JED - October 2015 - 33

THE AESA CHAMELEON
Owing to the existence of two uncontrollable variables, no test equipment manufacturer, software vendor,
prime contractor or other organization
can create an ideal solution to EW system simulation and testing. The first of
these variables is technological change,
which is occurring so rapidly that today's state-of-the-art will be tomorrow's
standard fare. Leading these advances
are the core components of every EW
and radar system: analog-to-digital
converters (ADCs) and digital-to-analog

The most advanced
COTS instruments
employed in EW testing
must as a rule have
performance equal to
or ideally better than
the EW system they
must test, and achieving
this is the instrument
manufacturer's
primary goal.
converters (DACs), FPGAs, GPUs, and
general-purpose processors.
The second variable is that adversaries are also achieving technological advances at a pace that accelerates every
year. Chief among these is the AESA radar. Multi-mode AESA radars are entering service with many nations around
the world. These radars often feature
chameleon-like capabilities that make
them formidable threats. Among many
other things, they can simultaneously
operate at many different frequencies,
use active beamforming to create multiple sub-beams (each one each transmitting at a different frequency), randomly
change the frequency and other characteristics of each pulse, increase or
decrease the RF power emitted by each
antenna element to avoid detection, employ multiple modulation types including various types of spread-spectrum
techniques, function in a passive role
in some sectors but not in others, and a
long list of other attributes.
Perhaps most amazing is their increasing ability to gather enough information about a target to derive its
radar cross section, engine modulation
and channel effects from the received
return, effectively creating a threedimensional image of the target. Using stored information about known
targets, they can identify what type of
aircraft it is tracking and perhaps its EW
and ECM capabilities. All of this gives
the radar a decided advantage.

THE BANDWIDTH CHALLENGE
The most advanced COTS instruments employed in EW testing must
as a rule have performance equal to or
ideally better than the EW system they
must test, and achieving this is the instrument manufacturer's primary goal.
One of the most daunting challenges
is the seemingly endless trend toward
increasing bandwidth. Compared to EW
systems, which cover vast frequency
ranges, radars have traditionally been
narrowband, operating over a frequency range of a few hundred megahertz.
This has changed dramatically, as radar
systems today routinely have bandwidths of 1 GHz or even 2 GHz and are
projected to increase to 4 GHz by the
end of the decade.
Every increase in a radar's signal and
operating bandwidth has a systemic
effect on an EW system that ripples
through all its functions. For example,
wider bandwidth and faster sample
rates dramatically increase the number
of samples the system must collect and
process, and there are limits on how
much and how fast this can be accomplished. Not only must the data (that is,
I and Q samples) collected by an EW system be processed, it must also be stored,
which requires very-high-performance
(and expensive) solid-state memory and
a high-speed system bus.
Recording signals occupying 2 GHz of
bandwidth, even over short periods, creates terabytes of data, and the only way
to effectively process it is by using highspeed signal processing implemented in
FPGAs and (or) GPUs. This hardware is
complemented by software that can sort
signals of interest from the rest, sending
only those selected (a reduced number
and thus less data) on to additional signal
processors for more detailed processing.
After this, the EW system must transmit
a response, which requires even more
analysis and processing. And, as usual,
all of this must be performed in near real
time, as the response time "window" is
dictated by the adversary threat system.
So, regardless of how much data an EW
system must process, it still has the same
limited amount of time to do it.
Latency is another critical factor affecting EW system performance, as well
as the test system designed to simu-

The Journal of Electronic Defense | October 2015

radars can modify existing waveforms
in real-time (pulse to pulse) during
operation. Consequently, it is practically impossible to identify all possible
threats, so advanced EW systems must
dynamically generate countermeasures
"on the fly" using high-speed digital
signal processing and software.
All of these factors, as well as the vagaries of signal propagation and interference, must be considered in order to
produce a simulated threat environment
that represents actual conditions. This
can be accomplished quite effectively
using signal building and channel simulation software to create the waveforms
or waveform sequences. Discrete arbitrary waveform generators (AWGs) or
vector signal generators (VSGs) fulfill
the task of reproducing the resulting
signals.
Of the stages of EW system simulation and evaluation, the laboratory approach is considerably less expensive,
and while AVGs and VSGs generally possess limited multi-emitter evaluation
capabilities, they can nevertheless reduce the amount of testing required on
more sophisticated threat environment
generators, installed system test facilities and open-air ranges along with
the amount of redesign and reprogramming required. As such, they are early-stage evaluation systems that are
designed to complement rather than
replace them. They have the benefit of
being closed-loop systems that give designers complete control over the test,
evaluation, and "tweaking" required
during development, and they can be
reused or repurposed at little or no additional cost.

33



JED - October 2015

Table of Contents for the Digital Edition of JED - October 2015

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
Going Small: Jamming the Mini-Drones
EW Simulation and Testing: Keeping Up With the Threat
Technology Survey: EW and SIGINT Antennas
EW 101
Index of Advertisers
JED Quick Look
JED - October 2015 - cover1
JED - October 2015 - cover2
JED - October 2015 - 3
JED - October 2015 - 4
JED - October 2015 - 5
JED - October 2015 - The View From Here
JED - October 2015 - 7
JED - October 2015 - Conferences Calendar
JED - October 2015 - 9
JED - October 2015 - Courses Calendar
JED - October 2015 - 11
JED - October 2015 - From the President
JED - October 2015 - 13
JED - October 2015 - 14
JED - October 2015 - The Monitor
JED - October 2015 - 16
JED - October 2015 - 17
JED - October 2015 - 18
JED - October 2015 - 19
JED - October 2015 - 20
JED - October 2015 - 21
JED - October 2015 - World Report
JED - October 2015 - 23
JED - October 2015 - 24
JED - October 2015 - 25
JED - October 2015 - Going Small: Jamming the Mini-Drones
JED - October 2015 - 27
JED - October 2015 - 28
JED - October 2015 - 29
JED - October 2015 - 30
JED - October 2015 - EW Simulation and Testing: Keeping Up With the Threat
JED - October 2015 - 32
JED - October 2015 - 33
JED - October 2015 - 34
JED - October 2015 - Technology Survey: EW and SIGINT Antennas
JED - October 2015 - 36
JED - October 2015 - 37
JED - October 2015 - 38
JED - October 2015 - 39
JED - October 2015 - 40
JED - October 2015 - 41
JED - October 2015 - 42
JED - October 2015 - 43
JED - October 2015 - EW 101
JED - October 2015 - 45
JED - October 2015 - 46
JED - October 2015 - 47
JED - October 2015 - 48
JED - October 2015 - Index of Advertisers
JED - October 2015 - JED Quick Look
JED - October 2015 - cover3
JED - October 2015 - cover4
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