o t & e for esm systems and the use of simulation for...

O T & E for ESM Systems and the use of simulation for

system performance clarification

Tuesday 11 March 2014 © EW Defence Limited Slide 1 of 52

Dr. Sue Robertson

EW Defence Limited

United Kingdom

e-mail: [email protected]


Summary of Presentation

Analysis of Trials Data

Why ESM Testing is needed in an Operational Environment

The Choice of a suitable Trials Area

The simulation of Radar Pulses

Example of the use of Trials Data to identify and solve ESM Performance Issues

The use of trials data for ELINT database and ESM Emitter Library Population

Why OT&E is needed


Although testing of ESM systems in a laboratory environment gives useful

indications of system performance, testing in the real world is needed to

determine how the system will work and to aid the optimisation of the system.

Factors such as multipath reflections from the surface of the aircraft and from

objects on the ground affect the performance of the system.

Features of the ESM installation on an aircraft, such as the location of the

antennas also affect system performance.

Common problems with ESM systems such as multi-tracking for single

radars, poor parameter measurement and errors in direction-finding can be

identified and rectified by using test flights in an Operational setting.

© EW Defence Limited Slide 4 of 52

Ideal picture seen by an Electronic Surveillance System

Radar 1

Radar 2

Radar 3

Aircraft

Route

Tracks at correct DOA Fixes with Error Ellipses

Tuesday 11 March 2014


Actual picture seen by an Electronic Surveillance System

Radar 1

Radar 2

Radar 3

Aircraft

Route

Tracks at correct DOA

Extra Tracks at incorrect DOA

Location Fixes with

Error Ellipses



Planning for a Trial

Simulation of Pulse Data for Comparison with Recorded Trials Data

Selection of a Suitable RF Environment

Definition of Aircraft Route and Altitude Profile

Gathering of Ground truth

Definition of Trials Objective

E.g. To Test Direction Finding Accuracy

To check the Performance of the pulse De-interleaver

To make sure that intercepts are Created for radars that should be seen

Ideally an area where the radar pulse density is low

Find locations and types of land-based radars

Build up a picture of shipping in the trials area


AIS Data Showing Ships in Malacca Straight and Singapore

Selection of a Suitable Trials Environment


AIS Targets in South China Sea

Selection of a Suitable Trials Environment


Air Traffic Control radars in East Malaysia

1. A 60 NM Primary Surveillance Radar (PSR) co-mounted with 200 NM monopulse SSR located on Bukit

Kepayang, 1 NM NE of Kota Kinabalu International Airport (055638.7N 1160352.3E)

2. A 60 NM Primary Surveillance Radar (PSR) co-mounted with 200 NM monopulse SSR located in Kuching

International Airport ( 012848.08 N 1102003.90 E)

3. A 60 NM Terminal Primary Approach Radar co-mounted with a 200 NM monopulse SSR located at Miri Airport

(041929.8N 1135915.8E)

4. A 50 NM Terminal Approach Radar with co-mounted 250 NM conventional SSR located at Labuan Air Force

Base (051526.9N 1150937.7E)

Source: Malaysia Aeronautical Information Publication (AIP)

Data for Ground Truth

Other Airfield radars in East Malaysia & Brunei

Sibu (021523.2N 1115904.4E)

Tawau (041415.4N 1180005.3E)

Bandar Seri Bagawan (4.9442 N 114.9283E)

Sibu Radar Tower


Weather Radars

Coastal Surveillance Radar in East Malaysia

There are 3 coastal surveillance radars in East Malaysia – provided as

part of project 1206.

Pulau Balambagan 7.283085N 116.92744E

Pulau Gaya 6.022125N 116.02650E

Pulau antanani 6.707025N 116.34932E

Data for Ground Truth

Kota Kinabalu 5.76472N 116.058E 5 GHz

Kuching 1.36472N 110.337E 5 GHz

Miri 4.21528N 113.988E 3GHz

Sandakan 5.90167N 118.048E 5 GHz

Bintulu 3.12417N 113.019E 5 GHz

There are 5 Weather Radars in East Malaysia


Radars in East Malaysia

ATC Weather Radar Coastal Surveillance

Aircraft Flight Profile


The best flight profile is one where a repeatable flight profile can be flown, for example

a race track or a box route.

Ideally the aircraft should fly for about 10 minutes on a straight track before turning to

allow the ESM picture to stabilise or to build up a new picture if the system is reset.

Aircraft Speed (kts) Approx Distance (km)

80 25

120 40

200 60

300 90

500 150

1000 300

The distance to be travelled on each straight track of the route will depend on the

aircraft speed.

.

Aircraft Flight Profile


Altitude

The altitude at which the trial is flown will determine how far the ESM can “see”.

The radar range (R) is limited by the radar equation

Power Received ∝ 1/R4

The ESM only has to receive pulses that have been transmitted by the radar, so

for the ESM

Power Received ∝1/R2

For example, a radar with a range of 60 nautical miles could be seen at a range

of 3600 nm by an ESM, if is wasn’t for the curvature of the earth.

The radar horizon which increases with altitude is the real governing factor for the

range at which the ESM can see the radar.

Aircraft Altitude (ft) Radar Horizon(km)

200 32

1000 72

2000 102

5000 162

10000 230

20000 320


Illustration of Radar Horizon Rings

ATC Weather Radar Coastal Surveillance

Altitude 1000ft,

horizon 75 km

Altitude 2000ft,

horizon 100 km

Altitude 4500ft,

horizon 150 km

Altitude 12000ft,

horizon 250 km

Example of ESM Trial


Trial Objectives

To Test the De-interleaver using two of the same type of Coastal Surveillance Radar

To check the creation of an intercept for a radar as it comes into the radar horizon

To check that multi-tracking does not occur

To Test DF performance

Aircraft Parameters

Speed = 200 kts, Maximum Altitude = 20000 ft

Straight line route needed = 60 km

Start of Route = 6.1 N 115.5 E End of Route = 6.5 N 116.0 E

ESM Sensitivity

- 60 dBmi

Range to Radars of Interest

Site Name Range at Route Start (km) Range at Route End (km)

Pulau Gaya 60 53

Pulau Mantanani 115 44

Pulau Balambagan 205 134

Altitude = 5000 ft for radar horizon of 160 km


Aircraft Route to Test De-interleaver and Detection Range


-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-4 -3 -2 -1 0 1 2 3 4Azimuth Angle (degrees)

Am

pli

tud

e (

dB

mi)

Range to Radar

= 15nm

3 dB Beamwidth

= 1.5 o

ES Threshold

Sin(x)/x

Beam Shape

1st Sidelobe Level

= -23 dB

The shape of the radar beam determines how many pulses are seen from

the radar each time the radar scans past the ES system

What does the ESM see from each radar?


Simulation of Radar Beam Pattern

The inputs to the calculation are the 3dB beamwidth of the radar and the first sidelobe

level.

A radiation pattern of the general form (sin(u)/u)2 is generated, using the following equation

for u:

u = C p sin ( q )

B

where: B is the 3dB beamwidth in radians

C is a factor dependent on the level of the first sidelobe

For sidelobe levels other than -13.2 dB (which is the default for a sin(u)/u pattern), the

radiation pattern equation must be modified by the factor z to give a pattern with the

required sidelobe levels. The actual equation used is:

Power, Aq = sin √ (u2 - z2) 2

√ (u2 - z2)

The factor C ranges from 0.885 when the first sidelobe level is -13.2 dB to about 1.4

when the first sidelobe level is -40 dB.

The factor z ranges from 0 when the first sidelobe level is -13.2 dB to about 5.4 when

the first sidelobe level is -40 dB.


Simulation of Radar Beam Pattern

The radiation pattern is altered in two ways by the general equation which provides the

power, Aq.

In addition to the suppression of the sidelobes, the main peak is enhanced in power. The

power must be normalised by subtracting the power at the peak of the beam as follows to

reduce the effects of the sidelobe generation to a zero gain:

A = A0 - Aq

where A0 is the calculated power at the peak of the beam, i.e. q = 0.

The final stage in the calculation of the emitter power is the correction for the peak ERP

of the emitter at the particular range.

Finally, the radar scan period and the pulse repetition intervals are needed to find the

power of each pulse as the radar scans past the ESM.


Range Pulses % of Radar

Duration Scan Time

200 nm 50 1.25

150 nm 50 1.25

100 nm 66 1.65

50 nm 150 3.75

25 nm 300 7.50

15 nm 1500 37.50

-70

-60

-50

-40

-30

-20

-10

0 50 100 150 200 250 300 350

Am

pli

tud

e (

dB

)

Time (ms)

50 nm

150 ms

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0 50 100 150 200 250 300 350

Am

pli

tud

e (

dB

)

Time (ms)

25 nm

300 ms

-70

-60

-50

-40

-30

-20

-10

0

0 100 200 300

Am

pli

tud

e (

dB

)

Time (ms)

100 nm

66 ms


Beam Patterns for Different Ranges


Time-line of All radars in trial

0

1

2

3

4

5

6

7

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

Em

itte

r in

Sc

en

ari

o

Time (ms)

Labuan ATC

KK ATC

KK Weather

Palau Balambagan

Palau Mantanani

Palau Gaya


Predicted Amplitude of all radars Showing Pulse Density

in one minute of flight

-60

-55

-50

-45

-40

-35

-30

-25

-20

0 10000 20000 30000 40000 50000 60000

Pu

lse

Am

pli

tud

e (

dB

)

Time (ms)

KK WeatherRadarKK ATC

Labuan ATC

PulauBalambaganPulauMantananiPulau Gaya

(~ 4000 pulses from 6 radars)


Detail of Predicted Amplitude Profiles

-60

-55

-50

-45

-40

-35

-30

-25

-20

35000 36000 37000 38000 39000 40000

Pu

lse

Am

pli

tud

e (

dB

)

Time (ms)


Labuan ATC



Fine Detail of Predicted Amplitude Profiles

-60

-55

-50

-45

-40

-35

-30

-25

-20

37300 37400 37500 37600 37700 37800 37900 38000

Pu

lse

Am

pli

tud

e (

dB

)

Time (ms)


Labuan ATC



Analysis of Trials Data

Graphical Representation of Pulse Data

Visualisation / Playback of Operator’s Screen

Calculation and Plot of Correct DOA Profiles

Graphical representation of “Track” Data

Comparison of Pulse Data with Simulation


Visualisation of the Operator’s Screen


DOA and Range Profiles of Radars of Interest

0

30

60

90

120

150

180

210

0 100 200 300 400 500 600

DO

A (

de

gre

es

) Pulau Gaya

PulauMantanani

PulauBalambagan

0

40

80

120

160

200

0 100 200 300 400 500 600

Ran

ge

(km

)

Time (seconds)


The analysis of ESM Track Data


0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600

DO

A (

de

gre

es

)

Time (seconds)

Pulau Gaya

Pulau Mantanani

Pulau Balambagan

53km

60km

115 km

205 km134 km

44 km

To see the DOA performance of the ESM the correct DOA of the radar is plotted (found by using

navigation data from the trials platform) and the DOA of Track Updates created by the ESM are

shown on the same graph.


The analysis of ESM Track Data


50

51

52

53

54

55

56

57

58

59

60

300 310 320 330 340 350 360 370 380 390 400

DO

A (

de

gre

es

)

Time (seconds)

This graph shows the tracks created for two of the radars, with the track for Palau Balambagan

appearing as the radar comes into the radar horizon of the aircraft.

Palau Balambagan

Palau Mantanani


The analysis of ESM Pulse Data


Each of the updates to the ESM tracks is created from sets of pulses. In this plot the correct

DOA of the radar is plotted and the DOAs of individual pulses are plotted on the same graph.

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600

DO

A (

de

gre

es

)

Time (seconds)

Pulau Mantanani

Pulau Balambagan

Pulau Gaya

Pulau Gaya

Pulau Mantanani

Pulau Balambagan

53km

60km

115 km

205 km

134 km

44 km


The Detail of the Pulse Data


In this graph the pulses from individual scans of each of the 3 radars can be seen.

40

60

80

100

120

140

160

370 375 380 385 390 395 400

DO

A (

de

gre

es

)

Time (seconds)

Pulau Mantanani

Pulau Balambagan

Pulau Gaya

Pulau Gaya

Pulau Mantanani

Pulau Balambagan

53km60km

115 km

205 km 134 km

44 km


Comparison of Theoretical Beam Shape with Received Pulses

Theoretical Amplitude

Profile

Example of Amplitude

Profile from Pulse Data

-65

-60

-55

-50

-45

-40

-35

-30

0 5 10 15 20 25

Am

pli

tud

e (

dB

mi)

Time (ms)

Number of Pulses = 24

Range to Radar = 60 km

-65

-60

-55

-50

-45

-40

-35

-30

0 5 10 15 20 25

Am

pli

tud

e (

dB

mi)

Time (ms)




Comparison of Theoretical Beam Shape with Received Pulses

Theoretical Amplitude

Profile

Example of Amplitude

Profile from Pulse Data-56

-54

-52

-50

-48

-46

-44

-42

-40

0 2 4 6 8 10

Am

pli

tud

e (

dB

mi)

Time (ms)



-56

-54

-52

-50

-48

-46

-44

-42

-40

0 2 4 6 8 10

Am

pli

tud

e (

dB

mi)

Time (ms)



radar2

3

1

4

5


Route taken by aircraft in trial

Example of Use of Pulse Data to diagnose DF / Multi-tracking

4

radar

1

3

5

2


Track formation during the Trial


Pulse data during a single run of the flight trial


Single scans of an ATC Radar showing the slope in DOA

across the main beam


ESM Antenna Installation on a Large Aircraft similar to the antenna

configuration in the trial where the DOA spread was first seen

Amplitude Comparison DOA Measurement


The beam shape for the ESM antennas can be represented by a Gaussian model with a nominal 3dB beamwidth of

about 70o.

The amplitude difference between the mth and either the (m+1)th port or the (m-1)th port can be used to estimate the

direction of arrival of the signal.

The assumption in the operation of an Amplitude Comparison ESM system is that the emitted pulse arrives with

equal amplitude at all receiving antennas, but that the detected amplitude at each antenna depends on the

receiver antenna beam shape.

The DOA of the pulse can therefore be determined from the difference in amplitude of the receiving antennas.

Typical ESM Receiver Antenna

Beam Shapes

with Activation Levels for a

Correct DOA of 70o


Typical Beam Shape of an Air Traffic Control (ATC) Radar


Typical Beam Shape of an ATC Radar with

overlay of Aircraft Azimuth Extent


DOA Errors across the main beam of a scanning radar as an aircraft with

30m ESM antenna separation moves past the radar at a range of 10 nm


Theoretical DOA Error Slope due to Antenna Separation

-65

-60

-55

-50

-45

-40

-35

-30

0 5 10 15 20 25 30

Am

pli

tud

e (

dB

mi)

-20

-10

0

10

20

0 5 10 15 20 25 30

DO

A E

rro

r (

deg

ree

s)

Time (ms)


Using Trials Data for ELINT Databases

Traditionally an Emitter Type would have been specified in the Emitter Libraries

for ESM Systems, rather having specific parameters for individual Emitter sites.

For example,

A typical Air Traffic Control (ATC)Radar may have the following parameter ranges

specified for it in the Emitter Library:

RF = 2700 to 3100 MHz, PRI = 1000 to 2000 ms, PW = 1 to 2 ms

A typical Marine Radar may have the following parameter ranges:

RF = 3040 to 3065 MHz, PRI = 1200 to 1300 ms, PW = 0.7 to 1.2 ms

Already we can see ambiguity.....


Example of the Overlap in Parameter ranges for some

ATC/Marine radars

0

500

1000

1500

2000

2500

0 500 1000 1500 2000 2500 3000

pu

lse

wid

th (

ns

) .

PRI (ms)



Using Trials Data for ELINT Databases

There is a trend towards using specific emitter parameters in Emitter

Libraries.

For example, two ATC radars of the same type would be specified

individually in the library

Radar at site A: RF = 2765 MHz, PRI = 1333ms, PW = 1.2ms

Radar at Site B: RF = 2945 MHz, PRI = 1555ms, PW = 1.5ms

Pulse data is needed to aid the specification and testing of the Emitter

Library.

.


Interleaved Radar Pulses

Here is an example of what pulses received from typical set of ship radars in

250 ms may look like – even in a busy RF environment it is rare to get more

than 3 or 4 radar pulse streams interleaved at any one time.

-70

-60

-50

-40

-30

-20

0 50 100 150 200 250

Pu

lse

Am

pli

tud

e (

dB

mi)

Time (ms)


De-interleaved Radar Pulses

It is therefore straightforward to de-interleave the radar pulses off-line from

the trial and extract sets of pulses for individual radars for use in the ELINT

database.

-70

-60

-50

-40

-30

-20

0 50 100 150 200 250

Pu

lse

Am

pli

tud

e (

dB

mi)

Time (ms)


Example of Pulses received from a Fixed PRI radar

and corresponding ELINT data set

-70

-60

-50

-40

-30

-20

0 50 100 150 200 250

Time (ms)

Radar Pulses

Pulse Amp1 TOA2 PRI3 RF4 PW5

(dBmi) (ms) (ms) (MHz) (ms)

1 -54.7 101.65 3045.1 0.70

2 -52.5 102.98 1331.831 3045.1 0.70

3 -48.5 104.32 1331.831 3045.2 0.71

4 -48.5 105.65 1331.830 3045.0 0.71

5 -47.0 106.98 1331.832 3045.2 0.70

6 -46.2 108.31 1331.831 3045.2 0.70

7 -47.0 109.64 1331.831 3045.1 0.70

8 -48.5 110.98 1331.831 3045.3 0.70

9 -49.5 112.31 1331.832 3045.2 0.70

10 -52.5 113.64 1331.831 3045.3 0.71

11 -54.0 114.97 1331.834 3045.2 0.70

12 -57.0 116.30 1331.833 3045.2 0.70

13 -59.5 117.63 1331.833 3045.2 0.72

Specific EmitterParameters

RF = 3045 MHz PRI Type = Fixed

PW = 0.7 (ms) PRI Element = 1331.83 (ms)

Scan Period = 1.8 seconds 3dB beamwidth = 2 degrees

1 Amplitude

2 Time of Arrival

3 Pulse Repetition Interval

4 Radar Frequency

5 Pulse Width


Example of Pulses received from a Staggered PRI

radar and corresponding ELINT data set

-70

-60

-50

-40

-30

-20

0 50 100 150 200 250

Time (ms)

Radar Pulses

Pulse Amp1 TOA2 PRI3 RF4 PW5

(dBmi) (ms) (ms) (MHz) (ms)

1 -59.0 215.20 9410.1 0.30

2 -55.7 216.87 1673.232 9410.0 0.31

3 -53.7 218.56 1685.516 9410.2 0.30

4 -51.7 220.26 1697.217 9410.1 0.30

5 -49.5 221.93 1673.232 9410.1 0.30

6 -47.0 223.61 1685.516 9410.2 0.30

7 -46.7 225.31 1697.217 9410.2 0.31

8 -45.5 226.99 1673.233 9410.1 0.30

9 -44.7 228.67 1685.516 9410.1 0.30

10 -44.7 230.37 1697.217 9410.0 0.30

11 -45.5 232.04 1673.232 9410.1 0.30

12 -46.2 233.73 1685.516 9410.0 0.30

13 -47.0 235.42 1697.217 9410.1 0.30

14 -51.7 237.10 1673.232 9410.0 0.31

15 -54.0 238.78 1685.517 9410.2 0.30

Specific Emitter Parameters

RF = 9410 MHz PRI Type = Staggered

PW = 0.3 (ms) PRI Elements =1673.232, 1685.516, 1697.217(ms)

Scan Period = 1.5 seconds 3dB beamwidth = 1.8 degrees

1 Amplitude

2 Time of Arrival

3 Pulse Repetition Interval

4 Radar Frequency

5 Pulse Width


Conclusions

O T & E trials are needed to check aspects of ESM System performance, such as

de-interleaving, detection range and DF accuracy in the real world.

Use of simulation of radar beam shapes based on actual ground truth allows a

comparison to be made with data recorded during a trial.

Issues such as multi-tracking and DOA errors can be diagnosed by looking at

recorded pulse data.

Recorded radar pulse data can be used to populate ELINT databases and for the

creation of ESM radar libraries containing specific Emitter Identities.


Dr Sue Robertson, e-mail: [email protected]

Nimrod MRA4

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