Overview of Modern Radar Electronic Protection Class Notes

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



Fresnel Zone

2 Ray 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


Read 3 dB Beamwidth at 3 dB line


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


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



Fresnel Zone

2 Ray 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


Read Attenuation at Range


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



Fresnel Zone

2 Ray 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



Fresnel Zone

2 Ray 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 = +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



RWR Link (4)

RADAR

10 km

10 kw

30 dBi

8 GHz 1 dBi

Rcvr Sens = -55 dBm


S/L = -20 dB



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


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


10 kw

30 dBi 10 sm

100 watts

3 dBi Ant

Self Protect J/S Problem(2)

RADAR

J 10 km


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)


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


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)


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)


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


10 kw

30 dBi

S/L = -20 dB

10 sm

1 watt

ERP

100 m

Stand-in Jamming Problem (2)

RADAR

J

5 km


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

Overview of Modern Radar Electronic Protection Class Notes

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