JED - July 2015 - 45

E W101

Signal Arriving at Receiver
SYMBOL

SYMBOL

SYMBOL

SYMBOL

Symbol Overlap
SYMBOL

SYMBOL

SYMBOL

SYMBOL

Delayed Multi-path Signal

because all of the many random multi-path signals tend to
cancel each other out.

will pass through periods of constructive and destructive interference. When symbols from the two (or more) received signals
Figure 4: In a multi-path environment, overlapping
symbols
can
cause significant
message
overlap,
"intersymbol
interference"
occurs. This will
cause errors
errors.
DIGITAL SIGNALS IN MULTIPATH ENVIRONMENTS
in the composite signal in the receiver. Error correction coding,
Figure 4 shows two digital signals arriving in a receiver.
as discussed in the October 2011 EW101 column, can be employed
Depending on the duration of the series of bits forming a symbol
to correct compromised symbols.
and the difference in path length for each signal, these two
signals could add constructively or destructively. Remember
WHAT'S NEXT
that each signal travels a meter for every 3 nanoseconds of time
Next month, we will summarize our discussion of radio propaand that multi-path signals can have quite complex propagation
gation formulas. Then, we will start a new series on directed
paths in a complex reflective environment, like an urban area.
energy weapons. For your comments and suggestions, Dave
As transmitters and receivers move about the city, the signals
Adamy can be reached at dave@lynxpub.com. a

The Journal of Electronic Defense | July 2015

Figure 4: In a multi-path environment, overlapping symbols can cause significant message errors.

45

SYNCHRONIZING EW AND CYBER TO
ACHIEVE SPECTRUM DOMINANCE
52nd Annual AOC International Symposium
and Convention | December 1-3, 2015

KEYNOTE AND HIGH RANKING SPEAKERS
Gen John Hyten, Commander, AF Space
Command

Dr. Mark Mayberry, MITRE CTI,
Previous AF Chief Scientist

Dr. Paul Kaminski, DSB

Air Commodore Madelein Spit, Chief NATO
NAFAG, Royal Netherlands AF

Dr. Will Roper, OSD, Director, Strategic
Capabilities Office
Lt Gen Dave Deptula, USAF (Ret.)
Gen Michael Hayden, Previous Director, CIA
Maj Gen Giovanni Fantuzzi, IAF, Air Attaché to US

Exhibit floor is more
than 75% sold! Secure
your space today.
Contact Stew Taylor,
taylor@crows.org.

Dr. Jackie Craig, Australia MOD, DSTO,
Chief EW & Cyber Division
Ms. Michelle Weslander-Quaid, Director
of Innovation, Google (invited)

CONVENTION HOST:

For more information visit www.crows.org/conventions/2015.html

JED-M0715 Convention Ad HP_MKG.indd 1

2015-06-09 4:23 PM


http://www.crows.org/conventions/2015.html

JED - July 2015

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

The View From Here
Conferences Calendar
Courses Calendar
From the President
The Monitor
World Report
The Modern MANPADS – an Evolving Threat
Technology Survey: RF Tuners and Tuner Modules for SIGINT Applications
EW 101
AOC News
Index of Advertisers
JED Quick Look
JED - July 2015 - cover1
JED - July 2015 - cover2
JED - July 2015 - 3
JED - July 2015 - 4
JED - July 2015 - 5
JED - July 2015 - The View From Here
JED - July 2015 - 7
JED - July 2015 - Conferences Calendar
JED - July 2015 - 9
JED - July 2015 - Courses Calendar
JED - July 2015 - 11
JED - July 2015 - From the President
JED - July 2015 - 13
JED - July 2015 - 14
JED - July 2015 - The Monitor
JED - July 2015 - 16
JED - July 2015 - 17
JED - July 2015 - 18
JED - July 2015 - 19
JED - July 2015 - 20
JED - July 2015 - 21
JED - July 2015 - World Report
JED - July 2015 - 23
JED - July 2015 - 24
JED - July 2015 - 25
JED - July 2015 - The Modern MANPADS – an Evolving Threat
JED - July 2015 - 27
JED - July 2015 - 28
JED - July 2015 - 29
JED - July 2015 - 30
JED - July 2015 - 31
JED - July 2015 - 32
JED - July 2015 - Technology Survey: RF Tuners and Tuner Modules for SIGINT Applications
JED - July 2015 - 34
JED - July 2015 - 35
JED - July 2015 - 36
JED - July 2015 - 37
JED - July 2015 - 38
JED - July 2015 - 39
JED - July 2015 - 40
JED - July 2015 - 41
JED - July 2015 - 42
JED - July 2015 - EW 101
JED - July 2015 - 44
JED - July 2015 - 45
JED - July 2015 - AOC News
JED - July 2015 - 47
JED - July 2015 - 48
JED - July 2015 - Index of Advertisers
JED - July 2015 - JED Quick Look
JED - July 2015 - cover3
JED - July 2015 - cover4
https://www.nxtbook.com/naylor/JEDM/JEDM0318
https://www.nxtbook.com/naylor/JEDM/JEDM0218
https://www.nxtbook.com/naylor/JEDM/JEDM0118
https://www.nxtbook.com/naylor/JEDM/JEDM1217
https://www.nxtbook.com/naylor/JEDM/JEDM1117
https://www.nxtbook.com/naylor/JEDM/JEDM1017
https://www.nxtbook.com/naylor/JEDM/JEDM0917
https://www.nxtbook.com/naylor/JEDM/JEDM0817
https://www.nxtbook.com/naylor/JEDM/JEDM0717
https://www.nxtbook.com/naylor/JEDM/JEDM0617
https://www.nxtbook.com/naylor/JEDM/JEDM0517
https://www.nxtbook.com/naylor/JEDM/JEDM0417
https://www.nxtbook.com/naylor/JEDM/JEDM0317
https://www.nxtbook.com/naylor/JEDM/JEDM0217
https://www.nxtbook.com/naylor/JEDM/JEDM0117
https://www.nxtbook.com/naylor/JEDM/JEDM1216
https://www.nxtbook.com/naylor/JEDM/JEDM1116
https://www.nxtbook.com/naylor/JEDM/JEDM1016
https://www.nxtbook.com/naylor/JEDM/JEDM0916
https://www.nxtbook.com/naylor/JEDM/JEDM0816
https://www.nxtbook.com/naylor/JEDM/JEDM0716
https://www.nxtbook.com/naylor/JEDM/JEDM0616
https://www.nxtbook.com/naylor/JEDM/JEDM0516
https://www.nxtbook.com/naylor/JEDM/JEDM0416
https://www.nxtbook.com/naylor/JEDM/JEDM0316
https://www.nxtbook.com/naylor/JEDM/JEDM0216
https://www.nxtbook.com/naylor/JEDM/JEDM0116
https://www.nxtbook.com/naylor/JEDM/JEDM1215
https://www.nxtbook.com/naylor/JEDM/JEDM1115
https://www.nxtbook.com/naylor/JEDM/JEDM1015
https://www.nxtbook.com/naylor/JEDM/JEDM0915
https://www.nxtbook.com/naylor/JEDM/JEDM0815
https://www.nxtbook.com/naylor/JEDM/JEDM0715
https://www.nxtbook.com/naylor/JEDM/JEDM0615
https://www.nxtbook.com/naylor/JEDM/JEDM0515
https://www.nxtbook.com/naylor/JEDM/JEDM0415
https://www.nxtbook.com/naylor/JEDM/JEDM0315
https://www.nxtbook.com/naylor/JEDM/JEDM0215
https://www.nxtbook.com/naylor/JEDM/JEDM0115
https://www.nxtbookmedia.com