JED - June 2016 - 26

New Signals, New Thr

Advanced DF Systems and Techni

A
By John Haystead

The Journal of Electronic Defense | June 2016

26

Although direction finding (DF) systems
are generally thought of as intelligencegathering tools for locating an RF emitter of some type, such as a radio or
radar, in fact, accurate and high-speed
DF capabilities are critical to all manner of military systems including selfprotection suites, homing weapons, and
real-time situational awareness tools.
To serve this myriad of applications,
a number of different techniques have
been developed over the years ranging
from classic Watson-Watt and Doppler
angle-of-arrival (AOA) techniques to
time difference of arrival (TDOA), power
of arrival (POA) and hybrid approaches.
With further advancements in signal
processing technology, more complex
approaches, such as correlative/coherent interferometry, vector matching
and others, have also become possible.
Ultimately, however, it is the overall
mission requirement, the sophistication of the signal being sought, and the
physical environment in which a system
is operating that determines the best
technique or combination of DF techniques for the job.

IS IT DF OR GEOLOCATION?
In the tactical operational environment, the term "geolocation" often
supplants direction finding when describing the purpose and capabilities
of systems. Says Martin Atanassov, Director of Marketing at Rohde & Schwarz
(Munich, Germany), "Geolocation is the
state-of-the-art today. Three or more advanced scanning DF receivers at different locations can automatically deliver
results to a DF server which then correlates and calculates the exact position of
the emitter. Even with only a short-time
emission or signal, you can get a geolocation result in nearly real time."

But, as pointed out by Dr. Andreas
Schwolen-Backes, Chief Technology Officer, Plath (Hamburg, Germany), the
distinction still depends on the requirements/mission of the user. "Sometimes
these requirements can be met using
multi-position location fixing, or a 'running fix', where a mobile DF system, such
as an aircraft or UAV, takes multiple
bearings of an emitter over a short time
to determine its position. This 'DF-onthe-move' is also typically the case for
a weapon system homing in on a target
in the last mile without connectivity to
a network. In these cases, geolocation
techniques will not work, but the classic
Watson-Watt AOA DF approach will."
Didier Boyet, Electronic Warfare &
Radiosurveillance Business Segment
Manager at Thales Communications &
Security (Colombes, France), agrees,
noting that other DF techniques can also
allow for instantaneous geolocation,
such as the simultaneous detection and
determination of both the azimuth and
elevation of a signal combined with a
digital terrain mapping capability. "This
can give you an indication of whether
the emitter is on the top of a hill or at
sea level, and although it will require
specialized hardware and software to
detect both azimuth and elevation, it
may provide instantaneous geolocation
without the use of an on-the-move airborne platform."
Schwolen-Backes says the distinction will ultimately still depend on the
signal and mission scenario. "In the case
of short-burst or low-probability-of-intercept (LPI) transmissions, it's not sufficient to monitor and DF the signals via
a classical search or monitoring receiver.
When you expect these types of signals
in your mission, you have to ensure that
each detection of an emission will lead

to a DF result. This is especially important when we talk about self-protection
systems, where every second counts."
On the other hand, Schwolen-Backes
acknowledges that in the tactical battlefield environment, geolocation is
a requirement for almost all systems,
"because users are normally interested
in who is doing what, when, why and
where. But, for the 'where,' the DF results
still have to deliver the most important
input to the geolocation calculation."
Eric Vogel, SIGINT Program Director at
BAE Systems (Nashua, NH), agrees that



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
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