introduction to radar warning receiver
TRANSCRIPT
2/23/2009
1
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 passive EW system 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
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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
J3F1J1
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
CVR135
J1
J2
J3
CVR45
J1
J2
J3
CVR
225
J1
J2
J3
CVR
315
J1
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
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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 Force during the Vietnam War in response to Russian radar-guided SAMs deployed in North Vietnam.
• The Israelis suffered heavy losses to radar-directed AAA 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 to digital 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 radar system is illuminating the aircraft and then provides aircrew cues
• Major software components: operational flight program and mission data file
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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 very dependent on radar and RF-guided weapons.
• They have surface-to-air-missiles (SAMs), anti-aircraft artillery (AAA), and air-to-air missiles that are cued/targeted/guided by RF signals.
• When an enemy radar points at a USAF aircraft, we can detect that signal and warn the aircrew of the presence of that weapon system.
GTRI_B-11Copyright by Georgia Tech Research Corporation, 2009
Typical Air Defense System Encounter
MISSILELAUNCHER
MISSILETRACKER
TARGETTRACKER
COMMANDSTATION
COMPUTERVAN
GTRI_B-12Copyright by Georgia Tech Research Corporation, 2009
SA-2 Surface to Air Missile
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GTRI_B-13Copyright by Georgia Tech Research Corporation, 2009
Processor
RWR Operational Concept
0
0
7
7
8
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 a flight test on an open-air range.
GTRI_B-15Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
Signal
Detection
Signal
Processing
Manage
Interfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
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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 the 0.5-18 GHz frequency range.
• Frequency is measured in “Hertz”
• Hertz is a unit of frequency of one cycle per second.
One second
6 Hertz
3 Hertz
GTRI_B-18Copyright by Georgia Tech Research Corporation, 2009
2/23/2009
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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
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GTRI_B-22Copyright by Georgia Tech Research Corporation, 2009
Quick Word About Notation for Pulsed Signals
Time
All meant to
illustrate
the same
concept.
GTRI_B-23Copyright by Georgia Tech Research Corporation, 2009
What Measurements Does an RWR Make?
• For each CW signal the RWR will measure:
• Frequency, angle of arrival, and power
• For each pulse in a pulsed signal the RWR will measure:
• 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 coverage of the RWR, no measurement 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
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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
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GTRI_B-28Copyright by Georgia Tech Research Corporation, 2009
Converting RF Pulse to Digital Data
Receiver
Pulse
Measurement
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 Crystal
Video
Simple; Inexpensive
Instantaneous
High POI in frequency range
No frequency resolution
Poor sensitivity
Poor simultaneous signal
Tuned RF Crystal Video Simple
Frequency measurement
Higher sensitivity than wideband
Slow response time
Poor POI
IFM Relatively simple
Frequency resolution
Instantaneous; High POI
Simultaneous signal problem
Relatively 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 time
Better POI
Spurious signals generated
Poorer sensitivity
GTRI_B-30Copyright by Georgia Tech Research Corporation, 2009
Basic Analog Receivers1 (2/2)
Receiver Advantage Disadvantage
Channelized Wide bandwidth
Near instantaneous
Moderate frequency resolution
High complexity, cost
Lower reliability
Limited sensitivity
Microscan Near instantaneous
Good frequency resolution
Good dynamic range
Good simultaneous signal capability
High complexity
Limited bandwidth
No pulse modulation
information
Critical alignment
Acousto-optic Near instantaneous
Good frequency resolution
Good simultaneous signal capability
Good POI
High complexity
New technology
1 Electronic Warfare And Radar Systems Engineering Handbook, NAWCWPNS TP 8347, April 1, 1999
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GTRI_B-31Copyright by Georgia Tech Research Corporation, 2009
Most Common RWR Receiver Architectures
Filename - 31
Band 1
Video
Band 2
Video
Band 3
Video
Multi-
plexer
Compressive
Video
Amplifier
RF
Amplifier
Crystal Video ReceiverTuned Narrowband Superhet
Video
IF
Amp
IF
Filter
Log
Video
Amp
RF
Filter
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
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GTRI_B-34Copyright by Georgia Tech Research Corporation, 2009
Input Scheduling
• Another important RWR term is input scheduling.
• Both superhet and CVR architectures require sophisticated input schedulers.
• The input schedule is usually defined in the mission data file.
• We have said that a typical RWR covers the 0.5-18 GHz frequency range, but they typically do not collect 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 an amplifier/detector that splits the covered RF range into multiple frequency bands.
• A typical CVR looks (collects input) from a single RF band 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
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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 much more complex than the input schedule for a CVR.
• This is because the superhet is a narrow-band receiver, i.e. the total frequency range is broken into many 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
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GTRI_B-40Copyright by Georgia Tech Research Corporation, 2009
Pulse Measurements
• If the RWR detects a pulse, it collects a set of data for that pulse.
• The formats differ among various RWRs, but this pulse data is generally called a pulse descriptor word (PDW).
• The PDW contains all data collected for a single RF pulse.
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) or frequency 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.
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GTRI_B-43Copyright by Georgia Tech Research Corporation, 2009
Input Buffer
• The final output of the Signal Detection component of the RWR is an Input Buffer.
• An Input Buffer is a series of PDWs that were collected during a single look.
• The Input Buffer is processed by the RWR software to determine what type radar (or radars) transmitted the pulses.
GTRI_B-44Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
Signal
Detection
Signal
Processing
Manage
Interfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
GTRI_B-45Copyright by Georgia Tech Research Corporation, 2009
OFP and MDF
Operational Flight Program (OFP)
• Executable code
• Input scheduler
• PRI deinterleaver
• Track file management
• Missile guidance algorithms
• Interface management
Mission Data File (MDF)
• Data (no executable code)
• Input schedule
• Threat identification
• Threat information
• Ambiguity resolve tables
• Missile guidance data
Filename - 45
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GTRI_B-46Copyright by Georgia Tech Research Corporation, 2009
Major Signal Processing Components
Filename - 46
PRI
DeinterleaveThreat ID
Ambiguity
ResolveTrack File
Management
Input
Buffer
Emitter
Track
File
GTRI_B-47Copyright by Georgia Tech Research Corporation, 2009
PRI Deinterleaving Algorithm
• Many years of research have been done regarding PRI deinterleaving algorithms.
• The PRI deinterleaving algorithm is the most complex algorithm, and uses the most processor time, of any function in an RWR OFP.
PRI
Deinterleave
Input
Buffer
Pulse train statistics:
Frequency/band
PRI
Power
Angle
Pulse 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 is the 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
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GTRI_B-49Copyright by Georgia Tech Research Corporation, 2009
PRI AgilityStagger
• For a “staggered PRI” emitter, a set of interpulse periods 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 generated for N pulses followed by another stable PRI for N pulses, etc.
• For example, this cycler generates a PRI of 175 for seven 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 period varies between every pulse usually within a known percentage range.
• For example, the pulse train below is a 200 +/- 10% jitter pulse train, i.e. the interpulse periods vary randomly 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
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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 for 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
PRI
DeinterleaveThreat ID
Ambiguity
ResolveTrack File
Management
Input
Buffer
Emitter
Track
File
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GTRI_B-55Copyright by Georgia Tech Research Corporation, 2009
Threat Identification
• Initial threat identification is usually a very simple process.
• The MDF assigns an initial threat ID based on frequency/band and PRI.
• So, “threat ID” is simply finding the corresponding entry in a table in the Mission Data File.
• Most initial threat IDs are ambiguous and require ambiguity resolution.
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
PRI
DeinterleaveThreat ID
Ambiguity
ResolveTrack File
Management
Input
Buffer
Emitter
Track
File
2/23/2009
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GTRI_B-58Copyright by Georgia Tech Research Corporation, 2009
Ambiguity Resolution
• Initial threat ID is done based on frequency/band and PRI.
• This usually results in an ID that says “this could be either Threat A, Threat C, Threat D, or Threat H”.
• Additional measurements are used/required to resolve ambiguities 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
PRI
DeinterleaveThreat ID
Ambiguity
ResolveTrack File
Management
Input
Buffer
Emitter
Track
File
GTRI_B-60Copyright by Georgia Tech Research Corporation, 2009
Track File Management
• All RWRs have some concept of a Track File. It may be called different names in different RWRs, but the concept is the same.
• The Track File is where the OFP stores all threat information that is has measured/computed.
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GTRI_B-61Copyright by Georgia Tech Research Corporation, 2009
Track File Management (cont.)
• The Track File management software is almost as complex as the PRI Deinterleaving software.
• The OFP updates the track file as new information becomes available.
• There are many sources of new information: correlation, missile guidance, angle, power, PRI agility, etc.
GTRI_B-62Copyright by Georgia Tech Research Corporation, 2009
Track File Management (cont.)
• The Emitter Track File is the most important data maintained by the RWR OFP.
• The ETF content affects operation of almost all other OFP functions
• Pilot cues (audio and display)
• Initiates additional measurements for ambiguity resolution
• Alters input scheduling
• The ETF is output to other systems in an integrated EW suite and may drive their operation as well.
GTRI_B-63Copyright by Georgia Tech Research Corporation, 2009
Simplified RWR Processing Flow
Signal
Detection
Signal
Processing
Manage
Interfaces
RF
Input
BufferEmitter
Track
File
Hardware SoftwareSoftware
2/23/2009
22
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 manages other 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 and Avionics Bus), blanking interface, etc.
GTRI_B-66Copyright by Georgia Tech Research Corporation, 2009
RWR “Challenges”
• There are many challenges to accurately and effectively operating an RWR in a real-world environment:
• High pulse densities
• Interference from other onboard systems
• Aircraft maneuvers
• Urban noise
• Antenna patterns
2/23/2009
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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
J3F1J1
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
CVR135
J1
J2
J3
CVR45
J1
J2
J3
CVR
225
J1
J2
J3
CVR
315
J1
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
-am
p
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
CRT
Drive
H/W