED - August 2014 - 44
JED - August 2014 - Book Reviews
JED - August 2014 - EW 101
JED - August 2014 - 47
JED - August 2014 - 48
JED - August 2014 - Index of Advertisers
JED - August 2014 - JED Quick Look
JED - August 2014 - cover3
JED - August 2014 - cover4
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