JED - June 2016 - 30

channels, with no switching required.)
In addition to standard correlative interferometric DF, the nine, parallel coherent receive channels perform beam
forming and super-resolution."
At Plath, Schwolen-Backes says their
state-of-the-art is a combination of correlative interferometric principles with
vector matching. "We use vector matching to calculate both the amplitude and
the phase of the detected waveform in
parallel. This not only improves bearing accuracy, but is more robust against
multipathing and polarization rotations. Sometimes it only makes sense
to use one of the methods (amplitude or
phase) depending on the antenna, but
the vector matching principle delivers
the best results."


The Journal of Electronic Defense | June 2016


Continuing advances in processing
hardware and software algorithms have
made it possible for exponentially more
intense signal processing and improved
DF capabilities - capabilities essential
for handling LPI signals. Says SchwolenBackes, "The software algorithms are
key to these advanced systems. The
first step is the highly-sophisticated
frequency and time resolution and then
for the DF data signal analysis to see all
the short bursts, ensure that they are
measured correctly, and that the bursts
are aggregated together to the correct
signal independent of its spread over
the spectrum. Finally, when you're talking about mixed sensors and multiple DF
sites and receivers and their results, you
have to ensure that all the data is fused
correctly, so that you are seeing and
hearing one complete signal."
As described by BAE's Vogel, "The
important thing is that evolving technology focus on taking advantage of everything about a given signal that can be
measured and processed to get the best
answer most quickly in an increasingly
challenging operating environment." In
that regard, Vogel points to some of the
key technology areas being pursued at
BAE such as improving throughput for
simultaneous DF measurement in both
azimuth and elevation on many signals.
"It's a fairly novel signal processing approach that does this, and it's really

enabled by modern state-of-the-art processors and receivers, allowing it to be
put into a tactical form factor." Another
focus area is on improving the accuracy of, and increasing the convergence
timelines for, geolocation in challenging
environments. "Here, we're working on
multi-path mitigation using some very
advanced correlation techniques. A lot
of DF techniques are based on correlation interferometry and modern processing allows you to do a lot of very fast
processing on a very rich data set." Another BAE effort addressing operation
in congested environments is aimed at
measuring DF on multiple signals at the
same frequency at the same time. "We
have some novel techniques for doing
that in a way that is very computationally efficient, allowing it to run on an
embedded tactical system." Vogel also
points out that, in addition to improving
performance, it's also important to find
ways to reduce system complexity, such
as the complexity of the arrays, to ease
the integration burdens on platforms.
"It's always a cost driver and we're working on a novel broadband aperture that
significantly reduces the number of antennas and their physical size."
At Thales, Boyet says high-resolution DF techniques such as multiple signal classification (MUSIC) algorithms
can significantly improve DF sensor performance over conventional approaches
in all environments, "by separating the
different co-channel signals, improving the signal-to-noise ratio for detection and DF, reducing signal fading
and allowing for spatial filtering and

beam-forming." To realize their true
advantage, however, such techniques
require significant equipment including multiple receive antennas, multiple
receivers, and high processing capabilities (to reduce the switching of antennas to receivers).
Antenna switching is an important
aspect of the processing requirement for
DF/geolocation systems. While a single
receiver may be able to cover the full
frequency band of interest, individual
antennas can't, with many different
antennas required for the task. As described by Boyet, "Especially with tactical systems, since they won't have as
many receivers as antennas, you need
to switch multiple antennas to a given
receiver, in order to cover a very wide
frequency band." In addition to SWaP
considerations, cost is also a major factor driving system design, the number
of receivers, and ultimately the switching requirements.
Rhode & Schwarz's Strobel has noted
another change in the spectrum in recent
years affecting antenna design and use.
"Over the last ten years, we've seen the
emergence of new wideband digital signals for civilian digital video broadcasting (DVB) and digital audio broadcasting
(DAB), and lots of them." Strobel says
these low-power signals present a big
challenge to active antennas (antennas
with integrated signal amplifiers) because the antennas themselves cause intermodulation. For many applications and
frequency ranges, however, active antennas are a requirement, because a passive
antenna with the required sensitivity


JED - June 2016

Table of Contents for the Digital Edition of JED - June 2016

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
Washington Report
World Report
Advances in COMINT/ DF Systems
Technology Survey: Communications and IED Jammers
SIGINT History
EW 101
Report from the 45th Annual Collaborative EW Symposium
AOC News
2016 AOC International Election Guide
Index of Advertisers
JED Quick Look
JED - June 2016 - cover1
JED - June 2016 - cover2
JED - June 2016 - 3
JED - June 2016 - 4
JED - June 2016 - 5
JED - June 2016 - The View From Here
JED - June 2016 - 7
JED - June 2016 - Conferences Calendar
JED - June 2016 - 9
JED - June 2016 - Courses Calendar
JED - June 2016 - 11
JED - June 2016 - From the President
JED - June 2016 - 13
JED - June 2016 - 14
JED - June 2016 - The Monitor
JED - June 2016 - 16
JED - June 2016 - 17
JED - June 2016 - 18
JED - June 2016 - 19
JED - June 2016 - 20
JED - June 2016 - 21
JED - June 2016 - Washington Report
JED - June 2016 - 23
JED - June 2016 - World Report
JED - June 2016 - 25
JED - June 2016 - Advances in COMINT/ DF Systems
JED - June 2016 - 27
JED - June 2016 - 28
JED - June 2016 - 29
JED - June 2016 - 30
JED - June 2016 - 31
JED - June 2016 - 32
JED - June 2016 - Technology Survey: Communications and IED Jammers
JED - June 2016 - 34
JED - June 2016 - 35
JED - June 2016 - 36
JED - June 2016 - 37
JED - June 2016 - 38
JED - June 2016 - 39
JED - June 2016 - 40
JED - June 2016 - 41
JED - June 2016 - 42
JED - June 2016 - SIGINT History
JED - June 2016 - 44
JED - June 2016 - 45
JED - June 2016 - EW 101
JED - June 2016 - 47
JED - June 2016 - Report from the 45th Annual Collaborative EW Symposium
JED - June 2016 - 49
JED - June 2016 - AOC News
JED - June 2016 - 2016 AOC International Election Guide
JED - June 2016 - 52
JED - June 2016 - 53
JED - June 2016 - 54
JED - June 2016 - 55
JED - June 2016 - 56
JED - June 2016 - Index of Advertisers
JED - June 2016 - JED Quick Look
JED - June 2016 - cover3
JED - June 2016 - cover4