JED - May 2013 - 41

TECHNOLOGY SURVEY
A SAMPLING OF RF SIGNAL GENERATORS
By Ollie Holt

leading workhorse in the EW test world. It typically
offers fewer waveform variations than an AWG, but
has excellent stability, the ability to quickly modify
the output signal and typically comes at a lower price
than an AWG. An AWG provides the ability to generate
more complex waveforms; actually an AWG can generate any waveform you can imagine. You can envision
an AWG as more of a fancy playback system. AWGs are
a better fit for testing COMINT systems, but they can
still be used for test and verification of ELINT, ESM
and RWR systems.
An AFG typically offers the following types of wave
shapes: sine, square, triangle, pulsed and ramped.
AFG’s usually have internal or external methods of
modulating the output signal while keeping tight
control of the frequency, phase and amplitude of the
output signal. An AWG can provide these waveforms
and more.
The output signal from an AFG is either created
from a very stable RF oscillator and tuned to the desired frequency with a phase locked loop or by Direct
Digital Synthesis (DDS). If a Direct Digital Synthesizer
is used, it may have some of the waveforms listed
above stored in memory to be retrieved as required.
The output from an AWG is typically created from a
DDS or from a replay from memory.
The survey asked manufacturers to describe the
type of signal generator: AFG, AWG or possibly a hybrid. Next it describes the source of the signal. This
could be an oscillator that can be tuned, a DDS, or it
could be a sampled waveform that is stored in memory
and continually replayed like an AWG.
The frequency range defines the lowest and highest signal frequency that the generator can reproduce.
For typical EW testing, this should at least cover 100
MHz to 18 GHz. Lower and higher frequencies add cost,
but they may be desirable for some types of testing.
The modulation types describe the different ways
the waveform can be modified. The output power
range and step size just describe the lowest to highest
“power out” figure, and the step sizes or resolution of
each step define how much control the operator has in
varying the output signal.
The final columns just describe how the supplier
feels the signal generator could be used and the size,
weight and power of the system.
Next month, our technology survey will feature
airborne flares and IR decoys.

The Journal of Electronic Defense | May 2013

T

his month’s technology survey looks at
RF signal generators that can be used
for defense electronics applications and
especially electronic warfare. EW engineers need ways of characterizing their
system and subsystem designs before
they take them to a test range to ensure the design
meets requirements. To perform these tests, a signal source is needed. Typically RF signal generators
are used to simulate a test signal that could mimic a
threat radar system or a communications system. Or,
it could just generate a tone that is use to calibrate
the EW System.
An RF signal generator is exactly what the name
implies; a device that can generate an RF time- and
amplitude-variant signal to be used for test and verification of RF systems. An RF signal generator may
produce exact replicas of a desired signal and it may
add predictable distortion to aid in system testing.
The world of RF signal generators has changed
much over the years as technology has evolved. Originally, an RF signal generator was not much more than
a tunable stable oscillator that could be modulated
both in amplitude and time. The time modulation was
typically a pulse generator that caused the RF signal
generator to enable and disable the output, creating
pulses similar to a pulsed radar system. The amplitude modulation would just cause the output amplitude of the RF signal generator to vary in amplitude
like the received amplitude variation of a scanning
radar system.
The main activity of an RF signal generator is its
ability to enable operator control and modification
of certain key waveform characteristics, such as frequency, amplitude, phase, waveform shape, rise and
fall times, etc. Today’s RF signal generators provide
three typical methods of developing the desired output signal: create, replicate or generate. “Generate”
is simply tasking the signal generator to pull a signal
from a library of signals and reproduce it. “Replicate”
is the ability to reproduce a signal that can be captured in some manner, stored in memory and regenerated on command. “Create” offers the ability to create
a new signal from mathematical methods or by adjusting controls.
RF signal generators can be separated into two
types: arbitrary function generators (AFGs) and arbitrary waveform generators (AWGs). The AFG is the

41


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JED - May 2013

Table of Contents for the Digital Edition of JED - May 2013

The View From Here
Conferences Calendar
Courses Calendar
From the President
Letters
The Monitor
The Monitor
The Long Hard Road – EW’s Future in Europe
Technology Survey: Signal Generators
Two Domains Are Better Than One
Preview: AOC 50th Anniversary
EW 101
Book Review
AOC News
Index of Advertisers
JED Quick Look
JED - May 2013 - cover1
JED - May 2013 - cover2
JED - May 2013 - 3
JED - May 2013 - 4
JED - May 2013 - 5
JED - May 2013 - The View From Here
JED - May 2013 - 7
JED - May 2013 - Conferences Calendar
JED - May 2013 - 9
JED - May 2013 - Courses Calendar
JED - May 2013 - 11
JED - May 2013 - From the President
JED - May 2013 - 13
JED - May 2013 - Letters
JED - May 2013 - The Monitor
JED - May 2013 - 16
JED - May 2013 - 17
JED - May 2013 - 18
JED - May 2013 - 19
JED - May 2013 - 20
JED - May 2013 - 21
JED - May 2013 - 22
JED - May 2013 - 23
JED - May 2013 - 24
JED - May 2013 - 25
JED - May 2013 - The Monitor
JED - May 2013 - 27
JED - May 2013 - The Long Hard Road – EW’s Future in Europe
JED - May 2013 - 29
JED - May 2013 - 30
JED - May 2013 - 31
JED - May 2013 - 32
JED - May 2013 - 33
JED - May 2013 - 34
JED - May 2013 - 35
JED - May 2013 - 36
JED - May 2013 - 37
JED - May 2013 - 38
JED - May 2013 - 39
JED - May 2013 - 40
JED - May 2013 - Technology Survey: Signal Generators
JED - May 2013 - 42
JED - May 2013 - 43
JED - May 2013 - 44
JED - May 2013 - 45
JED - May 2013 - 46
JED - May 2013 - 47
JED - May 2013 - Two Domains Are Better Than One
JED - May 2013 - 49
JED - May 2013 - 50
JED - May 2013 - 51
JED - May 2013 - Preview: AOC 50th Anniversary
JED - May 2013 - 53
JED - May 2013 - 54
JED - May 2013 - EW 101
JED - May 2013 - 56
JED - May 2013 - 57
JED - May 2013 - 58
JED - May 2013 - Book Review
JED - May 2013 - 60
JED - May 2013 - AOC News
JED - May 2013 - 62
JED - May 2013 - 63
JED - May 2013 - 64
JED - May 2013 - Index of Advertisers
JED - May 2013 - JED Quick Look
JED - May 2013 - cover3
JED - May 2013 - cover4
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