5/27/2018 05 - Introduction to RWR
1/23
2/23/20
GTRI_B-1Copyright by Georgia Tech Research Corporation, 2009
Introduction toRadar Warning Receivers
Robins AFB
February 24, 2009
Presenter: Kim Cole
GTRI_B-2Copyright by Georgia Tech Research Corporation, 2009
What is a Radar Warning Receiver?
A Radar Warning Receiver (RWR) is a pass iveEWsystem that does the following:
Detects RF signals transmitted by radar systems
Identifies the signal by radar type
Manages detected signals
Generates visual and audio cues to pilot
Manages interfaces to other systems
GTRI_B-3Copyright by Georgia Tech Research Corporation, 2009
What the Pilot Sees
5/27/2018 05 - Introduction to RWR
2/23
2/23/20
GTRI_B-4Copyright by Georgia Tech Research Corporation, 2009
CVR SUBSYSTEM
FSRS Subsystem
AM-42345
AM-423135
AM-423225
AM-423315
AS-3305
(45) J1
(135) J2
(Omni) J5
(315) J4
(225) J3
ANT7
E, G, I
(135)
E, G, I
(45)
E, G, I
(225)
E, G, I
(315)
IP1310
Diamond Audio
CM-479
J3F1
J1
F2J4 J2
HSDB
2X 2Y
C/D, E, G, I Band Static Video (TTL)
C-10373F1 F3
F2 J1
J2J5
J4J3
Antenna Control (0-3)
R-2094
J1 J3
J2
RI/D, Control (0-3), CW Strobe, PRF Window
Rec. Int., Discrimn. Video, Bandpass Video
AM-423135
(FSRS)
AM-423225
(FSRS)
AM-423315
(FSRS)
AM-42345
(FSRS)
J1
J2
J5
J6
J3
J4
AM-6971J6 J3 J1
J5
J4 J2
J7
N1
SA-2263
E, G, I Band Video (45, 135, 225, 315)
C/D Band Video (45, 135, 225, 315)Omni Video
CVR
135
J1
J2
J3
CVR
45
J1
J2
J3
CVR
225J1
J2
J3
CVR
315J1
J2
J3
ALQ-213 CMSP
ALR-69 System Block Diagram
GTRI_B-5Copyright by Georgia Tech Research Corporation, 2009
ALR-69 System
GTRI_B-6Copyright by Georgia Tech Research Corporation, 2009
What the Pilot Sees
5/27/2018 05 - Introduction to RWR
3/23
2/23/20
GTRI_B-7Copyright by Georgia Tech Research Corporation, 2009
(Very) Brief History of RWR
RWRs have been around for about 40 years.
First-generation RWRs were used by the US Air Forceduring the Vietnam War in response to Russian radar-guided SAMs deployed in North Vietnam.
The Israelis suffered heavy losses to radar-directedAAA and SAMs during the 1973 Yom Kippur War.
GTRI_B-8Copyright by Georgia Tech Research Corporation, 2009
Example USAF RWR Installations
RWR Type Aircraft
ALR-56C F-15
ALR-56M F-16, C-130, B-1
ALR-69 B-52, A-10, C-130, F-16, C-130
ALR-94 F-22
APR-39 C-130, V-22
GTRI_B-9Copyright by Georgia Tech Research Corporation, 2009
How Does an RWR Work?
Hardware handles detection
Hardware detects radar pulses and converts pulse parameters todigital format
Major hardware components: antennas, RF cables, receiver,signal processor, user I/O devices
Software handles identification and aircrew interface
Software processes digital data to determine what type of radarsystem is illuminating the aircraft and then provides aircrew cues
Major software components: operational flight program andmission data file
5/27/2018 05 - Introduction to RWR
4/23
2/23/20
GTRI_B-10Copyright by Georgia Tech Research Corporation, 2009
Why Do You Need an RWR?
The enemy is out there!
The enemy has air defense systems that are verydependent on radar and RF-guided weapons.
They have surface-to-air-missiles (SAMs), anti-aircraftartillery (AAA), and air-to-air missiles that arecued/targeted/guided by RF signals.
When an enemy radar points at a USAF aircraft, wecan detect that signal and warn the aircrew of thepresence of that weapon system.
GTRI_B-11Copyright by Georgia Tech Research Corporation, 2009
Typical Air Defense System Encounter
MISSILELAUNCHER
MISSILE
TRACKER
TARGETTRACKER
COMMAND
STATIONCOMPUTER
VAN
GTRI_B-12Copyright by Georgia Tech Research Corporation, 2009
SA-2 Surface to Air Missile
5/27/2018 05 - Introduction to RWR
5/23
2/23/20
GTRI_B-13Copyright by Georgia Tech Research Corporation, 2009
Processor
RWR Operational Concept
0
0
7
78
8
GTRI_B-14Copyright by Georgia Tech Research Corporation, 2009
How Do We Measure RWR Performance?
Typical RWR measures of performance (MOPs) are:
Detection range
Response time
Correct ID
DF accuracy
Age out
Performance is usually measured by conducting aflight test on an open-air range.
GTRI_B-15Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
SignalDetection
SignalProcessing
ManageInterfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
5/27/2018 05 - Introduction to RWR
6/23
2/23/20
GTRI_B-16Copyright by Georgia Tech Research Corporation, 2009
Origin of RWR Input
GTRI_B-17Copyright by Georgia Tech Research Corporation, 2009
RWR Frequency Coverage
A typical RWR detects pulsed radar signals in the0.5-18 GHz frequency range.
Frequencyis measured in Hertz
Hertzis a unit of frequency of one cycle per second.
One second
6 Hertz
3 Hertz
GTRI_B-18Copyright by Georgia Tech Research Corporation, 2009
5/27/2018 05 - Introduction to RWR
7/23
2/23/20
GTRI_B-19Copyright by Georgia Tech Research Corporation, 2009
GTRI_B-20Copyright by Georgia Tech Research Corporation, 2009
GTRI_B-21Copyright by Georgia Tech Research Corporation, 2009
Types of Radar Signals
Continuous Wave
Pulsed
5/27/2018 05 - Introduction to RWR
8/23
2/23/20
GTRI_B-22Copyright by Georgia Tech Research Corporation, 2009
Quick Word About Notation for Pulsed Signals
Time
All meant toillustrate
the same
concept.
GTRI_B-23Copyright by Georgia Tech Research Corporation, 2009
What Measurements Does an RWR Make?
For each CW s igna lthe RWR will measure:
Frequency, angle of arrival, and power
For each pulse in a pulsed signal the RWR willmeasure:
Frequency or frequency band, time of arrival (TOA),angle of arrival (AOA or DF), pulse width, and power
For CW or pulsed signals outside the RF coverageof the RWR, no m easurement is made.
GTRI_B-24Copyright by Georgia Tech Research Corporation, 2009
First Step: Detect Signal with Antenna
C/D Band antenna -
One per aircraft
E/J Band antenna -
Four per aircraft
5/27/2018 05 - Introduction to RWR
9/23
2/23/20
GTRI_B-25Copyright by Georgia Tech Research Corporation, 2009
First Step: Detect Signal with Antenna
45
225
315
135
Four E/J band antennas are
installed at quadrant locations
around aircraft.
GTRI_B-26Copyright by Georgia Tech Research Corporation, 2009
F-16 Forward Antenna Installation
GTRI_B-27Copyright by Georgia Tech Research Corporation, 2009
F-16 Aft Antenna Installation
5/27/2018 05 - Introduction to RWR
10/23
2/23/20
GTRI_B-28Copyright by Georgia Tech Research Corporation, 2009
Converting RF Pulse to Digital Data
Receiver
PulseMeasurement
Data
To software
For
Signal processing
Quadrant antennas
GTRI_B-29Copyright by Georgia Tech Research Corporation, 2009
Basic Analog Receivers1 (1/2)
Receiver Advantage Disadvantage
Wideband CrystalVideo
Simple; InexpensiveInstantaneous
High POI in frequency range
No frequency resolutionPoor sensitivity
Poor simultaneous signal
Tuned RF Crystal Video Simple
Frequency measurement
Higher sensitivity than wideband
Slow response time
Poor POI
IFM Relatively simpleFrequency resolution
Instantaneous; High POI
Simultaneous signal problemRelatively poor sensitivity
Narrow Band Scanning
Superhet
High sensitivity
Good frequency resolution
No simultaneous signals
problem
Slow Response
Poor POI
Poor against freq agility
Wideband Superhet Better response timeBetter POI
Spurious signals generatedPoorer sensitivity
GTRI_B-30Copyright by Georgia Tech Research Corporation, 2009
Basic Analog Receivers1 (2/2)
Receiver Advantage Disadvantage
Channelized Wide bandwidthNear instantaneous
Moderate frequency resolution
High complexity, cost
Lower reliability
Limited sensitivity
Microscan Near instantaneousGood frequency resolution
Good dynamic range
Good simultaneous signal capability
High complexityLimited bandwidth
No pulse modulation
information
Critical alignment
Acousto-optic Near instantaneousGood frequency resolution
Good simultaneous signal capability
Good POI
High complexityNew technology
1 Electronic Warfare And Radar Systems Engineering Handbook, NAWCWPNS TP 8347, April 1, 1999
5/27/2018 05 - Introduction to RWR
11/23
2/23/20
GTRI_B-31Copyright by Georgia Tech Research Corporation, 2009
Most Common RWR Receiver Architectures
Filename - 31
Band 1Video
Band 2Video
Band 3Video
Multi-plexer
CompressiveVideo
Amplifier
RFAmplifier
Crystal Video ReceiverTuned Narrowband Superhet
Video
IFAmp
IFFilter
LogVideoAmp
RFFilter
Local
Oscillator
Tuning
GTRI_B-32Copyright by Georgia Tech Research Corporation, 2009
Narrow-Band Superheterodyne Receiver
Narrow bandwidth
-90 dBm sensitivity
Low probability of intercept (POI)
Good signal separation
Measures frequency, PW, power, and AOA
Excellent CW Capability Medium cost
Medium volume
GTRI_B-33Copyright by Georgia Tech Research Corporation, 2009
Wideband Crystal Video Receiver
Wide instantaneous bandwidth
- 45 dBm sensitivity
High probability of intercept
Poor signal separation
Measures frequency band, PW, power, and AOA
Poor CW Capability
Low cost
Small volume
5/27/2018 05 - Introduction to RWR
12/23
2/23/20
GTRI_B-34Copyright by Georgia Tech Research Corporation, 2009
Input Scheduling
Another important RWR term is i npu t schedu l ing.
Both superhet and CVR architectures requiresophisticated input schedulers.
The input schedule is usually defined in the missiondata file.
We have said that a typical RWR covers the 0.5-18GHz frequency range, but they typically do notcollect inputs from the entire range at one time.
GTRI_B-35Copyright by Georgia Tech Research Corporation, 2009
CVR Input Scheduling
A typical CVR RF signal is fed to anamplifier/detector that splits the covered RF rangeinto multiple f requency bands.
A typical CVR l ooks(collects input) from a single RFband at a time.
Example band breaks are shown below.
Band 0 Band 1 Band 2 Band 3
0.5 GHz 2 GHz 8 GHz 12 GHz 18 GHz
GTRI_B-36Copyright by Georgia Tech Research Corporation, 2009
Example CVR Input Schedules
Band Look Time
0 25 ms
1 25 ms
2 25 ms
3 25 ms
Band Look Time
0 10 ms
1 12 ms
2 15 ms
3 15 ms
0 50 ms (conditional)
2 1 ms
3 1 ms
1 20 ms
3 25 ms
Really simple schedule
More realistic schedule
5/27/2018 05 - Introduction to RWR
13/23
2/23/20
GTRI_B-37Copyright by Georgia Tech Research Corporation, 2009
Simple Probability of Intercept Example
Filename - 37
Scanning threat radar
RWR input scheduler
Band 0 Band 1 Band 2 Band 3 Band 0
GTRI_B-38Copyright by Georgia Tech Research Corporation, 2009
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
2 4 6 8 10 12 14 16RF (GHz)
18
Emitter TransmittedFrequency Range
Threat ID
GTRI_B-39Copyright by Georgia Tech Research Corporation, 2009
Superhet Input Scheduler
The input schedule for a superhet receiver is muchmore complex than the input schedule for a CVR.
This is because the superhet is a narrow-bandreceiver, i.e. the total frequency range is broken intomany smaller segments that must be covered.
Superhet input schedulers contain more numerous,shorter looks.
0.5 GHz 2 GHz 8 GHz 12 GHz 18 GHz
5/27/2018 05 - Introduction to RWR
14/23
2/23/20
GTRI_B-40Copyright by Georgia Tech Research Corporation, 2009
Pulse Measurements
If the RWR detects a pulse, it collects a set of datafor that pulse.
The formats differ among various RWRs, but thispulse data is generally called a pu lse descr ip to rwo rd(PDW).
The PDW contains all data collected for a s ing leRFpulse.
GTRI_B-41Copyright by Georgia Tech Research Corporation, 2009
Pulse Descriptor Word
A typical PDW contains time of arrival (TOA), angle,pulse width, power, and frequency (superhet) orfrequency band (CVR).
The ALR-69 PDW format is shown below:
TIME OF ARRIVAL (16 LSBs)
TIME OF ARRIVAL (8 MSBs)PULSE WIDTH
POWER ANGLE
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
IP PP FO1 FO2 PRI DT RB1 RB2 DCB COR CDM B0 B1 B2 B3 B4
GTRI_B-42Copyright by Georgia Tech Research Corporation, 2009
Key Pulse Parameters
Time
FrequencyPulsewidth
Power
PRI
PRI is Pulse Repetition Interval.
5/27/2018 05 - Introduction to RWR
15/23
2/23/20
GTRI_B-43Copyright by Georgia Tech Research Corporation, 2009
Input Buffer
The final output of the Signal Detection componentof the RWR is an Input Buffer.
An Input Buffer is a series of PDWs that werecollected during a single look.
The Input Buffer is processed by the RWR softwareto determine what type radar (or radars) transmittedthe pulses.
GTRI_B-44Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
SignalDetection
SignalProcessing
ManageInterfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
GTRI_B-45Copyright by Georgia Tech Research Corporation, 2009
OFP and MDF
Operat ional Fl ight Program (OFP)
Executable code
Input scheduler
PRI deinterleaver
Track file management
Missile guidancealgorithms
Interface management
Mission Data File (MDF)
Data (no executablecode)
Input schedule
Threat identification
Threat information
Ambiguity resolve tables
Missile guidance data
Filename - 45
5/27/2018 05 - Introduction to RWR
16/23
2/23/20
GTRI_B-46Copyright by Georgia Tech Research Corporation, 2009
Major Signal Processing Components
Filename - 46
PRIDeinterleave
Threat IDAmbiguity
ResolveTrack File
Management
InputBuffer
EmitterTrack
File
GTRI_B-47Copyright by Georgia Tech Research Corporation, 2009
PRI Deinterleaving Algorithm
Many years of research have been done regardingPRI deinterleaving algorithms.
The PRI deinterleaving algorithm is the mostcomplex algorithm, and uses the most processortime, of any function in an RWR OFP.
PRIDeinterleave
InputBuffer
Pulse train statistics:Frequency/band
PRIPower
AnglePulse width
PRI agility info
Quality statistics
GTRI_B-48Copyright by Georgia Tech Research Corporation, 2009
PRI AgilityStable
For a stable PRI emitter the interpulse period isthe same for every pulse.
175 175175 175 175 175 175 175 175 175 175 175 175 175 175 175 175 175 175 175 175 175
5/27/2018 05 - Introduction to RWR
17/23
2/23/20
GTRI_B-49Copyright by Georgia Tech Research Corporation, 2009
PRI AgilityStagger
For a staggered PRI emitter, a set of interpulseperiods are repeated continuously.
2-level stagger
3-level stagger
4-level stagger
150 175175 150 175 150 175 150 175 150 175 150 175 150 175 150 175 150 175 150 175 150
150 150175 225 150 175 225 150 175 225 150 175 225 150 175 225 150 175 225 150 175 225
150 175175 125 200 150 175 125 200 150 175 125 200 150 175 125 200 150 175 125 200 150
GTRI_B-50Copyright by Georgia Tech Research Corporation, 2009
PRI AgilityCycler
For a cyclic PRI emitter a stable PRI is generatedfor N pulses followed by another stable PRI for Npulses, etc.
For example, this cycler generates a PRI of 175 forseven pulses and then a PRI of 150 for four pulses.
175 150175 175 175 175 175 175 150 150 150 150 175 175 175 175 175 175 175 150 150 150
GTRI_B-51Copyright by Georgia Tech Research Corporation, 2009
PRI AgilityJitter
For a jitter PRI emitter, the interpulse periodvaries between every pulse usually within a knownpercentage range.
For example, the pulse train below is a 200 +/- 10%jitter pulse train, i.e. the interpulse periods varyrandomly between 180 and 220.
200 181183 182 201 199 185 217 216 209 188 181 199 207 207 187 183 184 218 203 204 200
5/27/2018 05 - Introduction to RWR
18/23
2/23/20
GTRI_B-52Copyright by Georgia Tech Research Corporation, 2009
PRI Deinterleaving
Filename - 52
Radar Signal A
Radar Signal B
Radar Signal C
Interleaved Signal
GTRI_B-53Copyright by Georgia Tech Research Corporation, 2009
PRI Deinterleaving - Sorting
Hardware Measurement Useful f or Sorting?
Frequency or Frequency Band Yes
Time of Arrival Yes
Angle of Arrival Yes
Power No
Pulse Width Not so much
GTRI_B-54Copyright by Georgia Tech Research Corporation, 2009
Major Signal Processing Components
Filename - 54
PRIDeinterleave
Threat IDAmbiguityResolve
Track FileManagement
InputBuffer
EmitterTrack
File
5/27/2018 05 - Introduction to RWR
19/23
2/23/20
GTRI_B-55Copyright by Georgia Tech Research Corporation, 2009
Threat Identification
Initial threat identification is usually a very simpleprocess.
The MDF assigns an initial threat ID based onfrequency/band and PRI.
So, threat ID is simply finding the correspondingentry in a table in the Mission Data File.
Most initial threat IDs are amb iguousand requireamb igu i ty reso lu t ion.
GTRI_B-56Copyright by Georgia Tech Research Corporation, 2009
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
0 500 1000 1500 2000 2500 3000 3500PRI (microseconds)
4000
Emitter PRI Range
Threat ID
GTRI_B-57Copyright by Georgia Tech Research Corporation, 2009
Major Signal Processing Components
Filename - 57
PRIDeinterleave
Threat IDAmbiguityResolve
Track FileManagement
InputBuffer
EmitterTrack
File
5/27/2018 05 - Introduction to RWR
20/23
2/23/20
GTRI_B-58Copyright by Georgia Tech Research Corporation, 2009
Ambiguity Resolution
Initial threat ID is done based on frequency/band andPRI.
This usually results in an ID that says this could be either ThreatA, Threat C, Threat D, or Threat H.
Additional measurements are used/required to resolveambiguities and determine which a unique ID.
PRI agility (jitter, stagger, cycler)
Multiband
Scan type/rate
Missile guidance
GTRI_B-59Copyright by Georgia Tech Research Corporation, 2009
Major Signal Processing Components
Filename - 59
PRIDeinterleave
Threat IDAmbiguityResolve
Track FileManagement
InputBuffer
EmitterTrack
File
GTRI_B-60Copyright by Georgia Tech Research Corporation, 2009
Track File Management
All RWRs have some concept of a Track File. It maybe called different names in different RWRs, but theconcept is the same.
The Track File is where the OFP stores all threatinformation that is has measured/computed.
5/27/2018 05 - Introduction to RWR
21/23
2/23/20
GTRI_B-61Copyright by Georgia Tech Research Corporation, 2009
Track File Management (cont.)
The Track File management software is almost ascomplex as the PRI Deinterleaving software.
The OFP updates the track file as new informationbecomes available.
There are many sources of new information:correlation, missile guidance, angle, power, PRIagility, etc.
GTRI_B-62Copyright by Georgia Tech Research Corporation, 2009
Track File Management (cont.)
The Emit ter Track Fi le is the m ost im por tant data
mainta ined by th e RWR OFP.
The ETF content affects operation of almost allother OFP functions
Pilot cues (audio and display)
Initiates additional measurements for ambiguityresolution
Alters input scheduling
The ETF is output to other systems in an integratedEW suite and may drive their operation as well.
GTRI_B-63Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
SignalDetection
SignalProcessing
ManageInterfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
5/27/2018 05 - Introduction to RWR
22/23
2/23/20
GTRI_B-64Copyright by Georgia Tech Research Corporation, 2009
User Interface
Buttons/Lamps CRT Display
Audio
Missile launch
New guy
Diamond
GTRI_B-65Copyright by Georgia Tech Research Corporation, 2009
Interface Management
Besides the user interface the OFP also managesother intrasystem and intersystem input/output.
Intrasystem: Setting up pulse collection hardware,messaging on intrasystem hardware interfaces,messaging between OFPs within the RWR, etc.
Intersystem: MIL-STD-1553B data bus (EW Bus andAvionics Bus), blanking interface, etc.
GTRI_B-66Copyright by Georgia Tech Research Corporation, 2009
RWR Challenges
There are many challenges to accurately andeffectively operating an RWR in a real-worldenvironment:
High pulse densities
Interference from other onboard systems
Aircraft maneuvers
Urban noise
Antenna patterns
5/27/2018 05 - Introduction to RWR
23/23
2/23/20
GTRI_B-67Copyright by Georgia Tech Research Corporation, 2009
CVR SUBSYSTEM
FSRS Subsystem
AM-42345
AM-423135
AM-423225
AM-423315
AS-3305
(45) J1
(135) J2
(Omni) J5
(315) J4
(225) J3
ANT7
E, G, I
(135)
E, G, I
(45)
E, G, I
(225)
E, G, I
(315)
IP1310
Diamond Audio
CM-479
J3F1
J1
F2J4 J2
HSDB
2X 2Y
C/D, E, G, I Band Static Video (TTL)
C-10373F1 F3
F2 J1
J2J5
J4J3
Antenna Control (0-3)
R-2094
J1 J3
J2
RI/D, Control (0-3), CW Strobe, PRF Window
Rec. Int., Discrimn. Video, Bandpass Video
AM-423135
(FSRS)
AM-423225
(FSRS)
AM-423315
(FSRS)
AM-42345
(FSRS)
J1
J2
J5
J6
J3
J4
AM-6971J6 J3 J1
J5
J4 J2
J7
N1
SA-2263
E, G, I Band Video (45, 135, 225, 315)
C/D Band Video (45, 135, 225, 315)Omni Video
CVR
135
J1
J2
J3
CVR
45
J1
J2
J3
CVR
225J1
J2
J3
CVR
315J1
J2
J3
ALQ-213 CMSP
ALR-69 System Block Diagram
GTRI_B-68Copyright by Georgia Tech Research Corporation, 2009
The Travels of Joe Pulse
RF RF
Antenna
Pre-amp
AM-6639
J1
J2
Video
pulse
Video
Processor
(A5 CCA)
DMA
Pre-Process
(PRE_PROC)
PRI
Deinterleave
(PRIDE)
Emitter
ID
(EIDR)
ETF Mgt
(ETE)
A6 OFP
Display
Update
A4 OFP
Display
Update
Display
Refresh
IP-1310
Pulse
packet
Input
Buffer
Input
Buffer
Process
BufferPRIDE
Outputs
Threat
ID
ETF
Record
ETF
Record
Display
File
Refresh
Buffer
Air RF cableQuadrant
video signalsFIFO A6 RAM
A6 RAM A6 RAM A6OFP
variables
A6OFP
variables
ETF
ETF A4 RAM A4 RAM I/O
CRTDrive
H/W