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ATC Radar System
Laoag MSSR/RCAG Air Navigation Service
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C O N T E N T S
SYSTEM OVERVIEW OF ATC RADAR SYSTEM CONCEPT OF RADAR
RADAR USED IN AIR TRAFFIC CONTROL
FUNDAMENTALS OF SSR/MSSR
QUESTION AND ANSWER
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SYSTEM OVERVIEW OF ATC RADAR
Ja l 6
Aircraft
Satellite
VSAT
VSATRadarAir Traffic Control
RADAR STATION END-USER STATION
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PHILIPPINE RADAR COVERAGE
WEST
NORTH
SOUTH
EAST
LAO
TAG
MAJ
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CONCEPT OF RADAR
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RADAR (Radio Detection And Ranging)
The detection principle is accomplished by
using an echo principle ie, electromagnetic energy
will be beamed at an object and the reflectedenergy will indicate the presence of the object.
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CLASSIFICATION OF RADAR
a. Location Airborne or Ground-based
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b. Usage Search or Precision Radar
c. Principle of Operation
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Laoag MSSR/RCAG Air Navigation Service
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PRINCIPLE OF OPERATION
a. CW or Continuous Wave Radar
sometimes called as Doppler Radar, primaryused for checking the speed and acceleration
of moving objects.
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b. FM or Frequency Modulated Radar
similar with CW, the transmitted signal is sweptin frequency over a small range about the
carrier. The reflected energy remains at the
frequency with which it left the transmitter.
During the time it takes the energy to return tothe receiver, the transmitter has changed
frequency. The difference in frequency between
reflected signal frequency and the transmitter
frequency upon its return is then detected as
beat frequency and then presented at a suitable
distance measuring device. This indicates the
distance to a fixed target.
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c. Pulse Radar
In a pulse system, the CW transmitter is turned
ON/OFF at a given rate, the time that the
transmitter is turned ON being very short
while the time that is OFF beingcomparatively long. Thus short burst of radio
energy are transmitted while the transmitter
is turned OFF, any echoes returning from a
target may be received easily.
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Civil Aviation Authority of the Philippineshttp://www.caap.gov.ph
N
Azimuth
a. Primary Surveillance Radar (PSR)
Radiated signal Reflected signal
aircraft
RANGE
Range: 150-500km (depends on radiated power,
line-of-sight system)
Accuracy 2 (Azimuth) : 0.2..0.5
(Range) : 400800 m
Frequency : 3000 MHz
1300 MHz
Radar Pulse Power reaches hundreds of kilowatts or even ones of
megawatts
RADAR USED IN AIR TRAFFIC CONTROL
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b. Secondary Surveillance Radar (SSR)
aircraft
INTERROGATION
1030 MHz
REPLY
1090 MHz
TRANSPONDER
Range: 350-500km (line-of-sight system)
Accuracy, 2 (Azimuth): 0.2..0.5 (MSSR)
0.5..1.0 (SSR)
(Range): 200400 m
Radar
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c. Airport Surface Detection Equipment(ASDE)
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d. Precision Approach Radar (PAR)
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ARSR ASR PAR ASDE
Range 200 NM 60 NM 10 NM 3 NM
Frequency 1250-1350 MHz 2700-2900 MHz 9000-9180 MHz 24.25-24.72 GHz
Power Output 2 MW 500 KW 70 KW 30 KW
Pulse Width 3 sec 1sec 0.25sec 0.02sec
PRF Average 346-349 pps 900 pps 2,400 pps 14,000 pps
Noise Figure Less than 3dB Less than 4 dB Less than 3.5 dB Less than 5 dB
Antenna ( RPM) 6 15 2 sweep/sec 60
Ant. Beam (Hor) 1.25 1.3 Less than 0.8 0.3
Ant. Beam (Ver) Cosec2 Cosec2 Less than 0.5 Cosec2
Polarization Hor. / Circ. Hor. / Circ. Linear Circular
Power Tube Klystron Klystron Magnetron Magnetron
PRIMARY RADARS
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SSR ( Terminal and En-route)
Coverage 100 NM for Terminal; 200 NM for En-route
Frequency Uplink: 1030 MHz Downlink: 1090 MHz
Output Power 0.5 1.5KW
RF PULSE
Pulse Width 0.8 0.1 sec
Rising Time 0.05-0.1 sec
Down Time 0.05-0.2 sec
PRF 200-450 pps
Interval of Mode Pulse Mode A: 8 sec Mode C: 21 sec
Interlace A, A/C,A/A/C
SLS Func-tion RSLS/ISLS
Receiver Sensitivity Less -85 dBm for Terminal less -87 dBm for En-route
Discriminate Level Less -79 dBm for Terminal less -81 dBm for En-route
AccuracyAzimuth: 0.5
Range: 0.2 NM
SECONDARY RADAR
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FUNDAMENTALS OF SSR/MSSRaircraft
INTERROGATION MODE
1030 MHz
REPLY MODE
1090 MHz
Radar
Air-to-ground
Ground-to-air
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a. INTERROGATION MODE and REPLY MODE
1. INTERROGATION MODE
1 FOR MILITARY A/C
2 FOR MILITARY A/C
3A COMMON ATC (IDENT)
B CIVIL A/C
C CIVIL A/C (ALTITUDE)
D RESERVED
3S
P1 P3
5S
P1 P3
8S
P1 P3
17S
P1 P3
21S
P1 P3
25S
P1 P3
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2. REPLY CODE FOR MODE 3/A
SSR= 12bit code = 212 = 4096 Transponder Code
MSSR= 24bit code = 224 = 16 M Transponder Code
EMERGENCY CODE (SPECIAL CODE)
7700 Emergency
7600 Radio Failure
7500 Hijack
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0.45S 1.0S
FF C1 A1 C2 A2 C4 A4 B1 D1 B2 D2 B4 D4 SF SPI
4.35S
2.9S
20.3S
CODE PULSEPOSITIONAL
VALUECODE PULSE
POSITIONAL
VALUE
A1 1000 C1 10
A2 2000 C2 20
A4 4000 C4 40
B1 100 D1 1B2 200 D2 2
B4 400 D4 4
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example
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b. SSR DISPLAY SYSTEM
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c. SSR LIMITATIONS
PROBLEM FACTOR SOLUTION
1. Lost Target
1. Lobing (includes multipathlobing)
2. Differential lobing
3. Shadow blocking by the
body of the aircraft
4. Sitting (blind by building
or lay of land)
5. Main beam killing6. Over interrogation
Sharp cut off antenna
Integral SLS antenna
Antenna diversity (A/C)
Removal of obstruction
Radio wave absorber
Integral SLS antenna
Monopulse measurement
2. Split Target (Decline of
azimuth accuracy, decode
miss by data shortage)
1. Lobing and differential
lobing appear partially
2. Resulting from
transponder
When interrogation is
received within reply
suppression time
When interrogation is
received within the
transponder dead time
Sharp cutoff antenna
Integral SLS antenna
Use restriction of ISLS
Restriction of interrogator
(number of site, number of
interrogation, transmitted
power)
Transponder Automatic
Overload Control (AOC)
Removal of obstruction
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..SSR LIMITATIONS
PROBLEM FACTOR SOLUTION
3. False Target (Ghost)
1. Reflection from big
building or mountains
2. Transmission from
sidelobe of antenna
(trigger transponder)
receive reply from
sidelobe antenna3. Interference from reply
which responses to
interrogation of other sites
4. Synchronous garble
5. Fruit
6. Synchronous fruit
ISLS
3 pulse SLS
Integral SLS antenna
RSLS antenna
Area STC
Degarbling
Defruiter
Stagger Trigger
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-2 -1 0 +1 +2
OBA (DEGREES)
OBA
= "SUM" ANTENNA PATTERN
= "DIFFERENCE" ANTENNA PATTERN
= ERROR PATTERN CHARACTERISTIC
= OFF BORESIGHT ANGLE
DEGREE
+2+1-1-2
DIFFERENCIAL
PHASE-90 (+)
(-) +90
GAIN
IMPROVED PERFORMANCE OF SSR
B
H
K
+1
W
MONOPULSE TECHNIQUE
LARGE VERTICAL
APERTURE ANTENNA
ADVANCED SIGNAL
PROCESSING
ELECTRONIC SCANNING
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INTRODUCTION TO MODE-S SSR
Selective addressing and monopulse technique allows to overcome
majority of conventional SSR problems (fruit and garbling)
MODE-S TRANSPONDER
MSSR MODE-S
Operational compatibility for conventional SSR
Enhanced surveillance and high resolution altitude reporting (25-foot
increment)
Mode S transponder may be locked out from All Call interrogations to
avoid garbling
Mode S transponder has an unique address to provide discrete ident
Search (ALL CALL) Interrogations
Selective (ROLL CALL) Interrogations
Datalink capability
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GROUND STATIONINTERROGATION
TRANSPONDER REPLIESMODE A/C
Transponder
MODE-S
Transponder
SSR
MODE
A/C
MODE A MODE A MODE A
MODE C MODE C MODE C
SSR
MODE S
MODE A only ALL CALL MODE A NO REPLY
MODE C only ALL CALL MODE C NO REPLY
MODE A/S only ALL CALL MODE A MODE S
MODE C/S only ALL CALL MODE C MODE S
MODE S NO REPLY MODE S if addressed
MODE S and MODE A/C COMPATIBILITY
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END OF SLIDE
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