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Fall 2012
Overview of Modern Radar
Electronic Protection
Class Notes
Dave Adamy
Adamy Engineering 1420 Norfolk Ave, Atwater, CA 95301
Tel(209)357-4433 Fax(209)357-4434
www.lynxpub.com
Scope of Course • Radio Propagation
• Radar Jamming
• Electronic Protection
Handout Material
• Course Syllabus
– All visual aids + exercise work-sheets
• EW Pocket Guide
• Antenna & Propagation Slide Rule
• Scientific Calculator
EWPG page number
To Really Understand
Electronic Warfare
You need to have a real feel for Radio
Propagation
Antenna & Propagation Calculator
Ant. Gain reduction vs surface
Fresnel Zone
2 Ray Attenuation
Antenna Calculations
Free Space Attenuation
Calculate dB
1 m = 3.3 ft 1ft = .3m
1
2
Antenna Amplitude Pattern
Antenna & Propagation Calculator
Ant. Gain reduction vs surface
Fresnel Zone
2 Ray Attenuation
Antenna Calculations
Free Space Attenuation
Calculate dB
1 m = 3.3 ft 1ft = .3m
Antenna Scales
Antenna Scales
Antenna Gain & Beamwidth
Set Antenna Diameter (in ft) at Frequency (in GHz)
Antenna Gain & Beamwidth (cont)
Read Boresight Gain at Efficiency
Note 55% efficiency for Narrow Bandwidth antennas
Antenna Gain & Beamwidth (cont)
Read 3 dB Beamwidth at 3 dB line
Antenna Gain & Beamwidth (cont)
Read 10 dB Beamwidth at 10 dB line
First Null
First Null and Sidelobe
First
Sidelobe
Gain reduction vs. Surface Tolerance
Frequency
Gain reduction vs Surface Tolerance
Gain Reduction
Frequency
Surface Tolerance
Gain Reduction
Selection of Propagation Model
Clear
Propagation
Path
Low
Frequency,
Wide
beams,
Near
ground
Link longer
than Fresnel
Zone Distance
Two Ray
Link shorter
than Fresnel
Zone Distance
Line of
Sight
High frequency, Narrow
beams, Far from the ground
Propagation
Path
obstructed
by Terrain
Calculate additional loss
from Knife Edge Diffraction
14
Free Space Attenuation
Also called: Line of Sight Attenuation
Spreading Loss
Determined from: Formula
Nomograph
Slide Rule
Applicable when: Far from ground
Frequency high
Antennas narrow
Free Space Attenuation from Formula
LS = 32.44 + 20 Log(d) + 20 Log(f)
LS = Spreading loss between isotropic antennas (in dB)
d = distance in km
f = frequency in MHz
32 is a fudge factor
Warning: This equation only works if exactly
the right units are input
Some Extra Information, not in book:
If Distance in kilometers: round 32.44 to 32 for 1 dB calculations
If Distance in staturte miles: replace 32.44 with 36.52 (round to 37)
If Distance is in nautical miles: replace 32.44 with 37.74 (round to 38)
15
1
10
100
1000
10,000
20,000
Tra
ns
mis
sio
n D
ista
nc
e (
km
)
Fre
qu
en
cy (
MH
z)
1
10
100
500
40
60
80
100
120
140
160
Spreading Loss (dB)
Free Space Attenuation from Nomograph
15
Antenna & Propagation Calculator
Ant. Gain reduction vs surface
Fresnel Zone
2 Ray Attenuation
Antenna Calculations
Free Space Attenuation
Calculate dB
sm = 1.6 km
nm = 1.15 sm
1
2
Front of Antenna/Propagation slide rule
with line of sight attenuation scales highlighted
1
Free Space Attenuation from Slide Rule
Set Frequency
Free Space Attenuation from Slide Rule
Read Attenuation at Range
Free Space Attenuation from Slide Rule
Also notice short range scale (in meters)
Two Ray Attenuation
Also called: 40 Log d attenuation
distance4 attenuation
Determined from: Formula
Nomograph
Slide Rule
Applicable when: One primary reflector
Frequency low
Antennas wide
Direct and Reflected Rays close to the ground
XMTR RCVR
GROUND
Transmit
Antenna
Height
Receive
Antenna
Height
16
Two Ray Attenuation from Formula
LS = 120 + 40 Log(d) - 20 Log(hT) - 20 Log(hR)
LS = Spreading loss between isotropic antennas (in dB)
d = distance in km
hT = height of transmit antenna in meters
hR = height of receiving antenna in meters
Warning: This equation only works if exactly
the right units are input
Note: There is no frequency term
Minimum antenna heights may apply
30 MHz over good soil 10 meters
(to 3 meters at 60 MHz & 1 meter at 200 MHz)
Higher over salt water
Use higher of actual or minimum antenna height
16
1
10
10,000
100
1000
.1
1
1000
10
100
160
150
140
130
120
110
100
90
80 70
1
10
10,000
100
1000
170
Tra
nsm
itti
ng
A
nte
nn
a H
eig
ht
(m)
Rec
eiv
ing
An
ten
na H
eig
ht
(m)
Pa
th L
en
gth
(km
)
Pro
pa
ga
tio
n L
os
s (
dB
)
.3
3
30
3
300
30
300
3000
3
30
300
3000
Two Ray Attenuation from Nomograph
16
Antenna & Propagation Calculator
Ant. Gain reduction vs surface
Fresnel Zone
2 Ray Attenuation
Antenna Calculations
Free Space Attenuation
Calculate dB
1
2
Back of slide rule
with two-ray calculation scales highlighted
2
Two Ray Attenuation from Slide Rule
Set Transmit antenna height at link distance
Two Ray Attenuation from Slide Rule
Read attenuation at receiving antenna height
Minimum Ant Height – 2 Ray Propagation
Min
imu
m H
eig
ht
(mete
rs)
20 50 100 200 500 1000
.4
.6 .8 1
2
4 6 8
10
20
40
60 80 100
200
Sea
Water
Good Soil
Vert Pol
Poor Soil
Vert Pol
Poor Soil
Hor Pol
Good Soil
Hor Pol
Frequency (MHz)
Fresnel Zone
Determines whether FREE SPACE or
TWO RAY Propagation is appropriate
Determined from: Equation
Slide Rule
If Link is shorter than FZ: Use Free Space
If Link is longer than FZ: Use 2 Ray
Use selected propagation for whole distance
Fresnel Zone Calculation
FZ = [hT x hR x F] / 24,000
Where: FZ = Fresnel Zone in km
hT = Transmit antenna height in meters
hR = Receiving antenna height in meters
F = frequency in MHz
13
Antenna & Propagation Calculator
Ant. Gain reduction vs surface
Fresnel Zone
2 Ray Attenuation
Antenna Calculations
Free Space Attenuation
Calculate dB
1
2
Back of slide rule with Fresnel zone scales highlighted
2
Fresnel Zone from Slide Rule
Align transmit and receive antenna heights
(both in meters)
Fresnel Zone from Slide Rule
Read Fresnel Zone (in km) at Frequency (in MHz)
T R
H
d1
d2 ≥ d1
d2
d = [ 2 / (1 + d1/d2)]d1
Knife Edge Diffraction Geometry
Note: Blind Zone
d1 ≥ d2
If d is set to d1 there is a loss of 1.5 dB Accuracy
This is recommended, since this is only an
Approximation of the loss over a ridge line
17
H
XMTR RCVR
H
Line of Sight
XMTR RCVR Line of Sight
Line of sight path above or below the knife edge
Knife Edge Diffraction Nomograph
17
Jamming Equations
Required J/S
About Jamming Equations
d & R both used for range (in km)
1 sm = 1.6 km, 1 nm = 1.15 sm
Note: ERP = PT + GT (In direction of receiver)
Antenna gains sometimes “qualified”
GS = side lobe gain
(also called GRJ for Gain of radar antenna toward jammer)
GM = main beam gain (for self protection, just called G
RADAR RECEIVED POWER EQUATION
XMTR
RCVR
RCS
PR = PT + 2G - 103 - 20 Log F - 40 Log R + 10 Log RCS dB
PR = ERP + G - 103 - 20 Log F - 40 Log R + 10 Log RCS or
RWR Link
RADAR
10 km
10 kw
30 dBi
8 GHz
1 dBi
Rcvr Sens = -55 dBm
PR = ERP – Loss + GR
20 Log Reff = ERP – 32 -20 Log F + GR – Sens
Eff Range = Antilog[(20 Log d)/20]
RWR Link (2)
RADAR
10 km
10 kw
30 dBi
8 GHz
1 dBi
Rcvr Sens = -55 dBm
PR = ERP – Loss + GR
20 Log Reff = ERP – 32 -20 Log F + GR – Sens
Eff Range = Antilog[(20 Log d)/20]
PR = +100 – 131 + 1 = -30 dBm
20 Log Reff = 100 – 32 - 78 + 1 – ( -55) = 46
Eff Range = Antilog[(46)/20] = 199.5 km
ERP = 100 dBm
RWR Link (3)
RADAR
10 km
10 kw
30 dBi
8 GHz 1 dBi
Rcvr Sens = -55 dBm PR = ERP – Loss + GR
S/L = -20 dB
20 Log Reff = ERP – 32 -20 Log F + GR – Sens
Eff Range = Antilog[(20 Log d)/20]
RWR Link (4)
RADAR
10 km
10 kw
30 dBi
8 GHz 1 dBi
Rcvr Sens = -55 dBm
PR = ERP – Loss + GR
S/L = -20 dB
20 Log Reff = ERP – 32 -20 Log F + GR – Sens
Eff Range = Antilog[(20 Log d)/20]
PR = 80 – 131 + 1 = -50 dBm
20 Log Reff = 80 – 32 - 78 + 1 – (-55) = 26
Eff Range = Antilog[(26)/20] = 20 km
ERP = 80 dBm
GS = 10 dBi
SELF PROTECTION JAMMING
RADAR
J Radar Signal
Jammer Signal
Jammer located on target
Has advantage of Radar Antenna
Can use either Cover or Deceptive Jamming
S = ERPS + G - 103 - 20 Log F - 40 Log R + 10 Log RCS
J = ERPJ + G - 32 - 20 Log F - 20 Log R
Note that distances are the same and both jammer &
radar return are received with antenna gain G
J/S = ERPJ - ERPS + 71 + 20 Log R - 10 Log RCS
STAND-OFF JAMMING
RADAR
J
Radar Signal
•Jammer remote from target
•In side lobe of Radar Antenna
•Uses cover jamming
•Prevents Acquisition
S = ERPS + GM - 103 - 20 Log F - 40 Log RT + 10 Log RCS
J = ERPJ + GS - 32 - 20 Log F - 20 Log RJ
Note that distances and antenna gains are different
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT
- 10 Log RCS
SELF PROTECT BURN THROUGH
RADAR
J
Radar Signal [Reduces by R4]
Jammer Signal [Reduces by R2]
Target (& Jammer)
Approaching Radar
Range at which
there is no longer
adequate J/S
Range
Rcvd
Pw
r
Jammer Skin Return
SELF PROTECT BURN THROUGH EQN
J/S = ERPJ - ERPS + 71 + 20 Log R - 10 Log RCS
20 Log R = ERPS - ERPJ - 71 + 10 Log RCS + J/S (Required)
RBT = Anti-Log {[20 Log R]/20}
Note: RBT = R at Burn through range
Value of
STAND-OFF BURN THROUGH
RADAR
J
Radar Signal [Reduces by d4]
Target
Approaching
Radar
Range at which
there is no longer
adequate J/S
Range
Rcvd
Pw
r
Jammer
Skin Return
STAND-OFF BURN THROUGH EQN
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT
- 10 Log RCS
40 Log RT = ERPS - ERPJ - 71 - GS + GM + 20 Log RJ
+ 10 Log RCS + J/S (Required)
RBT = Anti-Log{[40 Log RT]/40}
Note: RBT = RT at Burn through range
Value of
Jamming Problems
Self Protect J/S Problem
RADAR
J 10 km
J/S = ERPJ - ERPS + 71 + 20 Log R - 10 Log RCS
10 kw
30 dBi 10 sm
100 watts
3 dBi Ant
Self Protect J/S Problem(2)
RADAR
J 10 km
J/S = ERPJ - ERPS + 71 + 20 Log R - 10 Log RCS
10 kw
30 dBi 10 sm
100 watts
3 dBi Ant
J/S = 53 - 100 + 71 + 20 - 10 = 34 dB
+ 70 dBm
ERP = + 100 dBm
ERP = + 53 dBm
Self Protect Burn Through Problem
RADAR
J 10 kw
30 dBi 10 sm
100 watts
3 dBi Ant
20 Log RBT = ERPS - ERPJ - 71 + 10 Log RCS + J/S (Rqd)
RBT = Antilog[(20 Log RBT)/20]
J/S (Rqd) = 2 dB
Self Protect Burn Through Problem(2)
RADAR
J 10 kw
30 dBi 10 sm
100 watts
3 dBi Ant
20 Log RBT = ERPS - ERPJ - 71 + 10 Log RCS + J/S (Rqd)
RBT = Antilog[(20 Log RBT)/20]
J/S (Rqd) = 2 dB
ERP = + 53 dBm
ERP = + 100 dBm
20 Log RBT = 100 – 53 - 71 + 10 + 2 = -12
RBT = Antilog[( -12)/20] = 251 meters
Stand-off J/S Problem
RADAR
J
5 km
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT - 10 Log RCS
10 kw
30 dBi
S/L = -20 dB
10 sm
1 kw
18 dB Ant
Stand-off J/S Problem (2)
RADAR
J
5 km
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT - 10 Log RCS
10 kw
30 dBi
S/L = -20 dB
10 sm
1 kw
18 dB Ant
ERP = + 100 dBm
ERP = + 78 dBm
GS = 10 dBi
J/S = 78 - 100 + 71 + 10 - 30 - 29.5 + 28 - 10 = 17.5 dB
Stand-off Burn-through Problem
RADAR
J 10 kw
30 dBi
S/L = -20 dB
10 sm
1 kw
18 dB Ant
J/S (Rqd) = 2 dB
40 Log RBT = ERPS - ERPJ - 71 – GS + GM + 20 Log RJ+ 10 Log RCS + J/S (Rqd)
RBT = Antilog[(40 Log RBT)/40]
Stand-off Burn-through Problem (2)
RADAR
J 10 kw
30 dBi
S/L = -20 dB
10 sm
1 kw
18 dB Ant
J/S (Rqd) = 2 dB
40 Log RBT = ERPS - ERPJ - 71 – GS + GM + 20 Log RJ+ 10 Log RCS + J/S (Rqd)
RBT = Antilog[(40 Log RBT)/40]
ERP = + 100 dBm
ERP = + 78 dBm
GS = 10 dBi
40 Log RBT = 100 - 78 - 71 – 10 + 30 + 29.5 + 10 + 2 = 12.5
RBT = Antilog[(12.5)/40] = 2 km
Stand-in Jamming Problem
RADAR
J
5 km
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT - 10 Log RCS
10 kw
30 dBi
S/L = -20 dB
10 sm
1 watt
ERP
100 m
Stand-in Jamming Problem (2)
RADAR
J
5 km
J/S = ERPJ - ERPS + 71 + GS - GM - 20 Log RJ + 40 Log RT - 10 Log RCS
10 kw
30 dBi
S/L = -20 dB
10 sm
1 watt
ERP
100 m
ERP = + 100 dBm
ERP = + 30 dBm
GS = 10 dBi
J/S = 30 - 100 + 71 + 10 - 30 +20 + 28 - 10 = 19 dB
Standard Jamming Techniques
Barrage Jamming
Spot Jamming
Swept Spot Jamming
Spoked PPI Display
Power Management
DECEPTIVE JAMMING
• Range
– RGPO, RGPI, Cover Pulse
• Angle
– Inverse Gain
• Velocity
– VGPO
• Monopulse Techniques
– Formation, Formation w/range denial, Blinking
– Cross Pol, Cross Eye, Terrain Bounce,
RANGE GATE PULL-OFF
TARGET
JAMMER
Radar Signal
Skin Return
Jammer
Signal
4
3
2
1
RANGE GATE PULL-OFF
At Radar
Skin Return
Jammer
Signal
Early Gate
Late Gate
1
2
3
4
RANGE GATE PULL-OFF
Radar Resolution Cell
Leading Edge Tracking
Skin Return
Jammer
Signal
Leading
Edge
Energly
Leading Edge Tracker Ignores Delayed Jammer Leading Edge
CCM requires jammer to lead skin return
RANGE GATE PULL-IN
TARGET
JAMMER
Radar Signal
Skin Return
Jammer
Signal
1
2
3
4
RANGE GATE PULL-IN
At Radar
Skin Return
Jammer
Signal
Early Gate
Late Gate
RANGE GATE PULL-IN
Radar Resolution Cell
COVER PULSES
TARGET
JAMMER
Radar Signal
Skin Return
Jammer
Signal
Denies Radar Range Information
Theoretical Inverse Gain
INVERSE GAIN JAMMING (CONSCAN)
SKIN
RETURN
JAMMING
SIGNAL
RADAR
RECEIVED
SIGNAL
INVERSE GAIN JAMMING (CONSCAN)
RADAR TRACKING RESPONSE
Track While Scan Radar
Fan Beam
measures Elevation
Fan Beam
measures Azimuth
Refe
rence
Target
Elevation
Target
Azimuth
Inverse Gain against TWS Radar
Skin Return
Angle Gate
Jammer
Radar
Return
Scan on Receive Only Radar
Steady Beam
On Target
Scans to create
Tracking data
INVERSE GAIN JAMMING (SORO)
SKIN
RETURN
JAMMING
SIGNAL
RADAR
RECEIVED
SIGNAL
AGC Jamming
Doppler Radar Return
Velocity Gate Pull-off
Formation Jamming
Formation Jamming with Range Denial
Blinking
Missile Track with Blinking
Terrain Bounce
Note: Last of Optional Slides
• Some techniques work against non-
multichannel radars only
• Multichannel techniques:
– Described in Section 9.9 of EW101
• Focus in this section on most complex
techniques
– Cross Pol & Cross Eye
• Others will be discussed along with EP
considerations
CONDON
LOBES
CROSS
POLARIZED
RESPONSE
PARABOLIC
DISH
FEED
SIGNAL ARRIVING
FROM OFF AXIS
DIRECTION
Cross Pol Jamming
Cross Polarization Jamming
Received
Signal
Polarization
Transmitted
Signal
Polarization
Vert Rcv
Horr Rcv
Horr Xmt
Vert Xmt
Cross Pol Issues
• Requires very large J/S to overcome
weakness of Condon Lobes
• Works best against short focus parabolic
antennas (Larger Condon Lobes)
• Defeated by polarization filters or flat plate
antennas (No Forward Geometry)
Cross Pol
Cross Eye Jamming
Wavefront with Cross Eye
Cross Eye Miss Distance
Cross Eye Implementation
180 deg
nsec
SW
nsec
SW
EP Techniques • Ultra-low Side Lobe
• Side lobe canceller
• Side Lobe Blanker
• Anti Cross Pol
• Mono-pulse
• Pulse Compression
• Pulse Doppler – Anti Doppler pull-off
– Frequency, range rate correlation
– Anti Chaff
• Leading Edge Tracking
• Anti AGC jamming
• Burn through modes
• Frequency Agility
• PRF Jitter
• Home on Jam Modes
Ultra-low Side Lobe
Target
Reduced
ELINT Range
JAMMER
Reduced J/S
Performance Relative Level Average Level
Ordinary -13 to -30 dB 0 to -5 dBi
Low -30 to -40 dB -5 to -20 dBi
Ultralow Below -40 dB Below -20 dBi From Schleher, EW in Info Age
Coherent Side Lobe Canceller
Appears to Radar
to be reduced signal
In Main Lobe
Signal Received
Stronger in auxiliary
Antenna.
Main
Radar
Antenna
Auxiliary
Antenna
RADAR ADDS
AUXILIARY ANTENNA
SIGNAL 180° OUT OF PHASE
(LIKES CW SIGNALS)
Coherent Sidelobe Canceller
Note that loop bandwidths make CSC respond best
To continuous signals
Cross pole response
May require another
canceller
Pulse signal acts like
It has wide angle.
Requires multiple CSCs
Requires one
Canceller per
Jammer
Vulnerable
To Blinking
(pg 288)
Target Jammers
+ +
NB
Loop
& Ph
Shift
NB
Loop
& Ph
Shift
NB
Loop
& Ph
Shift
Main Beam Signals
- Side lobe Signals
Side Lobe Blanker
Appears to Radar
to be reduced signal
In Main Lobe
Signal Received
Stronger in auxiliary
Antenna.
Main
Radar
Antenna
Auxiliary
Antenna
RADAR BLANKS
RECEIVER INPUT
DURING PULSE
IN SIDELOBE
Sidelobe Blanker
Note that blanker works against pulse signals in S/L
High Duty Factor or
Cover pulses cover
Desired return
Target Jammers
Switch
“Side Lobe”
Antenna
Anti Cross Pol
CONDON
LOBES
CROSS
POLARIZED
RESPONSE
Reduced Condon Lobes Make Cross Pol Jamming Ineffective
Monopulse Tracker
Angle tracking on every pulse
Deceptive Jamming Improves Radar Angle Track
Pulse Compression
Digital
Unless Jamming has correct
Bit phases, effective J/S
Reduced by code length
PULSE
With FM
COMPRESSIVE
FILTER
Linear
FM
Unless Jamming has correct
Frequency slope, effective J/S
Reduced by compression factor
Range/Velocity Correlation
PD radar correlates apparent range rate with Doppler frequency
– If inconsistent, rejects jamming signal
Pulse Position vs. time in RGPO
Time
Leading Edge Tracking
Skin Return
Jammer
Signal
Leading
Edge
Energy Leading Edge Tracker Ignores Delayed Jammer Leading Edge
CCM requires jammer to lead skin return
Anti AGC Jamming
Skin Return
Wideband Jamming Wideband
Channel
Normal
bandwidth
IF Amp
Dicke Fix
Limiter
AGC Loop
Prevents narrow pulses and wideband FM generated
Noise from capturing AGC
Burn Through Modes
• Increased Power
• Increased Duty Factor
Both increase radar detection range
In presence of Jamming
PRF Jitter
PSEUDO-RANDOM PULSE POSITION
PREVENTS RGPO & EXTENDS COVER PULSE TIME
Home on Jam
• Radar detects that jamming is taking place
– Pulse Doppler Radar detects jamming waveforms
• Homes on Jamming signal
– Mono-pulse radars use multiple apertures for angle info on every pulse
• Makes self protection jamming impractical
– Requires stand-off, stand-in jamming or decoys